E Henry¹*, M Strugari^2,3, G Mawko^2,4,5,6, K Brewer^2,3,6,7, D Liu⁹, A Gordon¹⁰, J Bryan¹¹, C Maitz¹¹, R Abraham^6,8, S Kappadath¹, A Syme^2,4,5, (1) Department of Imaging Physics, University of Texas MD Anderson Cancer Centre, Houston, TX, USA, (2) Department of Physics and Atmospheric Science, Dalhousie University, Halifax, NS, Canada, (3) Biomedical Translational Imaging Centre, Halifax, NS, Canada, (4) Department of Medical Physics, Nova Scotia Health Authority, Halifax, NS, Canada, (5) Department of Radiation Oncology, Dalhousie University, Halifax, NS, Canada, (6) Department of Diagnostic Radiology, Dalhousie University, Halifax, NS, Canada, (7) Department of Biomedical Engineering, Dalhousie University, Halifax, NS, Canada, (8) ABK Biomedical Inc., Halifax, NS, Canada, (9) School of Biomedical Engineering, University of British Columbia, Vancouver, BC, Canada, (10) Department of Radiology, Northwestern University, Chicago, IL, USA, (11) Department of Veterinary Medicine and Surgery, University of Missouri, Columbia, MO, USA

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  E Henry

WE-E-202-5 (Wednesday, 7/13/2022) 11:15 AM - 12:15 PM [Eastern Time (GMT-4)]

Room 202

Purpose: Perform precision dosimetry in yttrium-90 (⁹⁰Y) radioembolization through CT imaging of radiopaque microspheres in a rabbit liver model and compare extracted dose metrics to those produced from conventional PET-based dosimetry.

Methods: A calibration phantom was designed to contain posts with nominal microsphere concentrations of 0.5 mg/mL, 5.0 mg/mL, and 25.0 mg/mL. The mean Hounsfield unit (HU) was extracted from post volumes to generate a calibration curve to relate HU to microsphere concentration. A nominal bolus of 40 mg of microspheres was administered to the livers of eight rabbits followed by PET/CT imaging. A CT-based activity distribution was calculated through the application of the calibration curve to the CT image data. Post-treatment dosimetry was performed through the convolution of ⁹⁰Y dose-voxel kernels and the PET- and CT-based cumulated activity distributions. The mean dose to the liver from the PET- and CT-based dose distributions was compared through linear regression and Bland-Altman analysis.

Results: A linear least-squares fit to the HU and microsphere concentration data derived from the calibration phantom confirmed a strong, positive correlation (r²>0.99) with a slope of 14.13 HU/(mg/mL). Linear regression demonstrated a poor correlation between the mean liver dose derived from PET- and CT-based dosimetry (r²=0.37). Bland-Altman analysis predicted that CT-based dosimetry provides, on average, a mean liver dose 15.0 Gy larger than the mean liver dose derived from PET-based dosimetry. The dose distribution within the liver was shown to be significantly more heterogeneous when implementing CT-based dosimetry relative to PET-based dosimetry with an average coefficient of variation of 1.99 and 1.02, respectively.

Conclusion: Post-treatment CT imaging of radiopaque microspheres in ⁹⁰Y radioembolization provides the means to perform precision dosimetry and extract more accurate dose metrics that can be aid in refining our understanding of the dose-response relationship in ⁹⁰Y radioembolization, which could ultimately improve future patient outcomes.

Funding Support, Disclosures, and Conflict of Interest: RA is a shareholder, cofounder, and CMO of ABK Biomedical. AS, ECH, ACG, SCK, and DL have provided consulting services to ABK Biomedical. JNB and DL have received research support from ABK Biomedical.

Keywords

Nuclear Medicine, Radiation Dosimetry

Taxonomy

IM- Nuclear Medicine General: Quantitative Imaging

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