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| 2. |
- Peterson, Pernilla, et al.
(författare)
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Fat Quantification in Skeletal Muscle Using Multigradient-Echo Imaging: Comparison of Fat and Water References
- 2016
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Ingår i: Journal of Magnetic Resonance Imaging. - : WILEY-BLACKWELL. - 1053-1807 .- 1522-2586. ; 43:1, s. 203-212
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To investigate the precision, accuracy, and repeatability of water/fat imaging-based fat quantification in muscle tissue using a large flip angle (FA) and a fat reference for the calculation of the proton density fat fraction (FF). Comparison is made to a small FA water reference approach. Materials and Methods: An Intralipid phantom and both forearms of six patients suffering from lymphedema and 10 healthy volunteers were investigated at 1.5T. Two multigradient-echo sequences with eight echo times and FAs of 10 degrees and 85 degrees were acquired. For healthy volunteers, the acquisition of the right arm was performed twice with repositioning. From each set, water reference FF and fat reference FF images were reconstructed and the average FF and the standard deviation were calculated within the subfascial compartment. The small FA water reference was considered the reference standard. Results: A high agreement was found between the small FA water reference and large FA fat reference methods (FF bias=0.31%). In this study, the large FA fat reference approach also resulted in higher precision (38% smaller FF standard deviation in homogenous muscle tissue), but no significant difference in repeatability between the various methods was detected (coefficient of repeatability of small FA water reference approach 0.41%). Conclusion: The precision of fat quantification in muscle tissue can be increased with maintained accuracy using a larger flip angle, if a fat reference instead of a water reference is used.
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| 3. |
- Sterner, Gunnar, et al.
(författare)
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Determining 'true' glomerular filtration rate in healthy adults using infusion of inulin and comparing it with values obtained using other clearance techniques or prediction equations.
- 2008
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Ingår i: Scandinavian Journal of Urology and Nephrology. - : Informa UK Limited. - 0036-5599 .- 1651-2065. ; 42:3, s. 278-285
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Tidskriftsartikel (refereegranskat)abstract
- Objective. To determine 'true' glomerular filtration rate (GFR) in healthy adults as renal clearance following infusion of inulin, and compare that result with those obtained using other markers and clearance techniques and with estimations of GFR using creatinine-based prediction equations. Material and methods. Twenty healthy volunteers (11 females) with a median age of 27 years (range 19-36 years) received bolus doses of inulin and iohexol i.v. and 16 blood samples were taken after injection. Then, inulin and iohexol were infused to give stable plasma concentrations and blood and urine samples were collected. Residual bladder volume was estimated using ultrasound scanning. Plasma and urine concentrations of inulin and iohexol were determined using chromatography and resorcinol methods, respectively. Different methods of GFR determination were compared as well as four formulae for GFR estimation based on serum creatinine. Results. 'True' GFR, i.e. renal clearance of inulin during its infusion, was a median of 117 ml/min/1.73 m2 (inter-quartile range 106-129 ml/min/1.73 m2). Similar values of GFR were obtained with renal clearance of iohexol during its infusion and also with plasma (body) clearance of inulin or iohexol following bolus injections and using 16 or five plasma samples. Endogenous creatinine clearance was higher (p<0.001) than true GFR (median 23 ml/min/1.73 m2). Plasma clearance of iohexol and inulin based on their concentrations in four blood samples underestimated their renal clearance considerably. All four creatinine-based formulae markedly underestimated renal inulin clearance. Conclusions. Plasma and renal clearance of iohexol and inulin were similar in healthy adults. Underestimation of GFR was noted when plasma clearance of iohexol and inulin was based on four but not five or more blood samples. Some prediction equations underestimate true GFR to such an extent that caution must be taken when using them to evaluate normal or high GFR values.
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| 4. |
- Müller, Gunilla, et al.
(författare)
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Increased perfusion in dynamic gadolinium-enhanced MRI correlates with areas of bone repair and of bone necrosis in patients with Kienböck's disease
- 2019
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Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1053-1807 .- 1522-2586. ; 50:2, s. 481-489
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Tidskriftsartikel (refereegranskat)abstract
- Background: Osteonecrosis of the lunate, Kienböck's disease, can lead to fragmentation of the lunate, carpal collapse, and severe osteoarthritis. Since the etiology of Kienböck's disease is impaired circulation, a diagnostic method capable of assessing perfusion would be valuable. Recent studies have suggested that dynamic contrast-enhanced (DCE) MR examinations at 3 T can assess perfusion in healthy carpal bones. Purpose: To evaluate the use of DCE-MR for assessing perfusion in the lunate bone in patients with Kienböck's disease. Furthermore, to compare perfusion with histopathology with a focus on bone viability. Study Type: Prospective case–control study. Population: Fourteen patients with Kienböck's disease and a control group of 19 healthy subjects. Field Strength: 3 T with T1-weighted fat-saturated contrast-enhanced gradient echo series. Assessment: Features of the enhancement curves from the DCE-MR examinations, time to peak (TTP), maximum slope (MS), and maximum enhancement (ME) assessed by a radiologist. Six of 14 patients were surgerized with lunate excision, allowing comparison between features of the enhancement curves and histopathology. Statistical Tests: Mann–Whitney U-test. P < 0.05 was considered a statistically significant difference. Results: Patients with Kienböck's disease showed significantly higher and faster perfusion parameters compared with the control group, the mean value of the TTP in patients was 126.73 sec, in controls 189.79 sec (P = 0.024), ME in patients 173.55 AU, in controls 28.46 AU (P < 0.001), and MS in patients 5.04 AU, in controls 1.06 AU (P < 0.001). When compared with histopathology, increased perfusion was seen in areas of bone formation but also in necrosis. Areas of normal bone showed low perfusion. Data Conclusion: DCE-MRI at 3 T can diagnose altered perfusion in patients with Kienböck's disease. Increased perfusion cannot definitely be used as a marker of bone viability. Level of Evidence: 1. Technical Efficacy: Stage 3. J. Magn. Reson. Imaging 2018.
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| 5. |
- Sonesson, Mikael, et al.
(författare)
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Orthodontic appliances and MR image artefacts : An exploratory in vitro and in vivo study using 1.5-T and 3-T scanners
- 2021
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Ingår i: Imaging Science in Dentistry. - : Korean Academy of Oral and Maxillofacial Radiology. - 2233-7822 .- 2233-7830. ; 51
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: The aim of this study was to assess the artefacts of 12 fixed orthodontic appliances in magnetic resonance images obtained using 1.5-T and 3-T scanners, and to evaluate different imaging sequences designed to suppress metal artefacts. Materials and Methods: In vitro, study casts of 1 adult with normal occlusion were used. Twelve orthodontic appliances were attached to the study casts and scanned. Turbo spin echo (TSE), TSE with high readout bandwidth, and TSE with view angle tilting and slice encoding for metal artefact correction were used to suppress metal artefacts. Artefacts were measured. In vivo, 6 appliances were scanned: 1) conventional stainless-steel brackets; 2) nickelfree brackets; 3) titanium brackets; 4) a Herbst appliance; 5) a fixed retainer; and 6) a rapid maxillary expander. The maxilla, mandible, nasopharynx, tongue, temporomandibular joints, and cranial base/eye globes were assessed. Scores of 0, 1, 2, and 3 indicated no artefacts and minor, moderate, and major artefacts, respectively. Results: In vitro, titanium brackets and the fixed retainer created minor artefacts. In vivo, titanium brackets caused minor artefacts. Conventional stainless-steel and nickel free brackets, the fixed retainer, and the rapid maxillary expander caused major artefacts in the maxilla and mandible. Conventional stainless-steel and nickel-free brackets caused major artefacts in the eye globe (3-T). TSE with high readout bandwidth reduced image artefacts in both scanners. Conclusion: Titanium brackets, the Herbst appliance, and the fixed retainer caused minor artefacts in images of neurocranial structures(1.5-T and 3-T) when using TSE with high readout bandwidth.(Imaging Sci Dent 20200199)
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| 6. |
- Tufvesson, Hanna, et al.
(författare)
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Quantified small bowel motility in patients with ulcerative colitis and gastrointestinal symptoms : a pilot study
- 2021
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Ingår i: Acta Radiologica. - : SAGE Publications. - 0284-1851 .- 1600-0455. ; 62:7, s. 858-866
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Tidskriftsartikel (refereegranskat)abstract
- Background: Gastrointestinal (GI) symptoms are common in patients with ulcerative colitis (UC), even when the disease is in remission, possibly due to abnormalities in GI motility. Small bowel motility can be assessed globally and in specific intestinal regions during magnetic resonance enterography (MRE) using a displacement mapping technique. Purpose: To investigate whether small bowel motility in MRE differs between patients with UC and controls, and if altered motility correlates with GI symptoms. Material and Methods: In 2016–2018, patients who were admitted for MRE, regardless of clinical indication, were consecutively invited to the study. Healthy volunteers were recruited. The participants completed a questionnaire regarding GI symptoms and relevant clinical data were reviewed in the medical records. The dynamic imaging series obtained during MRE were sent for motility mapping and a motility index (MI) was calculated in jejunum, ileum and terminal ileum in all participants. Results: In total, 224 patients and healthy volunteers were enrolled in the study. Fifteen were diagnosed with UC and 22 were considered healthy controls. In UC, the prevalence of GI symptoms was higher than in controls (P < 0.001), both in remission and in active disease. There was no correlation between GI symptoms and small bowel motility in UC. Jejunal motility was lower in UC than in controls (P = 0.049). Conclusion: Jejunal motility is decreased in UC compared with healthy controls, but there is no relationship between small bowel motility and GI symptoms in UC.
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| 7. |
- Hörberg, Lisa, et al.
(författare)
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Reproducibility of measurements with a semi-automatic software package for the evaluation of rectal cancer
- 2020
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Ingår i: Acta Radiologica. - : SAGE Publications. - 0284-1851 .- 1600-0455. ; 61:5, s. 586-594
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Tidskriftsartikel (refereegranskat)abstract
- Background: Staging of rectal cancer with MRI has major impact on treatment choice and may be of importance in new cancer management strategies such as “wait-and-see” policy. Purpose: To assess the reproducibility of a software package recently developed at our department to measure volumes, apparent diffusion coefficient, and the skewness of apparent diffusion coefficient in lymph nodes and tumors in rectal cancer patients before and after chemoradiation treatment. Material and Methods: This study included 20 consecutive patients with biopsy-verified rectal cancer, in whom MRI staging had been performed both before and after chemoradiation treatment. The diffusion-weighted images were transferred to the software. The volume, apparent diffusion coefficient, and skewness were determined for 93 lymph nodes and 40 tumors. The volumes were compared with manual measurements of the volume of the same lymph nodes and tumors. Results: The agreement in semi-automatic measurements of lymph nodes was very good (ICC = 0.99), and in tumors good (ICC = 0.88). The agreement in manual measurements of lymph nodes was very good (ICC = 0.95) when all lymph nodes were included, but low (ICC = 0.52) if three outliers were excluded. Bland–Altman plots showed clear agreement between manual and semi-automatic measurements in the lymph nodes, but not in measurements of tumors. The values of apparent diffusion coefficient and skewness in tumors differed before and after treatment but did not differ in lymph nodes as a group. Conclusion: The software package showed a high degree of reproducibility in measurements on lymph nodes but requires further development to improve the reproducibility of tumor measurements.
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| 8. |
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| 9. |
- Bibic, Adnan, et al.
(författare)
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Measurement of vascular water transport in human subjects using time-resolved pulsed arterial spin labelling.
- 2015
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Ingår i: NMR in Biomedicine. - : Wiley. - 0952-3480. ; 28:8, s. 1059-1068
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Tidskriftsartikel (refereegranskat)abstract
- Most approaches to arterial spin labelling (ASL) data analysis aim to provide a quantitative measure of the cerebral blood flow (CBF). This study, however, focuses on the measurement of the transfer time of blood water through the capillaries to the parenchyma (referred to as the capillary transfer time, CTT) as an alternative parameter to characterise the haemodynamics of the system. The method employed is based on a non-compartmental model, and no measurements need to be added to a common time-resolved ASL experiment. Brownian motion of labelled spins in a potential was described by a one-dimensional general Langevin equation as the starting point, and as a Fokker-Planck differential equation for the averaged distribution of labelled spins at the end point, which takes into account the effects of flow and dispersion of labelled water by the pseudorandom nature of the microvasculature and the transcapillary permeability. Multi-inversion time (multi-TI) ASL data were acquired in 14 healthy subjects on two occasions in a test-retest design, using a pulsed ASL sequence and three-dimensional gradient and spin echo (3D-GRASE) readout. Based on an error analysis to predict the size of a region of interest (ROI) required to obtain reasonably precise parameter estimates, data were analysed in two relatively large ROIs, i.e. the occipital lobe (OC) and the insular cortex (IC). The average values of CTT in OC were 260 ± 60 ms in the first experiment and 270 ± 60 ms in the second experiment. The corresponding IC values were 460 ± 130 ms and 420 ± 139 ms, respectively. Information related to the water transfer time may be important for diagnostics and follow-up of cerebral conditions or diseases characterised by a disrupted blood-brain barrier or disturbed capillary blood flow. Copyright © 2015 John Wiley & Sons, Ltd.
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