Program Information
Dosimetry of a Small Field Electron Beam for Innovative Radiotherapy of Small Surface Or Internal Tumors
C Reft1*, Z Lu2 , J Noonan3 , (1) Univ Chicago, Chicago, IL, (2) University of Chicago, Chicago, IL, (3) Argonne National Laboratory, Lemont, Illinois
Presentations
SU-E-T-340 (Sunday, July 12, 2015) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose:An innovative small high intensity electron beams with energies from 6 to 12 MeV is being developed at Argonne National Laboratory to deliver an absorbed dose via a catheter to small malignant and nonmalignant lesions. This study reports on the initial dosimetric characteristics of this electron beam. These include output calibration, percent depth dose, beam profiles and leakage through the catheter.
Methods:To simulate the narrow electron beam, the Argonne Wakefield Accelerator is used to produce high energy electron beams. The electron beam from the accelerator is monitored by measuring the current through a transmission coil while the beam shape is observed with a fluorescent screen. The dosimetry properties of the electron beam transmitting through bone and tissue-like materials are measured with nanodot optically stimulated luminescent dosimeters and EDR radiographic film. The 6 MV photon beam from a Varian True beam linac is used to calibrate both the OSLDs and the film.
Results:The beam characteristics of the 12 MeV beam were measured. The properties of the small diameter, 5 mm, beam differs from that of broad clinical electron beams from radiotherapy linacs. Due to the lack of scatter from the narrow beam, the maximum dose is at the surface and the depth of the 50% depth dose is 35 mm compared to 51 mm for a clinical 12 MeV. The widths of the 90% isodose measured at the surface and depths of 2, 6, 12, and 16 mm varied from 6.6 to 8.8 mm while the widths of the FWHM isodose varied from 7.8 to 25.5 mm.
Conclusion:Initial beam measurements show favorable dosimetric properties for its use in treating either small surface or internal lesions, particularly to deliver radiation at the time of surgery to maximize the dose to the lesion and spare normal tissue.
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