Poster - Thur Eve - 61: A dosimetric comparison between single-arc and double-arc prostate VMAT plans.

Area of Science:

• Radiation Oncology
• Medical Physics
• Radiotherapy Planning

Background:

• Volumetric Modulated Arc Therapy (VMAT) is a modern radiotherapy technique.
• Optimizing dose delivery for prostate cancer while sparing critical organs like the rectum is crucial.
• Single-arc and double-arc VMAT techniques present different dosimetric characteristics.

Purpose of the Study:

• To compare the dosimetry of single-arc versus double-arc VMAT for prostate cancer treatment.
• To evaluate the impact of arc technique on planning target volume (PTV) coverage and rectal dose.
• To analyze dose profiles and monitor unit requirements for both techniques.

Main Methods:

• VMAT plans (single-arc and double-arc) were created for five prostate cancer patients.
• Dosimetric analysis included dose-volume histograms and specific dose criteria (PTV D99%, rectum D30%, D50%).
• Dose profiles were analyzed, and monitor units (MUs) were calculated using Eclipse with RapidArc.

Main Results:

• Double-arc VMAT demonstrated improved PTV coverage and better rectal sparing across all patients.
• Dose profiles showed a lateral shift in the anterior-posterior direction with the double-arc technique.
• The double-arc technique required approximately 20% more MUs and nearly double the treatment time.

Conclusions:

• The double-arc VMAT technique is superior to single-arc for prostate cancer dosimetry, providing enhanced target coverage and organ-at-risk sparing.
• The increased MUs and treatment time are justified by the dosimetric benefits, especially in complex cases.
• Double-arc VMAT should be considered for prostate cancer patients when single-arc techniques fall short of dose criteria.