Diffuse optical tomography has shown promising results as a tool for breast cancer screening and monitoring response to chemotherapy. Dynamic imaging of the transient response of the breast to an external stimulus, such as pressure or a respiratory maneuver, can provide additional information that can be used to detect tumors. We present a new digital continuous-wave optical tomography system designed to simultaneously image both breasts at fast frame rates and with a large number of sources and detectors. The system uses a master-slave digital signal processor-based detection architecture to achieve a dynamic range of 160 dB and a frame rate of 1.7 Hz with 32 sources, 64 detectors, and 4 wavelengths per breast. Included is a preliminary study of one healthy patient and two breast cancer patients showing the ability to identify an invasive carcinoma based on the hemodynamic response to a breath hold.
Continuous wave optical tomography is non-ionizing, uses endogenous contrast, and can be performed quickly and at
low cost which makes it a suitable imaging modality for breast cancer screening. Using multiple wavelengths of light to
illuminate the breast at various angles, three-dimensional images of the distribution of chromophores such as oxy- and
deoxy-hemoglobin can help identify cancerous tissue. Dynamic optical imaging can provide additional insight into
cancer characteristics such as angiogenesis and metabolism. Here we present the first clinical data acquired with our
novel digital breast imaging system. This system is based upon a Digital Signal Processor (DSP) architecture that
leverages the immediate digitization of acquired analog data to reduce noise and quickly process large amounts of data.
Employing this new instrument we have investigated the dynamic changes due to a breath hold and its potential for use
in breast cancer screening. Over the course of a breath hold, images have been collected simultaneously from both
breasts at a rate of 1.7 frames per second with 32 sources and 64 detectors per breast and four wavelengths of light at
765, 805, 827, and 905nm. Initial results involving one healthy volunteer and one breast cancer patient support the
potential use of dynamic imaging for breast cancer detection.
Breast cancer characteristics such as angiogenesis and hypoxia can be quantified by using optical
tomography imaging to observe the hemodynamic response to an external stimulus. A digital near-infrared
tomography system has been developed specifically for the purpose of dynamic breast imaging. It
simultaneously acquires four frequency encoded wavelengths of light at 765, 808, 827, and 905nm in order
to facilitate the functional imaging of oxy- and deoxy-hemoglobin, lipid concentration and water content.
The system uses 32 source fibers to simultaneously illuminate both breasts. There are 128 detector fibers,
64 fibers for each breast, which deliver the detected light to silicon photo-detectors. The signal is
conditioned by variable gain amplifiers and filters and is quantized by an analog to digital converter
(ADC). The sampled signal is then passed on for processing using a Digital Signal Processor (DSP) prior
to display on a host computer. The system can acquire 2.23 frames per second with a dynamic range of
For much of the past decade, we have developed most of the essential hardware and software components needed for
practical implementation of dynamic NIRS imaging. Until recently, however, these efforts have been hampered by the
lack of calibrating phantoms whose dynamics substantially mimic those seen in tissue. Here we present findings that
document the performance of a dynamic phantom based on use of twisted nematic liquid crystal (LC) technology.
Programmable time courses of applied voltage cause the opacity of the LC devices, which are embedded in a background
matrix consisting of polysiloxane (silicone) admixed with scattering and absorbing materials, to vary in a manner that
mimics the spatiotemporal hemodynamic pattern of interest. Methods for producing phantoms with selected absorption
and scattering, internal heterogeneity, external geometry, hardness, and number and locations of embedded LCs are
described. Also described is a method for overcoming the apparent limitation that arises from LCs being mainly
independent of the illumination wavelength. The results presented demonstrate that: the opacity vs. voltage response of
LCs are highly stable and repeatable; the dynamic phantom can be driven at physiologically relevant speeds, and will
produce time-varying absorption that follows the programmed behavior with high fidelity; image time series recovered
from measurements on the phantom have high temporal and spatial location accuracy. Thus the dynamic phantom can
fill the need for test media that practitioners may use to confirm the accuracy of computed imaging results, assure the
correct operation of imaging hardware, and compare performance of different data analysis algorithms.