Teletherapy (therapy from a distance) generally refers to treatment delivered with a linear accelerator. Conformal (3D) radiotherapy and IMRT are examples of teletherapy.
Brachytherapy (close-up therapy) refers to treatment delivered with the use of radioactive sources or seeds, which may be inserted into a natural body cavity or implanted into soft tissue. High dose-rate temporary implants and permanent prostate implants are examples of brachytherapy.
Conformal Radiation Therapy
Conformal (3D) treatment planning frequently allows more accurate definition of the volume to be treated and the anatomy of critical normal structures that should be protected. If your doctor recommends 3D radiotherapy for you, you will need to have a CAT scan in conjunction with your simulation. The CAT scan images (and sometimes MRI images, as well) are electronically transferred to our treatment planning computers, where your doctor will work with dosimetrists and physicists to delineate all of the important structures (tumor and normal tissues) in each slice of the CAT scan. This information is used to determine the safest, most effective combination of radiation beams for your treatment.
Intensity Modulated Radiation Therapy (IMRT)
Intensity modulated radiation therapy (IMRT) is a specialized form of 3D radiotherapy that allows radiation to be more exactly shaped to fit your tumor. With IMRT, the radiation beam can be broken up into many beamlets, and the intensity of each beamlet can be adjusted individually. Using IMRT, it may be possible to further limit the exact amount of radiation that is received by normal tissues that are near the tumor. In some situations, this may also allow a higher dose of radiation to be delivered to the tumor, increasing the chance of a cure.
The key to making IMRT most effective is being able to localize the target volume prior to each treatment. Conventional radiation therapy techniques make use of skin marks and bone positions from x-rays. However, internal structures such as the prostate can change their position daily with respect to the skin and bones by 1 cm or more. For that reason, the treatment team in radiation oncology will sometimes insert tiny gold markers (fiducial markers) into the target region of the body (such as the prostate or breast) to help precisely locate the target for daily treatments. These markers are imaged daily prior to treatment. The accompanying software tells the therapists how to adjust patient positioning to match the treatment plan.
Image-Guided Radiation Therapy (IGRT)
Normal structures and tumor position can change from day to day due to differences in organ filling, weight changes or simply from breathing. IGRT is conformal radiation treatment guided by imaging equipment such as CT or stereoscopic X-rays, that is mounted on robotic arms on the linear accelerator. These images are taken daily before the patient is given the radiation treatment.
All IGRT patients first undergo a CT scan as part of the planning process. The digital information from the CT scan is then transmitted to the console in the treatment room to allow doctors to compare the earlier image with the images taken just before treatment. Within seconds, computer calculations determine the movements necessary to match the planned treatment fields to within a millimeter.
This allows doctors to better target the cancer while avoiding nearby healthy tissue. In some cases, fiducial markers (as described above) are implanted in or near the tumor to help localize it during IGRT.
This treatment capability allows the physician to compensate for tumor motion due to respirations. Normal tissue can be spared as the radiation beam is on only when the tumor falls within the planned treatment volume.
Stereotactic radiotherapy is a technique that allows your radiation oncologist to precisely focus small beams of radiation to destroy certain types of tumors. Since the beam is so precise, your radiation oncologist may be able to spare more normal tissue than with conventional external beam therapy. This additional precision is achieved through rigid immobilization, such as with a head frame as is used in the treatment of brain tumors. Although often performed in a single treatment, stereotactic radiotherapy can also be delivered in multiple treatments, called fractionated radiosurgery. Stereotactic radiotherapy may be the only treatment if a very small area is affected. In addition to treating cancers, it can also be used to treat malformations in the brains blood vessels and certain noncancerous (benign) brain tumors.
Some small, superficial cancers of the rectum can be treated with a specialized type of external beam radiotherapy called endorectal radiotherapy. A metal tube is inserted into the rectum, and the beam is directed down the tube onto the inside surface of the rectum. Low grade, superficial rectal cancers may respond well to this treatment, sometimes allowing the patient to avoid major surgery and colostomy.
High dose-rate (HDR) brachytherapy is very important in the treatment of vaginal, cervical and uterine cancers, and it can be incorporated into the overall treatment plan for many other tumors (sarcoma, head and neck tumors, prostate tumors) as well. HDR brachytherapy is given over the course of several minutes, using equipment that allows the tumor to be temporarily exposed to a very active radioactive seed. In the case of gynecologic cancers, a vaginal cylinder or ring and tandem apparatus may be used to deliver the treatment. If solid tissues need to be implanted, needles or catheters may be used for the treatment. You will usually be able to go home immediately after this treatment. Depending of the type of cancer you have, you may need to have several sessions of brachytherapy to cure your cancer.