Doctors create a three- dimensional image of the prostate to help guide seed placement. In this image, the prostate gland is in red, the urethra in green, and the rectum in orange. Blue area shows where high-dose radiation will be delivered.
Unlike external beam radiation therapy, which delivers a high dose of radiation from outside the body, brachytherapy is a low energy type of radiation therapy in which small radioactive sources, commonly called seeds, are permanently implanted inside the tumor. On average 60 to 120 seeds are placed in a pattern specific to each patient's prostate gland, and remain there as a permanent implant. The seeds are smaller than a grain of rice, measuring only 4.5 mm in length and 0.8 mm thick. The seeds deliver most of their dose in about 4-6 months and the remainder of the dose by the end of the first year. The seeds contain temporarily radioactive material inside titanium shells. Titanium is well tolerated by the body and is used for many other procedures such as joint replacements. The seeds are permanent and cause no discomfort.
The first step in the process is an outpatient consultation with a radiation oncologist, who will work closely with the patient and his multidisciplinary team. The consultation will include a review of the medical history, imaging, and a physical examination. The radiation oncologist will then discuss the suitability of implant therapy based on PSA, Gleason score, tumor stage and other factors.
The pale purple circle on the left side of the prostate outlines the exact location of the tumor. The green circle around it shows the area of higer-dose radiation from the seeds delivered to the tumor.
Patients also undergo blood work and other preoperative studies before the day of the implant in order to be approved for anesthesia.
At the University of Maryland Medical Center, all prostate brachytherapy patients undergo blood work and other preoperative studies before the day of the implant in order to be approved for anesthesia. On the morning of the procedure, patients receive an enema to help maximize the quality of the ultrasound images. Blood thinners are discontinued prior to the procedure date to help diminish bleeding.
On the morning of the procedure, patients may receive an enema to clear out the lower part of the bowel. Patients are asked to arrive about two hours before the scheduled prostate implant. Typically the patient receives general or spinal anesthesia.
After the patient is anesthesized, an ultrasound probe is carefully placed and positioned to view the entire prostate. Axial images of the prostate, the urethra and the rectum are taken and transferred to the treatment planning computer.
The computer evaluates the exact position of the prostate and generates a three-dimensional plan that dictates the precise placement of the needles and seeds to provide exactly the amount of radiation needed to cover 100 percent of the prostate gland while limiting the amount of radiation to the normal structures (such as the urethra and the rectum).
On the day after the seed implant, doctors take a CT scan of the prostate to ensure that the seeds are properly placed. The image shows the cancerous area targeted by a higher dose of the radioactive seeds.
Using the plan, the radiation oncologist places the seeds inside the prostate. There is no surgical incision; instead, the seeds are loaded within fine needles which are inserted through the perineum (the area between the scrotum and the anus) into the prostate gland. The needle can be seen on the ultrasound image and is guided to the planned position within the prostate. It is then withdrawn, leaving the seeds at the exact locations. After the seed placement, the urologist performs a cystoscopy (a test that allows the urologists to look at the interior lining of the bladder and the urethra) to look for and remove any seeds in the bladder or the urethra and to assess whether a catheter is temporarily needed. The placement of a catheter is rare. The patient is then transferred to the recovery room. The entire procedure takes about two hours.
After the procedure, the patient will spend several hours in the recovery room. Patients generally are able to return to work within two days of discharge. Radiation exposure to other people is minimal; restrictions are recommended if the patient is returning to a setting where a newborn child, pregnant woman or young people are present.