Injectable radiopaque targets for cone-beam CT guided histotripsy.

Abstract

Background: Cone-beam CT (CBCT) guided histotripsy is being developed as a supplemental image guidance technique for histotripsy. The goal of this work is to present a percutaneously injectable, radiopaque target that can be used in preclinical testing of CBCT-guided histotripsy.

Methods: Livers of five in vivo swine were percutaneously injected with a mixture of barium paste diluted with saline or autologous blood to a concentration of 4:1. Post-injection CBCT images were used to analyze radiographic differences in injected volume; temporal stability of the injection (intensity, volume, and sphericity); and presence of image artifacts. Four injections were targeted and treated in vivo using a clinical histotripsy system. Injectate volume and intensity, and treatment zone size and contrast-to-noise ratio (CNR) were compared to control treatments.

Results: There was no significant difference in imaged volume or intensity between the 100 or 200 µL(p = 0.384) injection. Over the analyzed 5-206 min, the barium-saline and barium-blood injections had similar ranges of imaged volume and intensity, both changing during the first 30 min then were stable. The image artifact was reported as none to moderate in 5/6 cases for both injections. The CNR of the treatment zones and difference in diameters (planned versus actual) were 5.9 ± 1.8, 3.7 ± 1.3, and 5.9 ± 1.0 and 8.1 ± 4.0 mm, 15.9 ± 11.4 mm, and 7.6 ± 2.2 mm for the barium-saline, barium-blood and control groups respectively. The barium-saline injectate was not visible after treatment while the barium-blood was visible but dispersed.

Conclusion: Percutaneously injectable, radiopaque barium-based targets were acutely safe, targetable and treatable on CBCT and did not alter histotripsy treatment zone size in vivo.