51st AAPM Annual Meeting
James A. Zagzebski, PhD, University of Wisconsin, Madison, WI, 53705-2275, US
For more information about the American Association of Physicists in Medicine, visit aapm.org/

AbstractID: 11976 Title: Harmonic Imaging
The purpose ofthis course isto acquaint participants with recentsignal processing
techniques and modes on ultrasound instruments. Emphasisis on second harmonic
imaging, a processing and displaymode implemented on mostscanners. Harmonic
imaging was originally applied to enhance echo signals due to nonlinearscattering by
ultrasound contrast agents. However, the modality is much more commonly used in
“native tissue harmonic” mode, where echoes originating from nonlinear components of
propagating acoustic beams are detected and displayed. The source ofthese echo signals
and the advantages and disadvantages of harmonic imaging will be described. When
applied effectively, harmonic imaging providessignificant improvementsin image
quality compared to that obtained using conventionalsignal processing. A primary reason
for harmonic imaging´simproved image quality isreduction of acoustic noise caused by
reverberations within overlying tissues. Other contributorsto high quality ultrasound
imagesinclude spatial and frequency compounding and speckle reduction. These
techniques also will be described and placed in context with harmonic imaging.
Learning Objectives
After completing this course, participants will:
1. Describe the origin of harmonic echo signalsfor both conventional and contrast agent
imaging modes;
3.Contrast resolution and penetration capabilitiesfor harmonic imaging and linear
4. Identify clinicalsituations where harmonic imaging is used advantageously;
5. Describe how harmonic imaging is used to enhance detection of contrast agents;
6, State the benefits ofspatial and frequency compounding, and speckle reduction.

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