Jörg Freudenberger

New x-ray tube performance in computed tomography by introducing the rotating envelope tube technology.

The future demands of computed tomography imaging regarding the x-ray source can be summarized with higher scan power, shorter rotation times, shorter cool down times and smaller focal spots. We report on a new tube technology satisfying all these demands by making use of a novel cooling principle on one hand and of a novel beam control system on the other hand. Nowadays tubes use a rotating anode disk mainly cooled via radiation. The Straton x-ray tube is the first tube available for clinical routine utilizing convective cooling exclusively. It is demonstrated that this cooling principle makes large heat storage capacities of the anode disk obsolete. The unprecedented cooling rate of 4.8 MHU/min eliminates the need for waiting times due to anode cooling in clinical workflow. Moreover, an electronic beam deflection system for focal spot position and size control opens the door to advanced applications. The physical backgrounds are discussed and the technical realization is presented. From this discussion the superior suitability of this tube to withstand g-forces well above 20 g created by fast rotating gantries will become evident. Experience from a large clinical trial is reported and possible ways for future developments are discussed.

Perspectives of medical X-ray imaging

Abstract While X-ray image intensifiers (XII), storage phosphor screens and film-screen systems are still the work horses of medical imaging, large flat panel solid state detectors using either scintillators and amorphous silicon photo diode arrays (FD-Si), or direct X-ray conversion in amorphous selenium are reaching maturity. The main advantage with respect to image quality and low patient dose of the XII and FD-Si systems is caused by the rise of the Detector Quantum Efficiency originating from the application of thick needle-structured phosphor X-ray absorbers. With the detectors getting closer to an optimal state, further progress in medical X-ray imaging requires an improvement of the usable source characteristics. The development of clinical monochromatic X-ray sources of high power would not only allow an improved contrast-to-dose ratio by allowing smaller average photon energies in applications but would also lead to new imaging techniques.

Hairline fracture detection using Talbot-Lau x-ray imaging

Talbot-Lau X-ray imaging (TLXI) provides information about scattering and refractive features of objects – in addition to the well-known conventional X-ray attenuation image. We investigated the potential of TLXI for the detection of hairline fractures in bones, which are often initially occult in conventional 2D X-ray images. For this purpose, hairline fractures were extrinsically provoked in a porcine trotter (post-mortem) and scanned with a TLXI system. In the examined case, hairline fractures caused dark-field and differential-phase signals, whereas they were not evident in the conventional X-ray image. These findings motivate a comprehensive and systematic investigation of the applicability of TLXI for diagnosing hairline fractures.