Radiopaque Shells on 90Yttrium Microspheres to Improve Radiopacity and Imaging Detection

Sunday, March 5, 2023

3:27 PM – 3:36 PM

Location: Phoenix Convention Center, 227ABC

Presenting Author(s)

Colin Woolard, MD

Resident
HCA Healthcare

Disclosure(s): No financial relationships to disclose

Author/Co-author(s)

NL

Nicole Levi-Polyachenko, PhD

Associate Professor, Plastic and Reconstructive Surgery
Wake Forest
BK

Brian Kouri, MD

Attending Physician
Wake Forest University
WD

William Dezarn, PhD

Associate Professor, Radiation Oncology
Wake Forest

Disclosure(s):

Colin Woolard, MD: No financial relationships to disclose

Purpose: To envelope Yttrium-90 Microspheres (MS) with a radiopaque shell in order to display greater contrast enhancement compared to non-coated MS.

Materials and Methods: Combine iodinated solution (IS) with 3mg/mL of chitosan in 2% acetic acid and incubate with MS on a shaker plate for 30 minutes. While shaking, add 7mL of 10mg/ml sodium tripolyphosphate (TPP) (in 100% Op) dropwise over 1 minute, and continue to shake for 30 minutes. Wash the sample by centrifuging at for 10min, then resuspend in diH₂O. Alternatively, bismuth nanoparticles were added to the chitosan solution to serve as a radiopaque contrast agent in a shell around the MS. Samples were evaluated by scanning electron microscope (SEM) and Elemental Dispersive X-Ray Spectroscopy (EDX) analysis. The amount of iodine or bismuth was quantified on the coated MS. They were then evaluated in suspension, or through infusion into porcine kidney, using cone beam CT assessment. Computational modeling was also performed to ensure that coating thickness would not impede beta emission.

Results: Cone beam CT imaging show increased contrast of coated MS compared to MS coated with chitosan only. Better contrast resolution is seen with triple coated MS using IS, although the greatest increase in contrast is observed using bismuth nanoparticles. SEM images of control MS, singe coated MS, double coated MS, and triple coated MS show progressive layering of chitosan/IS coatings, while still retaining a shell thin enough not to impede therapeutic efficacy of ⁹⁰Y. EDX elemental analysis results show a stepwise increase in iodine content with average iodine contents of 0%, 33.4%, 42.8%, and 63.0% respectively. EDX data for single bismuth nanoparticle coatings show bismuth content between 31.9-33.9%.

Conclusion: The ability to intra-operatively assess Selective Internal Radiotherapy dosage delivery would allow localization of treated and untreated regions. With this knowledge, other interventions can be applied to ensure a more efficacious treatment plan. In this study we were able to apply significant amounts of radiopaque materials to the surface of MS. With the utilization of SEM, EDX, and cone beam CT, we confirmed that we (1) successfully enveloped MS in crosslinked chitosan, (2) successfully entrapped iodinated molecules, or radiopaque bismuth nanoparticles within this chitosan shell, and (3) successfully demonstrated visibility with cone beam CT of MS with radiopaque shells.