Checking the Transmission
By Keith Loria
Radiology Today
Vol. 20 No. 11 P. 26

Transmission ultrasound offers a new tool for breast imaging and possibly more.

According to recent data from the Centers for Disease Control and Prevention, nearly 39 million women in the United States get mammograms every year and, for every woman with cancer, 19 are told they might have cancer when they don’t. QT Ultrasound is hoping to change that paradigm with QTscan. The QTscan has received FDA 510(k) clearance for breast imaging and is not a replacement for screening mammography.

The FDA has also granted QT Ultrasound Breakthrough Device designation for its QT Scanner, potentially offering new opportunities for earlier and more frequent screening for young women at high risk for breast cancer who have no available FDA-cleared screening options. In addition, the National Institutes of Health has awarded $16 million in funding to continue QT Ultrasound’s research.

The system uses transmission ultrasound to image the breast. Rajni Natesan, MD, MBA, QT Ultrasound’s chief medical officer, explains that transmission ultrasound is the method by which a sound wave is propagated through an object while transmitted sound energy is measured at a number of receivers on the opposite side of the object.

“This differs from standard reflection or B-mode ultrasound, which use a single transducer to both transmit and measure the signal reflected back toward the original source,” Natesan says. “By propagating the wave through the object, the full effects of refraction, diffraction, and attenuation are applied to the wave, and that information is now available at the receiver.”

While transmission ultrasound has been investigated as an adjunct to mammography for quite some time, recent developments in hardware and imaging algorithms have enabled marked improvements in spatial resolution and clinical utility.

“A clinical transmission ultrasound 3D inverse scattering imaging system uses a transmitter-receiver array pair as well as a system of reflection transceivers to create a multimodality system [for transmission and reflection],” Natesan says. “Multiple transmission acquisitions are acquired for 180 angles, as the transmitter is rotated fully around the subject.”

Reflection data are acquired in 3D from the reflection transducers and interleaved between the transmission acquisitions. The result is a 3D reconstruction image volume of speed-of-sound (SOS) and reflection tomogram. The SOS image is useful diagnostically by itself.

“The images look like you’re looking at the patient’s breast,” Natesan says. “All of the ducts and different tissue types can be isolated and examined in the breast. We use the speed of sound to separate all these tissues out.”

Because abnormalities arise in the ductal and glandular tissues, doctors examine them thoroughly. Transmission ultrasound’s ability to isolate those tissues may offer a better chance of finding an abnormality, Natesan says.

“We do this with no ionizing radiation, no compression, [and] no injection, and the process is automated and not operator dependent,” she says.

Clinical Applications
QT Ultrasound has an FDA clearance for diagnostic imaging of the breast as an adjunct to mammography, not a replacement. However, together with mammography results, Natesan says it can give a woman and her doctor a more complete view of breast health.

“It is currently being used for patients with dense breasts, where a secondary screening option may be desired; patients who require more frequent imaging without the risk of radiation; and patients with breast implants who desire a supplementary screening option or providers who want to visualize preoperative or postoperative implant placement,” she says.

Earlier this year, QT Ultrasound launched commercial scanning centers to bring its radiation-free and compression-free breast imaging technology to women in a spa-like, patient-centric environment. These QTbreasthealth imaging centers are expected to provide women a best-in-class experience built around the company’s ultrasound technology.

“For years, we’ve seen the growing trend that consumers want to be involved in decisions about their health care,” John Klock, QT Ultrasound’s CEO, said in a company release at the time of the announcement. “Now, with the QTbreasthealth centers, we’re making it easier for women to put their breast health in their own hands. This technology is especially effective for women with dense breasts—about half of all women—who may have gotten false-positives with mammography or who have been told they need additional screening.”

The QTbreasthealth centers have opened in Novato, San Jose, and Walnut Creek, California; Grand Rapids, Michigan; and Scottsdale, Arizona.

“I believe in a comprehensive, integrative, patient-centered approach for each patient I treat, including access to the most medically advanced screenings for breast health,” said radiation oncology specialist Vershalee Shukla, MD, cofounder of the Vincere Cancer Center in Scottsdale, in a press release. “I see QTbreasthealth as the perfect complement to my practice philosophy, one that empowers my patients. We are thrilled to welcome them to Vincere Cancer Center.”

Clinical Trials
In the longer term, the company hopes to develop a medical imaging platform that can be used for infants, orthopedics, and more. QT Ultrasound has a number of ongoing clinical trials and Natesan notes the company’s extensive preclinical and pilot clinical work has enabled it to model successful pivotal trials of the scanner.

“A key clinical trial is a head-to-head mammography vs QT study,” she says. “We have a number of trials that are related to image quality that are ongoing as well.”

One study is using the technology to evaluate doubling time rates in nonsuspicious breast masses. With a completion date targeted for March 2020, the multicenter case study will compare breast imaging examinations from women with nonsuspicious breast masses correlated with calculated mass doubling time using QT Ultrasound with mass histology.

“The idea is we can look at how masses are growing over time and get a sense for how quickly they are doubling in size,” Natesan says. “Masses that are doubling in size in just a couple of days are much more likely to be suspicious than masses that are either shrinking in size or are growing very slowly. Our goal is to really reduce the number of unnecessary biopsies in the breasts.”

The integration of several different disciplines, from AI to image reconstruction, has also paved the way for successful cinematic rendering of breast ultrasound.

“We think there are benefits to these types of renderings for both physicians and patients in the setting of communication and diagnoses and surgical planning, and we’re looking at future studies investigating the utility for diagnostic purposes, compared with conventional ultrasound, mammography, and volume renderings,” Natesan says. “In comparison to most other imaging modalities, QT Ultrasound is unique in that it provides quantitative information about breast tissue, which can serve as a biomarker to identify tissue pathology.”

Another case collection study will follow an adaptive design with an initially planned total enrollment of approximately 600 cases to include both benign and malignant cases, representative of all tissue densities. The images and clinical data accrued will be used for the creation of a database to facilitate future readers’ studies, publications, building teaching files, and future marketing for QT Ultrasound.

A third clinical trial will evaluate the detection and characterization of breast findings of QT Ultrasound, comparing the results with handheld ultrasound and/or digital mammography—with and without tomosynthesis. Gretchen Stipek, MD, a radiologist for the Breast Center at Todd Cancer Institute in Long Beach, California, was recruited for a reader study and intrigued by the possibilities, so she went to Nevada to take part.

“One of the problems in radiology is that a lot of things are only anatomical and not necessarily functional, so the fact that there is something that could potentially measure the transmission in a certain spot and give you more accuracy can eventually lower the amount of people you do a biopsy on,” Stipek says. “That potentially is very helpful because no one wants to go through a biopsy.”

Another thing she found interesting about it was that it would be less costly, which was also attractive.

“The more comfortable something is, the more likely people are to do it, and this is actually quite comfortable,” Stipek says. “The patients, in general, like it because nobody is touching your breast, no one is pressing on it. It’s more patient friendly in that way.”

Research continues on the QT Ultrasound, but Stipek believes that it will be utilized more in the future.

“The challenge is going to be knowing the accuracy of these measurements, whether it’s somebody who needs to have a biopsy or not, and what the accuracy of having someone finding the cancer is,” she says.

“We need data on what the cancer detection rate is and what their positive predictive value is in terms of the biopsy.”

If the technology is as good as mammography in these two instances, and Stipek is hopeful it will be, she sees it being a game-changer in the industry.

“If the technology pans out, you can possibly use it for other parts of the body as well,” she says.

— Keith Loria is a freelance writer based in Oakton, Virginia.