Patient‐Specific 3‐Dimensional Model for High‐Intensity Focused Ultrasound Treatment Through the Rib Cage

Abstract

Objectives-The purpose of this study was to develop a patient-specific 3-dimensional model for high-intensity focused ultrasound (HIFU) treatment through the rib cage using patient data.Methods-Experimental testing to derive parameters used in defining the amount of energy and alteration needed in treatment protocols for upper abdominal disorders under the rib cage was performed. Reconstructed rib cage models based on patient data, tissue-mimicking material phantoms, and magnetic resonance imaging-guided HIFU using a multielement phased array transducer were used in the experiments. Changes in the focal temperature, acoustic power, and acoustic pressure distribution were investigated with and without the presence of the rib cage model. An ExAblate system (InSightec Ltd, Tirat Carmel, Israel) was used to sonicate phantoms by varying the target phantom or rib cage model location.Results-The effect of the rib cage on the acoustic pressure distribution and acoustic power was closely related to the anatomic structures of the ribs. Thermometry revealed that heating at the focus could be controlled by changing either the power or duration of HIFU application to improve the focal temperature change. The focal temperature change was found to be related to the distance between the rib cage model and focus and the shadow area on the transducer elements covered by the rib cage model in the beam path.Conclusions-Experimental results suggest that the rib cage model is a valuable and useful tool that can provide realistic human anatomic structures and properties for evaluating the effects of the rib cage on ultrasound propagation.

Tissue mimicking materials for imaging and therapy phantoms: a review

“…* Properties reported as function of temperature, * * MJ/mm 3 K. the proton resonance frequency, the diffusion coefficient, T1 and T2 relaxation times, magnetization transfer and the proton density. Examples of TMMs for MR-thermometry are based on evaporated milk and ballistic gel(Farrer et al 2015), agar-silica soft tissue mimic(Menikou et al 2016) and PVA-based soft-tissue mimic(Cao et al 2019). These TMMs show similar acoustic properties, along with MR (T1 and T2 * ), mechanical and thermal properties and are widely used for QA of MRgFUS(Menikou et al 2015) as discussed in section 5.3.…”

In silico feasibility assessment of extracorporeal delivery of low-intensity pulsed ultrasound to intervertebral discs within the lumbar spine

“…Although this study demonstrates promising capabilities of a generic planar phased array for LIPUS delivery to IVDs, particularly to proximal-lateral regions of the annulus fibrosus, performance to central and anterior regions could likely be enhanced by adopting more specialized array designs. The array design employed in this study is similar to the Exablate 2100 Conformal Bone System array, which has a comparable geometry and footprint and consists of ~1000 channels operating at 550 kHz (Holbrook et al 2014, Cao et al 2020. In practice, the phased array applicator configuration could be combined with robotic stereotactic manipulation platforms (Yiallouras and Damianou 2015), registered with imaging (CT/MRI) for planning/guidance, to practically achieve the array placements and orientations explored herein.…”

Anatomic thermochromic tissue-mimicking phantom of the lumbar spine for pre-clinical evaluation of MR-guided focused ultrasound (MRgFUS) ablation of the facet joint

“…Menikou et al [15] demonstrated that breast/rib phantom can be utilized as a very useful tool for evaluating ultrasonic protocols. Cao et al [16] showed the rib cage model is a valuable and useful tool that can provide realistic human anatomic structures and properties for evaluating the effects of the rib cage on ultrasound propagation. Beaulieu et al [17] demonstrated the use of 3D printed anatomical models to replicate bone ultrasonographic properties in water.…”