Although the mortality rate of breast cancer has been reduced with the introduction of screening mammography, many women undergo unnecessary subsequent examinations due to inconclusive diagnoses. Therefore, spatial resolution and soft tissue contrast must meet very high standards. The former is necessary in order to be able to detect and distinguish closely spaced microcalcifications from each other. Thus, a high spatial resolution is demanded. Superposition of anatomical structures especially within dense breasts in conjunction with the inherently low soft tissue contrast of absorption images compromises image quality. This can be overcome by phase-contrast imaging. In this study, we analyze the spatial resolution of grating-based multimodal mammography dose-dependently using a mammographic phantom and one freshly dissected mastectomy specimen at an inverse Compton X-ray source. Here, the main focus was on estimating the spatial resolution with the sample in the beam path and discussing benefits and drawbacks of the method used as well as the estimation of the mean glandular dose. Finally, the possibility of improving the spatial resolution is investigated by comparison of the monochromatic grating-based mammography with the standard one. In almost all cases, the spatial resolution is higher in our proposed approach while the dose can be significantly reduced. Additionally, phase-contrast imaging helps to improve the detection of tumor lesions
Inverse Compton scattering of infrared photons from relativistic electrons generates brilliant quasi-monochromatic X-rays with an electron accelerator with dimensions of only a few meters, e.g. at the storage ring based inverse Compton scattering X-ray source employed at the Munich Compact Light Source. Availability of synchrotron light in a laboratory comes along with broader access to synchrotron techniques, especially in - but not limited to - clinical imaging and pre-clinical biomedical applications. We have been exploring the latter in daily user operation since commissioning of the MuCLS. So far, the focus has been on dynamic in vivo small-animal respiratory imaging, grating-based phase-contrast imaging, e.g. for quantitative material decomposition, and spectroscopic imaging, e.g. for angiography.
While conventional x-ray tube sources reliably provide high-power x-ray beams for everyday clinical practice, the broad spectra that are inherent to these sources compromise the diagnostic image quality. For a monochromatic x-ray source on the other hand, the x-ray energy can be adjusted to optimal conditions with respect to contrast and dose. However, large-scale synchrotron sources impose high spatial and financial demands, making them unsuitable for clinical practice. During the last decades, research has brought up compact synchrotron sources based on inverse Compton scattering, which deliver a highly brilliant, quasi-monochromatic, tunable x-ray beam, yet fitting into a standard laboratory. One application that could benefit from the invention of these sources in clinical practice is coronary angiography. Being an important and frequently applied diagnostic tool, a high number of complications in angiography, such as renal failure, allergic reaction, or hyperthyroidism, are caused by the large amount of iodine-based contrast agent that is required for achieving sufficient image contrast. Here we demonstrate monochromatic angiography of a porcine heart acquired at the MuCLS, the first compact synchrotron source. By means of a simulation, the CNR in a coronary angiography image achieved with the quasi-mono-energetic MuCLS spectrum is analyzed and compared to a conventional x-ray-tube spectrum. The results imply that the improved CNR achieved with a quasi-monochromatic spectrum can allow for a significant reduction of iodine contrast material.
Grating based x-ray phase-contrast reveals differential phase-contrast (DPC) and dark-field contrast (DFC) on top of the conventional absorption image. X-ray vector radiography (XVR) exploits the directional dependence of the DFC and yields the mean scattering strength, the degree of anisotropy and the orientation of scattering structures by combining several DFC-projections. Here, we perform an XVR of an ex vivo human hand specimen. Conventional attenuation images have a good contrast between the bones and the surrounding soft tissue. Within the bones, trabecular structures are visible. However, XVR detects subtler differences within the trabecular structure: there is isotropic scattering in the extremities of the phalanx in contrast to anisotropic scattering in its body. The orientation changes as well from relatively random in the extremities to an alignment along the longitudinal trabecular orientation in the body. In the other bones measured, a similar behavior was found. These findings indicate a deeper insight into the anatomical configuration using XVR compared to conventional radiography. Since microfractures cause a discontinuous trabecular structure, XVR could help to detect so-called radiographically occult fractures of the trabecular bones.