Imaging Technology Enhances Diagnostic Process
Research into ultrasound imaging by Dr. José Sánchez ’00 MSEE ’02 could lead to physicians in the future detecting tumors at earlier stages, pinpointing treatments toward specific cancers, and potentially making diagnoses without the need for biopsies.
While earning his doctorate in electrical and computer engineering in 2010, Dr. José Sánchez ’00 MSEE ’02 found his interest researching ultrasound imaging had blossomed. “I pursued this area because of my passion with signal processing and its potential to improve medical technology,” said Sánchez, who survived a rare form of testicular cancer. “My mentality going in, and as a cancer survivor, was any contribution that could impact people’s lives is critical. Add signal processing, and you have a match made in heaven.”
Thanks to his work, physicians in the future may detect tumors at earlier stages and pinpoint treatments toward specific cancers — possibly even make diagnoses without the need for biopsies.
The assistant professor of electrical and computer engineering explained that spatial resolution, or the overall detail, is a factor affecting the quality of an ultrasonic image. Improving that detail has the potential to improve the diagnostic qualities of ultrasound images.
He added that in ultrasound imaging, axial resolution is a measure indicating what the minimum spacing between two structures should be, helping distinguish them.
It’s improved as the ultrasound system’s bandwidth increases. High-frequency systems tend to have larger bandwidth, but as frequency increases, the sound intensity decreases while there also is a reduction in the depth of penetration.
To deal with this tradeoff between spatial resolution and penetration depth, the amplitude can be increased for the excitation signal. That increase in power also increases pressure that could have side effects, such as heating or damaging body tissue.
Achieving Better Imaging
Sánchez is seeking a way to improve image quality using coded excitation and a pulse compression technique known as resolution enhancement compression (REC). This approach not only increases the transmitted energy while minimizing power but also enhances bandwidth to improve axial resolution.
“There is still a lot of research to be completed before we can push this technology onto clinical scanners,” he said about the timeline for his work. “I am just beginning to look into REC and hybrid coded excitation techniques on ultrasonic array-based systems. The results so far are very promising; if all goes well, an educated guess would be five to 10 years.”
Sánchez’s goal is to develop an ultra-sonic imaging system that transmits a pre-enhanced “chirp,” the coded excitation waveform used in REC. Through senior projects with Bradley students, he has worked on the platform for coded excitation and real-time processing of data with a general purpose graphic processing unit (GPGPU). “With single-element sources, research could take up to an hour,” Sánchez noted. “With a multiple-element source, it can be done quickly and in real time. Because we need to compress the received signal, more processing is required. Using a GPGPU, we are able to process the data in real time as a conventional system would.”
Now, he is acquiring data and developing digital signal-processing technology to transmit amplitude- and frequency-modulated coded signals using multiple-element sources to make imaging equipment smaller, less expensive and more accurate.
A waveform generator is used to produce electric impulses. Electric voltage is put through a transducer that converts it to a pressure wave. Then, that “bounces” back and is processed in a computer to create an image. Each transducer has its own individual response. Newer transducers have larger bandwidth, Sanchez noted, but there is room to improve. “We can improve resolution, we can improve contrast, and we can improve penetration depth,” he said about using the REC technique.
He works to encode those electric impulses with a special binary code that affects the impulses and, hopefully, results in a better ultrasound image.
Detecting Tumors Earlier
Sánchez also researches quantitative ultrasound techniques (QUS), which are used to study the microstructure of tissue and may allow doctors to detect some cancers, usually those that are not too deep in the body such as breast, thyroid, prostate, cervical and testicular tumors. Differentiating between tumors might be improved by using coded excitation techniques, but Sánchez said he needs to further research REC techniques in array-based systems.
In the future, when the REC research moves into the medical community, it could provide doctors with more information through better resolution of images, improved contrast and automatic tumor delineation. “All my work up to last year was focused on using a single-element source,” Sánchez said, adding that these sources are the simplest way to test the physics of the problem but have limitations that prevent them being used in a clinical setting. Using a larger, array-based ultrasound system is complicated by the cost, limited availability or limited function.
His research received an international assist when a colleague at the Universidad Catolica de Peru went to France to conduct research at the University of Lyon. The French facility had specialized array-based imaging equipment that aided Sanchez.
“We have a collaboration going where we can feed them this information,” he explained, noting the time difference between France and Peoria. “I wake up, and the data is waiting for me to process. This partnership gives me the opportunity to run experiments at a much quicker pace. The future involves pushing this research forward to put it into clinical machines.”
While Sánchez chose Bradley for his undergraduate work because of its reputation for providing a quality education and financial aid, he stayed for his master’s for more personal reasons: “I felt I wasn’t finished learning, and I didn’t feel that I was ready to contribute to society in the way I wanted. I needed to enhance my education to accomplish what I wanted to do.”
— Bob Grimson ’81