Coherence-enhanced synchrotron radiology: Refraction versus diffraction mechanisms Y. Hwu, H. H. Hsieh, and M. J. Lu Institute of Physics, Academia Sinica, Nankang, Taipei, Taiwan 11529, Republic of China W. L. Tsai and H. M. Lin Department of Materials Science, Tatung Institute of Technology, Taipei, Taiwan, Republic of China W. C. Goh Department of Materials Science, National University of Singapore, Singapore 119260 B. Lai Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 J. H. Je and C. K. Kim Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang, 790-784 Korea D. Y. Noh Department of Materials Science and Engineering, Kwangju Institute of Science and Technology, Kwangju, 506-712 Korea H. S. Youn Pohang Accelerator Laboratory, Pohang University of Science and Technology, Pohang, 790-784 Korea G. Tromba Sincrotrone Trieste SCpA, 34012 Trieste, Italy G. Margaritondo a) Institut de Physique Applique ´e, Ecole Polytechnique Fe ´de ´rale, CH-1015 Lausanne, Switzerland Received 18 March 1999; accepted for publication 9 July 1999 Tests performed in different regimes reveal the interplay of two edge-enhancement mechanisms in radiological images taken with coherent synchrotron light. The relative weight of the two mechanisms, related to refraction and to Fresnel edge diffraction, can be changed in a controlled way. This makes it possible to obtain different images of the same object with complementary information. © 1999 American Institute of Physics. S0021-89799903720-2 I. INTRODUCTORY REMARKS The high coherence levels of the third-generation syn- chrotron light sources open the way to various approaches to radiology. 1–8 Such approaches show promise of effective di- agnostic applications with a reduced radiation dose. The im- pact could be quite important, for example, in techniques like mammography. 3 The most important coherence factor in this progress is the x-ray beam geometry. 8 More specifically, it is the fact that the standard collimation of the synchrotron emission is now accompanied by an extremely small source size—at least in the vertical direction in the case of bending-magnet source. 9 The improvement in the image quality is not due to a single factor, but at least 1–8 to two different mechanisms: refraction and edge diffraction. Our present tests clearly show that both mechanisms can play a role, and that their relative weight in a given image depends on the experimental geometry, on the type of specimen, and on other parameters. By acting on these factors, we can move from one regime to the other and vice versa in a controlled way. The clarification of the different image-enhancing fac- tors is important for at least two different reasons. First of all, the two main enhancing mechanisms affect in different ways the edges between different specimen areas. Therefore, their understanding is important in order to correctly extract morphological information from the images—for example, for diagnostic applications. Second, the possibility to select one specific enhance- ment mechanism makes it possible to take different images carrying different and complementary information. This flex- ibility could be potentially exploited to enhance the future radiological applications of synchrotron radiation. As a consequence, such applications are likely to involve the parallel use of different and complementary approaches. Those concerning our present work—which are based on edge enhancement—could be complemented by other tech- niques such as the ‘‘diffraction enhanced imaging’’ DEI recently described by Chapman et al. 4 The potential final result is effective radiological diagnosis at low dose levels. Our present discussion is organized as follows. In Sec.II, we briefly review the two edge-enhancement mechanisms a Electronic mail: marga@dpmail.epfl.ch JOURNAL OF APPLIED PHYSICS VOLUME 86, NUMBER 8 15 OCTOBER 1999 4613 0021-8979/99/86(8)/4613/6/$15.00 © 1999 American Institute of Physics