| At present, most clinics make use of traditional dosimetry techniques such as 1D (e.g. ion chamber, TLD) or 2D (e.g. film) dosimetry systems, which lack the capability of efficiently providing the integrated dose information throughout a clinically relevant volume with adequate spatial resolution. Modern radiation therapy is characterized by more elaborate and customized treatments, utilizing advanced delivery techniques such as 3D conformal and Intensity Modulated Radiation Therapy (IMRT), having highly conformal dose-distributions with steep-dose gradients. The rapid advancement in radiation planning and delivery techniques has outpaced the corresponding means to adequately and accurately verify these treatments, and has emphasized the importance of a 3D dosimetry system to characterize and advance the growth of these new technologies. Gel dosimetry was used together with MRI to measure 3D absorbed dose distributions in radiation therapy. Radiation-induced polymerization of acrylic monomers dissolved in an aqueous gel produces a permanent, self-developing 3D image of dose distributions that can be appreciated visually or measured quantitatively by MRI scanning. A mathematical formalism was developed and numerical solutions generated that provide time-optimized MR sequence parameters for volumetric acquisition of polymer gels. We investigated the limitations of the 3D dosimetry system where we made use of the commercially available BANG gel dosimeter by irradiating gels in several clinical relevant beam geometries and compared these to more established measurement methodologies (e.g. film, ion chamber) as well as calculations. To facilitate the testing and analysis of the 3D dosimetry system, a 3D data analysis package and custom phantoms were developed. |
