Stereotactic Radiation Therapy

Stereotactic radiation therapy (SRT), also called stereotactic external-beam radiation therapy or stereotaxic radiation therapy, is a type of external radiation therapy that uses special equipment to position the patient and precisely deliver radiation to a tumor, with the total radiation dose divided into several smaller doses given over several days. It is used to treat brain tumors and other brain disorders and is also being studied for other cancers, such as lung cancer. What differentiates stereotactic from conventional radiotherapy is the precision of its delivery: some systems use specially designed frames physically attached to the patient's skull, while newer techniques use thermoplastic masks and highly accurate imaging systems to locate the patient, delivering high radiation doses with sub-millimetre accuracy. A fractionated variant delivered outside the brain, sometimes called stereotactic body radiotherapy, has been used to treat cancers including small cell and non-small-cell lung cancer and sarcomas that have metastasized to the lungs or liver, using several beams of varying intensity aimed from different angles at the tumor based on a four-dimensional treatment plan built from CT and MRI imaging, though the high doses involved can sometimes cause adverse effects ranging from mild rib fatigue and transient esophagitis to, rarely, fatal pneumonitis or hemorrhage.