The Mary Hillman Jennings
Radiation Oncology Center

Linear Accelerator Area

This area houses the center's high energy Linear Accelerator (Linac) and control. The Linac generates low and high energy photons and a range of electron energies for treatment of tumors at any depth within the body. Typical treatment courses last from two to seven weeks, with treatment given once or twice daily.

The Linac has several digitally-controlled features that enhance the quality of the treatment delivery process.

• Multi-leaf collimation There are 58 individual "leaves" in the head of the Linac that can be moved independently to shape the radiation beam to conform with a tumor volume. The shape of the radiation field can be customized for each treatment field, depending on the shape of the tumor volume as seen from the beam's direction.

  The center's Linac is the first Siemens Medical Systems Inc. Linac with multi-leaf collimation in clinical use in the United States.

• Virtual Wedge By moving a collimator jaw across the radiation beam, the Linac can modify the penetration depth of the beam. This results in a customization of the conformation of the radiation beam to the tumor and the patient's contour.
  
  
• Verify and Record System The Linac is operated through a digitally-controlled system that monitors the functions of the Linac. All clinical data pertaining to a patient's treatment is accessed through an electronic charting system each time a patient is treated. The system downloads all treatment parameters, verifies the accuracy of the information, then monitors the actual treatment delivery. In this manner, extremely complex treatments can be administered with an extra level of safety.
  
  
• On-Line Portal Imaging This provides real-time images of the placement of the radiation therapy beam on the target volume. By having the ability to check beam positioning before treatment, potential beam misalignments can be avoided, resulting in more accurate treatment administration.

Clinically, these features allow the Radiation Oncologist to deliver standard and conformal radiation therapy. Conformal therapy is the method of shaping treatment to conform to the shape and position of a tumor. By delivering conformal therapy, the amount of radiation that is delivered to a tumor volume is increased, and radiation to normal structures decreased. This gives patients a better chance of tumor control with fewer side effects. 

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