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Sökning: WFRF:(Brismar Torkel B.)

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1.
  • Heil, Jan, et al. (författare)
  • Sarcopenia predicts reduced liver growth and reduced resectability in patients undergoing portal vein embolization before liver resection-A DRAGON collaborative analysis of 306 patients
  • 2022
  • Ingår i: HPB. - : ELSEVIER SCI LTD. - 1365-182X .- 1477-2574. ; 24:3, s. 413-421
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: After portal vein embolization (PVE) 30% fail to achieve liver resection. Malnutrition is a modifiable risk factor and can be assessed by radiological indices. This study investigates, if sarcopenia affects resectability and kinetic growth rate (KGR) after PVE. Methods: A retrospective study was performed of the outcome of PVE at 8 centres of the DRAGON collaborative from 2010 to 2019. All malignant tumour types were included. Sarcopenia was defined using gender, body mass and skeletal muscle index. First imaging after PVE was used for liver volumetry. Primary and secondary endpoints were resectability and KGR. Risk factors impacting liver growth were assessed in a multivariable analysis. Results: Eight centres identified 368 patients undergoing PVE. 62 patients (17%) had to be excluded due to unavailability of data. Among the 306 included patients, 112 (37%) were non-sarcopenic and 194 (63%) were sarcopenic. Sarcopenic patients had a 21% lower resectability rate (87% vs. 66%, p < 0.001) and a 23% reduced KGR (p = 0.02) after PVE. In a multivariable model dichotomized for KGR >2.3% standardized FLR (sFLR)/week, only sarcopenia and sFLR before embolization correlated with KGR. Conclusion: In this largest study of risk factors, sarcopenia was associated with reduced resectability and KGR in patients undergoing PVE.
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2.
  • Al-Amiry, Bariq, 1976-, et al. (författare)
  • Does body mass index affect restoration of femoral offset, leg length and cup positioning after total hip arthroplasty? : a prospective cohort study
  • 2019
  • Ingår i: BMC Musculoskeletal Disorders. - : BioMed Central (BMC). - 1471-2474. ; 20
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: In obese patients, total hip arthroplasty (THA) can be technically demanding with increased perioperative risks. The aim of this prospective cohort study is to evaluate the effect of body mass index (BMI) on radiological restoration of femoral offset (FO) and leg length as well as acetabular cup positioning.Methods: In this prospective study, patients with unilateral primary osteoarthritis (OA) treated with THA between September 2010 and December 2013 were considered for inclusion. The perioperative plain radiographs were standardised and used to measure the preoperative degree of hip osteoarthritis, postoperative FO, leg length discrepancy (LLD), acetabular component inclination and anteversion.Results: We included 213 patients (74.5% of those considered for inclusion) with a mean BMI of 27.7 (SD 4.5) in the final analysis. The postoperative FO was improper in 55% and the LLD in 15%, while the cup inclination and anteversion were improper in 13 and 23% of patients respectively. A multivariable logistic regression model identified BMI as the only factor that affected LLD. Increased BMI increased the risk of LLD (OR 1.14, 95% CI 1.04 to 1.25). No other factors included in the model affected any of the primary or secondary outcomes.Conclusion: Increased BMI showed a negative effect on restoration of post-THA leg length but not on restoration of FO or positioning of the acetabular cup. Age, gender, OA duration or radiological severity and surgeon’s experience showed no relation to post-THA restoration of FO, leg length or cup positioning.
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3.
  • Al-Amiry, Bariq Sh. 1976-, et al. (författare)
  • The Influence of Radiological Severity and Symptom Duration of Osteoarthritis on Postoperative Outcome After Total Hip Arthroplasty : A Prospective Cohort Study
  • 2018
  • Ingår i: The Journal of Arthroplasty. - : CHURCHILL LIVINGSTONE INC MEDICAL PUBLISHERS. - 0883-5403 .- 1532-8406. ; 33:2, s. 436-440
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: We aimed to investigate the influence of preoperative radiological severity and symptom duration of hip osteoarthritis (OA) on the postoperative functional outcome, quality of life, as well as abductor muscle strength after total hip arthroplasty (THA). Methods: In this prospective cohort study, we studied 250 patients. Preoperatively, we evaluated the function with the Western Ontario and McMaster Universities Osteoarthritis (WOMAC) index and quality of life with euroqol-5D (EQ-5D). At 1 year after THA, the same scores and also hip abductor muscle strength were measured in 222 patients. We divided the cohort twice, first according to the radiological OA severity [Kellgren-Lawrence classification (KL)] and then according to the OA symptom duration. We investigated whether the preoperative KL class and symptom duration influenced the 1-year WOMAC (primary outcome measure) or EQ-5D and abductor muscle strength (secondary outcome measures). Results: The crude results showed that KL class and symptom duration had no influence (P = .90 and P = .20, respectively) on the 1-yearWOMAC. Younger age, male gender, and lower body mass index were associated with a better function. Regarding 1-year EQ-5D, the crude results showed that body mass index and KL class had no influence (P = .83 and P = .39, respectively). The adjusted results showed that only age and gender influenced the postoperative EQ-5D. No influence of the tested factors was found on the 1-year abductor muscle strength. Conclusion: Preoperative radiological OA severity and symptom duration had no influence on the outcome of THA and should probably not affect the decision about timing the operative intervention. 
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4.
  • Barrefelt, Asa, et al. (författare)
  • Fluorescence labeled microbubbles for multimodal imaging
  • 2015
  • Ingår i: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 464:3, s. 737-742
  • Tidskriftsartikel (refereegranskat)abstract
    • Air-filled polyvinyl alcohol microbubbles (PVA-MBs) were recently introduced as a contrast agent for ultrasound imaging. In the present study, we explore the possibility of extending their application in multimodal imaging by labeling them with a near infrared (NIR) fluorophore, VivoTag-680. PVA-MBs were injected intravenously into FVB/N female mice and their dynamic biodistribution over 24 h was determined by 3D-fluorescence imaging co-registered with 3D-mu CT imaging, to verify the anatomic location. To further confirm the biodistribution results from in vivo imaging, organs were removed and examined histologically using bright field and fluorescence microscopy. Fluorescence imaging detected PVA-MB accumulation in the lungs within the first 30 min post-injection. Redistribution to a low extent was observed in liver and kidneys at 4 h, and to a high extent mainly in the liver and spleen at 24 h. Histology confirmed PVA-MB localization in lung capillaries and macrophages. In the liver, they were associated with Kupffer cells; in the spleen, they were located mostly within the marginal-zone. Occasional MBs were observed in the kidney glomeruli and interstitium. The potential application of PVA-MBs as a contrast agent was also studied using ultrasound (US) imaging in subcutaneous and orthotopic pancreatic cancer mouse models, to visualize blood flow within the tumor mass. In conclusion, this study showed that PVA-MBs are useful as a contrast agent for multimodal imaging. (C) 2015 Elsevier Inc. All rights reserved.
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5.
  • Barrefelt, Åsa, et al. (författare)
  • Biodistribution, kinetics, and biological fate of SPION microbubbles in the rat
  • 2013
  • Ingår i: International Journal of Nanomedicine. - 1176-9114 .- 1178-2013. ; 8, s. 3241-3254
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: In the present investigation, we studied the kinetics and biodistribution of a contrast agent consisting of poly(vinyl alcohol) (PVA) microbubbles containing superparamagnetic iron oxide (SPION) trapped between the PVA layers (SPION microbubbles). Methods: The biological fate of SPION microbubbles was determined in Sprague-Dawley rats after intravenous administration. Biodistribution and elimination of the microbubbles were studied in rats using magnetic resonance imaging for a period of 6 weeks. The rats were sacrificed and perfusion-fixated at different time points. The magnetic resonance imaging results obtained were compared with histopathologic findings in different organs. Results: SPION microbubbles could be detected in the liver using magnetic resonance imaging as early as 10 minutes post injection. The maximum signal was detected between 24 hours and one week post injection. Histopathology showed the presence of clustered SPION microbubbles predominantly in the lungs from the first time point investigated (10 minutes). The frequency of microbubbles declined in the pulmonary vasculature and increased in pulmonary, hepatic, and splenic macrophages over time, resulting in a relative shift from the lungs to the spleen and liver. Meanwhile, macrophages showed increasing signs of cytoplasmic iron accumulation, initially in the lungs, then followed by other organs. Conclusion: The present investigation highlights the biological behavior of SPION microbubbles, including organ distribution over time and indications for biodegradation. The present results are essential for developing SPION microbubbles as a potential contrast agent and/or a drug delivery vehicle for specific organs. Such a vehicle will facilitate the use of multimodality imaging techniques, including ultrasound, magnetic resonance imaging, and single positron emission computed tomography, and hence improve diagnostics, therapy, and the ability to monitor the efficacy of treatment.
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6.
  • Barrefelt, Åsa, et al. (författare)
  • DYNAMIC MR IMAGING, BIODISTRIBUTION AND PHARMACOKINETICS OF POLYMER SHELLED MICROBUBBLES CONTAINING SPION
  • 2014
  • Ingår i: NANO. - 1793-2920. ; 9:6, s. 1450069-
  • Tidskriftsartikel (refereegranskat)abstract
    • Magnetic Resonance Imaging (MRI) is a noninvasive diagnostic method that provides information on morphological and physiological changes of the internal organs over time. Imaging and measurements can be repeated on the same subject, thereby reducing inter-individual variability effects and hence the number of subjects required. A potential MRI contrast agent consisting of microbubbles embedded with superparamagnetic iron oxide nanoparticles (SPION) in the shell (SPION MBs) was injected intravenously into rats to determine their biodistribution and pharmacokinetics using MR imaging. Agarose phantoms containing SPION MBs were scanned using 3 T MRI to construct a standard curve. Rats were injected with SPION MBs, free SPION or plain MBs and scanned dynamically at 3 T using a clinical MR scanner. The relaxation rate (R2*) was studied over time as a measure of the iron oxide concentrations to enable calculation of the pharmacokinetic parameters. The kinetics of SPION MBs in the liver was fitted to a one-compartment model. Furthermore, the biological fate of SPION MBs was examined via a histological survey of tissue samples using Perls' Prussian blue staining and immunohistochemistry (IHC). 1.2 h after injection of SPION MBs, T2* of the liver had decreased to its minimum. The elimination half-life of SPION MBs was 598.2 +/- 97.3 h, while the half-life for SPION was 222.6 +/- 26.4 h. Moreover, our study showed that SPION MBs were taken up by the macrophages in the lungs, spleen and liver. MBs labeled with SPION can be used for MR imaging. Moreover, MRI is a reliable and noninvasive tool that can be utilized in pharmacokinetic investigations of future contrast agents using SPION MBs and SPION in the rat.
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7.
  • Brismar, Torkel B (författare)
  • Assessment of skeletal structure by MR relaxometry
  • 1999
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Introduction: More than 40 per cent of all women older than 50 years will suffer from a hip, wrist or vertebral fracture. Most of these fractures are related to bone fragility, osteoporosis. If the disease is diagnosed and treated at an early stage the risk of fracture can be decreased. Traditional methods in clinical use primarily use the absorption of X-ray energy to evaluate bone quality. However, these methods do not evaluate the micro-structure of the bone, which has a major influence on biomechanical strength. This thesis evaluates a method to study the micro structure of trabecular bone by magnetic resonance (MR) relaxometry. Methods: Magnetic inhomogeneity arise at the interface between trabecular bone and bone marrow. The magnetic inhomogeneity results in decreased signal intensity in gradient echo images. The rate of the signal decrease can be used as an indirect measure of the trabecular bone structure called R2* (= 1/T2*). The trabecular bone is embedded in bone marrow containing fat and water. To evaluate the influence of fat and water content on T2* measurements the signal behaviour as a function of TE was studied in porcine lumbar vertebrae and fat emulsions. T2* values were related to biomechanical strength tested experimentally. A new method to study trabecular bone orientation by MR relaxometry was developed. MR relaxometric values of human vertebrae were related to the amount of bone mineral in vitro. The obtained MR relaxometric values of spine, hip and calcaneus were related to values obtained by dual X-ray absorptiometry (DXA) and by quantitative ultrasound QUS). Results: There was a relationship between fat content and T2*. As fat and water have different spin-lattice relaxation times (Tl) TR will theoretically also affect T2* measurements. The sagittal imaging plane is advantageous when performing MR relaxometry of the spine. Under experimental conditions MR relaxometry can predict biomechanical strength. Trabecular bone orientation studied by MR relaxometry in vitro can be calculated by rotation of the studied object in three orientations orthogonal to the external magnetic field. A relationship between results obtained by MR relaxometry and by bone mineral absorptiometry measurements was observed in vitro. Also in vivo MR relaxometry was related to absorptiometry of hip and to QUS of calcaneus. Conclusion: MR relaxometry is an accurate method to evaluate trabecular bone structure in vivo. The technique will be of interest not only for research purposes, but also for diagnosis and for treatment control at various diseases affecting the skeleton.
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8.
  • Brismar, Torkel B., et al. (författare)
  • Magnetite Nanoparticles Can Be Coupled to Microbubbles to Support Multimodal Imaging
  • 2012
  • Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 13:5, s. 1390-1399
  • Tidskriftsartikel (refereegranskat)abstract
    • Microbubbles (MBs) are commonly used as injectable ultrasound contrast agent (UCA) in modern ultrasonography. Polymer-shelled UCAs present additional potentialities with respect to marketed lipid-shelled UCAs. They are more robust; that is, they have longer shelf and circulation life, and surface modifications are quite easily accomplished to obtain enhanced targeting and local drug delivery. The next generation of UCAs will be required to support not only ultrasound-based imaging methods but also other complementary diagnostic approaches such as magnetic resonance imaging or computer tomography. This work addresses the features of MBs that could function as contrast agents for both ultrasound and magnetic resonance imaging. The results indicate that the introduction of iron oxide nanoparticles (SPIONs) in the poly(vinyl alcohol) shell or on the external surface of the MBs does not greatly decrease the echogenicity of the host MBs compared with the unmodified one. The presence of SPIONs provides enough magnetic susceptibility to the MBs to accomplish good detectability both in vitro and in vivo. The distribution of SPIONs on the shell and their aggregation state seem to be key factors for the optimization of the transverse relaxation rate.
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9.
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10.
  • Erlandsson, Helen, et al. (författare)
  • Scoring of medial arterial calcification predicts cardiovascular events and mortality after kidney transplantation
  • 2022
  • Ingår i: Journal of Internal Medicine. - : Wiley. - 0954-6820 .- 1365-2796. ; 291:6, s. 813-823
  • Tidskriftsartikel (refereegranskat)abstract
    • Background Progression of vascular calcification causes cardiovascular disease, which is the most common cause of death in chronic kidney failure and after kidney transplantation (KT). The prognostic impact of the extent of medial vascular calcification at KT is unknown. Methods In this prospective cohort study, we investigated the impact of medial calcification compared to a mix of intimal and medial calcification represented by coronary artery calcification (CAC score) and aortic valve calcification in 342 patients starting on kidney failure replacement therapy. The primary outcomes were cardiovascular events (CVE) and death. The median follow-up time was 6.4 years (interquartile range 3.7-9.6 years). Exposure was CAC score and arteria epigastrica medial calcification scored as none, mild, moderate, or severe by a pathologist at time of KT (n = 200). We divided the patients according to kidney failure replacement therapy during follow-up, that is, living donor KT, deceased donor KT, or dialysis. Results Moderate to severe medial calcification in the arteria epigastrica was associated with higher mortality (p = 0.001), and the hazard ratio for CVE was 3.1 (95% confidence interval [CI] 1.12-9.02, p < 0.05) compared to no or mild medial calcification. The hazard ratio for 10-year mortality in the dialysis group was 33.6 (95% CI, 10.0-113.0, p < 0.001) compared to living donor recipients, independent of Framingham risk score and prevalent CAC. Conclusion Scoring of medial calcification in the arteria epigastrica identified living donor recipients as having 3.1 times higher risk of CVE, independent of traditional risk factors. The medial calcification score could be a reliable method to identify patients with high and low risk of CVE and mortality following KT.
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11.
  • Gardin, Anna, et al. (författare)
  • Dynamic contrast enhanced magnetic resonance imaging in chronic Achilles tendinosis
  • 2013
  • Ingår i: BMC Medical Imaging. - : Springer Science and Business Media LLC. - 1471-2342. ; 13, s. 39-
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Chronic Achilles tendinosis is a common problem. When evaluating and comparing different therapies there is a need for reliable imaging methods. Our aim was to evaluate if chronic Achilles tendinosis affects the dynamic contrast-enhancement in the tendon and its surroundings and if short-term eccentric calf-muscle training normalizes the dynamic contrast-enhancement. Methods: 20 patients with chronic Achilles tendinopathy were included. Median duration of symptoms was 31 months (range 6 to 120 months). Both Achilles tendons were examined with dynamic contrast enhanced MRI before and after a 12-week exercise programme of eccentric calf-muscle training. The dynamic MRI was evaluated in tendon, vessel and in fat ventrally of tendon. Area under the curve (AUC), time to peak of signal, signal increase per second (SI/s) and increase in signal between start and peak as a percentage (SI%) was calculated. Pain and performance were evaluated using a questionnaire. Results: In the fat ventrally of the tendon, dynamic contrast enhancement was significantly higher in the symptomatic leg compared to the contralateral non-symptomatic leg before but not after treatment. Despite decreased pain and improved performance there was no significant change of dynamic contrast enhancement in symptomatic tendons after treatment. Conclusion: In Achilles tendinosis there is an increased contrast enhancement in the fat ventrally of the tendon. The lack of correlation with symptoms and the lack of significant changes in tendon contrast enhancement parameters do however indicate that dynamic enhanced MRI is currently not a useful method to evaluate chronic Achilles tendinosis.
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12.
  • Golembiewska, Edyta, et al. (författare)
  • Copeptin is independently associated with vascular calcification in chronic kidney disease stage 5
  • 2020
  • Ingår i: BMC Nephrology. - Stockholm : Karolinska Institutet, Dept of Clinical Science, Intervention and Technology. - 1471-2369.
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Vascular calcification (VC) is an independent predictor of cardiovascular disease (CVD) present in 30– 70% of patients with chronic kidney disease (CKD). Copeptin is a sensitive surrogate marker of arginine vasopressin (AVP), which is involved in many pathophysiologic processes in CKD. The aim of the present study was to explore the association of copeptin with VC in CKD stage 5. Methods: Copeptin was investigated in conjunction with living donor kidney transplantation in 149 clinically stable CKD stage 5 patients (CKD5), including 53 non-dialyzed (CKD5-ND) and 96 dialysis patients treated by peritoneal dialysis (PD) (n = 43) or hemodialysis (HD) (n = 53). We analyzed the association of copeptin with presence and extent of VC ascertained both histologically in biopsies from the inferior epigastric artery (n = 137) and by coronary artery calcification (CAC) score measured by computed tomography. Results: Patients with higher copeptin were older, had higher systolic blood pressure, higher prevalence of CVD and their preceding time on chronic dialysis was longer. In Spearman’s rank correlations (Rho), copeptin concentrations were significantly associated with CAC score (Rho = 0.27; p = 0.003) and presence of medial VC (Rho = 0.21; p = 0.016). Multivariate logistic regression analysis showed that 1-SD higher age, male gender, diabetes and 1-SD higher copeptin were significantly associated with the presence of moderate-extensive VC. Conclusions: High circulating levels of copeptin in CKD5 patients are independently associated with the degree of medial calcification ascertained by histology of arterial biopsies. Thus, plasma copeptin may serve as a marker of the uremic calcification process.
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13.
  • Grishenkov, Dmitry, 1983-, et al. (författare)
  • Acoustic properties of polymer-shelled ultrasound contrast agents. Bulk volume vs. microcapillary
  • 2009
  • Ingår i: 16th International Congress on Sound and Vibration 2009, ICSV 2009. - Krakow. - 9781615677368 ; , s. 2515-2522
  • Konferensbidrag (refereegranskat)abstract
    • The focus of contrast-enhanced ultrasound research has developed beyond detecting the blood pool to new areas such as perfusion imaging, drug and gene therapy, and targeted imaging. Polymer-shelled microbubbles are proposed as a new generation of ultrasound contrast agents (UCAs) which fulfil the requirements of these applications. With a shelf-life of several months and possibility to conjugate pharmacological molecules to their surface, these UCAs will allow not only to enhance the contrast of ultrasound images, but also to function as carriers of drugs to be delivered locally. In this study, the results of an experimental investigation of three types of UCAs stabilized by thick poly vinyl alcohol (PVA) shell are presented. These UCAs are synthesized from a PVA aqueous solution under varied pH values and temperature. The UCAs differ from each other in their average diameter, shell thickness and polydispersity. Knowledge of the peak negative pressure at which the solid shell fractures is paramount for a proper use of UCAs. Therefore, the dependence of this quantity on temperature and number of cycles in the incident pulse is examined. Much of the blood volume resides in the microcirculation, with capillaries playing a particularly important role in patho-physiology and drug delivery. In this sense in vitro characterization of the UCAs oscillation was moved from bulk volume to the capillary scale, where tissue-bubble interaction takes place. The main conclusion to be drawn from these results is that the shell of the UCAs begin to fracture at values of mechanical index (MI) approved for clinical applications. The fatigue, i.e. the accumulation of damage within the shell of the UCAs, is found to play an important role in fracturing the shell. Finally adhesion of the UCAs to the elastic wall is studied and correlated with estimates of the shell’s visco-elastic constants. Open questions arising from this comparison are briefly discussed.
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14.
  • Grishenkov, Dmitry, 1983-, et al. (författare)
  • Characterization of Acoustic Properties of PVA-Shelled Ultrasound Contrast Agents
  • 2010
  • Ingår i: Ultrasound Contrast Agents. - Italia : Springer-Verlag. - 9788847014930 ; , s. 99-108
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
    • This work examines the acoustic behavior of ultrasound contrast agents made of poly (vinyl alcohol) (PVA) shelled microbubbles manufactured at three different pH and temperature conditions. Backscattering amplitude, attenuation coefficient and phase velocity of ultrasonic waves propagating through suspensions of PVA contrast agents were measured at temperature values ranging between 24 oC and 37 oC in a frequency range from 3 MHz to 13 MHz.  A significant enhancement of the backscattering amplitude and displaying a weak dependence on temperature were observed.  Attenuation and phase velocity, on the other hand, showed higher sensitivity to temperature variations.  The dependence on system parameters such as the number of cycles, frequency, and exposure of the peak negative pressure, Pthr, at which ultrasound contrast agents fracture was also investigated.  The effects of temperature, blood, and, wherever data are available, of the dimension of the microbubbles on Pthr are also considered.  The large shell thickness notwithstanding, the results of this investigation show that at room temperature PVA contrast agents fracture at negative peak pressure values within the recommended safety limit.  Furthermore, Pthr decreases with increasing temperature, radius of the microbubbles, and number of cycles of the incident wave.  In conclusion, these results suggest that PVA-shelled microbubbles may offer a potentially viable system to be employed for both imaging and therapeutic purposes.
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15.
  • Grishenkov, Dmitry, 1983-, et al. (författare)
  • Characterization of acoustic properties of PVA-shelled ultrasound contrast agents : linear properties (Part I)
  • 2009
  • Ingår i: Ultrasound in Medicine and Biology. - : Elsevier BV. - 0301-5629 .- 1879-291X. ; 35:7, s. 1127-1138
  • Tidskriftsartikel (refereegranskat)abstract
    • This work examines the linear acoustic behavior of ultrasound contrast agents made of three types of poly (vinyl alcohol) (PVA) shelled microbubbles manufactured at different pH and temperature conditions. Back-scattered power, attenuation coefficient and phase velocity of ultrasonic waves propagating through suspensions of PVA contrast agents were measured at temperature values ranging between 24 degrees C and 37 degrees C in a frequency range from 3 MHz to 13 MHz. Enhancement of the backscattered power higher than 20 dB and displaying a weak dependence on temperature was observed. Attenuation and phase velocity, on the other hand, showed higher sensitivity to temperature variations. A modified version of the Church model, which accounts for the dispersion of the dynamic modulus of the PVA shells, was developed to simultaneously fit the attenuation and phase velocity data at 24 degrees C. The frequency dependence of the storage modulus was found to be that of semiflexible polymeric networks. On the other hand, the frequency dependence of the dynamic loss modulus suggests that additional mechanisms, which may be related to the finite dimensions of the shell and/or to its inhomogeneity, may play a significant role in the dissipation of the acoustic energy. For the microbubbles of interest, this model predicts frequency dependent resonance frequency higher than 100 MHz.
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16.
  • Grishenkov, Dmitry, 1983-, et al. (författare)
  • Characterization of acoustic properties of PVA-shelled ultrasound contrast agents : ultrasound-induced fracture (Part II)
  • 2009
  • Ingår i: Ultrasound in Medicine and Biology. - : Elsevier BV. - 0301-5629 .- 1879-291X. ; 35:7, s. 1139-1147
  • Tidskriftsartikel (refereegranskat)abstract
    • Knowledge of the magnitude of the peak negative pressure, P-thr, at which ultrasound contrast agents fracture is relevant for using these microbubbles both as devices for contrast enhancement purposes, as well as carriers of drugs to be delivered locally. In the second part of this communication, the acoustic properties of three types of microbubbles stabilized by poly (vinyl alcohol) (PVA) shells are further investigated. In particular, the dependence of P-thr on system parameters such as the number of cycles, frequency and exposure is examined. The effects of temperature, blood and, wherever data are available, of the dimension of the microbubbles on P-thr are also considered. The large shelf thickness notwithstanding, the results of this investigation show that at room temperature, PVA contrast agents fracture at negative peak pressure values within the recommended safety limit. Furthermore, P-thr decreases with increasing temperature, radius of the microbubbles and number of cycles of the incident wave. Fatigue seems to be a physical mechanism playing a dominant role in the fracture process. The effect of blood on P-thr varies according to condition under which the microbubbles have been synthesized, although stiffening of the shell is observed in most cases. In conclusion, these results suggest that PVA-shelled microbubbles may offer a potentially viable system to be employed for both imaging and therapeutic purposes.
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17.
  • Grishenkov, Dmitry, 1983-, et al. (författare)
  • In vitro contrast-enhanced ultrasound measurements of capillary microcirculation : Comparison between polymer- and phospholipid-shelled microbubbles
  • 2011
  • Ingår i: Ultrasonics. - : Elsevier BV. - 0041-624X .- 1874-9968. ; 51:1, s. 40-48
  • Tidskriftsartikel (refereegranskat)abstract
    • The focus of contrast-enhanced ultrasound research has developed beyond visualizing the blood pool and its flow to new areas such as perfusion imaging, drug and gene therapy, and targeted imaging. In this work comparison between the application of polymer- and phospholipid-shelled ultrasound contrast agents (UCAs) for characterization of the capillary microcirculation is reported. All experiments are carried out using a microtube as a vessel phantom. The first set of experiments evaluates the optimal concentration level where backscattered signal from microbubbles depends on concentration linearly. For the polymer-shelled UCAs the optimal concentration level is reached at a value of about 2 x 10(4) MB/ml, whereas for the phospholipid-shelled UCAs the optimal level is found at about 1 x 10(5) MB/ml.Despite the fact that the polymer shell occupies 30% of the radius of microbubble, compared to 0.2% of the phospholipid-shelled bubble, approximately 5-fold lower concentration of the polymer UCA is needed for investigation compared to phospholipid-shelled analogues. In the second set of experiments, destruction/replenishment method with varied time intervals ranging from 2 ms to 3 s between destructive and monitoring pulses is employed. The dependence of the peak-to-peak amplitude of backscattered wave versus pulse interval is fitted with an exponential function of the time gamma = A( 1 - exp(-beta t)) where A represents capillary volume and the time constant beta represents velocity of the flow. Taking into account that backscattered signal is linearly proportional to the microbubble concentration, for both types of the UCAs it is observed that capillary volume is linearly proportional to the concentration of the microbubbles, but the estimation of the flow velocity is not affected by the change of the concentration. Using the single capillary model, for the phospholipid-shelled UCA a delay of about 0.2-0.3 s in evaluation of the perfusion characteristics is found while polymer-shelled UCA provide response immediately. The latter at the concentration lower than 3.6 x 10(5) MB/ml have no statistically significant delay (p < 0.01), do not cause any attenuation of the backscattered signal or saturation of the receiving part of the system. In conclusion, these results suggest that the novel polymer-shelled microbubbles have a potential to be used for perfusion evaluation.
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18.
  • Grishenkov, Dmitry, 1983-, et al. (författare)
  • On comparison between polymer- and phospholipid-shelled microbubbles for contrast-enhanced ultrasound measurements of capillary microcirculation.
  • 2011
  • Ingår i: Proceedings of the 34<sup>th</sup> Scandinavian Symposium on Physical Acoustics.
  • Konferensbidrag (refereegranskat)abstract
    • The focus of contrast-enhanced ultrasound research has developed beyond visualizing the blood circulation to new areas such as perfusion and molecular imaging, drug and gene therapy. This work compares the application of polymer- and phospholipid-shelled ultrasound contrast agents (UCAs) employed for characterization of the capillary microcirculation. To quantify microcirculation destruction/replenishment technique with varied time intervals between destructive and monitoring pulses is used. The dependence of the peak-to-peak amplitude of backscattered wave versus pulse interval is fitted with an exponential function of the time y=A(1-exp(-βt)) , where A represents capillary volume and the time constant β represents velocity of the flow. Working under assumption that backscattered signal is linearly proportional to the microbubble concentration, for both types of the UCAs it is observed that capillary volume, A, is in linearly relationship with the concentration, and the flow velocity, β, remain unchanged. Using 500 µm diameter microtube as a vessel phantom a delay of about 0.25 s in evaluation of the perfusion characteristics is found for the phospholipid-shelled UCA, while polymer-shelled UCA provide response immediately. In conclusion, these results suggest that the novel polymer-shelled microbubbles have a potential to be used for perfusion evaluation.
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19.
  • Grishenkov, Dmitry, 1983-, et al. (författare)
  • On the acoustic properties of polymer-shell ultrasonic contrast agents.
  • 2008
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Polymer-shelled microbubbles have become the focus of intense research for their enhanced shelf life and demonstrated chemical versatility.  These are properties highly sought after in the ultrasonic contrast agents (UCAs) of the next generation, which will be engineered not only to enhance the contrast of ultrasound-based images, but also to function as carriers of drugs to be delivered locally.  Here, the results of an experimental investigation of three potentially new UCAs are presented.  These microbubbles are stabilized by thick poly (vinyl alcohol) shells.  These UCAs differ from each other in their dimensions and shell thickness (order of 0.5 microns).  Fundamental to their use as drug carrier is the knowledge of the pressure threshold at which the shell of these UCAs fractures.  Therefore, the dependence of this quantity on temperature, number of cycles of the incident pulse, nominal central frequency and pulse repetition frequency of the emitting transducer is examined.  The effect of using blood instead of deionized water is also considered.  The main conclusion to be drawn from these results is that their thick shell notwithstanding, these microbubbles begin to fracture at values of MI which can be acceptable in clinical applications.  This claim is supported also by images acquired by means of commercially available imaging systems.  Finally, these values of the pressure threshold are correlated with estimates of the shells’ visco-elastic constants obtained by fitting Church’s model to the frequency-dependent attenuation coefficient and phase velocity.  Open questions arising from this comparison are briefly discussed.
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20.
  • Gärdin, Anna, et al. (författare)
  • T2 * relaxation time in Achilles tendinosis and controls and its correlation with clinical score
  • 2016
  • Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1053-1807 .- 1522-2586. ; 43:6, s. 1417-1422
  • Tidskriftsartikel (refereegranskat)abstract
    • PURPOSE: To investigate if the T2 * of Achilles tendons can discriminate between chronic Achilles tendinosis and healthy controls; to correlate with clinical score; to evaluate its short-term repeatability; and to estimate minimal detectable change.MATERIALS AND METHODS: Twenty patients, with chronic mid-portion Achilles tendinosis, and 10 controls without history of Achilles tendon symptoms, were examined with a 3T MR scanner with a 3D flash ultrashort time to echo sequence with five different echo times. The sequence was run twice to test repeatability. The tendon border was delineated on axial slices at three different levels in the calculated T2 * maps. The clinical severity of Achilles tendinosis was measured by a VISA-A questionnaire.RESULTS: There was a significant difference in mean T2 * between symptomatic and control tendons (P < 0.001). In patients with unilateral symptoms no significant difference in T2 * was found between symptomatic and contralateral asymptomatic tendons (P = 0.19). There was no significant correlation between clinical severity and T2 * (r = -0.28, P = 0.22). The short-term repeatability of T2 * showed a coefficient of variation of 18%, a least significant change of 50%, and the intraclass correlation coefficient had an average consistency of 0.99.CONCLUSION: T2 * may help to differentiate between chronic Achilles tendinosis and healthy controls but was not associated with the clinical score. However, and notably, the reproducibility of the method was low and the number of patients was small.
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21.
  • Jakola, Asgeir Store, et al. (författare)
  • Quantitative texture analysis in the prediction of IDH status in low-grade gliomas.
  • 2018
  • Ingår i: Clinical neurology and neurosurgery. - : Elsevier BV. - 1872-6968 .- 0303-8467. ; 164, s. 114-120
  • Tidskriftsartikel (refereegranskat)abstract
    • Molecular markers provide valuable information about treatment response and prognosis in patients with low-grade gliomas (LGG). In order to make this important information available prior to surgery the aim of this study was to explore if molecular status in LGG can be discriminated by preoperative magnetic resonance imaging (MRI).All patients with histopathologically confirmed LGG with available molecular status who had undergone a preoperative standard clinical MRI protocol using a 3T Siemens Skyra scanner during 2008-2015 were retrospectively identified. Based on Haralick texture parameters and the segmented LGG FLAIR volume we explored if it was possible to predict molecular status.In total 25 patients (nine women, average age 44) fulfilled the inclusion parameters. The textural parameter homogeneity could discriminate between LGG patients with IDH mutation (0.12, IQR 0.10-0.15) and IDH wild type (0.07, IQR 0.06-0.09, p=0.005). None of the other four analyzed texture parameters (energy, entropy, correlation and inertia) were associated with molecular status. Using ROC curves, the area under curve for predicting IDH mutation was 0.905 for homogeneity, 0.840 for tumor volume and 0.940 for the combined parameters of tumor volume and homogeneity. We could not predict molecular status using the four other chosen texture parameters (energy, entropy, correlation and inertia). Further, we could not separate LGG with IDH mutation with or without 1p19q codeletion.In this preliminary study using Haralick texture parameters based on preoperative clinical FLAIR sequence, the homogeneity parameter could separate IDH mutated LGG from IDH wild type LGG. Combined with tumor volume, these diagnostic properties seem promising.
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22.
  • Klintström, Eva, et al. (författare)
  • Direct estimation of human trabecular bone stiffness using cone beam computed tomography
  • 2018
  • Ingår i: Oral surgery, oral medicine, oral pathology and oral radiology. - : ELSEVIER SCIENCE INC. - 2212-4403 .- 2212-4411. ; 126:1, s. 72-82
  • Tidskriftsartikel (refereegranskat)abstract
    • Objectives. The aim of this study was to evaluate the possibility of estimating the biomechanical properties of trabecular bone through finite element simulations by using dental cone beam computed tomography data. Study Design. Fourteen human radius specimens were scanned in 3 cone beam computed tomography devices: 3-D Accuitomo 80 (J. Morita MFG., Kyoto, Japan), NewTom 5 G (QR Verona, Verona, Italy), and Verity (Planmed, Helsinki, Finland). The imaging data were segmented by using 2 different methods. Stiffness (Young modulus), shear moduli, and the size and shape of the stiffness tensor were studied. Corresponding evaluations by using micro-CT were regarded as the reference standard. Results. The 3-D Accuitomo 80 (J. Morita MFG., Kyoto, Japan) showed good performance in estimating stiffness and shear moduli but was sensitive to the choice of segmentation method. Newtom 5 G (QR Verona, Verona, Italy) and Verity (Planmed, Helsinki, Finland) yielded good correlations, but they were not as strong as Accuitomo 80 U. Morita MFG., Kyoto, Japan). The cone beam computed tomography devices overestimated both stiffness and shear compared with the micro-CT estimations. Conclusions. Finite element-based calculations of biomechanics from cone beam computed tomography data are feasible, with strong correlations for the Accuitomo 80 scanner a. Morita MFG., Kyoto, Japan) combined with an appropriate segmentation method. Such measurements might be useful for predicting implant survival by in vivo estimations of bone properties.
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23.
  • Klintström, Eva, et al. (författare)
  • Predicting Trabecular Bone Stiffness from Clinical Cone-Beam CT and HR-pQCT Data; an In Vitro Study Using Finite Element Analysis
  • 2016
  • Ingår i: PLOS ONE. - : PLOS one. - 1932-6203. ; 11:8
  • Tidskriftsartikel (refereegranskat)abstract
    • Stiffness and shear moduli of human trabecular bone may be analyzed in vivo by finite element (FE) analysis from image data obtained by clinical imaging equipment such as high resolution peripheral quantitative computed tomography (HR-pQCT). In clinical practice today, this is done in the peripheral skeleton like the wrist and heel. In this cadaveric bone study, fourteen bone specimens from the wrist were imaged by two dental cone beam computed tomography (CBCT) devices and one HR-pQCT device as well as by dual energy X-ray absorptiometry (DXA). Histomorphometric measurements from micro-CT data were used as gold standard. The image processing was done with an in-house developed code based on the automated region growing (ARG) algorithm. Evaluation of how well stiffness (Young's modulus E3) and minimum shear modulus from the 12, 13, or 23 could be predicted from the CBCT and HR-pQCT imaging data was studied and compared to FE analysis from the micro-CT imaging data. Strong correlations were found between the clinical machines and micro-CT regarding trabecular bone structure parameters, such as bone volume over total volume, trabecular thickness, trabecular number and trabecular nodes (varying from 0.79 to 0.96). The two CBCT devices as well as the HR-pQCT showed the ability to predict stiffness and shear, with adjusted R-2-values between 0.78 and 0.92, based on data derived through our in-house developed code based on the ARG algorithm. These findings indicate that clinically used CBCT may be a feasible method for clinical studies of bone structure and mechanical properties in future osteoporosis research.
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24.
  • Kälvesten, Johan, et al. (författare)
  • Potential sources of quantification error when retrospectively assessing metacarpal bone loss from historical radiographs by using digital X-ray radiogrammetry : an experimental study
  • 2014
  • Ingår i: Journal of clinical densitometry. - : Elsevier. - 1094-6950 .- 1559-0747. ; 17:1, s. 104-108
  • Tidskriftsartikel (refereegranskat)abstract
    • During the past 15 yr, digital X-ray radiogrammetry (DXR) has been used to measure metacarpal bone mineral density (BMD). BMD is often measured in existing cohorts where X-ray images were not acquired in accordance with the DXR imaging protocol (DIP). The purpose of the present study was to analyze how deviations from DIP in historical radiographs may affect the reproducibility of DXR-BMD measurements. Cadaver hand phantoms were used to conduct repeat measurements of deviations from DIP with respect to voltage, exposure, lateral displacement, supination, combination of lateral displacement and supination or rotation, extension of the wrist, and edge enhancement. Direct digital radiography (Aristos; Siemens Healthcare, Erlangen, Germany) was used for image acquisition and dxr-online (Sectra, Linkoping, Sweden) for DXR-BMD measurements. The influence of the tested deviations from DIP ranged from 0 to 32.5 mg/cm(2) (0-6.8%). On repetition with the same specimen, none of the deviations resulted in a within-specimen reproducibility error greater than 2 mg/cm(2) (0.4%, equivalent to a T-score of 0.042). Among the tested deviations, all except tube voltage had a magnitude greater than the normal measurement noise for the technique and must therefore be considered when planning a study based on historical images.
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25.
  • Laucyte-Cibulskiene, Agne, et al. (författare)
  • Role of GDF-15, YKL-40 and MMP 9 in patients with end-stage kidney disease : focus on sex-specific associations with vascular outcomes and all-cause mortality
  • 2021
  • Ingår i: Biology of Sex Differences. - : Springer Science and Business Media LLC. - 2042-6410. ; 12:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Sex differences are underappreciated in the current understanding of cardiovascular disease (CVD) in association with chronic kidney disease (CKD). A hallmark of CKD is vascular aging that is characterised, amongst others, by; systemic inflammation, microbiota disbalance, oxidative stress, and vascular calcification—features linked to atherosclerosis/arteriosclerosis development. Thus, it is the necessary to introduce novel biomarkers related to athero-/arteriosclerotic damage for better assessment of vascular ageing in patients CKD. However, little is known about the relationship between uraemia and novel CVD biomarkers, such as growth differentiation factor-15 (GDF-15), cartilage glycoprotein-39 (YKL-40) and matrix metalloproteinase-9 (MMP-9). Therefore, we hypothesise that there are sex-specific relationships between GDF-15, YKL-40, MMP-9 levels in end-stage kidney disease (ESKD) patients in relation to gut microbiota, vascular calcification, inflammation, comorbidities, and all-cause mortality. Methods: ESKD patients, males (n = 151) and females (n = 79), not receiving renal replacement therapy were selected from two ongoing prospective ESKD cohorts. GDF-15, YKL-40 and MMP9 were analysed using enzyme-linked immunosorbent assay kits. Biomarker levels were analysed in the context of gut microbiota-derived trimethylamine N-oxide (TMAO), vascular calcification, inflammatory response, oxidative stress, comorbidities, and all-cause mortality. Results: Increased GDF-15 correlated with higher TMAO in females only, and with higher coronary artery calcification and IL-6. In females, diabetes was associated with elevated GDF-15 and MMP-9, whilst males with diabetes only had elevated GDF-15. No associations were found between biomarkers and CVD comorbidity. Deceased males and females had higher GDF-15 concentrations (p = 0.01 and p < 0.001, respectively), meanwhile only YKL-40 was increased in deceased males (p = 0.02). Conclusions: In conclusion, in males GDF-15 and YKL-40 were related to vascular calcification, inflammation, and oxidative stress, whilst in females GDF-15 was related to TMAO. Increased levels of YKL-40 and GDF-15 in males, and only GDF-15 in females, were associated with all-cause mortality. Our findings suggest that sex-specific associations of novel CVD biomarkers have a potential to affect development of cardiovascular complications in patients with ESKD.
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26.
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27.
  • Lilienberg, Elsa, et al. (författare)
  • In vivo Drug Delivery Performance of Lipiodol-based Emulsion or Drug-eluting Beads in Patients with Hepatocellular Carcinoma
  • 2017
  • Ingår i: Molecular Pharmaceutics. - : American Chemical Society (ACS). - 1543-8384 .- 1543-8392. ; 14:2, s. 448-458
  • Tidskriftsartikel (refereegranskat)abstract
    • Doxorubicin (DOX) delivered in a lipiodol-based emulsion (LIPDOX) or in drug-eluting beads (DEBDOX) is used as palliative treatment in patients with intermediate-stage hepatocellular carcinoma (HCC). The primary objective of this study was to evaluate the in vivo delivery performance of DOX from LIPDOX or DEBDOX in HCC patients using the local and systemic pharmacokinetics of DOX and its main metabolite doxorubicinol (DOXol). Urinary excretion of DOX and DOXol, and their short-term safety and anti-tumor effects were also evaluated. In this open, prospective, non-randomized multi-center study, LIPDOX (n=13) or DEBDOX (n=12) were injected into the feeding arteries of the tumor. Local (vena cava/hepatic vein orifice) and systemic (peripheral vein) plasma concentrations of DOX and DOXol were determined in samples obtained up to 6 h and 7 days after treatment. Tumor response was assessed using computed tomography or magnetic resonance imaging. The Cmax and AUC0-24 h for DOX were 5.6-fold and 2.4-fold higher in LIPDOX vs DEBDOX recipients, respectively (p <0.001). After 6 h, the respective mean proportions of the dose remaining in the liver or drug-delivery system (DDS) were 49% for LIPDOX and 88% for DEBDOX. LIPDOX releases DOX faster than DEBDOX in HCC patients and provides more extensive local and systemic exposure (AUC) to DOX and DOXol initially (0-7 days). DEBDOX formulation has a release and distribution of DOX that is more restricted and rate controlled than LIPDOX.
  •  
28.
  • Niklasson, Erik, et al. (författare)
  • Assessment of anterior thigh muscle size and fat infiltration using single-slice CT imaging versus automated MRI analysis in adults
  • 2022
  • Ingår i: British Journal of Radiology. - London, United Kingdom : British Institute of Radiology. - 0007-1285 .- 1748-880X. ; 95:1133
  • Tidskriftsartikel (refereegranskat)abstract
    • Objectives: We examined the longitudinal and cross- sectional relationship between automated MRI-analysis and single-slice axial CT imaging for determining muscle size and muscle fat infiltration (MFI) of the anterior thigh.Methods: Twenty-two patients completing sex-hormone treatment expected to result in muscle hypertrophy (n = 12) and atrophy (n = 10) underwent MRI scans using 2-point Dixon fat/water-separated sequences and CT scans using a system operating at 120 kV and a fixed flux of 100 mA. At baseline and 12 months after, auto- mated volumetric MRI analysis of the anterior thigh was performed bilaterally, and fat-free muscle volume and MFI were computed. In addition, cross-sectional area (CSA) and radiological attenuation (RA) (as a marker of fat infiltration) were calculated from single slice axial CT-images using threshold-assisted planimetry. Linear regression models were used to convert units.Results: There was a strong correlation between MRI- derived fat-free muscle volume and CT-derived CSA (R = 0.91), and between MRI-derived MFI and CT-derived RA (R = −0.81). The 95% limits of agreement were ±0.32 L for muscle volume and ±1.3% units for %MFI. The longi- tudinal change in muscle size and MFI was comparable across imaging modalities.Conclusions: Both automated MRI and single-slice CT-imaging can be used to reliably quantify anterior thigh muscle size and MFI.Advances in knowledge: This is the first study examining the intermodal agreement between automated MRI anal- ysis and CT-image assessment of muscle size and MFI in the anterior thigh muscles. Our results support that both CT- and MRI-derived measures of muscle size and MFI can be used in clinical settings.
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29.
  • Parker, Louis P., et al. (författare)
  • Cannulation configuration and recirculation in venovenous extracorporeal membrane oxygenation
  • 2022
  • Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 12:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Venovenous extracorporeal membrane oxygenation is a treatment for acute respiratory distress syndrome. Femoro-atrial cannulation means blood is drained from the inferior vena cava and returned to the superior vena cava; the opposite is termed atrio-femoral. Clinical data comparing these two methods is scarce and conflicting. Using computational fluid dynamics, we aim to compare atrio-femoral and femoro-atrial cannulation to assess the impact on recirculation fraction, under ideal conditions and several clinical scenarios. Using a patient-averaged model of the venae cavae and right atrium, commercially-available cannulae were positioned in each configuration. Additionally, occlusion of the femoro-atrial drainage cannula side-holes with/without reduced inferior vena cava inflow (0-75%) and retraction of the atrio-femoral drainage cannula were modelled. Large-eddy simulations were run for 2-6L/min circuit flow, obtaining time-averaged flow data. The model showed good agreement with clinical atrio-femoral recirculation data. Under ideal conditions, atrio-femoral yielded 13.5% higher recirculation than femoro-atrial across all circuit flow rates. Atrio-femoral right atrium flow patterns resembled normal physiology with a single large vortex. Femoro-atrial cannulation resulted in multiple vortices and increased turbulent kinetic energy at > 3L/min circuit flow. Occluding femoro-atrial drainage cannula side-holes and reducing inferior vena cava inflow increased mean recirculation by 11% and 32%, respectively. Retracting the atrio-femoral drainage cannula did not affect recirculation. These results suggest that, depending on drainage issues, either atrio-femoral or femoro-atrial cannulation may be preferrable. Rather than cannula tip proximity, the supply of available venous blood at the drainage site appears to be the strongest factor affecting recirculation.
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30.
  • Parker, Louis P., et al. (författare)
  • Computational Fluid Dynamics of the Right Atrium : A Comparison of Modeling Approaches in a Range of Flow Conditions
  • 2022
  • Ingår i: Journal of Engineering and Science in Medical Diagnostics and Therapy. - : ASME International. - 2572-7958 .- 2572-7966. ; 5:3
  • Tidskriftsartikel (refereegranskat)abstract
    • The right atrium (RA) combines flows from the inferior (IVC) and superior vena cava (SVC). Here RA mixing is simulated using computational fluid dynamics, comparing four modeling approaches. A patient-averaged model (11 M cells) was created from four volunteers. We compared: (1) unsteady k–ω Reynolds-averaged Navier–Stokes (URANS) (2) implicit large eddy simulation with second-order upwind convection scheme (iLES-SOU) (3) iLES with bounded-central difference convection scheme (iLES-BCD) and (4) LES with wall-adapting local eddy-viscosity (LES-WALE). A constant inlet flow rate of 6 L/min was applied with both IVC/SVC contributions ranging from 30–70%. A higher density mesh (37 M cells) was also simulated for models 2 and 4 (equal IVC/SVC flow) to assess the accuracy of models 1–4. Results from the 11 M cell LES-WALE model showed good agreement with the 37 M cell meshes. All four 11 M cell models captured the same large-scale flow structures. There were local differences in velocity, time-averaged wall shear stress, and IVC/SVC mixing when compared to LES-WALE, particularly at high SVC flow. Energy spectra and velocity animations from the LES-WALE model suggest the presence of transitional flow. For the general flow structures, all four methods provide similar results, though local quantities can vary greatly. On coarse meshes, the convection scheme and subgrid-scale (SGS) model have a significant impact on results. For RA flows, URANS should be avoided and iLES models are sensitive to convection scheme unless used on a highly resolved grid.
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31.
  • Parker, Louis P., et al. (författare)
  • Hemodynamic and recirculation performance of dual lumen cannulas for venovenous extracorporeal membrane oxygenation
  • 2023
  • Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 13:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Venovenous extracorporeal membrane oxygenation (ECMO) can be performed with two single lumen cannulas (SLCs) or one dual-lumen cannula (DLC) where low recirculation fraction (Rf) is a key performance criterion. DLCs are widely believed to have lower Rf , though these have not been directly compared. Similarly, correct positioning is considered critical although its impact is unclear. We aimed to compare two common bi-caval DLC designs and quantify R f in several positions. Two different commercially available DLCs were sectioned, measured, reconstructed, scaled to 27Fr and simulated in our previously published patient-averaged computational model of the right atrium (RA) and venae cavae at 2–6 L/min. One DLC was then used to simulate ± 30° and ± 60° rotation and ± 4 cm insertion depth. Both designs had low Rf (< 7%) and similar SVC/IVC drainage fractions and pressure drops. Both cannula reinfusion ports created a high-velocity jet and high shear stresses in the cannula (> 413 Pa) and RA (> 52 Pa) even at low flow rates. Caval pressures were abnormally high (16.2–23.9 mmHg) at low flow rates. Rotation did not significantly impact Rf . Short insertion depth increased Rf (> 31%) for all flow rates whilst long insertion only increased Rf at 6 L/min (24%). Our results show that DLCs have lower Rf compared to SLCs at moderate-high flow rates (> 4 L/min), but high shear stresses. Obstruction from DLCs increases caval pressures at low flow rates, a potential reason for increased intracranial hemorrhages. Cannula rotation does not impact Rf though correct insertion depth is critical.
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32.
  • Parker, Louis P., et al. (författare)
  • Impact of altered vena cava flow rates on right atrium flow characteristics
  • 2022
  • Ingår i: Journal of applied physiology. - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 132:5, s. 1167-1178
  • Tidskriftsartikel (refereegranskat)abstract
    • The right atrium (RA) combines the superior vena cava (SVC) and inferior vena cava (IVC) flows. Treatments like extracorporeal membrane oxygenation (ECMO) and hemodialysis by catheter alter IVC/SVC flows. Here we assess how altered IVC/SVC flow contributions impact RA flow. Four healthy volunteers were imaged with computerized tomography (CT), reconstructed and combined into a patient-averaged model. Large eddy simulations (LESs) were performed for a range of IVC/SVC flow contributions (30%-70% each, increments of 5%) and common flow metrics were recorded. Model sensitivity to reconstruction domain extent, constant/pulsatile inlets, and hematocrit was also assessed. Consistent with literature, a single vortex occupied the central RA across all flowrates with a smaller counter-rotating vortex, not previously reported, in the auricle. Vena cava flow was highly helical. RA turbulent kinetic energy (TKE; P = 0.027) and time-averaged wall shear stress (WSS; P < 0.001) increased with SVC flow. WSS was lower in the auricle (2 Pa, P < 0.001). WSS in the vena cava was equal at IVC/SVC = 65/35%. The model was highly sensitive to the reconstruction domain with cropped geometries lacking helicity in the venae cavae, altering the RA flow. The RA flow was not significantly affected by constant inlets or hematocrit. The commonly reported vortex in in the central RA is confirmed; however, a new, smaller vortex was also recorded in the auricle. When IVC flow dominates, as is normal, TKE in the RA is reduced and WSS in the venae cavae equalize. Significant helicity exists in the vena cava, as a result of distal geometry and this geometry appears crucial to accurately simulating RA flow. NEW & NOTEWORTHY Right atrium turbulent kinetic energy increases as the proportion of flow entering from the superior vena cava is increased. Although the commonly reported large right atrium vortex was confirmed across all flow scenarios, a new smaller vortex is observed in the right auricle. The caval veins exhibit highly helical flow and this appears to be the result of distal venous morphology.
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33.
  • Parker, Louis P., et al. (författare)
  • In silico parametric analysis of femoro-jugular venovenous ECMO and return cannula dynamics : In silico analysis of femoro-jugular VV ECMO
  • 2024
  • Ingår i: Medical Engineering and Physics. - : Elsevier BV. - 1350-4533 .- 1873-4030. ; 125
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: : Increasingly, computational fluid dynamics (CFD) is helping explore the impact of variables like: cannula design/size/position/flow rate and patient physiology on venovenous (VV) extracorporeal membrane oxygenation (ECMO). Here we use a CFD model to determine what role cardiac output (CO) plays and to analyse return cannula dynamics. Methods: : Using a patient-averaged model of the right atrium and venae cava, we virtually inserted a 19Fr return cannula and a 25Fr drainage cannula. Running large eddy simulations, we assessed cardiac output at: 3.5–6.5 L/min and ECMO flow rate at: 2–6 L/min. We analysed recirculation fraction (Rf), time-averaged wall shear stress (TAWSS), pressure, velocity, and turbulent kinetic energy (TKE) and extracorporeal flow fraction (EFF = ECMO flow rate/CO). Results: : Increased ECMO flow rate and decreased CO (high EFF) led to increased Rf (R = 0.98, log fit). Negative pressures developed in the venae cavae at low CO and high ECMO flow (high CR). Mean return cannula TAWSS was >10 Pa for all ECMO flow rates, with majority of the flow exiting the tip (94.0–95.8 %). Conclusions: : Our results underpin the strong impact of CO on VV ECMO. A simple metric like EFF, once supported by clinical data, might help predict Rf for a patient at a given ECMO flow rate. The return cannula imparts high shear stresses on the blood, largely a result of the internal diameter.
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34.
  • Parker, Louis P., et al. (författare)
  • Venovenous extracorporeal membrane oxygenation drainage cannula performance : From generalized to patient-averaged vessel model
  • 2024
  • Ingår i: Physics of fluids. - : AIP Publishing. - 1070-6631 .- 1089-7666. ; 36:6
  • Tidskriftsartikel (refereegranskat)abstract
    • Venovenous extracorporeal membrane oxygenation is used for respiratory support in the most severe cases of acute respiratory distress syndrome. Blood is drained from the large veins, oxygenated in an artificial lung, and returned to the right atrium (RA). In this study, we have used large eddy simulations to simulate a single-stage “lighthouse” drainage cannula in a patient-averaged model of the large veins and RA, including the return cannula. We compared the results with previous experimental and numerical studies of these cannulas in idealized tube geometries. According to the simulations, wall proximity at the drainage holes and the presence of the return cannula greatly increased drainage through the tip (33% at 5 L/min). We then simulated a multi-stage device in the same patient-averaged model, showing similar recirculation performance across the range of extracorporeal membrane oxygenation (ECMO) flow rates compared to the lighthouse cannula. Mean and maximum time-averaged wall shear stress were slightly higher for the lighthouse design. At high ECMO flow rates, the multi-stage device developed a negative caval pressure, which may be a cause of drainage obstruction in a clinical environment. Finally, through calculation of the energy spectra and vorticity field, we observed ring-like vortices inside the cannula originating from the side holes, most prominent in the proximal position. Our work highlights the important differences between a patient-derived and simplified venous model, with the latter tending to underestimate tip drainage. We also draw attention to the different dynamics of single-stage and multistage drainage cannulas, which may guide clinical use.
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35.
  • Persson, Anders, 1953-, et al. (författare)
  • Volume rendering compared with maximum intensity projection for magnetic resonance angiography measurements of the abdominal aorta
  • 2004
  • Ingår i: Acta Radiologica. - : SAGE Publications. - 0284-1851 .- 1600-0455. ; 45:4, s. 453-459
  • Tidskriftsartikel (refereegranskat)abstract
    • Purpose: To compare the volume rendering technique (VRT) with maximum intensity projection (MIP) for aortic diameter measurements in MR angiography (MRA) data sets.Material and Methods: Existing contrast-enhanced 3-dimensional MRA and digital subtraction angiography (DSA) data sets from 20 patients were analyzed. In each MRA data set, two aortic diameters were measured using MIP and VRT. Agreement with DSA measurements, dependence on rendering parameters, and interobserver agreement were assessed.Results: Diameters measured on MIP with fixed parameters showed no significant difference compared with DSA and with freely selected parameters a slight overestimation relative to DSA. Diameters measured on VRT were larger than on DSA. For both MIP and VRT, the measurements depended on the chosen parameters. The error relative to DSA was larger for VRT than for MIP with fixed parameters but not with freely chosen parameters. Interobserver agreement did not differ significantly.Conclusions: VRT is not suitable for diameter measurements of the abdominal aorta with fixed parameter settings but may be useful with user-selected settings.
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36.
  • Rickenlund, Anette, et al. (författare)
  • Effects of oral contraceptives on body composition and physical performance in female athletes.
  • 2004
  • Ingår i: Journal of Clinical Endocrinology and Metabolism. - : The Endocrine Society. - 0021-972X .- 1945-7197. ; 36:5, s. S34-S34
  • Tidskriftsartikel (refereegranskat)abstract
    • Menstrual disturbances are common among female athletes, and oral contraceptives (OCs) are often recommended as estrogen substitution. However, there is little information about the effects of OC use in athletes, and there is great concern that OCs might impair physical performance. The aim of this study was to investigate the effects of OC use on body composition and physical performance in female athletes. Twenty-six endurance athletes (13 with oligo-/amenorrhea and 13 regularly menstruating athletes) and 12 sedentary controls were examined before and after 10 months of treatment with a low dose, monophasic, combined OC. Significant changes in body composition were recorded in the athletes, but not in the controls. There was an increase in weight and fat mass only in athletes with oligo-/amenorrhea. These changes were associated with a decrease in ovarian androgens. OC treatment also increased bone mineral density, with the largest increase in athletes with a low bone mineral density at baseline. Despite significant changes in body composition, little impact on physical performance was recorded. We have demonstrated that OC treatment in female athletes has predominantly beneficial effects on body composition without adverse effects on physical performance and could be used for the prevention of osteoporosis in athletic amenorrhea. However, it cannot be excluded that a marked increase in fat mass might have unfavorable effects for athletic performance in individual women.
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37.
  • Rickenlund, Anette, et al. (författare)
  • Hyperandrogenicity is an alternative mechanism underlying oligomenorrhea or amenorrhea in female athletes and may improve physical performance.
  • 2003
  • Ingår i: Fertility and Sterility. - : Elsevier BV. - 0015-0282 .- 1556-5653. ; 79:4, s. 947-55
  • Tidskriftsartikel (refereegranskat)abstract
    • OBJECTIVE: To evaluate endocrine mechanisms underlying oligomenorrhea or amenorrhea in female athletes. DESIGN: Cross-sectional study. SETTING: Women's health clinical research unit at a university hospital. PATIENT(S): Age- and BMI-matched groups of athletes active in endurance sports with and without menstrual disturbances and regularly cycling sedentary controls. INTERVENTION(S): Groups were compared with respect to endocrine status, body composition, and physical performance. MAIN OUTCOME MEASURE(S): Identification of a subgroup of oligomenorrheic or amenorrheic athletes with increased androgen levels and anabolic body composition. RESULT(S): A subgroup of 8 of 25 athletes with menstrual disturbances had significantly higher serum levels of free and total testosterone, androstenedione, LH-FSH ratio, and lower SHBG levels than did all other groups. Other oligomenorrheic or amenorrheic athletes had normal values comparable to those in regularly menstruating athletes and controls. The hyperandrogenic subgroup showed a more anabolic body composition, with higher total bone mineral density and upper-lower fat mass ratio than did oligomenorrheic or amenorrheic athletes with normal androgen levels. The hyperandrogenic subgroup had the highest VO2 max and the highest performance values in general. CONCLUSION(S): Menstrual disturbances in female athletes are often explained as a consequence of hypothalamic inhibition and caloric deficiency. We suggest that essential hyperandrogenism is an alternative mechanism underlying oligomenorrhea or amenorrhea in some female athletes and may imply an advantage for physical performance.
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38.
  • Ripsweden, Jonaz, et al. (författare)
  • Impact on image quality and radiation exposure in coronary CT angiography: 100 kVp versus 120 kVp
  • 2010
  • Ingår i: Acta Radiologica. - : SAGE Publications. - 1600-0455 .- 0284-1851. ; 51:8, s. 903-909
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: The risk of radiation-induced cancer has become a major concern with the increasing use of computed tomography (CT). Purpose: To compare image quality and radiation doses when decreasing X-ray tube peak kilovoltage (kVp) from 120 to 100 kVp in patients undergoing coronary CT angiography (CCTA). Material and Methods: Patients referred for evaluation of suspected coronary artery disease (CAD) underwent 64-channel detector CCTA using a tube voltage of either 120 kVp (n = 46) or 100 kVp (n = 82). The individual volume CT dose index (CTDIvol) and dose length product (DLP) were recorded and effective radiation dose was estimated on the basis of DLP. Subjective image quality was assessed by two radiologists on per-patient based consensus. Vascular density and image noise were quantified in the left main coronary artery (LMCA) and proximal ascending aorta (AA). Mean density in the adjacent perivascular tissue was also quantified. Contrast-to-noise ratio (CNR) was calculated. Corresponding invasive coronary angiography (ICA) was performed, which constituted the gold standard. Results: Mean values in the 100120 kVp cohorts regarding CNR in the LMCA were 12.716.0 (P < 0.0001)) and in the AA 13.217.2 (P < 0.0001), CTDIvol 34.457.4 mGy (a 40% reduction, P < 0.0001), DLP 5781125 mGy X cm (P < 0.0001), and estimated effective dose 9.620.2 mSv (P < 0.0001). There was no statistically significant difference in subjective image quality between the two cohorts. The sensitivity to detect significant coronary stenoses was 88% (120 kVp) and 84% (100 kVp) and the specificity was 71% (120 kVp) and 74% (100 kVp), respectively. Conclusion: By reduction of tube voltage from 120 to 100 kVp at CCTA, while keeping all other scanning parameters unchanged, the radiation dose to the patient can be almost halved while keeping the diagnostic image quality at a clinically acceptable level.
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39.
  • Svensson, Anders, et al. (författare)
  • Automatic individualized contrast medium dosage during hepatic computed tomography by using computed tomography dose index volume (CTDIvol)
  • 2014
  • Ingår i: European Radiology. - : Springer Science and Business Media LLC. - 0938-7994 .- 1432-1084. ; 24:8, s. 1959-1963
  • Tidskriftsartikel (refereegranskat)abstract
    • To compare hepatic parenchymal contrast media (CM) enhancement during multi-detector row computed tomography (MDCT) and its correlation with volume pitch-corrected computed tomography dose index CTDIvol) and body weight (BW). One hundred patients referred for standard three-phase thoraco-abdominal MDCT examination were enrolled. BW was measured in the CT suite. Forty grams of iodine was administered intravenously (iodixanol 320 mg I/ml at 5 ml/s or iomeprol 400 mg I/ml at 4 ml/s) followed by a 50-ml saline flush. CTDIvol presented by the CT equipment during the parenchymal examination was recorded. The CM enhancement of the liver was defined as the attenuation HU of the liver parenchyma during the hepatic parenchymal phase minus the attenuation in the native phase. Liver parenchymal enhancement was negatively correlated to both CTDIvol (r = -0.60) and BW (r = -0.64), but the difference in correlation between those two was not significant. CTDIvol may replace BW when adjusting CM doses to body size. This makes it potentially feasible to automatically individualize CM dosage by CT. aEuro cent CTDI (vol) is related to liver CM enhancement in the parenchymal phase. aEuro cent CTDI (vol) provides comparable information to body weight (BW). aEuro cent CTDI (vol) may be used when automatically adjusting CM dose for patient size.
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40.
  • Svensson, Anders, et al. (författare)
  • Hepatic contrast medium enhancement at computed tomography and its correlation with various body size measures
  • 2012
  • Ingår i: Acta Radiologica. - : SAGE Publications. - 1600-0455 .- 0284-1851. ; 53:6, s. 601-606
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: When the same dose of iodine is given to all patients when performing abdominal computed tomography (CT) there may be a wide inter-individual variation in contrast medium (CM) enhancement of the liver. Purpose: To evaluate if any of the measures body height (BH), body mass index (BMI), lean body mass (LBM), ideal body weight (IBW), and body surface area (BSA) correlated better than body weight (BW) with hepatic enhancement, and to compare the enhancement when using iodixanol and iomeprol. Material and Methods: One hundred patients referred for standard three-phase CT examination of abdomen were enrolled. Body weight and height were measured at the time of the CT examination. Forty grams of iodine (iodixanol 320 mg l/mL or iomeprol 400 mg l/mL) was injected at a rate of 1.6 g-l/s, followed by a 50 mL saline flush. The late arterial phase was determined by using a semi-automatic smart prep technique with a scan delay of 20 s. The hepatic parenchymal phase started automatically 25 s after the late arterial phase. CM concentration was estimated by placement of regions of interest in aorta (native and late arterial phase) and in liver (native and parenchymal phase). Results: BW (r = -0.51 and -0.64), LBM (r = -0.54 and -0.59), and BSA (r = -0.54 and -0.65) showed the best correlation coefficients with aortic and hepatic parenchymal enhancement, respectively, without any significant differences between the measures. Comparing iodixanol and iomeprol there was no significant difference in aortic enhancement. The liver enhancement was significantly higher (P < 0.05) using iodixanol than iomeprol. Conclusion: To achieve a consistent hepatic enhancement, CM dose may simply be adjusted to body weight instead of using more complicated calculated parameters based on both weight and height.
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41.
  •  
42.
  • Valdimarsson, Valentinus T., et al. (författare)
  • Repeat procedures for recurrent colorectal liver metastases : Analysis of long-term liver regeneration and outcome
  • 2019
  • Ingår i: Cancer Management and Research. - 1179-1322. ; 11, s. 2617-2622
  • Tidskriftsartikel (refereegranskat)abstract
    • Background and aim: Repeat hepatectomy is increasingly performed for the management of recurrent colorectal liver metastases (CRLM). The aim of this study was to evaluate longterm functional liver volume (FLV) after a second hepatic procedure and to measure survival outcome. Methods: In this retrospective cohort study, patients treated for recurrent CRLM in the years 2005-2015 at two liver centers were included. Total FLV was calculated before the first procedure and before and after the second procedure. Overall survival was calculated. Results: Eighty-two patients were identified. The median follow-up was 53 (40-71) months from the first procedure. The median interval between first and second procedure was 13 (8-22) months. The initial FLV was 1584 (1313-1927) mL. The FLV was 1438 (1204-1896) mL after the first procedure and 1470 (1172-1699) mL after the second procedure (P<0.001). After the second procedure, a total of ten patients (12%) had a residual liver volume of less than 75% of the initial liver volume. The 5-year overall survival was 37 (26-54)% after the second procedure. Conclusion: Small changes in FLV were found after two hepatic procedures but with considerable inter-individual variation. Patients selected for a repeated hepatic procedure for recurrent CRLM had an acceptable survival.
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43.
  •  
44.
  • Wang, Qing, et al. (författare)
  • Multimodal perioperative assessment of liver function and volume in patients undergoing hepatectomy for colorectal liver metastasis : a comparison of the indocyanine green retention test, 99mTc mebrofenin hepatobiliary scintigraphy and gadoxetic acid enhanced MRI
  • 2022
  • Ingår i: British Journal of Radiology. - : British Institute of Radiology. - 0007-1285 .- 1748-880X. ; 95:1139
  • Tidskriftsartikel (refereegranskat)abstract
    • Objectives: To compare the dynamic changes in future liver remnant (FLR) function and volume after hepatec-tomy and to evaluate the associations between three modalities in assessment of liver function.Methods: Liver function and volume were quantified pre-operatively, at post-operative day (POD) 7 and POD 28 in 10 patients with colorectal liver metastases under-going hemihepatectomy using the indocyanine green retention (ICG) test, hepatobiliary scintigraphy (HBS) and gadoxetic acid-enhanced MRI. The 99mTc mebro-fenin uptake rate in the FLR was applied as a reference of liver function. MRI-derived parameters including liver- to-muscle ratio (LMR), liver - to-spleen ratio (LSR) and hepatocellular uptake index (HUI) were used for liver function assessment. Spearman's correlation analysis was used to evaluate the associations.Results: Increase in liver function ranged from 13 to 152% (median 92%) and in volume from 37 to 134% (median 79%). There was no significant discrepancy in increase between FLR function and volume during the first month following hepatectomy. LMR showed a significant corre-lation to ICG test (r = -0.66, p < 0.05) while LSR had an association with standardized FLR function obtained by HBS (r = -0.71, p < 0.05). During the first week after hepatectomy, pre-operative HUI and LMR showed the strongest correlation to the FLR growth in function and volume respectively (p < 0.05).Conclusion: The observed growth in FLR volume is closely related to the functional increase within 1 month after hepatectomy. Gadoxetic acid-enhanced MRI might substitute HBS for regional liver function assessment and provide an imaging tool for liver growth prediction.Advances in knowledge: Liver function growth was parallel with liver volume increase during the perioper-ative period. Liver function assessment with gadoxetic acid-enhanced MRI was comparable with that of HBS indicating that gadoxetic acid-enhanced MRI could substitute HBS for regional liver function evaluation.
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45.
  • Wiik, Anna, et al. (författare)
  • Muscle Strength, Size, and Composition Following 12 Months of Gender-affirming Treatment in Transgender Individuals
  • 2020
  • Ingår i: Journal of Clinical Endocrinology and Metabolism. - : ENDOCRINE SOC. - 0021-972X .- 1945-7197. ; 105:3, s. E805-E813
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. As many sports are divided in male/female categories, governing bodies have formed regulations on the eligibility for transgender individuals to compete in these categories. Yet, the magnitude of change in muscle mass and strength with gender-affirming treatment remains insufficiently explored. Objective. This study explored the effects of gender-affirming treatment on muscle function, size, and composition during 12 months of therapy. Design, settings, participants. In this single-center observational cohort study, untrained transgender women (TW, n = 11) and transgender men (TM, n = 12), approved to start gender-affirming medical interventions, underwent assessments at baseline, 4 weeks after gonadal suppression of endogenous hormones but before hormone replacement, and 4 and 12 months after treatment initiation. Main outcome measures. Knee extensor and flexor strength were assessed at all examination time points, and muscle size and radiological density (using magnetic resonance imaging and computed tomography) at baseline and 12 months after treatment initiation. Results. Thigh muscle volume increased (15%) in TM, which was paralleled by increased quadriceps cross-sectional area (CSA) (15%) and radiological density (6%). In TW, the corresponding parameters decreased by -5% (muscle volume) and -4% (CSA), while density remained unaltered. The TM increased strength over the assessment period, while the TW generally maintained their strength levels. Conclusions. One year of gender-affirming treatment resulted in robust increases in muscle mass and strength in TM, but modest changes in TW. These findings add new knowledge on the magnitude of changes in muscle function, size, and composition with cross-hormone therapy, which could be relevant when evaluating the transgender eligibility rules for athletic competitions.
  •  
46.
  • Wilczek, Michael L., et al. (författare)
  • Can secondary osteoporosis be identified when screening for osteoporosis with digital X-ray radiogrammetry? : Initial results from the Stockholm Osteoporosis Project (STOP)
  • 2017
  • Ingår i: Maturitas. - : Elsevier. - 0378-5122 .- 1873-4111. ; 101, s. 31-36
  • Tidskriftsartikel (refereegranskat)abstract
    • Objectives: To identify causes of low age-adjusted bone mass at digital X-ray radiogrammetry (DXR) in individuals attending an osteoporosis screening program. Study design: In a descriptive observational cohort study, women aged 40-75 years who attended a general mammography screening program had their bone mass investigated with DXR and answered a questionnaire regarding several clinical risk factors for osteoporosis. Each month the 2% with the lowest Z-scores were selected for further clinical examination with DXA of the hip and lumbar spine and pre-defined blood tests. Main outcome measure: Causes of secondary osteoporosis determined by clinical and laboratory evaluation. Results: 14,783 women attended mammography screening and had their bone mass evaluated. In total, 327 women had a low DXR BMD and 281 accepted further DXA examination. Of these, 93 (33.1%) had osteoporosis. The diagnosis was new in 79 cases (84.9%) and in 32 (34.4%) a potential underlying cause was identified. Primary hyperparathyroidism was found in 8.6% and secondary hyperparathyroidism in 13.5%. Several self reported risk factors for osteoporosis, including rheumatic disease, insulin-treated diabetes, cortisone treatment, smoking, reduced mobility, hyperparathyroidism, and malabsorption, were significantly more common among those selected for DXA referral than in the total cohort. For example, rheumatic disease and insulin-treated diabetes were reported 3.4 and 2.3 times as often, respectively. Conclusion: The prevailing potential cause of secondary osteoporosis according to DXR was primary and secondary hyperparathyroidism. Most of the women with these conditions were previously undiagnosed, indicating that further follow-up of patients with low age-adjusted DXR BMD is justified.
  •  
47.
  • Wilczek, Michael L., et al. (författare)
  • Mammography and Osteoporosis Screening-Clinical Risk Factors and Their Association With Digital X-Ray Radiogrammetry Bone Mineral Density
  • 2015
  • Ingår i: Journal of clinical densitometry. - : Elsevier. - 1094-6950 .- 1559-0747. ; 18:1, s. 22-29
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim of this study was to study the association between digital X-ray radiogrammetry (DXR) T-score and clinical risk factors for osteoporosis. Women were recruited 2 d per wk at a single mammography screening center between year 2010 and 2012. Included women answered a questionnaire about risk factors for osteoporosis, and a radiograph of the nondominant hand was obtained for DXR analysis. Univariate associations between DXR T-score and risk factors were examined. A generalized linear regression model was fitted to independent variables with univariate associations at p less than 0.05. The multivariable model was reduced through manual backward elimination, with p greater than 0.1 as the exclusion criterion. Seventy-six percent of the women chose to participate in the study (n = 8810). The difference in number of daily mammograms performed on study vs nonstudy days was not significant. All univariate associations between DXR T-score and potential risk factors were highly significant. The multivariable model included height, weight, age, right-handedness, menopause before age 45, alcohol consumption, cortisone treatment, rheumatic disease, and age x smoking status. The coefficient of determination of the model was 0.37. The association between risk factors for osteoporosis and DXR T-score is similar to previously reported associations with dual-energy X-ray absorptiometry.
  •  
48.
  • Zhao, Ying, et al. (författare)
  • Multimodal Imaging of Pancreatic Ductal Adenocarcinoma Using Multifunctional Nanoparticles as Contrast Agents
  • 2020
  • Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 12:48, s. 53665-53681
  • Tidskriftsartikel (refereegranskat)abstract
    • Late diagnosis and refractory behavior toward current treatment protocols make pancreatic ductal adenocarcinoma (PDAC) one of the most difficult cancer forms to treat. The imaging-based approach plays an important role to identify potentially curable PDAC patients in high-risk groups at the early stage. In the present study, we developed a core-shell structured gold nanorod (AuNR) as a contrast agent for multimodal imaging and investigated its application for PDAC diagnosis. The composite nanopartides composed of a AuNR core inside a layer of mesoporous silica that was then coated with a gadolinium oxide carbonate shell (AuNR-SiO2 -Gd) are designed to be used in magnetic resonance imaging (MRI), X-ray computed tomography (CT), and photoacoustic imaging (PM). A phantom study with the AuNR-SiO2-Gd NPs demonstrated higher MRI contrast compared to Gadovist and higher X-ray attenuation than Visipaque. A strong, stable, and broad wavelength range signal with a peak at 800 nm was observed in PAI. The AuNR-SiO2-Gd NPs showed significant contrast enhancement under PAI/MRI/CT in both the liver and spleen of control mice after intravenous administration. The utility in PDAC was studied in a genetically engineered mouse model carrying Kras and p53 mutations, which develops spontaneous tumors and keeps the desmoplasia and hypovascularity feature of PDAC in patients. The AuNR-SiO2-Gd NPs were highly accumulated in the surrounding soft tissues but were sparsely distributed throughout the tumor due to dense stroma infiltration and poor tumor vascularization. Hence, a negative contrast within the tumor area in CT/PAI and a positive contrast in MRI were observed. In conclusion, AuNR-SiO2-Gd NPs have good potential to be developed as a multimodal contrast agent for PDAC, which might improve early diagnosis and benefit the clinical outcome for PDAC patients.
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