AbstractID: 8627 Title: Determination of Beam Parameters For Stereotactic radiosurgery (SRS)
Thalamotomy For Treating Chronic Pain Using a Linac Accelerator
Determination of Beam Parameters For Stereotactic Radiosurgery (SRS) Thalamotomy For
Treating Chronic Pain Using a Linac Accelerator
Departments of Radiation Therapy, Medical College of Ohio, 3000 Arlington Avenue, Toledo, OH 43614-2598
Linac based SRS thalamotomy is different from conventional SRS in delivering a much larger dose (65-80 Gy) of radiation to the patient
in one setting. This dose is delivered though a very small radiation field of 5-10 mm to areas of thalamus to produce thalamic lesions which
are reliable in size, shape and location with low complication rates for further minimal invasive surgery. Measurement of beam data for
such treatments requires special attention to selection of proper ionization chamber, and setup geometry for inclusion of the lateral transport
medium in acquired beam signal. Validation of the acquired data with some theoretical technique such as MC calculation is needed to
assure that proper dose is delivered. In the present work, we report MC calculations using OMEGA beam for determining the dosimetric
parameters of a 6 MV photon for a 5, 7.5, and 10 mm field using a Varian Clinac 1800. The SRS applicators modeled are diverging
stainless steel cones built to fit in a holder attached to the head of the accelerator for beam collimation. The results of the MC calculation
are presented in comparison with measured data from water phantom using a 0.01 cc, and a 0.0023 cc ionization chamber, as well as a
diamond chamber.