Finally, HDR is one of the salvage treatment options for locally recurrent prostate cancer [24], [25], [26], [27] and [28]. There are currently two common

ways to perform dosimetry and treatment planning for prostate HDR brachytherapy, based on the image acquisition modality and its timing relative to the insertion of the brachytherapy catheters: CT-based and real-time TRUS based. Each method has advantages and disadvantages; choosing one or the other is a matter of departmental resources, site-specific logistics, experience, and personal preferences. TRUS-guided Talazoparib cell line HDR catheter insertion is the first of four steps using this method. The catheter insertion is performed under anesthesia in an operating or procedure room. After postoperative recovery, the patient is transferred to a CT scanner for Step 2 where simulation images are obtained find more and refinements of the catheter positions can be made. CT is most often used for this purpose because they are much more available and practical, although MRI scanners provide better anatomic detail of the prostate and surrounding anatomy. Once approved, the CT image data set is

transferred to a treatment planning computer for Step 3 where contours of the target and OARs are generated. Implant catheter distributions are registered and dose calculations are made to produce isodose clouds, dose volume histograms, and virtual dosimetry images. After dosimetry is reviewed and approved by the physician, the plan is uploaded to the treatment console, which transfers the source

delivery instructions to the robotic afterloader and where data about the final step, HDR treatment, are monitored. CT-based dosimetry offers excellent visualization of the brachytherapy catheters and OARs (rectum, urethra, and bladder) and it allows time for careful assessment of the dosimetry (Fig. 1). Although the prostate is more accurately contoured on TRUS, the CT scans can be fused with MRI to gather even more detailed information on key anatomic relationships. Except where dosimetry is performed in a room shielded for HDR brachytherapy, CT simulation in its current form often involves moving the patient. Therefore, the potential disadvantages of CT dosimetry are the need to move the patient and the time it takes to go from one location to another to perform serial functions. Moreover, changes in catheter ID-8 positions that occur between simulation and treatment delivery must be identified and corrected. This method uses the ultrasound images and computer planning in “real-time” to simultaneously guide brachytherapy catheter placement and to perform the dosimetry calculations. It has the advantages that the ultrasound clearly delineates; the prostate capsule and treatment can be delivered immediately afterward without moving the patient, if the implant procedure is performed in a properly shielded venue (i.e., a shielded operating room or brachytherapy suite).