Optical Near Infrared Imaging; From breast cancer imaging to monitoring phase transition in adipose tissues
Near infrared spectroscopy (NIRS) and diffuse optical tomography (DOT) have emerged as promising functional imaging techniques sensitive to cancer-induced pathological changes in tissue related to angiogenesis and flow/metabolism imbalances. Encouraging results have been reported for both cancer diagnosis and neoadjuvant chemotherapy monitoring. In this talk, I will introduce the principles of NIRS and DOT and present the applications of Near Infrared Spectroscopy in breast imaging and therapy monitoring. I will also introduce another innovative application of NIRS in monitoring phase transition in subcutaneous adipose (fatty) tissue during cryo-procedures.
First application: Near infrared dynamic diffuse optical tomography measurements of breast hemodynamics during fractional mammographic compression offers a novel contrast mechanism for detecting breast cancer and monitoring chemotherapy. Tissue viscoelastic relaxation during the compression period leads to a slow reduction in the compression force and reveals biomechanical and metabolic differences between healthy and lesion tissue. We measured both the absolute values and the temporal evolution of hemoglobin concentration during 25-35 N of compression for 22 locally advanced breast cancer patients scheduled to undergo neoadjuvant chemotherapy. We also characterize these novel breast cancer biomarkers for monitoring neoadjuvant chemotherapy (NACT) and predicting outcome. Specifically, I will report a 27 patient pilot study in which NACT patients were imaged using Dynamic Tomographic Optical Imaging (DTOBI) to quantify the hemodynamic changes due to partial mammographic compression.
Second application: Monitoring the kinetics of phase transition (freezing) in adipose tissue and formation of lipid crystals is important in Cryo-procedures such as cryosurgery or Selective Cryolipolysis (SC). In this work, we exploited a Near-Infrared Spectroscopy (NIRS) method to monitor the onset of fat freezing. Concurrent measurements of NIRS and MR Spectroscopy during cooling/heating cycles were performed in the MR scanner to compare the optical scattering and MR spectral changes versus temperature over time to characterize the onset of phase transition.