A dosimetrically motivated pathfinding approach for non-isocentric dynamic trajectory radiotherapy.

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Technology

Background:

• Non-isocentric dynamic trajectory radiotherapy (DTRT) enables complex treatment delivery through synchronized motion.
• Current DTRT planning may not fully optimize beam paths for dosimetric advantages.
• Developing advanced planning techniques is crucial for improving radiotherapy efficacy and safety.

Purpose of the Study:

• To develop and evaluate a novel dosimetrically motivated path determination technique for non-isocentric DTRT.
• To assess the impact of this technique on treatment plan quality and delivery efficiency.
• To compare non-isocentric DTRT plans generated with the new technique against other radiotherapy modalities.

Main Methods:

• A column generation algorithm was employed to iteratively determine optimal beam paths considering all available beam directions and extended source-to-target distances.
• Direct aperture optimization was used to create deliverable intensity-modulated plans along the determined paths.
• Comparative analysis was performed using craniospinal, spinal, breast, head and neck (H&N), and esophagus cancer cases, evaluating dosimetric quality and delivery time against VMAT, isocentric DTRT, and manual non-isocentric DTRT plans.

Main Results:

• For craniospinal/spinal cases, path determination improved dose conformity but slightly reduced target homogeneity compared to manual setup.
• Non-isocentric DTRT plans achieved target coverage while reducing mean organ-at-risk dose by 1.7 Gy (breast), 1.0 Gy (H&N), and 1.6 Gy (esophagus) versus VMAT.
• Compared to isocentric DTRT, non-isocentric DTRT reduced mean organ-at-risk dose by 0.8 Gy (breast), 0.6 Gy (H&N), and 0.8 Gy (esophagus).

Conclusions:

• A general, dosimetrically motivated path determination technique for non-isocentric DTRT has been successfully developed.
• This advancement offers improved treatment planning capabilities for non-isocentric DTRT.
• The developed technique holds significant potential for optimizing radiotherapy delivery and patient outcomes.