Imaging feedback of histotripsy treatments using ultrasound transient elastography

Histotripsy is a cavitation-based ablation therapy that mechanically fractionates soft tissues into fluid-like homogenate using high intensity short ultrasound pulses. This paper investigates the feasibility of imaging this change with ultrasound transient elastography to provide feedback for the treatments. Experiments were performed in tissue phantoms and ex vivo porcine kidneys using 3-cycle 750-kHz ultrasound pulses at peak negative/positive pressure of 17/108 MPa and a repetition rate of 50 Hz. Lesions with different degrees of fractionation were generated with increasing therapy doses from 0 to 2000 pulses per treatment location. Results showed that the lesions were detected with high sensitivity using elastography. The Young´s modulus decreased exponentially with increasing doses. Correspondingly, tissues were progressively fractionated as indicated by an exponential decrease in the percentage of remaining structurally intact cell nuclei. A good correlation existed between the lesion Young´s modulus and the degree of tissue fractionation. These results demonstrate the feasibility of detecting histotripsy lesions using ultrasound transient elastography, allowing for prediction of clinical outcomes during the treatments.