Department of Radiation Physics, University of Texas M. D. Anderson Cancer Center, Houston, TX.
To describe our experiences with patient-specific quality assurance (QA) for patients with prostate cancer receiving spot scanning proton therapy (SSPT) using single-field uniform dose (SFUD).
The first group of 249 patients with prostate cancer treated with SSPT using SFUD was included in this work. The scanning-beam planning target volume and number of monitor units were recorded and checked for consistency. Patient-specific dosimetric measurements were performed, including the point dose for each plan, depth doses, and two-dimensional (2D) dose distribution in the planes perpendicular to the incident beam direction for each field at multiple depths. The γ-index with 3% dose or 3-mm distance agreement criteria was used to evaluate the 2D dose distributions.
We observed a linear relationship between the number of monitor units and scanning-beam planning target volume. The difference between the measured and calculated point doses (mean ± SD) was 0.0% ± 0.7% (range, -2.9% to 1.8%). In general, the depth doses exhibited good agreement except at the distal end of the spread-out Bragg peak. The pass rate of γ-index (mean ± SD) for 2D dose comparison was 96.2% ± 2.6% (range, 90-100%). Discrepancies between the measured and calculated dose distributions primarily resulted from the limitation of the model used by the treatment planning system.
We have established a patient-specific QA program for prostate cancer patients receiving SSPT using SFUD.
Zhu XR, Poenisch F, Song X, Johnson JL, Ciangaru G, Taylor MB, Lii M, Martin C, Arjomandy B, Lee AK, Choi S, Nguyen QN, Gillin MT, Sahoo N. Are you the author?
Reference: Int J Radiat Oncol Biol Phys. 2011 Feb 5. Epub ahead of print.