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Mohamed Ghanem

Postdoctoral Scholar

Email

mghanem@apl.uw.edu

Phone

206-616-7317

Education

B.S. Civil Engineering, University of Washington - Seattle, 2009

M.S. Aerospace & Aeronautical Engineering, University of Washington - Seattle, 2012

Ph.D. Aerospace & Aeronautical Engineering, University of Washington - Seattle, 2018

Publications

2000-present and while at APL-UW

A prototype therapy system for boiling histotripsy in abdominal targets based on a 256-element spiral array

Bawiec, C.R., T.D. Khokhlova, O.A Sapozhnikov, P.B. Rosnitskiy, B.W. Cunitz, M.A. Ghanem, C. Hunter, W. Kreider, G.R. Schade, P.V. Yuldashev, and V.A. Khokhlova, "A prototype therapy system for boiling histotripsy in abdominal targets based on a 256-element spiral array," IEEE Trans. Ultrason. Ferroelectr. Freq. Control, 68, 1496-1510, doi:10.1109/TUFFC.2020.3036580, 2021.

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1 May 2021

Boiling histotripsy (BH) uses millisecond-long ultrasound (US) pulses with high-amplitude shocks to mechanically fractionate tissue with potential for real-time lesion monitoring by US imaging. For BH treatments of abdominal organs, a high-power multielement phased array system capable of electronic focus steering and aberration correction for body wall inhomogeneities is needed. In this work, a preclinical BH system was built comprising a custom 256-element 1.5-MHz phased array (Imasonic, Besançon, France) with a central opening for mounting an imaging probe. The array was electronically matched to a Verasonics research US system with a 1.2-kW external power source. Driving electronics and software of the system were modified to provide a pulse average acoustic power of 2.2 kW sustained for 10 ms with a 1–2-Hz repetition rate for delivering BH exposures. System performance was characterized by hydrophone measurements in water combined with nonlinear wave simulations based on the Westervelt equation. Fully developed shocks of 100-MPa amplitude are formed at the focus at 275-W acoustic power. Electronic steering capabilities of the array were evaluated for shock-producing conditions to determine power compensation strategies that equalize BH exposures at multiple focal locations across the planned treatment volume. The system was used to produce continuous volumetric BH lesions in ex vivo bovine liver with 1-mm focus spacing, 10-ms pulselength, five pulses/focus, and 1% duty cycle.

Noninvasive acoustic manipulation of objects in a living body

Ghanem, M.A., A.D. Maxwell, Y.-N. Wang, B.W. Cunitz, V.A. Khokhlova, O.A. Sopozhnikov, and M.R. Bailey, "Noninvasive acoustic manipulation of objects in a living body," Proc. Nat. Acad. Sci. USA, 117, 16,848-16,855, doi:10.1073/pnas.2001779117, 2020.

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21 Jul 2020

In certain medical applications, transmitting an ultrasound beam through the skin to manipulate a solid object within the human body would be beneficial. Such applications include, for example, controlling an ingestible camera or expelling a kidney stone. In this paper, ultrasound beams of specific shapes were designed by numerical modeling and produced using a phased array. These beams were shown to levitate and electronically steer solid objects (3-mm-diameter glass spheres), along preprogrammed paths, in a water bath, and in the urinary bladders of live pigs. Deviation from the intended path was on average <10%. No injury was found on the bladder wall or intervening tissue.

Design, fabrication, and characterization of broad beam transducers for fragmenting large renal calculi with burst wave lithotripsy

Randad, A., M.A. Ghanem, M.R. Bailey, A.D. Maxwell, "Design, fabrication, and characterization of broad beam transducers for fragmenting large renal calculi with burst wave lithotripsy, " J. Acoust. Soc. Am., 148, 44-50, doi:10.1121/10.0001512, 2020.

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1 Jul 2020

Burst wave lithotripsy (BWL) is a technology for comminuting urinary stones. A BWL transducer's requirements of high-pressure output, limited acoustic window, specific focal depth, and frequency to produce fragments of passable size constrain focal beamwidth. However, BWL is most effective with a beam wider than the stone. To produce a broad-beam, an iterative angular spectrum approach was used to calculate a phase screen that was realized with a rapid prototyped lens. The technique did not accurately replicate a target beam profile when an axisymmetric profile was chosen. Adding asymmetric weighting functions to the target profile achieved appropriate beamwidth. Lenses were designed to create a spherically focused narrow-beam (6 mm) and a broad-beam (11 mm) with a 350-kHz transducer and 84-mm focal depth. Both lenses were used to fragment artificial stones (11 mm long) in a water bath, and fragmentation rates were compared. The linearly simulated and measured broad beamwidths that were 12 mm and 11 mm, respectively, with a 2-mm-wide null at center. The broad-beam and the narrow-beam lenses fragmented 44 ± 9% and 16 ± 4% (p = 0.007, N = 3) of a stone by weight, respectively, in the same duration at the same peak negative pressure. The method broadened the focus and improved the BWL rate of fragmentation of large stones.

More Publications

Inventions

Holographic Beam Shaping for Ultrasound Therapy Transducers

Record of Invention Number: 48221

Adam Maxwell, Mike Bailey, Mohamed Ghanem

Disclosure

1 Dec 2017

Acoustics Air-Sea Interaction & Remote Sensing Center for Environmental & Information Systems Center for Industrial & Medical Ultrasound Electronic & Photonic Systems Ocean Engineering Ocean Physics Polar Science Center
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