Double-vertebral segment SBRT via novel ring-mounted Halcyon Linac: Plan quality, delivery efficiency and accuracy

Area of Science:

• Radiation Oncology
• Medical Physics
• Radiotherapy Technology

Background:

• Stereotactic body radiation therapy (SBRT) for spinal targets requires precise dose delivery.
• Single-isocenter/multi-target volumetric modulated arc therapy (SIMT VMAT) is an advanced technique for treating multiple targets simultaneously.
• The Halcyon ring delivery system (RDS) offers potential advantages in speed and accuracy for complex radiotherapy.

Purpose of the Study:

• To evaluate the plan quality, treatment delivery efficiency, and accuracy of SIMT VMAT for double-vertebral segments SBRT on the Halcyon RDS.
• To compare Halcyon RDS plans with those generated on an SBRT-dedicated Truebeam system.

Main Methods:

• Six patient cases with double-vertebral segments were replanned on Halcyon RDS using 6MV-FFF and SIMT VMAT.
• Plans were compared to retrospective Truebeam plans using identical geometry and objectives, evaluated per NRG-BR002 protocol.
• Phantom testing and independent dose verification were performed; treatment delivery parameters and portal dosimetry QA were assessed.

Main Results:

• Both Halcyon and Truebeam plans met NRG-BR002 compliance criteria with comparable target coverage and dose indices.
• Halcyon plans demonstrated significantly lower maximal and volumetric doses to organs-at-risk (OARs), including the spinal cord.
• Halcyon plans showed reduced monitor units, modulation, and overall treatment time, with higher portal dosimetry QA pass rates.

Conclusions:

• SIMT VMAT for double-vertebral segments SBRT on Halcyon RDS is feasible and dosimetrically superior to Truebeam.
• The Halcyon system provides more accurate treatment delivery and improved OAR sparing.
• Faster treatment delivery on Halcyon can enhance patient comfort, reduce motion artifacts, and improve clinical workflow efficiency.