The radiation induced magnetic resonance image intensity change provides a more efficient three-dimensional dose measurement in MRI-Fricke-agarose gel dosimetry.
A detailed methodology has been developed to map the spatial dose distribution in a Fricke-agarose gel based on the radiation induced image intensity change in the gel's magnetic resonance (MR) images. Besides the linear correlation between the change in the gel's spin-lattice relaxation rate and the absorbed dose, it is shown here that the radiation induced image intensity change for T1-weighted spin-echo images with TE << TR correlates exponentially to the absorbed dose. Furthermore, at the lower dose region (< 15 Gy), the correlation is fairly linear and its sensitivity is high. The minimum detectable dose is shown to be equivalent to the one obtained using the conventional R1-based approach. Since only one T1-weighted image is required for the dose evaluation, compared to the R1-based method, the total MR imaging time can be reduced from hours to a few minutes. This extensive time reduction avoids ferric ion diffusion effects and provides a practical way to simply and effectively measure the three-dimensional dose distribution using the Fricke-agarose dosimeter gel.
Chu
W C
WC
Institute of Biomedical Engineering, National Yang Ming University, Shih-Pai, Taipei, Taiwan, Republic of China. wchu@bme.ym.edu.tw
Guo
W Y
WY
Wu
M C
MC
Chung
W Y
WY
Pan
D H
DH
D005782:Gels; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008962:Models, Theoretical; D019047:Phantoms, Imaging; D011874:Radiometry / Q000379:methods* / Q000706:statistics & numerical data; D016634:Radiosurgery; D012685:Sepharose
D005782:Gels; D012685:Sepharose