Related Experiment Video
Updated: Sep 16, 2025
08:34
Proton Therapy Delivery and Its Clinical Application in Select Solid Tumor Malignancies
Published on: February 6, 2019
20.5K
Collimator angle selection for prostate and lymph node volumes on the Varian halcyon machine.
Laura E O'Connor1, Marissa R Pringle1, Aubrey Buskerud1
1Medical Dosimetry Program at the University of Wisconsin - La Crosse, La Crosse, WI, 54601, USA.
Summary
This study compared two volumetric modulated arc therapy (VMAT) plans on the Halcyon linear accelerator for large pelvic volumes. Researchers found no significant difference in organ at risk sparing or plan conformity between the tested collimator angle sets.
Area of Science:
- Radiation Oncology
- Medical Physics
- Cancer Treatment
Background:
- Volumetric modulated arc therapy (VMAT) with split-jaw technique is standard on TrueBeam for complex volumes.
- The Varian Halcyon linear accelerator lacks jaws, presenting unique planning challenges for large, complex targets.
- Optimizing collimator angles is crucial for sparing organs at risk (OAR) and improving dose conformity on the Halcyon.
Purpose of the Study:
- To evaluate the effectiveness of different collimator angle selections for VMAT planning on the Halcyon.
- To determine if specific collimator angles can improve OAR sparing (rectum, bladder, small bowel) and plan conformity for large prostate and pelvic lymph node volumes (>20 cm).
Main Methods:
- Two VMAT plans (Plan A: standard angles; Plan B: Cozzi et al. angles) were created for 14 patients.
- Plans were compared retrospectively based on OAR dose metrics (rectum/bladder V40, small bowel V15) and conformity index.
- The Halcyon linear accelerator's unique MLC configuration was considered in planning.
Main Results:
- No statistically significant differences were observed between Plan A and Plan B regarding OAR sparing.
- Conformity index values were not significantly improved by either plan.
- Both tested collimator angle sets provided comparable treatment planning outcomes on the Halcyon.
Conclusions:
- The tested collimator angle sets did not yield significant improvements in OAR sparing or plan conformity for large pelvic volumes on the Halcyon.
- Further research with larger patient cohorts or alternative collimator angles may be necessary to optimize Halcyon VMAT planning strategies.
- Insights were gained into collimator angle selection for complex treatments on the Halcyon, but definitive strategies require further investigation.
