Multi-modality compressed breast imaging

ABSTRACT Measurement of breast tissue response to external stimulation has the potential to unveil additional dynamic biomarkers of disease states. Recently tumor contrast generated by breathing-gas induced vascular changes has been demonstrated using both BOLD imaging [1] and MRIguided near infrared diffuse optical tomography [2]. At the same time, in the biomedical optics community, temporally resolved hemodynamic changes in the breast resulting from the application of external compression are being investigated as breast cancer biomarkers [3]. Building on our previous optical compressed breast imaging studies [4], we have developed a combined MRI-optical breast compression platform to enable simultaneous dynamic optical and MRI acquisition of the post-compression dynamics. MRI and diffuse optical imaging integrate synergistically, as MRI structural images are used to guide optical reconstructions, and deoxy-hemoglobin (HbR) dependent BOLD scans can be correlated with optical HbR measurements. We describe instrumentation development and report initial dynamic MRI results from healthy volunteers. MATERIALS AND METHODS Figure 1 shows details of the compression platform. An 8-element receive phased array is mounted sagitally on hydraulically actuated compression plates. Arrays of 32 source and 32 detection optical fibers are mounted on each plate, respectively, using the space inside the coil elements. MRI markers (Beekley MR Spot) are placed at the corners of the compression plates. The protocol consists of 3-5 2 minute compressions during which the subject’s left breast is imaged simultaneously with a multi-slice EPI sequence, as well as 12 Hz continuouswave optical imaging. After 2 minutes of compression, a T1-FLASH 3D structural image is acquired to locate the optical fibers using the corner MRI markers in conjunction with the known relative fiber locations on the two plates. Optical imaging co-registration algorithms are currently under development, thus we report on the temporal characteristics of the breast BOLD signal below.