Image-Guided Radiotherapy Using a Modified Industrial Micro-CT for Preclinical Applications

Area of Science:

• Medical Physics
• Preclinical Oncology
• Radiotherapy Technology

Background:

• Radiotherapy is crucial for cancer treatment but challenging in small animal models due to technical complexities and potential side effects.
• Implementing precise irradiation in preclinical studies, especially for small target volumes like the brain, is often limited.
• Existing methods may be costly or technically demanding, hindering long-term observational studies.

Purpose of the Study:

• To demonstrate the cost-effective conversion of an industrial micro-CT into a small animal image-guided radiation therapy (IGRT) device.
• To establish proof of principle for partial brain irradiation in mice using the modified micro-CT system.
• To overcome technical barriers in preclinical radiotherapy for small animal models.

Main Methods:

• A commercial industrial micro-CT scanner was repurposed with custom steel collimators (1-5 mm aperture).
• Radiation field characteristics (symmetry, flatness, penumbra) were measured using an ionization chamber, phantoms, and radiochromic films.
• A C++ treatment planning tool was developed, and proof of principle was shown via irradiation of mice with orthotopic glioblastoma.

Main Results:

• The modified system achieved high radiation field symmetry (1.04 ± 0.02%) and precise beam characteristics (penumbra 0.14-0.51 mm).
• Variable full width at half maximum (FWHM) from 1.97 to 9.99 mm was achievable based on collimator size.
• Dose rates were measured at 10.7 mGy/s (1 mm depth) and 7.6 mGy/s (5 mm depth).
• Irradiated mice tolerated the treatment well, showing central tumor necrosis indicative of therapeutic effect.

Conclusions:

• An industrial micro-CT scanner can be affordably modified for effective small animal image-guided radiation therapy (IGRT).
• This approach enables precise irradiation of critical and small target volumes, including the brain, in preclinical models.
• The developed system facilitates advanced radiotherapy research in small animals, overcoming previous technical and cost limitations.