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Diffuse optical imaging (DOI) may be a beneficial diagnostic method for women with mammographically dense breast tissue. In order to evaluate the utility of DOI, we are developing broadband diffuse optical spectroscopy (DOS) to characterize the functional origins of optical signals in breast cancer patients. Broadband DOS combines multifrequency intensity-modulated and continuous-wave near-infrared light to quantify tissue absorption and scattering spectra from 650 to 1000 nm. Values of intrinsic physiological properties (oxy- and deoxy-hemoglobin, water, lipid, and scatter power) derived from absorption and scattering spectra provide detailed information on breast physiology. We present the results of clinical studies of 58 stage II/III malignant breast tumors using a noninvasive, handheld, broadband DOS probe. On average, eight positions were scanned over tumor and contralateral normal breast for each subject. Intrinsic physiological properties were statistically significantly different for malignant vs. normal tissues for all subjects, without patient age or tumor size/type stratification. Breast tissues containing malignant tumors displayed reduced lipid content ( approximately 20%) and increased water, deoxy-, and oxy-hemoglobin (>50% each) compared to normal breast tissues. Functional perturbations by the tumor were significantly larger than functional variations in normal tissues. A tissue optical index (TOI) derived from intrinsic physiological properties yielded an average two-fold contrast difference between malignant tumors and intrinsic tissue properties. Our results demonstrate that intrinsic optical signals can be influenced by functional perturbations characteristic of malignant transformation; cellular metabolism, extracellular matrix composition, and angiogenesis. Our findings further underscore the importance of broadband measurements and patient age stratification in breast cancer DOI.
Diffuse optical spectroscopy (DOS) and imaging are emerging diagnostic techniques that quantitatively measure the concentration of deoxy-hemoglobin (ctHHb), oxy-hemoglobin (ctO 2Hb), water (ctH 2O), and lipid in cm-thick tissues. In early-stage clinical studies, diffuse optical imaging and DOS have been used to characterize breast tumor biochemical composition and monitor therapeutic response in stage II/III neoadjuvant chemotherapy patients. We investigated whether DOS measurements obtained before and 1 week into a 3-month adriamycin/cytoxan neoadjuvant chemotherapy regimen can predict final, postsurgical pathological response. Baseline DOS measurements of 11 patients before therapy revealed significant increases in tumor ctHHb, ctO 2Hb, ctH 2O, and spectral scattering slope, and decreases in bulk lipids, relative to normal breast tissue. Tumor concentrations of ctHHb, ctO 2Hb, and ctH2O dropped 27 ؎ 15%, 33 ؎ 7%, and 11 ؎ 15%, respectively, within 1 week (6.5 ؎ 1.4 days) of the first treatment for pathology-confirmed responders (n ؍ 6), whereas nonresponders (n ؍ 5) and normal side controls showed no significant changes in these parameters. The best single predictor of therapeutic response 1 week posttreatment was ctHHb (83% sensitivity, 100% specificity), while discrimination analysis based on combined ctHHb and ctH 2O changes classified responders vs. nonresponders with 100% sensitivity and specificity. In addition, the pretreatment tumor-to-normal ctO 2Hb ratio was significantly higher in responders (2.82 ؎ 0.44) vs. nonresponders (1.82 ؎ 0.49). These results highlight DOS sensitivity to tumor cellular metabolism and biochemical composition and demonstrate its potential for predicting and monitoring an individual's response to treatment.diffuse optical imaging ͉ frequency-domain photon migration ͉ near-infrared ͉ tissue spectroscopy ͉ translational research O ptimal management locally advanced breast cancer (LABC) remains a complex therapeutic problem (1). LABC represents 5-20% of all newly diagnosed breast cancers in the United States with a higher incidence in medically underserved areas (2). Treatment for LABC has evolved from radical mastectomy to preoperative neoadjuvant chemotherapy followed by mastectomy or breast conservation therapy (3). Despite aggressive local therapy, long-term patient survival is still poor. LABC remains controversial because of uncertainties in determining the optimal intensity and duration of neoadjuvant chemotherapy and evaluating therapeutic response (2, 4, 5).Neoadjuvant chemotherapy response is determined by serial physical examination, mammography and/or ultrasound. Complete pathological response (cPR) is an important therapeutic endpoint that is a surrogate for eradicating micrometastases, and strongly correlates with patient survival (6). Thus one goal of neoadjuvant chemotherapy monitoring is to determine early when a patient will demonstrate cPR. Many studies revealed significant discrepancies between clinical response assessments and final pathology (7-9).A rece...
A technique for measuring broadband near-infrared absorption spectra of turbid media that uses a combination of frequency-domain ͑FD͒ and steady-state ͑SS͒ reflectance methods is presented. Most of the wavelength coverage is provided by a white-light SS measurement, whereas the FD data are acquired at a few selected wavelengths. Coefficients of absorption ͑ a ͒ and reduced scattering ͑Ј s ͒ derived from the FD data are used to calibrate the intensity of the SS measurements and to estimate Ј s at all wavelengths in the spectral window of interest. After these steps are performed, one can determine a by comparing the SS reflectance values with the predictions of diffusion theory, wavelength by wavelength. Absorption spectra of a turbid phantom and of human breast tissue in vivo, derived with the combined SSFD technique, agree well with expected reference values. All measurements can be performed at a single source-detector separation distance, reducing the variations in sampling volume that exist in multidistance methods. The technique uses relatively inexpensive light sources and detectors and is easily implemented on an existing multiwavelength FD system.
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