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Professor Kirk Shung looks to improve ultrasound scanners, often regarded as a form of "medical sonar."
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Kirk Shung, Dean's Professor in Biomedical Engineering |
The birth of ultrasound occurred in 1877 when Pierre Curie discovered piezoelectricity, the shrinking and expansion of a piezoelectric crystal that occurs when electric voltage is applied across the crystal. This causes the crystal to vibrate and send out ultrasonic waves. By measuring the rate at which the waves are sent and reflected back by objects, an image can be produced of underwater ship wrecks or even internal organs.
Ultrasound devices found in clinics typically range from 2.5 to 15 MHz. Here, at USC Viterbi, Kirk Shung, the Dean’s Professor in Biomedical Engineering, is focusing on the development of high frequency ultrasound arrays. Shung is currently working on a 30 MHz linear array and ultrasound arrays going up to 80 MHz.
Compared to the ultrasound devices on the market, Shung’s higher frequency arrays will allow in depth analysis of smaller or superficially structured organs like the eye and skin. In addition to clinical medicine, the higher frequency arrays can also be used for preclinical or small animal imaging. The higher frequency accounts for better spatial resolution that will allow clinicians to look at smaller anatomical structures.
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80 MHz Array (Image: Courtesy of Kirk Shung) |
Shung is looking to further expand his work to 80 MHz frequency by mounting an array onto a biopsy needle. Biopsy needles are used to gather tissues in tumors to determine whether the tumor is malignant or benign. By mounting the ultrasound device onto the needle, physicians will be able to see the tissues surrounding the needle in real time to minimize sampling errors. This technology has been coined “virtual histology.” Currently, the targeted lesion is breast cancer. A Ph.D. student, Thomas Cummins, is working on this project in collaboration with two breast radiologists at Keck School of Medicine of USC, Drs. Mary Yamashita and Linda Larson.
Another of Shung’s projects involves intravascular imaging of blood vessels. Current clinical devices require a catheter to be inserted into a vessel in order to observe the anatomy of the vessel walls. This process is frequently used to determine the degree of stenosis and the nature of the atherosclerotic lesion in arteries, including coronary arteries. A drawback of the device is that it only offers cross-sectional view of the blood vessel; there is a blind spot in the front. When the catheter is introduced into the vessel with a guide wire, puncture of the vessel wall or lesion may occur. To solve this problem a Ph.D. student, Nester Cabrera Munoz, is designing and building a forward looking catheter consisting of a miniature 30 MHz phased array mounted at the tip of the catheter.
