Encrypted login | home

Program Information

Experimental Verification of Robustness Optimized Intensity Modulated Proton Therapy Plans for Craniospinal Irradiation

no image available
J Yu

J Yu1*, L Liao12 , N Sahoo1 , X Zhu1 , M Gillin1 , X Zhang1 , (1) Proton Therapy Center, UT MD Anderson Cancer Center, Houston, TX,(2)Department of Industrial Engineering, University of Houston, Houston, TX


SU-E-T-417 (Sunday, July 12, 2015) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose:The robustness-optimized intensity modulated proton therapy (RO-IMPT) plans takes into account the setup errors to eliminate the hot/cold spots caused by setup errors at the junction for craniospinal (CSI) irradiation fields. The RO-IMPT requires a large area for the junction of two fields. This work is to verify the treatment planning system calculated dose with introduction of setup errors by two-dimensional (2D) dose measurement. Two fields of total lengths of 45 cm with junctions of 21 cm were measured.

Methods:2D dose distributions in the coronal plane were measured by a commercial 2D ion-chamber-array detector in a cubic solid water phantom. A total spine field consisting of an upper and a lower spine field was measured at the depths of 5.4 and 6.9 cm. The active area for the measurement was 24x24 cm²2. The junction and the area outside the junction of the spine fields were measured separately to complete the verification for the total field. Six different amounts of set-up errors along the superior-inferior direction up to 1.4 cm were intentionally applied. The measured dose with and without set-up errors were compared with the calculated dose with and without set-up errors using Gamma-index analysis. 3%/3mm and 2%/2mm dose/distance agreement criteria were used. The point dose at the center of the junction was also compared.

Results:For all fields with various introduced setup errors, 100 % of pixels passed the 3%/3mm criteria and on average 96% of pixels passed 2%/2mm criteria. Differences in the measured and calculated doses were within 1.1%.

Conclusion:The efficacy of the robustness for the CSI RO-IMPT plans were verified by measurement. The measurement method can be used for patient treatment field specific QA for CSI RO-IMPT plans in our institution in the near future.

Contact Email: