Physiologically gated microbeam radiation using a field emission x-ray source array.

Area of Science:

• Medical Physics
• Radiation Oncology
• Biomedical Engineering

Background:

• Microbeam radiation therapy (MRT) utilizes narrow, high-dose radiation beams for cancer treatment, sparing normal tissues.
• Motion during MRT can degrade beam quality (e.g., lower PVDR), reducing therapeutic effectiveness.
• Carbon nanotube (CNT) x-ray sources offer a novel approach for generating microbeams for small animal studies.

Purpose of the Study:

• To incorporate physiological gating into a CNT-based microbeam radiation system.
• To minimize motion-induced blurring and preserve beam characteristics during MRT.
• To enhance the precision and practicality of CNT-based MRT for moving targets.

Main Methods:

• Utilized a CNT x-ray source array (160 kVp) collimated to a 280 μm microbeam.
• Employed a mechanical phantom and in vivo mouse models to simulate respiratory motion.
• Implemented a pressure sensor-based system to gate radiation delivery during periods of minimal motion.
• Analyzed microbeam profiles and peak to valley dose ratios (PVDR) using Gafchromic films and γ-H2Ax staining.

Main Results:

• Gated irradiation on a phantom reduced PVDR drop from 50% to 5.5% compared to non-gated conditions.
• In vivo studies demonstrated a 2.4-fold increase in PVDR with gating compared to non-gated delivery.
• Gating reduced microbeam width by approximately 40% in vivo and 38% in phantom studies.

Conclusions:

• Physiological gating synchronized with CNT x-ray sources effectively minimizes motion-induced microbeam blurring.
• Gated MRT enhances PVDR, crucial for effective treatment of moving tumors.
• This technique improves the precision and feasibility of CNT-based MRT for clinical applications.