Dose optimization in high-dose-rate brachytherapy: A literature review of quantitative models from 1990 to 2010

High-dose-rate brachytherapy is a form of internal radiotherapy, in which a tumor receives a temporary high dose of radiation. The treatment is commonly used in clinical practice. We discuss the literature based on the following topics: scope (interstitial or intracavitary), planning method (forward or inverse planning), objectives (in order to guarantee the right dose for the target area, critical organs and normal tissue), decision process (a priori, a posteriori or interactive), optimization techniques (exact, deterministic heuristic or stochastic heuristic method) and evaluation criteria (to measure the performance of the model results). The review serves three goals. First, we provide an overview of recent developments in the literature regarding the application of quantitative models for high-dose-rate dose optimization. Second, the classification allows to indicate recent developments in relation to each criterion and as such, provides an effective overview for researchers who are interested in a particular perspective. Finally, we want to explore opportunities for these quantitative models. We end the paper by revealing the main shortcomings in the current models: a better adaptation of clinical requirements to the mathematical model formulation, and a focus on probabilistic planning.