Prototype Small-Animal PET-CT Imaging System for Image-guided Radiation Therapy.

Area of Science:

• Medical Physics and Imaging
• Radiation Oncology
• Molecular Imaging

Background:

• Precision targeted radiation therapy requires integrated imaging and treatment systems, but current progress is limited by a lack of such technologies.
• Molecular imaging plays a crucial role in guiding targeted radiation therapy, enhancing treatment accuracy and efficacy.

Purpose of the Study:

• To develop and evaluate a prototype positron emission tomography (PET) scanner integrated with a cone beam computed tomography (CBCT)-based small animal irradiation system.
• To demonstrate the feasibility of molecular-image-guided, targeted external beam radiation therapy using the integrated theranostic system.

Main Methods:

• Developed a PET scanner with two rotating Hamamatsu time-of-flight PET modules integrated into a CBCT small animal irradiation system.
• Characterized the PET system's performance using phantom studies (NEMA NU 4-2008) and in-vivo imaging of colorectal cancer in mice using 64Cu-DOTA-M5A.
• Compared the prototype system's performance with a commercial Siemens Inveon PET/CT system and created Monte Carlo-based radiation treatment plans.

Main Results:

• The prototype PET system demonstrated good energy (12.9% at 511 KeV) and timing (283.6 ps) resolution, with spatial resolutions of 2.6 mm × 2.6 mm × 1.6 mm.
• Phantom imaging resolved cylindrical volumes as small as 3 mm, and in-vivo imaging comparable to a commercial system for tumor detection (location, size, shape).
• Demonstrated successful creation of targeted radiation treatment plans based on 64Cu-DOTA-M5A PET/CT images, escalating dose to active tumor regions while sparing normal tissue.

Conclusions:

• The integrated PET/CBCT system is a feasible prototype for molecular-image-guided radiation therapy in small animal models.
• The system enables precise targeting of tumors based on molecular imaging, allowing for dose escalation to biologically active volumes.
• This theranostic approach holds promise for advancing precision oncology through integrated imaging and targeted treatment delivery.