EVALUATION OF EFFECTS OF SCATTER AND ATTENUATION CORRECTION ON INTERNAL DOSIMETRY CALCULATION FOR RADIONUCLIDE THERAPY OF LIVER TUMOR

Abstract

Aim: It was aimed to analyse the impact of scattering and attenuation correction (AC) on lungs shunt fraction and liver components dose in 90Y dosimetry after intra-arterial injection of 99mTc-MAA.
Material and Methods: A cohort of 20 patients (F:5, M:15) was included in the current study. 99mTc-MAA activity (3-6 mCi) was intra-arterially administered to the targeted liver, followed by whole body scan (WBS) with peak-window at 140 keV (15% width), and down-scatter window. SPECT/CT scan was subsequently performed involving the lungs and liver regions with dual window scatter correction (SC). The lungs shunt fraction was calculated from the standard WBS, scatter corrected WBS, SPECT/CT with attenuation and scatter correction, and scatter corrected SPECT. The tumour and surrounding healthy tissue doses were estimated with different approaches including AC-SC (SPECT/CT), NoAC-SC (SPECT), NoAC-NoSC+LSF(SC-WBS), AC-SC+LSF (WBS), and NoAC-NoSC+LSF(WBS)
Results: It was found that the average deviation between the standard LSF and those obtained from AC-SC, NoAC-SC and SC-WBS was -50% (-29/-71), -32%(-8/-67), -45%(-13/80), respectively. The required 90Y activity (GBq/Gy) decreased by 2-11%, 1-9% and 2-7% with using LSFs from AC-SC, NoAC-SC, SC-WBS images. The tumour and surrounding healthy tissue doses were estimated as 112±90 Gy and 30±18 Gy/GBq by AC-SC (SPECT/CT), 117±108 and 30±22 by NoAC-SC (SPECT), 110±100 and 31±21 Gy/GBq by NoAC-NoSC+LSF(SC-WBS), 106±84 and 28±17 Gy/GBq by AC-SC+LSF (WBS), while they were 90±85 and 28±20 Gy/GBq by NoAC-NoSC+ LSF(WBS). Overall, no significant difference was found in the healthy tissue and tumour doses between the approaches with (p<0.05) with and without scatter correction. Whilst, a significant difference was seen in the lungs shunt fractions and lungs doses (p<0.05) between the approaches with scatter corrected LSF and the standard approach with no scatter correction.
Conclusion: It has been demonstrated that 90Y dosimetry can be used safely in case of scattering and attenuation correction to SPECT images.