Design and evaluation of a 63 element 1.75-dimensional ultrasound phased array for treating benign prostatic hyperplasia

Abstract

Focused ultrasound surgery (FUS) is a clinical method for treating benign prostatic hyperplasia (BPH) in which tissue is noninvasively necrosed by elevating the temperature at the focal point above 60<th>°C using short sonications. With 1.75-dimensional (1.75-D) arrays, the power and phase to the individual elements can be controlled electronically for focusing and steering. This research describes the design, construction and evaluation of a 1.75-D ultrasound phased array to be used in the treatment of benign prostatic hyperplasia. The array was designed with a steering angle of ±13.5 deg in the transverse direction, and can move the focus in three parallel planes in the longitudinal direction with a relatively large focus size. A piezoelectric ceramic (PZT-8) was used as the material of the transducer and two matching layers were built for maximum acoustic power transmission to tissue. To verify the capability of the transducer for focusing and steering, exposimetry was performed and the results correlated well with the calculated fields. In vivo experiments were performed to verify the capability of the transducer to ablate tissue using short sonications. [Work supported by the Whitaker Foundation and the Department of Defense Congressionally Directed Medical Prostate Cancer Research Program.]

Optimization of ultrasound array designs for high intensity focused treatment of prostate cancer and benign prostatic hyperplasia

“…This choice of element dimensions means that Grating lobes will be generated at unwanted locations. It has been found that a value of Grating lobe that is 20% of the maximum intensity is acceptable as it will not lead to temperatures above 41°C at the location of the Grating lobes, unless excessive acoustical power is used [8][9][10].…”

“…Previous effective flat arrays that were able to generate lesions in parts of the prostate include a two-dimensional (2-D) 8 9 8 phased array that was capable of electrically focusing and steering the ultrasound beam over a portion (less than half) of the prostate [8]. Another example is a 1.75-dimensional (1.75-D) 21 9 3 phased array that had the capability of focusing and steering the ultrasound beam at three different parallel planes inside the prostate [9,10]. Other flat shapes that were introduced in the past were 1.5-dimensional (1.5-D) 64 9 4 and 42 9 3 phased arrays that were used to perform tissue ablation on cancerous cells in the prostate [2].…”

Feasibility of in vivo Transesophageal Cardiac Ablation Using a Phased Ultrasound Array

“…In comparison to a full matrix array (195 elements), a sparse array (64 active elements) has a benefit from the reduced number of elements. Additionally, an array with tapered elements was designed to significantly suppress grating lobes (Benkeser et al 1987;Saleh and Smith 2005). According to the simulation results, the sparse array model with tapered elements produced no significant grating lobes.…”

Clinical applications of high-intensity focused ultrasound

“…Both USG-guided probes and MRI-guided systems have been developed. The USG probes are inserted per rectum and incorporate both imaging and therapeutic transducers in one unit, [35][36][37][38][39][40][41] such as Ablatherm (Edap Technomed, France) and the Sonablate (Focus Surgery Inc, US), whereas a prostate-dedicated MRI-HIFU system makes use of either the transrectal (ExAblate OR; InSightec) or transurethral (Philips Healthcare) approach.…”