In vivo photoacoustics and high frequency ultrasound imaging of mechanical high intensity focused ultrasound (HIFU) ablation

Abstract

Abstract:The thermal effect of high intensity focused ultrasound (HIFU) has been clinically exploited over a decade, while the mechanical HIFU is still largely confined to laboratory investigations. This is in part due to the lack of adequate imaging techniques to better understand the in-vivo pathological and immunological effects caused by the mechanical treatment. In this work, we explore the use of high frequency ultrasound (US) and photoacoustics (PA) as a potential tool to evaluate the effect of mechanical ablation in-vivo, e.g. boiling histotripsy. Two mice bearing a neuroblastoma tumor in the right leg were ablated using an MRI-HIFU system conceived for small animals and monitored using MRI thermometry. High frequency US and PA imaging were performed before and after the HIFU treatment. Afterwards, the tumor was resected for further assessment and evaluation of the ablated region using histopathology. High frequency US imaging revealed the presence of liquefied regions in the treated area together with fragmentized tissue which appeared with different reflecting proprieties compared to the surrounding tissue. Photoacoustic imaging on the other hand revealed the presence of deoxygenated blood within the tumor after the ablation due to the destruction of blood vessel network while color Doppler imaging confirmed the blood vessel network destruction within the tumor. The treated area and the presence of red blood cells detected by photoacoustics were further confirmed by the histopathology. This feasibility study demonstrates the potential of high frequency US and PA approach for assessing in-vivo the effect of mechanical HIFU tumor ablation.

Real-time assessment of high-intensity focused ultrasound heating and cavitation with hybrid optoacoustic ultrasound imaging

“…These ablation techniques generally do not involve acoustic cavitation events, although vaporization may be produced at high temperatures [7] . Tissue destruction can also result in alteration of mechanical properties that are readily visible in the US images, which can further reveal the presence of liquefied regions, tissue disruption or blood flow changes via color Doppler imaging [49] . The hybrid OPUS monitoring approach suggested in this work can thus enhance the capabilities of OA for monitoring a multitude of thermal treatments.…”

“…Being based on optical absorption at multiple wavelengths, multi-spectral OA tomography further enables spectroscopic differentiation of coagulated tissues resulting from HIFU or other ablation methods [45] , [46] , [47] . Vessel disruption [48] and consequent accumulation of deoxygenated blood [49] could also be observed with OA. Thermometry and monitoring during HIFU treatments have been realized with different OA systems and methods [46] , [50] , [51] , [52] , [53] , [54] .…”

Listening to tissues with new light: recent technological advances in photoacoustic imaging

“…PAT-enhanced robotic surgical system is promising for guiding endonasal and fetal surgery with high precision (247,248,250,271). Temperature mapping is another focus of PAT's treatment guidance, especially for HIFU ablation and interstitial laser phototherapy (136,253,254,272).…”

Small PLGA nanocapsules Co-encapsulating copper sulfide nanodots and fluorocarbon compound for photoacoustic imaging-guided HIFU synergistic therapy

“…21 Importantly, it has been conrmed that PAI techniques can be integrated with HIFU ablation techniques, which could help doctors to detect the location of the target tumor tissues and therefore perform HIFU ablation procedures with more accuracy. [22][23][24] Moreover, to promote therapeutic efficacy, several HIFU SAs containing PA contrast agents have been successfully fabricated. [25][26][27][28] For example, Zhang et al designed, fabricated, and applied peruorohexaneincorporated hollow mesoporous Prussian blue nanoparticles (HMPBs), which resulted in both sensitive and precise PAI and the simultaneous enhancement of HIFU therapy.…”