External Beam Therapy
External Beam Therapy is delivered using a Linear Accelerator and a variety of treatment planning modalities, specifically 3D Conformal Therapy, Intensity Modulated Radiation Therapy (IMRT), Volumetric Modulated Arc Therapy (VMAT), Stereotactic RadioSurgery (SRS), Stereotactic RadioTherapy (SRT), and Stereotactic Body RadioTherapy (SBRT). All of these modalities benefit from Image Guided Radiation Therapy (IGRT). IGRT incorporates kV imaging into therapy procedures by providing high resolution, low dose imaging in the treatment room. This provides clinicians with patient specific imaging techniques that are used to make fast and accurate decisions on the patient position before treatment and can be used for patient monitoring during treatment.
IMRT, or Intensity Modulated Radiation Therapy, is a cancer treatment method that delivers doses of radiation directly to cancer cells in a very targeted way, much more precisely than is possible with conventional radiotherapy. IMRT can be used to treat tumors that might have been considered untreatable in the past due to close proximity to vital organs and structures.
With IMRT, the radiation dose is designed to conform to the three-dimensional shape of the tumor by modulating - or controlling - the intensity of the radiation beam to focus a higher radiation dose on the tumor, while minimizing radiation exposure to surrounding normal tissues. Treatment is carefully planned by using 3-D computed tomography (CT) images of the patient, in conjunction with computerized dose calculations that determine the dose intensity pattern which will best conform to the tumor shape while avoiding the specified organs at risk.
IMRT is being used extensively to treat a variety of cancers. It can be used as part of a treatment plan for patients with prostate cancer, head and neck cancer, lung cancer, gynecologic cancers, brain tumors and leukemia.