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

Department of Medical Physics and Bioengineering, University College London, London, WC1E 6BT, UK.
Applied Optics (Impact Factor: 1.78). 07/2007; 46(17):3628-38. DOI: 10.1364/AO.46.003628
Source: PubMed


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.

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    • "Optical imaging has been predicted to improve sensitivity and specificity in dense breast tissues, but this has not yet been well established. Most published optical studies focusing on lesion detection and characterization were performed in heterogeneous breast density populations [15-21]. Increased hemoglobin and water content, as well as decreased lipid content were observed in tumors compared to normal surrounding breast tissue. "
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    ABSTRACT: Radiographic density adversely affects the performance of x-ray mammography and can be particularly problematic in younger and high-risk women. Because of this limitation, there is signficant ongoing effort to develop alternative cancer screening and detection strategies for this population. This pilot study evaluates the potential of Diffuse Optical Spectroscopic Imaging (DOSI) to image known tumors in dense breast tissue. We performed a retrospective analysis on 24 radiographically dense breast cancer subjects measured with DOSI over a 4 year period (Bi-RADS category 3 and 4, average age = 39 +/- 7.6, average maximum size 31 +/- 17 mm). Two previously-described DOSI contrast functions, the tissue optical index (TOI), and the specific tumor component (STC), which are based upon the concentrations and spectral signatures of hemoglobin, water and lipids, respectively, were used to form 2D optical images of breast tumors. Using TOI and STC, 21 out of 24 breast tumors were found to be statistically different from the surrounding highly vascularized dense tissue and to be distinguishable from the areolar region. For these patients, the tumor to normal contrast was 2.6 +/- 1.2 (range 1.3 to 5.5) and 10.0 +/- 7.5 (range 3.3 to 26.4) for TOI and STC, respectively. STC images were particularly useful in eliminating metabolic background from the retroareolar region which led to identification of 2 out of 4 retroareolar tumors. Using both the abundance and the disposition of the tissue chromophores recovered from the DOSI measurements, we were able to observe tumor contrast relative to dense breast tissue. These preliminary results suggest that DOSI spectral characterization strategies may provide new information content that could help imaging breast tumors in radiographically dense tissue and in particular in the areolar complex.
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    • "Many groups have reported high total hemoglobin concentration in malignant tumors as compared to normal tissues - an expectable contrasting mechanism due to the sustained angiogenesis occurring in tumors [3,11,12]. Despite of unapparent manifestation in hemoglobin-DOT, some groups have observed a decrease of the oxygen saturation (StO2) in the tumor regions [12–14]. In addition, some researchers have described tumor-to-normal contrast in tissue scattering parameter, ascribed to morphologic changes at a cellular level as well as changes in size and density of subcellular organelles in tumors [15,16]. "
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    ABSTRACT: A combined time-domain fluorescence and hemoglobin diffuse optical tomography (DOT) system and the image reconstruction methods are proposed for enhancing the reliability of breast-dedicated optical measurement. The system equipped with two pulsed laser diodes at wavelengths of 780 nm and 830 nm that are specific to the peak excitation and emission of the FDA-approved ICG agent, and works with a 4-channel time-correlated single photon counting device to acquire the time-resolved distributions of the light re-emissions at 32 boundary sites of tissues in a tandem serial-to-parallel mode. The simultaneous reconstruction of the two optical (absorption and scattering) and two fluorescent (yield and lifetime) properties are achieved with the respective featured-data algorithms based on the generalized pulse spectrum technique. The performances of the methodology are experimentally assessed on breast-mimicking phantoms for hemoglobin- and fluorescence-DOT alone, as well as for fluorescence-guided hemoglobin-DOT. The results demonstrate the efficacy of improving the accuracy of hemoglobin-DOT based on a priori fluorescence localization.
    Full-text · Article · Feb 2013 · Biomedical Optics Express
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    • "For both the forward model computation and reconstruction, the imaging domain was discretized into a uniform grid having a spatial resolution of 0.25 cm in the plane and 0.1875 cm along the coordinate. The bulk opitcal parameters were set to cm and cm for both the breast and the outside region in the box, which can be physically realized by filling the box with intralipid that has optical characteristics close to breast tissue [46]. The measurements were generated with a spherical heterogeneity of radius 1 cm present at the position with the coordinate (5,8,3) cm. "
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    ABSTRACT: We present a method for noniterative maximum a posteriori (MAP) tomographic reconstruction which is based on the use of sparse matrix representations. Our approach is to precompute and store the inverse matrix required for MAP reconstruction. This approach has generally not been used in the past because the inverse matrix is typically large and fully populated (i.e., not sparse). In order to overcome this problem, we introduce two new ideas. The first idea is a novel theory for the lossy source coding of matrix transformations which we refer to as matrix source coding. This theory is based on a distortion metric that reflects the distortions produced in the final matrix-vector product, rather than the distortions in the coded matrix itself. The resulting algorithms are shown to require orthonormal transformations of both the measurement data and the matrix rows and columns before quantization and coding. The second idea is a method for efficiently storing and computing the required orthonormal transformations, which we call a sparse-matrix transform (SMT). The SMT is a generalization of the classical FFT in that it uses butterflies to compute an orthonormal transform; but unlike an FFT, the SMT uses the butterflies in an irregular pattern, and is numerically designed to best approximate the desired transforms. We demonstrate the potential of the noniterative MAP reconstruction with examples from optical tomography. The method requires offline computation to encode the inverse transform. However, once these offline computations are completed, the noniterative MAP algorithm is shown to reduce both storage and computation by well over two orders of magnitude, as compared to a linear iterative reconstruction methods.
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