| 1. |
|
|
| 2. |
|
|
| 3. |
- Hamill, James J., et al.
(författare)
-
Accuracy of PET Partial Volume Correction in Tracer Uptake Measurements with Six Isotopes
- 2016
-
Ingår i: 2016 Ieee Nuclear Science Symposium, Medical Imaging Conference And Room-Temperature Semiconductor Detector Workshop (Nss/Mic/Rtsd). - 9781509016426 - 9781509016433
-
Konferensbidrag (refereegranskat)abstract
- Soderlund et al recently published a sphere phantom study with six PET tracers, concluding that image quality was good but tracer concentration measurements based on mean uptake (MEAN) were strongly affected by partial volume errors (PVE). In this work we ask if a previously published PVE correction method (CORR, described in 2002 by Hickeson and colleagues) is more accurate. The CORR method may be appropriate in applications like lung-nodule PET/CT when isolated hot structures, perhaps lung nodules, sit in a region of approximately uniform background, and the object's volume (V) is known from CT. A volume of interest in the PET image (VOI) is defined around the object. Background is estimated from voids adjacent to the VOI. Tracer concentration in Bq/ml is set to the background-corrected VOI total, divided by V. Hot spheres had diameters 10, 13, 17 and 22 mm. Cold spheres had diameters 28 and 37 mm. The phantom was filled with positron-emitting F-18, C-11, Zr-89, I-124, Ga-68 and Y-90 activity with a sphere to background ratio of approximately 4:1. TOF PET data from a Siemens mCT PET/CT scanner were reconstructed with the TOF-PSF method. Using the MEAN and CORR methods, we calculated contrast recovery (CR), defined by NEMA NU 2-2007, for hot and cold spheres. In hot spheres 13 mm or more in diameter, CR based on CORR was between 90% and 10.5% for, all but one measurement with F-18, C-11, Zr-89, I-124 Ga-68. In the 10 mm sphere, CR was 82% on average. In these spheres and these isotopes, CR based on MEAN varied between 0.3 and 0.8. In the cold spheres, recovery based on CORR was between 0.7 and 1.0 for these isotopes. Reconstructions of Y-90 were less accurate. In conclusion, CORR improved contrast recovery measurements, compared to MEAN.
|
|
| 4. |
- Marchesseau, Stephanie, et al.
(författare)
-
Hybrid PET/CT and PET/MRI imaging of vulnerable coronary plaque and myocardial scar tissue in acute myocardial infarction
- 2018
-
Ingår i: Journal of Nuclear Cardiology. - : SPRINGER. - 1071-3581 .- 1532-6551. ; 25:6, s. 2001-2011
-
Tidskriftsartikel (refereegranskat)abstract
- BackgroundFollowing an acute coronary syndrome, combined CT and PET with F-18-NaF can identify coronary atherosclerotic plaques that have ruptured or eroded. However, the processes behind F-18-NaF uptake in vulnerable plaques remain unclear. Methods and ResultsTen patients with STEMI were scanned after F-18-NaF injection, for 75minutes in a Siemens PET/MR scanner using delayed enhancement (LGE). They were then scanned in a Siemens PET/CT scanner for 10minutes. Tissue-to-background ratio (TBR) was compared between the culprit lesion in the IRA and remote non-culprit lesions in an effort to independently validate prior studies. Additionally, we performed a proof-of-principle study comparing TBR in scar tissue and remote myocardium using LGE images and PET/MR or PET/CT data. From the 33 coronary lesions detected on PET/CT, TBRs for culprit lesions were higher than for non-culprit lesions (TBR=2.110.45 vs 1.46 +/- 0.48; P<0.001). Interestingly, the TBR measured on the PET/CT was higher for infarcted myocardium than for remote myocardium (TBR=0.81 +/- 0.10 vs 0.71 +/- 0.05; P=0.003). These results were confirmed using the PET/MR data (TBR=0.81 +/- 0.10 for scar, TBR=0.71 +/- 0.06 for healthy myocardium, P=0.03). Conclusions We confirmed the potential of F-18-NaF PET/CT imaging to detect vulnerable coronary lesions. Moreover, we demonstrated proof-of-principle that F-18-NaF concurrently detects myocardial scar tissue.
|
|
| 5. |
- Moberg, Christina, et al.
(författare)
-
De unga gör helt rätt när de stämmer staten : 1 620 forskare och lärare i forskarvärlden: Vi ställer oss bakom Auroras klimatkrav
- 2022
-
Ingår i: Aftonbladet. - : Aftonbladet. ; :2022-12-07
-
Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Vi, 1 620 forskare samt lärare vid universitet och högskolor, är eniga med de unga bakom Auroramålet: De drabbas och riskerar att drabbas allvarligt av klimatkrisen under sin livstid. De klimatåtgärder vi vidtar i närtid avgör deras framtid. Sverige måste ta ansvar och göra sin rättvisa andel av det globala klimatarbetet. I strid med Parisavtalet ökar utsläppen av växthusgaser i en takt som gör att 1,5-gradersmålet kan överskridas om några år. De globala effekterna blir allt mer synliga med ständiga temperaturrekord, smältande isar, havshöjning och extremväder som torka, förödande bränder och skyfall med enorma översvämningar, som i Pakistan nyligen. Försörjningen av befolkningen utsätts för allvarliga hot i många länder.Minskningen av den biologiska mångfalden är extrem. Klimatkrisen är enligt WHO det största hotet mot människors hälsa i hela världen och barn utgör en särskilt sårbar grupp. Med Sveriges nordliga läge sker uppvärmningen här dubbelt så fort som det globala genomsnittet. Det förskjuter utbredningsområden för växtlighet och sjukdomsbärande insekter och ökar förekomsten av extremväder såsom värmeböljor, skogsbränder och översvämningar samt av många olika sorters infektioner och allergier. När extremväder ökar, ökar även stressen och risken för mental ohälsa. Värmeböljor ökar risken för sjukdom och död hos sårbara grupper som äldre, små barn och personer med kroniska sjukdomar. De negativa effekterna på hälsan kommer att öka i takt med klimatkrisen och barn riskerar att drabbas av ackumulerade negativa hälsoeffekter under hela sina liv. Redan i dag är mer än hälften av unga mellan 12 och 18 år i Sverige ganska eller mycket oroliga för klimat och miljö. Detta är förståeligt när våra beslutsfattare inte gör vad som krävs.Den juridiska och moraliska grunden för arbetet mot klimatförändringarna är att varje land måste göra sin rättvisa andel av det globala klimatarbetet. Centralt i det internationella klimatramverket är att rika länder med höga historiska utsläpp, däribland Sverige, måste gå före resten av världen. Dessa länder måste också bidra till att finansiera klimatomställningen i länderna i det Globala Syd, som är minst ansvariga för klimatkrisen men drabbas hårdast. Denna rättviseprincip är tydlig i Parisavtalet och var en het diskussionsfråga under COP27 i Sharm el-Sheikh, men lyser med sin frånvaro i det svenska klimatarbetet. Sverige har satt mål för att minska sina utsläpp. Men de är helt otillräckliga: minskningstakten är för låg och målen tillåter samtidigt att åtgärder skjuts på framtiden. Dessutom exkluderas merparten av Sveriges utsläpp från de svenska nationella utsläppsmålen; bland annat utelämnas utsläpp som svensk konsumtion orsakar utanför Sveriges gränser, utsläpp från utrikes transporter och utsläpp från markanvändning och skogsbruk, exempelvis utsläpp från förbränning av biobränslen eller utsläpp från dikade våtmarker (Prop. 2016/17:146 s.25-28).Sverige saknar dessutom ett eget mål för att öka upptaget av växthusgaser genom utökat skydd och restaurering av ekosystem, något som krävs för att begränsa de värsta konsekvenserna av klimatkrisen (IPCC s.32). Trots dessa låga ambitioner misslyckas Sverige med att nå sina utsläppsmål, konstaterar både Klimatpolitiska rådet och Naturvårdsverket. En klimatpolitik i linje med Parisavtalet kräver både att alla typer av växthusgasutsläpp minskar samtidigt som – inte i stället för – upptaget av växthusgaser maximeras: i dag misslyckas Sverige på bägge fronter.Slutsatsen är tydlig. Sverige vidtar inte de åtgärder som krävs för att skydda barns och ungdomars rättigheter enligt Europakonventionen till skydd för de mänskliga rättigheterna. Detta medför allvarliga risker för liv och hälsa för unga generationer, människor i andra länder och särskilt utsatta grupper. Detta kan inte fortsätta. Därför ställer vi oss bakom Auroras krav att Sverige börjar göra sin rättvisa andel och omedelbart sätter igång ett omfattande och långtgående klimatarbete som vilar på vetenskaplig grund och sätter rättvisa i centrum.
|
|
| 6. |
- Sjöholm, Therese, et al.
(författare)
-
A whole-body diffusion MRI normal atlas : development, evaluation and initial use
- 2023
-
Ingår i: Cancer Imaging. - : BioMed Central (BMC). - 1740-5025 .- 1470-7330. ; 23:1
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Statistical atlases can provide population-based descriptions of healthy volunteers and/or patients and can be used for region- and voxel-based analysis. This work aims to develop whole-body diffusion atlases of healthy volunteers scanned at 1.5T and 3T. Further aims include evaluating the atlases by establishing whole-body Apparent Diffusion Coefficient (ADC) values of healthy tissues and including healthy tissue deviations in an automated tumour segmentation task.Methods: Multi-station whole-body Diffusion Weighted Imaging (DWI) and water-fat Magnetic Resonance Imaging (MRI) of healthy volunteers (n = 45) were acquired at 1.5T (n = 38) and/or 3T (n = 29), with test-retest imaging for five subjects per scanner. Using deformable image registration, whole-body MRI data was registered and composed into normal atlases. Healthy tissue ADCmean was manually measured for ten tissues, with test-retest percentage Repeatability Coefficient (%RC), and effect of age, sex and scanner assessed. Voxel-wise whole-body analyses using the normal atlases were studied with ADC correlation analyses and an automated tumour segmentation task. For the latter, lymphoma patient MRI scans (n = 40) with and without information about healthy tissue deviations were entered into a 3D U-Net architecture.Results: Sex- and Body Mass Index (BMI)-stratified whole-body high b-value DWI and ADC normal atlases were created at 1.5T and 3T. %RC of healthy tissue ADCmean varied depending on tissue assessed (4-48% at 1.5T, 6-70% at 3T). Scanner differences in ADCmean were visualised in Bland-Altman analyses of dually scanned subjects. Sex differences were measurable for liver, muscle and bone at 1.5T, and muscle at 3T. Volume of Interest (VOI)-based multiple linear regression, and voxel-based correlations in normal atlas space, showed that age and ADC were negatively associated for liver and bone at 1.5T, and positively associated with brain tissue at 1.5T and 3T. Adding voxel-wise information about healthy tissue deviations in an automated tumour segmentation task gave numerical improvements in the segmentation metrics Dice score, sensitivity and precision.Conclusions: Whole-body DWI and ADC normal atlases were created at 1.5T and 3T, and applied in whole-body voxel-wise analyses.
|
|
| 7. |
- Sjöholm, Therese, et al.
(författare)
-
A whole-body FDG PET/MR atlas for multiparametric voxel-based analysis
- 2019
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9
-
Tidskriftsartikel (refereegranskat)abstract
- Quantitative multiparametric imaging is a potential key application for Positron Emission Tomography/Magnetic Resonance (PET/MR) hybrid imaging. To enable objective and automatic voxel-based multiparametric analysis in whole-body applications, the purpose of this study was to develop a multimodality whole-body atlas of functional 18F-fluorodeoxyglucose (FDG) PET and anatomical fat-water MR data of adults. Image registration was used to transform PET/MR images of healthy control subjects into male and female reference spaces, producing a fat-water MR, local tissue volume and FDG PET whole-body normal atlas consisting of 12 male (66.6 +/- 6.3 years) and 15 female (69.5 +/- 3.6 years) subjects. Manual segmentations of tissues and organs in the male and female reference spaces confirmed that the atlas contained adequate physiological and anatomical values. The atlas was applied in two anomaly detection tasks as proof of concept. The first task automatically detected anomalies in two subjects with suspected malignant disease using FDG data. The second task successfully detected abnormal liver fat infiltration in one subject using fat fraction data.
|
|
| 8. |
- Sjöholm, Therese
(författare)
-
Cancer imaging and image analysis methods in whole-body MRI and PET/MRI
- 2023
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Diagnostic medical imaging techniques such as magnetic resonance imaging (MRI) and positron emission tomography (PET) can provide structural and functional assessments of the whole body. This has great value for potentially systemic diseases such as cancer. To take advantage of the enormous amount of data provided by current imaging systems, improvements in whole-body imaging protocols and advancements in image analysis methods are however needed. This thesis aims to develop advanced imaging and image analysis methods for the purpose of tumour characterisation in MRI and combined PET/MRI whole-body image datasets. Early prediction of progression free survival (PFS) and overall survival (OS) in patients with relapsed/refractory (r/r) large B-cell lymphoma (LBCL) undergoing chimeric antigen receptor (CAR) T-cell therapy was assessed using whole-body PET/MRI pre- and post-therapy. Reference standard manual segmentations of tumours and non-malignant lymphoid tissue were used, and an extended set of semi-quantitative and quantitative PET/MRI metrics was extracted. Predictive PET/MRI metrics included the metabolic tumour volume (MTV), tumour apparent diffusion coefficient (ADC) and 18F-fluorodeoxyglucose (FDG) uptake in non-malignant bone marrow. To enable automated image analysis, deformable image registration was used to create multiparametric normal atlases of healthy volunteers examined with whole-body FDG PET, diffusion weighted imaging (DWI) MRI and water-fat MRI. To improve the geometric accuracy of DWI in the normal atlas, the reverse polarity gradient (RPG) distortion correction method was evaluated. RPG increased the geometrical alignment between DWI and structural images acquired in the same scan session, with little effect on healthy tissue ADC. It was further shown that healthy tissue assessments in atlas space was possible, with the normal atlas employed to study voxel-wise correlations between ADC and age across the whole body, confirming results from a manual segmentation approach. As proof of concept, a probabilistic atlas based approach was successfully used for segmentation of suspected malignant disease in FDG PET data and detection of liver fat infiltration in fat fraction (FF) MRI data. Lastly, using a cohort of r/r LBCL patients, statistical deviations between patient and normal atlas DWI data included as input in a deep learning based model, improved its performance for automated tumour segmentation.
|
|
| 9. |
- Sjöholm, Therese, et al.
(författare)
-
Improved geometric accuracy of whole body diffusion-weighted imaging at 1.5T and 3T using reverse polarity gradients
- 2022
-
Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 12
-
Tidskriftsartikel (refereegranskat)abstract
- Whole body diffusion-weighted imaging (WB-DWI) is increasingly used in oncological applications, but suffers from misalignments due to susceptibility-induced geometric distortion. As such, DWI and structural images acquired in the same scan session are not geometrically aligned, leading to difficulties in e.g. lesion detection and segmentation. In this work we assess the performance of the reverse polarity gradient (RPG) method for correction of WB-DWI geometric distortion. Multi-station DWI and structural magnetic resonance imaging (MRI) data of healthy controls were acquired at 1.5T (n = 20) and 3T (n = 20). DWI data was distortion corrected using the RPG method based on b = 0 s/mm(2) (b0) and b = 50 s/mm(2) (b50) DWI acquisitions. Mutual information (MI) between low b-value DWI and structural data increased with distortion correction (P < 0.05), while improvements in region of interest (ROI) based similarity metrics, comparing the position of incidental findings on DWI and structural data, were location dependent. Small numerical differences between non-corrected and distortion corrected apparent diffusion coefficient (ADC) values were measured. Visually, the distortion correction improved spine alignment at station borders, but introduced registration-based artefacts mainly for the spleen and kidneys. Overall, the RPG distortion correction gave an improved geometric accuracy for WB-DWI data acquired at 1.5T and 3T. The b0- and b50-based distortion corrections had a very similar performance.
|
|
| 10. |
- Sjöholm, Therese, et al.
(författare)
-
Whole body FDG PET/MR for progression free and overall survival prediction in patients with relapsed/refractory large B-cell lymphomas undergoing CAR T-cell therapy
- 2022
-
Ingår i: Cancer Imaging. - : BioMed Central (BMC). - 1740-5025 .- 1470-7330. ; 22:1
-
Tidskriftsartikel (refereegranskat)abstract
- Background: To find semi-quantitative and quantitative Positron Emission Tomography/Magnetic Resonance (PET/MR) imaging metrics of both tumor and non-malignant lymphoid tissue (bone marrow and spleen) for Progression Free Survival (PFS) and Overall Survival (OS) prediction in patients with relapsed/refractory (r/r) large B-cell lymphoma (LBCL) undergoing Chimeric Antigen Receptor (CAR) T-cell therapy.Methods: A single-center prospective study of 16 r/r LBCL patients undergoing CD19-targeted CAR T-cell therapy. Whole body 18F-fluorodeoxyglucose (FDG) PET/MR imaging pre-therapy and 3 weeks post-therapy were followed by manual segmentation of tumors and lymphoid tissues. Semi-quantitative and quantitative metrics were extracted, and the metric-wise rate of change (Δ) between post-therapy and pre-therapy calculated. Tumor metrics included maximum Standardized Uptake Value (SUVmax), mean SUV (SUVmean), Metabolic Tumor Volume (MTV), Tumor Lesion Glycolysis (TLG), structural volume (V), total structural tumor burden (Vtotal) and mean Apparent Diffusion Coefficient (ADCmean). For lymphoid tissues, metrics extracted were SUVmean, mean Fat Fraction (FFmean) and ADCmean for bone marrow, and SUVmean, V and ADCmean for spleen. Univariate Cox regression analysis tested the relationship between extracted metrics and PFS and OS. Survival curves were produced using Kaplan-Meier analysis and compared using the log-rank test, with the median used for dichotomization. Uncorrected p-values < 0.05 were considered statistically significant. Correction for multiple comparisons was performed, with a False Discovery Rate (FDR) < 0.05 considered statistically significant.Results: Pre-therapy (p < 0.05, FDR < 0.05) and Δ (p < 0.05, FDR > 0.05) total tumor burden structural and metabolic metrics were associated with PFS and/or OS. According to Kaplan-Meier analysis, a longer PFS was reached for patients with pre-therapy MTV ≤ 39.5 ml, ΔMTV≤1.35 and ΔTLG≤1.35. ΔSUVmax was associated with PFS (p < 0.05, FDR > 0.05), while ΔADCmean was associated with both PFS and OS (p < 0.05, FDR > 0.05). ΔADCmean > 0.92 gave longer PFS and OS in the Kaplan-Meier analysis. Pre-therapy bone marrow SUVmean was associated with PFS (p < 0.05, FDR < 0.05) and OS (p < 0.05, FDR > 0.05). For bone marrow FDG uptake, patient stratification was possible pre-therapy (SUVmean ≤ 1.8).Conclusions: MTV, tumor ADCmean and FDG uptake in bone marrow unaffected by tumor infiltration are possible PET/MR parameters for prediction of PFS and OS in r/r LBCL treated with CAR T-cells.
|
|
