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

Development of a digital breast phantom for photoacoustic computed tomography

Photoacoustic (PA) imaging provides morphological and functional information about angiogenesis and thus is potentially suitable for breast cancer diagnosis. However, the development of PA breast imaging has been hindered by inadequate patients and a lack of ground truth images. Here, we report a digital breast phantom with realistic acoustic and optical properties, with which a digital PA-ultrasound imaging pipeline is developed to create a diverse pool of virtual patients with three types of masses: ductal carcinoma in situ, invasive breast cancer, and fibroadenoma. The experimental results demonstrate that our model is realistic, flexible, and can be potentially useful for accelerating the development of PA breast imaging technology.

Hybrid time-domain and continuous-wave diffuse optical tomography instrument with concurrent, clinical magnetic resonance imaging for breast cancer imaging

Diffuse optical tomography has demonstrated significant potential for clinical utility in the diagnosis and prognosis of breast cancer, and its use in combination with other structural imaging modalities improves lesion localization and the quantification of functional tissue properties. Here, we introduce a hybrid diffuse optical imaging system that operates concurrently with magnetic resonance imaging (MRI) in the imaging suite, utilizing commercially available MR surface coils. The instrument acquires both continuous-wave and time-domain diffuse optical data in the parallel-plate geometry, permitting both absolute assignment of tissue optical properties and three-dimensional tomography; moreover, the instrument is designed to incorporate diffuse correlation spectroscopic measurements for probing tissue blood flow. The instrument is described in detail here. Image reconstructions of a tissue phantom are presented as an initial indicator of the system's ability to accurately reconstruct optical properties and the concrete benefits of the spatial constraints provided by concurrent MRI. Last, we briefly discuss how various data combinations that the instrument could facilitate, including tissue perfusion, can enable more comprehensive assessment of lesion physiology.

Clinical optoacoustic imaging combined with ultrasound for coregistered functional and anatomical mapping of breast tumors

Optoacoustic imaging, based on the differences in optical contrast of blood hemoglobin and oxyhemoglobin, is uniquely suited for the detection of breast vasculature and tumor microvasculature with the inherent capability to differentiate hypoxic from the normally oxygenated tissue. We describe technological details of the clinical ultrasound (US) system with optoacoustic (OA) imaging capabilities developed specifically for diagnostic imaging of breast cancer. The combined OA/US system provides co-registered and fused images of breast morphology based upon gray scale US with the functional parameters of total hemoglobin and blood oxygen saturation in the tumor angiogenesis related microvasculature based upon OA images. The system component that enabled clinical utility of functional OA imaging is the hand-held probe that utilizes a linear array of ultrasonic transducers sensitive within an ultrawide-band of acoustic frequencies from 0.1 MHz to 12 MHz when loaded to the high-impedance input of the low-noise analog preamplifier. The fiberoptic light delivery system integrated into a dual modality probe through a patented design allowed acquisition of OA images while minimizing typical artefacts associated with pulsed laser illumination of skin and the probe components in the US detection path. We report technical advances of the OA/US imaging system that enabled its demonstrated clinical viability. The prototype system performance was validated in well-defined tissue phantoms. Then a commercial prototype system named Imagio™ was produced and tested in a multicenter clinical trial termed PIONEER. We present examples of clinical images which demonstrate that the spatio-temporal co-registration of functional and anatomical images permit radiological assessment of the vascular pattern around tumors, microvascular density of tumors as well as the relative values of the total hemoglobin [tHb] and blood oxygen saturation [sO2] in tumors relative to adjacent normal breast tissues. The co-registration technology enables increased accuracy of radiologist assessment of malignancy by confirming, upgrading and/or downgrading US categorization of breast tumors according to Breast Imaging Reporting And Data System (BI-RADS). Microscopic histologic examinations on the biopsied tissue of the imaged tumors served as a gold standard in verifying the functional and anatomic interpretations of the OA/US image feature analysis.

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.

Mono- and multimodal registration of optical breast images

Optical breast imaging offers the possibility of noninvasive, low cost, and high sensitivity imaging of breast cancers. Poor spatial resolution and a lack of anatomical landmarks in optical images of the breast make interpretation difficult and motivate registration and fusion of these data with subsequent optical images and other breast imaging modalities. Methods used for registration and fusion of optical breast images are reviewed. Imaging concerns relevant to the registration problem are first highlighted, followed by a focus on both monomodal and multimodal registration of optical breast imaging. Where relevant, methods pertaining to other imaging modalities or imaged anatomies are presented. The multimodal registration discussion concerns digital x-ray mammography, ultrasound, magnetic resonance imaging, and positron emission tomography.

Role of optical spectroscopy using endogenous contrasts in clinical cancer diagnosis

Optical spectroscopy has been intensively studied for cancer management in the past two decades. This review paper first introduces the background of optical spectroscopy for cancer management, which includes the advantages of optical techniques compared to other established techniques, the principle of optical spectroscopy and the typical setup of instrumentation. Then the recent progress in optical spectroscopy for cancer diagnosis in the following organs is reviewed: the brain, breast, cervix, lung, stomach, colon, prostate and the skin. Reviewed papers were selected from the PubMed database with keywords combining the terms of individual optical spectroscopy techniques and cancers. The primary focus is on the in vivo applications of optical spectroscopy in clinical studies. Ex vivo studies are also included for some organs to highlight special applications or when there are few in vivo results in the literature. Practical considerations of applying optical spectroscopy in clinical settings such as the speed, cost, complexity of operation, accuracy and clinical value are discussed. A few commercially available clinical instruments that are based on optical spectroscopy techniques are presented. Finally several technical challenges and standard issues are discussed and firm conclusions are made.

In vivo quantitative imaging of normal and cancerous breast tissue using broadband diffuse optical tomography

PURPOSE

A NIR tomography system that combines frequency domain (FD) and continuous wave (CW) measurements was used to image normal and malignant breast tissues.

METHODS

FD acquisitions were confined to wavelengths less than 850 nm because of detector limitations, whereas light from longer wavelengths (up to 948 nm) was measured in CW mode with CCD-coupled spectrometer detection. The two data sets were combined and processed in a single spectrally constrained reconstruction to map concentrations of hemoglobin, water, and lipid, as well as scattering parameters in the breast.

RESULTS

Chromophore concentrations were imaged in the breasts of nine asymptomatic volunteers to evaluate their intrasubject and intersubject variability. Normal subject data showed physiologically expected trends. Images from three cancer patients indicate that the added CW data is critical to recovering the expected increases in water and decreases in lipid content within malignancies. Contrasts of 1.5 to twofold in hemoglobin and water values were found in cancers.

CONCLUSIONS

In vivo breast imaging with instrumentation that combines FD and CW NIR data acquisition in a single spectral reconstruction produces more accurate hemoglobin, water, and lipid results relative to FD data alone.

Automated coregistered imaging using a hand-held probe-based optical imager

Near-infrared optical imaging holds a promise as a noninvasive technology toward cancer diagnostics and other tissue imaging applications. In recent years, hand-held based imagers are of great interest toward the clinical translation of the technology. However hand-held imagers developed to date are typically designed to obtain surface images and not tomography information due to lack of coregistration facilities. Herein, a recently developed hand-held probe-based optical imager in our Optical Imaging Laboratory has been implemented with novel coregistration facilities toward real-time and tomographic imaging of tissue phantoms. Continuous-wave fluorescence-enhanced optical imaging studies were performed using an intensified charge coupled device camera based imaging system in order to demonstrate the feasibility of automated coregistered imaging of flat phantom surfaces, using a flexible probe that can also contour to curvatures. Three-dimensional fluorescence tomographic reconstructions were also demonstrated using coregistered frequency-domain measurements obtained using the hand-held based optical imager. It was also observed from preliminary studies on cubical phantoms that multiple coregistered scans differentiated deeper targets (approximately 3 cm) from artifacts that were not feasible from a single coregistered scan, demonstrating the possibility of improved target depth detectability in the future.

Diffuse optical tomography of the breast: preliminary findings of a new prototype and comparison with magnetic resonance imaging

This paper presents an evaluation of a prototype diffuse optical tomography (DOT) system. Seventeen women with 18 breast lesions (10 invasive carcinomas, 2 fibroadenomas, and 6 benign cysts; diameters 13-54 mm) were evaluated with DOT and magnetic resonance imaging (MRI). A substantial fraction of the original 36 recruited patients could not be examined using this prototype due to technical problems. A region of interest (ROI) was drawn at the lesion position as derived from MRI and at the mirror image site in the contralateral healthy breast. ROIs were assessed quantitatively and qualitatively by two observers independently in two separate readings. Intra- and interobserver agreements were calculated using kappa statistics (k) and intraclass correlation coefficients (ICCs). Discriminatory values for presence of malignancy were determined by receiver operating characteristic (ROC) analyses. Intraobserver agreements were excellent (k 0.88 and 0.88; ICC 0.978 and 0.987), interobserver agreements were good to excellent (k 0.77-0.95; ICC 0.96-0.98). Discriminatory values for presence of malignancy were 0.92-0.93 and 0.97-0.99 for quantitative and qualitative ROC analysis, respectively. This DOT system has the potential to discriminate malignant from benign breast tissue in a reproducible qualitative and quantitative manner. Important technical improvements are required before this technique is ready for clinical application.

Optical imaging of the breast

This review provides a summary of the current state of optical breast imaging and describes its potential future clinical applications in breast cancer imaging. Optical breast imaging is a novel imaging technique that uses near-infrared light to assess the optical properties of breast tissue. In optical breast imaging, two techniques can be distinguished, i.e. optical imaging without contrast agent, which only makes use of intrinsic tissue contrast, and optical imaging with a contrast agent, which uses exogenous fluorescent probes. In this review the basic concepts of optical breast imaging are described, clinical studies on optical imaging without contrast agent are summarized, an outline of preclinical animal studies on optical breast imaging with contrast agents is provided, and, finally, potential applications of optical breast imaging in clinical practice are addressed. Based on the present literature, diagnostic performance of optical breast imaging without contrast agent is expected to be insufficient for clinical application. Development of contrast agents that target specific molecular changes associated with breast cancer formation is the opportunity for clinical success of optical breast imaging.

New technologies for human cancer imaging

Despite technical advances in many areas of diagnostic radiology, the detection and imaging of human cancer remains poor. A meaningful impact on cancer screening, staging, and treatment is unlikely to occur until the tumor-to-background ratio improves by three to four orders of magnitude (ie, 10(3)- to 10(4)-fold), which in turn will require proportional improvements in sensitivity and contrast agent targeting. This review analyzes the physics and chemistry of cancer imaging and highlights the fundamental principles underlying the detection of malignant cells within a background of normal cells. The use of various contrast agents and radiotracers for cancer imaging is reviewed, as are the current limitations of ultrasound, x-ray imaging, magnetic resonance imaging (MRI), single-photon emission computed tomography, positron emission tomography (PET), and optical imaging. Innovative technologies are emerging that hold great promise for patients, such as positron emission mammography of the breast and spectroscopy-enhanced colonoscopy for cancer screening, hyperpolarization MRI and time-of-flight PET for staging, and ion beam-induced PET scanning and near-infrared fluorescence-guided surgery for cancer treatment. This review explores these emerging technologies and considers their potential impact on clinical care. Finally, those cancers that are currently difficult to image and quantify, such as ovarian cancer and acute leukemia, are discussed.

Comparison of diffuse optical tomography of human breast with whole-body and breast-only positron emission tomography

We acquire and compare three-dimensional tomographic breast images of three females with suspicious masses using diffuse optical tomography (DOT) and positron emission tomography (PET). Co-registration of DOT and PET images was facilitated by a mutual information maximization algorithm. We also compared DOT and whole-body PET images of 14 patients with breast abnormalities. Positive correlations were found between total hemoglobin concentration and tissue scattering measured by DOT, and fluorodeoxyglucose (18F-FDG) uptake. In light of these observations, we suggest potential benefits of combining both PET and DOT for characterization of breast lesions.

Diffuse optical imaging of the healthy and diseased breast: A systematic review

Screening X-ray mammography is limited by false positives and negatives leading to unnecessary physical and psychological morbidity. Diffuse Optical Imaging using harmless near infra red light, provides lesion detection based on functional abnormalities and represents a novel diagnostic arm that could complement traditional mammography. Reviews of optical breast imaging have not been systematic, are focused mainly on technological developments, and have become superseded by rapid technological advancement. The aim of this study is to review clinically orientated studies involving approximately 2,000 women in whom optical mammography has been used to evaluate the healthy or diseased breast. The results suggest that approximately 85% of breast lesions are detectable on optical mammography. Spectroscopic resolution of tissue haemoglobin composition and oxygen saturation may improve the detectability of breast diseases. Results suggest that breast lesions contain approximately twice the haemoglobin concentration of background tissue. Current evidence suggests that it is not possible to distinguish benign from malignant disease using optical imaging techniques in isolation. Methods to improve the performance of Diffuse Optical Imaging, such as better spectral coverage with additional wavelengths, improved modelling of light transport in tissues and the use of extrinsic dyes may augment lesion detection and characterisation. Future research should involve large clinical trials to determine the overall sensitivity and specificity of optical imaging techniques as well as to establish patient satisfaction and economic viability.

Advances in optical spectroscopy and imaging of breast lesions

A review is presented of recent advances in optical imaging and spectroscopy and the use of light for addressing breast cancer issues. Spectroscopic techniques offer the means to characterize tissue components and obtain functional information in real time. Three-dimensional optical imaging of the breast using various illumination and signal collection schemes in combination with image reconstruction algorithms may provide a new tool for cancer detection and treatment monitoring.