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- Ilan, Ezgi, et al.
(författare)
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Parametric Net Influx Rate Images of 68Ga-DOTATOC and 68Ga-DOTATATE : Quantitative Accuracy and Improved Image Contrast
- 2017
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Ingår i: Journal of Nuclear Medicine. - : Society of Nuclear Medicine. - 0161-5505 .- 1535-5667 .- 2159-662X. ; 58:5, s. 744-749
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Tidskriftsartikel (refereegranskat)abstract
- (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.
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- Lindström, Elin, et al.
(författare)
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Regularized reconstruction of digital time-of-flight Ga-68-PSMA-11 PET/CT for the detection of recurrent disease in prostate cancer patients
- 2019
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Ingår i: Theranostics. - : Ivyspring International Publisher. - 1838-7640. ; 9:12, s. 3476-3484
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Tidskriftsartikel (refereegranskat)abstract
- Accurate localization of recurrent prostate cancer (PCa) is critical, especially if curative therapy is intended. With the aim to optimize target-to-background uptake ratio in Ga-68-PSMA-11 PET, we investigated the image quality and quantitative measures of regularized reconstruction by block-sequential regularized expectation maximization (BSREM).Methods: The study encompassed retrospective reconstruction and analysis of 20 digital time-of-flight (TOF) PET/CT examinations acquired 60 min post injection of 2 MBq/kg of Ga-68-PSMA-11 in PCa patients with biochemical relapse after primary treatment. Reconstruction by ordered-subsets expectation maximization (OSEM; 3 iterations, 16 subsets, 5 mm gaussian postprocessing filter) and BSREM (beta-values of 100-1600) were used, both including TOF and point spread function (PSF) recovery. Background variability (BV) was measured by placing a spherical volume of interest in the right liver lobe and defined as the standard deviation divided by the mean standardized uptake value (SUV). The image quality was evaluated in terms of signal-to-noise ratio (SNR) and signal-to-background ratio (SBR), using SUVmax of the lesions. A visual assessment was performed by four observers.Results:OSEM reconstruction produced images with a BV of 15%, whereas BSREM with a beta-value above 300 resulted in lower BVs than OSEM (36% with beta 100, 8% with beta 1300). Decreasing the acquisition duration from 2 to 1 and 0.5 min per bed position increased BV for both reconstruction methods, although BSREM with beta-values equal to or higher than 800 and 1200, respectively, kept the BV below 15%. In comparison of BSREM with OSEM, the mean SNR improved by 25 to 66% with an increasing beta-value in the range of 200-1300, whereas the mean SBR decreased with an increasing beta-value, ranging from 0 to 125% with a beta-value of 100 and 900, respectively. Decreased acquisition duration resulted in beta-values of 800 to 1000 and 1200 to 1400 for 1 and 0.5 min per bed position, respectively, producing improved image quality measures compared with OSEM at a full acquisition duration of 2 min per bed position. The observer study showed a slight overall preference for BSREM beta 900 although the interobserver variability was high.Conclusion:BSREM image reconstruction with beta-values in the range of 400-900 resulted in lower BV and similar or improved SNR and SBR in comparison with OSEM.
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