Understanding quantitative transmission ultrasound.

In this real patient scan, the QT algorithm systematically characterizes and strips away normal tissues to expose the underlying suspicious mass.

How Does Quantitative Transmission Ultrasound Work?

Quantitative transmission (QT) ultrasound works by transmitting pulse pressure-waves of sound through objects, allowing sound energy to be measured by high-resolution receivers on the opposite side of the object. This differs from standard reflection or B-Mode ultrasound which uses a single transducer to both transmit and measure the signal, which is reflected back toward the original source. Propagating the wave through the object allows the full effects of refraction, diffraction and attenuation to be transmitted to and displayed by the receiver.

While transmission ultrasound has been investigated as an adjunct to mammography for 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 multi-modality system (transmission and reflection). Multiple transmission acquisitions are acquired for 180 angles as the transmitter is rotated fully around the subject. Reflection data from the reflection transducers is interleaved between the transmission acquisitions. The result is a 3D speed-of-sound (SOS) image and an artifact-free reflection tomogram. The SOS image is useful diagnostically by itself. With refraction correction, contrast resolution under 100µm is commonly achieved in compounded B-Mode reflection images.

A SOS QT Ultrasound breast scan showing multiple cysts in a very dense breast

What has the FDA approved this technology for?

The QTultrasound Breast Scanner is approved for use as an ultrasonic imaging system to provide reflection-mode and transmission-mode images of a patient’s breast. It is not intended to be used as a replacement for screening mammography.

What are the results of clinical research for transmission ultrasound?

Clinical anatomy studies and correlations
QTscan correlations with cross-sectional anatomy of human female breasts discriminates different tissue types within the breast. A study comparing mammography (XRM) with QTultrasound found that QTultrasound identified all major anatomical features of the breast and that SOS calculations showed specific values for breast tissues, with a linear discriminant analysis showing an overall accuracy of 91.4%. Additionally, radiologists using a visual grading analysis scored the image quality of QTultrasound as better in 69%-90% of breasts for specific tissues. Conclusions: QTultrasound provides accurate anatomic information and high tissue specificity using speed of sound information. Quantitative transmission ultrasound can distinguish different types of breast tissue with high resolution and accuracy.2

Clinical comparison with hand held reflection ultrasound
Up-and-coming ultrasound technology shows prowess as mammography adjunct.
May 24, 2017 | Dave Pearson | Breast Imaging

The emerging imaging technology called quantitative transmission (QT) ultrasound has shown its utility as an aid in distinguishing cysts from solid lesions in the breast, according to a study published online May 23 in Academic Radiology. Researchers at the Cleveland Clinic and from QTultrasound Labs of Novato, Calif., which is developing the technology and sponsored the study, trained 14 experienced radiologists on the tool, then had them interpret 37 blinded, randomized lesions as seen on mammography and transmission ultrasound.

The QTultrasound scanner under review works by producing reflection B-mode and transmission images in three dimensions—coronal, axial and sagittal views, the authors explain. For the study, the team confirmed solid lesions with pathology results and cysts with imaging from handheld ultrasound. They found the radiologists were able to use the QT images to tell a cyst from a solid lesion with an average reader accuracy of 0.920. Further, the mean reader sensitivity and specificity with QTultrasound were 0.933 and 0.858, respectively.

These results pointed to “the importance of further study with this novel true three-dimensional automated technology for improving specificity while maintaining high sensitivity in order to prevent false-positive biopsies and ultimately provide quality breast care,” the authors wrote in their discussion. “We believe that transmission ultrasound imaging can be used as an adjunct to mammography to improve the sensitivity and specificity of the breast screening process,” they add. Academic Radiology has posted the study in full for free.3

Clinical studies of breast cyst fluid The purpose of this work is to determine if the speed of sound value of a breast cyst can aid in the clinical management of breast masses. Cyst fluid samples were obtained from 37 patients as part of a case-collection study for ultrasound imaging of the breast. The speed of sound of each sample was measured using a quantitative transmission ultrasound scanner in vivo. Electrolytes, protein, cholesterol, viscosity, and specific gravity were also measured (in the aspirated cyst fluid) to assess their relationship to the speed of sound values obtained during breast imaging. There were positive correlations between viscosity and cholesterol (r = 0.71) and viscosity and total protein × cholesterol (r = 0.78). Additionally, we performed direct cell counts on cyst fluids and confirmed a positive correlation of number of cells with speed of sound (r = 0.74). The speed of sound of breast macrocysts, as observed using transmission ultrasound, correlated with the cytological features of intracystic cell clumps. On the basis of our work with speed as a classifier, we propose a spectrum of breast macrocysts from fluid-filled to highly cellular. Our results suggest high-speed cysts are mature macrocysts with high cell counts and many cellular clumps that correlate with cyst microanatomy as seen by transmission ultrasound.4

Clinical trial results A series of blinded reader studies comparing QT scans to mammograms have been carried out. These results demonstrate improvements in sensitivity and specificity with 2D and 3D X-ray mammography and will be presented at meetings and published in peer-reviewed journals soon. Physicians may contact QTultrasound to receive additional information.

Sources:

1. Klock JC, Lenox MW, Wiskin JW, Malik B, Natesan R. Transmission Ultrasound Using 3D Inverse Scattering. Open Access E Book on Emerging Trends in Ultrasound. June 2018

2. John C. Klock, Elaine Iuanow, BilalMalik, Nancy A. Obuchowski, JamesWiskin, and Mark Lenox. Anatomy-Correlated Breast Imaging and Visual Grading Analysis Using Quantitative Transmission Ultrasound. International Journal of Biomedical Imaging Volume 2016, Article ID 7570406, 9 pages

3. Elaine Iuanow, MD, Kathleen Smith, MBA, Nancy A. Obuchowski PhD†, Jennifer Bullen MS† and John C. Klock, MD. Accuracy of Cyst vs. Solid Diagnosis in the Breast Using Quantitative Transmission (QT) Ultrasound. Academic Radiology 2017 Vol 24:1148-1153; doi: 10.1016/j.acra.2017.03.024. Epub 2017 May 23; PubMed ID 28549870. Academic Radiology has posted the study in full for free.

4.Malik B, Klock JC. Breast Cyst Fluid Analysis Correlations with Speed of Sound Using Transmission Ultrasound