Biomedical Acoustics

Ultrasound-induced heating and lesion formation enhanced with phase-shift nanoemulsions

High-intensity focused ultrasound (HIFU) can treat solid tumors by depositing enough heat to denature proteins, resulting in thermal coagulation.  The heating process can be enhanced in the presence of acoustic cavitation.  We have developed a phase-shift nanoemulsion (PSNE) that can be used to provide acoustic cavitation on demand with fine spatial and temporal control.  The PSNE are small enough to extravasate from tumor vasculature and accumulate in the tumor interstitial space. Potentially, this will lead to predictable lesion formation via bubble-enhanced heating, and significantly reduce the treatment time required for HIFU-induced tumor ablation.  

  • Faculty: Porter                                                                                                      
  • Student: P. Zhang (PhD)

Ultrasound based biomechanical imaging

picture-823In this work we aim to measure mechanical property distributions in tissues, principally the shear modulus. Doing so requires the measurement of tissue displacement which we do by means of diagnostic ultrasound. The measured deformation is used as an input to an inverse problem which we solve in order to determine the distribution of mechanical properties in the tissue.  The applications include detection and differential diagnosis of cancer tumors in the breast.

  •  Faculty: Barbone (BU), and A. Oberai (RPI)
  • Students: C. Rivas (PhD)                                                                        

The Physics of Non-Invasive Therapy Using High Intensity Focused Ultrasound (HIFU)

ultrasound-biomech-image1Transcutaneous and intraoperative surgery by high-intensity focused ultrasound (HIFU) is an exciting new modality for minimally invasive medical therapy.  This project focuses on understanding and exploiting the role that bubbles and cavitation play in both mitigating and promoting tissue heating and disruption by HIFU.  We have shown that HIFU-induced cavitation activity can significantly enhance tissue heating rates and provides a means for imaging the subsequent thermal lesion.  On the other hand, too much cavitation can shield the target region and/or lead to heating rates so excessive that boiling results.  The key is to generate cavitation activity at the lowest possible acoustic pressure amplitude and control the spatial and temporal characteristics of the resulting cavitation field to avoid boiling, bubble shielding and malformed lesions.  The effort is funded primarily by the DoD and supplemented by industry funds and NSF support via the Center for Subsurface Sensing and Imaging Systems.

  • Faculty: Cleveland, Holt, and Roy
  • Recent Students: C. Farny (PhD, 2007) and A. Draudt (PhD)

Nucleating Inertial Acoustic Cavitation in Tissue Using Laser-Heated Gold Nano-Particles

ultrasound-biomech-image11Transcutaneous and intraoperative surgery by high-intensity focused ultrasound (HIFU) is an exciting new modality for minimally invasive medical therapy.  By safely promoting cavitation activity, one can enhance HIFU heating rates, improve targeting, and minimize treatment times.  This project studies a technique for nucleating cavitation activity “on demand” in translucent tissues, such as breast and brain.  When gold nano-particles are exposed pulsed laser excitation, a microscopic vapor cavity is formed from the rapid particle heating.  This cavity, when created during the rarefaction phase of HIFU exposure, serves to nucleate inertial acoustic cavitation activity that can be sustained for the duration of the acoustic exposure.  Because the particles are durable, they can be reused to nucleate cavitation on demand as needed.  This project is currently unfunded, but we expect to secure NSF support via the Center for Subsurface Sensing and Imaging Systems and a Boston University Dean’s Catalyst Award.

  • Faculty: Holt, and Roy
  • Students: C. Farny (PhD, 2007), T Wu (PhD, 2007), H. Ju (PhD) and J. McLaughlan (postdoc)

The Center for Subsurface Sensing and Imaging Systems (CenSSIS): Acoustics Thrust & MedBED

censsis-iamgeCenSSIS is an NSF-funded Engineering Research Center based at Northeastern University, with academic partners at Boston University, RPI, and the University of Puerto Rico at Mayaguez.  The Center is subdivided into a series of research thrusts.  The Acoustics thrust is based in Roy’s lab and includes a number of projects related to the use of acoustics in sensing and imaging.  A medical sensing and imaging testbed (MedBED) has been developed and currently active projects (and key investigators) include quantitative ultrasound imaging (Cleveland), the scanning acoustic microscope (Cleveland), acousto-optic imaging (Roy/Murray), HIFU cavitation diagnostics (Roy/Holt/Cleveland), and elasticity imaging (Barbone).  The Center is funded primarily by NSF, with supplemental support from industry (Analogic Corp., among others).

  • Faculty: Barbone, Cleveland, and Roy
  • Recent Students: A. Draudt (PhD), P. Lai (PhD), C. Rivas (PhD) and W. Duncanson (PhD; BME)

Lithotripsy

lithotripsy-imageShock Wave Lithotripsy (SWL) is a non-invasive medical technique for treating kidney stones.  Shock waves generated outside the body are focused onto the kidney stones resulting in fragmentation into pieces small enough to be passed naturally.   The goal of the research is to understand the process by which the shock waves fragment the stones and to understand the mechanisms by which shock waves can damage the surrounding soft tissue.  This work is carried out in collaboration with colleagues at Indiana University Medical School, University of Washington at Seattle, Caltech, University of Illinois and the BU Medical School.   This work is primarily funded by the National Institutes of Health and has also been supported by the Whitaker Foundation.

  • Faculty: Cleveland
  • Recent Students: P Chitnis (PhD 2006), H. Luo (PhD), J. Kracht (PhD)

Quantitative Ultrasound Imaging

quant-ultrasound-imageThe goal of this project is to employ tomographic inversion of ultrasound data to detect HIFU lesions.  In general tomographic reconstruction of ultrasound data in the body is not practical because the limited acoustic windows into the body normally mean only limited-view backscatter data is available.  The resulting inversion problem is therefore poorly posed.  In the case of HIFU however the individual lesions are approximately ellipsoidal in shape and the approximate position and size is known a priori.  Second, the process of necrosis results in change in sound speed and attenuation inside the lesion from their nominal values. Therefore the lesion can be described using shape-based methods where it is necessary to estimate only a small number of parameters to describe the geometry of the lesion rather than determine all the acoustics properties over all space.  This makes the inversion problem tractable even with the limited view backscatter data of an ultrasound probe.

  • Faculty: Cleveland, and E. Miller (ECE-Tufts)
  • Students: B. Ulker-Karbeyaz (PhD 2005, NU), A. Draudt (PhD), E. Guven (PhD, NU)

Targeted Ultrasound Contrast Agents for Drug Delivery

targetet-ultrasound-imageThis is project is a collaboration with Prof. Joyce Wong of the Department of Biomedical Engineering (BME) at BU.  Prof. Wong is developing molecules that target and bind to diseased tissue.   One barrier to her work is finding appropriate contrast agents that these molecules can be attached to so that the diseased tissue can be imaged.  One candidate is the ultrasound contrast agent, which typically consists of a gas microbubble, 1 to 5 µm in diameter, encapsulated with a thin shell.  We are investigating the use of polymer-shelled contrast agents.  The ultrasound imaging systems and scanning acoustic microscope are used to characterize the properties of the microbubbles developed in the Wong Lab.  This work is funded by the National Institutes of Health and the NSF Centre for Subsurface Sensing and Imaging Systems.

  • Faculty: Cleveland, and Wong (BME-BU)
  • Students: W. Duncanson (PhD 2008, BME)