Purpose: The purpose of this study is to determine if diffraction enhanced imaging (DEI) can quantify anisotropy in bone microarchitecture. Background: Osteoporosis is characterized by low bone mass and microarchitectural deterioration of bone. A noninvasive tool for measuring the degree of anisotropy (DA) in bone microarchitecture will help clinicians better assess fracture risk in osteoporotic patients. DEI detects small angular deflections in an x-ray beam, and is only sensitive to angular changes in one plane. If the beam is refracted by multiple anisotropic microstructures (e.g. osteocyte lacunae and pores) in bone, the angular spreading can be measured with DEI and differences in the amount of spreading for different bone orientations is indicative of the DA in bone microarchitecture. Method: An x-ray-tube based DEI system was used to collect an array of DEI reflectivity profiles measured through bovine cortical bone samples with the bones oriented with the bone axis in the plane perpendicular to the propagation of the x-ray beam. Micro-CT images of the bones were obtained using a Scanco uCT40 ex vivo scanner, and the DA of the pore structure was quantified using BoneJ. Results: The maximum and minimum measured reflectivity profile widths through bone varied by a factor of two; this suggests that the microarchitecture is preferentially aligned with the bone axis in a 2-to-1 ratio. The DA for the cortical pores was 0.6, which agrees with DEI’s anisotropy measure. Conclusions: The preliminary findings of this study suggest that DEI is sensitive to anisotropy in bone microarchitecture.
Purpose: The goal of this study was to begin quantifying the performance of a second generation diffraction
enhanced imaging (DEI) system designed to reduce imaging time from our first generation system.
Background: DEI, a phase contrast x-ray imaging modality, generates images with enhanced soft tissue contrast at a
lower dose than conventional radiography. Our group has previously reported on an x-ray tube-based DEI system,
but a substantial gap remained between the imaging time of that system and that of a clinical DEI system.
Method: A high power, rotating anode x-ray tube was integrated into this second generation DEI system along with
an image intensifier to improve photon counting efficiency. Images of phantoms were acquired using a tube power
of 10 kW (125 kVp, 80 mA) at the silicon  reflection with the analyzer crystal at its half-reflectivity point.
Results: Our preliminary results show comparable image contrast to the first generation DEI system. Imaging time
was reduced by a factor four and x-ray-on time was reduced by a factor of sixty from the initial prototype system.
Conclusions: These early results from our second generation diffraction enhanced imaging system show significant
reduction in imaging time with preservation of DEI contrast.
Conventional mammographic image contrast is derived from x-ray absorption, resulting in breast structure visualization
due to density gradients that attenuate radiation without distinction between transmitted and scattered or refracted x-rays.
This leads to image blurring and contrast reduction, hindering the early detection of small or otherwise occult cancers.
Diffraction enhanced imaging (DEI) allows for dramatically increased contrast with decreased radiation dose compared
to conventional mammographic imaging due to monochromatic x-rays, its unique refraction-based contrast mechanism
and excellent scatter rejection. However, a lingering drawback to the clinical translation of DEI has been the requirement
for synchrotron radiation. Our laboratory developed a DEI prototype (DEI-PR) utilizing a readily available Tungsten xray
tube source and traditional DEI crystal optics, providing soft tissue images at 60keV. To demonstrate the clinical
utility of our DEI-PR, we acquired images of full-thickness human breast tissue specimens on synchrotron-based DEI,
DEI-PR and digital mammography systems. A reader study was designed to allow unbiased assessment of system
performance when analyzing three systems with dissimilar imaging parameters and requiring analysis of images
unfamiliar to radiologists. A panel of expert radiologists evaluated lesion feature visibility and histopathology correlation
after receiving training on the interpretation of refraction contrast mammographic images. Preliminary data analysis
suggests that our DEI system performed roughly equivalently with the traditional DEI system, demonstrating a
significant step toward clinical translation of this modality for breast cancer applications.
Diffraction enhanced imaging (DEI) uses monochromatic x-rays coupled to an analyzer crystal to extract information
about the refraction of x-rays within the object. Studies of excised biological tissues show that DEI has significant
contrast-to-noise ratio (CNR) advantages for soft tissue when compared to standard radiography. DEI differs from
conventional CT in that its refraction contrast depends on x-ray energy as 1/E, thus the energy and dose considerations
for conventional CT will be inappropriate. The goal of this study was to assess the optimal energy for in vivo CT
imaging of a mouse head to obtain the largest soft tissue refraction CNR. Through a theoretical model, optimum
refraction CNR for mouse brain imaging was found to be about 20 keV. The findings were tested experimentally using
the DEI system at the X15A beamline of the National Synchrotron Light Source. Using the parameters for optimized
refraction CNR (20 keV, silicon  reflection), large image artifacts were caused by DEI's scatter-rejection
properties. By increasing the x-ray energy and using a lower order diffraction, silicon , soft tissue features within
the brain, including the hippocampus, could be resolved.