Brachytherapy treatment planning

Modern brachytherapy offers a great deal of versatility in the selection of radionuclide sources and their precise positioning in relation to the tumor. The successful outcome of a brachytherapy treatment rests upon careful planning and the accuracy with which each step of the procedure is implemented. A slight departure for instance from proper spacing of sources may result in 'overdosage' and necrosis within the target volume or 'underdosage' of the tumor. The specification of a three-dimensional target volume was extremely difficult before the advent of computer tomography (CT), and treatment planning and computerized dose calculation methods have been largely limited to two-dimensional approaches. These conditions have now been drastically changed, and a re-evaluation of dosimetry techniques is in progress. Recent advances in diagnostic imaging methods, especially CT, permit the definition of both normal and neoplastic tissues in 3 dimensions. Recent developments in computer display technology have created the tools to manage and evaluate large amounts of information, whether diagnostic information that describes the patient's anatomy and the target volume, or calculated three-dimensional dose distributions