Medical ultrasound has diagnostic and therapeutic applications. Diagnostic ultrasound is used to make images of the inside of the body. The most well-known application is imaging fetuses, but ultrasound can be used to image many soft tissues including the heart, liver, and kidney. Therapeutic ultrasound may be used to destroy tissues such as tumors and uterine fibroids. The FDA is responsible for ensuring safety and effectiveness of medical ultrasound. The research areas that the Ultrasonics group focusses upon are summarized below:
Earthworm Vessel Before (a) and After (b) Rupture from high intensity ultrasound
Tissue-Mimicking material made from high temperature hydrogel
Modeling of dissipation of heat in biological tissue, from ultrasound exposure
Measurement of Therapeutic and Diagnostic Ultrasound Fields
The focus of this area is to identify or develop appropriate methods for pre-clinical device evaluation and characterization of therapeutic ultrasound devices. High intensity therapeutic ultrasound (HITU) holds the potential for radically advanced therapeutic techniques, including ablation of both malignant and benign lesions and cessation of internal bleeding in injured vessels and organs. Although some clinical success has been achieved, the lack of standardized methods to assess the acoustic and thermal characteristics of the beam is one factor that has hampered general understanding and acceptance, and has slowed FDA regulatory review of HITU systems.
Modeling and Simulation of Ultrasound Fields and Bioeffects
In this area, mathematical models for ultrasound propagation are developed, compared, and analyzed. Since ultrasound physics is complex, numerical methods are developed to obtain fast and accurate solutions of the model equations. These solutions provide a basis for comparison of different models to determine which is most relevant given a certain application. They also facilitate understanding of the many physical processes related to ultrasound, including beam diffraction, nonlinear effects, and absorption of energy by tissue media, heat conduction, and thermal lesion formation.
Safety Evaluation of Medical Ultrasound Devices
This research aims to develop measurement techniques for analyzing the thermal safety of ultrasound imaging as well as ablation devices such as HITU, as part of thermal safety evaluation of these devices. Current areas include (a) measuring the ultrasound thermal field by IR thermography; (b) developing both a tissue mimicking and blood mimicking material as HITU phantoms for comparing temperature measurements with those in ex vivo tissue; and (c) characterizing the transient temperature rise during diagnostic ultrasound eye exam and acoustic radiation force (ARFI) elastography imaging.
Bioeffects of Ultrasound on the Nervous System
In this area, we investigate the bioeffects of pressure waves on both the central nervous system and the peripheral nervous system. Ongoing investigations include: mechanisms of traumatic brain injury (TBI) using a high-intensity focused ultrasound (HIFU) based model of blast waves, thresholds for microvasculature rupture in the brain, and acoustic neuromodulation. Results will help evaluate biomarkers for diagnosing TBI, quantify safety thresholds for transcranial ultrasound procedures such as tumor ablation and clot lysis, and establish operating regimes where neuromodulation is effective in treating various autoimmune disorders and mental illnesses.
Effectiveness Evaluation of Medical Ultrasound Devices
In this area, we explore methods for rigorously characterizing ultrasound device diagnostic performance. In collaboration with the Quantitative Imaging Biomarkers Alliance (QIBA), we are developing standardized phantoms and measurements for assessing ultrasound shear wave velocity in liver, used for staging liver fibrosis. In collaboration with the American Institute of Ultrasound in Medicine (AIUM) Technical Standards Committee, we are exploring potential risks and benefits associated with conditional increased output of ultrasound transducers, important for overweight patients. We are developing tissue-mimicking phantoms for use in photoacoustics for assessing blood oxygenation, and methods for predicting osteoporotic fracture risk.
The creation of realistic ultrasound models, phantoms, and the understating of bioeffects all depend on accurate knowledge of the relevant tissue’s mechanical and thermal properties. Important characteristics include density, sound speed, ultrasound absorption, heat capacity, perfusion rate, and more. The characterization process provides information on how an “average” tissue of a given type might behave when exposed to ultrasound and also provides a better understanding of how much variation occurs across populations of people. This area seeks to expand the knowledgebase of tissue properties by designing new measurement methods and performing careful measurements on tissue samples, with the overall goal of achieving improved accuracy of the tools used for ultrasound testing, regulation, and product development.
Current funding sources
American Institute of Ultrasound in Medicine (AIUM)
Defense Advanced Research Projects Agency (DARPA)
FDA Medical Countermeasures Initiative (MCMi)
FDA Office of Women’s Health (OWH)
National Institute for Biomedical Imaging and Bioengineering (NIBIB)
National Institutes of Health (NIH)
National Science Foundation
Quantitative Imaging Biomarkers Alliance (QIBA)
U.S. Army Medical Research and Materiel Command
Keith Wear, Ph.D.
Gregory Clement, Ph.D.
Yunbo Liu, Ph.D.
Subha Maruvada, Ph.D.
Matthew Myers, Ph.D.
Joshua Soneson, Ph.D.
Maureen Dreher, Ph.D.
Dr. Brian Garra
Stanley Huang, Ph.D.
Srinidhi Nagaraja, Ph.D.
Joshua Pfefer, Ph.D.
William Vogt, Ph.D.
Meijun Ye, Ph.D.
Gammell Applied Technologies
George Washington University
Purdue University School of Medicine
University College, London
University of California at Berkeley
University of Cincinnati
University of Michigan
University of Mississippi
University of Tokyo
University of Wisconsin
Uniformed Services University of the Health Sciences
- ONDA acoustic scanning system
- High intensity therapeutic ultrasound transducers
- Ultrasound hydrophones
- Acertara acoustic scanning system
- Thin wire thermocouples and thermal property analyzer
- Time delay spectrometry system
- Radiation Force Balance system
- HP Impedance Analyzer
- ONDA schlieren imaging system
- Hydrophone field mapping system
- Decagon KD-2
- Oscilloscopes, function generators
- VeraSonics 256 Ultrasound Imaging System
Public domain software
Relevant standards & guidances
- FDA: Ultrasonic Therapy and Surgery Products Performance Standard, Federal Register 1050.10 (1978 – rev. 2012)
- U.S. Guidance for Industry and FDA Staff, Class II Special Controls Guidance Document: Focused Ultrasound Stimulator System for Aesthetic Use, 2011
- IEC 62SC: Medical electrical equipment – Part 2-5: Particular requirements for the safety of ultrasonic physiotherapy equipment – IEC 60601-2-5 (Ed. 3.0) 2009
- U.S. Guidance for Industry and FDA Staff, Information for Manufacturers Seeking Marketing Clearance of Diagnostic Ultrasound Systems and Transducers, 2008
- IEC 62555 - Ultrasonics - Power measuement - Output power measurement for High Intensity Therapeutic Ultrasound (HITU) transducers and systems
- IEC 62556 - Surgical Systems - Specification and measurement of field parameters for High Intensity Therapeutic Ultrasound (HITU) transducers and systems
- IEC 61828 - Ultrasonics: Focusing transducers, Definitions and measurement methods for the transmitted fields
- IEC 60601-2-62 - Particular requirements for the basic safety and essential performance of high intensity therapeutic ultrasound HITU equipment
- IEC 61161 - Ultrasonics - Power measurement - Radiation force balances and performance requirements, ed. 2
- IEC 61689 - Ultrasonics - Physiotherapy systems - Performance requirements and methods of measurement in the frequency range 0,5 MHz to 5 MHz
- IEC NWP - Ultrasonics – Therapeutic systems – Field specifications and methods of measurement in the frequency range of 20 kHz to 500 kHz
- IEC 62462 - Ultrasonics - Output test - Guide for the maintenance of ultrasound physiotherapy systems
- IEC 62127-1 - Ultrasonics - Hydrophones - Part 1: Measurement and characterisation of medical ultrasonic fields up to 40 MHz
- IEC 62127-2 - Ultrasonics - Hydrophones - Part 2: Calibration for ultrasonic fields up to 40 MHz
- IEC 60601-2-37 - Particular requirements for the basic safety and essential performance of ultrasonic medical diagnostic and monitoring equipment
- IEC 61684 - Ultrasonics - Pressure pulse lithotripters - Characteristics of fields
- IEC 60601-2-36 - Particular requirements for the basic safety and essential performance of equipment for extracorporeally induced lithotripsy
- IEC 62359 - Ultrasonics - Field Characterization - Test methods for the determination of thermal and mechanical indices related to medical diagnostic ultrasonic fields
Selected Peer-Review Publications
- Q. Wang et al, Investigation of the correlation between diffuse infrared and ultrasound for transcranial ultrasound, Biomedical Physics & Engineering Express, 2016.
- Liu et al., Thermal Safety Simulations of Transient Temperature Rise during Acoustic Radiation Force-Based Ultrasound Elastography
- McCabe et al., Application of high-intensity focused ultrasound to the study of mild traumatic brain injury
- Wear et al., Improved Measurement of Acoustic Output Using Complex Deconvolution of Hydrophone Sensitivity
- Soneson, A parametric study of error in the parabolic approximation of focused axisymmetric ultrasound beams
- King et al., Development and characterization of a tissue-mimicking material for high-intensity focused ultrasound,
- Maruvada et al., A procedure for acoustic power calibration of high intensity focused ultrasound transducers using a radiation force technique
- Harris, Progress in medical ultrasound exposimetry