| 61. |
- Nordström, Jonny, et al.
(författare)
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Effect of PET-CT misalignment on the quantitative accuracy of cardiac 15O-water PET
- 2022
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Ingår i: Journal of Nuclear Cardiology. - : Springer Science and Business Media LLC. - 1071-3581 .- 1532-6551. ; 29:3, s. 1119-1128
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Quantification of myocardial blood flow (MBF) with PET requires accurate attenuation correction, which is performed using a separate CT. Misalignment between PET and CT scans has been reported to be a common problem. The purpose of the present study was to assess the effect of PET CT misalignment on the quantitative accuracy of cardiac 15O-water PET.METHODS: Ten clinical patients referred for evaluation of ischemia and assessment of MBF with 15O-water were included in the study. Eleven different misalignments between PET and CT were induced in 6 different directions with 10 and 20 mm amplitudes: caudal (+Z), cranial (- Z), lateral (±X), anterior (+Y), and anterior combined with cranial (+ Y and - Z). Blood flow was quantified from rates of washout (MBF) and uptake (transmural MBF, MBFt) for the whole left ventricle and the three coronary territories. The results from all misalignments were compared to the original scan without misalignment.RESULTS: MBF was only minorly affected by misalignments, but larger effects were seen in MBFt. On the global level, average absolute deviation across all misalignments for MBF was 1.7% ± 1.4% and for MBFt 5.4% ± 3.2 Largest deviation for MBF was - 4.8% ± 5.8% (LCX, X + 20) and for MBFt - 19.3% ± 9.6% (LCX, X + 20). In general, larger effects were seen in LAD and LCX compared to in RCA.CONCLUSION: The quantitative accuracy of MBF from 15O-water PET, based on the washout of the tracer, is only to a minor extent affected by misalignment between PET and CT.
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| 62. |
- Nordström, Jonny, et al.
(författare)
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Influence of image reconstruction on quantitative cardiac 15O-water positron emission tomography
- 2023
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Ingår i: Journal of Nuclear Cardiology. - : Springer Nature. - 1071-3581 .- 1532-6551. ; 30:2, s. 716-725
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundThe impact on quantitative 15O-water PET/CT of a wide range of different reconstruction settings, including regularized reconstruction by block-sequential regularized expectation maximization (BSREM), was investigated.MethodsTwenty clinical stress scans from patients referred for assessment of myocardial ischemia were included. Patients underwent a 4-min dynamic stress PET scan with 15O-water on a digital PET/CT scanner. Twenty-two reconstructions were generated from each scan and a clinical reconstruction was used as reference. Varied parameters were number of iterations, filter, exclusion of time-of-flight and point-spread function, and regularization parameter with BSREM. Analyses were performed in aQuant utilizing two different methods and resulting regional myocardial blood flow (MBF), perfusable tissue fraction (PTF), and transmural MBF (MBFt) values were evaluated.ResultsAcross the two analyses, correlations toward the reference reconstruction were strong for all parameters (ρ ≥ 0.83). Using automated analysis and the diagnostic threshold of hyperemic MBF at 2.3 mL⋅g−1⋅min−1, diagnosis was unchanged irrespective of reconstruction method in all patients except for one, where only four of the most extreme reconstruction methods resulted in a change of diagnosis.ConclusionThe low sensitivity of MBF values to reconstruction method and, as previously shown, scanner type and PET/CT misalignment, confirms that diagnostic hyperemic MBF cutoff values can be consistently used for 15O-water.
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| 63. |
- Nordström, Jonny, et al.
(författare)
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Influence of patient motion on quantitative accuracy in cardiac 15O-water positron emission tomography.
- 2022
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Ingår i: Journal of Nuclear Cardiology. - : Springer Nature. - 1071-3581 .- 1532-6551. ; 29:4, s. 1742-1752
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Patient motion is a common problem during cardiac PET. The purpose of the present study was to investigate to what extent motions influence the quantitative accuracy of cardiac 15O-water PET/CT and to develop a method for automated motion detection.METHOD: Frequency and magnitude of motion was assessed visually using data from 50 clinical 15O-water PET/CT scans. Simulations of 4 types of motions with amplitude of 5 to 20 mm were performed based on data from 10 scans. An automated motion detection algorithm was evaluated on clinical and simulated motion data. MBF and PTF of all simulated scans were compared to the original scan used as reference.RESULTS: Patient motion was detected in 68% of clinical cases by visual inspection. All observed motions were small with amplitudes less than half the LV wall thickness. A clear pattern of motion influence was seen in the simulations with a decrease of myocardial blood flow (MBF) in the region of myocardium to where the motion was directed. The perfusable tissue fraction (PTF) trended in the opposite direction. Global absolute average deviation of MBF was 3.1% ± 1.8% and 7.3% ± 6.3% for motions with maximum amplitudes of 5 and 20 mm, respectively. Automated motion detection showed a sensitivity of 90% for simulated motions ≥ 10 mm but struggled with the smaller (≤ 5 mm) simulated (sensitivity 45%) and clinical motions (accuracy 48%).CONCLUSION: Patient motion can impair the quantitative accuracy of MBF. However, at typically occurring levels of patient motion, effects are similar to or only slightly larger than inter-observer variability, and downstream clinical effects are likely negligible.
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| 64. |
- Nordström, Jonny, et al.
(författare)
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Left ventricular volumes and ejection fraction from cardiac ECG-gated 15O-water positron emission tomography compared to cardiac magnetic resonance imaging using simultaneous hybrid PET/MR
- 2023
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Ingår i: Journal of Nuclear Cardiology. - : Springer Nature. - 1071-3581 .- 1532-6551. ; 30:4, s. 1352-1362
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Tidskriftsartikel (refereegranskat)abstract
- Background15O-water PET is the gold standard for noninvasive quantification of myocardial blood flow. In addition to evaluation of ischemia, the assessment of cardiac function and remodeling is important in all cardiac diseases. However, since 15O-water is freely diffusible and standard uptake images show little contrast between the myocardium and blood pool, the assessment of left-ventricular (LV) volumes and ejection fraction (EF) is challenging. Therefore, the aim of the present study was to investigate the feasibility of calculating LV volumes and EF from first-pass analysis of 15O-water PET, by comparison with cardiac magnetic resonance imaging (CMR) using a hybrid PET/MR scanner.MethodsTwenty-four patients with known or suspected CAD underwent a simultaneous ECG-gated cardiac PET/MR scan. The 15O-water first-pass images (0-50 seconds) were analyzed using the CarPET software and the CMR images were analyzed using the software Segment, for LV volumes and EF calculations. The LV volumes and EF were compared using correlation and Bland–Altman analysis. In addition, inter- and intra-observer variability of LV volumes and EF were assessed for both modalities.ResultsThe correlation between PET and CMR was strong for volumes (r > 0.84) and moderate for EF (r = 0.52), where the moderate correlation for EF was partly due to the small range of EF values. Agreement was high for all parameters, with a slight overestimation of PET values for end-diastolic volume but with no significant mean bias for other parameters. Inter- and intra-observer agreement of volumes was high and comparable between PET and CMR. For EF, inter-observer agreement was higher for PET and intra-observer agreement was higher for CMR.ConclusionLV volumes and EF can be calculated by first-pass analysis of a 15O-water PET scan with high accuracy and comparable precision as with CMR.
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| 65. |
- Nordström, Jonny
(författare)
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Quantitative cardiac 15O-water PET : Assessment of left-ventricular function, remodeling, and impact of patient motion
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- International guidelines advocate the use of noninvasive cardiac imaging as the initial diagnostic test for coronary artery disease, the global leading cause of death according to the world health organization. Within the wide spectrum of cardiac imaging, 15O-water PET is the gold standard for noninvasive quantification of myocardial blood flow (MBF). However, because 15O-water is a metabolically inert and freely diffusible tracer, the net retention of 15O-water in the myocardium is zero and there is no contrast between the myocardial wall and the cavity in a standard uptake image of 15O-water. The lack of contrast poses difficulties for the measurement of cardiac function and remodeling, paramount assessments for coronary artery disease evaluation along with MBF. Part one of the aim of this thesis is the development and evaluation of methods for assessment of cardiac function and remodeling in terms of left-ventricular (LV) volumes and ejection fraction (EF), LV mass (LVM), and LV wall thickness (WT). Part two is focused on patient motion, which occurs frequently in all cardiac PET studies and represents a possible source for induced error in the quantification of MBF. The feasibility of LV volumes and EF calculations was shown in paper I, where cardiac-gated parametric blood-pool images and first-pass images were imported into a commercially available software for SPECT. The method was, however, too laborious for clinical practice but served as an important proof-of-concept. In paper II, LV volumes and EF calculations were performed using first-pass images in the same software used for standard analysis of 15O-water PET and MBF assessment. The results were improved compared to paper I and the method was feasible for clinical implementation. In paper III, LVM and WT calculations were performed using segmentation of perfusable tissue fraction (PTF) images. The results showed high accuracy compared to cardiac magnetic resonance (MR) imaging, and the method was highly automated, allowing for ready clinical implementation. In papers IV-V, the impact of patient motion on the quantitative accuracy of 15O-water PET was investigated. Simulations showed a minimal impact of PET-CT misalignment on MBF, but did show that impact of dynamic motion during PET acquisition was more pronounced. Visual inspection of clinical scans showed frequent motion, but at a small amplitude with generally limited impact according to the simulations. An automated motion detection algorithm was developed which was highly accurate in detecting larger types of motion. A clear pattern of motion-induced artifacts were discovered, which may help improve their visual detection.
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| 66. |
- Nyström, Andreas, et al.
(författare)
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Denosumab Prevents Early Periprosthetic Bone Loss After Uncemented Total Hip Arthroplasty : Results from a Randomized Placebo-Controlled Clinical Trial
- 2020
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Ingår i: Journal of Bone and Mineral Research. - : Wiley. - 0884-0431 .- 1523-4681. ; 35:2, s. 239-247
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Tidskriftsartikel (refereegranskat)abstract
- Implant loosening is the most common indication for revision surgery after total hip arthroplasty (THA). Although bone resorption around the implants plays a pivotal role in the pathophysiology of loosening, it is unknown whether potent early inhibition of osteoclasts could mitigate this process and thus reduce the need for revision surgery. We performed a randomized, double-blind, placebo-controlled phase 2 trial in 64 patients aged 35 to 65 years with unilateral osteoarthritis of the hip. They underwent surgery with an uncemented THA and were randomized to either two subcutaneous doses of denosumab (n = 32) or placebo (n = 32) given 1 to 3 days and 6 months after surgery. Patients were followed for 24 months. Primary outcome was periprosthetic bone mineral density (BMD) of the hip at 12 months as measured by dual-energy X-ray absorptiometry (DXA). In addition, [18 F] sodium fluoride positron emission tomography/CT (F-PET) was performed in half of the patients for analysis of periprosthetic standardized uptake value (SUV). Analyses were made according to intention-to-treat principles. The trial was registered at ClinicalTrials.gov 2011-001481-18, NCT01630941. Denosumab potently inhibited early periprosthetic bone loss. After 12 months, BMD in the denosumab group was 32% (95% confidence interval [CI] 22-44) higher in Gruen zone 7 and 11% (95% CI 8-15) higher in zones 1 to 7. After 24 months, the difference in BMD between groups had decreased to 15% (95% CI 4-27) in zone 7 and 4% (95% CI 0-8) in zones 1 to 7. In both groups, SUV increased after surgery, but the increase was less pronounced in the denosumab group. Biochemical markers of bone metabolism decreased in the denosumab group in the first 12 months, but a rebound effect with marker concentrations above baseline was observed after 24 months. Denosumab potently prevents early periprosthetic bone loss after uncemented THA; however, the effect diminishes after discontinuation of treatment. Further research is needed to determine whether this bone loss will prove to be of clinical importance and, if so, whether the positive effect observed in this study could be preserved by either prolonged treatment with denosumab or additional antiresorptive treatment.
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| 67. |
- Nyström, Andreas, 1972-
(författare)
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Uncemented Total Hip Arthroplasty : Aspects on Bone Biology, Implant Fixation, Periprosthetic Bone Remodeling, Bone Mineral Density and Effects of Denosumab
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Uncemented total hip arthroplasty (THA) is associated with loss of periprosthetic bone mineral density (BMD). The collum femoris preserving (CFP) stem lost 28% of proximal BMD at 2 years. The overall purpose of this thesis was to study the long-term results of the CFP stem in BMD and implant stability (study III) and whether periprosthetic BMD can be preserved with denosumab (study I). Secondary objectives were to evaluate a CT-based technique as an alternative to radiostereometric analysis (RSA) and investigate the reliability, agreement, and precision of periprosthetic [18F]-fluoride PET/CT (F-PET). In study I, a randomized controlled trial, we studied the effect of denosumab on 1) periprosthetic BMD by dual-energy x-ray absorptiometry (DXA), 2) periprosthetic bone formation by F-PET, and 3) serum markers of bone turnover. We found that denosumab prevents early periprosthetic bone loss and reduces periprosthetic and systemic bone turnover. Study II is a methodologic-, multicenter study investigating the precision of low-dose CT-based implant motion analysis (CTMA). We determined the precision of CTMA by repeated measures and found it to be high. In study III we examined the long-term results of the CFP stem. The cohort from a previous, prospective study on the CFP stem was followed up for a minimum of 8 years with DXA and RSA. Periprosthetic BMD was not restored, and further bone loss was seen in the proximal part of the femur; however, the stems appeared stable on RSA. In study IV, we looked at the reliability, agreement, and precision of periprosthetic F-PET. F-PET investigations from study I were analyzed twice by two independent observers, at least 3 weeks apart. Reliability was excellent, agreement was high, and precision was moderate between and within observers. In conclusion, denosumab prevents periprosthetic BMD loss and the CFP stem shows continuous periprosthetic bone loss 8 years after surgery, but the implants remain stable. In addition, this thesis shows that CTMA is a precise method and a viable alternative to RSA. Finally, it demonstrates that periprosthetic F-PET is a reliable method with high inter- and intraobserver agreement.
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| 68. |
- Olsson, Erik J, et al.
(författare)
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What Price Equality? The Academic Cost of Government Supervised Gender Mainstreaming at Swedish Universities
- 2020
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Ingår i: Societies. - : MDPI AG. - 2075-4698. ; 10:4
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Tidskriftsartikel (refereegranskat)abstract
- This article is focused on gender mainstreaming at Swedish universities in the period from 2016-2019. Our research questions are: (a) In what form was gender mainstreaming introduced and did the form itself affect scholar's academic rights? (b) Was the process in question compatible with international standards of institutional autonomy? (c) What effect did gender mainstreaming have on scholars' ability to exercise their academic rights in accordance with international standards? Using the UNESCO Recommendations Concerning the Status of Higher-education Teaching Personnel (1997) as our international standard, we conclude that gender mainstreaming was introduced as a form of identity politics though government action and de facto supervision; that the latter was problematic from the perspective of institutional autonomy; that the choice of gender studies as a preferred scientific framework for university policy had a chilling effect on inquiry and free speech in other areas of research; and, finally, that gender mainstreaming led to violations of some scholars' individual rights. The findings may be taken into account in evaluations of the outcome of gender mainstreaming at Swedish universities, all things considered.
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| 69. |
- Portinson Hylander, Jens, et al.
(författare)
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Hållbart deltagande : kan medborgares involvering öka legitimiteten för kontroversiella åtgärder i transportsystem?
- 2024
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Ingår i: Sammanställning av referat från Transportforum 2024. - Linköping : Statens väg- och transportforskningsinstitut. ; , s. 174-175
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- En växande insikt är att de främsta hindren för en hållbar omställning är sociala och politiska, inte tekniska eller ekonomiska. En central aspekt för att implementera nya hållbara sociala praktiker och tekniska system, är att bygga och upprätthålla deras legitimitet. Ju kraftigare åtgärder för att minska växthusgasutsläpp, desto kraftigare blir reaktionerna. Studien utförs som en jämförande kvalitativ fallstudie, där tre städer som har implementerat (potentiellt) kontroversiella åtgärder utforskas: Helsingborg i Sverige där införandet av en s.k. ’superbuss’ omfördelat utrymmet för bilar och buss på gatorna, Sandnes i Norge där ett centrumtorg med parkering har omvandlats till en kultur- och aktivitetszon, och Köpenhamn i Danmark där processer pågår för att drastiskt minska antalet parkeringsplatser i den medeltida stadskärnan.Studiens huvudsakliga data utgörs av intervjuer med individer som i olika roller har deltagit i planeringen av, besluten om, eller dialogerna om åtgärderna i de olika fallen. Två viktiga urvalskriterium för fallen är: 1) att de metoder och verktyg genom vilka deltagande och dialog med medborgare och andra intressenter har skett under planeringens gång har varit nyskapande i den kontext där de använts, och 2) att projektet i någon mån kan anses vara exempel på framgångsrikt genomförande av åtgärder. Syftet med detta urval är att dra lärdomar från framgång, och för att utforska om det finns något värdefullt i sig i innovativa grepp för medborgardeltagande. Baserat på en operationalisering av de teoretiska begreppen legitimitet, medborgardeltagande och processinnovation analyseras data för att identifiera lärdomar om faktorer som påverkar genomförandet av de kontroversiella åtgärderna. Preliminära resultat berör frågor som inkludering, representation, och rättvisa, men även maktfaktorer som fastighetsägande.
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| 70. |
- Regula, Naresh, et al.
(författare)
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Carbon Flux as a Measure of Prostate Cancer Aggressiveness : [11C]-Acetate PET/CT
- 2020
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Ingår i: International Journal of Medical Sciences. - : Ivyspring International Publisher. - 1449-1907. ; 17:2, s. 214-223
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Dynamic [11C]-acetate positron emission tomography (PET) can be used to study tissue perfusion and carbon flux simultaneously. In this study, the feasibility of the quantification of prostate cancer aggressiveness using parametric methods assessing [11C]-acetate kinetics was investigated in prostate cancer subjects. The underlying uptake mechanism correlated with [11C]-acetate influx and efflux measured in real-time in vitro in cell culture.Methods: Twenty-one patients with newly diagnosed low-to-moderate risk prostate cancer underwent magnetic resonance imaging (MRI) and dynamic [11C]-acetate PET/CT examinations of the pelvis. Parametric images of K1 (extraction × perfusion), k2 (oxidative metabolism) and VT (=K1/k2, anabolic metabolism defined as carbon retention) were constructed using a one-tissue compartment model with an arterial input function derived from pelvic arteries. Regions of interest (ROIs) of the largest cancer lesion in each patient and normal prostate tissue were drawn using information from MRI (T2 and DWI images), biopsy results, and post-surgical histopathology of whole prostate sections (n=7). In vitro kinetics of [11C]-acetate were studied on DU145 andPC3 cell lines using LigandTracer® White equipment for the measurement of the radioactivity uptake in real-time at 37°C.Results: Mean prostate specific antigen (PSA) was 8.33±3.92 ng/mL and median Gleason Sum 6 (range 5-7). K1,VT and standardized uptake values (SUVs) were significantly higher in cancerous prostate tissues compared to normal ones for all patients (p<0.001), while k2 was not (p=0.26). PSA values correlated to early SUVs (r=0.50,p=0.02) and K1 (r=0.48, p=0.03). Early and late SUVs correlated to VT (r>0.76, p<0.001) and K1 (r>0.64,p<0.005). In vitro studies demonstrated higher extraction and retention (p<0.01) of [11C]-acetate in the more aggressive PC3 cells.Conclusion: Parametric images could be used to visualize the [11C]-acetate kinetics of the prostate cancer exhibiting elevated extraction associated with the cancer aggressiveness. The influx rate of [11C]-acetate studied in cell culture also showed dependence on the cancer aggressiveness associated with elevated lipogenesis. Dynamic [11C]-acetate/PET demonstrated potential for prostate cancer aggressiveness estimation using parametric-based K1 and VT values.
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