Although transmission-based x-ray imaging is the most commonly used imaging approach for breast cancer detection, it exhibits false negative rates higher than 15%. To improve cancer detection accuracy, x-ray coherent scatter computed tomography (CSCT) has been explored to potentially detect cancer with greater consistency. However, the 10-min scan duration of CSCT limits its possible clinical applications. The coded aperture coherent scatter spectral imaging (CACSSI) technique has been shown to reduce scan time through enabling single-angle imaging while providing high detection accuracy. Here, we use Monte Carlo simulations to test analytical optimization studies of the CACSSI technique, specifically for detecting cancer in ex vivo breast samples. An anthropomorphic breast tissue phantom was modeled, a CACSSI imaging system was virtually simulated to image the phantom, a diagnostic voxel classification algorithm was applied to all reconstructed voxels in the phantom, and receiver-operator characteristics analysis of the voxel classification was used to evaluate and characterize the imaging system for a range of parameters that have been optimized in a prior analytical study. The results indicate that CACSSI is able to identify the distribution of cancerous and healthy tissues (i.e., fibroglandular, adipose, or a mix of the two) in tissue samples with a cancerous voxel identification area-under-the-curve of 0.94 through a scan lasting less than 10 s per slice. These results show that coded aperture scatter imaging has the potential to provide scatter images that automatically differentiate cancerous and healthy tissue within ex vivo samples. Furthermore, the results indicate potential CACSSI imaging system configurations for implementation in subsequent imaging development studies.
This study intends to validate the sensitivity and specificity of coded aperture coherent scatter spectral imaging (CACSSI) by comparison to standard histological preparation and pathologic analysis methods used to differentiate normal and neoplastic breast tissues. A composite overlay of the CACSSI rendered image and pathologist interpreted stained sections validate the ability of CACSSI to differentiate normal and neoplastic breast structures ex-vivo. Via comparison to pathologist annotated slides, the CACSSI system may be further optimized to maximize sensitivity and specificity for differentiation of breast carcinomas.
It is known that conventional x-ray imaging provides a maximum contrast between cancerous and healthy fibroglandular breast tissues of 3% based on their linear x-ray attenuation coefficients at 17.5 keV, whereas coherent scatter signal provides a maximum contrast of 19% based on their differential coherent scatter cross sections. Therefore in order to exploit this potential contrast, we seek to evaluate the performance of a coded- aperture coherent scatter imaging system for breast cancer detection and investigate its accuracy using Monte Carlo simulations. In the simulations we modeled our experimental system, which consists of a raster-scanned pencil beam of x-rays, a bismuth-tin coded aperture mask comprised of a repeating slit pattern with 2-mm periodicity, and a linear-array of 128 detector pixels with 6.5-keV energy resolution. The breast tissue that was scanned comprised a 3-cm sample taken from a patient-based XCAT breast phantom containing a tomosynthesis- based realistic simulated lesion. The differential coherent scatter cross section was reconstructed at each pixel in the image using an iterative reconstruction algorithm. Each pixel in the reconstructed image was then classified as being either air or the type of breast tissue with which its normalized reconstructed differential coherent scatter cross section had the highest correlation coefficient.
Comparison of the final tissue classification results with the ground truth image showed that the coded aperture imaging technique has a cancerous pixel detection sensitivity (correct identification of cancerous pixels), specificity (correctly ruling out healthy pixels as not being cancer) and accuracy of 92.4%, 91.9% and 92.0%, respectively. Our Monte Carlo evaluation of our experimental coded aperture coherent scatter imaging system shows that it is able to exploit the greater contrast available from coherently scattered x-rays to increase the accuracy of detecting cancerous regions within the breast.
A scatter imaging technique for the differentiation of cancerous and healthy breast tissue in a heterogeneous sample is introduced in this work. Such a technique has potential utility in intraoperative margin assessment during lumpectomy procedures. In this work, we investigate the feasibility of the imaging method for tumor classification using Monte Carlo simulations and physical experiments. The coded aperture coherent scatter spectral imaging technique was used to reconstruct three-dimensional (3-D) images of breast tissue samples acquired through a single-position snapshot acquisition, without rotation as is required in coherent scatter computed tomography. We perform a quantitative assessment of the accuracy of the cancerous voxel classification using Monte Carlo simulations of the imaging system; describe our experimental implementation of coded aperture scatter imaging; show the reconstructed images of the breast tissue samples; and present segmentations of the 3-D images in order to identify the cancerous and healthy tissue in the samples. From the Monte Carlo simulations, we find that coded aperture scatter imaging is able to reconstruct images of the samples and identify the distribution of cancerous and healthy tissues (i.e., fibroglandular, adipose, or a mix of the two) inside them with a cancerous voxel identification sensitivity, specificity, and accuracy of 92.4%, 91.9%, and 92.0%, respectively. From the experimental results, we find that the technique is able to identify cancerous and healthy tissue samples and reconstruct differential coherent scatter cross sections that are highly correlated with those measured by other groups using x-ray diffraction. Coded aperture scatter imaging has the potential to provide scatter images that automatically differentiate cancerous and healthy tissue inside samples within a time on the order of a minute per slice.
A fast and accurate scatter imaging technique to differentiate cancerous and healthy breast tissue is introduced in this work. Such a technique would have wide-ranging clinical applications from intra-operative margin assessment to breast cancer screening. Coherent Scatter Computed Tomography (CSCT) has been shown to differentiate cancerous from healthy tissue, but the need to raster scan a pencil beam at a series of angles and slices in order to reconstruct 3D images makes it prohibitively time consuming. In this work we apply the coded aperture coherent scatter spectral imaging technique to reconstruct 3D images of breast tissue samples from experimental data taken without the rotation usually required in CSCT. We present our experimental implementation of coded aperture scatter imaging, the reconstructed images of the breast tissue samples and segmentations of the 3D images in order to identify the cancerous and healthy tissue inside of the samples. We find that coded aperture scatter imaging is able to reconstruct images of the samples and identify the distribution of cancerous and healthy tissues (i.e., fibroglandular, adipose, or a mix of the two) inside of them. Coded aperture scatter imaging has the potential to provide scatter images that automatically differentiate cancerous and healthy tissue inside of ex vivo samples within a time on the order of a minute.
Coherent scatter X-ray imaging is a technique that provides spatially-resolved information about the molecular structure of the material under investigation, yielding material-specific contrast that can aid medical diagnosis and inform treatment. In this study, we demonstrate a coherent-scatter imaging approach based on the use of coded apertures (known as coded aperture coherent scatter spectral imaging1, 2) that enables fast, dose-efficient, high-resolution scatter imaging of biologically-relevant materials. Specifically, we discuss how to optimize a coded aperture coherent scatter imaging system for a particular set of objects and materials, describe and characterize our experimental system, and use the system to demonstrate automated material detection in biological tissue.
Instead of having the entire breast removed (a mastectomy), breast cancer patients often receive a breast con- serving surgery (BCS) for removal of only the breast tumor. If post-surgery analysis reveals ta missed margin around the tumor tissue excised through the BCS procedure, the physician must often call the patient back for another surgery, which is both difficult and risky for the patient. If this “margin detection” could be performed during the BCS procedure itself, the surgical team could use the analysis to ensure that all tumor tissue was removed in a single surgery, thereby potentially reducing the number of call backs from breast cancer surgery. We describe here a potential technique to detect surgical tumor margins in breast cancer using x-ray coherent scatter imaging. In this study, we demonstrate the imaging ability of this technique using Monte Carlo simulations.
Coded apertures and energy resolving detectors may be used to improve the sampling efficiency of x-ray tomography and increase the physical diversity of x-ray phenomena measured. Coding and decompressive inference enable increased molecular specificity, reduced exposure and scan times. We outline a specific coded aperture x-ray coherent scatter imaging architecture that demonstrates the potential of such schemes. Based on this geometry, we develop a physical model using both a semi-analytic and Monte Carlo-based framework, devise an experimental realization of the system, describe a reconstruction algorithm for estimating the object from raw data, and propose a classification scheme for identifying the material composition of the object at each location
In this work, we demonstrate the ability to determine the material composition of a sample by measuring coherent scatter
diffraction patterns generated using a coded-aperture x-ray scatter imaging (CAXSI) system. Most materials are known
to exhibit unique diffraction patterns through coherent scattering of low-energy x-rays. However, clinical x-ray imagers
typically discard scatter radiation as noise that degrades image quality. Through the addition of a coded aperture, the
system can be sensitized to coherent scattered photons that carry information about the identity and location of the
scattering material. In this work, we demonstrate this process using a Monte-Carlo simulation of a CAXSI system. A
simulation of a CAXSI system was developed in GEANT4 with modified physics libraries to model coherent scatter
diffraction patterns in materials. Simulated images were generated from 10 materials including plastics, hydrocarbons,
and biological tissue. The materials were irradiated using collimated pencil- and fan-beams with energies of 160 kVp.
The diffraction patterns were imaged using a simulated 2D detector and mathematically deconstructed using an
analytical projection model that accounted for the known x-ray source spectrum. The deconstructed diffraction patterns
were then matched with a library of known coherent scatter form-factors of different materials to determine the identity
of the scatterer at different locations in the object. The results showed good agreement between the measured and known
scatter patterns from the materials, demonstrating the ability to image and identify materials at different 3D locations
within an object using a projection-based CAXSI system.
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