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| Treatment Questions
What is "Brachytherapy"?
Brachytherapy translates to short therapy, where the radiation is placed in or near the cancer. Because the radiation source is placed within or near the cancer, the cancer receives a very high dose, while most normal tissue receive little, if any, radiation.
The radiation source can be placed either temporarily or permanently. These sources may be placed into a cavity (endocavitary brachytherapy), within the body tissue (interstitial brachytherapy), or within the bronchus (endobronchial brachytherapy). Brachytherapy is only used for some types of cancers and may be paired with external beam radiation therapy (EBRT). When paired with external beam radiation therapy, brachytherapy is usually given after EBRT.
Temporary Sources: Defined as either Low dose rate (LDR) or High dose rate (HDR) depending on how much dose they give per minute. LDR procedures take 2 to 5 days to deliver, while HDR procedures take a few minutes. Once an adequate dose has been reached, the source is removed. Temporary LDR is used at OHSU for certain endometrial and cervical cancers (Cesium137 sources), some head and neck sites, and biliary tree cancers. Chorodial melanomas are also treated with LDR (Iodine 125 sources). HDR is used for endobronchial, esophageal, and most gynecology cancers.
Permanent Sources: These radioactive sources are placed near or within the tumor and stay there permanently. Iodine 125 or Palladium 103 are used for permanent prostate seed implants. Permanent seed placement requires 3 steps, pre-planning stage, placement of the seed, and post-implant dose calculations.
- During the pre-planning stage, an ultrasound image of the prostate is acquired. This is then used to plan the distribution of seed placement within the prostate. The plan is reviewed and approved by the doctor.
- Seed placement is an outpatient procedure. You are usually home by late afternoon.
- For the post-implant dose calculation, a CAT-scan of the pelvis is performed about one month after the implant. Based on this CAT-scan, a final dose calculation is performed.
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