School of Biomedical Engineering, Science & Health Systems V 1.0 SD [020307] BIOMEDICAL ULTRASOUND RESEARCH Acoustic-optic Measurements Characterization of Piezoelectric Imaging Transducers and Materials: The swept frequency approach (Time Delay Spectrometry – TDS) allows transducer characterization and material attenuation measurements to be performed as nearly continuous functions of frequency. The measurements are carried out routinely from 250 kHz up to 40 MHz. Recently the range has been extended to 60 MHz. Current research is focused on extending bandwidth to 100 MHz and independent verification of the data using optical measurements. Typical applications: ultrasound metrology, assessment of safety of ultrasound imaging systems, specialty transducer design, and non-destructive testing. PROGRAM OVERVIEWPROGRAM OVERVIEW Design and Calibration of Miniature Piezoelectric Polymer Ultrasonic Hydrophone Probes: Such probes are indispensable for acoustic field characterizations. Available hydrophones are usually calibrated at discrete frequencies only. Such calibration is inadequate, as it fails to detect possible rapid variations in the sensitivity of the probes. We have developed unique probe calibration methods, which plot sensitivity as a virtually continuous function of frequency up to 60 MHz; they are now being extended to 100 MHz. Evaluation of Spatial Averaging Corrections: Ideal characterization of acoustic fields would require an actual point probe or receiver. Since all available probes have finite aperture, a faithful reproduction of the acoustic pressure-time waveform involves a correction that depends on the field’s frequency and the actual dimensions of the probe. We have developed a model that can reliably account for the spatial averaging correction in the field produced by circular sources and we are in the process of extending this model to account for rectangular shaped sources, similar to those encountered in clinical practice. This work is of immediate importance in minimizing the uncertainty in determining the two (FDA approved) key safety parameters: Mechanical (or Cavitational) Index and Thermal Index. Next Generation of Enhanced Bandwidth Polymer Transducer for Medical Imaging: Our goal is to provide a non- resonantly operating imaging transducer that has bandwidth significantly larger and pulse-echo sensitivity on a par or better than that achievable with current resonant PZT design. The increased bandwidth will allow the operator to control imaging frequency without a need to change transducers and facilitate harmonic imaging. Harmonic imaging provides increased resolution images and is widely used in clinical applications in conjunction with acoustic contrast agents (See Dr. M.A. Wheatley’s research). Ultrasound Transducer Design Remote Reconstruction of Surface Velocity: The method developed allows remote reconstruction of the surface velocity of any vibrating structure (e.g., imaging transducer). The image on the left is the reconstruction of a focused “half-moon” Doppler probe. Specialty Ultrasound Therapeutic Transducers: These transducers are designed for specific applications, including prostate treatment. They employ low frequency ultrasound and are designed for both transrectal and transurethral treatment. Interaction of Ultrasound and Biological Tissue: This major activity focuses on the development of piezoelectric devices for ultrasound energy delivery and models capable of predicting propagation of acoustic waves in inhomogeneous media, such as tissue. The primary impact of this work will occur in the field of both diagnostic and therapeutic applications of ultrasound energy, such as accelerated wound healing or management, using bioacoustic sensors/actuators. Faculty: S. Adrian, Ph.D., P. Bloomfield, Ph.D., V. Genis, Ph.D., R. Lec, Ph.D., P. Lewin, Ph. D., (Director, Biomedical Research and Education Center), M. Wheatley, Ph.D.; Key Collaborators: B. Goldberg, MD, F. Forsberg, Ph.D., Thomas Jefferson University, J. Reid, Ph.D., M. Shankar, Ph.D., Drexel U (ECE); Graduate Students: V. Devaraju, M. Sc. Bm. E. and E. Radulescu, M. Sc. E.E.; Close Collaboration With: Biosensors Laboratory and Optics Laboratory, DrexelUniverstiy; Division of Ultrasound, Thomas Jefferson University.

School of Biomedical Engineering, Science & Health Systems V 1.0 SD [020307] CHARACTERIZATION OF PIEZOELECTRIC IMAGING TRANSDUCERS & MATERIALS The swept frequency approach (Time Delay Spectrometry – TDS) allows transducer characterization and material attenuation measurements to be performed as nearly continuous functions of frequency. The measurements are carried out routinely from 250 kHz up to 40 MHz. Recently the range has been extended to 60 MHz. Current research is focused on extending bandwidth to 100 MHz and independent verification of the data using optical measurements. Typical applications: ultrasound metrology, assessment of safety of ultrasound imaging systems, specialty transducer design, and non-destructive testing. PROJECTONEPAGERPROJECTONEPAGER Faculty/Contact: Peter A. Lewin, Ph.D., Drexel University. Collaborators: P. Mohana Shankar, Ph.D., Drexel University; Vladimir Genis, Ph.D., Drexel University; E. Radulescu, Graduate Student, Drexel University. Laboratories: Ultrasound Laboratory; Ultrasound Transducer Research Facility; Diagnostic Ultrasonics and Signal Processing Laboratory. Support: NIH Simulated Radiation Directivity Pattern Bilaminar Hydrophone Frequency Response

School of Biomedical Engineering, Science & Health Systems V 1.0 SD [020307] DESIGN OF & CALIBRATION OF MINIATURE PIEZOELECTRIC POLYMER ULTRASONIC HYDROPHONIC PROBES Such probes are indispensable for acoustic field characterizations. Available hydrophones are usually calibrated at discrete frequencies only. Such calibration is inadequate, as it fails to detect possible rapid variations in the sensitivity of the probes. We have developed unique probe calibration methods, which plot sensitivity as a virtually continuous function of frequency up to 60 MHz; they are now being extended to 100 MHz. PROJECTONEPAGERPROJECTONEPAGER Miniature Needle-type Wideband PVDF Hydrophone Probe Faculty/Contact: Peter A. Lewin, Ph.D., Drexel University. Collaborators: P. Mohana Shankar, Ph.D., Drexel University; E. Radulescu, Graduate Student, Drexel University. Laboratories: Ultrasound Laboratory; Ultrasound Transducer Research Facility; Diagnostic Ultrasonics and Signal Processing Laboratory. Support: NIH

School of Biomedical Engineering, Science & Health Systems V 1.0 SD [020307] EVALUATION OF SPATIAL AVERAGING CORRECTIONS Ideal characterization of acoustic fields would require an actual point probe or receiver. Since all available probes have finite aperture, a faithful reproduction of the acoustic pressure-time waveform involves a correction that depends on the field’s frequency and the actual dimensions of the probe. We have developed a model that can reliably account for the spatial averaging correction in the field produced by circular sources and we are in the process of extending this model to account for rectangular shaped sources, similar to those encountered in clinical practice. This work is of immediate importance in minimizing the uncertainty in determining the two (FDA approved) key safety parameters: Mechanical (or Cavitational) Index and Thermal Index. PROJECTONEPAGERPROJECTONEPAGER Faculty/Contact: Peter A. Lewin, Ph.D., Drexel University. Collaborators: P. Mohana Shankar, Ph.D., Drexel University; E. Radulescu, Graduate Student, Drexel University. Laboratories: Ultrasound Laboratory; Ultrasound Transducer Research Facility; Diagnostic Ultrasonics and Signal Processing Laboratory. Support: NIH

School of Biomedical Engineering, Science & Health Systems V 1.0 SD [020307] NEXT GENERATION OF ENHANCED BANDWITH POLYMER TRANSDUCER FOR MEDICAL IMAGING Our goal is to provide a non-resonantly operating imaging transducer that has bandwidth significantly larger and pulse-echo sensitivity on a par or better than that achievable with current resonant PZT design. The increased bandwidth will allow the operator to control imaging frequency without a need to change transducers and facilitate harmonic imaging. Harmonic imaging provides increased resolution images and is widely used in clinical applications in conjunction with acoustic contrast agents (See Dr. M.A. Wheatley’s research). PROJECTONEPAGERPROJECTONEPAGER Faculty/Contact: Peter A. Lewin, Ph.D., Drexel University. Collaborators: P. Bloomfield, Ph.D., Drexel University; V. Devaraju, Graduate Student, Drexel University. Laboratories: Ultrasound Laboratory; Ultrasound Transducer Research Facility; Diagnostic Ultrasonics and Signal Processing Laboratory. Support: NIH 3D image of rabbit kidney with contrast injected IV. Note excellent vessel definition.

School of Biomedical Engineering, Science & Health Systems V 1.0 SD [020307] REMOTE RECONSTRUCTION OF SURFACE VELOCITY The method developed allows remote reconstruction of the surface velocity of any vibrating structure (e.g., imaging transducer). The image below is the reconstruction of a focused “half-moon” Doppler probe. PROJECTONEPAGERPROJECTONEPAGER Faculty/Contact: Peter A. Lewin, Ph.D., Drexel University. Collaborators: V. Genis, Ph.D., Drexel University; E. Radulescu, Graduate Student, Drexel University. Laboratories: Ultrasound Laboratory; Ultrasound Transducer Research Facility.

School of Biomedical Engineering, Science & Health Systems V 1.0 SD [020307] SPECIALTY ULTRASOUND THERAPEUTIC TRANSDUCERS These transducers are designed for specific applications, including prostate treatment. They employ low frequency ultrasound and are designed for both transrectal and transurethral treatment. PROJECTONEPAGERPROJECTONEPAGER Specialty Ultrasound Therapeutic Transducers for Prostate Treatment Faculty/Contact: Peter A. Lewin, Ph.D., Drexel University. Collaborators: V. Genis, Ph.D., Drexel University; B. Goldberg, MD, Thomas Jefferson University; F. Forsberg, Ph.D., Thomas Jefferson University. Laboratories: Ultrasound Laboratory; Ultrasound Transducer Research Facility.

School of Biomedical Engineering, Science & Health Systems V 1.0 SD [020307] INTERACTION OF ULTRASOUND & BIOLOGICAL TISSUE This major activity focuses on the development of piezoelectric devices for ultrasound energy delivery and models capable of predicting propagation of acoustic waves in inhomogeneous media, such as tissue. The primary impact of this work will occur in the field of both diagnostic and therapeutic applications of ultrasound energy, such as accelerated wound healing or management, using bioacoustic sensors/actuators. PROJECTONEPAGERPROJECTONEPAGER Faculty/Contact: Peter A. Lewin, Ph.D., Drexel University. Collaborators: R. Lec, Ph.D., Drexel University; V. Genis, Ph.D., Drexel University; B. Goldberg, MD, Thomas Jefferson University; F. Forsberg, Ph.D., Thomas Jefferson University. Laboratories: Ultrasound Laboratory; Ultrasound Transducer Research Facility; Diagnostic Ultrasonics and Signal Processing Laboratory.