Extracorporeal application of high‐intensity focused ultrasound for prostatic tissue ablation

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Abstract
Authors from Mannheim describe their experience with high‐intensity ultrasound for locally confined prostatic carcinoma. This was essentially an in vivo efficacy and safety study, as well as a clinical feasibility study. They found a positive answer to all questions asked. It will be interesting to see if further evaluation leads to a potential clinical use for this technology. A study from the Cleveland Clinic is presented, of the 2‐year follow‐up results in 34 patients who had an outpatient mid‐urethral sling using porcine small intestine submucosa. The technique is described, with cure of incontinence in 27 of the 34 women. There was no prolonged retention or erosion. OBJECTIVE: To investigate the efficacy and safety of extracorporeal prostatic tissue ablation using high‐intensity focused ultrasound (HIFU) in vivo in animals, and in a clinical feasibility study in men, as this is an investigational minimally invasive treatment alternative for locally confined prostatic carcinoma, but may have significant side‐effects. PATIENTS, MATERIALS AND METHODS: Ultrasound (1.04 MHz excitation frequency) was generated by an extracorporeal cylindrical piezo‐ceramic element and focused by a paraboloidal reflector to a focal size of 32 × 4 mm. The focal distance and aperture diameter were both 100 mm. HIFU was applied extracorporeally at different intensities and pulse duration (up to 6 s) to 11 dog prostates in vivo (median intensity 1192 W/cm 2 ) and eight patients (median intensity 3278 W/cm 2 , range 2384–3576) under general anaesthesia. The lesions were assessed macroscopically and histologically after HIFU and any side‐effects evaluated. RESULTS: Thermoablation was feasible in vivo and in all patients. Macroscopic analysis and histology showed sharply demarcated coagulative necrosis. Side‐effects, including skin and rectal burns, occurred only after transvesical application in the in vivo study. There were no side‐effects in patients after perineal application. CONCLUSION: Extracorporeal HIFU is technically feasible and induces sharply demarcated tissue damage in the prostate. From the early results of this phase 1 study, the perineal approach seems to be safe.

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