uu.seUppsala University Publications
Change search
Link to record
Permanent link

Direct link
BETA
Sörensen, Jens
Alternative names
Publications (10 of 126) Show all publications
Vorobyeva, A., Westerlund, K., Mitran, B., Altai, M., Rinne, S., Sörensen, J., . . . Karlström, A. E. (2018). Development of an optimal imaging strategy for selection of patients for affibody-based PNA-mediated radionuclide therapy. Scientific Reports, 8, Article ID 9643.
Open this publication in new window or tab >>Development of an optimal imaging strategy for selection of patients for affibody-based PNA-mediated radionuclide therapy
Show others...
2018 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, article id 9643Article in journal (Refereed) Published
Abstract [en]

Affibody molecules are engineered scaffold proteins, which demonstrated excellent binding to selected tumor-associated molecular abnormalities in vivo and highly sensitive and specific radionuclide imaging of Her2-expressing tumors in clinics. Recently, we have shown that peptide nucleic acid (PNA)-mediated affibody-based pretargeted radionuclide therapy using beta-emitting radionuclide Lu-177 extended significantly survival of mice bearing human Her2-expressing tumor xenografts. In this study, we evaluated two approaches to use positron emission tomography (PET) for stratification of patients for affibody-based pretargeting therapy. The primary targeting probe Z(HER2:342)SR-HP1 and the secondary probe HP2 (both conjugated with DOTA chelator) were labeled with the positron-emitting radionuclide Ga. Biodistribution of both probes was measured in BALB/C nu/nu mice bearing either SKOV-3 xenografts with high Her2 expression or DU-145 xenografts with low Her2 expression. (68)GaHP2 was evaluated in the pretargeting setting. Tumor uptake of both probes was compared with the uptake of pretargeted Lu-177-HP2. The uptake of both Ga-68-Z(HER2:342)SR-HP1 and Ga-68-HP2 depended on Her2-expression level providing clear discrimination of between tumors with high and low Her2 expression. Tumor uptake of Ga-68-HP2 correlated better with the uptake of Lu-177-HP2 than the uptake of Ga-68 Z(HER2:342) SR-HP1. The use of Ga-68-HP2 as a theranostics counterpart would be preferable approach for clinical translation.

Place, publisher, year, edition, pages
NATURE PUBLISHING GROUP, 2018
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:uu:diva-360010 (URN)10.1038/s41598-018-27886-0 (DOI)000436078500006 ()29942011 (PubMedID)
Funder
Swedish Research Council, 2015-02353Swedish Research Council, 2015-02509Swedish Research Council, 2016-05207VINNOVA, 2015-02509Swedish Cancer Society, CAN 2015/350Swedish Cancer Society, 2014/474Swedish Society for Medical Research (SSMF)
Available from: 2018-09-13 Created: 2018-09-13 Last updated: 2018-09-13Bibliographically 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
Show others...
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
von Below, C., Wassberg, C., Grzegorek, R., Kullberg, J., Gestblom, C., Sörensen, J., . . . Ahlström, H. (2018). MRI and 11C acetate PET/CT for prediction of regional lymph node metastasis in newly diagnosed prostate cancer. Radiology and Oncology, 52(1), 90-97
Open this publication in new window or tab >>MRI and 11C acetate PET/CT for prediction of regional lymph node metastasis in newly diagnosed prostate cancer
Show others...
2018 (English)In: Radiology and Oncology, ISSN 1318-2099, E-ISSN 1581-3207, Vol. 52, no 1, p. 90-97Article in journal (Refereed) Published
Abstract [en]

Background:

C acetate PET/CT parameters in predicting regional lymph node (LN) metastasis of newly diagnosed prostate cancer (PCa).

Patients and methods:

C acetate PET/CT (53 patients) before extended pelvic LN dissection. For each patient the visually most suspicious LN was assessed for mean apparent diffusion coefficient (ADCmean), maximal standardized uptake value (SUVmax), size and shape and the primary tumour for T stage on MRI and ADCmean and SUVmax in the index lesion. The variables were analysed in simple and multiple logistic regression analysis.

Results:

All variables, except ADCmean and SUVmax of the primary tumor, were independent predictors of LN metastasis. In multiple logistic regression analysis the best model was ADCmean in combintion with MRI T-stage where both were independent predictors of LN metastasis, this combination had an AUC of 0.81 which was higher than the AUC of 0.65 for LN ADCmean alone and the AUC of 0.69 for MRI T-stage alone.

Conclusions:

Several quantitative and qualitative imaging parameters are predictive of regional LN metastasis in PCa. The combination of ADCmean in lymph nodes and T-stage on MRI was the best model in multiple logistic regression with increased predictive value compared to lymph node ADCmean and T-stage on MRI alone.

Keywords
diffusion magnetic resonance imaging, lymph node excision, lymph nodes, positronemission tomography, prostatic neoplasm
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:uu:diva-346994 (URN)10.2478/raon-2018-0001 (DOI)000426260900012 ()29520210 (PubMedID)
Available from: 2018-03-23 Created: 2018-03-23 Last updated: 2018-05-16Bibliographically approved
Krasniqi, A., D'Huyvetter, M., Devoogdt, N., Frejd, F. Y., Sörensen, J., Orlova, A., . . . Tolmachev, V. (2018). Same-day imaging using small proteins: Clinical experience and translational prospects in oncology.. Journal of Nuclear Medicine, 59(6), 885-891
Open this publication in new window or tab >>Same-day imaging using small proteins: Clinical experience and translational prospects in oncology.
Show others...
2018 (English)In: Journal of Nuclear Medicine, ISSN 0161-5505, E-ISSN 1535-5667, Vol. 59, no 6, p. 885-891Article in journal (Refereed) Published
Abstract [en]

Imaging of expression of therapeutic targets may enable patients' stratification for targeted treatments. The use of small radiolabeled probes based on the heavy-chain variable region of heavy-chain-only immunoglobulins or non-immunoglobulin scaffolds permits rapid localization of radiotracers in tumors and rapid clearance from normal tissues. This makes high-contrast imaging possible on the day of injection. This mini-review focuses on small proteins for radionuclide-based imaging that would allow same-day imaging, with the emphasis on clinical applications and promising preclinical developments within the field of oncology.

Keywords
Animal Imaging, Molecular Imaging, Oncology: Breast, affibody, nanobody, radionuclide molecular imaging, scaffold proteins
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:uu:diva-351165 (URN)10.2967/jnumed.117.199901 (DOI)000435102600013 ()29545374 (PubMedID)
Funder
Swedish Cancer SocietySwedish Research Council
Note

De 2 sista författarna delar sistaförfattarskapet.

Available from: 2018-05-21 Created: 2018-05-21 Last updated: 2018-08-24Bibliographically approved
Tovedal, T., Lubberink, M., Morell, A., Estrada, S., Golla, S. S., Myrdal, G., . . . Lennmyr, F. (2017). Blood Flow Quantitation by Positron Emission Tomography During Selective Antegrade Cerebral Perfusion. Annals of Thoracic Surgery, 103(2), 610-616
Open this publication in new window or tab >>Blood Flow Quantitation by Positron Emission Tomography During Selective Antegrade Cerebral Perfusion
Show others...
2017 (English)In: Annals of Thoracic Surgery, ISSN 0003-4975, E-ISSN 1552-6259, Vol. 103, no 2, p. 610-616Article in journal (Refereed) Published
Abstract [en]

BACKGROUND: Perfusion strategies during aortic surgery usually comprise hypothermic circulatory arrest (HCA), often combined with selective antegrade cerebral perfusion (SACP) or retrograde cerebral perfusion. Cerebral blood flow (CBF) is a fundamental parameter for which the optimal level has not been clearly defined. We sought to determine the CBF at a pump flow level of 6 mL/kg/min, previously shown likely to provide adequate SACP at 20°C in pigs.

METHODS: Repeated positron emission tomography (PET) scans were used to quantify the CBF and glucose metabolism throughout HCA and SACP including cooling and rewarming. Eight pigs on cardiopulmonary bypass were assigned to either HCA alone (n = 4) or HCA+SACP (n = 4). The CBF was measured by repeated [(15)O]water PET scans from baseline to rewarming. The cerebral glucose metabolism was examined by [(18)F]fluorodeoxyglucose PET scans after rewarming to 37°C.

RESULTS: Cooling to 20°C decreased the cortical CBF from 0.31 ± 0.06 at baseline to 0.10 ± 0.02 mL/cm(3)/min (p = 0.008). The CBF was maintained stable by SACP of 6 mL/kg/min during 45 minutes. After rewarming to 37°C, the mean CBF increased to 0.24 ± 0.07 mL/cm(3)/min, without significant differences between the groups at any time-point exclusive of the HCA period. The net cortical uptake (Ki) of [(18)F]fluorodeoxyglucose after rewarming showed no significant difference between the groups.

CONCLUSIONS: Cooling autoregulated the CBF to 0.10 mL/cm(3)/min, and 45 minutes of SACP at 6 mL/kg/min maintained the CBF in the present model. Cerebral glucose metabolism after rewarming was similar in the study groups.

National Category
Surgery
Identifiers
urn:nbn:se:uu:diva-302609 (URN)10.1016/j.athoracsur.2016.06.029 (DOI)000397165400067 ()27592601 (PubMedID)
Available from: 2016-09-07 Created: 2016-09-07 Last updated: 2018-09-03Bibliographically approved
Nordström, J., Kero, T., Harms, H. J., Widström, C., Flachskampf, F., Sörensen, J. & Lubberink, M. (2017). Calculation of left ventricular volumes and ejection fraction from dynamic cardiac-gated 15O-water PET/CT: 5D-PET. EJNMMI Physics, 4(1), Article ID 26.
Open this publication in new window or tab >>Calculation of left ventricular volumes and ejection fraction from dynamic cardiac-gated 15O-water PET/CT: 5D-PET
Show others...
2017 (English)In: EJNMMI Physics, ISSN 2197-7364, E-ISSN 2191-219X, Vol. 4, no 1, article id 26Article in journal (Refereed) Published
Abstract [en]

BACKGROUND: Quantitative measurement of myocardial blood flow (MBF) is of increasing interest in the clinical assessment of patients with suspected coronary artery disease (CAD). (15)O-water positron emission tomography (PET) is considered the gold standard for non-invasive MBF measurements. However, calculation of left ventricular (LV) volumes and ejection fraction (EF) is not possible from standard (15)O-water uptake images. The purpose of the present work was to investigate the possibility of calculating LV volumes and LVEF from cardiac-gated parametric blood volume (V B) (15)O-water images and from first pass (FP) images. Sixteen patients with mitral or aortic regurgitation underwent an eight-gate dynamic cardiac-gated (15)O-water PET/CT scan and cardiac MRI. V B and FP images were generated for each gate. Calculations of end-systolic volume (ESV), end-diastolic volume (EDV), stroke volume (SV) and LVEF were performed with automatic segmentation of V B and FP images, using commercially available software. LV volumes and LVEF were calculated with surface-, count-, and volume-based methods, and the results were compared with gold standard MRI.

RESULTS: Using V B images, high correlations between PET and MRI ESV (r = 0.89, p < 0.001), EDV (r = 0.85, p < 0.001), SV (r = 0.74, p = 0.006) and LVEF (r = 0.72, p = 0.008) were found for the volume-based method. Correlations for FP images were slightly, but not significantly, lower than those for V B images when compared to MRI. Surface- and count-based methods showed no significant difference compared with the volume-based correlations with MRI. The volume-based method showed the best agreement with MRI with no significant difference on average for EDV and LVEF but with an overestimation of values for ESV (14%, p = 0.005) and SV (18%, p = 0.004) when using V B images. Using FP images, none of the parameters showed a significant difference from MRI. Inter-operator repeatability was excellent for all parameters (ICC > 0.86, p < 0.001).

CONCLUSION: Calculation of LV volumes and LVEF from dynamic (15)O-water PET is feasible and shows good correlation with MRI. However, the analysis method is laborious, and future work is needed for more automation to make the method more easily applicable in a clinical setting.

National Category
Cardiac and Cardiovascular Systems Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:uu:diva-333781 (URN)10.1186/s40658-017-0195-2 (DOI)000415372700001 ()29138942 (PubMedID)
Available from: 2017-11-16 Created: 2017-11-16 Last updated: 2018-02-22Bibliographically 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.
Show others...
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
Regula, N. K., Lubberink, M., Jorulf, H., Ladjevardi, S., Häggman, M. & Sörensen, J. (2017). Dynamic Imaging of Prostate Cancer with 11C-acetate PET/CT. 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 662.
Open this publication in new window or tab >>Dynamic Imaging of Prostate Cancer with 11C-acetate PET/CT
Show others...
2017 (English)In: Journal of Nuclear Medicine, ISSN 0161-5505, E-ISSN 1535-5667, Vol. 58, no S1, article id 662Article in journal, Meeting abstract (Other academic) Published
Abstract [en]

Objectives: Dynamic 11C-acetate PET/CT can be used to study tissue perfusion and carbon flux simultaneously, but studies in cancer are limited. We investigated the kinetics of 11C-acetate in prostate cancer subjects using parametric images with an image-derived input function (IDIF).

Methods: Twenty-one patients with newly diagnosed low-moderate risk prostate cancer were studied. All underwent pelvic MRI. Dynamic 11C-acetate (5 MBq/kg) PET/CT of the pelvis was acquired for 32 minutes with 32 time frames. An IDIF was acquired from iliac vessels with multiple small regions of interest (ROIs) and a standardized metabolite correction. Parametric images of K1 (extraction), k2 (oxidative metabolism) and Vd (=K1/k2, anabolic metabolism defined as carbon retention) were constructed using a one-tissue compartment model. ROIs of the largest cancer region in each patient and normal prostate tissue were drawn using information from MRI (T2 and DWI images) and from post-surgical histopathology of whole prostate sections (n=7).

Results: Mean PSA was 8.3±3.9. Median Gleason Sum was 6 (range 5-7). K1, Vd and SUVs were higher in cancerous regions compared to normal prostate for all patients (p<0.001). PSA correlated to early SUV (r=0.50, p=0.02) and K1 (r=0.48, p=0.03). Early and late SUVs were correlated to Vd (r>0.76, p<0.001) and K1 (r>0.61, p<0.005).

Conclusion: Parametric images could be used to visualize the 11C-acetate kinetics of the prostate. In this cohort of relatively low-risk cancers, PSA values were related to cancer perfusion. SUV of cancerous regions at any time point is primarily associated with anabolic metabolism. Research Support: Swedish Cancer Foundation (Cancerfonden)

National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:uu:diva-333339 (URN)000404949903062 ()
Conference
Annual Meeting of the Society-of-Nuclear-Medicine-and-Molecular-Imaging (SNMMI), JUN 10-14, 2017, Denver, CO
Funder
Swedish Cancer Society
Available from: 2017-11-14 Created: 2017-11-14 Last updated: 2017-11-14Bibliographically approved
Sandberg, D. T., Tolmachev, V., Velikyan, I., Olofsson, H., Wennborg, A., Feldwisch, J., . . . Sörensen, J. (2017). Intra-image referencing for simplified assessment of HER2-expression in breast cancer metastases using the Affibody molecule ABY-025 with PET and SPECT.. European Journal of Nuclear Medicine and Molecular Imaging, 44(8), 1337-1346
Open this publication in new window or tab >>Intra-image referencing for simplified assessment of HER2-expression in breast cancer metastases using the Affibody molecule ABY-025 with PET and SPECT.
Show others...
2017 (English)In: European Journal of Nuclear Medicine and Molecular Imaging, ISSN 1619-7070, E-ISSN 1619-7089, Vol. 44, no 8, p. 1337-1346Article in journal (Refereed) Published
Abstract [en]

PURPOSE: In phase I/II-studies radiolabelled ABY-025 Affibody molecules identified human epidermal growth factor receptor 2 (HER2) expression in breast cancer metastases using PET and SPECT imaging. Here, we wanted to investigate the utility of a simple intra-image normalization using tumour-to-reference tissue-ratio (T/R) as a HER2 status discrimination strategy to overcome potential issues related to cross-calibration of scanning devices.

METHODS: Twenty-three women with pre-diagnosed HER2-positive/negative metastasized breast cancer were scanned with [(111)In]-ABY-025 SPECT/CT (n = 7) or [(68)Ga]-ABY-025 PET/CT (n = 16). Uptake was measured in all metastases and in normal spleen, lung, liver, muscle, and blood pool. Normal tissue uptake variation and T/R-ratios were established for various time points and for two different doses of injected peptide from a total of 94 whole-body image acquisitions. Immunohistochemistry (IHC) was used to verify HER2 expression in 28 biopsied metastases. T/R-ratios were compared to IHC findings to establish the best reference tissue for each modality and each imaging time-point. The impact of shed HER2 in serum was investigated.

RESULTS: Spleen was the best reference tissue across modalities, followed by blood pool and lung. Spleen-T/R was highly correlated to PET SUV in metastases after 2 h (r = 0.96, P < 0.001) and reached an accuracy of 100% for discriminating IHC HER2-positive and negative metastases at 4 h (PET) and 24 h (SPECT) after injection. In a single case, shed HER2 resulted in intense tracer retention in blood. In the remaining patients shed HER2 was elevated, but without significant impact on ABY-025 biodistribution.

CONCLUSION: T/R-ratios using spleen as reference tissue accurately quantify HER2 expression with radiolabelled ABY-025 imaging in breast cancer metastases with SPECT and PET. Tracer binding to shed HER2 in serum might affect quantification in the extreme case.

Keywords
Affibody, HER2-receptor, PET, SPECT, Shedding, T/R
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-317746 (URN)10.1007/s00259-017-3650-3 (DOI)000403468900012 ()28261749 (PubMedID)
Funder
Swedish Cancer Society
Available from: 2017-03-17 Created: 2017-03-17 Last updated: 2018-02-28Bibliographically 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
Show others...
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
Organisations

Search in DiVA

Show all publications