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  • 1. Hsu, David Fc
    et al.
    Ilan, Ezgi
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
    Peterson, William T
    Uribe, Jorge
    Lubberink, Mark
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
    Levin, Craig S
    Studies of a Next Generation Silicon-Photomultiplier-Based Time-of-Flight PET/CT System2017In: Journal of Nuclear Medicine, ISSN 0161-5505, E-ISSN 1535-5667, Vol. 58, no 9, p. 1511-1518Article in journal (Refereed)
    Abstract [en]

    This article presents system performance studies of the Discovery MI PET/CT system, a new time-of-flight (TOF) system based on silicon photomultipliers. System performance and clinical imaging comparisons were made between this next-generation system and other commercially available PET/CT and PET/MR systems, as well as between different reconstruction algorithms. Methods: Spatial resolution, sensitivity, NECR, scatter fraction, count rate accuracy, and image quality were characterized with the NEMA NU-2 2012 standards. Energy and coincidence time resolution were measured. Tests were conducted independently and results were averaged on two Discovery MI scanners installed at Stanford and Uppsala University Hospitals. Back-to-back patient scans were also performed between the Discovery MI PET/CT, Discovery 690 PET/CT, and SIGNA PET/MR systems. Clinical images were reconstructed with both ordered-subset expectation maximization (OSEM) and the "Q.Clear" reconstruction algorithms, and examined qualitatively. Results: The averaged full-width half max (FWHM) of the radial/tangential/axial spatial resolution reconstructed with FBP at 1, 10, and 20 cm from the system center are, respectively, 4.10/4.19/4.48 mm, 5.47/4.49/6.01 mm, and 7.53/4.90/6.10 mm. The averaged sensitivity is 13.7 cps/kBq at the center of the FOV. Averaged peak noise equivalent count rate is 193.4 kcps at 21.9 kBq/mL with a scatter fraction of 40.6%. The averaged contrast recovery coefficients for the image quality phantom are 53.7/64.0/73.1/82.7/86.8/90.7 for the 10/13/17/22/28/37 mm diameter spheres. The average photopeak energy resolution is 9.40% FWHM and the average coincidence time resolution is 375.4 ps FWHM. Clinical image comparisons between the PET/CT systems demonstrate the high quality of the Discovery MI system. Comparisons between the Discovery MI and SIGNA systems show similar spatial resolution and overall imaging performance. Lastly, results indicate significant image quality and contrast-to-noise performance enhancement for the "Q.Clear" reconstruction algorithm when compared to OSEM. Conclusion: Excellent performance was achieved with the new Discovery MI system, including 375 ps FWHM coincidence time resolution and sensitivity of 14 cps/kBq. Comparisons between different image reconstruction algorithms and other multimodal SiPM and non-SiPM-based PET detector system designs indicate substantial performance enhancements are possible with this next-generation system.

  • 2.
    Hsu, David
    et al.
    Stanford Univ, Radiol, Elect Engn, Stanford, CA 94305 USA..
    Ilan, Ezgi
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
    Peterson, William
    GE Healthcare, Waukesha, WI USA..
    Uribe, Jorge
    GE Healthcare, Waukesha, WI USA..
    Lubberink, Mark
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
    Levin, Craig
    Stanford Univ, Radiol, Elect Engn, Bioengn, Stanford, CA 94305 USA..
    Studies of a Next Generation Silicon-Photomultiplier-Based Time-of-Flight PET/CT System2017In: Journal of Nuclear Medicine, ISSN 0161-5505, E-ISSN 1535-5667, Vol. 58, no S1, article id 89Article in journal (Other academic)
    Abstract [en]

    Objectives: This article presents studies performed with the Discovery MI PET/CT system, a new time-of-flight (TOF) system based on silicon photomultipliers. System performance was characterized according to the NEMA NU-2 2012 standards. Comparisons of performance and clinical images were also made between this next-generation system and other commercially available PET/CT and PET/MR systems, as well as between different image reconstruction algorithms.

    Methods: Spatial resolution, sensitivity, NECR, scatter fraction, count rate accuracy, and image quality were characterized according to the NEMA NU-2 2012 standards. In addition, energy and coincidence time resolution were measured using a line source at the center of the field-of-view (CFOV). Tests were conducted independently on two Discovery MI scanners installed at Stanford University Hospital and Uppsala University Hospital, and results were averaged between the two systems. In addition, back-to-back patient scans were performed between the Discovery MI PET/CT, Discovery 690 PET/CT, and SIGNA PET/MR systems. Clinical images were reconstructed with both ordered-subset expectation maximization (OSEM) reconstruction algorithms and the block-sequential regularized expectation maximization (BSREM) "Q.Clear" reconstruction algorithm, and examined qualitatively.

    Results: The averaged FWHM of the radial, tangential, and axial spatial resolution reconstructed with filtered backprojection (FBP) at 1/10/20 cm from the system center are, respectively, 4.10/4.19/4.48 mm, 5.47/4.49/6.01 mm, and 7.53/4.90/6.10 mm. The averaged sensitivity is 13.7 cps/kBq at the center and 13.4 cps/kBq at 10 cm radial offset from the center. Averaged peak noise equivalent count rate (NECR) is 193.4 kcps at 21.9 kBq/mL with a scatter fraction (SF) of 40.6%. The averaged contrast recovery (CR) coefficients for the image quality (IQ) phantom are 53.7/64.0/73.1/82.7/86.8/90.7 for the 10/13/17/22/28/37 mm diameter spheres over 3 separate acquisitions. The average photopeak energy resolution is 9.40% FWHM and the average coincidence time resolution is 375.4 ps FWHM. Clinical image comparisons between the PET/CT systems demonstrate the very high quality of the Discovery MI system. Comparisons between the Discovery MI PET/CT and SIGNA PET/MR systems, which contain identical detector architectures but with different detector diameters, show similar spatial resolution and overall imaging performance. Lastly, results indicate significant image quality and contrast-to-noise performance enhancement for the "Q.Clear" reconstruction algorithm when compared to OSEM.

    Conclusion: Excellent performance was achieved with the new Discovery MI system, including 375 ps FWHM coincidence time resolution and sensitivity of 14 cps/kBq. Comparisons between different image reconstruction algorithms and other multimodal SiPM and non-SiPM-based PET detector system designs indicate substantial performance enhancements are possible with this next-generation system. Research Support: None

  • 3.
    Ilan, Ezgi
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
    Deller, Timothy
    Gen Elect, Elm Grove, WI USA..
    Kjellberg, Fredric
    GE Healthcare, Stockholm, Sweden..
    Peterson, William
    GE Healthcare, Waukesha, WI USA..
    Lubberink, Mark
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
    Performance comparison of three commercially available PET systems: SIGNA PET/MR, Discovery IQ and Discovery MI2017In: Journal of Nuclear Medicine, ISSN 0161-5505, E-ISSN 1535-5667, Vol. 58, no S1, article id 1353Article in journal (Other academic)
    Abstract [en]

    Objectives: The NEMA performance measurement standard (NEMA NU 2-2012) for PET scanners provides guidelines on how to assess the performance of Positron Emission Tomography (PET). Three different state of the art PET systems were installed at Uppsala University Hospital between years 2014-2016 and independent NEMA standard tests were performed. The aim of this study was to compare system performance of the three scanners.

    Methods: Three commercially available scanners from GE-healthcare (SIGNA PET/MR; Discovery IQ PET/CT; Discovery MI PET/CT) were evaluated. The SIGNA and MI systems are based on LYSO crystals and digital SiPMs, whereas the IQ uses BGO crystals and regular PMTs. Spatial resolution, sensitivity, count rate statistics, count rate accuracy and image quality were assessed according to the NEMA NU 2-2012 standards. In addition to the NEMA standard test, recovery was assessed for different reconstructions using the NEMA image quality phantom at a contrast of 4:1 in all spheres, and a triple line insert phantom. These tests were performed on all three scanners in a single session, avoiding differences due to variability in phantom preparation.

    Results: Full width of half maximum (FWHM) of the spatial resolution (radial/tangential/axial) reconstructed with filtered back projection (FBP) at 1,10 and 20 cm from the centre of FOV is illustrated in figure 1A for each system. The average sensitivity, Peak NECR, scatter fraction and count rate accuracy of each system is presented in table 1. The average image contrast recovery coefficients of SIGNA, IQ and MI varied between 45, 40 and 56 % (10 mm sphere) to 74, 72 and 84 % (22 mm sphere) respectively. The average image contrast recovery coefficients is presented in figure 1B. The lung error for SIGNA, IQ and MI were 2.7, 18 and 5.2 % respectively. Using reconstruction settings recommended for clinical use (Signa: TOF-OSEM, 2 iterations/28 subsets, 5 mm post-filter; IQ: OSEM, 4/12, 4 mm; MI: TOF-OSEM, 3/16, 5 mm, all with resolution recovery) recovery based on a volume of interest over whole spheres varied between 50, 38 and 51 % (10 mm sphere) to 86, 83 and 87 % (22 mm sphere), respectively. In addition to the recommended settings for clinical use, Q.Clear (Block-sequential regularized expectation maximization (BSREM) with PSF modeling) reconstructions with beta values ranging from 100 to 500 with step of 200 were reconstructed. The volume recovery of each system for varying reconstructions is presented in Figure 1C. The mean radial/tangential/central spatial resolution of SIGNA, IQ and MI using the triple line insert phantom when using the recommended standard reconstructions and Q.Clear reconstruction is presented in Figure 1D.

    Conclusion: As expected, the two ToF systems based on LYSO crystals coupled to digital SiPMs (SIGNA and MI), resulted in an overall better resolution, image quality, NECR and volume recovery than the non-TOF BGO coupled to non-digital detector system (IQ). The image quality and spatial resolution improved when Q.Clear reconstruction was used. The sensitivity was higher in SIGNA than in MI and IQ due to a 25 cm axial FOV in SIGNA, compared to 20 cm for MI and IQ. In conclusion, the new SiPM-based PET detector systems provide a considerable enhancement in system performance.

  • 4.
    Ilan, Ezgi
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
    Sandström, Mattias
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
    Velikyan, Irina
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
    Sundin, Anders
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
    Eriksson, Barbro
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences.
    Lubberink, Mark
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
    Parametric Net Influx Rate Images of 68Ga-DOTATOC and 68Ga-DOTATATE: Quantitative Accuracy and Improved Image Contrast2017In: Journal of Nuclear Medicine, ISSN 0161-5505, E-ISSN 1535-5667, Vol. 58, no 5, p. 744-749Article in journal (Refereed)
    Abstract [en]

    (68)Ga-DOTATOC and (68)Ga-DOTATATE are radiolabelled somatostatin analogs used for diagnosis of somatostatin receptor expressing neuroendocrine tumors (NETs) and SUV -measurements are suggested for treatment monitoring. However, changes in net-influx rate (Ki) may better reflect treatment effects than those of the SUV, and accordingly there is a need to compute parametric images showing Ki at the voxel level. The aim of this study was to evaluate parametric methods for computation of parametric Ki images by comparison to volume of interest based methods and to assess image contrast in terms of tumor-to-liver ratio.

    METHODS: Ten patients with metastatic NETs underwent a 45-min dynamic PET examination followed by whole-body PET/CT at 1 h post injection of (68)Ga-DOTATOC and (68)Ga-DOTATATE on consecutive days. Parametric Ki images were computed using a basis function method (BFM) implementation of the two tissue irreversible compartment model and the Patlak method using a descending aorta image-derived input function, and mean tumor Ki values were determined for 50% isocontour VOIs and compared to Ki values based on non-linear regression (NLR) of the whole-VOI time-activity curve. A subsample of healthy liver was delineated in the whole-body and Ki images and tumor-to-liver ratios were calculated in order to evaluate image contrast. Correlation and agreement between VOI-based and parametric Ki values were assessed using regression and Bland-Altman analysis.

    RESULTS: Correlation (R2) between NLR-based and parametric image-based (BFM) tumor Ki values was 0.98 (slope 0.81) and 0.97 (slope 0.88) for (68)Ga-DOTATOC and (68)Ga DOTATATE, respectively. For Patlak analysis, correlation between NLR-based and parametric based (Patlak) tumor Ki were 0.95 (slope 0.71) and 0.92 (slope 0.74) for (68)Ga-DOTATOC and (68)Ga-DOTATATE, respectively. There was no bias between NLR and parametric based Ki-values. Tumor-to-liver contrast was 1.6 and 2.0 times higher in the parametric BFM-Ki images, and 2.3 and 3.0 times in the Patlak images, than in the whole-body images for (68)Ga-DOTATOC and (68)Ga-DOTATATE, respectively.

    CONCLUSION: A high correlation and agreement between NLR- and parametric based Ki values was found, showing that parametric net influx rate images are quantitatively accurate. In addition, tumor-to-liver contrast was superior in the parametric Ki images compared to whole-body images both for (68)Ga-DOTATOC and (68)Ga DOTATATE.

  • 5.
    Ilan, Ezgi
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
    Sandström, Mattias
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
    Velikyan, Irina
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Radiology, Oncology and Radiation Science, Biomedical Radiation Sciences. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
    Sundin, Anders
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
    Lubberink, Mark
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
    Validation of parametric net influx rate images of Ga-68-DOTATOC and Ga-68-DOTATATE2015In: European Journal of Nuclear Medicine and Molecular Imaging, ISSN 1619-7070, E-ISSN 1619-7089, Vol. 42, no S1, p. S232-S232Article in journal (Other academic)
  • 6.
    Ilan, Ezgi
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Radiology, Oncology and Radiation Science, Section of Nuclear Medicine and PET. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
    Sandström, Mattias
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Radiology, Oncology and Radiation Science, Section of Nuclear Medicine and PET. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
    Wassberg, Cecilia
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Radiology, Oncology and Radiation Science, Radiology.
    Sundin, Anders
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Radiology, Oncology and Radiation Science, Radiology.
    Garske-Román, Ulrike
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Radiology, Oncology and Radiation Science, Radiology.
    Eriksson, Barbro
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Endocrine Tumor Biology.
    Granberg, Dan
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences.
    Lubberink, Mark
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Radiology, Oncology and Radiation Science, Radiology.
    Dose Response of Pancreatic Neuroendocrine Tumors Treated with Peptide Receptor Radionuclide Therapy Using 177Lu-DOTATATE2015In: Journal of Nuclear Medicine, ISSN 0161-5505, E-ISSN 1535-5667, Vol. 56, no 2, p. 177-182Article in journal (Refereed)
    Abstract [en]

    UNLABELLED: Peptide receptor radionuclide therapy (PRRT) is a promising treatment for patients with neuroendocrine tumors, giving rise to improved survival. Dosimetric calculations in relation to PRRT have been concentrated to normal organ dosimetry in order to limit side effects. However, the relation between the absorbed dose to the tumor and treatment response has so far not been established. Better knowledge in this respect may improve the understanding of treatment effects, allow for improved selection of those patients who are expected to benefit from PRRT, and avoid unnecessary treatments. The aim of the present work was to evaluate the dose-response relationship for pancreatic neuroendocrine tumors treated with PRRT using (177)Lu-DOTATATE.

    METHODS: Tumor-absorbed dose calculations were performed for 24 lesions in 24 patients with metastasized pancreatic neuroendocrine tumors treated with repeated cycles of (177)Lu-DOTATATE at 8-wk intervals. The absorbed dose calculations relied on sequential SPECT/CT imaging at 24, 96, and 168 h after infusion of (177)Lu-DOTATATE. The unit density sphere model from OLINDA was used for absorbed dose calculations. The absorbed doses were corrected for partial-volume effect based on phantom measurements. On the basis of these results, only tumors larger than 2.2 cm in diameter at any time during the treatment were included for analysis. To further decrease the effect of partial-volume effect, a subgroup of tumors (>4.0 cm) was analyzed separately. Tumor response was evaluated by CT using Response Evaluation Criteria In Solid Tumors.

    RESULTS: Tumor-absorbed doses until best response ranged approximately from 10 to 340 Gy. A 2-parameter sigmoid fit was fitted to the data, and a significant correlation between the absorbed dose and tumor reduction was found, with a Pearson correlation coefficient (R(2)) of 0.64 for tumors larger than 2.2 cm and 0.91 for the subgroup of tumors larger than 4.0 cm. The largest tumor reduction was 57% after a total absorbed dose of 170 Gy.

    CONCLUSION: The results imply a significant correlation between absorbed dose and tumor reduction. However, further studies are necessary to address the large variations in response for similar absorbed doses.

  • 7.
    Ilan, Ezgi
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology. Univ Uppsala Hosp, Med Phys, Uppsala, Sweden..
    Sundin, Anders
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology. Univ Uppsala Hosp, Med Imaging Ctr, Uppsala, Sweden..
    Velikyan, Irina
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology. Univ Uppsala Hosp, Med Imaging Ctr, Uppsala, Sweden..
    Sandström, Mattias
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology. Univ Uppsala Hosp, Med Phys, Uppsala, Sweden..
    Ahlström, Håkan
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology. Univ Uppsala Hosp, Med Imaging Ctr, Uppsala, Sweden..
    Lubberink, Mark
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology. Univ Uppsala Hosp, Med Phys, Uppsala, Sweden..
    Comparison of PET/CT and PET/MR-based Ga-68-DOTATOC standardized uptake values2016In: European Journal of Nuclear Medicine and Molecular Imaging, ISSN 1619-7070, E-ISSN 1619-7089, Vol. 43, p. S447-S447Article in journal (Refereed)
  • 8.
    Lindström, Elin
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology. Uppsala Univ Hosp, Med Phys, Uppsala, Sweden..
    Lindsjö, Lars
    Uppsala Univ Hosp, PET Ctr, Uppsala, Sweden..
    Ilan, Ezgi
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology. Uppsala Univ Hosp, Med Phys, Uppsala, Sweden..
    Sundin, Anders
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology. Uppsala Univ Hosp, PET Ctr, Uppsala, Sweden..
    Sörensen, Jens
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Clinical Physiology. Uppsala Univ Hosp, PET Ctr, Uppsala, Sweden..
    Danfors, Torsten
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology. Uppsala Univ Hosp, PET Ctr, Uppsala, Sweden..
    Antoni, Gunnar
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Division of Molecular Imaging. Uppsala Univ Hosp, PET Ctr, Uppsala, Sweden..
    Lubberink, Mark
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology. Uppsala Univ Hosp, Med Phys, Uppsala, Sweden..
    Optimisation of penalized likelihood estimation reconstruction (Q.Clear) on a digital time-of-flight PET-CT scanner for four different PET tracers2017In: Journal of Nuclear Medicine, ISSN 0161-5505, E-ISSN 1535-5667, Vol. 58, no S1, article id 1355Article in journal (Other academic)
    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.

  • 9.
    Lindström, Elin
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology. Department of Medical Physics, Uppsala University Hospital, Uppsala, Sweden.
    Sundin, Anders
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
    Trampal, Carlos
    Lindsjö, Lars
    Ilan, Ezgi
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology. Department of Medical Physics, Uppsala University Hospital, Uppsala, Sweden .
    Danfors, Torsten
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
    Antoni, Gunnar
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Medicinal Chemistry, Preparative Medicinal Chemistry.
    Sörensen, Jens
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology. PET Centre, Uppsala University Hospital, Uppsala, Sweden.
    Lubberink, Mark
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology. Department of Medical Physics, Uppsala University Hospital, Uppsala, Sweden .
    Evaluation of penalized likelihood estimation reconstruction on a digital time-of-flight PET/CT scanner for 18F-FDG whole-body examinations2018In: Journal of Nuclear Medicine, ISSN 0161-5505, E-ISSN 1535-5667, Vol. 59, no 7, p. 1152-1158Article in journal (Refereed)
    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.

  • 10.
    Sandström, Mattias
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology.
    Ilan, Ezgi
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology.
    Karlberg, Anna
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology.
    Johansson, Silvia
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Experimental and Clinical Oncology.
    Freedman, Nanette
    Hadassah Hebrew Univ Med Ctr, Med Biophys & Nucl Med, Jerusalem, Israel.
    Garske-Román, Ulrike
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
    Method dependence, observer variability and kidney volumes in radiation dosimetry of (177)Lu-DOTATATE therapy in patients with neuroendocrine tumours.2015In: EJNMMI physics, ISSN 2197-7364, Vol. 2, no 1, article id 24Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Radionuclide therapy can be individualized by performing dosimetry. To determine absorbed organ doses in (177)Lu-DOTATATE therapy, three methods based on activity concentrations are currently in use: the small volume of interest (sVOI) method, and two methods based on large VOIs either on anatomical CT (aVOI) or on thresholds on functional images (tVOI). The main aim of the present work was to validate the sVOI in comparison to the other two methods regarding agreement and time efficiency. Secondary aims were to investigate inter-observer variability for the sVOI and the change of functional organ volumes following therapy.

    METHODS: Thirty patients diagnosed with neuroendocrine tumours undergoing therapy with (177)Lu-DOTATATE were included. Each patient underwent three SPECT/CT scans at 1, 4 and 7 days after the treatment. Three independent observers calculated absorbed doses to the right and left kidney and the spleen using sVOI and one observer used aVOI. For tVOI, the absorbed doses were calculated based on automatically drawn isocontours around the organs at different thresholds (42, 50, 60 and 70 %). The inter-observer difference between the calculated absorbed doses for sVOI was calculated, and the differences between the three methods were computed. Ratios of organ volumes acquired at days 1, 4 and 7 versus the volume at day 1 were calculated for the tVOI method.

    RESULTS: The differences in results of the absorbed dose calculations using all the sVOI and tVOI were small (<5 %). Absorbed dose calculations using aVOI differed slightly more from these results but were still below 10 %. The differences between the three dose calculation methods varied between <5 and 10 %. The organ volumes derived from the tVOI were independent of time for the spleen while they decreased with time for the kidneys. The fastest analysis was performed with the sVOI method.

    CONCLUSIONS: All three dose calculation methods rendered comparable results with small inter-observer differences for sVOI. Unlike the spleen, the functional volume of the kidneys decreased over time during therapy, which suggests that the absorbed dose calculation for the kidneys on activity concentrations should be performed for each time point. The sVOI is the preferred method for calculating absorbed doses in solid organs.

  • 11.
    Sandström, Mattias
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology.
    Ilan, Ezgi
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
    Sundin, Anders
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
    Lubberink, Mark
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
    Image quality measurements with 177Lu on a GE Discovery 670 CZT2017In: Journal of Nuclear Medicine, ISSN 0161-5505, E-ISSN 1535-5667, Vol. 58, no S1, article id 763Article in journal (Other academic)
  • 12.
    Sandström, Mattias
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
    Ilan, Ezgi
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
    Sundin, Anders
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
    Lubberink, Mark
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
    Is there a gender difference of absorbed dose to the risk organs in patients receiving 177Lu-Octreotate therapy?2017In: Journal of Nuclear Medicine, ISSN 0161-5505, E-ISSN 1535-5667, Vol. 58, no S1, article id 248Article in journal (Other academic)
1 - 12 of 12
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