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Danfors, Torsten
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Publications (10 of 28) Show all publications
Roodakker, K. R., Alhuseinalkhudhur, A., Al-Jaff, M., Georganaki, M., Zetterling, M., Berntsson, S. G., . . . Smits, A. (2019). Region-by-region analysis of PET, MRI, and histology in en bloc-resected oligodendrogliomas reveals intra-tumoral heterogeneity. European Journal of Nuclear Medicine and Molecular Imaging, 46(3), 569-579
Open this publication in new window or tab >>Region-by-region analysis of PET, MRI, and histology in en bloc-resected oligodendrogliomas reveals intra-tumoral heterogeneity
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2019 (English)In: European Journal of Nuclear Medicine and Molecular Imaging, ISSN 1619-7070, E-ISSN 1619-7089, Vol. 46, no 3, p. 569-579Article in journal (Refereed) Published
National Category
Radiology, Nuclear Medicine and Medical Imaging
Research subject
Computerized Image Processing
Identifiers
urn:nbn:se:uu:diva-356591 (URN)10.1007/s00259-018-4107-z (DOI)000457151600005 ()30109401 (PubMedID)
Funder
Erik, Karin och Gösta Selanders Foundation
Available from: 2018-08-14 Created: 2018-08-08 Last updated: 2019-04-06Bibliographically approved
Jonasson, M., Langaas, G., Appel, L., Danfors, T., Fazio, P., Lubberink, M. & Varrone, A. (2018). Blood Flow Dependence of Early [C-11]PE2I and [F-18]FE-PE2I PET SUVR Measurements Used In the Differential Diagnosis of Parkinsonian Disorders. Paper presented at 31st Annual Congress of the European-Association-of-Nuclear-Medicine (EANM), OCT 13-17, 2018, Dusseldorf, GERMANY. European Journal of Nuclear Medicine and Molecular Imaging, 45, S303-S304
Open this publication in new window or tab >>Blood Flow Dependence of Early [C-11]PE2I and [F-18]FE-PE2I PET SUVR Measurements Used In the Differential Diagnosis of Parkinsonian Disorders
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2018 (English)In: European Journal of Nuclear Medicine and Molecular Imaging, ISSN 1619-7070, E-ISSN 1619-7089, Vol. 45, p. S303-S304Article in journal, Meeting abstract (Other academic) Published
Place, publisher, year, edition, pages
Springer, 2018
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:uu:diva-372963 (URN)000449266202217 ()
Conference
31st Annual Congress of the European-Association-of-Nuclear-Medicine (EANM), OCT 13-17, 2018, Dusseldorf, GERMANY
Available from: 2019-01-21 Created: 2019-01-21 Last updated: 2019-01-21Bibliographically approved
Lubberink, M., Widström, C., Jonasson, M., Appel, L., Fällmar, D., Nyholm, D., . . . Danfors, T. (2018). Differential diagnosis of patients with parkinsonian syndrome using multilinear regression to disease-specific C-11-PE2I-PET templates and classification tree learning. Paper presented at 31st Annual Congress of the European-Association-of-Nuclear-Medicine (EANM), OCT 13-17, 2018, Dusseldorf, GERMANY. European Journal of Nuclear Medicine and Molecular Imaging, 45, S409-S409
Open this publication in new window or tab >>Differential diagnosis of patients with parkinsonian syndrome using multilinear regression to disease-specific C-11-PE2I-PET templates and classification tree learning
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2018 (English)In: European Journal of Nuclear Medicine and Molecular Imaging, ISSN 1619-7070, E-ISSN 1619-7089, Vol. 45, p. S409-S409Article in journal, Meeting abstract (Other academic) Published
Place, publisher, year, edition, pages
Springer, 2018
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:uu:diva-372967 (URN)000449266204001 ()
Conference
31st Annual Congress of the European-Association-of-Nuclear-Medicine (EANM), OCT 13-17, 2018, Dusseldorf, GERMANY
Available from: 2019-01-10 Created: 2019-01-10 Last updated: 2019-01-10Bibliographically approved
Lindström, E., Sundin, A., Trampal, C., Lindsjö, L., Ilan, E., Danfors, T., . . . Lubberink, M. (2018). Evaluation of penalized likelihood estimation reconstruction on a digital time-of-flight PET/CT scanner for 18F-FDG whole-body examinations. Journal of Nuclear Medicine, 59(7), 1152-1158
Open this publication in new window or tab >>Evaluation of penalized likelihood estimation reconstruction on a digital time-of-flight PET/CT scanner for 18F-FDG whole-body examinations
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2018 (English)In: Journal of Nuclear Medicine, ISSN 0161-5505, E-ISSN 1535-5667, Vol. 59, no 7, p. 1152-1158Article in journal (Refereed) Published
Abstract [en]

The resolution and quantitative accuracy of PET are highly influenced by the reconstruction method. Penalized-likelihood estimation algorithms allow for fully convergent iterative reconstruction, generating a higher image contrast than ordered-subsets expectation maximization (OSEM) while limiting noise. In this study, a type of penalized reconstruction known as block-sequential regularized expectation maximization (BSREM) was compared with time-of-flight OSEM (TOF OSEM). Various strengths of noise penalization factor β were tested along with various acquisition durations and transaxial fields of view (FOVs) with the aim of evaluating the performance and clinical use of BSREM for 18F-FDG PET/CT, both quantitatively and in a qualitative visual evaluation. Methods: Eleven clinical whole-body 18F-FDG PET/CT examinations acquired on a digital TOF PET/CT scanner were included. The data were reconstructed using BSREM with point-spread function recovery and β-factors of 133, 267, 400, and 533—and using TOF OSEM with point-spread function—for various acquisition times per bed position and various FOVs. Noise level, signal-to-noise ratio (SNR), signal-to-background ratio (SBR), and SUV were analyzed. A masked evaluation of visual image quality, rating several aspects, was performed by 2 nuclear medicine physicians to complement the analysis. Results: The lowest levels of noise were reached with the highest β-factor, resulting in the highest SNR, which in turn resulted in the lowest SBR. A β-factor of 400 gave noise equivalent to TOF OSEM but produced a significant increase in SUVmax (11%), SNR (22%), and SBR (12%). BSREM with a β-factor of 533 at a decreased acquisition duration (2 min/bed position) was comparable to TOF OSEM at a full acquisition duration (3 min/bed position). Reconstructed FOV had an impact on BSREM outcome measures; SNR increased and SBR decreased when FOV was shifted from 70 to 50 cm. The evaluation of visual image quality resulted in similar scores for reconstructions, although a β-factor of 400 obtained the highest mean whereas a β-factor of 267 was ranked best in overall image quality, contrast, sharpness, and tumor detectability. Conclusion: In comparison with TOF OSEM, penalized BSREM reconstruction resulted in an increased tumor SUVmax and an improved SNR and SBR at a matched level of noise. BSREM allowed for a shorter acquisition than TOF OSEM, with equal image quality.

Keywords
FDG, Image Reconstruction, Molecular Imaging, PET/CT, block-sequential regularized expectation maximization, image reconstruction, penalization factor
National Category
Medical and Health Sciences Medical Image Processing
Identifiers
urn:nbn:se:uu:diva-343272 (URN)10.2967/jnumed.117.200790 (DOI)000437237200037 ()29449445 (PubMedID)
Available from: 2018-02-26 Created: 2018-02-26 Last updated: 2018-09-18Bibliographically approved
Lindström, E., Oddstig, J., Danfors, T., Lindsjö, L., Hansson, O. & Lubberink, M. (2018). Flutemetamol and FDG Brain-PET Image Reconstruction Methods Affect Software-Aided Diagnosis in Patients with Neurodegenerative Diseases. Paper presented at 31st Annual Congress of the European-Association-of-Nuclear-Medicine (EANM), OCT 13-17, 2018, Dusseldorf, GERMANY. European Journal of Nuclear Medicine and Molecular Imaging, 45, S305-S305
Open this publication in new window or tab >>Flutemetamol and FDG Brain-PET Image Reconstruction Methods Affect Software-Aided Diagnosis in Patients with Neurodegenerative Diseases
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2018 (English)In: European Journal of Nuclear Medicine and Molecular Imaging, ISSN 1619-7070, E-ISSN 1619-7089, Vol. 45, p. S305-S305Article in journal, Meeting abstract (Other academic) Published
Place, publisher, year, edition, pages
Springer, 2018
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:uu:diva-372965 (URN)000449266202220 ()
Conference
31st Annual Congress of the European-Association-of-Nuclear-Medicine (EANM), OCT 13-17, 2018, Dusseldorf, GERMANY
Available from: 2019-01-14 Created: 2019-01-14 Last updated: 2019-01-14Bibliographically approved
Fällmar, D., Lilja, J., Danfors, T., Kilander, L., Iyer, V., Lubberink, M., . . . Sörensen, J. (2018). Z-score maps from low-dose 18F-FDG PET of the brain in neurodegenerative dementia.. American Journal of Nuclear Medicine and Molecular Imaging, 8(4), 239-246
Open this publication in new window or tab >>Z-score maps from low-dose 18F-FDG PET of the brain in neurodegenerative dementia.
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2018 (English)In: American Journal of Nuclear Medicine and Molecular Imaging, ISSN 2160-8407, Vol. 8, no 4, p. 239-246Article in journal (Refereed) Published
Abstract [en]

Neuroimaging is a central part of diagnostic work-up of patients with suspected neurodegenerative disease. FDG-PET can reveal pathological changes earlier and more reliably than morphological imaging. Diagnostic accuracy can be improved by constructing 3D SSP Z-score maps, showing patterns of significant deficits. During FDG-PET, the subject receives a moderate but not insignificant dose of ionizing radiation, and a dose reduction with retained image quality is desirable. With lower dose, repeated examinations can become a useful tool for monitoring disease progress and potential effects of disease-modifying interventions. The aim of this study was to evaluate Z-maps created from low-dose and normal-dose FDG-PET of the brain, with quantitative and qualitative methods. Nine patients with neurodegenerative disorders were prospectively enrolled and nine age-matched controls were recruited through advertising. All subjects (n=18) underwent two FDG-PET scans on separate occasions; a routine and a low-dose scan. The routine dosage of FDG was 3 MBq/kg, and low dosage was 0.75 MBq/kg. 3D-SSP images showing Z-scores of < -1.96 were created from 10-minute summations. The study was comprised of a quantitative part comparing the Z-scores, and a qualitative part where experienced nuclear medicine specialists visually assessed the images. Regarding the quantitative part, Bland-Altman analysis showed a slight constant bias (0.206). Regarding qualitative discrimination between patients and controls, the performance between normal- and low-dose were equal, both showing 72% sensitivity, 83% specificity and 78% accuracy. In this study, visual assessment of 3D-SSP Z-score maps from low-dose FDG-PET provided diagnostic information highly comparable to normal-dose, with minor quantitative discrepancies.

Keywords
FDG, PET, methodology, neurodegeneration, neuroimaging, radiation
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:uu:diva-362198 (URN)000444491000001 ()30245916 (PubMedID)
Available from: 2018-10-02 Created: 2018-10-02 Last updated: 2018-11-15Bibliographically approved
Fällmar, D., Haller, S., Lilja, J., Danfors, T., Kilander, L., Tolboom, N., . . . Larsson, E.-M. (2017). Arterial spin labeling-based Z-maps have high specificity and positive predictive value for neurodegenerative dementia compared to FDG-PET.. European Radiology, 27(10), 4237-4246
Open this publication in new window or tab >>Arterial spin labeling-based Z-maps have high specificity and positive predictive value for neurodegenerative dementia compared to FDG-PET.
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2017 (English)In: European Radiology, ISSN 0938-7994, E-ISSN 1432-1084, Vol. 27, no 10, p. 4237-4246Article in journal (Refereed) Published
Abstract [en]

OBJECTIVE: Cerebral perfusion analysis based on arterial spin labeling (ASL) MRI has been proposed as an alternative to FDG-PET in patients with neurodegenerative disease. Z-maps show normal distribution values relating an image to a database of controls. They are routinely used for FDG-PET to demonstrate disease-specific patterns of hypometabolism at the individual level. This study aimed to compare the performance of Z-maps based on ASL to FDG-PET.

METHODS: Data were combined from two separate sites, each cohort consisting of patients with Alzheimer's disease (n = 18 + 7), frontotemporal dementia (n = 12 + 8) and controls (n = 9 + 29). Subjects underwent pseudocontinuous ASL and FDG-PET. Z-maps were created for each subject and modality. Four experienced physicians visually assessed the 166 Z-maps in random order, blinded to modality and diagnosis.

RESULTS: Discrimination of patients versus controls using ASL-based Z-maps yielded high specificity (84%) and positive predictive value (80%), but significantly lower sensitivity compared to FDG-PET-based Z-maps (53% vs. 96%, p < 0.001). Among true-positive cases, correct diagnoses were made in 76% (ASL) and 84% (FDG-PET) (p = 0.168).

CONCLUSION: ASL-based Z-maps can be used for visual assessment of neurodegenerative dementia with high specificity and positive predictive value, but with inferior sensitivity compared to FDG-PET.

KEY POINTS: • ASL-based Z-maps yielded high specificity and positive predictive value in neurodegenerative dementia. • ASL-based Z-maps had significantly lower sensitivity compared to FDG-PET-based Z-maps. • FDG-PET might be reserved for ASL-negative cases where clinical suspicion persists. • Findings were similar at two study sites.

Keywords
18F-FDG, Arterial spin labeling MRI, Dementia, Neurodegenerative, Visual assessment
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-319602 (URN)10.1007/s00330-017-4784-1 (DOI)000408952400027 ()28374078 (PubMedID)
Available from: 2017-04-06 Created: 2017-04-06 Last updated: 2018-01-03Bibliographically approved
Jonasson, M., Appel, L., Danfors, T., Nyholm, D., Askmark, H., Frick, A., . . . Lubberink, M. (2017). Development of a clinically feasible [11C]PE2I PET method for differential diagnosis of parkinsonism using reduced scan duration and automated reference region extraction.. American Journal of Nuclear Medicine and Molecular Imaging, 7(6), 263-274
Open this publication in new window or tab >>Development of a clinically feasible [11C]PE2I PET method for differential diagnosis of parkinsonism using reduced scan duration and automated reference region extraction.
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2017 (English)In: American Journal of Nuclear Medicine and Molecular Imaging, ISSN 2160-8407, Vol. 7, no 6, p. 263-274Article in journal (Refereed) Published
Abstract [en]

[11C]PE2I is a highly selective dopamine transporter PET ligand. Parametric images based on dynamic [11C]PE2I scans, showing dopamine transporter availability (BPND) and relative cerebral blood flow (R1), can be used in differential diagnosis of parkinsonism. This work aimed to investigate a shortened scan duration and automated generation of parametric images which are two prerequisites for routine clinical application. Twelve subjects with parkinsonism and seventeen healthy controls underwent 80 min dynamic [11C]PE2I PET scans. BPND and R1 images were generated using cerebellum reference region defined on a co-registered MRI, as well as a supervised cluster analysis (SVCA)-based reference. Initial 20, 30 and 40 min of the scans were extracted and images of standardized uptake value ratio (SUVR) and R1 were computed using MRI- and SVCA-based reference. Correlation was high between striatal 80 min MRI-based BPND and 40 min SVCA-based SUVR-1 (R2=0.95). High correlation was also found between R1 values in striatal and limbic regions (R2≥0.91) whereas correlation was moderate for cortical regions (R2=0.71). The results indicate that dynamic [11C]PE2I scans can be restricted to 40 min and that SVCA can be used for automatic extraction of a reference region. These outcomes will support routine applications of [11C]PE2I PET in clinical settings.

Keywords
PET, [11C]PE2I, parametric images, parkinsonism, supervised clustering
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-340790 (URN)000419593300003 ()29348981 (PubMedID)
Funder
Swedish Research CouncilSwedish Society for Medical Research (SSMF)
Available from: 2018-02-02 Created: 2018-02-02 Last updated: 2018-02-21Bibliographically approved
Lindström, E., Lindsjö, L., Ilan, E., Sundin, A., Sörensen, J., Danfors, T., . . . Lubberink, M. (2017). Optimisation of penalized likelihood estimation reconstruction (Q.Clear) on a digital time-of-flight PET-CT scanner for four different PET tracers. Paper presented at Annual Meeting of the Society-of-Nuclear-Medicine-and-Molecular-Imaging (SNMMI), JUN 10-14, 2017, Denver, CO. Journal of Nuclear Medicine, 58(S1), Article ID 1355.
Open this publication in new window or tab >>Optimisation of penalized likelihood estimation reconstruction (Q.Clear) on a digital time-of-flight PET-CT scanner for four different PET tracers
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2017 (English)In: Journal of Nuclear Medicine, ISSN 0161-5505, E-ISSN 1535-5667, Vol. 58, no S1, article id 1355Article in journal, Meeting abstract (Other academic) Published
Abstract [en]

Objectives: The penalized likelihood estimation reconstruction algorithm Q.Clear (GE Healthcare) allows for full convergence and edge preservation through a block sequential regularized expectation maximization technique. In this study the performance of Q.Clear was investigated for different penalization factors (β) with the aim to optimize its clinical use for four different tracers.

Methods: Q.Clear reconstructions with β values of 200, 400, 600 and 800 were compared to time-of-flight ordered subset expectation maximization (TF-OSEM) (3 iterations, 16 subsets and 5 mm Gaussian filter) with point spread function recovery. Clinical whole-body PET/CT (Discovery MI, GE Healthcare) scans with 68Ga-DOTATOC, 18F-FDG, 11C-acetate or 18F-fluoride were analyzed for level of noise in healthy liver tissue, signal to noise ratio (SNR), signal to background ratio (SBR) and maximum standardized uptake value (SUVmax). In addition, acquisition times per bed position and transaxial field of view (FOV) of the reconstructed images were varied. For each tracer, images from 10 patients were included, with a mean of 30 lesions per tracer. A spherical reference volume of interest (VOI) was placed in the liver and lesions were delineated employing a 41% threshold of the maximum voxel.

Results: The lowest levels of noise were reached with the highest beta factor resulting in the highest SNR, but this in turn gave the lowest SBR. Noise equivalence to OSEM was found with β 600 for 68Ga-DOTATOC, 18F-FDG and 18F-fluoride, and β 400 for 11C-acetate with a resulting significant increase of SUVmax (19.4%, 9.7%, 22.5% and 19.0% respectively) (P < 0.0001, paired t-test), SNR (22.1%, 22.6%, 9.5% and 33.6%) and SBR (19.5%, 11.7%, 21.3% and 18.5%) compared to OSEM. SNR decreased while SBR increased for all tracers when extending FOV from 500 to 700 mm, but only significantly for 18F-fluoride. Decreasing image acquisition time gave no statistical difference of SUVmax for 68Ga-DOTATOC, 18F-fluoride (2 to 1.5 min) for any reconstruction method nor for 11C-acetate (3 to 2 min) with β 蠅 400. Decreasing time for 18F-FDG (3 to 2 min) resulted in a change of optimal beta to β 800 in order to reach noise equivalence to OSEM along with maintaining a higher SNR than OSEM.

Conclusion: Images reconstructed by Q.Clear result in a tracer-dependent increase in tumour SUVmax values compared to OSEM at matched levels of noise, and an improved SNR. The optimal penalization factor, both in terms of noise-equivalence to OSEM and in terms of absolute SNR, is tracer dependent.

National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:uu:diva-333337 (URN)000404949906146 ()
Conference
Annual Meeting of the Society-of-Nuclear-Medicine-and-Molecular-Imaging (SNMMI), JUN 10-14, 2017, Denver, CO
Available from: 2017-11-15 Created: 2017-11-15 Last updated: 2017-11-15Bibliographically approved
Lubberink, M., Appel, L., Lindskog, K., Danfors, T., Sprycha, M., Daging, J., . . . Antoni, G. (2017). Quantitative assessment of synaptic density using the SV2A ligand C-11-UCBA in humans. Paper presented at 28th International Symposium on Cerebral Blood Flow, Metabolism and Function / 13th International Conference on Quantification of Brain Function with PET, APR 01-04, 2017, Int Soc Cerebral Blood Flow & Metab, Berlin, Germany. Journal of Cerebral Blood Flow and Metabolism, 37, 74-74
Open this publication in new window or tab >>Quantitative assessment of synaptic density using the SV2A ligand C-11-UCBA in humans
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2017 (English)In: Journal of Cerebral Blood Flow and Metabolism, ISSN 0271-678X, E-ISSN 1559-7016, Vol. 37, p. 74-74Article in journal, Meeting abstract (Other academic) Published
Place, publisher, year, edition, pages
Sage Publications, 2017
National Category
Endocrinology and Diabetes Hematology Neurology
Identifiers
urn:nbn:se:uu:diva-331031 (URN)000400157400107 ()
Conference
28th International Symposium on Cerebral Blood Flow, Metabolism and Function / 13th International Conference on Quantification of Brain Function with PET, APR 01-04, 2017, Int Soc Cerebral Blood Flow & Metab, Berlin, Germany
Available from: 2017-10-11 Created: 2017-10-11 Last updated: 2017-10-11
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