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Histopathological analysis is the current gold standard in breast cancer diagnosis and management, however, as imaging technology improves, the amount of potential diagnostic information that may be demonstrable radiologically should also increase. We aimed to evaluate the potential clinical usefulness of 3-D phase-contrast micro-computed tomography (micro-CT) imaging at high spatial resolutions as an adjunct to conventional histological microscopy. Ten breast tissue specimens, 2 mm in diameter, were scanned at the SYRMEP beamline of the Elettra Synchrotron using the propagation-based phase-contrast micro-tomography method. We obtained $1.2~\mu \text{m}$ pixel size images, which were analyzed and compared with corresponding histological sections examined under light microscopy. To evaluate the effect of spatial resolution on breast cancer diagnosis, scans with four different pixel sizes were also performed. Our comparative analysis revealed that high-resolution images can enable, at a near-histological level, detailed architectural assessment of tissue that may permit increased breast cancer diagnostic sensitivity and specificity when compared with current imaging practices. The potential clinical applications of this method are also discussed.

X-ray breast computed tomography (breast-CT) is a new emerging technique for breast imaging however its application is still limited because of low spatial resolution and high delivered dose. In this framework, synchrotron radiation provides ideal X-ray imaging conditions. Tunable and monochromatic laminar X-ray beam, along with large propagation distance, allows acquiring images with high quality, low scatter and dose reduction, due to the selection of the most suitable energy for the given thickness and breast composition. Moreover, the high spatial coherence permits to exploit the phase-contrast effects enabling a better image quality and soft tissue contrast. At the Elettra synchrotron facility, in Italy, a project for in vivo low-dose, high-contrast and high-resolution breast-CT is under development using a high-efficiency photon-counting detector. Due to the vertical size of the beam (*3.5 mm) the scan requires a sequence of vertical steps. Thus reducing the number of projections is essential to shorten the total acquisition time. Optimized preprocessing algorithms (phase-retrieval) and the state of the art of tomographic reconstruction methods are crucial to improve image quality. In this work, performances of standard and iterative reconstruction algorithms at different experimental conditions are compared, evaluating quantitatively the image quality in terms of Contrast-to-Noise ratio and edge sharpness. Preliminary results suggest that, in the light of a clinical exam where a short scan time is desirable, the projection number can be reduced without a major loss in image quality by applying FBP based reconstruction algorithms and phase-retrieval pre-processing.

Rationale and Objectives This study employs clinical/radiological evaluation in establishing the optimum imaging conditions for breast cancer imaging using the X-ray propagation-based phase-contrast tomography. Materials and Methods Two series of experiments were conducted and in total 161 synchrotron-based computed tomography (CT) reconstructions of one breast mastectomy specimen were produced at different imaging conditions. Imaging factors include sample-to-detector distance, X-ray energy, CT reconstruction method, phase retrieval algorithm applied to the CT projection images and maximum intensity projection. Observers including breast radiologists and medical imaging experts compared the quality of the reconstructed images with reference images approximating the conventional (absorption) CT. Various radiological image quality attributes in a visual grading analysis design were used for the radiological assessments. Results The results show that the application of the longest achievable sample-to-detector distance (9.31 m), the lowest employed X-ray energy (32 keV), the full phase retrieval, and the maximum intensity projection can significantly improve the radiological quality of the image. Several combinations of imaging variables resulted in images with very high-quality scores. Conclusion The results of the present study will support future experimental and clinical attempts to further optimize this innovative approach to breast cancer imaging.