High-speed MRI-guided near-infrared tomography system to monitor breast hemodynamics in vivo

Diffuse spectroscopic imaging of breast cancer with near-infrared (NIR) light can be integrated into magnetic resonance imaging (MRI), to provide local molecular information about the tissue regions. Dynamics within the tissue from pulsatile blood volume and oxygenation levels can be indicative of pathogenic events such as cellular proliferation and angiogenesis. Additionally the pharmacokinetics and leakage of optical contrast agents within these tissues can be helpful in tumor diagnosis. Measurement of these events require a fast imaging system, and in this work a new data acquisition design was studied, which can greatly improve the imaging speed and realize dynamic contrast imaging with combined NIR-MRI exams.;This study demonstrates the technology and methodology to build a NIR tomography system with spectrally-encoded sources in two wavelength bands which is capable of quantifying the temporal oxyhemoglobin and deoxyhemoglobin contrast in breast tissue at a 20 Hz bandwidth. The system was integrated into a 3T MRI system through a customized breast coil interface for simultaneous optical and MRI acquisition. In this configuration, the MR images provide breast tissue structural information for NIR spectroscopy of adipose and fibro-glandular tissue in breast. System stability and noise were carefully characterized, and different reconstruction methods were compared to optimize image quality. Spectral characterization and dynamic performance of the NIR system were verified through a series of phantom experiments. Normal human subjects were imaged with finger pulse oximeter (PO) plethysmogram synchronized to the NIR-MRI system to provide a frequency-locked data reference. Both the raw data from the NIR system and the recovered absorption variation of the breast at two wavelengths showed the same frequency as the PO output, indicating that this system can recover the temporal absorption changes caused by breast hemodynamics. The system was used to spectrally characterize changes in normal fibroglandular and adipose tissue.