Radiation therapy

Radiation therapy (or radiotherapy) is the medical use of ionizing radiation as part of cancer treatment to control malignant cells (not to be confused with radiology, the use of radiation in medical imaging and diagnosis). Although radiotherapy is often used as part of curative therapy, it is occasionally used as a palliative treatment, where cure is not possible and the aim is for symptomatic relief. Other rare uses are to wipe out the immune system prior to transplant to reduce the incidence of tissue rejection, called total body irradiation (TBI); to calm hyperactive muscles—such as might cause twitchy eyes—with mild superficial treatments; and to form scar tissue around a stent to reinforce the vascular wall.

3-dimensional radiation therapy

3-dimensional radiation therapy (also called 3-dimensional conformal radiation therapy) is a procedure that uses a computer to create a 3-dimensional picture of the tumor. The patient first undergoes a CT scan in the treatment position, a process known as simulation. The images from the scan are transferred to a treatment planning computer, and the physician traces the outline of the tumor and normal organs on each slice of the CT scan. The treatment planning computer allows the physician to try different beam arrangements on the patient, a process known as virtual simulation. The treatment planning computer may show the beam's eye view (BEV), which is a visual depiction of the treatment field in relation to the tumor and the bony anatomy of the patient and normal organs. Using information from the BEV, physicians can design custom blocking of parts of the radiation beam in order to spare normal tissue as much as possible, which allows doctors to give the highest possible dose of radiation to the tumor.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~