Breast cancer detection by mapping hemoglobin concentration and oxygen saturation

Evaluation of Tumor Development Using Hemoglobin Saturation Profile on Rodent Dorsal Window Chamber

Tumor development can be indirectly evaluated using features of the tumor microenvironment (TME), such as hemoglobin saturation (HbSat), blood vessel dilation, and formation of new vessels. High values of HbSat and other features of the TME could indicate high metabolic activity and could precede the formation of angiogenic tumors; therefore, changes in HbSat profile can be used as a biomarker for tumor progression. One methodology to evaluate HbSat profile over time, and correlate it with tumor development in vivo in a preclinical model, is through a dorsal skin-fold window chamber. In this chapter, we provide a detailed description of this methodology to evaluate hemoglobin saturation profile and to predict tumor development. We will cover the surgical preparation of the mouse, the installation/maintenance of the dorsal window chamber, and the imaging processing and evaluation to the HbSat profile to predict new development of new tumor areas over time. We included, in this chapter, step by step examples of the imaging processing method to obtain pixel level HbSat values from raw pixels data, the computational method to determine the HbSat profile, and the steps for the classification of the areas into tumor and no-tumor.

The use of tissue oxygen measurements compared to indocyanine green imaging for the assessment of intraoperative tissue viability of human bowel

BACKGROUND

Adequate tissue oxygenation and perfusion remain fundamental to safe bowel resection surgery. Near infrared (NIR) imaging using indocyanine green has proven itself superior to clinical evaluation alone in assessing bowel perfusion, but requires expensive equipment not readily available in many centers.

METHODS

We studied the IntraOx device (Vioptix Inc, Newark, CA USA), a handheld, tissue oxygen saturation assessment tool, to assess whether tissue bed oxygen saturation (StO2) is comparable to NIR assessment of bowel viability. Patients undergoing elective colon resection for benign and malignant disease were included. After choosing a clinical margin (CM) and dividing the mesentery, StO2 was measured at 5-cm intervals along the colon. A tissue oxygen saturation margin (TOM) was assigned where StO2 dropped off by at least 10 percentage points. NIR perfusion was then assessed to determine NIR margin (NIRM). Intraoperative and postoperative data were collected.

RESULTS

32 consecutive patients undergoing colectomies were analyzed. IntraOx sensitivity was 90.6%, specificity was 94.3%. The mean StO2 difference across the NIRM was 23.1%. In all but one case, the TOM matched the NIRM. In 3 cases, the TOM and NIRM concurred, but were a mean of 3.3 cm proximal to the CM and altered the surgical plan. At 4-week follow-up, no significant complications were reported.

CONCLUSIONS

The IntraOx device consistently identified a margin of significant saturation "drop-off" which correlated with the findings on NIR perfusion and clinical assessment. These early data indicate that StO2 measurement may be equivalent to NIR assessment of bowel perfusion. In addition, the IntraOx device may be a more cost-effective solution for surgeons looking for adjunctive evaluation of bowel viability. More study is warranted in a larger group of patients to confirm these preliminary findings and to judge the impact of StO2 assessment on reducing anastomotic leaks.

Quantitative analysis of breast tumours aided by three-dimensional photoacoustic/ultrasound functional imaging

In this pilot study, we explored a quantitative method to analyse characteristics of breast tumours using 3D volumetric data obtained from a three-dimensional (3D) photoacoustic/ultrasound (PA/US) functional imaging system. Imaging results from 24 Asian patients with maximum tumour diameters less than 2 cm, including 8 benign tumours, 16 T1 stage invasive breast cancers (IBCs), and 22 normal breasts, were analysed. We found that the volumetric mean oxygenation saturation (SO₂) in tumour regions of T1 stage IBCs was 7.7% lower than that of benign tumours (P = 0.016) and 3.9% lower than that of healthy breasts (P = 0.010). The volumetric mean SO₂ in tumour surrounding regions of T1 stage IBCs was 4.9% lower than that of benign tumours (P = 0.009). For differentiating T1 stage IBCs and benign tumours, with a cut-off SO₂ value of 78.2% inside tumours, we obtained a sensitivity of 100%, a specificity of 62.5%, and an AUC of 0.81; with a cut-off SO₂ value of 77.9% in regions surrounding tumours, we obtained a sensitivity of 100%, a specificity of 75% and an AUC of 0.84. Our preliminary results demonstrate that 3D PA/US functional imaging has the potential to provide valuable quantitative physiological information that may be useful for the detection and evaluation of breast tumours.

Oxygen-Sensing Paint-On Bandage: Calibration of a Novel Approach in Tissue Perfusion Assessment

BACKGROUND

Knowledge of tissue oxygenation status is fundamental in the prevention of postoperative flap failure. Recently, the authors introduced a novel oxygen-sensing paint-on bandage that incorporated an oxygen-sensing porphyrin with a commercially available liquid bandage matrix. In this study, the authors extend validation of their oxygen-sensing bandage by comparing it to the use of near-infrared tissue oximetry in addition to Clark electrode measurements.

METHODS

The oxygen-sensing paint-on bandage was applied to the left hind limb in a rodent model. Simultaneously, a near-infrared imaging device and Clark electrode were attached to the right and left hind limbs, respectively. Tissue oxygenation was measured under normal, ischemic (aortic ligation), and reperfused conditions.

RESULTS

On average, the oxygen-sensing paint-on bandage measured a decrease in transdermal oxygenation from 85.2 mmHg to 64.1 mmHg upon aortic ligation. The oxygen-sensing dye restored at 81.2 mmHg after unclamping. Responses in both control groups demonstrated a similar trend. Physiologic changes from normal to ischemic and reperfused conditions were statistically significantly different in all three techniques (p < 0.001).

CONCLUSIONS

The authors' newly developed oxygen-sensing paint-on bandage exhibits a comparable trend in oxygenation recordings in a rat model similar to conventional oxygenation assessment techniques. This technique could potentially prove to be a valuable tool in the routine clinical management of flaps following free tissue transfer. Incorporating oxygen-sensing capabilities into a simple wound dressing material has the added benefit of providing both wound protection and constant wound oxygenation assessment.

Wavelength-modulated differential photoacoustic radar imager (WM-DPARI): accurate monitoring of absolute hemoglobin oxygen saturation

Accurate monitoring of blood oxy-saturation level (SO2 ) in human breast tissues is clinically important for predicting and evaluating possible tumor growth at the site. In this work, four different non-invasive frequency-domain photoacoustic (PA) imaging modalities were compared for their absolute SO2 characterization capability using an in-vitro sheep blood circulation system. Among different PA modes, a new WM-DPAR imaging modality could estimate the SO2 with great accuracy when compared to a commercial blood gas analyzer. The developed WM-DPARI theory was further validated by constructing SO2 tomographic images of a blood-containing plastisol phantom.

Near-infrared spectroscopy for medical applications: Current status and future perspectives

The near-infrared radiation (NIR) window, also known as the "optical window" or "therapeutic window", is the range of wavelengths that has the maximum depth of penetration in tissue. Indeed, because NIR is minimally absorbed by water and hemoglobin, spectra readings can be easily collected from the body surface. Recent reports have shown the potential of NIR spectroscopy in various medical applications, including functional analysis of the brain and other tissues, as well as an analytical tool for diagnosing diseases. The broad applicability of NIR spectroscopy facilitates the diagnosis and therapy of diseases as well as elucidating their pathophysiology. This review introduces recent advances and describes new studies in NIR to demonstrate potential clinical applications of NIR spectroscopy.

Optical imaging for breast cancer prescreening

Breast cancer prescreening is carried out prior to the gold standard screening using X-ray mammography and/or ultrasound. Prescreening is typically carried out using clinical breast examination (CBE) or self-breast examinations (SBEs). Since CBE and SBE have high false-positive rates, there is a need for a low-cost, noninvasive, non-radiative, and portable imaging modality that can be used as a prescreening tool to complement CBE/SBE. This review focuses on the various hand-held optical imaging devices that have been developed and applied toward early-stage breast cancer detection or as a prescreening tool via phantom, in vivo, and breast cancer imaging studies. Apart from the various optical devices developed by different research groups, a wide-field fiber-free near-infrared optical scanner has been developed for transillumination-based breast imaging in our Optical Imaging Laboratory. Preliminary in vivo studies on normal breast tissues, with absorption-contrasted targets placed in the intramammary fold, detected targets as deep as 8.8 cm. Future work involves in vivo imaging studies on breast cancer subjects and comparison with the gold standard X-ray mammography approach.

Estimate of tissue composition in malignant and benign breast lesions by time-domain optical mammography

The optical characterization of malignant and benign breast lesions is presented. Time-resolved transmittance measurements were performed in the 630-1060 nm range by means of a 7-wavelength optical mammograph, providing both imaging and spectroscopy information. A total of 62 lesions were analyzed, including 33 malignant and 29 benign lesions. The characterization of breast lesions was performed applying a perturbation model based on the high-order calculation of the pathlength of photons inside the lesion, which led to the assessment of oxy- and deoxy-hemoglobin, lipids, water and collagen concentrations. Significant variations between tumor and healthy tissue were observed in terms of both absorption properties and constituents concentration. In particular, benign lesions and tumors show a statistically significant discrimination in terms of absorption at several wavelengths and also in terms of oxy-hemoglobin and collagen content.

Near infrared imaging of tissue heterogeneity: probe design and sensitivity analysis

A CW type handheld near infrared tissue oximeter called P-Scan tissue imager was developed for real time imaging of tissue oxygen saturation ([StO2]) and hemoglobin concentration ([Hbt]). The probe consists of eight dual-wavelength light sources (690nm and 830nm) and eight photon detectors forming a 2.5cm X 2.5cm matrix. The local tissue oxygen saturation and hemoglobin concentration was calculated based on optical measurement of absorption coefficients for oxy and deoxy hemoglobin. A superimposition algorithm was developed for direct imaging of local tissue [StO2]/[Hbt] without complex inverse reconstruction. The measurement sensitivity of such a P-Scan device with respect to tumor size, tumor depth, tumor lateral location and tumor optical contrast was studied. First order Born approximation was used to simulate the photon migration in a 2D turbid model with an embedded absorber. The simulation results implied that the P-Scan imager is able to detect the tissue heterogeneity up to 1.5 cm deep with reasonably high sensitivity. Simulation also indicated that among multiple factors that may influence the P-Scan sensitivity, tumor size and tumor depth are dominant factors.^*

Localization and functional parameter reconstruction of suspicious breast lesions by near infrared/ultrasound dual modal imaging

A novel imaging scheme integrating a continuous wave (CW) hand held near infrared tissue imager and a portable ultrasound probe was proposed for evaluation of suspicious breast lesions. A new methodology was developed to reconstruct functional properties of the lesion and the surrounding tissue based on the optical measurement of the diffusive light and the ultrasound measurement of the tumor morphology. The first order Born approximation was used to solve the absorption coefficients for both the tumor tissue and the background tissue assuming that optical properties within each tissue type are uniform. A compression force was applied by the handheld near infrared imager to the breast tissue in order to enhance the optical contrast. The force was monitored by a built-in load cell. 2D projection algorithm was used to find the center of the tumor and to co-register the near infrared image with the ultrasound image. The proposed imaging scheme was tested by a clinical trial where both near infrared and ultrasound data were collected on subjects' breast tissues with embedded suspicious lesions. 3D image algorithm on single patient successfully reconstructed the oxygen saturation and the hemoglobin concentration in both the tumor area and the surrounding tissue. More data collection and analysis are required to confirm this imaging scheme.

Monitoring the response to primary medical therapy for breast cancer using three- dimensional time-resolved optical mammography

Primary medical therapy is used to reduce tumour size prior to surgery in women with locally advanced breast cancer. Optical tomography is a functional imaging technique using near- infrared light to produce three-dimensional breast images of tissue oxygen saturation and haemoglobin concentration. Its advantages include the ability to display quantitative physiological information, and to allow repeated scans without the hazards associated with exposure to ionising radiation. There is a need for a non-invasive functional imaging tool to evaluate response to treatment, so that non-responders can be given the opportunity to change their treatment regimen. Here, we evaluate the use of optical tomography for this purpose. Four women with newly diagnosed breast cancer who were about to undergo primary medical therapy gave informed and voluntary consent to take part in the study. Changes in physiological and optical properties within the tumour were evaluated during the course of neoadjuvant chemotherapy. Optical imaging was performed prior to treatment, after the first cycle of chemotherapy, halfway through, and on completion of chemotherapy. Images of light absorption and scatter at two wavelengths were produced, from which images of total haemoglobin concentration and oxygen saturation were derived. All patients that showed a good or complete response to treatment on MRI showed a corresponding recovery in the haemoglobin concentration images. Changes in mean tumour total haemoglobin concentration could be seen four weeks into treatment. The tumour oxygen saturation was low compared to background in three out of four patients, and also showed a return to baseline over treatment. Optical imaging of the breast is feasible during primary medical therapy and can be used to assess response to treatment over six months.

NIR spectroscopic imaging to map hemoglobin + myoglobin oxygenation, their concentration and optical pathlength across a beating pig heart during surgery

The purpose of this paper is to demonstrate that near-infrared (NIR) spectroscopic imaging can provide spatial distribution (maps) of the absolute concentration of hemoglobin + myoglobin, oxygen saturation parameter and optical pathlength, reporting on the biochemico-physiological status of a beating heart in vivo. The method is based on processing the NIR spectroscopic images employing a first-derivative approach. Blood-pressure-controlled gating compensated the effect of heart motion on the imaging. All the maps are available simultaneously and noninvasively at a spatial resolution in the submillimeter range and can be obtained in a couple of minutes. The equipment has no mechanical contact with the tissue, thereby leaving the heart unaffected during the measurement.

Near-infrared tissue oximetry and digital image analysis: quantification of renal ischaemia in real time during partial nephrectomy

OBJECTIVE

To determine the feasibility of using near-infrared tissue oximetry (TO) and digital image analysis for assessing renal function and to quantify local renal ischaemia in a porcine model.

MATERIALS AND METHODS

Tissue oximetry was performed and red/blue (R/B) colour ratios were determined on renal units of Yorkshire swine. Interval measurements were taken before clamping the renal hilum, during warm ischaemia, and after unclamping using a ViOptix T.Ox™ Tissue Oximeter and Matlab(®) digital image analysis. Matlab software analysed images from the laparoscopic camera and determined an R/B ratio to track renal ischaemia. The tissue oximeter used direct infrared light and was placed adjacent to the kidney parenchymal surface. The data were divided into preclamp, clamp and post-clamp, and compared between methodologies.

RESULTS

The R/B ratio showed a higher rate of change compared with TO during clamp time in both the 15-min experiment (R/B = 96.0 vs. TO = 52.1 unit/reference) and the 30-min experiment (R/B = 97.6 vs. TO = 45.9). The R/B ratio showed a higher rate of change compared with TO at 1 min after clamping in the 15-min experiment (R/B = 80.1 vs. TO = 12.4). Both detection devices showed similar changes in pre- and post-clamp measurements in the 15- min experiment (R/B = 1.6 vs. TO = 3.8) and the 30-min experiment (R/B = 4.7 vs. TO =-4.5). In the 30-min experiment the R/B ratio showed a significant difference between preclamp, clamp, and post-clamp states (P= 0.026).

CONCLUSIONS

Both TO and digital image analysis were able to calculate an ischaemic drop in tissue oxygen saturation during periods of acute renal ischaemia. The findings suggest that the R/B ratio observed during histogram analysis shows a greater sensitivity compared with TO in quantifying renal ischaemia.

Evaluation of a quantitative blood oxygenation level-dependent (qBOLD) approach to map local blood oxygen saturation

Blood oxygen saturation (SO(2)) is a promising parameter for the assessment of brain tissue viability in numerous pathologies. Quantitative blood oxygenation level-dependent (qBOLD)-like approaches allow the estimation of SO(2) by modelling the contribution of deoxyhaemoglobin to the MR signal decay. These methods require a high signal-to-noise ratio to obtain accurate maps through fitting procedures. In this article, we present a version of the qBOLD method at long TE taking into account separate estimates of T(2), total blood volume fraction (BV(f)) and magnetic field inhomogeneities. Our approach was applied to the brains of 13 healthy rats under normoxia, hyperoxia and hypoxia. MR estimates of local SO(2) (MR_LSO(2)) were compared with measurements obtained from blood gas analysis. A very good correlation (R(2) = 0.89) was found between brain MR_LSO(2) and sagittal sinus SO(2).

Radiologic and near-infrared/optical spectroscopic imaging: where is the synergy?

OBJECTIVE

Optical and radiologic imaging are commonly used in preclinical research, and research into combined instruments for human applications is showing promise. The purpose of this article is to outline the fundamental limitations and advantages and to review the available systems. The emerging developments and future potential will be summarized.

CONCLUSION

Integration of hybrid systems is now routine at the preclinical level and appears in the form of specialized packages in which performance varies considerably. The synergy is commonly focused on using spatial localization from radiographs to provide structural data for spectroscopy; however, applications also exist in which the spectroscopy informs the use of radiologic imaging. Examples of clinical systems under research and development are shown.

Diffuse Optics for Tissue Monitoring and Tomography

This review describes the diffusion model for light transport in tissues and the medical applications of diffuse light. Diffuse optics is particularly useful for measurement of tissue hemodynamics, wherein quantitative assessment of oxy- and deoxy-hemoglobin concentrations and blood flow are desired. The theoretical basis for near-infrared or diffuse optical spectroscopy (NIRS or DOS, respectively) is developed, and the basic elements of diffuse optical tomography (DOT) are outlined. We also discuss diffuse correlation spectroscopy (DCS), a technique whereby temporal correlation functions of diffusing light are transported through tissue and are used to measure blood flow. Essential instrumentation is described, and representative brain and breast functional imaging and monitoring results illustrate the workings of these new tissue diagnostics.

Diagnosing breast cancer using Raman spectroscopy: prospective analysis

We present the first prospective test of Raman spectroscopy in diagnosing normal, benign, and malignant human breast tissues. Prospective testing of spectral diagnostic algorithms allows clinicians to accurately assess the diagnostic information contained in, and any bias of, the spectroscopic measurement. In previous work, we developed an accurate, internally validated algorithm for breast cancer diagnosis based on analysis of Raman spectra acquired from fresh-frozen in vitro tissue samples. We currently evaluate the performance of this algorithm prospectively on a large ex vivo clinical data set that closely mimics the in vivo environment. Spectroscopic data were collected from freshly excised surgical specimens, and 129 tissue sites from 21 patients were examined. Prospective application of the algorithm to the clinical data set resulted in a sensitivity of 83%, a specificity of 93%, a positive predictive value of 36%, and a negative predictive value of 99% for distinguishing cancerous from normal and benign tissues. The performance of the algorithm in different patient populations is discussed. Sources of bias in the in vitro calibration and ex vivo prospective data sets, including disease prevalence and disease spectrum, are examined and analytical methods for comparison provided.

Development of a transillumination infrared modality for differential vasoactive optical imaging

We present the development and implementation of a new near infrared transillumination imaging modality for tissue imaging. Exogenous inhaled hyperoxic and hypercarbic gases are used as "vasoactive contrast agents" via the production of changes in concentration of the endogenous HbO(2) and Hb in blood. This vasoactive differential imaging method is employed to acquire data and for subsequent image analysis. Spectroscopic changes obtained from transillumination measurements on the palms of healthy volunteers demonstrate the functionality of the imaging platform. This modality is being developed to monitor suspect breast lesions in a clinical setting based on the hypothesis that the atypical tumor vascular environment will yield sufficient contrast for differential optical imaging between diseased and healthy tissue.

Differentiation of angiogenic burden in human cancer xenografts using a perfusion-type optical contrast agent (SIDAG)

INTRODUCTION

Use of fluorescence imaging in oncology is evolving rapidly, and nontargeted fluorochromes are currently being investigated for clinical application. Here, we investigated whether the degree of tumour angiogenesis can be assessed in vivo by planar and tomographic methods using the perfusion-type cyanine dye SIDAG (1,1'-bis- [4-sulfobutyl]indotricarbocyanine-5,5'-dicarboxylic acid diglucamide monosodium).

METHOD

Mice were xenografted with moderately (MCF7, DU4475) or highly vascularized (HT1080, MDA-MB435) tumours and scanned up to 24 hours after intravenous SIDAG injection using fluorescence reflectance imaging. Contrast-to-noise ratio was calculated for all tumours, and fluorochrome accumulation was quantified using fluorescence-mediated tomography. The vascular volume fraction of the xenografts, serving as a surrogate marker for angiogenesis, was measured using magnetic resonance imaging, and blood vessel profile (BVP) density and vascular endothelial growth factor expression were determined.

RESULTS

SIDAG accumulation correlated well with angiogenic burden, with maximum contrast to noise ratio for MDA-MB435 (P < 0.0001), followed by HT1080, MCF7 and DU4475 tumours. Fluorescence-mediated tomography revealed 4.6-fold higher fluorochrome concentrations in MDA-MB435 than in DU4475 tumours (229 +/- 90 nmol/l versus 49 +/- 22 nmol/l; P < 0.05). The vascular volume fraction was 4.5-fold (3.58 +/- 0.9% versus 0.8 +/- 0.53%; P < 0.01), blood vessel profile density 5-fold (399 +/- 36 BVPs/mm2 versus 78 +/- 16 BVPs/mm2) and vascular endothelial growth factor expression 4-fold higher for MDA-MB435 than for DU4475 tumours.

CONCLUSION

Our data suggest that perfusion-type cyanine dyes allow assessment of angiogenesis in vivo using planar or tomographic imaging technology. They may thus facilitate characterization of solid tumours.

A prospective pilot clinical trial evaluating the utility of a dynamic near-infrared imaging device for characterizing suspicious breast lesions

Introduction

Characterizing and differentiating between malignant tumors, benign tumors, and normal breast tissue is increasingly important in the patient presenting with breast problems. Near-infrared diffuse optical imaging and spectroscopy is capable of measuring multiple physiologic parameters of biological tissue systems and may have clinical applications for assessing the development and progression of neoplastic processes, including breast cancer. The currently available application of near-infrared imaging technology for the breast, however, is compromised by low spatial resolution, tissue heterogeneity, and interpatient variation.

Materials and methods

We tested a dynamic near-infrared imaging schema for the characterization of suspicious breast lesions identified on diagnostic clinical ultrasound. A portable handheld near-infrared tissue imaging device (P-Scan; ViOptix Inc., Fremont, CA, USA) was utilized. An external mechanical compression force was applied to breast tissue. The tissue oxygen saturation and hemoglobin concentration were recorded simultaneously by the handheld near-infrared imaging device. Twelve categories of dynamic tissue parameters were derived based on real-time measurements of the tissue hemoglobin concentration and the oxygen saturation.

Results

Fifty suspicious breast lesions were evaluated in 48 patients. Statistical analyses were carried out on 36 out of 50 datasets that satisfied our inclusion criteria. Suspicious breast lesions identified on diagnostic clinical ultrasound had lower oxygenation and higher hemoglobin concentration than the surrounding normal breast tissue. Furthermore, histopathologic-proven malignant breast tumors had a lower differential hemoglobin contrast (that is, the difference of hemoglobin concentration variability between the suspicious breast lesion and the normal breast parenchyma located remotely elsewhere within the ipsilateral breast) as compared with histopathologic-proven benign breast lesions.

Conclusion

The proposed dynamic near-infrared imaging schema has the potential to differentiate benign processes from those of malignant breast tumors. Further development and refinement of the dynamic imaging device and additional subsequent clinical testing are necessary for optimizing the accuracy of detection.

Diagnosing breast cancer using diffuse reflectance spectroscopy and intrinsic fluorescence spectroscopy

Using diffuse reflectance spectroscopy and intrinsic fluorescence spectroscopy, we have developed an algorithm that successfully classifies normal breast tissue, fibrocystic change, fibroadenoma, and infiltrating ductal carcinoma in terms of physically meaningful parameters. We acquire 202 spectra from 104 sites in freshly excised breast biopsies from 17 patients within 30 min of surgical excision. The broadband diffuse reflectance and fluorescence spectra are collected via a portable clinical spectrometer and specially designed optical fiber probe. The diffuse reflectance spectra are fit using modified diffusion theory to extract absorption and scattering tissue parameters. Intrinsic fluorescence spectra are extracted from the combined fluorescence and diffuse reflectance spectra and analyzed using multivariate curve resolution. Spectroscopy results are compared to pathology diagnoses, and diagnostic algorithms are developed based on parameters obtained via logistic regression with cross-validation. The sensitivity, specificity, positive predictive value, negative predictive value, and overall diagnostic accuracy (total efficiency) of the algorithm are 100, 96, 69, 100, and 91%, respectively. All invasive breast cancer specimens are correctly diagnosed. The combination of diffuse reflectance spectroscopy and intrinsic fluorescence spectroscopy yields promising results for discrimination of breast cancer from benign breast lesions and warrants a prospective clinical study.

Development of a handheld near-infrared imager for dynamic characterization of in vivo biological tissue systems

A handheld near-infrared imager was developed for real-time monitoring of tissue physiologic changes in response to dynamic compression stimuli. Both 2D and 3D imaging schemas were developed for reconstruction of tissue heterogeneities based on optical measurements. The handheld imager and the dynamic imaging schema were validated on both benchtop phantoms and in vivo human tissues. The benchtop tests demonstrated that the imager was able to reconstruct absorption properties of the embedded heterogeneity with accuracy and repeatability. The tests on in vivo human tissues demonstrated that the imager was able to generate various dynamic loading profiles with reproducibility and to detect tissue optical, mechanical, and physiologic changes under the dynamic loading condition.

Three-dimensional time-resolved optical mammography of the uncompressed breast

Optical tomography is being developed as a means of detecting and specifying disease in the adult female breast. We present a series of clinical three-dimensional optical images obtained with a 32-channel time-resolved system and a liquid-coupled interface. Patients place their breasts in a hemispherical cup to which sources and detectors are coupled, and the remaining space is filled with a highly scattering fluid. A cohort of 38 patients has been scanned, with a variety of benign and malignant lesions. Images show that hypervascularization associated with tumors provides very high contrast due to increased absorption by hemoglobin. Only half of the fibroadenomas scanned could be observed, but of those that could be detected, all but one revealed an apparent increase in blood volume and a decrease in scatter and oxygen saturation.

Diode laser differential absorption spectrometry for measurements of some parameters of condensed media

A method of diode laser differential absorption spectrometry (DLDAS) is proposed. The method is based on the detection of absorption spectra variations caused by the changes of a parameter of a condensed media (temperature, composition of the components of a mixture, pH, etc.). Some simple theoretical background of the proposed technique is presented. The potentialities of the method are demonstrated in the experiments on remote contactless measurement of the temperature of aqueous solutions and measurement of the deviations of the composition of a mixture of dyes from the equilibrium state.

Diffuse optical imaging and spectroscopy for cancer

Visible light and near infrared light interact with biological tissue by absorption and scattering. Diffuse optical imaging and spectroscopy reconstructs tissue physiologic parameters based on noninvasive measurement of tissue optical properties. This technology can be used to differentiate physiologic and molecular signatures of both malignant and benign tissues, as they relate to the area of cancer research. Major advantages are the use of non-ionizing radiation, real-time continuous data acquisition, low cost, and portability. Limitations include low spatial resolution and limited reproducibility. This paper reviews the currently available state-of-the-art technologies for diffuse optical imaging and spectroscopy and their applications in cancer research.

Advances in methods for assessing tumor hypoxia in vivo: implications for treatment planning

Tumor hypoxia and its downstream effects have remained of considerable interest for decades due to its negative impact on response to various cancer therapies and promotion of metastasis. Diagnosing hypoxia non-invasively can provide a significant advancement in cancer treatment and is the dire necessity for implementing specific targeted therapies now emerging to treat different aspects of cancer. A variety of techniques are being proposed to do so. However, none of them has yet been established in the clinical arena. This review summarizes the methods currently available to assess tumor hypoxia in vivo and their respective advantages and shortcomings. It also points out the impedances that need to be overcome to establish any particular method in the clinic, along with a broad overview of requirements for further advancement in this sphere of cancer research.

Reconstruction of tissue heterogeneity by near infrared imaging: a novel algorithm and benchtop validation

A novel algorithm has been developed for Near Infrared (NIR) imaging of tissue optical properties with embedded heterogeneity. The algorithm was based on the optical measurements of the absorption perturbation by a matrix of multiple source detector pairs. Direct superimposition algorithm was used to calculate the two dimensional projected image of the tissue absorption. This absorption map is then compared with that of the homogenous phantom in order to reconstruct the absorption perturbation caused by the embedded object. Benchtop setup has been developed to validate this reconstruction scheme. Simulating tumors made of gelatin cylinders of high absorption coefficients were placed inside a homogenous intralipid phantom of specific background absorption. The depth of the tumor was adjusted at different levels and the diffuse reflectance was measured by a tissue imager consisting of a matrix of 4 sources and 4 detectors. The measured absorption coefficients were compared with the actual tumor absorption coefficients at different tumor depths in order to determine the reconstruction accuracy.

Near-infrared spectroscopy as a screening tool for patent ductus arteriosus in extremely low birth weight infants

BACKGROUND

Patent ductus arteriosus (PDA) is frequent and potentially pathologic in preterm infants. A simple bedside tool to screen for ductal patency would assist in the care of extremely low birth weight (ELBW) infants.

OBJECTIVE

To investigate the utility of near-infrared spectroscopy (NIRS) in identifying ELBW infants who would benefit from early echocardiography.

METHODS

Tissue oxygen saturation (S(t)O(2)) was measured by NIRS in the lungs, brain, skeletal muscle and kidney of 20 ELBW infants. Comparisons were made between the S(t)O(2) in these organs and the need for intervention for a PDA. All studies were performed within the first 4 days of life. Similar measurements were performed following treatment with indomethacin in nine of the patients.

RESULTS

The S(t)O(2) of skeletal muscle (left deltoid) and kidney differed between the infants who were treated for PDA and those who were not (p = 0.01 for both). As a screen for a PDA requiring intervention, deltoid S(t)O(2) had sensitivity 77% and specificity 83%, and kidney S(t)O(2) had sensitivity 85% and specificity 83%. Following treatment with indomethacin, the low S(t)O(2) in the deltoid and kidney increased toward the range seen in patients who did not require treatment of a PDA. Inter- and intra-observer variability ranged from minimal to high.

CONCLUSION

This pilot study of a portable NIRS device shows encouraging efficacy in identifying ELBW infants who were likely to benefit from early echocardiography and subsequent intervention to close a PDA. Further study is warranted.

Lasers in cancer detection and diagnosis research: enabling characteristics with illustrative examples

The salient properties of laser light and the way light interacts with biological tissues and molecular constituents of tissues offer possibilities for detection and diagnosis of cancer. In particular, the wavelength selectivity of tunable lasers, narrow bandwidth around the selected wavelength, and spectral brightness enable probing of key molecular constituents of tissues, and endow laser-based techniques with much desired diagnostic potential. This article presents an overview of some recent developments in optical imaging and optical biopsy of different types of cancers, and illustrates the diagnostic role of the color of light.

Scanning time-domain optical mammography: detection and characterization of breast tumors in vivo

Optical mammography is one of several new techniques for breast cancer detection and characterization presently under development for clinical use that provide information other than morphologic, in particular on the biochemical and metabolic state of normal and diseased tissue. In breast tissue, scattering of red to near infrared (NIR) light dominates absorption and NIR light may penetrate several centimeters through the breast. Optical mammography avoids the use of ionizing radiation and offers the power of diffuse optical spectroscopy. However, because of strong light scattering, spatial resolution of optical mammography is generally low. The paper reviews the results of a clinical study on scanning time-domain optical mammography comprising 154 patients carrying a total of 102 carcinomas validated by histology. Ninety two of these tumors were detected in optical mammograms retrospectively and for 87 of the detected tumors optical properties and tissue parameters were derived. In addition developments on instrumentation and data analysis are covered and possible improvements of optical mammography are briefly discussed.

Spectral and temporal near-infrared imaging of ex vivo cancerous and normal human breast tissues

Cancerous and normal ex vivo human breast tissues were investigated using spectroscopic and time-sliced two-dimensional (2-D) transillumination imaging methods in order to demonstrate the importance and potential of spectral and temporal measurements in breast cancer detection and diagnosis. The experimental arrangement for time-sliced optical imaging used 120 fs, 1 kHz repetition-rate, 800 nm light pulses from a Ti:sapphire laser system for sample illumination, and a 80 ps resolution ultrafast gated intensified camera system for recording 2-D time-sliced images. The spectroscopic imaging arrangement used 1225-1300 nm tunable output of a Cr: forsterite laser for sample illumination, a Fourier space gate to discriminate against multiple-scattered light, and a near-infrared area camera to record 2-D images. Images recorded with earlier temporal slices of transmitted light highlighted tumors, while those recorded with later slices accentuated normal tissues. When light was tuned closer to the 1203 nm absorption resonance of adipose tissues, a marked enhancement in contrast between the images of adipose and fibrous tissues was observed. A similar wavelength-dependent difference between normal and cancerous tissues was observed. These results correlate well with pathology and nuclear magnetic resonance based analyses of the samples.

Time-resolved optical mammography using a liquid coupled interface

A method has been devised for generating three-dimensional optical images of the breast using a 32-channel time-resolved system and a liquid-coupled interface. The breast is placed in a hemispherical cup surrounded by sources and detectors, and the remaining space is filled with a fluid with tissue-like optical properties. This approach has three significant benefits. First, cups can accommodate a large range of breast sizes, enabling the entire volume of the breast to be sampled. Second, the coupling of the source and detector optics at the surface is constant and independent of the subject, enabling intensity measurements to be employed in the image reconstruction. Third, the external geometry of the reconstructed volume is known exactly. Images of isolated targets with contrasting absorbing and scattering properties have been acquired, and the performance of the system has been evaluated in terms of the contrast, spatial resolution, and localization accuracy. These parameters were strongly dependent on the location of the targets within the imaged volume. Preliminary images of a healthy human subject are also presented, which reveal subtle heterogeneity, particularly in the distribution of scatter. The ability to detect an absorbing target adjacent to the breast is also demonstrated.

Breast cancer detection based on incremental biochemical and physiological properties of breast cancers: a six-year, two-site study

RATIONALE AND OBJECTIVES

To demonstrate that near-infrared spectroscopy would achieve sufficient sensitivity and specificity in human breast cancer to reach ROC/AUC values in the 90s and yet to warn of the potential liabilities of introduction of a novel technology in this field.

MATERIALS AND METHODS

116 subjects from two nations (44 were cancer-verified by biopsy and histopathology) were reviewed. NIR spectroscopy of total hemoglobin and its relative oxygenation were monitored in breast cancers and compared to their contralateral breast in a 2D nomogram for diagnostic evaluation. A novel handheld NIR breast cancer detector pad with a 3-wavelength LED and 8 detectors with 4 cm separation between source and detectors was placed on the subject's breast. The method is convenient, rapid, and safe and has achieved high patient compliance with minimal patient apprehension of compression, confinement, or radioactivity.

RESULTS

The absorbance increments of the cancerous region are referred to the mirror image location on the contralateral breast. The two metrics are increased hemoglobin concentration due to angiogenesis and decreased hemoglobin saturation due to hypermetabolism of the cancer. The 2D nomogram display of these two metrics shows Zone 1 contains verified cancers and Zone 2 contains noncancers. ROC evaluation of the nomogram gives 95% AUC for the two sites, Philadelphia and Leipzig.

CONCLUSION

A simple, economical breast cancer detector has achieved high patient compliance and a high ROC/AUC score for a population which involved a range of tumors down to and including those of 0.8-1 cm in diameter.

Time-domain scanning optical mammography: II. Optical properties and tissue parameters of 87 carcinomas

Within a clinical trial on scanning time-domain optical mammography reported on in a companion publication (part I), craniocaudal and mediolateral projection optical mammograms were recorded from 154 patients, suspected of having breast cancer. Here we report on in vivo optical properties of the subset of 87 histologically validated carcinomas which were visible in optical mammograms recorded at two or three near-infrared wavelengths. Tumour absorption and reduced scattering coefficients were derived from distributions of times of flight of photons recorded at the tumour site employing the model of diffraction of photon density waves by a spherical inhomogeneity, located in an otherwise homogeneous tissue slab. Effective tumour radii, taken from pathology, and tumour location along the compression direction, deduced from off-axis optical scans of the tumour region, were included in the analysis as prior knowledge, if available. On average, tumour absorption coefficients exceeded those of surrounding healthy breast tissue by a factor of about 2.5 (670 nm), whereas tumour reduced scattering coefficients were larger by about 20% (670 nm). From absorption coefficients at 670 nm and 785 nm total haemoglobin concentration and blood oxygen saturation were deduced for tumours and surrounding healthy breast tissue. Apart from a few outliers total haemoglobin concentration was observed to be systematically larger in tumours compared to healthy breast tissue. In contrast, blood oxygen saturation was found to be a poor discriminator for tumours and healthy breast tissue; both median values of blood oxygen saturation are the same within their statistical uncertainties. However, the ratio of total haemoglobin concentration over blood oxygen saturation further improves discrimination between tumours and healthy breast tissue. For 29 tumours detected in optical mammograms recorded at three wavelengths (670 nm, 785 nm, 843 nm or 884 nm), scatter power was derived from transport scattering coefficients. Scatter power of tumours tends to be larger than that of surrounding healthy breast tissue, yet the 95% confidence intervals of both medians overlap.

Time-resolved optical mammography between 637 and 985 nm: clinical study on the detection and identification of breast lesions

The first time-resolved optical mammograph operating beyond 900 nm was tested in a retrospective clinical study involving 194 patients with malignant and benign lesions, to investigate the diagnostic potential for the detection and characterization of breast lesions. For the first part of the study (101 patients with 114 lesions), the system was operated at 683, 785, 913 and 975 nm. Subsequently, to improve the spectral content of optical images, the number of wavelengths was increased (up to 7) and the spectral range was extended (637-985 nm). Late gated intensity and scattering images provide sensitivity to tissue composition (oxy- and deoxyhaemoglobin, water and lipids) and physiology (total haemoglobin content and oxygen saturation), as well as to structural changes. Tumours are typically identified because of the strong blood absorption at short wavelengths (637-685 nm), while cysts are characterized by low scattering, leading to a detection rate of approximately 80% for both lesion types, when detection is required in both cranio-caudal and oblique views. The detection rate for other benign lesions, such as fibroadenomas, is presently much lower (<40%). The effectiveness of the technique in localizing and identifying different lesion types was analysed as a function of various parameters (lesion size, compressed breast thickness, age, body mass index, breast parenchymal pattern). The possibility that physiologic changes due to the development of a malignant lesion could affect the entire breast was investigated. The capacity to assess the density of breast based on the average scattering properties was also tested.

Time-domain scanning optical mammography: I. Recording and assessment of mammograms of 154 patients

Using a triple wavelength (670 nm, 785 nm, 843/884 nm) scanning laser-pulse mammograph we recorded craniocaudal and mediolateral projection optical mammograms of 154 patients, suspected of having breast cancer. From distributions of times of flight of photons recorded at typically 1000-2000 scan positions, optical mammograms were derived displaying (inverse) photon counts in selected time windows, absorption and reduced scattering coefficients or total haemoglobin concentration and blood oxygen saturation. Optical mammograms were analysed by comparing them with x-ray and MR mammograms, including results of histopathology, attributing a subjective visibility score to each tumour assessed. Out of 102 histologically confirmed tumours, 72 tumours were detected retrospectively in both optical projection mammograms, in addition 20 cases in one projection only, whereas 10 tumours were not detectable in any projection. Tumour contrast and contrast-to-noise ratios of mammograms of the same breast, but derived from measured DTOFs by various methods were quantitatively compared. On average, inverse photon counts in selected time windows, including total photon counts, provide highest tumour contrast and contrast-to-noise ratios. Based on the results of the present study we developed a multi-wavelength, multi-projection scanning time-domain optical mammograph with improved spectral and spatial (angular) sampling, that allows us to record entire mammograms simultaneously at various offsets between the transmitting fibre and receiving fibre bundle and provides first results for illustration.

Characterization of female breast lesions from multi-wavelength time-resolved optical mammography

Characterization of both malignant and benign lesions in the female breast is presented as the result of a clinical study that involved more than 190 subjects in the framework of the OPTIMAMM European project. All the subjects underwent optical mammography, by means of a multi-wavelength time-resolved mammograph, in the range 637-985 nm. Optical images were processed by applying a perturbation model, relying on a nonlinear approximation of time-resolved transmittance curves in the presence of an inclusion, with the aim of estimating the major tissue constituents (i.e. oxy- and deoxy-haemoglobin, lipid and water) and structural parameters (linked to dimension and density of the scatterer centres) for both the lesion area and the surrounding tissue. The critical factors for the application of the perturbation model on in vivo data are also discussed. Forty-six malignant and 68 benign lesions were analysed. A subset of 32 cancers, 40 cysts and 14 fibroadenomas were found reliable for the perturbation analysis. For cancers, we show a higher blood content with respect to the surrounding tissue, while cysts are characterized by a lower concentration of scattering centres with respect to the surrounding tissue. For fibroadenomas, the low number of cases does not allow any definite conclusions.