No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
The Recent Development of an X-ray Grating Interferometer at Shanghai Synchrotron Radiation Facility
Abstract
An X-ray grating interferometer has been installed at Shanghai
Synchrotron Radiation Facility (SSRF). Three sets of phase gratings were
designed to cover the wide X-ray energy range needed for biological and
soft material imaging capabilities. The performance of the grating
interferometer has been evaluated by a tomography study of a PMMA
particle packing and a new born mouse chest. In the mouse chest study,
the carotid artery and carotid vein inside the mouse can be identified
in situ without contrast agents.
Current bio-medical imaging researches aim to detect brain micrometastasis in early stage for its increasing incidence and high mortality rates. Synchrotron phase-contrast imaging techniques, such as in-line phase-contrast (IPC) and grating-based phase-contrast (GPC) imaging, could provide a high spatial and density imaging study of biological specimens' 3D structures. In this study, we demonstrated the detection efficiencies of these two imaging tools on breast cancer micrometastasis in an ex vivo mouse brain. We found that both IPC and GPC can differentiate abnormal brain structures induced by micrometastasis from the surrounding normal tissues. We also found that GPC was more sensitive in detecting the small metastasis as compared to IPC.
We report on significant advances and new results concerning a recently developed method for grating-based hard x-ray phase tomography. We demonstrate how the soft tissue sensitivity of the technique is increased and show in vitro tomographic images of a tumor bearing rat brain sample, without use of contrast agents. In particular, we observe that the brain tumor and the white and gray brain matter structure in a rat's cerebellum are clearly resolved. The results are potentially interesting from a clinical point of view, since a similar approach using three transmission gratings can be implemented with more readily available x-ray sources, such as standard x-ray tubes. Moreover, the results open the way to in vivo experiments in the near future.
The basic principles of x‐ray image formation and interpretation in radiography have remained essentially unchanged since Röntgen first discovered x rays over a hundred years ago. The conventional approach relies on x‐ray absorption as the sole source of contrast and draws exclusively on ray or geometrical optics to describe and interpret image formation. This approach ignores another, potentially more useful source of contrast—phase information. Phase‐sensitive techniques, which can be understood using wave optics rather than ray optics, offer ways to augment or complement standard absorption contrast by incorporating phase information. New approaches that can detect x‐ray phase shifts within soft tissues show promise for clinical and biological applications.
First Talbot interferometry in the hard X-ray region was demonstrated using a pair of transmission gratings made by forming gold stripes on glass plates. By aligning the gratings on the optical axis of X-rays with a separation that caused the Talbot effect by the first grating, moire fringes were produced inclining one grating slightly against the other around,the optical axis. A phase object placed in front of the first grating was detected by moire-fringe bending. Using the technique of phase-shifting interferometry, the differential phase corresponding to the phase object could also be measured. This result suggests that X-ray Talbot interferometry is a novel and simple method for phase-sensitive X-ray radiography.
Objectives: Phase-contrast and scattering-based x-ray imaging are known to provide additional and complementary information to conventional, absorption-based methods, and therefore have the potential to play a crucial role in medical diagnostics. We report on the first mammographic investigation of 5 native, that is, freshly dissected, breasts carried out with a grating interferometer and a conventional x-ray tube source. Four patients in this study had histopathologically proven invasive breast cancer. One male patient, without the presence of any malignant formations within the resected breast, was included as a control specimen.
Materials and Methods: We used a Talbot-Lau grating setup installed on a conventional, low-brilliance x-ray source; the interferometer operated at the fifth Talbot distance, at a tube voltage of 40 kVp with mean energy of 28 keV, and at a current of 25 mA. The device simultaneously recorded absorption, differential phase and small-angle scattering signals from the native breast tissue. These quantities were then combined into novel color- and high-frequency-enhanced radiographic images. Presurgical images (conventional mammography, ultrasonography, and magnetic resonance imaging) supported the findings and clinical relevance was verified.
Results: Our approach yields complementary and otherwise inaccessible information on the electron density distribution and the small-angle scattering power of the sample at the microscopic scale. This information can be used to potentially answer clinically relevant, yet unresolved questions such as unequivocally discerning between malignant and premalignant changes and postoperative scars and distinguishing cancer-invaded regions within healthy tissue.
Conclusions: We present the first ex vivo images of fresh, native breast tissue obtained from mastectomy specimens using grating interferometry. This technique yields improved diagnostic capabilities when compared with conventional mammography, especially when discerning the type of malignant conversions and their breadth within normal breast tissue. These promising results advance us toward the ultimate goal, using grating interferometry in vivo on humans in a clinical setting.
Phase-contrast radiography using an x-ray interferometer is presented for observing organic matter. High sensitivity of phase-contrast radiography is demonstrated with a rat cerebellar specimen without staining it with a contrast medium. The layer structure of the cerebellum can be observed in the obtained image while there is no clear structure in the corresponding absorption-contrast image. Quantitative image analysis is made possible by converting an x-ray interference pattern to an x-ray phase shift distribution. The lipid distribution in the cerebellum is discussed by evaluating x-ray phase shifts before and after lipid removal.
X-ray phase and absorption radiographs and tomograms of the heart of a rat were taken with an X-ray grating interferometer with monochromatic synchrotron radiation at a photon energy of 17.5 keV. The phase images show largely superior quality with respect to the absorption images taken with the same dose, particularly much better contrast and contrast-to-noise ratio. Different tissues can clearly be distinguished. The results demonstrate the potential of grating interferometry for two- and three-dimensional X-ray imaging of biological soft tissue in an aqueous environment.