Phase-sensitive X-ray imaging of synovial joints

Abstract

To test the efficacy of phase-sensitive X-ray imaging for intact synovial joints, whereby refraction effects, along with the attenuation of conventional radiography, can be exploited. Intact cadaveric human knee joints were imaged, in the computed tomographic mode, using an analyzer-based X-ray system at the National Synchrotron Light Source, Brookhaven National Laboratory. A collimated fan beam of 51 keV X-rays was prepared by a silicon [1,1,1 reflection] double-crystal monochromator. The X-ray beam transmitted through the specimen was imaged after diffraction in the vertical plane by means of the analyzer crystal with the analyzer crystal tuned to its half-reflectivity point (6.5 microrad). A two-dimensional filtered backprojection (FBP) algorithm was used for reconstructing transverse slices of images. The resulting images demonstrate simultaneous soft tissue and bone contrast at a level that has not been achieved previously. Identifiable structures include articular cartilage, cruciate ligaments, loose connective tissue, menisci, and chondrocalcinosis. Phase-sensitive X-ray imaging using an analyzer-based system renders exceptionally high quality images of soft and hard tissues within synovial joints, with high contrast and resolution, and thus holds promise for the eventual clinical utility.