Phase-sensitive X-ray imaging of synovial joints.

OBJECTIVE: 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.
DESIGN: 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.
RESULTS: 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.
CONCLUSION: 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.