High-Speed, Multi-Modal Diffuse Optical Spectroscopic Imaging for Translational Biophotonics
Diffuse optical spectroscopic imaging (DOSI) is a non-invasive and quantitative technique to recover absolute tissue optical properties and chromophores. Over the past decade, our DOSI device has been utilized as a “one size fits all” standard bedside instrument to serve all of our research needs. In breast cancer research, we have screened dozens of patients studying the spectral profile of tumors and monitoring their response to chemotherapy. In military medicine, the same DOSI technology has been used to investigate hemorrhagic shock and novel resuscitative techniques. However, recent applications have revealed limitations of our DOSI device, requiring more capabilities than what is currently offered. In breast cancer research, more modalities are needed in order to effectively screen patients, such as a continuous imaging mode to locate contrast and generate chromophore maps, as well as a dual-channel mode to perform analysis on layered tissue. In military medicine, there is a need for a high-speed and more portable system to capture hemodynamics and metabolism of traumatically injured patients.
To meet the needs of these applications, I present advances in DOSI technology. A broadband-capable, high speed DOSI has been demonstrated on tissue-simulating optical phantoms where a buried object was successfully imaged using a continuous scan over a wide area. Separation of layers in a heterogenous phantom was also presented wherein a subsurface object was invisible from the point of view of a shallow probe, but detectable using a sufficiently deep measurement. In addition, sensitivity to layers of tissue was verified on a human participant wherein adipose and underlying muscle tissue were shown to have different deoxygenation rates under the condition of a short arterial occlusion. The metabolic rate of oxygen consumption of human thenar tissue was estimated using pulsatile hemoglobin signals captured by DOSI. Benefits of a two-channel DOSI instrument was demonstrated in a study of massive hemorrhage and resuscitative endovascular balloon occlusion of the aorta. Finally, I propose the future direction of DOSI with preliminary work developing a portable DOSI device.