Synchrotron radiation microtomography is a new technique with high directionality of a synchrotron radiation beam and a high-resolution detector array. In this study, we estimated the visualization of the peripheral human lung structure with an ultra-high-resolution computed tomography (CT) system, the synchrotron radiation CT. The synchrotron radiation CT system uses the bending magnet beamline emitted from the 8.0 GeV electron storage ring. Six lung specimens were obtained at autopsy: 3 normal, 1 cellular alveolitis, 1 diffuse alveolar damage, and 1 pulmonary hemorrhage. Each specimen was cut down to a cylindrical sample with 6-mm diameter and 15- to 25-mm height. The synchrotron radiation CT images of these lung samples were obtained using the ultra-high-resolution image detector system with a charge coupled device (CCD) array detector (1024 × 1024 pixels with 12 × 12 μm2 pixel size). After that, the sample specimens were sliced to 200 μm (micrometer) thickness, and were observed with a stereomicroscope and by contact radiography. Finally, approximately 10-μm thick microscopic images were obtained and compared with the synchrotron radiation CT images. The synchrotron radiation CT could depict the peripheral lung including peripheral airways, airspaces, and alveolar walls individually. Each finding in the 3 disease processes seen on the synchrotron radiation CT images correlated well with the microscopic findings. The synchrotron radiation CT allows microtomographic imaging of human lung specimens with ultra high-spatial resolution (12 μm) on a level approaching that of conventional histopathology, without sectioning.
X-rays have been used for diagnostic medical imaging for more than 100 years. Although new techniques such as computed tomography (CT) have been developed, the means of producing X-rays has altered little during that time. CT is now widely used in clinical practice because it produces images of high diagnostic quality with high resolution. High-resolution CT (HRCT) has been developed and is an essential examination for chest diagnosis in daily practice. However, the spatial resolution of HRCT is not of sufficient resolution to depict the microscopic pathologic process in diseased lung in some cases. For example, the HRCT findings, such as ground glass opacity, often involves various pathologic features representing different pathologic processes. Thus, conventional x-ray sources used for clinical CT systems would appear to have some limitations in performance in terms of spatial and contrast resolution.
Synchrotron radiation is emitted from an electron traveling at almost the speed of light when its path is bent by a magnetic field. The synchrotron radiation is an ultra-bright beam with a continuous spectrum from infrared rays to x-ray (white beam). Synchrotron radiation is useful in various fields and in both fundamental and applied research, such as the following advanced research fields: materials science, earth science, environmental science, life science, and medical diagnosis. Using synchrotron radiation, the structures and characteristics of the materials can be analyzed without cutting and without destruction. Grodzins first proposed the application of synchrotron radiation to CT in 1983. 1,2 Synchrotron radiation has features available for ultra-high-resolution CT, which are the high photon flux from synchrotron x-ray sources and the small angular source size leading to negligible geometric blur. The features enable synchrotron radiation CT to obtain images with high spatial resolution and a high signal-to-noise ratio. 3–10
In the present study, using synchrotron radiation CT developed for structural studies of biologic specimens, we investigated its potential in lung imaging with precise histologic and histopathologic correlation.