Professor Tim Hall is retiring after 22 years in the Department of Medical Physics. Through his time as both a graduate student and faculty member, Dr. Hall has contributed an invaluable amount of research and leadership in the field of quantitative imaging.
He was first introduced to Madison in the 1980s as an undergraduate physics major when he was presented with an opportunity to work with John Cameron on a project related to air ion concentrations near high-voltage power lines.
“I got to know many of the medical physics faculty members and their wives (John Cameron, Herb Attix, Paul DeLuca, Bill Zarnstorff, Chuck Mistretta, Jerry Nickles, Jim Zagzebski) and thoroughly enjoyed being here,” says Hall. “The combination of physics and (near) immediate impact on lives was exciting. The natural next step was to come here for grad school and pursue a PhD.”
Hall received a PhD in medical physics from the University of Wisconsin–Madison in 1988 and then set off to work with a former colleague who was working at the University of Kansas Medical Center. After 15 years in Kansas, he returned to UW–Madison as a professor in 2003.
“I returned to UW-Madison because I wanted to be in an environment rich in resources including a talented pool of graduate students to work with. The ultrasound group, led by Jim Zagzebski and Ernie Madsen, had a long tradition of cutting-edge research and I wanted to contribute,” says Hall.
His research interests over the years covered several areas of applied ultrasound physics including development of methods for estimating new quantitative ultrasound parameters based on the underlying physics of acoustic wave propagation. Most notable are the various methods for estimation of backscatter coefficients and the “effective scatterer size,” and various methods for measuring the nonlinear viscoelastic properties of in vivo tissues as well as contributing to improved methods for measuring other tissue properties such as acoustic attenuation.
These developments extended from the derivation of parameters and methods to estimate them, to development of test materials for quantifying the technical performance (bias, linearity, and components of estimate variance) of these parameter estimates in known media (phantoms), to implementation on clinical imaging systems and clinical trials of their performance in human subjects.
He reflects on the ways that quantitative imaging has evolved over the course of his career.
“There have been incredible advancements in medical imaging since I started graduate school. When I started graduate school (1984), Chuck Mistrettta’s group had established digital subtraction angiography but was troubled with writing data fast enough to disk to store the information. Our ultrasound group was writing data to, as I recall, 16″ platters that stored 2 MB of data, cost $10,000 each and typically crashed every year or two and needed to be replaced. Thankfully, technology has caught up with our needs (at least for now).
Specifically for ultrasound, conversion from analog to digital system design, miniaturization of systems and architecture, and the vast array of other technical improvements have allowed for an even wider variety of software tools to improve imaging and aid in diagnosis.
Central to my own work have been the advancements in quantitative imaging. Think of an imaging system, for some tasks, as a ‘measurement device’ instead of a fancy ‘camera’. As physicists, we know metrology (the science of measurement) and can apply that to image data.
The concept of objective, system-independent estimates of tissue properties have, over the years, expanded from an ultrasound-centric effort among a few groups to a worldwide effort involving all stakeholders in the medical imaging community across all modalities.”
In addition to his role as professor, Hall also served as interim chair of the Department of Medical Physics from 2020-2021. He is a member of many professional organizations including Fellow of the American Institute of Ultrasound in Medicine, and Fellow of the American Institute for Medical and Biological Engineering.
Hall will officially finish up his work at UW–Madison this spring and plans to spend more time pursuing his passion for scuba diving. He leaves some advice for the next generation of leaders.
“My advice to everyone is to find your passion and pursue it. We spend too much of our lives working to not enjoy what we do.”