There are several different ways to administer radiation. Some of the more common are listed below. Many new procedures are currently under investigation.
Internal
Seed implants
This method is most often used to treat prostate cancer. Radioactive seeds are implanted and placed directly on the cancer mass. The seeds are smaller than a grain of rice. Up to 150 seeds may be implanted. They work by delivering high doses of radiation directly to the tumor without affecting nearby healthy tissues. Ultrasound may be used prior to implantation to map out the tissue. The results help determine where and how many seeds will be implanted. This can be an outpatient treatment, and normal activities are usually resumed after 2-3 days.(1)
Brachytherapy
This method is most often used as a local treatment for early stage carcinomas. Sealed radioactive sources are used to deliver radiation to the tumor from a short distance. Brachytherapy may be combined with external beam radiation, depending upon the type and severity of the cancer. The two radioactive sources used are 103Pd and 125I. This treatment has been used to treat eye plaques and cancers of the prostate, lungs, brain, and female reproductive organs (uterus, ovaries, cervix).(2)
External
External Beam Radiation Therapy
This method uses large machines to produce high and low energy X-ray beams. The amount of radiation required is dependent upon the type of cancer. For example, the level of radiation necessary to destroy a skin carcinoma is less than the amount needed to treat a cancer that is located deep within the body. This treatment is offered for a large variety of cancers, and may be used alone or in conjunction with other cancer treatments, such as surgery or chemotherapy.(1)
3-D Conformal Therapy and Intensity Modulated Radiation Therapy (IMRT)
This method, which is newer and more precise than external beam, uses computer imaging to calculate the most efficient dose and combination of radiation treatments. Magnetic resonance imaging (MRI) and graphics are used to create a 3-D image of the tumor, allowing it to be distinguished from normal tissues. This technique allows a more precise mapping of the cancer and has the potential to increase the amount of radiation on the tumor and decrease the amount on normal tissue surrounding the tumor. Treatment plans are highly variable, and depend on cancer type and severity. This method is currently used to treat cancers of the prostate, head and neck, and breast.(1)
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