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X-Ray, BMI, PET -- and now Photoacoustic? Grodins Lecturer Discusses Prospects

Biomedical Engineering Department faculty and students convene for a keynote address on promising new molecular imaging techniques

October 28, 2008 — Can ultrasound imaging compete with other imaging techniques, such as optics, magnetic resonance imaging (MRI) and positron emission computed tomography (PET) in capturing molecular activity?
Keynote lecturer Matthew O'Donnell, left, and Michael Khoo, chair of the Viterbi School's Biomedical Engineering Department.
Matthew O’Donnell, dean of engineering and professor of bioengineering at the University of Washington, Seattle, and guest speaker at the Biomedical Engineering Department’s Grodins Keynote Lecture on Oct. 22, believes it can if a photoacoustic approach is used.  

In his talk, “Can Ultrasound Become the Dominant Molecular Imaging Modality,” O’Donnell reviewed the successes of using photoacoustics in molecular therapy, calling it “an exacting vehicle for molecular imaging.”

Current ultrasonic imaging methods that use micro air bubbles as targeting carriers for molecular imaging are quite limited in the variety of targeting molecules that they can carry, he said.  Photoacoustic imaging, on the other hand, does not have that problem because it does not use air bubbles as carriers.  

A photoacoustic image is formed by illuminating tissues of interest with a beam of light of extremely short duration, which causes transient thermal expansion of the tissue.  An ultrasonic pulse is emitted as a result and can be detected by an ultrasonic receiver.  Its capability and image quality are determined by optical absorption of tissues and the spatial resolution of the ultrasound.  
Grodins Lecture audience.

O’Donnell, who addressed about 80 faculty and staff attending the late afternoon lecture, began his hour-long presentation with a history of medical imaging, which goes back to Alexander Graham Bell’s invention of the photophone in 1880.  The photophone allowed for the transmission of sound on a beam of light and became a precursor to modern day fiber optics.  Bell transmitted his first wireless telephone message a few hundred yards away on June 3, 1880.  The principles underlying the technique were later used by Guglielmo Marconi to develop wireless telegraphy.

O’Donnell reviewed other imaging techniques leading up to current techniques, such as magnetic resonance imaging, which uses a powerful magnetic field, radio frequency pulses and a computer to produce detailed pictures of organs, soft tissues, bone and virtually all other internal body structures.  He also discussed positron emission tomorgraphy, also called PET scans, which is a type of nuclear medicine used for imaging structures and organs.  PET imaging is particularly useful in illuminating important body functions, such as blood flow, oxygen use and sugar (glucose) metabolism, to help physicians pinpoint abnormal metabolic activity within the body.  He concluded the lecture with several examples of photoacoustic imaging that have successfully captured the activity of specific molecules.  
Professor Khoo, right, presents Matthew O'Donnell with a commemorative plaque. 

After a question-and-answer session, Michael C. Khoo, chair of the Viterbi School’s Department of Biomedical Engineering, presented O’Donnell with a commemorative plaque.

The Grodins Keynote Lecture was named for the late Fred S. Grodins, the Biomedical Engineering Department’s founding chair.  Grodins’ 1963 publication, “Control Theory and Biological Systems,” is a landmark document on the earliest applications of engineering control theory for physiological systems.