SIR 2024
Interventional Oncology
Joshua S. Ellis, MD
Resident Physician
Massachusetts General Hospital
Financial relationships: Full list of relationships is listed on the CME information page.
John Di Capua, MD, MHS (he/him/his)
Resident Physician
Massachusetts General Hospital
Financial relationships: Full list of relationships is listed on the CME information page.
Raul N. Uppot, MD
Associate Professor
Massachusetts General Hospital
Financial relationships: Full list of relationships is listed on the CME information page.
Ronald Arellano, MD (he/him/his)
Associate Professor
Massachusetts General Hospital
Financial relationships: Full list of relationships is listed on the CME information page.
Sanjeeva P. Kalva, MBBS, MD, RPVI, FSIR, FCIRSE, FACR (he/him/his)
Professor
Massachusetts General Hospital
Financial relationships: Full list of relationships is listed on the CME information page.
Thermal ablation of segment II liver lesions or upper pole renal lesions can be difficult to complete safely due to adjacent stomach or pancreas/colon respectively. Focal hydrodissection using normal saline or induced pneumoperitoneum are both limited by gravity and rapid dissipation. We proposed using the injection of a bioresorbable hydrogel to enhance hydrodissection capabilities during an ablation and demonstrate thermal protection in an in vivo swine model.
Materials and Methods:
Multiple biocompatible and resorbable GRAS (generally recognized as safe) polymers were iteratively tested to develop an injectable and triggerably degradable hydrogel. The hydrogel was assessed for thermal induction, biocompatibility, injectability, and and rheological properties. The optimal compounds were then used in 4 in vivo terminal porcine experiments approved by the institutional IACUC. In the perinephric space, multiple hydrogel variations were injected and compared to saline and assessed with CT and ultrasound for retention time. Thermal protection from microwave ablation (MWA) was tested in vivo in a live swine model. Inducible dissolution of the gel was achieved using EDTA or sodium bicarbonate.
Results:
Ex vivo the hydrogel formulation demonstrated injectability through an 18G by 20 cm Chiba needle and optimal viscosity for holding shape. Injection of EDTA demonstrated complete dissolution of the gel. The in vivoexperiments demonstrated the gel was able to stay in position for over 4 hours, significantly longer than the < 10-minute dwell time for normal saline (p< .001, T-test) in both the perinephric and intraperitoneal spaces. Moreover, the longer-lasting gel hydrodissection pocket was achieved using only 40% volume of gel compared to saline because of superior rheological properties. In a swine model, MWA was performed after gel was injected adjacent to a segment II/III liver lesion. Intra-procedure temperature at the margin was 80C in the liver with a corresponding gastric lining temperature of 37C adjacent to the stomach wall on the opposite side of the 2cm gel pocket.
Conclusion:
An injectable hydrogel can be used for thermal protection of adjacent structures for difficult-to-ablate lesions using 40% less volume of injected material while demonstrating >20x longer shape-holding ability. This same gel can then be degraded after hydrodissection is completed. Because the thermal heat capacity of the gel is higher than that of water/saline, future studies will explore the ability to shape heat using the hydrogel.