Ultrasound applicators for interstitial thermal coagulation

• Published in: IEEE transactions on ultrasonics, ferroelectrics, and frequency control ferroelectrics, and frequency control, 1999-09, Vol.46 (5), p.1218-1228
• Main Authors: Diederich, C.J., Nau, W.H., Stauffer, P.R.
• Format: Article
• Language: English
• Subjects: Acoustic transducers; Acoustics; Applicators; Biocompatibility; Biological and medical sciences; Coagulation; Computer simulation; Devices; Direct current; Diseases of the cardiovascular system; Exact sciences and technology; Fundamental areas of phenomenology (including applications); In vivo; Interstitials; Medical sciences; Medical treatment; Physics; Plastics; Radiotherapy. Instrumental treatment. Physiotherapy. Reeducation. Rehabilitation, orthophony, crenotherapy. Diet therapy and various other treatments (general aspects); Surgery (general aspects). Transplantations, organ and tissue grafts. Graft diseases; Surgical implants; Temperature distribution; Temperature measurement; Thermal effects; Tissue; Transducers; Transduction; acoustical devices for the generation and reproduction of sound; Ultrasonic applications; Ultrasonic imaging; Ultrasonic transducers; Ultrasound; Vascular surgery: aorta, extremities, vena cava. Surgery of the lymphatic vessels
• ISSN: 0885-3010; 1525-8955
• DOI: 10.1109/58.796127

Direct-coupled (DC) and catheter-cooled (CC) ultrasound applicator configurations were evaluated for high-temperature ultrasound interstitial thermal therapy (USITT) using computer simulations, acoustic beam measurements, and in vivo temperature measurements. The DC devices consist of 2.2-mm diameter tubular ultrasound transducers encapsulated within a thin biocompatible plastic coating, which can be inserted directly into the tissue. The CC devices incorporate 1.5-mm diameter tubular transducers, which are inserted within 2.2to 2.4-mm diameter plastic implant catheters and require an integrated water-cooling scheme. Simulated transient temperature profiles and cumulative thermal dose distributions indicate that each of these applicator configurations can produce target temperatures greater than 50/spl deg/C and corresponding thermal doses greater than 300 to 600 equivalent minutes at 43/spl deg/C (EM/sub 43/spl deg/C/) within 5 min at a radial depth of 1 to 1.5 cm in moderately perfused tissues. Theoretical investigations of air-cooling implemented within DC applicators demonstrated a significant enhancement of thermal penetration compared with non-cooled DC applicators, thus approaching performance attainable with CC devices. Temperature distributions achieved with DC and CC applicators in vivo were in agreement with theoretical calculations and further demonstrate that the devices are practical, sufficient power output levels can be obtained, and the angular heating profiles can be shaped or directed to protect non-targeted critical normal tissues. This preliminary study demonstrates that these interstitial ultrasound applicators have potential to provide controlled thermal coagulation and necrosis of small target regions and deserve further investigation and development for possible implementation in the treatment of benign and cancerous lesions in sites such as prostate, liver, and brain.