|Aurora Breast MRI shows multicentric cancer with at least 11 separate tumors in the left breast, while a previous mammogram showed multiple densities.|
Magnetic resonance imaging of the breast serves a unique and important function in the battle against breast cancer. This adjunct to mammography and ultrasound often provides vital information for specific circumstances, such as screening women at high risk of breast cancer, and computer aided detection (CAD) for MRI enables additional valuable clinical insight.
While CAD used in mammography focuses on detection of suspicious areas, CAD for MRI provides exquisite detail about lesions that have been detected in prior activity. The way a lesion reacts to contrast injections as well as the morphologic details that are revealed by tools in CAD assist in the management of breast disease.
Who to scan
Elsie Levin, MD, medical director of the Faulkner Sagoff Breast Imaging and Diagnostic Center at the Brigham and Women’s/Faulkner Hospital in Boston explains four primary indications for breast MRI. “Probably 50 percent of my breast MR now is high-risk screening for patients who are documented BRCA1 or BRCA2, patients who have a personal history of breast cancer [especially if they had a lumpectomy and their original cancer was not seen on mammogram], or for those with a strong family history of breast or ovarian cancer.” The final category involves young women who survived Hodgkin’s disease, if they were diagnosed in adolescence and received radiation.
For another group, newly diagnosed breast cancer patients, MRI is helpful for biopsy guidance or surgical planning. MRI reveals additional lesions in about one third of those patients, and in about half of that group it will change surgical management, not necessarily converting the plan to mastectomy, but perhaps a wider local excision based on MR findings.
Levin is using the Aurora 1.5T Dedicated Breast MRI System with CAD capabilities built into the workstation. Some of the features she appreciates include the ability to re-register images to manage patient movement between sequences, multiplanar reconstruction with the click of a button that provides 3D views of morphology, and the ability to produce a MIP (maximum intensity projection) that can be rotated, which surgeons find quite valuable.
The Aurora system includes a 1.5T magnet, patient table, RF and gradient coils that have been optimized specifically for breast imaging. It features an ellipsoid shim that is capable of including bilateral breast and axillary regions simultaneously. In addition, the system offers ductal tissue suppression, which means that it is particularly beneficial for younger women with dense breasts.
David R. Gruen, MD, medical director of the Suite for Women’s Imaging at Norwalk Radiology in Connecticut explains that the functionality of MRI CAD is quite different from CAD for mammography.
CAD for MRI does not identify suspicious lesions, but provides a means to review the huge image data sets more efficiently, and identifies important morphologic features of tumors.
If you are doing eight to 15 diagnostic breast MRIs a day, and you expect that each study has upwards of 2,000 images, there is no way you can review that many images in a usable accurate way, without CAD, Gruen explains. They use Confirma CAD that allows review of images in a timely manner. Before CAD, they spent 20 to 25 minutes on each study, but with CAD, they have cut the time spent per study to 10 to 12 minutes.
CAD supplies a process to automate the evaluation of kinetics of the lesion. A breast MRI study includes injection of a contrast agent with evaluation of uptake and wash out via the vasculature of the lesion. Malignancies tend to create new vasculature, so they gain contrast quickly and lose it quickly. CAD synthesizes the data, overlays enhancement characteristics on the data and generates a curve of the dynamic enhancement.
Mark T. Lawton, MD, director of mammography services for St. Joseph Regional Medical Center in Milwaukee is using the Invivo DynaCAD system with the Philips 1.5T Intera scanner not only to assess kinetic properties of lesions, but to delineate their morphology as well.
He explains that often cancer is not necessarily a single mass, but will present as a regional distribution with an interrupted pattern of scattered areas of suspicious enhancements. By using the 3D tools in their CAD, they gain valuable information that informs a variety of interventions.