Transurethral ultrasound array for prostate thermal therapy: initial studies

MRI‐guided thermal therapy of transplanted tumors in the canine prostate using a directional transurethral ultrasound applicator

“…The tubular transducer segments on these applicators were sectored from the outer electrode surface to radiate an angularly directive beam pattern, producing an arc of energy output over a 180°active acoustic zone along the transducer length. Details of applicator design and performance are given by Diederich and Burdette (19) and Diederich et al (20). The angularly directive beam distributions can be used to increase heating selectivity to specific lobes or regions of the prostate gland while protecting nontargeted regions.…”

“…The angularly directive beam distributions can be used to increase heating selectivity to specific lobes or regions of the prostate gland while protecting nontargeted regions. Note that these applicators were initially designated for the treatment of BPH, with 180°directivity selected to target the anterolateral zones of the prostate while avoiding the rectum (19,20). In addition, these applicator configurations allow the heating pattern to be adjusted in real time along the length of the prostatic urethra by varying the applied power levels to each independently controlled transducer segment.…”

“…Transurethral ultrasound applicators which are currently under development were used to apply heating energy directly to selected regions of the prostate that contained implanted tumors (20,19). Two slightly different applicator configurations were used in this study.…”

“…Towards this end, the feasibility of prostate thermal ablation using transurethral ultrasound applicators has recently been reported, demon-strating potential for highly controllable heating patterns in both the angle and along the applicator length (19,20). In order to take full advantage of the enhanced spatial control afforded by these applicators, it may be possible to control and monitor treatments with these devices using MRI, and more specifically real-time multi-planar MRTI.…”

Interstitial devices for minimally invasive thermal ablation by high-intensity ultrasound

“…These applicators are usually small (1.5 to 2.5 mm in diameter) to facilitate insertion into a catheter 56 or placement in direct contact with tissue 23 . At present, this technique is proposed for treatment of benign prostate hypertrophy (BPH) 20 and prostate cancer [56][57][58] ; to correct some forms of cardiac arrhythmia 27 and for spinal treatments 59 . In general, the acoustic power of these applicators consists in several acoustic watts and treatment time lasts 15 to 20 minutes to reach temperatures of about 55°C in exposed tissue.…”