: This paper offers a comprehensive review of dosimetry in high dose rate brachytherapy (HDR-BT), in terms of the recent practical dosimetry techniques and systems that are utilized for radiation delivery and dosage verification. This article presents the novel models in HDR-BT for a variety of cancer including the three-dimensional (3D) image-based dose-specification techniques. The performance of HDR-BT treatment entails positioning the radioactive sources proximate to the region of interest to achieve the delivery of high radiation doses to the tumor area. Dose delivery for brachytherapy adheres to the inverse square law where rapid attenuation or dissipation in radiation results in negligible impact on the contiguous healthy tissue or organs at risk (OAR). Thus, it is critical that a sharp decline in the distribution of radiation dose proximate to the HDR source is maintained