Comparison of dose decrement from intrafraction motion supine prostate radiotherapy

作者：Olsen Jeffrey R; Parikh Parag J^*; Watts Michael; Noel Camille E; Baker Kenneth W; Santanam Lakshmi; Michalski Jeff M

来源：Radiotherapy and Oncology, 2012, 104(2): 199-204.

DOI：10.1016/j.radonc.2012.06.008

• Prostate
• Radiotherapy
• Prone
• Tracking
• Calypso

Background and purpose: Dose effects of intrafraction motion during prone prostate radiotherapy are unknown. We compared prone and supine treatment using real-time tracking data to model dose coverage.
Material and methods: Electromagnetic tracking data were analyzed for 10 patients treated prone, and 15 treated supine, with IMRT for localized prostate cancer. Plans were generated using 0 mm, 3 mm, and 5 mm PTV expansions. Manual beam-hold interventions were applied to reposition the patient when translations exceeded a predetermined threshold. A custom software application (SWIFTER) used intrafraction tracking data acquired during beam-on model delivered prostate dose, by applying rigid body transformations to the prostate structure contoured at simulation within the planned dose cloud. The delivered minimum prostate dose as a percentage of planned dose (Dmin%), and prostate volume covered by the prescription dose as a percentage of the planned volume (VRx%) were compared for prone and supine treatment.
Results: Dmin% was reduced for prone treatment for 0 (p = 0.02) and 3 mm (p = 0.03) PTV margins. VRx% was reduced for prone treatment only for 0 mm margins (p = 0.002). No significant differences were found using 5 mm margins.
Conclusions: Intrafraction motion has a greater impact on target coverage for prone compared to supine prostate radiotherapy. PTV margins of 3 mm or less correlate with a significant decrease in delivered dose for prone treatment.

• 出版日期2012-8