Multibeam tomotherapy: a new treatment unit devised for multileaf collimation, intensity-modulated radiation therapy

Area of Science:

• Medical Physics
• Radiation Oncology
• Medical Imaging

Background:

• Current radiation therapy techniques, including intensity-modulated radiation therapy (IMRT), image-guided radiation therapy (IGRT), and adaptive radiation therapy (ART), aim to optimize dose delivery while minimizing toxicity.
• Achieving shorter treatment times and improved patient comfort are critical goals in the development of advanced radiation therapy systems.
• Existing systems often involve complex mechanical movements and longer treatment durations, potentially impacting patient tolerance and workflow efficiency.

Purpose of the Study:

• To propose a fully integrated system for automated multileaf collimator (MLC) based IMRT, IGRT, and ART.
• To enhance patient comfort through a novel unit design and significantly reduced treatment times.
• To develop a 'multibeam tomotherapy' approach utilizing limited beam directions and discrete patient couch motion for efficient dose delivery.

Main Methods:

• A new dual energy linac with five fixed treatment heads and a single electron beam generator is proposed, minimizing moving parts.
• Motion is restricted to MLCs, a robotic patient table, and limited gantry rotation (+/- 36 degrees).
• Flattening-filter-free treatment heads with restricted apertures combined with 'step and shoot' MLC delivery and discrete couch motion enable topographic intensity modulation.
• A 'Multifocal MLC-positioning' algorithm and an overlap strategy for adjacent fields were developed for treatment planning and optimization.
• The system incorporates a dedicated electron beam CT (TOM'AGE) and an optical topometric patient positioning system (TOPOS).

Main Results:

• Clinical case studies demonstrate a reduction in treatment time by over 50% compared to high-quality 3-D conformal and IMRT treatments, achieving treatment times of only a few minutes.
• The proposed system achieves comparable or better planning target volume coverage and improved organ-at-risk sparing.
• The mean integral dose to normal tissue is comparable to existing high-quality techniques.
• The design allows for enhanced patient positioning and image guidance features within reasonable overall treatment times.

Conclusions:

• The 'multibeam tomotherapy' concept offers a significant reduction in treatment time, enhancing patient comfort and enabling advanced IGRT/ART capabilities.
• The system's design, featuring limited motion and efficient beam delivery, provides a technically reliable and clinically advantageous approach to radiation therapy.
• This innovative design holds the potential to improve the efficiency and effectiveness of radiation oncology treatments.