I think that you are asking about brachytherapy. This is an alternative to radiation therapy. It is done in a single session, during which many probes are inserted into the prostate through the skin. These probes are inserted using the guidance of ultrasound (and I think that this is what confused you). These probes will gradually release radiation that will treat the prostate cancer.
This technique is new in Lebanon and is available only in University medical center - Rizk Hospital (UMC-RH).
Compared to radiotherapy, it has less side effects. However, this technique has its indications and contraindications that must be discussed on a case by case basis.