Quantitative image feedback in TACE-combining novel imageable beads and spectral CT

Abstract

Purpose Currently, drug-eluting beads (DEB) are mixed with contrast medium and delivered together for transcatheter arterial chemoembolization (TACE). The mixture is imaged using conventional X-ray (fluoroscopy, DSA, and CBCT) to visualize DEBs deposition. However, given the fluid dynamic properties are different for the two materials (i.e. solid vs. liquid, different densities, etc.), they can separate and lead to incomplete/limited feedback of true DEB location during TACE; especially after contrast washout. Recently, imageable microspheres have been developed. While this has provided an added level of x-ray visibility, work also has been done to improve the x-ray imaging device. The purpose of this study is to show imageable bead visibility using energy-resolved CT, an emerging x-ray imaging modality allowing for material specific and quantitative imaging of contrast media [1]. Materials and Methods In a phantom study, imageable microspheres (0.1-0.3 mm) loaded with iodine containing lipiodol were embedded in agarose and scanned along with a phantom comprising distilled water and a probe filled with NaI (200 mm) as reference. Data were acquired using a spectral CT animal scanner prototype (Philips Research, Hamburg, Germany) equipped with a photon-counting detector. For comparison, conventional CT images were acquired. Results The iodine content in the microspheres showed inherent enhancement over background signal levels in the conventional CT images (CNRiodine/water=8.5). Using the spectral CT scanner and dedicated signal processing techniques, iodine maps with complete background suppression (CNRwater/air=0.08) were generated, providing a quantitative and protocol-independent measure of iodine concentration (i.e. mg/ml). Conclusion Combining imageable microspheres with the K-edge imaging capability of spectral CT allows for quantitative image feedback of administered beads. This example illustrates the importance of developing microspheres and imaging equipment that is optimized to work together and improve overall x-ray visibility.