Room: Room 202
Purpose: To evaluate the inherent radiopacity of a prototype glass microsphere produced by ABK Biomedical for use in Transarterial Radioembolization (TARE) by developing calibration curves relating Computed Tomography (CT) voxel enhancement to microsphere concentration, and to compare the inherent radiopacity to that of commercially available glass microspheres, i.e. TherasphereÂ®.
Methods: Two tissue-equivalent CT phantoms were developed using an agarose hydrogel (2% w/w) that features a funnel design to isolate microspheres deposited by micropipette. Following microsphere deposition (one phantom loaded with ABK Biomedical glass microspheres, one loaded with TherasphereÂ®), each phantom was imaged with transmission light microscopy, then with clinical CT across a range of energies (80-120 kVp), mAs values (250-500 mAs), and image reconstruction convolution kernels (Siemens B10f, B40f, and B80f). Regions of Interest (ROI) for image analysis were determined from physical measurements of microsphere distributions using microscopy. Voxel enhancement from microsphere deposition was quantified within MATLAB, and microscopy images were analyzed in ImageJ to quantify the number of microspheres/cluster.
Results: The number of deposited microspheres/cluster (for both products) ranged over two orders of magnitude (10-1500). Low-energy (80 kVp), high-intensity (450 mAs) acquisitions reconstructed with a moderately smooth kernel (B40f) resulted in calibration curves with the best fits. ABKâ€™s microspheres demonstrate greater radiopacity than the existing commercially available product, and have a greater sensitivity (steeper slope) across the measured range of microspheres concentrations.
Conclusion: These findings demonstrate the potential of using x-ray-based imaging modalities to quantify the presence of glass microspheres for high-accuracy dosimetry in TARE. Optimization of glass composition to maximize inherent radiopacity will be an important step in realizing this goal. The prototype microspheres from ABK Biomedical are more radiopaque than an existing clinical product, and future work will aim to further enhance the radiopacity.
Funding Support, Disclosures, and Conflict of Interest: RA, DB, SK are the co-founders of ABK Biomedical, Inc. ECH, GM, and AS have no financial relationship with ABK Biomedical Inc. ECH is a trainee in the Cancer Research Training Program of the Beatrice Hunter Cancer Research Institute, with funds provided by the QEll Foundation.