Abstract
X-ray computed tomography of small animals and their organs is an essential tool in basic and preclinical biomedical research. In both phase-contrast and absorption tomography high spatial resolution and short exposure times are of key importance. However, the observable spatial resolutions and achievable exposure times are presently limited by system parameters rather than more fundamental constraints like, e.g., dose. Here we demonstrate laboratory tomography with few-ten μm spatial resolution and few-minute exposure time at an acceptable dose for small-animal imaging, both with absorption contrast and phase contrast. The method relies on a magnifying imaging scheme in combination with a high-power small-spot liquid-metal-jet electron-impact source. The tomographic imaging is demonstrated on intact mouse, phantoms and excised lungs, both healthy and with pulmonary emphysema.
Highlights
Imaging, the extra optical elements in the grating-based imaging (GBI) arrangement typically cause a dose and exposure-time disadvantage compared to the free-space propagation of propagation-based imaging (PBI)
This dose and exposure-time advantage of PBI over GBI is not a general result and the performance of the methods must be evaluated for each individual imaging task, the present study was performed with PBI since it has demonstrated lower-dose and shorter-exposure-time high-resolution imaging of the specific class of objects discussed here
By changing the effective propagation distance zeff = (R1R2)/(R1 + R2) the contrast can be tuned from pure absorption to increasing phase contrast[24], albeit typically at the price of longer exposure times
Summary
Imaging, the extra optical elements (gratings) in the GBI arrangement typically cause a dose and exposure-time disadvantage compared to the free-space propagation of PBI. The advantages include speed, 3D with thinner effective slicing, and less destructive and simplified sample preparation In this application high spatial resolution and short exposure times are essential while dose is of lesser concern. The method relies on a magnifying propagation-based arrangement in combination with a high-brightness liquid-metal-jet electron-impact source[19] This source type has previously demonstrated its applicability for very high spatial resolution (cellular and sub-cellular) phase-contrast imaging of blood vessels, tumors, lung tissue, and muscle tissue in organs and in whole-body mouse and zebrafish, but with long exposure times and high dose[20,21,22,23]. We demonstrate the system for bone absorption imaging in intact mouse and for phase-contrast imaging of phantoms and excised mouse lungs, both healthy and with pulmonary emphysema
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