Everette C. Burdette

Transurethral ultrasound array for prostate thermal therapy: initial studies

This study presents the initial evaluation of an applicator designed for transurethral ultrasound thermotherapy (TUST) of prostate tissue in the treatment of benign prostatic hyperplasia (BPH) and cancer. A tubular multitransducer applicator, consisting of four piezoceramic tubes (2.5 mm diameter, 6 mm long, 6.8 MHz) under separate power control, was designed to fit within a semiflexible water-cooled temperature-regulated delivery catheter to be placed within the prostatic urethra during therapy. Sonication patterns were tailored to produce power depositions which avoid nontargeted tissues, such as the rectum. Computer simulations have demonstrated that 1.4-2.0 cm radial therapeutic zones (temperatures /spl ges/50-55/spl deg/C, thermal doses >300 EM/sub 43/) with concurrent sparing of the urethral mucosa can be produced within prostate tissue having blood perfusion as high as 10 kg m/sup -3/ s/sup -1/ within 15-30 min. Acoustic distributions and power output measurements of a prototype applicator have demonstrated acoustic power levels approaching 10 W per each sectored transducer segment are attainable, with beam profiles collimated within the transducer length and with desired circumferential distributions. In vivo thermal dosimetry characterizations of these transurethral applicators have indicated that therapeutic temperatures between 50 and 90/spl deg/C are attainable, controllable in the longitudinal and circumferential directions, and have effective radial heating. These results clearly indicate that transurethral ultrasound applicators have potential to provide improved spatial localization and control of the heating distribution over existing transurethral thermal therapy techniques for both hyperthermia and thermal coagulative therapy of the prostate.

Combination of transurethral and interstitial ultrasound applicators for high-temperature prostate thermal therapy

The purpose of this study was to determine the feasibility of using a transurethral ultrasound applicator in combination with implantable ultrasound applicators for inducing thermal coagulation and necrosis of localized cancer lesions or benign disease within the prostate gland. The potential to treat target zones in the anterior and lateral portions of the prostate with the angularly directive transurethral applicator, while simultaneously treating regions of extracapsular extension and zones in the posterior prostate with the directive implantable applicators in combination with a rectal cooling bolus, is evaluated. Biothermal computer simulations, acoustic characterizations, and in vivo thermal dosimetry experiments with canine prostates were used to evaluate the performance of each applicator type and combinations thereof. Simulations have demonstrated that transurethral applicators with 180-270° acoustic active zones can direct therapeutic heating patterns to the anterior and lateral prostate, implantable needles can isolate heating to the posterior gland while avoiding rectal tissue, and that the combination of applicators can be used to produce conformal heating to the whole gland. Single implantable applicators (1.8mm ODx10mm long, ∼180° active sector, ∼7MHz, direct-coupled type) produced directional thermal lesions within in vivo prostate, with temperatures >50°C extending more than 10mm radially after 10-15min. Combination of interstitial applicators (1-2) and a transurethral applicator (3-2.5mm ODx6 mm long, 180° active sector, 6.8MHz, 6 mm OD delivery catheter) produced conforming temperature distributions (48-85°C) and zones of acute thermal damage within 15min. The preliminary results of this investigation demonstrate that implantable directional ultrasound applicators, in combination with a transurethral ultrasound applicator, have the potential to provide thermal coagulation and necrosis of small or large regions within the prostate gland, while sparing thermally sensitive rectal tissue.

Combination of implantable and transurethral ultrasound applicators for prostate thermal therapy

This preliminary investigation demonstrates that using implantable ultrasound applicators (with energy directed away from the rectum and nontargeted tissue) in combination with a directional transurethral ultrasound applicator have potential to provide controlled thermal coagulation and necrosis of small or large regions within the prostate gland, while sparing thermally sensitive rectal tissue.

Interstitial ultrasound applicators for localized thermal coagulation of tissue

Two interstitial ultrasound applicator design configurations were evaluated for high-temperature thermal therapy using computer simulations, acoustic beam measurements, and in vivo temperature measurements. Simulated transient temperature rises and cumulative thermal dose distributions indicate that these applicators can produce target temperatures greater than 50/spl deg/C and corresponding thermal doses greater than 300-600 EM43/spl deg/C within 5 min at a radial depth of 1 cm in moderately perfused tissues. Temperature distributions achieved with prototype applicators in vivo were in good agreement with theoretical calculations, and further demonstrate that the devices are practicable, sufficient power output levels can be obtained, and heating profiles can be shaped to protect non-targeted critical normal tissues. This preliminary study demonstrates that these interstitial ultrasound applicators have potential to provide controlled thermal ablation (necrosis) of small cancerous lesions, and deserve further investigation for possible implementation in sites such as prostate and brain.

Prostate thermal therapy with interstitial and transurethral ultrasound applicators : A feasibility study

The purpose of this study was to determine the feasibility of using a transurethral ultrasound applicator in combination with implantable ultrasound applicators for inducing thermal coagulation and necrosis of localized cancer lesions or BPH within the prostate gland. The concept being evaluated is the potential to treat target zones in the anterior and lateral portions of the prostate with the transurethral applicator, while simultaneously treating regions of extracapsular extension and zones in the posterior prostate with the directive implantable applicators in combination with a rectal cooling bolus. Biothermal computer simulations, acoustic characterizations, and in vivo thermal dosimetry experiments were used to evaluate the performance of each applicator type and combinations thereof. The preliminary results of this investigation demonstrate that implantable ultrasound applicators, in combination with a transurethral ultrasound applicator, have the potential to provide thermal coagulation and necrosis of small or large regions within the prostate gland, while sparing thermally sensitive rectal tissue.

Ultrasound technology for thermal therapy: interstitial and intracavitary approaches

Reviews recent advances in interstitial and intracavitary ultrasound applicators designed for high-temperature thermal therapy and hyperthermia. Design and performance characteristics determined by acoustic measurements, in vitro and in vivo studies are presented. These results demonstrate the ability of this ultrasound technology to provide highly controllable zones of thermal coagulation or temperature elevation.

Transurethral high-intensity ultrasound for treatment of stress urinary incontinence (SUI): simulation studies with patient-specific models

Abstract Background: Stress urinary incontinence (SUI) is prevalent in adult women, attributed to weakened endopelvic supporting tissues, and typically treated using drugs and invasive surgical procedures. The objective of this in silico study is to explore transurethral high-intensity ultrasound for delivery of precise thermal therapy to the endopelvic tissues adjacent to the mid-urethra, to induce thermal remodeling as a potential minimally invasive treatment alternative. Methods: 3D acoustic (Rayleigh–Sommerfeld) and biothermal (Pennes bioheat) models of the ultrasound applicator and surrounding tissues were devised. Parametric studies over transducer configuration [frequency, radius-of-curvature (ROC)] and treatment settings (power, duration) were performed, and select cases on patient-specific models were used for further evaluation. Transient temperature and thermal dose distributions were calculated, and temperature and dose metrics reported. Results: Configurations using a 5-MHz curvilinear transducer (3.5u2009×u200910u2009mm, 28u2009mm ROC) with single 90u2009s sonication can create heated zones with 11u2009mm penetration (>50u2009°C) while sparing the inner 1.8u2009mm (<45u2009°C) radial depth of the urethral mucosa. Sequential and discrete applicator rotations can sweep out bilateral coagulation volumes (1.4u2009W power, 15° rotations, 600u2009s total time), produce large volumetric (1124u2009mm³ above 60 EM43u2009°C) and wide angular (∼50.5° per lateral sweep) coverage, with up to 15.6u2009mm thermal penetration and at least 1.6u2009mm radial urethral protection (<5u2009EM43u2009°C). Conclusion: Transurethral applicators with curvilinear ultrasound transducers can deliver spatially selective temperature elevations to lateral mid-urethral targets as a possible means to tighten the endopelvic fascia and adjacent tissues.