The role of dose distribution gradient in the observed ferric ion diffusion time scale in MRI-Fricke-infused gel dosimetry

Ferric ion diffusion is a detrimental factor in MRI-Fricke-infused gel dosimetry. In this study, a novel approach involving MR image subtraction and a fast image-based dosimetry technique to study ferric ion diffusion effects is presented. The fast image-based approach allows studying dose profile d...

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Bibliographic Details
Published in:Magnetic resonance imaging 2002-07, Vol.20 (6), p.495-502
Main Authors: Tseng, Y.J., Chu, W.C., Chung, W.Y., Guo, W.Y., Kao, Y.-H., Wang, J., Huang, Sung-Cheng
Format: Article
Language:English
Subjects:
Biological and medical sciences
Diffusion
Ferric Compounds - radiation effects
Ferric ion diffusion
Gamma knife radiosurgery
Gels
Investigative techniques, diagnostic techniques (general aspects)
Magnetic Resonance Imaging - methods
Medical sciences
Miscellaneous. Technology
MRI-Fricke-infused gel dosimetry
Radiation Dosage
Radiation dosimetry
Radiodiagnosis. Nmr imagery. Nmr spectrometry
Sepharose - radiation effects
Stereotactic radiosurgery
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Summary:Ferric ion diffusion is a detrimental factor in MRI-Fricke-infused gel dosimetry. In this study, a novel approach involving MR image subtraction and a fast image-based dosimetry technique to study ferric ion diffusion effects is presented. The fast image-based approach allows studying dose profile degradation within minutes post-irradiation. The relationship between the rate of dose profile deterioration and dose distribution gradients can be elucidated with the improved imaging temporal resolution also. Our results showed that for a dose distribution with gradient 4 Gy/mm or higher, ferric ion diffusion causes apparent dose profile degradation in 0.5–1 h post-irradiation. For a gradual dose gradient change of 2.1 Gy/mm or smaller, dose profile degradation appears insignificant for a two-hour elapsed diffusion time. These observations agree well with the theoretical analysis of a square dependence between dose profile degradation and dose distribution gradient. Because all stereotactic radiosurgery procedures produce steep dose distributions and because the ideal “snapshot” of MR scanning cannot be achieved, knowledge of the ferric ion diffusion time scale is important in experimental designs in order to avoid potential measurement errors in MRI-Fricke-agarose gel dosimetry.
ISSN:0730-725X
1873-5894
DOI:10.1016/S0730-725X(02)00522-2