High-Resolution, Small Animal Radiation Research Platform With X-Ray Tomographic Guidance Capabilities

Purpose: To demonstrate the computed tomography, conformal irradiation, and treatment planning capabilities of a small animal radiation research platform (SARRP). Methods and Materials: The SARRP uses a dual-focal spot, constant voltage X-ray source mounted on a gantry with a source-to-isocenter distance of 35 cm. Gantry rotation is limited to 120° from vertical. X-rays of 80-100 kVp from the smaller 0.4-mm focal spot are used for imaging. Both 0.4-mm and 3.0-mm focal spots operate at 225 kVp for irradiation. Robotic translate/rotate stages are used to position the animal. Cone-beam computed tomography is achieved by rotating the horizontal animal between the stationary X-ray source and a flat-panel detector. The radiation beams range from 0.5 mm in diameter to 60 × 60 mm². Dosimetry is measured with radiochromic films. Monte Carlo dose calculations are used for treatment planning. The combination of gantry and robotic stage motions facilitate conformal irradiation. Results: The SARRP spans 3 ft × 4 ft × 6 ft (width × length × height). Depending on the filtration, the isocenter dose outputs at a 1-cm depth in water were 22-375 cGy/min from the smallest to the largest radiation fields. The 20-80% dose falloff spanned 0.16 mm. Cone-beam computed tomography with 0.6 × 0.6 × 0.6 mm³ voxel resolution was acquired with a dose of <1 cGy. Treatment planning was performed at submillimeter resolution. Conclusion: The capability of the SARRP to deliver highly focal beams to multiple animal model systems provides new research opportunities that more realistically bridge laboratory research and clinical translation.