A Tissue Phantom for Visualization and Measurement of Ultrasound-Induced Cavitation Damage

Abstract

Many ultrasound studies involve the use of tissue-mimicking materials to research phenomena invitro and predict in-vivo bioeffects. We have developed a tissue phantom to study cavitationinduced damage to tissue. The phantom consists of red blood cells suspended in an agarose hydrogel. The acoustic and mechanical properties of the gel phantom were found to be similar to soft tissue properties. The phantom's response to cavitation was evaluated using histotripsy. Histotripsy causes breakdown of tissue structures by generation of controlled cavitation using short, focused, high-intensity ultrasound pulses. Histotripsy lesions were generated in the phantom and kidney tissue using a spherically focused 1-MHz transducer generating 15 cycle pulses at a pulse repetition frequency of 100 Hz with a peak negative pressure of 14 MPa. Damage appeared clearly as increased optical transparency of the phantom due to rupture of individual red blood cells. The morphology of lesions generated in the phantom was very similar to that generated in kidney tissue, at both macroscopic and cellular levels. Additionally, lesions in the phantom could be visualized as hypoechoic regions on a B-Mode ultrasound image, similar to histotripsy lesions in tissue. High speed imaging of the optically-transparent phantom was used to show that damage coincides with the presence of cavitation. These results indicate that the phantom can accurately mimic the response of soft tissue to cavitation and provide a useful tool for studying damage induced by acoustic cavitation.

Development of Nanodroplets for Histotripsy-Mediated Cell Ablation

“…Agarose gel phantoms with an embedded red blood cell (RBCs) layer were used to demonstrate the ability of using nanodroplets to mechanically ablate tissue. 44 This phantom provides a thin, translucent red layer of RBCs as a visual indicator between the two transparent agorose gel layers that locally appears more transparent when RBCs layer is damaged. Tissue phantoms were prepared using a mixture of agarose powder (type VII; Sigma-Aldrich Co., St. Louis, Missouri, USA) and canine RBCs in 0.9% isotonic saline.…”

The influence of gas diffusion on bubble persistence in shock-scattering histotripsy

“…27 However, in vitro studies of histotripsy utilize phantoms of highly degassed agar to monitor bubble dynamics. 6,28,29 As noted in Fig. 4(A), the equilibrium diameter, and therefore the duration of bubble persistence, is reduced in degassed media compared to physiologic gas saturated media.…”

Tissue-Mimicking Phantom Useful in Simulating Laser Light-Tissue Interactions

“…Maxwell et al 3 demonstrated that HIFU-induced cavitation can be visualized using agarose hydrogel TM phantom supplemented with red blood cells (RBCs). In their study, RBC-agarose TM phantom was prepared by solidifying agarose phantom, pouring RBCs onto the agarose phantom, allowing it to solidify again, and finally, pouring agarose solution onto the RBCs-suspended agarose phantom.…”

“…In their study, RBC-agarose TM phantom was prepared by solidifying agarose phantom, pouring RBCs onto the agarose phantom, allowing it to solidify again, and finally, pouring agarose solution onto the RBCs-suspended agarose phantom. 3 Additionally, in order to simulate interactions between laser energy and hair shafts, our study group also developed a hair shaft-embedded bovine serum al-A B bumin and polyacrylamide hydrogel-based TM phantom. To do so, TM phantom was prepared by mixing polyacrylamide hydrogel and 5% (w/v) bovine serum albumin in distilled water.…”