Advances in Enhanced Imaging
In addition to his on-campus research,
Dr. José Sánchez receives international assistance from colleagues at the University of Lyon in France, which has specialized array-based imaging equipment. Noting the time difference, Sánchez said, “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.” View a video of Sánchez discussing his imaging research at bradley.edu/go/works-Sanchez2014.
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.
Dr. José Sánchez, 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.
In ultrasound imaging, axial resolution indicates what the minimum spacing between two structures should be, helping distinguish them, he added. Imaging is 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 trade-off 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.
Sánchez, who holds undergraduate and graduate degrees from Bradley, 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 much 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. If all goes well, an educated guess would be five to 10 years.”
Sánchez’s goal is to develop an ultrasonic 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 instantaneously. 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 wave “bounces” back and is processed in a computer to create an image. 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 he needs to further research REC techniques in array-based systems.
In the future, when 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.
He said his interest in this research was piqued while earning his doctorate in electrical and computer engineering in 2010. “I pursued this field 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.”
By Bob Grimson
Photography by Ethan Zentz