Open AccessA 3D Monte Carlo method for estimation of patient-specific internal organs absorbed dose for 99m Tc-hynic-Tyr 3 -octreotide imaging
Author(s) -
Mehdi Momennezhad,
Shahrokh Nasseri,
Seyed Rasoul Zakavi,
Ali Asghar Parach,
Mahdi Ghorbani,
Ruhollah Ghahraman Asl
Publication year - 2016
Publication title -
world journal of nuclear medicine
Language(s) - English
Resource type - Journals
eISSN - 1607-3312
pISSN - 1450-1147
DOI - 10.4103/1450-1147.174700
Subject(s) - nuclear medicine , medicine , octreotide , absorbed dose , monte carlo method , single photon emission computed tomography , spect imaging , positron emission tomography , dosimetry , somatostatin , statistics , mathematics
Single-photon emission computed tomography (SPECT)-based tracers are easily available and more widely used than positron emission tomography (PET)-based tracers, and SPECT imaging still remains the most prevalent nuclear medicine imaging modality worldwide. The aim of this study is to implement an image-based Monte Carlo method for patient-specific three-dimensional (3D) absorbed dose calculation in patients after injection of (99m)Tc-hydrazinonicotinamide (hynic)-Tyr(3)-octreotide as a SPECT radiotracer. (99m)Tc patient-specic S values and the absorbed doses were calculated with GATE code for each source-target organ pair in four patients who were imaged for suspected neuroendocrine tumors. Each patient underwent multiple whole-body planar scans as well as SPECT imaging over a period of 1-24 h after intravenous injection of (99m)hynic-Tyr(3)-octreotide. The patient-specific S values calculated by GATE Monte Carlo code and the corresponding S values obtained by MIRDOSE program differed within 4.3% on an average for self-irradiation, and differed within 69.6% on an average for cross-irradiation. However, the agreement between total organ doses calculated by GATE code and MIRDOSE program for all patients was reasonably well (percentage difference was about 4.6% on an average). Normal and tumor absorbed doses calculated with GATE were slightly higher than those calculated with MIRDOSE program. The average ratio of GATE absorbed doses to MIRDOSE was 1.07 ± 0.11 (ranging from 0.94 to 1.36). According to the results, it is proposed that when cross-organ irradiation is dominant, a comprehensive approach such as GATE Monte Carlo dosimetry be used since it provides more reliable dosimetric results.