Research: Quantitative Ultrasound Imaging

This research is concerned with methods of improving diagnostic ultrasound. Currently, ultrasound scanners operate in a very qualitative manner. Ultrasound images are representations of the relative echo amplitude, without any consideration for comparison with an absolute scale. The images that are produces are wonderfully detailed and allow radiologists and physicians an amazing view. Recently, interest has been rekindled in "quantitative ultrasound imaging", in which images would represent numerical values of acoustical properties of tissue. This may offer the following advantages

• Enhanced diagnosis: It is known that certain diseases, inlcuding cirrhosis of the liver and some malignant cancers, change the values of acoustical properties in prescribed ways. Directly measuring these properties may enhance clinical evaluation of these diseases
• Stability of images: As ultrasonographers and scanners change, the images from current scanners may also change. Since the images only reflect relative amplitudes, there is limited ability to ensure that an image taken today with machine A will be similar to one taken tomorrow by machine B. Quantitative ultrasound imaging circumvents this difficulty by producing images that directly reflect underlying physical properties of tissue.
• Reduction of artifacts: The amplitude of an ultrasound echo is affected by two physical properties: attenuation, largely the absorption of ultrasound energy by tissue, and backscatter, the scattering of sound energy back to the source. It is possible that a region with high attenuation will absorb so much ultrasound that regions below it will appear black. This is like a shadow where the light has been blocked. Because of this, little ultrasound energy is available to interact with areas below this region and thus there is little echo. This mimics a similar condition in which an area may have low backscatter and thus not produce much echo. By separating images into an attenuation image and a backscatter image (both quantitatively determined) we can prevent this "confusion" of the two possibilities.