Leakage-Penumbra effect in intensity modulated radiation therapy step-and-shoot dose delivery

World Journal of Radiology
Grigor N Grigorov, James C L Chow

Abstract

To study the leakage-penumbra (LP) effect with a proposed correction method for the step-and-shoot intensity modulated radiation therapy (IMRT). Leakage-penumbra dose profiles from 10 randomly selected prostate IMRT plans were studied. The IMRT plans were delivered by a Varian 21 EX linear accelerator equipped with a 120-leaf multileaf collimator (MLC). For each treatment plan created by the Pinnacle(3) treatment planning system, a 3-dimensional LP dose distribution generated by 5 coplanar photon beams, starting from 0(o) with equal separation of 72(o), was investigated. For each photon beam used in the step-and-shoot IMRT plans, the first beam segment was set to have the largest area in the MLC leaf-sequencing, and was equal to the planning target volume (PTV). The overshoot effect (OSE) and the segment positional errors were measured using a solid water phantom with Kodak (TL and X-OMAT V) radiographic films. Film dosimetric analysis and calibration were carried out using a film scanner (Vidar VXR-16). The LP dose profiles were determined by eliminating the OSE and segment positional errors with specific individual irradiations. A non-uniformly distributed leaf LP dose ranging from 3% to 5% of the beam dose was measured in cl...Continue Reading

References

Oct 17, 2001·Journal of Applied Clinical Medical Physics·G A Ezzell, S Chungbin
Oct 8, 2003·Medical Physics·J E Bayouth, S M Morrill
Apr 20, 2004·Seminars in Radiation Oncology·Adam S GardenK Kian Ang
Apr 21, 2005·Medical Physics·James C L ChowAndrew Alexander
Jan 21, 2006·Physics in Medicine and Biology·Grigor N GrigorovRob B Barnett
Jun 23, 2006·Physics in Medicine and Biology·Thomas Bortfeld
Mar 1, 2011·Journal of Medical Imaging and Radiation Sciences·Craig ElithHelen M Warren-Forward

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