Common Terms used in Radiation Therapy
External Beam Radiation Therapy is a form of treatment that delivers radiation therapy using external radiation sources (as opposed to internal radiation or Brachytherapy).
CT-Simulation is the first step of the treatment planning process when your body is mapped to allow the radiation oncologist to outline the tumor and the normal tissues in 3-dimensions (3-D) for treatment planning.
3-D Conformal Radiation Treatment - the radiation oncologist uses 3-D CT scans of your body to develop a treatment plan to deliver the prescribed radiation dose to the tumor while sparing the surrounding normal tissues from radiation damage. This technique carefully shapes the radiation beam to conform with the tumor shape. This is achieved by targeting the tumor from different angles. Such treatment is delivered in about 6-10 minutes daily.
IMRT, or intensity modulated radiation therapy, is a technique that radiation oncologists use to target tumors with a varying intensity radiation beam (modulated) thus delivering a more homogeneous dose to each part of the tumor. IMRT is a 15-20 minute long daily treatment.
4-D CT Simulation is a sophisticated way to simulate tumor motion that may occur during treatment delivery. The radiation oncologist obtains a series of CT scans during the normal breathing cycle of the patient. Then the tumor and the normal organs are outlined on the moving CT images. Then the treatment volumes are determined to account for the positional and shape changes of tumor and organs due to breathing. This minimizes the risk of radiation effects on normal tissue.
Respiratory Gating - the radiation beam is started and stopped as necessary to target tumor that are effected by the patients breathing motion.
IGRT ( image-guided radiation ) - XR or CT scan is obtained using the treatment machine to analyze the picture of the tumor, or target, and the surrounding tissues to allow the radiation oncologist to adjusts the treatment parameters before each and every treatment is delivered.
SRS (stereotactic radiosurgery) is a technique that is used to treat tumors in the brain. Though it is a non-invasive, non-surgical treatment, the effectiveness of SRS compares so favourably with surgical resection of brain tumors thus it has been named radiosurgery.
Combined Modality Treatments are delivered jointly by medical and radiation oncologists
- Neo-Adjuvant Chemotherapy is given to the patients before radiation therapy to shrink tumors
- Concurrent Chemotherapy with Radiation Therapy can more effectively treat certain cancer types
- Adjuvant chemotherapy is given after surgery or after radiaiton therapy to maximize chance for cure
SBRT (stereotactic body radiation therapy) , is a similar non-surgical radiation technique to brain-SRS and used for targets that are outside the brain. The term radiosurgery is used because SBRT has been favourably compared to surgical resection of tumors as far effectiveness of local tumor control. SBRT is most commonly used to treat tumors of the spine, liver, pancreas and is typically delivered in 3 to 5 radiation treatment sessions. Each session is about 30-40 minute long.
Internal Radiation Therapy ( Brachytherapy ) - treats cancer by placing radioactive seeds directly into or next to the tumor inside the body. This technique is a highly successful treatment option for cancers of the prostate, cervix, endometrium, breast, skin, bronchus, esophagus, and head/neck, as well as soft-tissue sarcomas and several other types of cancer. It is used as a single modality treatment or in combination with External Beam Radiotherapy[y. There are two types of Brachytherapy: LDR and HDR.
LDR (Low Dose Rate Brachytherapy) - uses small, about 2 mm long radioactive seeds that are permanently implanted in the body during an outpatient surgical procedure. The implanted seeds emit radiation with a gradually and slowly reducing strength in a few weeks then they no longer emit radiation. This technique is commonly used to treat prostate cancer.
HDR (High Dose Rate Brachytherapy) - is a very adaptable, conformal, intensity modulated radiation treatment. HDR uses very higher-strength radioactive sources compared to LDR. As opposed to LDR, these sources are only implanted in the body temporarily. First, narrow catheters are placed inside the tumor during an outpatient minimally invasive procedure. Then the 1 mm diameter catheters are after-loaded with the high strength Iridium radioisotope. This robotic radiation treatment delivery takes only 5-10 minutes. Some treatments are delivered using dedicated applicators to hold the isotope in place during the short HDR treatments. Then the applicators are carefully removed and the patient is discharged home. Some treatments are repeated over a period of 5 days before the narrow plastic catheters are removed after the last HDR treatment. The patient is not hospitalized, this is an outpatient treatment.
Non-sealed Radioisotope Treatment is a unique form of internal radiation treatment - it is an xcellent option for some patients with advanced cancers who suffer from pain due to wide-spread painful bone metastases that can be treated with injectable radioisotopes (Samarium, Stroncium) to aid in pain control. Oral capsule radio-iodine is the treatment of choice for patients with differentiated thyroid cancer after thyroidectomy.
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