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Somatostatin receptor scintigraphy (SRS) is a useful tool in the assessment of GEP-NET (gastroenteropancreatic neuroendocrine tumor) patients. The choice of appropriate settings of image reconstruction parameters is crucial in interpretation of these images. The aim of the study was to investigate how the GEP NET lesion signal to noise ratio (TCS/TCB) depends on different reconstruction settings for Flash 3D software (Siemens).SRS results of 76 randomly selected patients with confirmed GEP-NET were analyzed. For SPECT studies the data were acquired using standard clinical settings 3-4 h after the injection of 740 MBq 99mTc-[EDDA/HYNIC] octreotate. To obtain final images the OSEM 3D Flash reconstruction with different settings and FBP reconstruction were used. First, the TCS/TCB ratio in voxels was analyzed for different combinations of the number of subsets and the number of iterations of the OSEM 3D Flash reconstruction. Secondly, the same ratio was analyzed for different parameters of the Gaussian filter (with FWHM = 2-4 times greater from the pixel size). Also the influence of scatter correction on the TCS/TCB ratio was investigated.With increasing number of subsets and iterations, the increase of TCS/TCB ratio was observed. With increasing settings of Gauss [FWHM coefficient] filter, the decrease of TCS/TCB ratio was reported. The use of scatter correction slightly decreases the values of this ratio.OSEM algorithm provides a meaningfully better reconstruction of the SRS SPECT study as compared to the FBP technique. A high number of subsets improves image quality (images are smoother). Increasing number of iterations gives a better contrast and the shapes of lesions and organs are sharper. The choice of reconstruction parameters is a compromise between image qualitative appearance and its quantitative accuracy and should not be modified when comparing multiple studies of the same patient.

The effective radioiodine treatment of patients with DTC is possible only after raising the TSH value over 30 μUI/ml. This effect might be obtained by either endogenous or exogenous stimulation. The aim of this study was to evaluate differences in (131)I biokinetics of selected regions of interest (ROIs) in cases of endogenous and exogenous stimulation.Two groups of 50 patients were enrolled in the study. All patients were treated with 3.7 GBq of ¹³¹I; the first group after thyroid hormone withdrawal (THW), the second group after rhTSH administration (rhTSH). On the basis of post-treatment images, the uptake ratios over selected ROIs (thyroid remnants, mediastinum, liver, stomach, abdomen, and whole-body) were compared between groups.In the case of uptake over the whole-body and the liver, statistically significant higher values were received for the THW group. For the remaining regions, the differences between groups were statistically insignificant, but uptake ratios in the rhTSH group were generally numerically lower compared to the THW group.The revealed difference in radioiodine biokinetics after thyroid hormone withdrawal or administration of recombinant human TSH may influence many important aspects of patients with DTC treatment, such as the choice of proper therapeutic scheme, the cost of therapy, and the dose assessment.