Breast Imaging Research
The Division of Breast Imaging at the Medical University of South Carolina (MUSC) is actively engaged in helping test new technology that could one day revolutionize the way that breast cancer is diagnosed. MUSC breast imaging researchers are currently involvedin assessment of quantitative analysis tools applied to digital mammography, clinical usefulness of three-dimensional x-ray imaging systems, and development of x-ray imaging systems that explore alternative contrast mechanisms that can ideally result in diagnostic quality imaging at greatly reduced radiation dose.
Abid Irshad, M.D., Director of Breast Imaging, is helping to test software (QuantraTM Volumetric Assessment; Hologic, Bedford, MA) that will provide a quantitative basis for breast tissue composition automatically from mammographic images. Approved in October 2011 by the US Food and Drug administration for research, Quantra estimates volumes in the breast and calculates the volumetric fraction of fibroglandular tissue, which typically is denser than other breast tissue. Knowing the proportion of fibroglandular tissue to whole breast volume is important because denser tissue has been associated with an increased risk of breast cancer. Dr. Irshad is testing the internal consistency of Quantra measurements, comparing Quantra to other methods of breast density assessment and helping optimize the technology. Dr. Irshad and his colleagues have also shown that ultrasound imaging features of breast cancers can be used to predict whether a cancer is receptor positive or negative, forging an important link between imaging and pathology findings.
Etta Pisano, M.D., Professor of Radiology at MUSC, has research efforts focused on clinical assessment and R&D of new breast imaging technologies. She was principal investigator of the landmark American College Radiology Imaging Network (ACRIN) trial comparing digital and film mammography, which showed both technologies to have similar overall diagnostic efficacy but digital mammography to be more sensitive in younger women (<50 years old), pre- or perimenopausal women, and women with dense breast tissue and is now developing a similar multicenter clinical trial surrounding digital breast tomosynthesis (DBT). DBT, a technology that is based on digital mammography system platform, is a three-dimensional imaging x-ray modality where multiple limited-angle projections are acquired from the standard cranio-caudal and medial lateral oblique mammographic screening positions under compression (Figure 1). These projection images are reconstructed into slices allowing for z directional viewing of the mammographic breast tissue. This technology is seen as a means of peering through layers of overlapping breast tissue that may be obscuring the visibility of breast lesions. As it is currently FDA approved, digital breast tomosynthesis would be performed at the time of screening mammography, providing supplemental information that hopefully enhances diagnostic precision.
Figure 1: Digital Breast Tomosynthesis slice (left) of MLO view and corresponding conventional digital MLO mammogram (right)
Dedicated Breast Computed Tomography (DBCT), full three-dimensional imaging of the breast is currently under clinical investigation for patients who have suspicious findings from initial screening mammography. This technology allows for full 360 degree scan of the breast without compression and is also intended to resolve the issue of overlapping tissue possibly obscuring breast cancer. Currently Dr. Amy Campbell and biomedical engineer Elodia Cole, MS are conducting laboratory based reader studies assessing DBCT (Figure 2).
Figure 2: Dedicated Breast Computed Tomography representative slice in three projection views (sagittal, transverse, and coronal) with multi-intensity projection image (MIP)
Both DBT and DBCT technologies expose patients to more radiation than two-dimensional mammography, but studies are underway at MUSC and elsewhere to optimize the quality of digital images while minimizing the dose of radiation needed to obtain those images. Breast imagers at MUSC are also helping to assess how to integrate such complex technologies into the digital archives and workflow of a mid-sized academic medical center.
Dean M. Connor, Jr., PhD and Dr. Pisano are also exploring a new breast imaging technique known as diffraction enhanced imaging (DEI),. Dr. Conor, a physicist, is currently investigating methods of optimization of DEI towards clinical system development through experiments on a operational DEI system in his lab. In contrast to traditional radiography, which relies primarily on absorption for contrast, DEI exploits two additional contrast mechanisms: refraction and ultra-small-angle scatter rejection (extinction). The small-angle nature of refraction and scatter rejection make them largely undetectable by typical x-ray technology. By incorporating crystal-based optics, DEI is able to recover refraction and extinction data that would otherwise be lost and use them to enhance contrast. Because it provides much better contrast and imaging detail of soft tissue, it shows special promise for the early detection of breast cancer. Relying on refraction and extinction, it can provide higher contrast with a lower absorbed radiation dose.