Automated HIFU treatment planning and execution based on 3D modeling of the prostate, urethra, and rectal wall

Abstract

Current treatment planning with the Sonablate500 image-guided high-intensity focused ultrasound (HIFU) device (Focus Surgery, Inc.) used for the treatment of prostate cancer consists of defining treatment zones on up to 15 ultrasound images that span the entire prostate. While effective, this process may be time-consuming in the case of large prostates or if multiple treatments are required. For this reason, a method has been developed to quickly model the prostate, urethra, and rectal wall from 2D ultrasound images to allow for completely automated treatment planning for HIFU treatments. It is based on the identification of boundaries and prostate structures in 4 to 6 orthographic ultrasound images prior to treatment. The structures are defined through traces and form the input to structure-specific 3D models. All structures are modeled as deformable parametric surfaces that are then processed by the automated treatment planning module. Early results show that the developed models are robust, flexible, generate good closed surfaces even in the absence of full imaging data, and accurately model the wide variation encountered in tracing and pointing skills, human prostates, urethras, and rectal wall shapes. Such model accuracy has shown to be sufficient for planning these HIFU treatments. The entire treatment planning process is shown, highlighting the usefulness of the developed 3D models. Specific model details for the prostate, urethra, and the rectal are given. Results using in-vivo animal and human data as model inputs and envisioned treatment planner outputs are also presented, together with the initial integration activities into the Sonablate500 HIFU device.

An integrated system for therapy planning of high intensity focused ultrasound

“…In comparable studies, the most commonly used tools are magnetic resonance image (MRI) [8] and ultrasonic imaging [4]. and each one has its own advantages over the other.…”

“…To capture 3D volume using ultrasonic imaging, one common method is to combine several equally-spaced parallel frames [4], which requires additional motion control of the imaging probe. In our setup, instead of constructing a volume from parallel frames, we used a 3D probe from Prosonic (3.3Mhz central frequency, 128 element phased array) with a built-in motor for steering the imaging array to captures sector frames at an angle up to 45 degree from the center plane.…”

“…In clinical practice, the target area for the HIFU exposure is usually larger than the size of HIFU focus and therefore multiple exposures are generally needed for a single target area [4]. After the volume of interest was captured, the target area should be segmented out from surround tissues for HIFU planning.…”

“…To achieve better clinical results, there also have been active research activities on HIFU planning, most of which are organ specific. For example, in [4], Seip et al focused on generating a three dimensional representation of the organ and the target from ultrasonic imaging, then a set of targeted HIFU lesions were selected automatically from a known "lesion library" to fill the entire target area. While such techniques can be sufficient for organs like the prostate, it cannot be easily extended to other organs like the brain due to unique characteristics of each organ [5].…”

HIFU Therapy Planning Using Pre-treatment Imaging and Simulation

“…Typically, the therapy planning approach involves: use of pre-treatment imaging data; segmentation -manual or semi-automated; development of 3D anatomy model or registration with a reference dataset; simulation of HIFU beam and thermal dosimetry around the target tissue; and display and review of the treatment plan. Recent developments in therapy planning using imaging are targeted for specific applications, e.g., for prostate cancer using 3D ultrasound images [1].…”