4π non-coplanar liver SBRT: a novel delivery technique

Area of Science:

• Radiation Oncology
• Medical Physics
• Cancer Treatment

Background:

• Liver stereotactic body radiation therapy (SBRT) quality is crucial for effective cancer treatment.
• Optimizing beam delivery in SBRT is essential to minimize dose to healthy tissues.
• Volumetric modulated arc therapy (VMAT) is a current standard for liver SBRT.

Purpose of the Study:

• To develop and evaluate a novel 4π framework for optimizing non-coplanar beam orientations and fluences in liver SBRT.
• To improve dose distribution and organ-at-risk sparing in liver SBRT treatments.
• To compare the efficacy of the 4π framework against VMAT for liver SBRT.

Main Methods:

• A 4π framework with algorithms was developed to optimize non-coplanar beam orientations and fluences.
• Collision detection using CAD models ensured safe beam delivery.
• Greedy column generation optimized beam orientation and fluence maps for 10 liver SBRT cases.
• 14 and 22 non-coplanar fields were optimized to cover 95% of the PTV with 100% prescription dose.

Main Results:

• The 4π plans showed a 22% reduction in 50% dose spillage volume and a 19% reduction in integral dose compared to VMAT.
• Mean normal liver dose was reduced by 31%, with an increase in normal liver volume receiving <15 Gy by 51 cc.
• Significant reductions were observed in mean doses to kidneys (70% and 51%) and maximum doses to the stomach (67%) and spinal cord (64%).

Conclusions:

• The novel 4π non-coplanar radiation delivery technique significantly improves dose gradient.
• High dose spillage was reduced, and organ-at-risk sparing was enhanced compared to VMAT.
• This method offers a superior approach for liver SBRT quality improvement.