Advanced Imaging for Breast Cancer: Screening, Diagnosis, and Assessing Response to Therapy
L MacDonald1*, T Yankeelov2*, A Karellas3*, J Boone4*, (1) University of Washington, Seattle, WA, (2) Vanderbilt University, Nashville, TN, (3) University of Massachusetts Medical School, Worcester, MA, (4) UC Davis Medical Center, Sacramento, CAWE-A-141-1 Wednesday 8:00AM - 9:55AM Room: 141
Several imaging modalities are being developed to improve early detection and diagnosis and to assist in selecting and monitoring treatments. This symposium will review advances in x-ray, nuclear, and magnetic resonance breast imaging methods.
A primary shortcoming of mammography is that anatomical overlap of dense tissues confounds diagnosis of cancerous lesions. Breast tomosynthesis (BT), now FDA approved, and dedicated breast CT (bCT), not yet FDA approved, each address this shortcoming by providing tomographic imaging. Using similar equipment that also acquires digital mammograms, BT images are reconstructed from several x-ray projection images acquired from different views (e.g. 15 projections covering 15 degree arc). In this approach the high mammographic resolution is preserved in the x,y direction (axial plane) and tomographic resolution is provided in the z-plane but with lower resolution. In bCT a flat panel detector is used in rotating cone-beam CT geometry acquiring 300-500 images over 360 degrees covering the entire breast in as little as 17 seconds; resolution is again similar to mammography and is isotropic in x,y,z. Both BT and bCT have been developed so that the radiation dose to the breast is similar to two-view mammography. Both appear to be superior to mammography for visualizing mass lesions, but not yet for visualizing microcalcifications. Improved bCT resolution, and synthetic 2D mammograms derived from BT data promise to improve the performance of each with micro-calcifications. The added complexity in BT and bCT requires more attention to the details of image acquisition, detector pixel binning, and x-ray beam pulsing. Technical aspects of BT and bCT and their evolving role in breast imaging will be discussed.
Nuclear medicine imaging can show physiological functions of lesions at the molecular level, providing complementary information to the x-ray techniques. Functional imaging offers the potential to distinguish malignant from benign processes, characterize lesions to assist in selecting therapy, and monitor therapy efficacy. Since imaging is at the molecular pathways level, changes can often be seen well before macroscopic changes to lesion size. Great potential and challenges for nuclear medicine imaging lie in the specificity and availability of radiolabeled molecular probes. Cost and systemic dose are further challenges to nuclear methods, but both single-photon and positron-emitting radiotracers show promise for diagnostic and therapeutic applications.
With the ability to provide both anatomic and functional imaging, there have been dramatic increases in the range and quality of information available from magnetic resonance imaging (MRI) methods. In particular, dynamic contrast enhanced MRI, diffusion weighted MRI, and proton MR spectroscopy have matured to the point where they can offer relevant and complimentary information on tumor status. Emerging yet promising techniques include magnetization transfer MRI, chemical exchange saturation transfer MRI, magnetic resonance elastography, and hyperpolarized MR. We will provide an overview of each of these techniques in the context of examining therapeutic response in the neoadjuvant setting. We will also briefly discuss the importance of biomarker validation, standardization and reproducibility—critical issues that must be addressed to routinely deploy these methods in the clinical setting.
1. Understand the principles and differences between breast tomosynthesis and breast CT, and the technical advantages and limitations of each.
2. Understand potential roles of nuclear medicine/PET in lesion detection, diagnosis, and therapy monitoring.
3. Identify at least three new MR techniques used to image/characterize breast cancer.
4. Appreciate the use of imaging as a biomarker and the importance of standardized image-based metrics.
Funding Support, Disclosures, and Conflict of Interest: MacDonald: NIH-NCI Grant 1R01CA163498