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Matthew Bruce

Principal Scientist/Engineer






B.S. Electrical and Computer Engineering, Michigan Technological University, 1991

M.S. Electrical and Computer Engineering, Virginia Polytechnic University, 1993

Ph.D. Bioengineering, University of Washington, 2004

Matthew Bruce's Website



2000-present and while at APL-UW

Quantitative tissue perfusion imaging using nonlinear ultrasound localization microscopy

Harmon, J.S., Z.Z. Khaing, J.E. Hyde, C.P. Hofstetter, C. Tremblay-Darveau, and M.F. Bruce, "Quantitative tissue perfusion imaging using nonlinear ultrasound localization microscopy," Sci. Rep., 12, doi:10.1038/s41598-022-24986-w, 2023.

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19 Dec 2022

Ultrasound localization microscopy (ULM) is a recent advancement in ultrasound imaging that uses microbubble contrast agents to yield vascular images that break the classical diffraction limit on spatial resolution. Current approaches cannot image blood flow at the tissue perfusion level since they rely solely on differences in velocity to separate tissue and microbubble signals; lower velocity microbubble echoes are removed during high pass wall filtering. To visualize blood flow in the entire vascular tree, we have developed nonlinear ULM, which combines nonlinear pulsing sequences with plane-wave imaging to segment microbubble signals independent of their velocity. Bubble localization and inter-frame tracking produces super-resolved images and, with parameters derived from the bubble tracks, a rich quantitative feature set that can describe the relative quality of microcirculatory flow. Using the rat spinal cord as a model system, we showed that nonlinear ULM better resolves some smaller branching vasculature compared to conventional ULM. Following contusion injury, both gold-standard histological techniques and nonlinear ULM depicted reduced in-plane vessel length between the penumbra and contralateral gray matter (–16.7% vs. –20.5%, respectively). Here, we demonstrate that nonlinear ULM uniquely enables investigation and potential quantification of tissue perfusion, arguably the most important component of blood flow.

Development of tough hydrogel phantoms to mimic fibrous tissue for focused ultrasound therapies

Kumar, Y.N., Z. Singh, Y.-N. Wang, G.R. Schade, W. Kreider, M. Bruce, E. Vlaisavljevich, T.D. Khokhlova, and A.D. Maxwell, "Development of tough hydrogel phantoms to mimic fibrous tissue for focused ultrasound therapies," Ultrasound Biol. Med., 48, 1762-1777, doi:10.1016/j.ultrasmedbio.2022.05.002, 2022.

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1 Sep 2022

Tissue-mimicking gels provide a cost-effective medium to optimize histotripsy treatment parameters with immediate feedback. Agarose and polyacrylamide gels are often used to evaluate treatment outcomes as they mimic the acoustic properties and stiffness of a variety of soft tissues, but they do not exhibit high toughness, a characteristic of fibrous connective tissue. To mimic pathologic fibrous tissue found in benign prostate hyperplasia (BPH) and other diseases that are potentially treatable with histotripsy, an optically transparent hydrogel with high toughness was developed that is a hybrid of polyacrylamide and alginate. The stiffness was established using shear wave elastography (SWE) and indentometry techniques and was found to be representative of human BPH ex vivo prostate tissue. Different phantom compositions and excised ex vivo BPH tissue samples were treated with a 700-kHz histotripsy transducer at different pulse repetition frequencies. Post-treatment, the hybrid gels and the tissue samples exhibited differential reduction in stiffness as measured by SWE. On B-mode ultrasound, partially treated areas were present as hyperechoic zones and fully liquified areas as hypoechoic zones. Phase contrast microscopy of the gel samples revealed liquefaction in regions consistent with the target lesion dimensions and correlated to findings identified in tissue samples via histology. The dose required to achieve liquefaction in the hybrid gel was similar to what has been observed in ex vivo tissue and greater than that of agarose of comparable or higher Young's modulus by a factor >10. These results indicate that the developed hydrogels closely mimic elasticities found in BPH prostate ex vivo tissue and have a similar response to histotripsy treatment, thus making them a useful cost-effective alternative for developing and evaluating different treatment protocols.

Blood flow changes associated with spinal cord injury assessed by non-linear Doppler contrast-enhanced ultrasound

Bruce, M., D. Dewees, J. Harmon, L. Cates, Z.Z. Khaing, and C.P. Hofstetter, "Blood flow changes associated with spinal cord injury assessed by non-linear Doppler contrast-enhanced ultrasound," Ultrasound Med. Biol., 48, 1410-1419, doi:10.1016/j.ultrasmedbio.2022.03.004, 2022.

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1 Aug 2022

Contrast-enhanced ultrasound (CEUS) is clinically used to image the microcirculation at lower imaging frequencies (<2 MHz). Recently, plane-wave acquisitions and Doppler processing have revealed improved microbubble sensitivity, enabling CEUS use at higher frequencies (15 MHz) and the ability to image simultaneously blood flow in the micro- and macrocirculations. We used this approach to assess acute and chronic blood flow changes within contused spinal cord in a rodent spinal cord injury model. Immediately after spinal cord injury, we found significant differences in perfusion deficit between moderate and severe injuries (1.73 ± 0.1 mm2 vs. 3.2 ± 0.3 mm2, respectively), as well as a delay in microbubble arrival time in tissue adjacent to the injury site (0.97 ± 0.1 s vs. 1.54 ± 0.1 s, respectively). Acutely, morphological changes to central sulcal arteries were observed where vessels rostral to the contusion were displaced 4.8 ± 2.2° and 8.2 ± 3.1° anteriorly, and vessels caudal to the contusion 17.8 ± 3.9° and 24.2 ± 4.1° posteriorly, respectively, for moderate and severe injuries. Significant correlation of the acute perfusion deficit and arrival time were found with the chronic assessment of locomotive function and histological estimate of spared spinal cord tissue.

More Publications

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