Encrypted login | home

Program Information

Double-Focused Sparse Orthogonal Collimator Design for Small Animal X-Ray Irradiators

K Woods

K Woods*, D Nguyen, D Ruan, D O'Connor, K Sheng, UCLA School of Medicine, Los Angeles, CA


MO-DE-605-11 (Monday, July 31, 2017) 1:45 PM - 3:45 PM Room: 605

Purpose: Pre-clinical studies are crucial for evaluating the safety and efficacy of new radiotherapy strategies, but the irradiation techniques used are vastly different from the eventual clinical implementation. The development of advanced small animal irradiators with 3D volumetric imaging and dedicated planning systems has enabled more accurate, translatable pre-clinical studies. However, these systems lack fluence-modulating hardware and cannot perform intensity modulated radiation therapy (IMRT). We propose the design for a double-focused sparse orthogonal collimator (SOC) for small animal X-ray irradiators, with preliminary dosimetry data from our novel rectangular aperture optimization (RAO) approach.

Methods: The SOC has two orthogonal sets of leaves with two double-focused leaves in each bank. An Arduino board controls the stepper motors driving each leaf at >4 cm/sec with 0.02 mm resolution. The SOC design securely attaches to the X-ray tube of the PXI X-RAD SmART system. SOC-based IMRT can be performed using RAO for fluence map optimization with rectangular representation. RAO plans were created for highly concave targets in the mouse brain and compared to a hypothetical miniaturized multileaf collimator (MLC). Secondly, RAO plans were created based on mouse brain tumor PET signal intensity.

Results: The SOC CAD design is completed with necessary clearance and compatibility tests. A planning system based on convolution dose calculation and RAO optimization was created for the mouse scale. For the concave targets, RAO plans achieved superior dose gradient, conformality, and target dose homogeneity to the MLC plans. RAO also created simultaneous integrated doses conforming to the PET active volume, providing a positive or negative boost to the hyper-metabolic volume.

Conclusion: The proposed SOC design would enable IMRT for pre-clinical small animal studies, yielding much more clinically relevant results. Using RAO for fluence optimization, the SOC bridges a critical gap in achieving highly modulated dose distributions without complex MLC hardware.

Funding Support, Disclosures, and Conflict of Interest: DOE DE-SC0017057, NIH R44CA183390, NIH R01CA188300, NIH R43CA183390, NIH U19AI067769

Contact Email: