Focused Extracorporeal Pyrotherapy: Feasibility Study in Man

Abstract

A feasibility study of focused extracorporeal pyrotherapy was conducted in 50 patients. The instrument has a mobile Firing head, which is composed of multiple piezoelectric ceramics with a focal length of 320 mm. The energy focus was 10 mm high × 1.5 mm wide. A retractable and rotating central 3.5-MHz ultrasound transducer was used to localize the tissue target. A 7.5-MHz sectorial transrectal transducer was used for the prostate. The recording of the temperature curves by means of implanted thermocouples demonstrated that the apparatus was able to induce a peak temperature of 120°C in the focal zone. Heat diffusion was minimal because of the brief shot durations (0.015 to 1 second). Twenty-eight patients with benign prostatic hyperplasia were treated. There was virtually no heat diffusion to the rectum and urethra. The maximum temperature recorded in 12 patients who underwent pyrotherapy for superficial bladder tumors was 65°C. Eight patients underwent the same treatment to the kidney, and two patients were treated for liver metastases. Histologic examination of the target organs demonstrated severe tissue laceration with intense congestion and marked hyperemia on Day 0 and very early signs of necrosis on Day 2, corresponding to the dimensions of the focal area. No significant alterations in the usual laboratory values were observed apart from a transient rise in creatine phosphokinase with the longer shot durations. The side effects were skin burns. A shot duration—skin focal point distance curve can be used to avoid these adverse effects.