Prostate thermal therapy with high intensity transurethral ultrasound: the impact of pelvic bone heating on treatment delivery.

Purpose: This study was designed to assess pelvic bone temperature during typical treatment regimens of transurethral ultrasound thermal ablation of the prostate to establish guidelines for limiting bone heating.

Methods: Treatment with transurethral planar, curvilinear, and sectored tubular applicators was simulated using an acoustic and biothermal pelvic model that accommodates applicator sweeping, boundary temperature control, and changes in perfusion and attenuation with thermal dose to more accurately model ultrasound energy penetration. The effects of various parameters including power and frequency (5-10 MHz) on bone heating were assessed for a range of prostate cross-sections (3-5 cm) and bone distances (1-3 cm).

Referenceless MR thermometry for monitoring thermal ablation in the prostate.

Referenceless proton resonance frequency (PRF) shift thermometry provides a means to measure temperature changes during minimally invasive thermotherapy that is inherently robust to motion and tissue displacement. However, if the referenceless method is used to determine temperature changes during prostate ablation, phase gaps between water and fat in image regions used to determine the background phase can confound the phase estimation. We demonstrate an extension to referenceless thermometry which eliminates this problem by allowing background phase estimation in the presence of phase discontinuities between aqueous and fatty tissue.

Magnetic resonance-guided high-intensity ultrasound ablation of the prostate.

Objectives: This paper describes our work in developing techniques and devices for magnetic resonance (MR)-guided high-intensity ultrasound ablation of the prostate and includes review of relevant literature.

Methods: Catheter-based high-intensity ultrasound applicators, in interstitial and transurethral configurations, were developed to be used under MR guidance. Magnetic resonance thermometry and the relevant characteristics and artifacts were evaluated during in vivo thermal ablation of the prostate in 10 animals.

MRI-temperature mapping during ultrasound prostate ablation using fat for phase estimation.

Referenceless proton resonance frequency (PRF) shift thermometry provides a means to measure temperature changes during minimally invasive thermotherapy that is inherently robust to motion and tissue displacement. In this study, the method is expanded to allow background phase estimation from fatty tissue. A correction scheme for temperature map distortions caused by the ultrasound applicator is developed.

Curvilinear transurethral ultrasound applicator for selective prostate thermal therapy.

Thermal therapy offers a minimally invasive option for treating benign prostatic hyperplasia (BPH) and localized prostate cancer. In this study we investigated a transurethral ultrasound applicator design utilizing curvilinear, or slightly focused, transducers to heat prostatic tissue rapidly and controllably. The applicator was constructed with two independently powered transducer segments operating at 6.

Effects of spatial and temporal resolution for MR image-guided thermal ablation of prostate with transurethral ultrasound.

Purpose: To describe approaches for determining optimal spatial and temporal resolutions for the proton resonance frequency shift method of quantitative magnetic resonance temperature imaging (MRTI) guidance of transurethral ultrasonic prostate ablation.

Materials And Methods: Temperature distributions of two transurethral ultrasound applicators (90 degrees sectored tubular and planar arrays) for canine prostate ablation were measured via MRTI during in vivo sonication, and agree well with two-dimensional finite difference model simulations at various spatial resolutions. Measured temperature distributions establish the relevant signal-to-noise ratio (SNR) range for thermometry in an interventional MR scanner, and are reconstructed at different resolutions to compare resultant temperature measurements.

MRI-guided interstitial ultrasound thermal therapy of the prostate: a feasibility study in the canine model.

The feasibility of MRI-guided interstitial ultrasound thermal therapy of the prostate was evaluated in an in vivo canine prostate model. MRI compatible, multielement interstitial ultrasound applicators were developed using 1.5 mm diameter cylindrical piezoceramic transducers (7 to 8 MHz) sectored to provide 180 degrees of angular directional heating.

Highly directional transurethral ultrasound applicators with rotational control for MRI-guided prostatic thermal therapy.

Transurethral ultrasound applicators with highly directional energy deposition and rotational control were investigated for precise treatment of benign prostatic hyperplasia (BPH) and adenocarcinoma of the prostate (CaP). Two types of catheter-based applicators were fabricated, using either 90 degrees sectored tubular (3.5 mm OD x 10 mm) or planar transducers (3.