External Beam Radiation Therapy

The University of Wisconsin Carbone Cancer Center offers external beam radiation therapy to patients who need it.
External beam radiation therapy can be delivered using linear accelerators (below left) or other more specialized devices such as Tomotherapy (below right).


High energy X-ray beams from these machines are aimed at the tumor from outside the body, usually treating from multiple directions to better focus the radiation on the tumor. By taking advantage of the ability to focus the radiation on the tumor and also, the fact that tumors can be more sensitive to radiation than are some normal tissues, tumors can often be selectively destroyed while limiting the effects on normal tissue or organs.

Linear accelerator
Linear accelerator
Tomotherapy machine
Tomotherapy machine


Image-guided Radiation Therapy (IGRT)


Image-guidance techniques are almost always employed when intensity modulated radiation therapy (IMRT) is being used to deliver the treatment.  Used together, IGRT and IMRT can produce a very precise, normal tissue sparing radiation therapy delivery.


Radiology scans such as CT and MRI scans are used to identify the regions of the body that need to be treated and can then be used daily to direct the radiation to these sites. Such and approach is called image guided radiation therapy (IGRT). UW Radiation Oncology has three different types of treatment machines that have build in IGRT capabilities:  Tomotherapy, TrueBeam and Viewray, with the first two employing CT scans and Viewray employing a built in MRI scanner.


In other situations, such as in the lung, tumors can move in cycle with breathing and there are imaging and other methods to synchronize the delivery of radiation to the tumor’s motion.


Intensity Modulated Radiation Therapy


Intensity modulated radiation therapy (IMRT) is an advanced form of external beam radiotherapy that treats from multiple angles while changing the size, shape and intensity of the radiation beam to conform to the size, shape, and location of the patient's tumor.


It is a method that is increasingly used for a variety of tumors because of its ability to deliver high, effective doses to the tumor while better limiting the radiation doses received by normal tissue, thus reducing the chance of side effects. However, there are some treatment situations where the precise position and extent of a tumor is not as well defined and where IMRT may not be the preferred over more standard external beam delivery approaches.


UW radiation oncology employs some of the most sophisticated, IMRT capable treatment delivery machines, including Tomotherapy and TrueBeam equipment.


Treatment Duration


Treatments are usually given five days a week and each lasts approximately 15-30 minutes, over a period of three to seven weeks. How often and how long you are treated depends upon the type of tumor.