title: Monte Carlo and experimental internal radionuclide dosimetry in RANDO head phantom.
abstract: Monte Carlo techniques are widely employed in internal dosimetry to obtain better estimates of absorbed dose distributions from irradiation sources in medicine. Accurate 3D absorbed dosimetry would be useful for risk assessment of inducing deterministic and stochastic biological effects for both therapeutic and diagnostic radiopharmaceuticals in nuclear medicine. The goal of this study was to experimentally evaluate the use of Geant4 application for tomographic emission (GATE) Monte Carlo package for 3D internal dosimetry using the head portion of the RANDO phantom. GATE package (version 6.1) was used to create a voxel model of a human head phantom from computed tomography (CT) images. Matrix dimensions consisted of 319 × 216 × 30 voxels (0.7871 × 0.7871 × 5 mm(3)). Measurements were made using thermoluminescent dosimeters (TLD-100). One rod-shaped source with 94 MBq activity of (99m)Tc was positioned in the brain tissue of the posterior part of the human head phantom in slice number 2. The results of the simulation were compared with measured mean absorbed dose per cumulative activity (S value). Absorbed dose was also calculated for each slice of the digital model of the head phantom and dose volume histograms (DVHs) were computed to analyze the absolute and relative doses in each slice from the simulation data. The S-values calculated by GATE and TLD methods showed a significant correlation (correlation coefficient, r(2) ≥ 0.99, p < 0.05) with each other. The maximum relative percentage differences were ≤14% for most cases. DVHs demonstrated dose decrease along the direction of movement toward the lower slices of the head phantom. Based on the results obtained from GATE Monte Carlopackage it can be deduced that a complete dosimetry simulation study, from imaging to absorbed dose map calculation, is possible to execute in a single framework.
authors.affiliation: Medical Physics Department, Faculty of Medicine, Mashhad University of Medical Science, Pardis -e- Daneshgah, Vakil Abad Blvd., Mashhad, Iran. ghahramanasl@gmail.com.
authors.forename: Ruhollah
authors.initials: R
authors.lastname: Ghahraman Asl
authors.affiliation: Medical Physics Department, Faculty of Medicine, Mashhad University of Medical Science, Pardis -e- Daneshgah, Vakil Abad Blvd., Mashhad, Iran.|Medical Physics Research Center, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Shahrokh
authors.initials: S
authors.lastname: Nasseri
authors.affiliation: Medical Physics Department, Faculty of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran.
authors.forename: Ali Asghar
authors.initials: AA
authors.lastname: Parach
authors.affiliation: Nuclear Medicine Research Center, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Seyed Rasoul
authors.initials: SR
authors.lastname: Zakavi
authors.affiliation: Medical Physics Department, Faculty of Medicine, Mashhad University of Medical Science, Pardis -e- Daneshgah, Vakil Abad Blvd., Mashhad, Iran. momennezhadm@mums.ac.ir.|Nuclear Medicine Research Center, Mashhad University of Medical Sciences, Mashhad, Iran. momennezhadm@mums.ac.ir.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Momennezhad
authors.affiliation: Comprehensive Cancer Centers of Nevada, Las Vegas, NV, USA.
authors.forename: David
authors.initials: D
authors.lastname: Davenport
mesh_terms: D006257:Head / Q000502:physiology*; D006801:Humans; D008954:Models, Biological; D009010:Monte Carlo Method; D019047:Phantoms, Imaging; D011868:Radioisotopes / Q000737:chemistry; D011874:Radiometry / Q000295:instrumentation*; D011879:Radiotherapy Dosage
chemical_list: D011868:Radioisotopes
keywords: Absorbed dose; GATE; Internal dosimetry; RANDO phantom