Improving breast cancer diagnosis by reducing chest wall effect in diffuse optical tomography

We have developed ultrasound (US)-guided diffuse optical tomography (DOT) technique to assist US diagnosis of breast cancer and to predict neoadjuvant chemotherapy response of breast cancer patients. The technique was implemented using a hand-held hybrid probe consisting co-registered US transducer and optical source and detector fibers which couple the light illumination from laser diodes and photon detection to PMT detectors. With the US guidance, diffused light measurements were made at the breast lesion site and the normal contralateral reference site which was used to estimate the background tissue optical properties for imaging reconstruction. However, background optical properties were affected by the chest wall underneath the breast tissue. In this study, we have analyzed data from 297 female patients and results have shown statistical significant correlation between fitted optical properties (μ_a and μ_s) and the chest wall depth detected by a boundary detection algorithm applied to co-registered US images (r < 0.27, p < 1.0 x 10^-4). After subtracting the background total hemoglobin (tHb) computed with μa at each wavelength, the difference between malignant and benign lesion groups has improved. The Area-under-the-ROC curve (AUC) has improved from 88.5% to 91.5% (sensitivity improved from 85.0% to 87.5% and specificity from 90.2% to 92.6%). Statistical test has revealed significant difference of the AUC improvements after subtracting background tHb values.