X-ray tube-based diffraction enhanced imaging prototype images of full-thickness breast specimens: reader study evaluation

Abstract

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. BACKGROUND AND SIGNIFICANCECancer imparts distinct and measurable changes in breast tissue at the cellular level. However, absorption contrast based on the spatial distribution of x-ray attenuation does not always provide sufficient contrast due to often minimal differences in x-ray attenuation between normal and cancerous tissues. These microscopic and macroscopic alterations may cause x-ray refraction, a minute change in the direction of x-ray propagation, which is exploited by phase contrast imaging. X-ray refraction contrast is not yet widely used in medical imaging although several phase-contrast imaging devices are in various stages of research and development. (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) Diffraction enhanced imaging (DEI) is a specific type of analyzer-based phase contrast imaging. Traditionally, DEI has used intense, highly collimated synchrotron radiation (SR) to produce images based on absorption, refraction and extinction contrast. (5,6,21) The application of DEI to breast imaging has consistently provided superior contrast and signalto-noise ratio (SNR) when compared to conventional radiographic images.

High-Resolution Phase-Contrast Tomography on Human Collagenous Tissues: A Comprehensive Review

“…However, a relevant limitation to the clinical translation of the DEI method has been the need to use synchrotron radiation. In this direction, Faulconer et al [19] developed a DEI prototype (DEI-PR) using a Tungsten X-ray tube laboratory source combined with traditional DEI crystal optics. Full-thickness human breast tissue specimens were imaged with the DEI-PR at 60 keV, but also with a synchrotron-based DEI and digital mammography systems to demonstrate the clinical utility of the laboratory-based prototype.…”