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Item Metadata only The Measurement of hole angulation for collimator used in SPECT(Mahidol University. Mahidol University Library and Knowledge Center, 1992) Chatchai Navikhacheevin; Anchali Krisanachinda; Chindarat IntaramarnItem Metadata only Optimum correction techniques in myocardial spect image(Mahidol University. Mahidol University Library and Knowledge Center, 2007) Wachirakorn Nakpoonnabutr; Anchali KrisanachindaItem Metadata only Lesion detectability in tomographic imaging of radioiodine-131(Mahidol University. Mahidol University Library and Knowledge Center, 2016) Supakiet Piasanthia; Putthiporn Charoenphun; Krisanat ChuamsaamarkkeeRadioiodine (131I) is a frequently used radionuclide for treatment and diagnosis of thyroid diseases in Nuclear Medicine.Undesirable image quality of 131I could compromise the accuracy and detectability limit especially in the small lesions. The goal of this work was to evaluate the lesion detectability and effects of acquisition time as well as scatter correction on tomographic imaging of 131I. This work also aimed to determine the optimised acquisition time for 131I SPECT. The NEMA IEC Body phantom (with a set of fillable hollow spheres) was used in this study. There were 2 conditions in this study; (1) hot lesion with no background and (2) hot lesion with warm background ratio of 10:1. The qualitative analysis was performed by three experienced nuclear medicine physicians, while quantitative analysis was determined by calculating the contrast to noise ratio (CNR) followed by two-tailed pair t-test statistical analysis.In the qualitative results for no background, all spheres were seen for all acquisition times in both scatter correction (SC) and no scatter correction (NC). Contrary to the lesion to background ratio of 10:1, the smallest sphere (0.52 mL, diameter of 10 mm) was not seen in both SC and NC. In the second smallest sphere (1.15 mL, diameter of 13 mm), the qualitative results were enhanced when prolonging acquisition time and performing scatter correction. The effects of acquisition time and scatter correction were clearly seen through a quantitative method. The CNRs increased when prolonging acquisition time for both no background and background ratio of 10:1. Interestingly, the statistical results indicated that means CNR acquired with 20 or 30 second per frame were not significantly different with 40 second per frame. However, when activity was presented in the background, the means CNR of 20 second per frame were different, whereas 30 (excluding smallest sphere) and 40 second per frame were not significantly different. On the effects of scatter, the CNRs increased when SC was applied to no background, whereas the effects of scatter for lesion with background ratio of 10:1 were undetermined. In conclusion, this study elucidated the lesion detectability of 131I SPECT. The acquisition time for no background condition could be optimized and acquisition time of 20 and 30 second per frame could be used instead of 40 second per frame. For the lesion to background ratio of 10:1, the acquisition, time should be carefully considered when the lesions are small