Development of a Photon-Counting Based Multi-Energy Small Animal CBCT to Improve Radiation Dose Calculation Accuracy in Preclinical Radiation Research
X Hu1*, Y Zhong1, K Yang2, X Jia1, (1) University of Texas Southwestern Medical Center, Dallas, TX, (2) Harvard Medical School, Massachusetts General Hospital, Boston, MA
Presentations
TH-A-207-2 (Thursday, 7/14/2022) 7:30 AM - 8:30 AM [Eastern Time (GMT-4)]
Room 207
Purpose: Cone beam CT (CBCT) in preclinical small animal irradiation platforms provides essential information needed for image guidance and radiation dose calculation for experiment planning. This project developed a photon-counting detector (PCD)-based multi(3)-energy (ME-)CBCT on a small animal irradiator to improve accuracy of material differentiation and dose calculation, compared to conventional flat panel detector (FPD)-based CBCT.
Methods: We designed a mechanical structure to mount a PCD to an existing preclinical irradiator platform and a data acquisition pipeline to acquire x-ray projection data with a 100 kVp x-ray beam with three energy thresholds in a single rotation. An energy threshold optimization scheme was implemented to determine optimal thresholds to balance signal-to-noise ratios (SNRs) among energy channels. Pixel-based detector response calibration was performed to remove ring artifacts in reconstructed CBCT images. Feldkamp-Davis-Kress (FDK) method was employed to reconstruct CBCT images and Alternative Direction Method of Multipliers (ADMM) with a total variance regularization was adapted to perform the material decomposition into bone and water. We compared dose calculation results (under a 225 kVp x-ray beam) using PCD-based ME-CBCT with that of FPD-based CBCT.
Results: The optimal nominal energy thresholds were determined as 26, 56, and 90 keV, so that SNRs in a selected region-of-interest in the background material (water) region were 6.107, 5.912 and 5.925 in the three channels respectively. In the reconstructed CBCT images, reduced image contrasts with increasing photon energies were observed without obvious beam hardening artifacts due to the narrow energy range in each channel. Average difference between measured x-ray attenuation coefficients and analytically calculated values was 10%. Radiation dose error was reduced from 49.54% to 16.35% in bone inserts and from 20.19% to 12.67% in soft tissue inserts.
Conclusion: PCD-based ME-CBCT can facilitate critical tasks in preclinical small animal irradiation researches, such as radiation dose calculations in experiment planning.
Funding Support, Disclosures, and Conflict of Interest: This study was supported in part by grants from National Institutes of Health (R37CA214639, R01CA227289).
Keywords
Photon Detectors, Cone-beam CT, Optimization
Taxonomy
IM/TH- Cone Beam CT: General (Most aspects)
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