Apparatus-dependent dosimetric differences in spine stereotactic body radiotherapy

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Technology

Background:

• Spine stereotactic body radiotherapy (SBRT) requires precise dose delivery to tumors while sparing critical structures.
• Apparatus-dependent variations in dose distribution can impact treatment outcomes and safety in spine SBRT.

Purpose of the Study:

• To investigate and quantify apparatus-dependent dose distribution differences in spine SBRT treatment planning.
• To compare various radiotherapy systems, including robotic radiosurgery, intensity modulated protons, and different multileaf collimator (MLC) configurations for intensity-modulated radiation therapy (IMRT) and volumetric arc therapy (VMAT).

Main Methods:

• Systematic treatment planning for targets involving one to three thoracic vertebral bodies.
• Contouring of esophagus and spinal cord as organs at risk.
• Evaluation of image-guided robotic radiosurgery (CK), intensity modulated protons (IMP), fixed-field IMRT (5mm, 4mm, 2.5mm MLC), and intensity modulated volumetric arc therapy (IMVAT) (2.5mm MLC).

Main Results:

• All evaluated systems met acceptable treatment planning constraints.
• Fixed field IMRT (2.5mm MLC), IMVAT, and IMP systems demonstrated the lowest maximum dose to planning target volumes (PTVs).
• The 2.5mm MLC 9-field IMRT, IMVAT, and CK plans delivered the least dose to critical organs at risk (spinal cord and esophagus). CK plans showed the highest target dose inhomogeneity.

Conclusions:

• Apparatus choice significantly influences dose distribution in spine SBRT.
• Increased treatment complexity (more vertebral bodies) favors systems with more beams and finer MLCs.
• Benchmarking physical dose distributions is crucial for multi-institutional spine SBRT clinical trials.