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.
Highlights
Breast tumor diagnosis is widely regarded as one of the most applicable areas of diffuse optical tomography (DOT), which aims at reconstructing blood concentration and oxygenation images of the breast by spatially and spectrally resolving its tissue optical properties [1,2,3,4,5]
This endogenous-contrast-based imaging modality, referred to as hemoglobin-DOT, has potentials to compensate the limitations of the established modalities, such as X-ray mammography, ultrasound (US) and magnetic resonance imaging (MRI), in the safety, sensitivity and specificity, for screening young women under 35 years of age who have dense breasts [1,4,5], and allows for improved discrimination between malignant and benign lesions [3,5,6,7]
The two laser diode (LD)-wavelengths are chosen according to the peak excitation and emission wavelengths of Indocyanine Green (ICG) agent, respectively, as well as to be within the optical spectral range optimized for quantifying the tissue hemoglobin indexes
Summary
Breast tumor diagnosis is widely regarded as one of the most applicable areas of diffuse optical tomography (DOT), which aims at reconstructing blood concentration and oxygenation images of the breast by spatially and spectrally resolving its tissue optical properties [1,2,3,4,5]. It has been argued that, hemoglobin-DOT with no a priori information, termed standalone hemoglobin-DOT, does not have sufficient sensitivity for early lesion detection, and might be readily corrupted by the breast and its periphery structures, such as the blood vessels, glands, nipple, and chest wall etc., due in part to the moderate tumor-to-normal hemoglobin contrast of about 1.5-2.5 [3], as well as the limited quantitative accuracy and spatial resolution of the inversion [1] To overcome these intrinsic shortcomings, multi-modal approaches that incorporate the hemoglobin-DOT with other imaging techniques have been intensively investigated, where the feasible-region information provided by the other modalities is normally used to reasonably regularize the inverse problem of the hemoglobin-DOT. Advances in multi-modal approaches using standard imaging modality of considerably high spatial resolution have been made in three fronts: concurrent optical measurements with MRI [17,18], X-ray mammography [19], and US [20]
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