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The Mary Hillman
Jennings
Radiation Oncology Center
Treatment Planning
"Radiation therapy treatment planning" is the process that
allows the medical physicist and dosimetrist to reconstruct, model, predict, and optimize
the total dose of radiation to tumor volumes and minimize the dose to critical structures
near the tumor.
The Mary Hillman Jennings Radiation Oncology Center is the first
clinical site in the U.S. to accept and use the ADAC Laboratories Pinnacle3 Treatment
Planning Computer System for 3-D conformal treatment planning.
- After clinical evaluation of a patient, a treatment planning CT scan of
the patient in actual treatment position is obtained. The CT scanner is networked directly
to the treatment planning system (TPS); the CT radiographic information is transmitted to
the TPS.
- The tumor volume is outlined on each CT slice. The volume is then
reconstructed in 3-D. The radiation oncologist, medical physicist, and dosimetrist use the
TPS to determine the size, shape, number, and physical characteristics of the radiation
beams best suited to a patient's treatment. This is an interactive process, using the 3-D
reconstruction to view and evaluate the dose distribution to the tumor and surrounding
tissues.
- The TPS also generates data in "Beam's Eye View" - the shape of
the tumor as viewed by the treatment machine, thus allowing the creation of field-shaping
blocks from all treatment angles. This information is used to define the shaping of the
beams using the multi-leaf collimator on the linear accelerator.
- To customize the beam shape from all angles improves the ability to
minimize unwanted radiation dose to surrounding normal tissue and focus optimally on the
tumor.
After computerized treatment planning is performed, the intended
treatment portals are localized on the Center's radiographic simulator. The portals are
then re-verified prior to the start of treatment by radiographing the patient on the
linear accelerator with the blocked treatment fields defined by the multi-leaf collimator.
The shape and localization of the treatment portals are checked radiographically each week
throughout the course of therapy.
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