How to overcome the limitations of today’s screening technologies
Radiologists have known for decades that the sensitivity of mammography for detecting breast cancer is lower in women with dense breasts. This remains true today even with the advent of digital breast tomosynthesis (or 3D mammography).
Ultrasound has been shown to find more cancers in women with dense breasts, but it is time and labor intensive, and often operator dependent. Moreover, its poor specificity leads to a high rate of false positives, resulting in unnecessary biopsies and added cost to the healthcare system.
Contrast-enhanced breast MRI has also been shown to detect more cancers in dense tissue. However, its low specificity generates a high rate of false positives and at a prohibitively expensive cost.
Dense breast tissue itself is not an indication for MRI. This technology is most suited for screening high-risk women, including those women with genetic mutations and/or strong family history, or who have had submental radiation to the chest to treat lymphoma during adolescence. Even among this population, radiologists are beginning to question the safety of MRI technology. In recent studies, patients with Multiple Sclerosis who have undergone multiple contrast-enhanced MRIs, demonstrated gadolinium contrast depositions in their brain tissue. The long-term clinical significance of this finding is currently unknown.
A Better Option
In recent years, researchers have been exploring how advanced imaging techniques, analogous to those used in astrophysics, could improve the specificity of ultrasound to provide a better option for evaluating dense breast tissue.
Scientists have long faced the problem that when imaging a star or galaxy, for example, the light that arrives from these objects is corrupted by the earth’s turbulent atmosphere. The atmosphere acts like a “dirty lens,” causing the images to be blurry. In conventional breast ultrasound, the patient’s tissue acts much like the earth’s atmosphere in that it corrupts the original sound signals to the point that when it gets to a tumor and back, the resulting image is blurry.
Many techniques have been developed over the years to help compensate for the earth’s atmosphere and “de-blur” images of space objects. Today, knowledge gained from these techniques is being applied to help clinicians improve the clarity of breast ultrasound imaging – especially for women with dense breasts. By learning from astrophysics, researchers have developed new technology that delivers three-dimensional whole breast ultrasound presented in tomographic coronal slices.
Benefits of 3D Ultrasound
Three-dimensional whole breast ultrasound introduces a new method for the capture and treatment of sound signals. Unlike traditional ultrasound that relies on a small, one-dimensional probe and gel, the technology employs a novel 360-degree ring transducer that surrounds and images the breast while both are submerged in water.
Due to its advanced design, the transducer is able to capture reflection echoes from all directions around the breast while receiving signals transmitted through the breast. The signals are analyzed using sophisticated algorithms that provide cross-sectional slices of the entire volume of the breast. The technology measures not only reflection but also sound speed and attenuation, and provides more information than ever before to help characterize tissue.
Sound speed and attenuation have been shown to help evaluate tissue stiffness and density, while “de-blurring” the images, for a clearer rendering of a lesion’s shape and structure, all of which can help differentiate malignant tumors from benign lesions. Research has demonstrated that increased sound speed and attenuation are often associated with breast cancer.1 In addition, greater breast density, a known factor for increased breast cancer risk, has been shown to exhibit increased sound speed.2
The first U.S. FDA-cleared 3D whole breast ultrasound technology developed with this approach is the SoftVue whole-breast imaging system [Delphinus Medical Technologies]. Currently 510(k) cleared for diagnostic imaging purposes only, SoftVue is the subject of a 10,000-patient, multi-center research project, the results of which will be used to expand the use of SoftVue for screening women with dense breast tissue in combination with mammography.
More than 500 patient scans have been performed on SoftVue to date, supporting its development and early clinical results. At RSNA 2016, researchers will share new study findings showing that images generated by SoftVue are comparable in resolution to those generated by MRI.3 In addition, the researchers will share data demonstrating that SoftVue has a positive predictive value for lesion characterization of 87 percent. 4
If the results of the large research project mimic these findings, 3D whole breast ultrasound may prove to deliver best-in-class specificity (fewer false positives) with improved sensitivity (find more cancers) – all in a safe, fast procedure with no compression or radiation.
References
- Ranger, B., Littrup, P. J., Duric, N., Chandiwala-Mody, P., Li, C., Schmidt, S., &Lupinacci, J. (2012). Breast Ultrasound Tomography Versus MRI for Clinical Display of Anatomy and Tumor Rendering: Preliminary Results. American Journal of Roentgenology, 198(1), 233-239.
- Duric, N., Boyd, N., Littrup, P., Sak, M., Myc, L., Li, C., …& Albrecht, T. (2013). Breast density measurements with ultrasound tomography: A comparison with film and digital mammography. Medical physics, 40, 013501.
- Duric, N., Sandhu, G., Roy, O., Li, C., Littrup, P.J., Sak, M., Brem, R.F. Toward high-resolution whole breast imaging using ultrasound tomography: a comparison with MRI. RSNA 2016
- Duric, N., Littrup, P.J., Brem, R.F., Yamashita, M.W. Improving specificity of whole breast ultrasound using tomographic techniques. RSNA 2016
