Abstract No. 14 - Assessment of radiopaque bead volume and distribution following hepatic TACE in swine: CBCT and MicroCT

Abstract

To compare bead visualization in vivo with cone-beam CT (CBCT) that is not optimized for radiopaque bead visualization to ex vivo microCT imaging to better inform and map true bead distribution. Swine (n = 2) underwent hepatic TACE (n = 3) using radiopaque embolic beads (70-150 µm, LC Bead LUMI) until flow stasis under fluoroscopic guidance. After embolization, in vivo CBCT at 120 kVp was performed using an Allura Xper FD20 x‐ray system (Philips, Andover, MA) with image resolution of 0.656 mm. After the procedure, the liver was resected and the embolized regions were identified under fluoroscopy and isolated. The embolized liver specimens were imaged using a Bruker SkyScan 1176 in-vivo Micro-CT with image resolution of 17.49 µm. The resulting images were segmented using a constant threshold value and registered using point registration (Mimics 19.0, Materialise, Leuven, Belgium). The volume, surface area, and length of the vessel centerlines were calculated for each segmentation. CBCT values were expressed as a percentage of microCT. Distribution of the radiopaque beads was defined on microCT and unoptimized CBCT. The visualized embolization volume and surface area using unoptimized CBCT was significantly less than that observed under microCT, 37 ± 1% (p<0.0003) and 10.3 ± 0.2% (p<0.000007) respectively. The length of the vessel centerlines on CBCT was less than on microCT, 2.6 ± 0.5% (p<0.00003). Individual beads were apparent on microCT. Standard unoptimized CBCT at 120kVp and microCT allowed for visualization of LC Bead LUMI within the hepatic vasculature after TACE. Unoptimized CBCT underestimates both the volume and distribution of radiopaque beads in hepatic tissue compared to microCT. Intra-procedural and post-procedural imaging modalities (fluoroscopy, CBCT and CT) may underestimate true embolization volume and distribution. Clinicians should be aware of the differences between clinical imaging results and the true delivery and distribution of radiopaque beads during embolization. Future work will seek to define the added conspicuity of optimized CBCT customized for LC Bead LUMI.