Imaging tumor oxyhemoglobin and deoxyhemoglobin concentrations with ultrasound-guided diffuse optical tomography

Ultra-miniature dual-wavelength spatial frequency domain imaging for micro-endoscopy

Significance

There is a need for a cost-effective, quantitative imaging tool that can be deployed endoscopically to better detect early stage gastrointestinal cancers. Spatial frequency domain imaging (SFDI) is a low-cost imaging technique that produces near-real time, quantitative maps of absorption and reduced scattering coefficients, but most implementations are bulky and suitable only for use outside the body.

Aim

We aim to develop an ultra-miniature SFDI system comprising an optical fiber array (diameter 0.125 mm) and a micro camera (1 × 1    mm package) to displace conventionally bulky components, in particular, the projector.

Approach

First, we fabricated a prototype with an outer diameter of 3 mm, although the individual component dimensions could permit future packaging to a < 1.5    mm diameter. We developed a phase-tracking algorithm to rapidly extract images with fringe projections at three equispaced phase shifts to perform SFDI demodulation.

Results

To validate the performance, we first demonstrate comparable recovery of quantitative optical properties between our ultra-miniature system and a conventional bench-top SFDI system with an agreement of 15% and 6% for absorption and reduced scattering, respectively. Next, we demonstrate imaging of absorption and reduced scattering of tissue-mimicking phantoms providing enhanced contrast between simulated tissue types (healthy and tumour), done simultaneously at wavelengths of 515 and 660 nm. Using a support vector machine classifier, we estimate that sensitivity and specificity values of > 90 % are feasible for detecting simulated squamous cell carcinoma.

Conclusions

This device shows promise as a cost-effective, quantitative imaging tool to detect variations in optical absorption and scattering as indicators of cancer.

MamoRef: an optical mammography device using whole-field CW diffuse reflectance. Presentation, validation and preliminary clinical results

Objective.MamoRef is an mammography device that uses near-infrared light, designed to provide clinically relevant information for the screening of diseases of the breast. Using low power continuous wave lasers and a high sensitivity CCD (Charge-coupled device) that captures a diffusely reflected image of the tissue, MamoRef results in a versatile diagnostic tool that aims to fulfill a complementary role in the diagnosis of breast cancer providing information about the relative hemoglobin concentrations as well as oxygen saturation.Approach.We present the design and development of an initial prototype of MamoRef. To ensure its effectiveness, we conducted validation tests on both the theoretical basis of the reconstruction algorithm and the hardware design. Furthermore, we initiated a clinical feasibility study involving patients diagnosed with breast disease, thus evaluating the practical application and potential benefits of MamoRef in a real-world setting.Main results.Our study demonstrates the effectiveness of the reconstruction algorithm in recovering relative concentration differences among various chromophores, as confirmed by Monte Carlo simulations. These simulations show that the recovered data correlates well with the ground truth, with SSIMs of 0.8 or more. Additionally, the phantom experiments validate the hardware implementation. The initial clinical findings exhibit highly promising outcomes regarding MamoRef's ability to differentiate between lesions.Significance.MamoRef aims to be an advancement in the field of breast pathology screening and diagnostics, providing complementary information to standard diagnostic techniques. One of its main advantages is the ability of determining oxy/deoxyhemoglobin concentrations and oxygen saturation; this constitutes valuable complementary information to standard diagnostic techniques. Besides, MamoRef is a portable and relatively inexpensive device, intended to be not only used in specific medical imaging facilities. Finally, its use does not require external compression of the breast. The findings of this study underscore the potential of MamoRef in fulfilling this crucial role.

Optimizing Tissue Oxygenation in Reduction Mammoplasty: The Role of Continuous Diffusion of Oxygen: A Feasibility Pilot Randomized Controlled Trial

INTRODUCTION

Bilateral reduction mammoplasty (BRM) aims to alleviate macromastia-related symptoms in women. This procedure involves a T-Junction suture at the medial inframammary fold that encompasses 12%-39% of wound breakdowns mainly due to reduced perfusion. Continuous diffusion of oxygen (CDO) may enhance breast tissue oxygenation to prevent such complication. We explored the feasibility of this therapy.

METHODS

A 4-wk feasibility-pilot randomized controlled trial of women undergoing BRM was conducted. By internal randomization (left/right side), participants received standard of care (SOC) in one breast using topical skin adhesive, while their other breast received SOC + CDO at the T-junction covered by a silicon sheet (sCDO), or CDO directly to the T-Junction skin (dCDO). Feasibility outcomes included protocol delivery, outcome measurement, device-related adverse events, and device acceptability. Exploratory outcomes were T-Junction SatO2 and deoxyhemoglobin assessed with near-infrared spectroscopy and wound dehiscence.

RESULTS

Sixteen participants (age = 33 ± 8 y; body mass index = 34.34 ± 5.85 kg/m2) were recruited, conforming n = 32 breasts (SOC, n = 16; dCDO, n = 10, sCDO, n = 6). At 4 wk, protocol delivery was 93.7%, outcome measuring 100%, and device-related adverse events 0%. Device acceptability showed an 85.4% strong agreement for attitude toward use, 78.2% perceived ease of use, and 77.7% perceived usefulness. Breasts undergoing sCDO showed higher SatO2 (P < 0.001), whereas lower deoxyhemoglobin (P < 0.001) compared to all other breast groups. However, wound dehiscence was not different between groups (P = 0.66).

CONCLUSIONS

Self-applied CDO to the T-Junction is feasible, safe, and acceptable, in patients undergoing BRM. In a proper wound environment, CDO may enhance breast tissue oxygenation. However, it is unclear whether CDO leads to decreased wound dehiscence. This study showed reproducibility for larger randomized trials.

Noninvasive hemoglobin sensing and imaging: optical tools for disease diagnosis

SIGNIFICANCE

Measurement and imaging of hemoglobin oxygenation are used extensively in the detection and diagnosis of disease; however, the applied instruments vary widely in their depth of imaging, spatiotemporal resolution, sensitivity, accuracy, complexity, physical size, and cost. The wide variation in available instrumentation can make it challenging for end users to select the appropriate tools for their application and to understand the relative limitations of different methods.

AIM

We aim to provide a systematic overview of the field of hemoglobin imaging and sensing.

APPROACH

We reviewed the sensing and imaging methods used to analyze hemoglobin oxygenation, including pulse oximetry, spectral reflectance imaging, diffuse optical imaging, spectroscopic optical coherence tomography, photoacoustic imaging, and diffuse correlation spectroscopy.

RESULTS

We compared and contrasted the ability of different methods to determine hemoglobin biomarkers such as oxygenation while considering factors that influence their practical application.

CONCLUSIONS

We highlight key limitations in the current state-of-the-art and make suggestions for routes to advance the clinical use and interpretation of hemoglobin oxygenation information.

In vivo photoacoustic assessment of the oxygen saturation changes in the human radial artery: a preliminary study associated with age

SIGNIFICANCE

We demonstrate the potential of probing the sO2 change under blood flow in vivo using photoacoustic (PA) imaging and sheds light on the complex relationship between RBC aggregation and oxygen delivery.

AIM

To conduct in vivo assessments of the sO2 in the radial artery of healthy volunteers and simultaneously probe the relation between the sO2 and hemodynamic behavior such as red blood cell (RBC) aggregation.

APPROACH

The effects of PA-based measurements of blood hemodynamics were studied as a function of the subjects' age (20s, 30s, and 40s). The pulsatile blood flow in the human radial artery of 12 healthy subjects was imaged in the 700 to 900 nm optical wavelength range using a linear array-based PA system.

RESULTS

The PA power when blood velocity is minimum (Pamax) was larger than the one attained at maximum blood velocity (Pamin), consistent with predictions based on the cyclical variation of RBC aggregation during pulsatile flow. The difference between Pamin and Pamax at 800 nm (ΔPa800) increased with age (1.7, 2.2, and 2.6 dB for age group of 20s, 30s, and 40s, respectively). The sO2 computed from Pamax was larger than the one from Pamin.

CONCLUSIONS

The ΔPa800 increased with participant age. The ΔPa800 metric could be a surrogate of noninvasively monitoring the age-induced changes in RBC aggregation. The sO2 change during a cycle of pulsatile blood flow also increased with age, demonstrating that RBC aggregation can affect the sO2 change.

Method for Quantitative Broadband Diffuse Optical Spectroscopy of Tumor-Like Inclusions

A hybrid reflectance-based diffuse optical imaging (DOI) technique combining discrete wavelength frequency-domain (FD) near-infrared spectroscopy (NIRS) with broadband continuous wave NIRS measurements was developed to quantify the broadband optical properties of deep tumor-like inclusions. This method was developed to more accurately measure the broadband optical properties of human tumors using a compact handheld imaging probe and without requiring a priori spectral constraints. We simulated the reconstruction of absorption and scattering spectra (650–1000 nm) of human breast tumors in a homogeneous background at depths of 0 to 10 mm. The hybrid DOI technique demonstrated enhanced performance in reconstruction of optical absorption with a mean accuracy over all 71 wavelengths of 8.39% versus 32.26% for a 10 mm deep tumor with the topographic DOI method. The new hybrid technique was also tested and validated on two heterogeneous tissue-simulating phantoms with inclusion depths of 2, 7, and 9 mm. The mean optical absorption accuracy over all wavelengths was similarly improved up to 5x for the hybrid DOI method versus topographic DOI for the deepest inclusions.

Value of combining dynamic contrast enhanced ultrasound and optoacoustic tomography for hypoxia imaging

Optoacoustic imaging (OAI) can detect haemoglobin and assess its oxygenation. However, the lack of a haemoglobin signal need not indicate a lack of perfusion. This study uses a novel method to assist the co-registration of optoacoustic images with dynamic contrast enhanced ultrasound (DCE-US) images to demonstrate, in preclinical tumour models, the value of combining haemoglobin imaging with a perfusion imaging method, showing that a lack of a haemoglobin signal does not necessarily indicate an absence of perfusion. DCE-US was chosen for this particular experiment because US is extremely sensitive to microbubble contrast agents and because microbubbles, like red blood cells but unlike currently available optical contrast agents, do not extravasate. Significant spatial correlations were revealed between the DCE-US properties and tumour blood-oxygen saturation and haemoglobin, as estimated using OAI. It is speculated that DCE-US properties could be applied as surrogate biomarkers for hypoxia when planning clinical radiotherapy or chemotherapy.

Identification of the S100 fused-type protein hornerin as a regulator of tumor vascularity

Sustained angiogenesis is essential for the development of solid tumors and metastatic disease. Disruption of signaling pathways that govern tumor vascularity provide a potential avenue to thwart cancer progression. Through phage display-based functional proteomics, immunohistochemical analysis of human pancreatic ductal carcinoma (PDAC) specimens, and in vitro validation, we reveal that hornerin, an S100 fused-type protein, is highly expressed on pancreatic tumor endothelium in a vascular endothelial growth factor (VEGF)-independent manner. Murine-specific hornerin knockdown in PDAC xenografts results in tumor vessels with decreased radii and tortuosity. Hornerin knockdown tumors have significantly reduced leakiness, increased oxygenation, and greater apoptosis. Additionally, these tumors show a significant reduction in growth, a response that is further heightened when therapeutic inhibition of VEGF receptor 2 (VEGFR2) is utilized in combination with hornerin knockdown. These results indicate that hornerin is highly expressed in pancreatic tumor endothelium and alters tumor vessel parameters through a VEGF-independent mechanism.Angiogenesis is essential for solid tumor progression. Here, the authors interrogate the proteome of pancreatic cancer endothelium via phage display and identify hornerin as a critical protein whose expression is essential to maintain the pancreatic cancer vasculature through a VEGF-independent mechanism.

Optical-flow analysis toolbox for characterization of spatiotemporal dynamics in mesoscale optical imaging of brain activity

Wide-field optical imaging techniques constitute powerful tools to investigate mesoscale neuronal activity. The sampled data constitutes a sequence of image frames in which one can investigate the flow of brain activity starting and terminating at source and sink locations respectively. Approaches to the analyses of information flow include qualitative assessment to identify sources and sinks of activity as well as their trajectories, and quantitative measurements based on computing the temporal variation of the intensity of pixels. Furthermore, in a few studies estimates of wave motion have been reported using optical-flow techniques from computer vision. However, a comprehensive toolbox for the quantitative analyses of mesoscale brain activity data is still lacking. We present a graphical-user-interface toolbox based in Matlab® for investigating the spatiotemporal dynamics of mesoscale brain activity using optical-flow analyses. The toolbox includes the implementation of three optical-flow methods namely Horn-Schunck, Combined Local-Global, and Temporospatial algorithms for estimating velocity vector fields of flow of mesoscale brain activity. From the velocity vector fields we determined the locations of sources and sinks as well as the trajectories and temporal velocities of flow of activity. Using simulated data as well as experimentally derived sensory-evoked voltage and calcium imaging data from mice, we compared the efficacy of the three optical-flow methods for determining spatiotemporal dynamics. Our results indicate that the combined local-global method we employed, yields the best results for estimating wave motion. The automated approach permits rapid and effective quantification of mesoscale brain dynamics and may facilitate the study of brain function in response to new experiences or pathology.

Differentiation of tumor vasculature heterogeneity levels in small animals based on total hemoglobin concentration using magnetic resonance-guided diffuse optical tomography in vivo

Insight into the vasculature of the tumor in small animals has the potential to impact many areas of cancer research. The heterogeneity of the vasculature of a tumor is directly related to tumor stage and disease progression. In this small scale animal study, we investigated the feasibility of differentiating tumors with different levels of vasculature heterogeneity in vivo using a previously developed hybrid magnetic resonance imaging (MRI) and diffuse optical tomography (DOT) system for small animal imaging. Cross-sectional total hemoglobin concentration maps of 10 Fisher rats bearing R3230 breast tumors are reconstructed using multi-wavelength DOT measurements both with and without magnetic resonance (MR) structural a priori information. Simultaneously acquired MR structural images are used to guide and constrain the DOT reconstruction, while dynamic contrast-enhanced MR functional images are used as the gold standard to classify the vasculature of the tumor into two types: high versus low heterogeneity. These preliminary results show that the stand-alone DOT is unable to differentiate tumors with low and high vascular heterogeneity without structural a priori information provided by a high resolution imaging modality. The mean total hemoglobin concentrations comparing the vasculature of the tumors with low and high heterogeneity are significant (p-value 0.02) only when MR structural a priori information is utilized.

Noninvasive Surface Imaging of Breast Cancer in Humans using a Hand-held Optical Imager

X-ray mammography, the current gold standard for breast cancer detection, has a 20% false-negative rate (cancer is undetected) and increases in younger women with denser breast tissue. Diffuse optical imaging (DOI) is a safe (nonionizing), and relatively inexpensive method for noninvasive imaging of breast cancer in human subjects (including dense breast tissues) by providing physiological information (e.g. oxy- and deoxy- hemoglobin concentration). At the Optical Imaging Laboratory, a hand-held optical imager has been developed which employs a breast contourable probe head to perform simultaneous illumination and detection of large surfaces towards near real-time imaging of human breast cancer. Gen-1 and gen-2 versions of the handheld optical imager have been developed and previously demonstrated imaging in tissue phantoms and healthy human subjects. Herein, the hand-held optical imagers are applied towards in vivo imaging of breast cancer subjects in an attempt to determine the ability of the imager to detect breast tumors. Five female human subjects (ages 51-74) diagnosed with breast cancer were imaged with the gen-1 optical imager prior to surgical intervention. One of the subjects was also imaged with the gen-2 optical imager. Both imagers use 785 nm laser diode sources and ICCD camera detectors to generate 2D surfaces maps of total hemoglobin absorption. The subjects lay in supine position and images were collected at various locations on both the ipsilateral (tumor-containing) and contralateral (non-tumor containing) breasts. The optical images (2D surface maps of optical absorption due to total hemoglobin concentration) show regions of higher intensity at the tumor location, which is indicative of increased vasculature and higher blood content due to the presence of the tumor. Additionally, a preliminary result indicates the potential to image lymphatic spread. This study demonstrates the potential of the hand-held optical devices to noninvasively image breast cancer in human subjects.

Effect of vascular haemoglobin concentrations on ultrasound-guided diffuse optical tomography in differentiating benign from malignant breast lesions

OBJECTIVES

Ultrasound-guided diffuse optical tomography (US-DOT) can potentially detect breast carcinomas by measuring total tumour haemoglobin concentrations (TTHC). The purpose of this study was to evaluate whether vascular haemoglobin concentrations (VHC) affect the ability of US-DOT to distinguish breast carcinomas from benign.

MATERIALS AND METHODS

In 85 women (97 palpable lesions) referred for core breast biopsy, we measured VHC with a complete blood count and calculated TTHCs for each lesion with US-DOT. Anaemia was defined as a VHC less than 120.0 g/L.

RESULTS

Mean TTHCs were significantly higher in malignant lesions (n = 53) than in benign lesions (n = 44), regardless of whether the lesions were from women with anaemia (TTHC, 248.5 vs. 123.3 μmol/L; P = 0.001) or from those without (TTHC, 229.7 vs. 173.9 μmol/L; P = 0.016). A cut-off TTHC of 155.1 μmol/L provided 81.3 % sensitivity, 81.8 % specificity and 81.5 % accuracy for detecting malignant tumours in women with anaemia and 78.4 % sensitivity, 54.5 % specificity and 67.1 % accuracy for women without. There was no significant difference in sensitivity (P = 0.813), specificity (P = 0.108) and accuracy (P = 0.162) between the anaemic group and the non-anaemic group.

CONCLUSIONS

Vascular haemoglobin concentrations did not affect the ability of US-DOT to differentiate breast carcinomas from benign lesions.

KEY POINTS

• US-DOT can differentiate benign from malignant breast lesions by measuring TTHC. • No difference in TTHC between the anaemia and non-anaemia group. • Vascular haemoglobin concentrations do not affect the diagnostic ability of US-DOT.

An ideal-observer framework to investigate signal detectability in diffuse optical imaging

With the emergence of diffuse optical tomography (DOT) as a non-invasive imaging modality, there is a requirement to evaluate the performance of the developed DOT systems on clinically relevant tasks. One such important task is the detection of high-absorption signals in the tissue. To investigate signal detectability in DOT systems for system optimization, an appropriate approach is to use the Bayesian ideal observer, but this observer is computationally very intensive. It has been shown that the Fisher information can be used as a surrogate figure of merit (SFoM) that approximates the ideal observer performance. In this paper, we present a theoretical framework to use the Fisher information for investigating signal detectability in DOT systems. The usage of Fisher information requires evaluating the gradient of the photon distribution function with respect to the absorption coefficients. We derive the expressions to compute the gradient of the photon distribution function with respect to the scattering and absorption coefficients. We find that computing these gradients simply requires executing the radiative transport equation with a different source term. We then demonstrate the application of the SFoM to investigate signal detectability in DOT by performing various simulation studies, which help to validate the proposed framework and also present some insights on signal detectability in DOT.

Breast cancer: assessing response to neoadjuvant chemotherapy by using US-guided near-infrared tomography

PURPOSE

To assess initial breast tumor hemoglobin (Hb) content before the initiation of neoadjuvant chemotherapy, monitor the Hb changes at the end of each treatment cycle, and correlate these findings with tumor pathologic response.

MATERIALS AND METHODS

The HIPAA-compliant study protocol was approved by the institutional review boards of both institutions. Written informed consent was obtained from all patients. Patients who were eligible for neoadjuvant chemotherapy were recruited between December 2007 and May 2011, and their tumor Hb content was assessed by using a near-infrared imager coupled with an ultrasonography (US) system. Thirty-two women (mean age, 48 years; range, 32-82 years) were imaged before treatment, at the end of every treatment cycle, and before definitive surgery. The patients were graded in terms of their final pathologic response on the basis of the Miller-Payne system as nonresponders and partial responders (grades 1-3) and near-complete and complete responders (grades 4 and 5). Tumor vascularity was assessed from total Hb (tHb), oxygenated Hb (oxyHb), and deoxygenated Hb (deoxyHb) concentrations. Tumor vascularity changes during treatment were assessed from percentage tHb normalized to the pretreatment level. A two-sample two-sided t test was used to calculate the P value and to evaluate statistical significance between groups. Bonferroni-Holm correction was applied to obtain the corrected P value for multiple comparisons.

RESULTS

There were 20 Miller-Payne grade 1-3 tumors and 14 grade 4 or 5 tumors. Mean maximum pretreatment tHb, oxyHb, and deoxyHb levels were significantly higher in grade 4 and 5 tumors than in grade 1-3 tumors (P = .005, P = .008, and P = .017, respectively). The mean percentage tHb changes were significantly higher in grade 4 or 5 tumors than in grade 1-3 tumors at the end of treatment cycles 1-3 (P = .009 and corrected P = .009, P = .002 and corrected P = .004, and P < .001 and corrected P < .001, respectively).

DISCUSSION

These findings indicate that initial tumor Hb content is a strong predictor of final pathologic response. Additionally, the tHb changes during early treatment cycles can further predict final pathologic response.