Sensitivity enhancement of methacrylic acid gel dosimeters by incorporating iodine for computed tomography scans

Abstract

Purpose: Polymer gel dosimeters provide three-dimensional absorbed dose information and have gradually become a popular tool for quality assurance in radiotherapy. This study aims to incorporate iodine into the MAGAT-based gel as radiation sensitizer and investigate whether it can be used to measure the radiation dose and slice thickness for CT scans.

Methods: The nMAGAT(I) gel was doped with 0.03, 0.05, and 0.07-M iodine. The absorbed dose was delivered using a CT scanner (Alexion 16, Toshiba Medical Systems, Japan) with tube voltages of 80, 100, 120, and 135 kVp. The irradiated nMAGAT(I) gel was read using a cone beam optical CT scanner to produce dose-response curves. The nMAGAT(I) gel was used to obtain the slice sensitivity profile (SSP) and the CT dose index (CTDI) for quality assurance of CT scans.

Results: The 0.07-M iodine-doped nMAGAT(I) gel exhibited maximum sensitivity with the dose enhancement ratio of 2.12. The gel was chemically stable 24 h after its preparation, and the polymerization process was completed 24-48 h after the irradiation. For CT quality assurance, the full width at half maximum measured by the nMAGAT(I) gel matched the nominal slice thickness of CT. The CTDI at center, CTDI at peripheral, and weighted CTDI obtained by the nMAGAT(I) gel differed from those obtained by the ionization chamber by -4.2%, 3.1%, and 0.7%, respectively.

Conclusions: The nMAGAT(I) gel can be used to assess radiation doses and slice thickness in CT scans, thus rendering it a potential quality assurance tool for CT and other radiological diagnostic applications.

Keywords: CT dose index; Computed tomography; Polymer gel dosimeter; Slice sensitivity profile.