Application of Polarization-sensitive Optical Coherence Tomography in Measurement of Gel Dosimeters

Purpose: Polymer gel dosimeters have been proven to be an effective tool for verifying the three-dimensional dose distribution in radiotherapy. The radiation-induced polymerization is proportional to the absorbed dose and can be read by magnetic resonance imaging (MRI), computed tomography (CT), and optical CT on a macroscopic scale. In this study, we proposed an application of polarization-sensitive optical coherence tomography (PS-OCT) to read the reflection intensity of the gel dosimeter on a microscopic scale. Methods: The MAGAT gel was prepared with methacrylic acid (MAA) as monomers and further irradiated 0 to 12 Gy using 6 MV photon beams. The gel dosimeters were scanned by PS-OCT. The cross-section intensity image and phase retardation image were reconstructed. The maximum reflected intensity and the light attenuation rate were further evaluated as does response indexes. Results: The reflection intensity of the MAGAT gel increased with the increase in the absorbed dose and gradually saturated after exceeding 10 Gy. The linear dose range of the maximum reflected intensity was 2–8 Gy (R² = 0.999). The light attenuation rate of the MAGAT gel was also linearly correlated with the radiation dose (R² = 0.953). Conclusion: The dose response of the MAGAT gel can be read by PS-OCT on the microscopic scale. This novel scanning technique has the potential for verifying therapeutic doses for superficial tumors and skin cancers.