Radiation therapy dosimetry using magnetic resonance imaging of polymer gels

Abstract

Further progress in the development of polymer gel dosimetry using MRI is reported, together with examples of its application to verify treatment plans for stereotactic radiosurgery and high dose rate brachytherapy. The dose distribution image produced in the tissue-equivalent gel by radiation-induced polymerization, and encoded in the spatial distribution of the NMR transverse relaxation rates (R2) of the water protons in the gel, is permanent. Maps of R2 are constructed from magnetic resonance imaging data and serve as a template for dose maps, which can be used to verify complex dose distributions from external sources or brachytherapy applicators. The integrating, three-dimensional, tissue-equivalent characteristics of polymer gels make it possible to obtain dose distributions not readily measured by conventional methods. An improved gel formulation (BANG-2) has a linear dose response that is independent of energy and dose rate for the situations studied to date. There is excellent agreement between the dose distributions predicted using treatment planning calculations and those measured using the gel method, and the clinical practical utility of MRI-based polymer gel dosimetry is thereby demonstrated.

Temperature and hydration effects on absorbance spectra and radiation sensitivity of a radiochromic medium

“…[1][2][3][4][5][6][7] While many of the current polymer systems are utilized for two-or three-dimensional dose representation, high spatial resolution offers potential for successful implementation in point-based measurements. Radiochromic materials commercially available in GAFCHROMIC ® films ͑International Specialty Products, Wayne, NJ͒ have the desired high spatial resolution [8][9][10] and are able to provide sufficient signal from a subcubic millimeter volume.…”

Optimisation of the MAGAT gel dosimeter compositions

“…R2 maps can be converted to dose maps using a linear dose response equation (2) that has been reported by several independent investigators (12)(13)(14) . ) 2 ( where; α is the slope of the dose-R2 curve, Ro is R2 background and R2 is R2 value of the irradiated gel.…”

Radiation dose enhancement of gold nanoparticle on different polymer gel dosimeters

“…The following imaging modalities can be used to extract the dose information within the exposed polymer gels such as OCT, MRI, X-ray CT etc. Gel dosimeters have a number of advantages, including true three-dimensional, soft tissue/water equivalence, directional independence, energy independence and it can be modified depending on the application [10][11][12][13]. Nanoparticle size ranges from 1 to 100 nm but definition includes particles up to 1µm which have also been reported.…”