Phase-and-amplitude computer tomography

Abstract

A tomographic technique is proposed for reconstruction under specified conditions of the three-dimensional distribution of complex refractive index in a sample from a single projection image per view angle, where the images display both absorption contrast and propagation-induced phase contrast. The algorithm achieves high numerical stability as a consequence of the complementary nature of the absorption and phase contrast transfer functions. The method is pertinent to biomedical imaging and nondestructive testing of samples exhibiting weak absorption contrast. © 2006 American Institute of Physics. DOI: 10.1063/1.2226794 X-ray computer tomography CT is a well-established technique for three-dimensional 3D imaging of internal structure of samples. 1,2 Conventional CT imaging is based on the differential attenuation of transmitted x rays by constituents of the sample. This contrast mechanism is effective for distinguishing between elemental components with significant differences in atomic number or density, e.g., between flesh and bones in the case of medical CT. However, the difference in x-ray attenuation by different types of soft tissues e.g., healthy and malignant ones is typically rather weak, which results in poor image contrast, hampering diagnostics. It has been suggested that x-ray phase contrast can be utilized for improvement of the contrast in transmission images of noncrystalline samples consisting predominantly of light chemical elements. 3‐5 Subsequently, phase-contrast x-ray CT PCT has been implemented in several forms, including x-ray interferometry, 6,7 , analyzer-based 8,9 and propagation-based phase contrast, 10‐12 and others. The sub