Effect of direct voltage induction by low-frequency security systems on neurostimulator lead

Low-frequency (LF) security systems, such as antitheft electronic article surveillance (EAS) gates emit strong magnetic fields that could potentially interfere with neurostimulator operation. Some patients reported pain and shocking sensations near EAS gates, even after they turned off their pulse generator. To investigate the direct voltage induction of EAS systems on neurostimulator leads, we evaluated voltages induced by two EAS systems (14 kHz continuous wave or 58 kHz pulsed) on a 40 cm sacral neurostimulator lead formed in a circular loop attached to a pulse generator that was turned off. The lead and neurostimulator were mounted in a saline-filled rectangular phantom placed within electromagnetic fields emitted by EAS systems. The measured voltage waveforms were applied to computational models of spinal nerve axons to predict whether these voltages may evoke action potentials. Additional in vitro testing was performed on the semicircular lead geometry, to study the effect of lead geometry on EAS induced voltages. While standard neurostimulator testing per ISO 14708-3:2017 recommends electromagnetic compatibility testing with LF magnetic fields for induction of malfunctions of the active electronic circuitry while generating intended stimulating pulses, our results show that close to the EAS antenna frames, the induced voltage on the lead could be strong enough to evoke action potentials, even with the pulse generator turned off. This work suggests that patient reports of pain and shocking sensations when near EAS systems could also be correlated with the direct EAS-induced voltage on neurostimulator lead.

Amplitude- and frequency-dependent activation of layer II/III neurons by intracortical microstimulation

Intracortical microstimulation (ICMS) has been used for the development of brain machine interfaces. However, further understanding about the spatiotemporal responses of neurons to different electrical stimulation parameters is necessary to inform the design of optimal therapies. In this study, we employed in vivo electrophysiological recording, two-photon calcium imaging, and electric field simulation to evaluate the acute effect of ICMS on layer II/III neurons. Our results show that stimulation frequency non-linearly modulates neuronal responses, whereas the magnitude of responses is linearly correlated to the electric field strength and stimulation amplitude before reaching a steady state. Temporal dynamics of neurons' responses depends more on stimulation frequency and their distance to the stimulation electrode. In addition, amplitude-dependent post-stimulation suppression was observed within ∼500 μm of the stimulation electrode, as evidenced by both calcium imaging and local field potentials. These findings provide insights for selecting stimulation parameters to achieve desirable spatiotemporal specificity of ICMS.

Optical Imaging Technology: A Useful Tool to Identify Remission in Cushing Disease After Surgery

We recently reported the use of optical imaging technology to quantify facial plethora in endogenous Cushing syndrome (CS). In the present study, we studied a larger cohort of patients with Cushing disease (CD) and examined water content fraction as well as blood volume fraction as bio-optic markers for determining the efficacy of this methodology as a predictor of lasting remission after surgery for CS. We imaged 49 patients before and after transsphenoidal surgery (TSS) for Cushing disease (CD); 22 patients were also seen at 3-6 months, and 13 patients 12 months post-operatively. On all patients, we used multi-spectral imaging (MSI) to evaluate hemodynamic distributions as well as water content at a specific area of the face. We found a decrease in blood volume fraction after vs. before surgical treatment in the tested facial area in 37 of the 40 patients, as determined with biochemical markers (p<0.001). All patients that were followed up for up to 12 months showed the same decrease from preoperative values and they remained in remission from CD. We conclude that MSI can be used for the evaluation of remission from CD, at least in the immediate post-operative period and up to one year after surgery. The use of this technology can supplement biochemical and other testing for the evaluation of the various treatment modalities available for patients with CD.

Using in vivo fluorescence lifetime imaging to detect HER2-positive tumors

Background

Assessment of the status of tumor biomarkers in individual patients would facilitate personalizing treatment strategy, and continuous monitoring of those biomarkers and their binding process to the therapeutic drugs would provide a means for early evaluation of the efficacy of therapeutic intervention. Fluorescent probes can accumulate inside the tumor region due to the leakiness of its vascularization and this can make it difficult to distinguish if the measured fluorescence intensity is from probes bound to target receptors or just accumulated unbound probes inside the tumor. In this paper, we have studied the fluorescence lifetime as a means to distinguish bound HER2 specific affibody probes to HER2 receptors.

Our imaging system is a time-resolved fluorescence system using a Ti-Sapphire femtosecond pulse laser as source and Time correlated Single photon Counting (TCSPC) system as detector for calculating the lifetime of the contrast agent. HER2-specific Affibody (His6-ZHER2:GS-Cys) (Affibody, Stockholm, Sweden) conjugated with a Dylight750 fluorescent probe (Thermo-Fisher-Scientific, Waltham, Massachusetts) was used as contrast agent and six human cancer cell lines, BT-474, SKOV-3, NCI-N87, MDA-MB-361, MCF-7, and MDA-MB-468, known to express different levels of HER2/neu, are used in athymic mice xenografts.

Results

By comparing the lifetime of unbound contrast agent (at the contralateral site) to the fluorescence lifetime at the tumor site, our results show that the fluorescence lifetime decreases as HER2 specific Affibody probes bind to the tumor receptors. A decrease of ~15% (100ps) in tumor fluorescence lifetime was observed in tumors with mid to high HER2 expression. Smaller decreases were observed in tumors with low-level of HER2 receptors and no change was observed in the non-HER2-expressing tumors.

Conclusions

Using HER2-specific Affibody conjugated with the Dylight750 fluorescent probe as contrast agent, we demonstrated in live animals that change in fluorescence lifetime of the bound contrast agent can be used to assess the high to mid-level expression of HER2 expressing tumors in-vivo in only one measurement. The rationale is that the fluorescence lifetime of our specific probe is sensitive to affinity to, and specific interaction with, other molecules.

Facial Plethora: Modern Technology for Quantifying an Ancient Clinical Sign and Its Use in Cushing Syndrome

CONTEXT

Facial plethora is a clinical sign described since ancient times for a variety of diseases. In the 19th century, it was linked to increased blood volume or flow, but this has never been proven. Facial plethora is also one of the earliest described clinical features of Cushing's syndrome (CS).

OBJECTIVE

This study aimed to quantify facial plethora changes in CS as an early assessment of cure after surgery using noninvasive near-infrared multispectral imaging (MSI).

DESIGN

The longitudinal cohort study was initiated in August 2012 and completed in August 2014.

SETTING

Clinical research hospital, National Institutes of Health.

PATIENTS

Thirty-four of the 38 patients who received surgical treatment for CS under protocol 97CH0076 during this period were included.

INTERVENTION(S)

MSI was performed on the right cheek of patients before surgery and 4.9 ± 3.1 days afterward.

MAIN OUTCOME MEASURE(S)

Average blood volume fraction as measured by MSI and serum cortisol.

RESULTS

All but four of the 28 patients (86%) who were assessed as cured by postoperative plasma cortisol measurements of < 3 μg/dL showed a decrease in blood volume fraction (17.7 ± 0.03 vs 15.8 ± 0.03%; P = .0019), whereas an increase was seen in patients with persistent CS (18.5 ± 0.03 vs 21.4 ± 0.04%; P = .0017). Change in blood volume fraction before and after surgery was correlated with postoperative cortisol (rs = 0.58; P = .0003).

CONCLUSIONS

Clinical data obtained from 34 patients indicate that a decrease in facial plethora after surgery, as evidenced by a decrease in blood volume fraction, is correlated with CS outcome. This novel technology for the first time identified a physiological mechanism associated with an ancient clinical sign. Furthermore, as a proof of principle, MSI is a promising early marker of cure in patients with CS that complements biochemical and clinical data.

Relative brain signature: a population-based feature extraction procedure to identify functional biomarkers in the brain of alcoholics

BACKGROUND

A novel feature extraction technique, Relative-Brain-Signature (RBS), which characterizes subjects' relationship to populations with distinctive neuronal activity, is presented. The proposed method transforms a set of Electroencephalography's (EEG) time series in high dimensional space to a space of fewer dimensions by projecting time series onto orthogonal subspaces.

METHODS

We apply our technique to an EEG data set of 77 abstinent alcoholics and 43 control subjects. To characterize subjects' relationship to the alcoholic and control populations, one RBS vector with respect to the alcoholic and one with respect to the control population is constructed. We used the extracted RBS vectors to identify functional biomarkers over the brain of alcoholics. To achieve this goal, the classification algorithm was used to categorize subjects into alcoholics and controls, which resulted in 78% accuracy.

RESULTS AND CONCLUSIONS

Using the results of the classification, regions with distinctive functionality in alcoholic subjects are detected. These affected regions, with respect to their spatial extent, are frontal, anterior frontal, centro-parietal, parieto-occiptal, and occipital lobes. The distribution of these regions over the scalp indicates that the impact of the alcohol in the cerebral cortex of the alcoholics is spatially diffuse. Our finding suggests that these regions engage more of the right hemisphere relative to the left hemisphere of the alcoholics' brain.

Multiscale BerEp4 molecular imaging of microtumor phantoms: toward theranostics for basal cell carcinoma

Basal cell carcinoma (BCC), the most common cancer in humans, appears macroscopically and microscopically similar to many other skin lesions, which makes differential diagnosis difficult. We are developing an approach for quantitative molecular imaging of BerEP4, a transmembrane biomarker for BCC, with the goal of increasing the precision and accuracy of diagnosis. This pilot study was conducted to assess the affinity and selectivity of BerEp4 antibody and assess its possible use in designing theranostic probes for BCC. We provide evidence that our photon-counting fluorescence macrodetection system can recover specific signal increases from a film/pellet phantom. Additionally, we show that a two-photon excited fluorescence /backscatter confocal microscopy system can image BerEP4 antibody/antigen complex on the surface of BerEP4-expressing cancer cells in three dimensions. Based on the initial results, BerEP4 seems to be a promising biomarker for molecular imaging of BCC. To prepare BerEP4 for eventual theranostic use, we examined the feasibility of a combined macro-/micro-optical approach to imaging BCC with various histologies. These optical methods, endowed with the ability to monitor treatment in real time, may open an opportunity for noninvasive diagnosis, treatments, and follow-up.

Prefrontal cortex hemodynamics and age: a pilot study using functional near infrared spectroscopy in children

Cerebral hemodynamics reflect cognitive processes and underlying physiological processes, both of which are captured by functional near infrared spectroscopy (fNIRS). Here, we introduce a novel parameter of Oxygenation Variability directly obtained from fNIRS data —the OV Index—and we demonstrate its use in children. fNIRS data were collected from 17 children (ages 4–8 years), while they performed a standard Go/No-Go task. Data were analyzed using two frequency bands—the first attributed to cerebral autoregulation (CA) (<0.1 Hz) and the second to respiration (0.2–0.3 Hz). Results indicate differences in variability of oscillations of oxygen saturation (SO₂) between the two different bands. These pilot data reveal a dynamic relationship between chronological age and OV index in CA associated frequency of <0.1 Hz. Specifically, OV index increased with age between 4 and 6 years. In addition, there was much higher variability in frequencies associated with CA than for respiration across subjects. These findings provide preliminary evidence for the utility of the OV index and are the first to describe the relationship between cerebral autoregulation and age in children using fNIRS methodology.

In vivo fluorescence lifetime imaging for monitoring the efficacy of the cancer treatment

PURPOSE

Advances in tumor biology created a foundation for targeted therapy aimed at inactivation of specific molecular mechanisms responsible for cell malignancy. In this paper, we used in vivo fluorescence lifetime imaging with HER2-targeted fluorescent probes as an alternative imaging method to investigate the efficacy of targeted therapy with 17-DMAG (an HSP90 inhibitor) on tumors with high expression of HER2 receptors.

EXPERIMENTAL DESIGN

HER2-specific Affibody, conjugated to Alexafluor 750, was injected into nude mice bearing HER2-positive tumor xenograft. The fluorescence lifetime was measured before treatment and monitored after the probe injections at 12 hours after the last treatment dose, when the response to the 17-DMAG therapy was the most pronounced as well as a week after the last treatment when the tumors grew back almost to their pretreatment size.

RESULTS

Imaging results showed significant difference between the fluorescence lifetimes at the tumor and the contralateral site (∼0.13 ns) in the control group (before treatment) and 7 days after the last treatment when the tumors grew back to their pretreatment dimensions. However, at the time frame that the treatment had its maximum effect (12 hours after the last treatment), the difference between the fluorescence lifetime at the tumor and contralateral site decreased to 0.03 ns.

CONCLUSIONS

The results showed a good correlation between fluorescence lifetime and the efficacy of the treatment. These findings show that in vivo fluorescence lifetime imaging can be used as a promising molecular imaging tool for monitoring the treatment outcome in preclinical models and potentially in patients.

Evaluation of non-invasive multispectral imaging as a tool for measuring the effect of systemic therapy in Kaposi sarcoma

Diffuse multi-spectral imaging has been evaluated as a potential non-invasive marker of tumor response. Multi-spectral images of Kaposi sarcoma skin lesions were taken over the course of treatment, and blood volume and oxygenation concentration maps were obtained through principal component analysis (PCA) of the data. These images were compared with clinical and pathological responses determined by conventional means. We demonstrate that cutaneous lesions have increased blood volume concentration and that changes in this parameter are a reliable indicator of treatment efficacy, differentiating responders and non-responders. Blood volume decreased by at least 20% in all lesions that responded by clinical criteria and increased in the two lesions that did not respond clinically. Responses as assessed by multi-spectral imaging also generally correlated with overall patient clinical response assessment, were often detectable earlier in the course of therapy, and are less subject to observer variability than conventional clinical assessment. Tissue oxygenation was more variable, with lesions often showing decreased oxygenation in the center surrounded by a zone of increased oxygenation. This technique could potentially be a clinically useful supplement to existing response assessment in KS, providing an early, quantitative, and non-invasive marker of treatment effect.

In vivo assessment of HER2 receptor density in HER2-positive tumors by near-infrared imaging, using repeated injections of the fluorescent probe

HER2 overexpression and amplification of the HER2/neu gene have been found in approximately 25% of invasive breast carcinomas. They are associated with a poor prognosis and resistance to therapy in breast cancer patients. Up to now, clinical evaluation of human epidermal growth factor receptor 2 (HER2) expression is based on ex vivo methods (immunohistochemistry (IHC) or fluorescence in situ hybridization (FISH) staining of biopsied tissue). Our goal is to realize “image and treat” paradigm using targeted fluorescent probes to evaluate expression levels of cell biomarkers responsible for cancer progression and to monitor the efficacy of corresponding monoclonal antibody treatments. We used fluorescent Affibody-based probes for in vivo analysis of HER2 receptors using near-infrared optical imaging that do not interfere with binding of the therapeutic agents to these receptors. We have analyzed two types of breast carcinoma xenografts with significant differences in HER2 expression (3+ and 2+ according to classification) in the mouse model. Using our kinetic model to analyze the temporal variations of the fluorescence intensity in the tumor area after two subsequent injections allowed us to assess quantitatively the difference in HER2 expression levels for two tumor types (BT-474 and MD-MBA-361). This result was substantiated by ELISA ex vivo assays of HER2 expression in the same tumors.

Biophotonics techniques for structural and functional imaging, in vivo

In vivo optical imaging is being conducted in a variety of medical applications, including optical breast cancer imaging, functional brain imaging, endoscopy, exercise medicine, and monitoring the photodynamic therapy and progress of neoadjuvant chemotherapy. In the past three decades, in vivo diffuse optical breast cancer imaging has shown promising results in cancer detection, and monitoring the progress of neoadjuvant chemotherapy. The use of near infrared spectroscopy for functional brain imaging has been growing rapidly. In fluorescence imaging, the difference between autofluorescence of cancer lesions compared to normal tissues were used in endoscopy to distinguish malignant lesions from normal tissue or inflammation and in determining the boarders of cancer lesions in surgery. Recent advances in drugs targeting specific tumor receptors, such as monoclonal antibodies (mAb), has created a new demand for developing non-invasive in vivo imaging techniques for detection of cancer biomarkers, and for monitoring their down regulations during therapy. Targeted treatments, combined with new imaging techniques, are expected to potentially result in new imaging and treatment paradigms in cancer therapy. Similar approaches can potentially be applied for the characterization of other disease-related biomarkers. In this chapter, we provide a review of diffuse optical and fluorescence imaging techniques with their application in functional brain imaging and cancer diagnosis.

Affibody-DyLight conjugates for in vivo assessment of HER2 expression by near-infrared optical imaging

Purpose

Amplification of the HER2/neu gene and/or overexpression of the corresponding protein have been identified in approximately 20% of invasive breast carcinomas. Assessment of HER2 expression in vivo would advance development of new HER2-targeted therapeutic agents and, potentially, facilitate choice of the proper treatment strategy offered to the individual patient. We present novel HER2-specific probes for in vivo evaluation of the receptor status by near-infrared (NIR) optical imaging.

Experimental Design

Affibody molecules were expressed, purified, and labeled with NIR-fluorescent dyes. The binding affinity and specificity of the obtained probe were tested in vitro. For in vivo validation, the relationship of the measured NIR signal and HER2 expression was characterized in four breast cancer xenograft models, expressing different levels of HER2. Accumulation of Affibody molecules in tumor tissue was further confirmed by ex vivo analysis.

Results

Affibody-DyLight conjugates showed high affinity to HER2 (K_D = 3.66±0.26). No acute toxicity resulted from injection of the probes (up to 0.5 mg/kg) into mice. Pharmacokinetic studies revealed a relatively short (37.53±2.8 min) half-life of the tracer in blood. Fluorescence accumulation in HER2-positive BT-474 xenografts was evident as soon as a few minutes post injection and reached its maximum at 90 minutes. On the other hand, no signal retention was observed in HER2-negative MDA-MB-468 xenografts. Immunostaining of extracted tumor tissue confirmed penetration of the tracer into tumor tissue.

Conclusions

The results of our studies suggest that Affibody-DyLight-750 conjugate is a powerful tool to monitor HER2 status in a preclinical setting. Following clinical validation, it might provide complementary means for assessment of HER2 expression in breast cancer patients (assuming availability of proper NIR scanners) and/or be used to facilitate detection of HER2-positive metastatic lesions during NIR-assisted surgery.

In vivo method to monitor changes in HER2 expression using near-infrared fluorescence imaging

Human epidermal growth factor receptor type 2 (HER2) is a well-known biomarker that is overexpressed in many breast carcinomas. HER2 expression level is an important factor to optimize the therapeutic strategy and monitor the treatment. We used albumin binding domain-fused HER2-specific Affibody molecules, labeled with Alexa Fluor750 dye, to characterize HER2 expression in vivo. Near-infrared optical imaging studies were carried out using mice with subcutaneous HER2-positive tumors. Animals were divided into groups of five: no treatment and 12 hours and 1 week after treatment of the tumors with the Hsp90 inhibitor 17-dimethylaminoethylamino-17-demethoxygeldanamycin (17-DMAG). The compartmental ligands-receptor model, describing binding kinetics, was used to evaluate HER2 expression from the time sequence of the fluorescence images after the intravenous probe injection. The normalized rate of accumulation of the specific fluorescent biomarkers, estimated from this time sequence, linearly correlates with the conventional ex vivo enzyme-linked immunosorbent assay (ELISA) readings for the same tumor. Such correspondence makes properly arranged fluorescence imaging an excellent candidate for estimating HER2 overexpression in tumors, complementing ELISA and other ex vivo assays. Application of this method to the fluorescence data from HER2-positive xenografts reveals that the 17-DMAG treatment results in downregulation of HER2. Application of the AngioSense 750 probe confirmed the antiangiogenic effect of 17-DMAG found with Affibody-Alexa Fluor 750 conjugate.

Biophotonics techniques for structural and functional imaging, in vivo

In vivo optical imaging is being conducted in a variety of medical applications, including optical breast cancer imaging, functional brain imaging, endoscopy, exercise medicine, and monitoring the photodynamic therapy and progress of neoadjuvant chemotherapy. In the past three decades, in vivo diffuse optical breast cancer imaging has shown promising results in cancer detection, and monitoring the progress of neoadjuvant chemotherapy. The use of near infrared spectroscopy for functional brain imaging has been growing rapidly. In fluorescence imaging, the difference between autofluorescence of cancer lesions compared to normal tissues were used in endoscopy to distinguish malignant lesions from normal tissue or inflammation and in determining the boarders of cancer lesions in surgery. Recent advances in drugs targeting specific tumor receptors, such as AntiBodies (MAB), has created a new demand for developing non-invasive in vivo imaging techniques for detection of cancer biomarkers, and for monitoring their down regulations during therapy. Targeted treatments, combined with new imaging techniques, are expected to potentially result in new imaging and treatment paradigms in cancer therapy. Similar approaches can potentially be applied for the characterization of other disease-related biomarkers. In this chapter, we provide a review of diffuse optical and fluorescence imaging techniques with their application in functional brain imaging and cancer diagnosis.

Using in-vivo fluorescence imaging in personalized cancer diagnostics and therapy, an image and treat paradigm

The major goal in developing drugs targeting specific tumor receptors, such as Monoclonal AntiBodies (MAB), is to make a drug compound that targets selectively the cancer-causing biomarkers, inhibits their functionality, and/or delivers the toxin specifically to the malignant cells. Recent advances in MABs show that their efficacy depends strongly on characterization of tumor biomarkers. Therefore, one of the main tasks in cancer diagnostics and treatment is to develop non-invasive in-vivo imaging techniques for detection of cancer biomarkers and monitoring their down regulation during the treatment. Such methods can potentially result in a new imaging and treatment paradigm for cancer therapy. In this article we have reviewed fluorescence imaging approaches, including those developed in our group, to detect and monitor Human Epidermal Growth Factor 2 (HER2) receptors before and during therapy. Transition of these techniques from the bench to bedside is the ultimate goal of our project. Similar approaches can be used potentially for characterization of other cancer related cell biomarkers.

A hematoma detector-a practical application of instrumental motion as signal in near infra-red imaging

In this paper we discuss results based on using instrumental motion as a signal rather than treating it as noise in Near Infra-Red (NIR) imaging. As a practical application to demonstrate this approach we show the design of a novel NIR hematoma detection device. The proposed device is based on a simplified single source configuration with a dual separation detector array and uses motion as a signal for detecting changes in blood volume in the dural regions of the head. The rapid triage of hematomas in the emergency room will lead to improved use of more sophisticated/expensive imaging facilities such as CT/MRI units. We present simulation results demonstrating the viability of such a device and initial phantom results from a proof of principle device. The results demonstrate excellent localization of inclusions as well as good quantitative comparisons.

Abstract 5298: Affibody – NIR conjugate for optical imaging of HER2-expressing tumors

Amplification of the HER2/neu gene and/or overexpression of the protein have been identified in approximately 20% of invasive breast carcinoma, Particularly in breast cancer, elevated HER2 status is associated with increased proliferation and survival of cancer cells and thus contributes to poor therapy outcomes and unfavorable prognosis.

Affibody molecules are unique class of artificial ligands. They are relatively small, (∼7-kDa), affinity proteins, structurally based on a 58-amino-acid scaffold derived from the Z domain of the Staphylococcus aureus- protein, and were obtained by combinatorial protein engineering.

Optical imaging is a powerful tool allowing non-invasive in vivo analysis of macroscopic distribution of fluorescent labels. Introduction of Near-Infrared fluorescent beacons significantly improved the light penetration making the Over the past several years, there has been an explosion of reports describing successful in vivo NIR fluorescence imaging using antibodies or antibodies fragment or small molecules as contrast agents.

Here we report the construction, in vitro and in vivo evaluation of a new Affibody based probe for Near Infrared imaging of HER2-positive tumors.

Unique, C-terminal cysteine residue of HER2-Affibody molecules were modified with maleimide derivatives of optical beacons. The conjugates maintained high affinity to HER2 receptors with estimated KD value 3.66 ±0.26 nM using HER2 positive BT474 cells. Competition assay showed slight affinity reduction due to labeling (IC50=24.1 nM at 50nM labeled Affibody). No dye accumulation was observed for “non-specific” Affibody molecules (raised against Taq polymerase). HER2-Affibody binding was well correlated with receptor expression in five different cell lines as determined by FACS and HER2 Elisa respectively. Receptor specificity was also confirmed by immunofluorescence imaging: Cells with high HER2 level (SKBR3) showed almost exclusive membrane retention of the probe even after long period of incubation. Neither membrane retention nor intracellular uptake of the probe was observed for HER2-negative MDA MB-468 cells.

In vivo characteristic of the probe was performed in mice subcutaneous tumor models using NIR fluorescence small-animal imager. The probe showed relatively fast clearance rate from the circulation after intravenous administration (T1/2=31.8±10.42 min). The highest accumulation was recorded for BT474 tumors 90 min post probe administration. No signal was detected in tumors injected with HER2-nonspecyfic probe or for HER2 negative tumors receiving HER2-Affibody. Interestingly, accumulation rate better correlated with HER2 expression level in the tumor than maximum uptake.

HER2-dependend probe accumulation was confirmed also by IHC analysis.

Our results suggest that optical imaging using Affibody-based probes, may become a noninvasive alternative tool for assessment of HER2 expression in breast tumors.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5298. doi:10.1158/1538-7445.AM2011-5298

Target detection and quantification using a hybrid hand-held diffuse optical tomography and photoacoustic tomography system

We present a photoacoustic tomography-guided diffuse optical tomography approach using a hand-held probe for detection and characterization of deeply-seated targets embedded in a turbid medium. Diffuse optical tomography guided by coregistered ultrasound, MRI, and x ray has demonstrated a great clinical potential to overcome lesion location uncertainty and to improve light quantification accuracy. However, due to the different contrast mechanisms, some lesions may not be detectable by a nonoptical modality but yet have high optical contrast. Photoacoustic tomography utilizes a short-pulsed laser beam to diffusively penetrate into tissue. Upon absorption of the light by the target, photoacoustic waves are generated and used to reconstruct, at ultrasound resolution, the optical absorption distribution that reveals optical contrast. However, the robustness of optical property quantification of targets by photoacoustic tomography is complicated because of the wide range of ultrasound transducer sensitivity, the orientation and shape of the targets relative to the ultrasound array, and the uniformity of the laser beam. We show in this paper that the relative optical absorption map provided by photoacoustic tomography can potentially guide the diffuse optical tomography to accurately reconstruct target absorption maps.

Artifact reduction method in ultrasound-guided diffuse optical tomography using exogenous contrast agents

In diffuse optical tomography (DOT), a typical perturbation approach requires two sets of measurements obtained at the lesion breast (lesion or target site) and a contra-lateral location of the normal breast (reference site) for image reconstruction. For patients who have a small amount of breast tissue, the chest-wall underneath the breast tissue at both sites affects the imaging results. In this group of patients, the perturbation, which is the difference between measurements obtained at the lesion and reference sites, may include the information of background mismatch which can generate artifacts or affect the reconstructed quantitative absorption coefficient of the lesion. Also, for patients who have a single breast due to prior surgery, the contra-lateral reference is not available. To improve the DOT performance or overcome its limitation, we introduced a new method based on an exogenous contrast agent and demonstrate its performance using animal models. Co-registered ultrasound was used to guide the lesion localization. The results have shown that artifacts caused by background mismatch can be reduced significantly by using this new method.

Target detection and quantification using a hybrid hand-held diffuse optical tomography and photoacoustic tomography system

We present a photoacoustic tomography-guided diffuse optical tomography approach using a hand-held probe for detection and characterization of deeply-seated targets embedded in a turbid medium. Diffuse optical tomography guided by coregistered ultrasound, MRI, and x ray has demonstrated a great clinical potential to overcome lesion location uncertainty and to improve light quantification accuracy. However, due to the different contrast mechanisms, some lesions may not be detectable by a nonoptical modality but yet have high optical contrast. Photoacoustic tomography utilizes a short-pulsed laser beam to diffusively penetrate into tissue. Upon absorption of the light by the target, photoacoustic waves are generated and used to reconstruct, at ultrasound resolution, the optical absorption distribution that reveals optical contrast. However, the robustness of optical property quantification of targets by photoacoustic tomography is complicated because of the wide range of ultrasound transducer sensitivity, the orientation and shape of the targets relative to the ultrasound array, and the uniformity of the laser beam. We show in this paper that the relative optical absorption map provided by photoacoustic tomography can potentially guide the diffuse optical tomography to accurately reconstruct target absorption maps.

Potential role of coregistered photoacoustic and ultrasound imaging in ovarian cancer detection and characterization

Currently, there is no adequate technology to detect early stage ovarian cancers. Most of the cancers in the ovary are detected when the cancer has already metastasized to other parts of the body. As a result, ovarian cancer has the highest mortality of all gynecologic cancers with a 5-year survival rate of 30% or less. Thus, there is an urgent need to improve the current diagnostic techniques. Photoacoustic imaging (PAI) is an emerging modality with a great potential to assist ultrasound for detecting ovarian cancer noninvasively. In this article, we report the first study of coregistered ultrasound and PAI of 33 ex vivo human ovaries. An assessment of the photoacoustic images has revealed light absorption distribution in the ovary, which is directly related to the vasculature distribution and amount. Quantification of the light absorption levels in the ovary has indicated that, in the postmenopausal group, malignant ovaries showed significantly higher light absorption than normal ones (P = .0237). For these two groups, we have obtained a sensitivity of 83% and a specificity of 83%. This result suggests that PAI is a promising modality for improving ultrasound diagnosis of ovarian cancer.

Optical tomography method that accounts for tilted chest wall in breast imaging

The chest wall underneath breast tissue distorts light reflection measurements, especially measurements obtained from distant source-detector pairs. For patients with a chest wall located at a shallower depth, the chest-wall effect needs to be considered in the image reconstruction procedure. Following our previous studies, this work systemically evaluates the performance of a two-layer model-based reconstruction using the finite element method, and compares it with the performance of the semi-infinite model. The results obtained from simulations and phantom experiments show that the two-layer model improves the light quantification of the targets. The improvements are attributed to improved background estimation and more accurate weight matrix calculation using a two-layer model compared to the semi-infinite model. Fitted two-layer background optical properties obtained from a group of ten patients with chest walls located less than 2 cm deep are more representative of breast tissue and chest-wall optical properties.

Early-stage invasive breast cancers: potential role of optical tomography with US localization in assisting diagnosis

PURPOSE

To investigate the potential role of optical tomography in the near-infrared (NIR) spectrum with ultrasonographic (US) localization as a means of differentiating early-stage cancers from benign lesions of the breast.

MATERIALS AND METHODS

The protocol was approved by the institutional review boards and was HIPAA compliant; all participants signed an informed consent. One hundred seventy-eight consecutive women (mean age, 52 years; range, 21-89 years) who underwent US-guided biopsy were imaged with a hand-held probe consisting of a coregistered US transducer and an NIR imager. The lesion location provided by coregistered US was used to guide optical imaging. Light absorption was measured at two optical wavelengths. From this measurement, tumor angiogenesis was assessed on the basis of calculated total hemoglobin concentration (tHb) and was correlated with core biopsy results. For patients diagnosed with carcinomas and followed up with subsequent excision, the tHb was correlated with pathologic parameters.

RESULTS

There were two in situ carcinomas (Tis), 35 T1 carcinomas, 24 T2-T4 carcinomas, and 114 benign lesions. The mean maximum and mean average tHb of the Tis-T1 group were 102.0 micromol/L +/- 28.5 (standard deviation) and 71.9 micromol/L +/- 18.8, and those of the T2-T4 group were 100.3 micromol/L +/- 26.4 and 67.0 micromol/L +/- 18.3, respectively. The mean maximum and mean average tHb of the benign group were 55.1 micromol/L +/- 22.7 and 39.1 micromol/L +/- 14.9, respectively. Both mean maximum and mean average tHb levels were significantly higher in the malignant groups than they were in the benign group (P < .001). The sensitivity, specificity, positive predictive value, and negative predictive value for Tis-T1 cancers were 92%, 93%, 81%, and 97%. The corresponding values for T2-T4 tumors were 75%, 93%, 69%, and 95%.

CONCLUSION

The angiogenesis (tHb) contrast imaged by using the NIR technique with US holds promise as an adjunct to mammography and US for distinguishing early-stage invasive breast cancers from benign lesions.

Effect of the chest wall on breast lesion reconstruction

The chest wall underneath the breast tissue affects near-infrared (NIR) diffusive waves measured with reflection geometry. With the assistance of a co-registered ultrasound, the depth and the tilting angle of the chest wall can be determined and are used to model the breast as a two-layer medium. Finite element method (FEM) is suitable for modeling complex boundary conditions and is adapted to model the breast tissue and chest wall. Four parameters of bulk absorption and reduced scattering coefficients of these two layers are estimated and used for imaging reconstruction. Using a two-layer model, we have systematically investigated the effect of the chest wall on breast lesion reconstruction. Results have shown that chest-wall depth, titling angle, and difference between optical properties of two layers of lesion and reference sites affect the lesion reconstruction differently. Our analysis will be valuable and informative to researchers who are using reflectance geometry for breast imaging. The analysis can also provide guidelines for imaging operators to minimize image artifacts and to produce the best reconstruction results.

Tumor angiogenesis imaged by optical tomography can accurately diagnose early-stage invasive breast cancers

Abstract #52

Background: Our initial clinical results obtained from a novel ultrasound(US)-guided diffusive-wave optical tomography have shown that early-stage invasive breast cancers may be distinguished from benign lesions with an average of two-fold angiogenesis contrast. However, breast cancer is a heterogeneous disease with different growth and metabolic rates that result in a wide range of functional differences. In this report, we present a spectrum of breast lesion angiogenesis distributions from benign lesions, early-stage invasive cancers to advanced cancers. The objective is to investigate the feasibility of optical tomography with US localization in differentiating malignant from benign breast masses.&#x2028; Materials and Methods: 123 patients underwent US-guided biopsy and were imaged with a combined imager consisting of a commercially available US system and a near infrared (NIR) imager. A hand-held probe with a centrally located US transducer and NIR sensors surrounding it was used to simultaneously acquire co-registered US images and optical data. The lesion location provided by US was used to guide optical imaging reconstruction. Light absorption was measured at multiple wavelengths. From this, tumor angiogenesis was assessed based on calculated total hemoglobin concentration.&#x2028; Results: There were 23 stage I carcinomas, 21 stage II to IIII carcinomas, and 112 benign lesions. The mean maximum and average values of total hemoglobin concentration (tHb) of the stage I malignant group were 102.0 μ mol/liter (±30.7) and 72.3 μ mol/liter ( ±18.1), and the values of the state II to IIII malignant group were 114.4 μ mol/liter (±38.4) and 75.4 μ mol/liter (±25.2), respectively. The mean maximum and average values of the benign group were 54.0 μ mol/liter (±22.3) and 38.2 μ mol/liter (±14.8), respectively. Both maximum and average of tHb level were statistically significantly higher in the malignant groups than the benign group (P&lt;0.01). An example of a six mm stage I cancer imaged by US (Fig.1(a)) and the NIR imager (Fig.1(b) is given in Figure 1.&#x2028; &#x2028; The detection sensitivity and specificity of the stage I cancer group were 91% and 94%, and 76% and 94% for the stage II to IIII cancer group.&#x2028; Discussion: The tumor angiogenesis distributions are complex and the angiogenesis contrast holds great promise for distinguishing early-stage invasive breast cancers from benign lesions. For advanced cancers, the angiogenesis distribution is heterogeneous and often presents periphery enhancement and/or shadow effect which can be used to assist US diagnosis.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 52.

Image reconstruction method for a two-layer tissue structure accounts for chest-wall effects in breast imaging

We develop a new tomographic imaging reconstruction algorithm for a two-layer tissue structure. Simulations and phantom experiments show more accurate reconstruction of target optical properties compared with those results obtained from a semi-infinite tissue model for layered structures. This improvement is mainly attributed to the more accurate estimation of background optical properties and more accurate estimation of weight matrix for imaging reconstruction by considering the light propagation effect in the second layer. Clinical results of breast lesions are also presented to demonstrate the utility of this new imaging algorithm.