External Beam Radiation Therapy
External beam radiation therapy (EBRT) is delivered using a device like a linear accelerator, gamma knife, or proton machine to direct high energy radiation to the treatment area. The beams are delivered from outside of the body hence the “external” name.
Our treatment machines are able to deliver treatment using VMAT or volumetric arc therapy. This technology delivers the treatment beams in less time than on older “step and shoot” Linacs. The older machines needed to stop to deliver each radiation dose, rather than have the machine shape the beam while moving in one continuous motion while treating the patient. Our patients spend less time on the treatment table so there is less likelihood of movement during the treatment process.
Image guided radiation therapy is the procedure used for most patients treated with EBRT. Before all treatments, patients are simulated (or “simmed” for short) using a PET/CT or MRI machine. Doing so allows the treatment team to see exactly where the tumor is located so that it can be accurately treated. Before every treatment the patient is scanned to ensure the aiming point for the radiation beams is on center.
The goal of intensity modulated radiation therapy is shaping the radiation dose to fit the shape of the tumor while missing the surrounding healthy tissue. This is achieved by varying or modulating the strength of the beam so that it is strongest where it strikes the tumor and weakest near the surrounding healthy tissues. In this way the beam can be changed to conform to the 3-dimensional shape of the tumor. Each tumor is unique in shape so the advantage of IMRT is the flexibility in changing the strength and direction of the beam to closely match the shape of the tumor.
SRS and SBRT
Stereotactic radiosurgery and stereotactic body radiosurgery are extremely accurate techniques used to deliver very high doses of radiation to small tumors of the brain and body. The key difference between SRS/SBRT and traditional EBRT is the size of the dose delivered during the single treatment. The area to be treated is fully immobilized adding to the effectiveness of the treatment.
Total skin electron therapy is used to treat a skin cancer called mycosis fungoides-a type of non-Hodgkin’s lymphoma. Our clinic has the expertise to treat patients with this cancer if needed. A very low intensity radiation beam is used to treat the entire skin surface. While this treatment is very effective, it requires the patient to have their eyes, nails, and feet shielded from the radiation so that they don’t receive an excess dose.
This technique uses a radioactive source (radioactive iodine for example), to treat the site from within the body. This technique sometimes allows for a higher dose to be delivered in a relatively short space of time and requires only a single visit or a single treatment compared to multiple treatments needed for EBRT.
In some cases, intra-operative radiation therapy (radiation treatment during surgery) can be used to eliminate the need for conventional external beam treatment after surgery, and be completed in a single hospital visit. An applicator (a ball shaped probe) is put in the tumor cavity to deliver radiation to all the tissues that surrounded the tumor. Because the radiation is given inside of the breast, there are fewer side effects such as skin rashes or irritation.
MRI Guided HDR Brachytherapy
High dose rate (HDR) brachytherapy gives a bigger dose to the tumor in a shorter space of time. Using thin catheters (tubes) placed inside the tumor, the radioactive source is passed through the catheters to the tumor where it stays for a short amount of time. When the treatment is done, the catheters are taken out so nothing stays in the body. Our department uses 3T magnetic resonance imaging (MRI) for HDR brachytherapy because it provides a more complete picture of the treatment area than PET/CT alone.
Eye plaque treatments
Used to treat a number of tumors of the eye, eye plaque brachytherapy involves the placement of tiny radioactive seeds on the eyeball near the tumor in the eye. The radioactive seeds are placed inside a silicon cup that is held in place by a gold-plated cap (resembling a bottle top) that is attached to the eye. This procedure is performed under anesthesia and the eye plaques may remain in place for two to six days.