CT scan based prostate cancer patient-specific transperineal ultrasound probe setups for image guided radiotherapy

Radiotherapy (RT) is a possible treatment modality for prostate cancer patients. The aim of RT is to irradiate tumor tissue, while sparing normal tissue as much as possible. Prior to treatment delivery, a CT scan is usually acquired, on which a treatment plan is prepared. Subsequently, the radiation dose is delivered to the patient in multiple fractions. The patients' setup prior to each of these fractions should replicate the setup during the CT scan, in order to deliver the dose to the correct location. This makes patient setup a crucial aspect of the RT workflow. It has been shown that frequent imaging during the course of the treatment (image guided RT, IGRT) can allow a more accurate patient positioning. The use of 4D ultrasound (US) imaging in these IGRT workflows is not widespread, despite the many advantages (e.g. superior soft-tissue contrast, real-time volumetric organ tracking and no extra radiation). This can be mainly attributed to the high operator dependence of this image modality. In this study, the planning CT scans of prostate cancer patients were used to calculate patient-specific transperineal US (TPUS) probe setups. The use of these setups can potentially minimize operator dependence and possibly even remove the need for a trained operator