Premium
The effect of unrealistic thyroid vertical position on thyroid dose in the MIRD phantom
Author(s) -
Lee Choonsik,
Lee Jaiki,
Lee Choonik
Publication year - 2004
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.1764702
Subject(s) - imaging phantom , thyroid , nuclear medicine , torso , medicine , dosimetry , anatomy
Anatomically, the thyroid gland is placed in the lower neck, extending from the level of the fifth cervical vertebra down to the first thoracic vertebra. However, the thyroid of the Medical Internal Radiation Dose (MIRD) phantom, which has been widely used for dosimetric calculation, is located right above the top of the torso and is completely included in the neck region. To investigate the effect of the unrealistic position of the thyroid in the MIRD phantom on dose calculation, thyroid absorbed doses at various vertical positions were calculated for the idealized external broad parallel photon beam from anterior‐posterior, posterior‐anterior, right lateral (RLAT), and left lateral (LLAT) direction using the Monte Carlo method. The thyroid absorbed dose decreased by as much as about 60% for 0.05 MeV photon in both RLAT and LLAT irradiations when the thyroid was relocated to realistic position (inserted into the torso). The effective dose also decreased by 10%, consequently. The thyroid dose of the widely accepted stylized model, the MIRD phantom, is overestimated in RLAT and LLAT irradiation geometries.