Limitations to the spatial resolution of current digital x-ray systems are bounded by the physical characteristics of the xray
detector. However, the need to image smaller structures provides motivation to develop high-resolution x-ray
detector systems for use with computed radiographic, and tomographic x-ray systems. We report the implementation of
a tilted detector technique (TDT) to attain near isotropic resolution enhancement by combining two orthogonal image
views, acquired with existing detector hardware tilted at a fixed angle.
Images were acquired using a ceiling-mounted x-ray unit (Proteus XR/a, GE Medical Systems, 50kVp, 250mAs).
Images were digitized using a Fujifilm Capsula X CR system, from a 35×43cm detector cassette placed on an angulated
stand, featuring a 3520×4280 image matrix with an in-plane pixel spacing of 0.1mm. Three images were acquired: two
for use with our TDT; and one for comparison, with no detector tilt. Performance was determined by using two line-pair
phantoms (Models 07-521 and 07-533, Nuclear Associates) placed orthogonally to each other in the field of view.
Custom software corrected for perspective distortion, co-registered and combined the tilted-detector images into a single
Following unwarping and co-registration, the limiting spatial resolution of an image obtained via the weighted
combination of the two orthogonal views (8 lp/mm) is found to be superior to that of a single view acquired with no
detector tilt (5 lp/mm).
This novel technique shows significant improvement in the spatial resolution of x-ray image acquisitions, using existing
x-ray components and detector hardware.
In this paper, the accuracy and precision of RSA analysis using a GE Innova<sup>TM</sup> 4100 digital flat panel and a Siemens Multistar x-ray image intensifier (XRII) were evaluated and compared with that of a conventional film-screen system, in order to explore the possibility of real-time kinematic and dynamic RSA study. A phantom, having two rigid body segments with no movement, was constructed and imaged by the digital flat panel, XRII and conventional screen-film systems, respectively. The acquired images were measured and motions were derived. The mean and standard deviation of the repeated results were analyzed to determine the accuracy and precision, respectively. Comparing all three axes, the lowest rotational accuracy and precision were 0.008 ± 0.011°, 0.013 ± 0.015° and 0.006 ± 0.05° while the lowest translational accuracy and precision were 25 ± 28 mm, 17 ± 37 mm and 4 ± 6 mm for the film-screen, XRII and digital flat panel, respectively. The evaluation of the accuracy and precision of the RSA in this study confirms its place as a highly accurate method. The study shows that both digital flat panel and XRII systems have potential application to the kinematics and dynamics joint study.