Sutapa Rakshit, Basant Malpani, Hemant Shimpi, Nawab Singh Baghel
Radiation Medicine Centre (BARC), TMH, Parel, Mumbai, Maharashtra, India
Objective: The aim of this study is to evaluate the performance characteristics of ge infinia gamma camera collimator systems using line sources fabricated in-house.
Materials and Methods: Approximately 400 μL of radioactive solution of either 131I, 177Lu, 99mTc and 153Sm was filled in Teflon tubes (TEFZEL, Φ =1/16”, l = 50cm). These tubings were affixed onto Perspex sheets (53 cm × 8 cm × 0.2 cm). Line sources were placed facing the collimator surface for static acquisition at surface. Static images were acquired for 200 kcts (at zoom 1) in 1024 × 1024 pixels with different separation geometries. Initially, collimator was moved away by a centimeter each after acquisition up to 10 cm and later on by 2 cm. Energy and window settings used were 153Sm (103 keV, 20%), 99mTc (140 keV, 20%), 177Lu (113, 208 keV, 20%) and 131I (364 keV, 20%). Line profiles (20 pixel thick) were drawn corresponding to 10 mm thickness. FWHM in millimeters and maximum counts for each profile were noted.
Results: FWHM with LEHR collimator at surface for 153Sm, 99mTc, 177Lu were observed to be 7.5, 8.5 and 9.8 mm respectively. The same with HEGP for 177Lu and 131I were 11 and 10 mm. FWHM with LEHR for 99mTc at 1-10, 12, 14 and 15 cm distance were 8.6, 9.8, 9.6, 10.5, 11.3, 11.7, 12.2, 12.8, 13.5, 15.5, 14.0, 16.8 and 17.3 mm respectively. FWHM with LEHR for 177Lu for these distances were 9.8, 11.0, 10.5, 12.0, 13.3, 13.5, 15.8, 18.0, 15.0, 18.0, 18.0, 20.0 and 21.0 mm respectively.
Conclusions: LSF is an easy to perform method to evaluate performance characteristic of the gamma camera collimator system. Our results show the ease of rating collimators characteristics and assessing resolution characteristics with changing depths.
