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SU‐FF‐T‐38: Dosimetric Characteristics of a P‐32 Conformal Source for Irradiation of Paraspinal Tumors
Author(s) -
Turcotte J,
Mauceri T,
Seco J
Publication year - 2009
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.3181510
Subject(s) - materials science , nuclear medicine , biomedical engineering , monte carlo method , irradiation , conformal map , dosimetry , spinal cord , medicine , physics , geometry , mathematics , nuclear physics , psychiatry , statistics
Purpose : A90 Y foil encased in a titanium plaque has been used to irradiate the dura for patients with paraspinal tumors. The plaque is applied to the dura intraoperatively after radiotherapy and surgery. Rapid falloff of the %DD allows the dura's surface to be treated, while sparing the spinal cord a few millimeters below. A new plaque, the RIC Conformal Source, utilizing32 P embedded in a polymeric film and bonded to a polycarbonate backing has been developed for surface irradiations. This new plaque has advantages over previous designs. The lower energy of32 P (1.709 MeV) allows for increased dose sparing of the cord over90 Y (2.28 MeV). Additionally, a longer half life of 14.28 days for32 P versus 2.67 days for90 Y , as well as a simpler manufacturing process make this new source worthy of investigation. Method and Materials : To study the dosimetric characteristics of this new plaque, a flat plaque was constructed for measurements with radiochromic film. Surface profiles and %DD were measured and compared to Monte Carlo (Penelope) data. The32 P data was also compared to the90 Y data to show viability of the new source for treatment. Surface profiles were evaluated using a Therapeutic Width Index (TWI), defined as the width of the surface profile at 90% divided by the width of the source. Results : The32 P plaque's surface profiles and %DD measurements agreed well with Penelope. Comparison of %DD showed a more rapid falloff for32 P (2.3% at 3mm) than for90 Y (14.1% at 3mm). The TWI for32 P was 0.82 and was 0.88 for the90 Y . Conclusion : Better %DD characteristics and similar surface profiles show the new plaque utilizing32 P to be clinically acceptable. Inhomogeneities in the polymeric film need to be further evaluated before clinical use of this source.