Micro CT calibration accuracy for pre-clinical studies in ion therapy

Area of Science:

• Medical Physics
• Radiotherapy Physics
• Pre-clinical Imaging

Background:

• Accurate stopping power ratio (SPR) estimation from computed tomography (CT) is crucial for charged particle therapy (CPT) range accuracy.
• Clinical CT-based SPR calibration methods are not optimized for micro CT scanners used in small animal pre-clinical studies.
• Range uncertainties in pre-clinical CPT trials are a significant challenge.

Purpose of the Study:

• To assess the impact of different clinical SPR calibration methods on range predictions in small animal CPT pre-clinical trials.
• To evaluate SPR calibration accuracy at both voxel and organ levels using micro CT data.
• To provide a reference for SPR and range uncertainties in pre-clinical CPT research.

Main Methods:

• Small animal phantom imaging using micro CT at varying X-ray tube voltages (45-70 kV).
• Application of two single-energy CT (SECT) methods (stoichiometric and simplified) and one dual-energy CT (DECT) stoichiometric method.
• Evaluation of SPR prediction accuracy using simulated murine virtual phantoms (head, thorax, abdomen) derived from in vivo data.

Main Results:

• SECT methods demonstrated comparable accuracy in head and abdomen, with root mean squared (RMS) errors ranging from 2.31% to 5.04%.
• SECT methods showed higher RMS errors in the lung phantom (16.42% and 35.80%).
• The stoichiometric DECT method improved accuracy in the lung phantom (12.37%) and achieved 19.37% in the head and 6.42% in the abdomen.

Conclusions:

• This study provides the first report on treatment plan-agnostic, low-kV micro CT SPR calibration accuracy.
• Dual-energy CT calibration methods offer improved SPR accuracy compared to single-energy methods, especially for lung tissue.
• Findings offer a valuable reference for understanding SPR and range uncertainties in small animal CPT pre-clinical studies.