Validation of MR-based polymer gel dosimetry as a preclinical three-dimensional verification tool in conformal radiotherapy

Abstract

The aim of this work was to investigate MR‐based polymer gel dosimetry as a three‐dimensional (3D) dosimetry technique in conformal radiotherapy. A cylindrical container filled with polymer gel was placed in a water‐filled torso phantom to verify a treatment plan for the conformal irradiation of a mediastinal tumor located near the esophagus. Magnetic resonance spin‐spin relaxation rate images were acquired and, after calibration, converted to absorbed dose distributions. The dose maps were compared with dose distributions measured using radiographic film. The average root‐mean‐square structural deviation, for the complete dose distribution, amounted to less than 3% between gel and film dose maps. It may be expected that MR gel dosimetry will become a valuable tool in the verification of 3D dose distributions. The influence of imaging artifacts arising from eddy currents, temperature drift during scanning, and B1 field inhomogeneity on the dose maps was taken into account and minimized. Magn Reson Med 43:116–125, 2000. © 2000 Wiley‐Liss, Inc.

Indigenously developed multipurpose acrylic head phantom for verification of IMRT using film and gel dosimetry

“…Then the R2 images of the phantom with acrylic cylindrical insert and vials were converted to dose images by applying the calibration equation. ( 18 , 19 , 20 , 21 ) It is noted that the median image filter was applied to all raw MR image data before the R2 estimation algorithm was used in the ATOM program.…”

MAGIC polymer gel for dosimetric verification in boron neutron capture therapy

“…The first two base images are affected by stimulated echoes and deviate from the mono‐exponential decay curve. ( 29 , 30 ) The script contained background exclusion by thresholding, followed by a nonlinear fit using the Levenberg–Marquart algorithm (31) to those pixels that did not belong to the background. The effectiveness of the background separation was examined visually.…”

NCS Report 25: Process management and quality assurance for intracranial stereotactic treatment

“…Unfortunately, the process of creating stable gels and anthropomorphic configurations is limited to experienced and specialized centres, which makes this tool rather cumbersome for basic dosimetry [21,40,41]. In addition, the majority of these gels require extensive use of MRI equipment for read-out, necessitating a multidisciplinary approach and close collaboration with MRI specialists.…”