ABSTRACT
Histotripsy is a noninvasive focused ultrasound therapy that mechanically fractionates tissue to create well-defined lesions. In a previous clinical pilot trial to treat benign prostatic hyperplasia (BPH), histotripsy did not result in consistent objective improvements in symptoms, potentially because of the fibrotic and mechanically tough nature of this tissue. In this study, we aimed to identify the dosage required to homogenize BPH tissue by different histotripsy modalities, including boiling histotripsy (BH) and cavitation histotripsy (CH). A method for histotripsy lesion quantification via entropy (HLQE) analysis was developed and utilized to quantify lesion area of the respective treatments. These data were correlated to changes in mechanical stiffness measured by ultrasound shear-wave elastography before and after treatment with each parameter set and dose. Time points corresponding to histologically observed complete lesions were qualitatively evaluated and quantitatively measured. For the BH treatment, complete lesions occurred with >=30s treatment time, with a corresponding maximum reduction in stiffness of -90.9±7.2(s.d.)%. High pulse repetition frequency (PRF) CH achieved a similar reduction to that of BH at 288s (-91.6±6.0(s.d.)%), and low-PRF CH achieved a (-82.1±5.1(s.d.)%) reduction in stiffness at dose >=144s. Receiver operating characteristic curve analysis showed that a >~75% reduction in stiffness positively correlated with complete lesions observed histologically, and can provide an alternative metric to track treatment progression.
ABSTRACT
OBJECTIVE: To evaluate simulated parastomal herniation forces in in vitro abdominal fascial models. Our group previously illustrated how incision type may play a consequential role in bowel herniation force generated across an incision using several abdominal fascia models. We sought to (1) Confirm findings in fresh human tissue, (2) Assess correlation between herniation force and incision size, and (3) Determine whether incision type impacts drainage in a simulated ex vivo ileal conduit. MATERIALS AND METHODS: Axial tension force (N) of herniation was measured using our previously published protocol, pulling a Foley catheter balloon 3.8 cm diameter affixed to a dynamometer through silicone/fascial incisions ranging 3-5.8 cm. We simulated ileal conduits using bovine small intestine with stoma matured through human fascia using 3.0 cm linear or cruciate incisions. The conduit's caudal end was catheterized and filled at 20 mL/min. Drainage was measured by pad weight change. Two-sided α < 0.05 was used to reject the null hypothesis. RESULTS: Mean (±SD) herniation forces in fresh human fascia varied significantly across linear longitudinal, linear transverse, and cruciate incisions (20.9 ± 3.7, 23.3 ± 8.8, and 8.9 ± 3.8 N, respectively [P = .011]). Fresh human fascial linear incisions 3 cm in diameter had a herniation force of 22.1 ± 6.3 vs 3.5 ± 0.7 N for 5.8 cm incisions when herniating a 3.8 cm balloon (P = .002). All observations were similar in silicone. In simulated ileal conduit, mean drainage: 70.8 ± 3.6 vs 82.1 ± 9.7 mL (linear vs cruciate) after 100 mL instilled, respectively (P = .05). CONCLUSION: This ex vivo study further suggests incision type has predictable influence on herniation force. These data support standardization of urostomy construction techniques and evaluating the clinical impact of stomal maturation techniques on parastomal hernia rates.
