Gel dosimeters for radiotherapy: an introductory review

A major challenge in radiotherapy treatment is to deliver precise dose of radiation to the tumor with minimum dose to the healthy normal tissues. Recently, gel dosimetry has emerged as a powerful tool to measure three-dimensional [3D] dose distribution for complex delivery verification and quality assurance. Dosimeters currently in use are inadequate for clinical use as they measure one-dimensional [e.g. ion chambers] or two-dimensional [e.g. Radiographic films] dose distribution. There are basically two types of gel dosimeters i.e. Fricke and polymer gels. Fricke gel dosimeters are easy to prepare and are tissue equivalent but their use is limited because of dependence on oxygen concentration. Polymer gels are also sensitive to oxygen contamination however different formulations are used to solve this problem. The review summarizes improvements in gel dosimeter models and different gel compositions that had been proposed. These dosimeters act both as a phantom and detector, thus confirming the versatility of dosimetry technique. In this review imaging techniques most widely used for gel dosimeters. Magnetic Resonance Imaging, X-ray and Optical Computed Tomography shall be evaluated along with their limitations and sensitivity of gels