High optode-density wearable probe for monitoring breast tumor dynamics during neoadjuvant chemotherapy
Sam Spink, Boston University

We present a high optode-density continuous-wave (CW) wearable diffuse optical device for the investigation of hemodynamic responses of locally advanced breast tumors during neoadjuvant chemotherapy (NAC). The goal of this work is to provide an accessible technology for assessing cancer treatment response in the hospital and home. The device consists of a rigid-flex substrate with 32 LEDs at two wavelengths (750 nm and 850 nm) and 16 detectors. It is highly flexible and can conform to the natural shape of the breast. Measurements on spatially-complex tissue-simulating phantoms were utilized to validate both simpler topographic visualizations and more complex 3-D tomographic reconstructions using the Rytov approximation. The ability to of the probe to capture spatial variation was evaluated by monitoring a channel flow phantom whose nigrosin dye concentration varied within the channel over time. The ability of the probe to capture hemodynamic responses to perturbations in vivo was validated through cuff occlusions and a normal volunteer study employing breath holds. During occlusions (n=2), we identified a mean peak increase in deoxyhemoglobin and decrease in oxyhemoglobin in the forearm of 7.65 ± 1.72 and 4.78 ± 1.22 µM, respectively. From initial volunteer data (n=4 out of 10 planned volunteers), we identified a mean rise in oxyhemoglobin of 1.71 ± 0.89 µM occurring in normal breast tissue following a 30 sec breath hold. A clinical study will commence shortly, and we aim to quantify tumor contrast during breath holds, and assess if treatment response can be determined during NAC.