MAGIC-f Gel Dosimeter Reading: A Comparison between an In-House Optical CT and MRI Imaging

Introduction: According to new developments in radiation therapy techniques, accurate dose verification in three dimensions has become more critical. Polymer gel dosimeters (PGDs) are valuable tools to be used for this purpose. Nowadays, various imaging modalities are employed to read out the gels. This study was aimed to investigate the measured dose distribution recorded in MAGIC-f PGD with optical computed tomography (OCT) by comparison with MRI. Material and Methods: We developed an in-house charge-coupled device (CCD) based cone-beam OCT scanner. A phantom of MAGIC-f PGD was used to measure a four-field box dose distribution. MRI and OCT scanners were performed for gel readouts. Both measurement results were compared by gamma index analysis with various acceptance criteria. The temporal stability of the gel was also evaluated with the OCT readout system. Results: The percentage of isodose lines from two measured datasets agreed well together. The pass rates were ۹۹.۰۲%, ۹۶.۸%, and ۸۹.۸% with ۵%/۵mm, ۴%/۴mm, and ۳%/۳mm criteria, respectively, at the phantom's central axial slice. Conclusion: The results indicate that the performance of this OCT system is almost the same with acceptable discrepancies to the MRI as accepted standard readout modality, and it can be used for three-dimensional dose verifications.

Keywords:

Optical Tomography , Radiometry , MAGIC polymer gel , magnetic resonance imaging , Radiotherapy