18/14/2015 Three-dimensional Quantitative Ultrasound Imaging A.J. Devaney Department of electrical and computer engineering Northeastern university Boston, MA “Acoustical Holography,” Encyclopedia of Applied Physics, Americal Institute of Physics “Acoustical Holography,” Encyclopedia of Applied Physics, Americal Institute of Physics A.J. Devaney Associates, Inc. 295 Huntington Ave-suite 208. Boston, MA

28/14/2015 Canonical Imaging Configuration Insonifying waveform Scattered wavefield Sensor system Quantitative imaging problem: Given set of scattered field measurements determine object function

38/14/2015 Data Model Nonlinear and nonlocal mapping from object function to scattered field Mapping from 3D to 2D thus non-unique Born approximation Rytov approximation Born approximation Rytov approximation

48/14/2015 Born Approximation Imaging scattering pointImage point “Lens” outgoing spherical waveIncoming spherical wave.

58/14/2015 Analog Two-dimensional Imaging ObjectImage x,y Lens Lens converts outgoing spherical waves into incoming spherical waves to produce the image field.

68/14/2015 Backpropagation Imaging Sensor system aperture Scattered wavefield Object 1.Measure wavefield over aperture 2.Compute plane wave amplitude (FFT) 3.Perform plane wave expansion (FFT) Sensor system aperture Backpropagated wavefield Image

78/14/2015 Backpropagation--the Acoustic Lens Sensor system Backpropagated wavefieldScattered wavefield ObjectImage Single experiment generates image of the product

88/14/2015 The backpropagation Algorithm Sensor system aperture Scattered wavefield Object Sensor system aperture Backpropagated wavefield Image

98/14/2015 The backpropagation Point Spread Function Point spread function is the image of a point (delta function) scatterer Wave aberration function models sensor and computational inaccuracies spherical waveSensor system aperture backpropagated spherical wave

108/14/2015 Point Spread Function Ideal Case : = 4  steradians Zero aberration and Point spread functionCoherent transfer function

118/14/2015 Improving Image Quality confocal Ultrasound Imaging source array detector array High quality image Focus-on-transmit and focus-on-receive Confocal mode: r=r 0

128/14/2015 Plane wave insonification Diffraction tomography source array detector array Partial image

138/14/2015 Image Quality Point spread functionTransfer function

148/14/2015 Image Processing Image processing performed directly on 3D image in confocal system Image processing performed on raw data in diffraction tomography (yields filtered backpropagation algorithm) Image processing performed directly on 3D image in confocal system Image processing performed on raw data in diffraction tomography (yields filtered backpropagation algorithm)

158/14/2015 Summary and Conclusions l Single experiment ultrasound imaging of 3D objects yields extremely low image quality l Multiple experiments via confocal scanning or diffraction tomography yields high image quality l Post image processing and algorithm optimization can improve image quality l Born approximation not adequate for strong scattering and/or extended objects l Conventional (optical) measures of image quality not appropriate for 3D ultrasound