Performance assessment of diffuse optical spectroscopic imaging instruments in a 2-year multicenter breast cancer trial

We present a framework for characterizing the performance of an experimental imaging technology, diffuse optical spectroscopic imaging (DOSI), in a 2-year multicenter American College of Radiology Imaging Network (ACRIN) breast cancer study (ACRIN-6691). DOSI instruments combine broadband frequency-domain photon migration with time-independent near-infrared (650 to 1000 nm) spectroscopy to measure tissue absorption and reduced scattering spectra and tissue hemoglobin, water, and lipid composition. The goal of ACRIN-6691 was to test the effectiveness of optically derived imaging endpoints in predicting the final pathologic response of neoadjuvant chemotherapy (NAC). Sixty patients were enrolled over a 2-year period at participating sites and received multiple DOSI scans prior to and during 3- to 6-month NAC. The impact of three sources of error on accuracy and precision, including different operators, instruments, and calibration standards, was evaluated using a broadband reflectance standard and two different solid tissue-simulating optical phantoms. Instruments showed <0.0010 mm−1 (10.3%) and 0.06 mm−1 (4.7%) deviation in broadband absorption and reduced scattering, respectively, over the 2-year duration of ACRIN-6691. These variations establish a useful performance criterion for assessing instrument stability. The proposed procedures and tests are not limited to DOSI; rather, they are intended to provide methods to characterize performance of any instrument used in translational optical imaging.

Coregistration of Dynamic Contrast Enhanced MRI and Broadband Diffuse Optical Spectroscopy for Characterizing Breast Cancer

A handheld scanning probe based on broadband Diffuse Optical Spectroscopy (DOS) was used in combination with dynamic contrast enhanced MRI (DCE-MRI) to quantitatively characterize locally-advanced breast cancers in six patients. Measurements were performed sequentially using external fiducial markers for co-registration. Tumor patterns were categorized according to MRI morphological data, and 3D DCE-MRI slices were converted into a volumetric matrix with isotropic voxels to generate views that coincided with the DOS scanning plane. Tumor volume and depth at each DOS measurement site were determined, and a tissue optical index (TOI) that reflects both angiogenic and stromal characteristics was derived from broadband DOS data.

In all six cases, optical scans showed significant TOI contrast corresponding to MRI morphological information. Sharp TOI peaks were recovered for well-circumscribed masses. A reduction in TOI was found inside a tumor with a necrotic center. A broadened peak was observed for a diffuse tumor pattern, and an inflammatory septal case provided two TOI peaks that correlated qualitatively with MRI enhancement. These results provide qualitative confirmation of the common signal origin and complementary information content that can be achieved by combining optical and MR imaging for breast cancer detection and clinical management.

Abstract P4-02-04: Tissue oxyhemoglobin dynamics measured with functional optical imaging immediately after starting chemotherapy correlates with markers of cellular proliferation and inflammation in a rat breast tumor model

We have reported that a transient increase of oxyhemoglobin level measured 24 hours after the start of neoadjuvant chemotherapy using noninvasive Diffuse Optical Spectroscopic Imaging (DOSI) may be useful in discriminating nonresponding from reponding breast cancer patients (PNAS. 2011 Aug 30;108(35):14626–31). To elucidate the underlying biological mechanism, we compared optical measured hemoglobin levels to tissue biomarkers in a rat tumor model.

Method: An orthotopic mammary tumor model using Fischer 344 rats and MAT3B cells was used for this experiment. 16 mg of cyclophosphamide was administered (i.p.) in 15 rats after tumors had grown to a significant size. A wide-field functional imaging device that utilizes structured near-infrared light was used to measure superficial absolute concentrations of oxyhemoglobin (ctO2Hb) and deoxyhemoglobin (ctHHb) of the tumors. Rats were imaged and sacrificed (two per timepoint) at each of the following timepoints: baseline, 2, 6, 12, 24, 48, 96 hours, and day 8 following the injection. Resected tumors were sectioned after paraffin-embedding and representative slides were used for immunohistochemistry. Cellular markers of proliferation (measured by Ki67), apoptosis (Caspase3), NK cells (ANK61), and macrophages (MAC387) were counted in each slide using Image J software.

Result: Average tumors baseline values of ctO2Hb and ctHHb were 81.4 µM (±9.2 SD) and 22.4 µM (±4.1 SD) respectively. In most rats, both levels gradually increased from baseline to 24 hours after the injection and reached a maximum at 48 hours and then declined until Day 8. At 24 hours, ctO2Hb was significantly higher than baseline [96.8 µM (±8.8 SD) vs. 81.4µM (±9.2 SD), p = 0.003 using Student's t-test]. This trend was mimicked in the tissue markers of cellular proliferation and apoptosis, which peaked at 24 through 48 hours and then dropped. The average NK cell count was also found to rise consistently through the course of monitoring and reached the highest at day 8, while macrophage counts reached a peak at 48 hours and then declined. The differences between baseline and 24 hours for these were statistically significant: Ki67 [294 (±107 SD) vs. 115 (±68 SD), p = 0.0002], Caspase3 [2916 (±1383 SD) vs. 136 (±150 SD), p &lt; 0.0001], NK cells [635 (±329 SD) vs. 159 (±110 SD), p = 0.0001], and macrophage markers [281 (±260 SD) vs. 39 (±31 SD), p = 0.01].

Baseline tumor oxygen saturation correlates with a pathologic complete response in breast cancer patients undergoing neoadjuvant chemotherapy

Tissue hemoglobin oxygen saturation (i.e., oxygenation) is a functional imaging endpoint that can reveal variations in tissue hypoxia, which may be predictive of pathologic response in subjects undergoing neoadjuvant chemotherapy. In this study, we used diffuse optical spectroscopic imaging (DOSI) to measure concentrations of oxyhemoglobin (ctO(2)Hb), deoxy-hemoglobin (ctHHb), total Hb (ctTHb = ctO(2)Hb + ctHHb), and oxygen saturation (stO(2) = ctO(2)Hb/ctTHb) in tumor and contralateral normal tissue from 41 patients with locally advanced primary breast cancer. Measurements were acquired before the start of neoadjuvant chemotherapy. Optically derived parameters were analyzed separately and in combination with clinical biomarkers to evaluate correlations with pathologic response. Discriminant analysis was conducted to determine the ability of optical and clinical biomarkers to classify subjects into response groups. Twelve (28.6%) of 42 tumors achieved pathologic complete response (pCR) and 30 (71.4%) were non-pCR. Tumor measurements in pCR subjects had higher stO(2) levels (median 77.8%) than those in non-pCR individuals (median 72.3%, P = 0.01). There were no significant differences in baseline ctO(2)Hb, ctHHb, and ctTHb between response groups. An optimal tumor oxygenation threshold of stO(2) = 76.7% was determined for pCR versus non-pCR (sensitivity = 75.0%, specificity = 73.3%). Multivariate discriminant analysis combining estrogen receptor staining and stO(2) further improved the classification of pCR versus non-pCR (sensitivity = 100%, specificity = 85.7%). These results show that elevated baseline tumor stO(2) are correlated with a pCR. Noninvasive DOSI scans combined with histopathology subtyping may aid in stratification of individual patients with breast cancer before neoadjuvant chemotherapy.

OT2-05-02: ACRIN 6691 Monitoring and Predicting Breast Cancer Neoadjuvant Chemotherapy Response Using Diffuse Optical Spectroscopic Imaging (DOSI)

Background

Imaging technologies monitoring and predicting breast cancer response to neoadjuvant chemotherapy (NAC) are of increasing interest. The utility of conventional imaging approaches varies and identifies the need for alternate functional imaging strategies. The use of model-based photon migration methods to quantitatively separate light absorption from scattering in multiply-scattering tissues is a type of near-infrared spectroscopy (NIRS) broadly referred to as diffuse optical spectroscopy (DOS) [Bevilacqua, et al. Applied Optics, 2000; Jakubowski, et al., J of Applied Optics, 2009]. DOSI is a promising experimental technology that allows patients undergoing NAC to be followed with a “no significant risk” device meeting Food and Drug Administration criteria for exempt status. The current design is a mobile device which offers increased accessibility and is relatively simple to perform and interpret, as compared to mammography, magnetic resonance imaging, and positron emission tomography. Due to its size and portability, DOSI is a low barrier-to-access technology, creating new opportunities for patients to receive personalized treatment and for physicians to gain new insight into response mechanisms. The long-term goal is to provide oncologists with a relatively simple, risk-free bedside tool that can be used to help inform medical decisions on chemotherapy regimen, duration, and timing of surgery, thereby maximizing therapeutic response and minimizing unnecessary toxicity.

Trial design: In this phase I/II prospective single arm study, patients will receive SOC NAC at five (5) NCI Network for Translational Research in Optical Imaging (NTROI) clinical sites with identical DOSI instruments and procedures. Patients will receive four DOSI exams: at baseline before chemotherapy, at early therapy 5–10 days after NAC initiation, at mid therapy, and at post therapy prior to surgery. The protocol will evaluate a harmonized DOSI technology platform that has been standardized for NAC monitoring.

Eligibility: Women who have been diagnosed with breast cancer, have had confirmation by pre-treatment biopsy, and are scheduled to receive NAC followed by surgery are eligible for this trial.

Specific aims: The primary aim of this clinical trial is to determine whether the baseline to mid-therapy changes in the DOSI measurement of the quantitative tumor tissue optical index can predict final pathologic complete response in patients with breast cancer undergoing NAC. The secondary aims investigate the correlation between additional DOSI quantitative measurements of tumor biochemical composition obtained at other timepoints, the full range of pathologic response (i.e. complete, partial, and non-response), and any corresponding imaging measurements.

Statistical methods: Logistic regression models will be used to study the relationships between pathological complete response and percent change in tissue optical index tumor to normal ratio at different imaging time points.

Study size: A total of sixty (60) patients will be enrolled in this imaging study. Currently, one patient has accrued.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr OT2-05-02.

Breast cancer spatial heterogeneity in near-infrared spectra and the prediction of neoadjuvant chemotherapy response

We describe an algorithm to calculate an index that characterizes spatial differences in broadband near-infrared [(NIR), 650-1000 nm] absorption spectra of tumor-containing breast tissue. Patient-specific tumor spatial heterogeneities are visualized through a heterogeneity spectrum function (HS). HS is a biomarker that can be attributed to different molecular distributions within the tumor. To classify lesion heterogeneities, we built a heterogeneity index (HI) derived from the HS by weighing the HS in specific NIR absorption bands. It is shown that neoadjuvant chemotherapy (NAC) response is potentially related to the tumor heterogeneity. Therefore, we correlate the heterogeneity index obtained prior to treatment with the final response to NAC. From a pilot study of 15 cancer patients treated with NAC, pathological complete responders (pCR) were separated from non-pCR according to their HI (-44 ± 12 and 43 ± 17, p = 3 × 10(-8), respectively). We conclude that the HS function is a biomarker that can be used to visualize spatial heterogeneities in lesions, and the baseline HI prior to therapy correlates with chemotherapy pathological response.

Consensus recommendations for advancing breast cancer: risk identification and screening in ethnically diverse younger women

A need exists for a breast cancer risk identification paradigm that utilizes relevant demographic, clinical, and other readily obtainable patient-specific data in order to provide individualized cancer risk assessment, direct screening efforts, and detect breast cancer at an early disease stage in historically underserved populations, such as younger women (under age 40) and minority populations, who represent a disproportionate number of military beneficiaries. Recognizing this unique need for military beneficiaries, a consensus panel was convened by the USA TATRC to review available evidence for individualized breast cancer risk assessment and screening in young (< 40), ethnically diverse women with an overall goal of improving care for military beneficiaries. In the process of review and discussion, it was determined to publish our findings as the panel believes that our recommendations have the potential to reduce health disparities in risk assessment, health promotion, disease prevention, and early cancer detection within and in other underserved populations outside of the military. This paper aims to provide clinicians with an overview of the clinical factors, evidence and recommendations that are being used to advance risk assessment and screening for breast cancer in the military.

Near-infrared imaging of the sinuses: preliminary evaluation of a new technology for diagnosing maxillary sinusitis

Diagnosing sinusitis remains a challenge for primary care physicians. There is a need for a simple, office-based technique to aid in the diagnosis of sinusitis without the cost and radiation risk of conventional radiologic imaging. We designed a low-cost near-infrared (NIR) device to transilluminate the maxillary sinuses. The use of NIR light allows for greater interrogation of deep-tissue structures as compared to visible light. NIR imaging of 21 patients was performed and compared with computed tomography (CT) scans. Individual maxillary sinuses were scored on a scale from 0 to 2 based on their degree of aeration present on CT and similarly based on the NIR signal penetration into the maxilla on NIR images. Our results showed that air-filled and fluid/tissue-filled spaces can be reasonably distinguished by their differing NIR signal penetration patterns, with average NIR imaging scores for fluid-filled maxillary sinuses (0.93+/-0.78, n=29) significantly lower than those for normal maxillary sinuses (1.62+/-0.57, n=13) (p=0.003). NIR imaging of the sinuses is a simple, safe, and cost-effective modality that can potentially aid in the diagnosis of sinusitis. Long-term, significant device refinement and large clinical trials will be needed to determine the diagnostic accuracy of this technique.

Effect of contact force on breast tissue optical property measurements using a broadband diffuse optical spectroscopy handheld probe

We investigated the effects of operator-applied force on diffuse optical spectroscopy (DOS) by integrating a force transducer into the handheld probe. Over the typical range of contact forces measured in the breasts of eight patients, absorption and reduced scattering coefficients (650 to 1000 nm) variance was 3.1 +/- 1.0% and 1.0 +/- 0.4%. For trained operators, we observed <5% variation in hemoglobin and <2% variation in water and lipids. Contact force is not a significant source of variation, most likely because of a relatively wide probe surface area and the stability of the DOS method for calculating tissue optical properties.

Non-invasive detection and monitoring of tumor pathological grade during neoadjuvant chemotherapy by measuring tissue water state using diffuse optical spectroscopic imaging

Abstract #803

Background: Changes of tissue water state are related to physiological and pathological properties of breast tissues. For instance, MRI has measured water mobility in order to monitor local micro-structural changes in breast cancer tissues during chemotherapy. Diffuse Optical Spectroscopic Imaging (DOSI) measures water molecular vibrational states associated with macro-molecular complexes in tissues such as proteins. For DOSI measurements, breast tumors are line-scanned and spectral information on each point is spatially mapped to generate an image.&#x2028; Subjects & Methods: DOSI was employed to measure 15 infiltrating ductal carcinoma (IDC) patients before treatment. Five IDC and one infiltrating lobular carcinoma (ILC) tumors were also measured along the course of neoadjuvant chemotherapy. Patient responses were determined from standard pathology: complete (N=2), partial (N=2) and non-responders (N=2). The spectral features of tissue water absorption from 935 nm to 998nm were compared to those of a pure water spectrum measured at body temperature in order to acquire the Bound Water Index (BWI: the residual between tissue and pure water spectra). In spectroscopic images, the Cancer BWI Ratio (CBR) was calculated by counting the fraction of the BWI less than 20% of the BWI range of pre-chemo (baseline) measurement in a primary cancer. Lower BWI means the cancer has more free water. The CBR communicates the changes of tissue water state along the course of therapies in the similar way to Signal Enhanced Ratio (SER) used in contrast enhanced MRI.&#x2028; Results: In our in vivo clinical studies with 15 IDC tumors, a high inverse correlation between BWI and Nottingham Bloom-Richardson histopathological score (R=-0.87) was found. In the neoadjuvant chemotherapy studies, BWI increased during the entire course of the therapy in complete responders while it fluctuated then stayed close to baseline values in partial responders. In non-responders, the change amount of BWI was very small and the BWI values decreased below baseline values. Quantitatively, for complete responders, BWI increased (more bound water) 59% from baseline and CBR decreased (less pixels for cancer) 26.9% and the pixels presenting cancer property disappeared. In partial responders, BWI increased 4.7% and CBR decreased 8.2% whereas, in non-responders, BWI decreased 16.4% and CBR increased 28.7%.&#x2028; Discussion: The high correlation between BWI and histopathological score communicates that water state measurements using DOSI report on disease grades of breast cancer non-invasively. In the neoadjuvant chemotherapy studies, bigger tissue water state changes have been measured in complete than partial responders and the changes to the opposite direction in non-responders. There results demonstrate a potential of tissue water state with DOSI as a non-invasive pathological grade monitor during chemotherapy, which can be used as a substitute for a biopsy at any point during the treatment cycle.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 803.

Diffuse optical spectroscopy measurements of healing in breast tissue after core biopsy: case study

Diffuse optical spectroscopy (DOS) has been used to monitor and predict the effects of neoadjuvant (i.e., presurgical) chemotherapy in breast cancer patients in several pilot studies. Because patients with suspected breast cancers undergo biopsy prior to treatment, it is important to understand how biopsy trauma influences DOS measurements in the breast. The goal of this study was to measure the effects of a standard core breast biopsy on DOS measurements of tissue deoxyhemoglobin, hemoglobin, water, and bulk lipid concentrations. We serially monitored postbiopsy effects in the breast tissue in a single subject (31-year-old premenopausal female) with a 37x18x20 mm fibroadenoma. A baseline measurement and eight weekly postbiopsy measurements were taken with a handheld DOS imaging instrument. Our instrument used frequency domain photon migration combined with broadband steady-state spectroscopy to characterize tissues via quantitative measurements of tissue absorption and reduced scattering coefficients from 650 to 1000 nm. The concentrations of significant near-infrared (NIR) absorbers were mapped within a 50 cm(2) area over the biopsied region. A 2-D image of a contrast function called the tissue optical index (TOI=deoxyhemoglobinxwaterbulk lipid) was generated and revealed that a minimum of 14 days postbiopsy was required to return TOI levels in the biopsied area to their prebiopsy levels. Changes in the TOI images of the fibroadenoma also reflected the progression of the patient's menstrual cycle. DOS could therefore be useful in evaluating both wound-healing response and the effects of hormone and hormonal therapies in vivo.

Design and testing of a miniature broadband frequency domain photon migration instrument

A board-level broadband frequency domain photon migration (mini-FDPM) instrument has been constructed to replace a conventional network-analyzer-based FDPM instrument. The mini-FDPM instrument with four wavelengths (681, 783, 823, and 850 nm), matches conventional FDPM instrument in performance (-88 dBm noise level, 100 dB dynamic range) and bandwidth (1 GHz), and recovers the same optical properties within about 6% in absorption and 4% in reduced scattering for liquid phantoms covering a wide range of relevant optical properties. Compared to the conventional FDPM instrument, the mini-FDPM instrument is more than 5x faster (approximately 200 ms per 401 modulation frequencies) and several orders of magnitude less in size and cost. Standard fiber-optic-based probes can be used with the mini-FDPM instrument, which increases applications in a number of clinically relevant measurement scenarios. By drastically reducing size and cost, FDPM miniaturization lowers barriers to access and will help promote FDPM in clinical research problems. The mini-FDPM instrument forms the core of a modular broadband diffuse optical spectroscopy instrument that can be used for a variety of clinical problems in imaging and functional monitoring (i.e., breast/skin cancer, brain activation, and exercise physiology).

Diffuse optical monitoring of blood flow and oxygenation in human breast cancer during early stages of neoadjuvant chemotherapy

We combine diffuse optical spectroscopy (DOS) and diffuse correlation spectroscopy (DCS) to noninvasively monitor early hemodynamic response to neoadjuvant chemotherapy in a breast cancer patient. The potential for early treatment monitoring is demonstrated. Within the first week of treatment (day 7) DOS revealed significant changes in tumor/normal contrast compared to pretreatment (day 0) tissue concentrations of deoxyhemoglobin (rctHHbT/N=69+/-21%), oxyhemoglobin (rctO2HbT/N=73+/-25%), total hemoglobin (rctTHbT/N=72+/-17%), and lipid concentration (rctLipidT/N=116+/-13%). Similarly, DCS found significant changes in tumor/normal blood flow contrast (rBFT/N=75+/-7% on day 7 with respect to day 0). Our observations suggest the combination of DCS and DOS enhances treatment monitoring compared to either technique alone. The hybrid approach also enables construction of indices reflecting tissue metabolic rate of oxygen, which may provide new insights about therapy mechanisms.

Method for recovering quantitative broadband diffuse optical spectra from layered media

We report the recovery of broadband (650-1000 nm) diffuse optical absorption and reduced scattering spectra stratified by layer in a two-layer phantom. The broadband optical properties of the phantom featured top and bottom layers designed to simulate adipose and muscle, respectively. The absolute value and dynamic variation of chromophore concentrations in both layers (top layer thickness greater than 5 mm) were calculated with an average 10% error and 3% error, respectively. In addition to spectra, the algorithm recovers the top layer thickness up to 12 mm within 10% error. It is insensitive to initial guesses of both layers' optical properties as long as the layer thickness initial guess is within +/-2 mm.

Intrinsic tumor biomarkers revealed by novel double-differential spectroscopic analysis of near-infrared spectra

We develop a double-differential spectroscopic analysis method for broadband near-infrared (NIR, 650 to 1000 nm) absorption spectra. Application of this method to spectra of tumor-containing breast tissue reveals specific cancer biomarkers. In this method, patient-specific variations in molecular composition are removed by using the normal tissue as an internal control. The effects of concentration differences of the four major tissue absorbers (oxyhemoglobin, deoxyhemoglobin, water, and bulk lipid) between the tumor and normal tissue are accounted for to reveal small spectral components unique to cancer. From a pilot study of 15 cancer patients, we find these spectral components to be characterized by specific NIR absorption bands. Based on the spectral regions of absorption at about 760, 930, and 980 nm, we identify these biomarkers with changes in state or addition of lipid and/or water. To quantify spectral variation in the absorption bands, we construct the specific tumor component (STC) index. The STC index identifies regions of the breast with tumors.

Predicting response to breast cancer neoadjuvant chemotherapy using diffuse optical spectroscopy

Diffuse optical spectroscopy (DOS) and imaging are emerging diagnostic techniques that quantitatively measure the concentration of deoxy-hemoglobin (ctHHb), oxy-hemoglobin (ctO(2)Hb), water (ctH(2)O), 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(2)Hb, ctH(2)O, and spectral scattering slope, and decreases in bulk lipids, relative to normal breast tissue. Tumor concentrations of ctHHb, ctO(2)Hb, and ctH(2)O 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(2)O changes classified responders vs. nonresponders with 100% sensitivity and specificity. In addition, the pretreatment tumor-to-normal ctO(2)Hb 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.

In vivo absorption, scattering, and physiologic properties of 58 malignant breast tumors determined by broadband diffuse optical spectroscopy

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.

Imaging in breast cancer: diffuse optics in breast cancer: detecting tumors in pre-menopausal women and monitoring neoadjuvant chemotherapy

Diffuse optical spectroscopy (DOS) and diffuse optical imaging (DOI) are non-invasive diagnostic techniques that employ near-infrared (NIR) light to quantitatively characterize the optical properties of centimeter-thick, multiple-scattering tissues. Although NIR was first applied to breast diaphanography more than 70 years ago, quantitative optical methods employing time- or frequency-domain 'photon migration' technologies have only recently been used for breast imaging. Because their performance is not limited by mammographic density, optical methods can provide new insight regarding tissue functional changes associated with the appearance, progression, and treatment of breast cancer, particularly for younger women and high-risk subjects who may not benefit from conventional imaging methods. This paper reviews the principles of diffuse optics and describes the development of broadband DOS for quantitatively measuring the optical and physiological properties of thick tissues. Clinical results are shown highlighting the sensitivity of diffuse optics to malignant breast tumors in 12 pre-menopausal subjects ranging in age from 30 to 39 years and a patient undergoing neoadjuvant chemotherapy for locally advanced breast cancer. Significant contrast was observed between normal and tumor regions of tissue for deoxy-hemoglobin (p = 0.005), oxy-hemoglobin (p = 0.002), water (p = 0.014), and lipids (p = 0.0003). Tissue hemoglobin saturation was not found to be a reliable parameter for distinguishing between tumor and normal tissues. Optical data were converted into a tissue optical index that decreased 50% within 1 week in response to neoadjuvant chemotherapy. These results suggest a potential role for diffuse optics as a bedside monitoring tool that could aid the development of new strategies for individualized patient care.

Combined diffuse optical spectroscopy and contrast-enhanced magnetic resonance imaging for monitoring breast cancer neoadjuvant chemotherapy: a case study

Monitoring tumor response to therapy can enable assessment of treatment efficacy, maximizing patient outcome and survival. We employ a noninvasive, handheld laser breast scanner (LBS) based on broadband diffuse optical spectroscopy (DOS) in conjunction with contrast-enhanced magnetic resonance imaging (cMRI) to assess tumor response to presurgical neoadjuvant chemotherapy. DOS and cMRI scans are performed after the first and fourth cycles of a doxorubicin/cyclophosphamide regimen in a patient with invasive ductal carcinoma. DOS measurements are used to quantify bulk tissue optical and physiological parameters, which are mapped to T2- and T1-weighted cMRI images. Initial DOS measurements show high tumor/normal contrast in total hemoglobin concentration (THC, 56+/-7 versus 27+/-4 microM) and water fraction (81.4+/-1% versus 24+/-3%) colocalized with regions of strongly enhancing T2-weighted and cMRI signals. After the fourth cycle of chemotherapy, we observe decreases in peak MRI contrast-enhancement values (37.6%) and apparent lesion volume (21.9 versus 13.7 cm3), which corresponds to physiological changes measured by DOS, including a 20 to 25% reduction in the spatial extent of the tumor and a 38.7% drop in mean total hemoglobin content (THC, 41.6 versus 23.4 microM). These data provide in vivo validation of the accuracy of broadband DOS and the sensitivity of optical methods to changes in tumor physiology.

Noninvasive monitoring of red blood cell transfusion in very low birthweight infants using diffuse optical spectroscopy

Red blood cell (RBC) transfusion guidelines are designed to maintain adequate tissue oxygenation by increasing blood oxygen-carrying capacity. However, since tissue oxygenation is not measured, RBC transfusion guidelines are mostly subjective. Clinical evidence of oxygen transport/consumption mismatches in infants is often unclear and confounded by multiple factors. Invasive hemoglobin measurements can contribute further to anemia if performed too frequently. Diffuse optical spectroscopy (DOS) is a noninvasive quantitative method to measure the tissue oxy, deoxy, and total hemoglobin concentrations (ctO2Hb, ctHb, ctTHb), as well as mixed arterial-venous tissue hemoglobin saturation (stO2). Our objective is to determine if DOS can assess changes in tissue oxygenation in very low birth weight (VLBW) infants undergoing RBC transfusions. DOS measurements of ctO2Hb and ctHb are performed on 10 VLBW infants before and within 24 h after RBC transfusion. Seven nontransfused infants are studied to evaluate hemodynamic variations independent of RBC transfusion. Tissue near-infrared absorption and scattering values are measured using a four-wavelength (690, 750, 810, and 830 nm) frequency-domain tissue oximeter (OxiplexTS, ISS, Champaign, Illinois). In transfused subjects, DOS demonstrates significant increases in ctO2Hb (48+/-13 versus 74+/-20 microM, p<0.002), ctTHb (87+/-17 versus 107+/-24 microM, p=0.004), and stO2 (54+/-8 versus 68+/-6%, p<0.004) post-transfusion. DOS measurements correlate with mean hemoglobin increases for all infants (r=0.83, p<0.0001). No significant DOS changes occurred in the nontransfused group. Calculations of the differential path length for these transfused subjects show high variability (approximately 20%). DOS may serve as a noninvasive bedside tool to assess tissue oxygenation in infants and provide a functionally based transfusion trigger.

Non-Invasive Hemodynamic Monitoring using near Infrared Frequency Domain Photon Migration in Rabbit Hemorrhagic Shock Model

Background

Currently, there are no reliable, accurate, non-invasive methods of assessing hemodynamic parameters, tissue hemoglobin, and 0, content for physiologic monitoring. Recent advances in the field of optical diagnostics have lead to new imaging modalities capable of evaluating regional in-vivo tissue composition using its optical properties. The advantage of Frequency Domain Photon Migration (FDPM) over previously studied bulk NIR spectroscopy is that it allows for quantitative measurements of both light absorption and scattering in tissues. Devices based on FDPM principles have the potential to accurately and non-invasively monitor hemodynamics and other parameters in patients with shock and physiologic disturbances.

Purpose

This study investigated FDPM methods for monitoring shock and the response to treatment with volume expansion and pressors in a hemorrhagic rabbit model. The sensitivity of this monitoring method for discriminating changes in hemodynamic parameters compared to traditional invasive monitoring devises, as well as the ability to accurately measure hemoglobin and tissue 0, was assessed.

Methods

New Zealand White (NZW) rabbits (n=25) were used in this study. Aprototype FDPM device developed in our laboratory was used. Aprobe was placed on the inner thigh of the rabbits. The rabbits underwent concurrent traditional invasive monitoring including cardiac output (CO), pulmonary arterial pressure (PA), systemic blood pressure via arterial line, hemoglobin, and arterial and venous blood gases. Hemorrhage was performed via a syringe either in stages or in a single step. After measurements were obtained the animals were resuscitated with vasopressors, or with crystalloid solution.

Results

The FPDM measurements of tissue hemoglobin (Hb), Oxyhemoglobin (HbO,), water content and tissue 0, saturation were obtained. The tissue Hb (r=0.7) and oxygen content (r=0.6) closely correlated with the measurements made with invasive methods. The FDPM measurements also correlated with CO. Conclusion: Broad-bandwidth FDPM may be a reliable, accurate and non-invasive means of monitoring patients with hemorrhagic shock and their response to treatment. FDPM may potentially be adapted for use in early shock recognition for triage or in settings where aggressive invasive monitoring is problematic.

Noninvasive functional optical spectroscopy of human breast tissue

Near infrared diffuse optical spectroscopy and diffuse optical imaging are promising methods that eventually may enhance or replace existing technologies for breast cancer screening and diagnosis. These techniques are based on highly sensitive, quantitative measurements of optical and functional contrast between healthy and diseased tissue. In this study, we examine whether changes in breast physiology caused by exogenous hormones, aging, and fluctuations during the menstrual cycle result in significant alterations in breast tissue optical contrast. A noninvasive quantitative diffuse optical spectroscopy technique, frequency-domain photon migration, was used. Measurements were performed on 14 volunteer subjects by using a hand-held probe. Intrinsic tissue absorption and reduced scattering parameters were calculated from frequency-domain photon migration data. Wavelength-dependent absorption (at 674, 803, 849, and 956 nm) was used to determine tissue concentration of oxyhemoglobin, deoxyhemoglobin, total hemoglobin, tissue hemoglobin oxygen saturation, and bulk water content. Results show significant and dramatic differences in optical properties between menopausal states. Average premenopausal intrinsic tissue absorption and reduced scattering values at each wavelength are 2.5- to 3-fold higher and 16-28 % greater, respectively, than absorption and scattering for postmenopausal subjects. Absorption and scattering properties for women using hormone replacement therapy are intermediate between premenopausal and postmenopausal populations. Physiological properties show differences in mean total hemoglobin (7.0 microM, 11.8 microM, and 19.2 microM) and water concentration relative to pure water (10.9 %, 15.3 %, and 27.3 %) for postmenopausal, hormone replacement therapy, and premenopausal subjects, respectively. Because of their unique, quantitative information content, diffuse optical methods may play an important role in breast diagnostics and improving our understanding of breast disease.

Non-invasive in vivo characterization of breast tumors using photon migration spectroscopy

Frequency-domain photon migration (FDPM) is a non-invasive optical technique that utilizes intensity-modulated, near-infrared (NIR) light to quantitatively measure optical properties in thick tissues. Optical properties (absorption, mu(a), and scattering, mu(s)', parameters) derived from FDPM measurements can be used to construct low-resolution (0.5 to 1 cm) functional images of tissue hemoglobin (total, oxy-, and deoxy-forms), oxygen saturation, blood volume fraction, water content, fat content and cellular structure. Unlike conventional NIR transillumination, FDPM enables quantitative analysis of tissue absorption and scattering parameters in a single non-invasive measurement. The unique functional information provided by FDPM makes it well-suited to characterizing tumors in thick tissues. In order to test the sensitivity of FDPM for cancer diagnosis, we have initiated clinical studies to quantitatively determine normal and malignant breast tissue optical and physiological properties in human subjects. Measurements are performed using a non-invasive, multi-wavelength, diode-laser FDPM device optimized for clinical studies. Results show that ductal carcinomas (invasive and in situ) and benign fibroadenomas exhibit 1.25 to 3-fold higher absorption than normal breast tissue. Within this group, absorption is greatest for measurements obtained from sites of invasive cancer. Optical scattering is approximately 20% greater in pre-menopausal versus post-menopausal subjects due to differences in gland/cell proliferation and collagen/fat content. Spatial variations in tissue scattering reveal the loss of differentiation associated with breast disease progression. Overall, the metabolic demands of hormonal stimulation and tumor growth are detectable using photon migration techniques. Measurements provide quantitative optical property values that reflect changes in tissue perfusion, oxygen consumption, and cell/matrix development.