Michael Gruber MD, Presenter: Nothing to Disclose

Mokhtar Chmeissani, Abstract Co-Author: Nothing to Disclose

Peter Homolka PhD, Abstract Co-Author: Nothing to Disclose

Meritxell Tortajada Gimenez, Abstract Co-Author: Nothing to Disclose

Michael Pretterklieber, Abstract Co-Author: Nothing to Disclose

Franz Maria Kainberger MD, Abstract Co-Author: Nothing to Disclose

The aim of the project is to develop a digital imaging X-ray machine based on direct capture of X-ray photons with room temperature solid-state pixel detectors coupled with photon counting readout electronics, Medipix-2 chip. The direct capture approach has a much higher SNR compared to a system where photons are captured in a scintillating crystal coupled to amorphous Si.

The Medipix-2 chip is a matrix of 256 x 256 pixels with a pixel pitch of 55μm. Thus the effective area of one chip assembly (a Medipix-2 chip bump-bonded to CdTe) is 14.08mm x 14.08mm. A large monolithic image of 11.2cm x 7cm was obtained by consecutive displacement approach. We took images of 8 human cadaver hands at 4 different dose levels (0.25, 0.64, 1.25, 2.5mAs - skin dose 2.4, 6, 12, 26μGy) at 44kV tube voltage with the new detector and also with a flat-panel detector system (Philips Digital Diagnost, Philips, Hamburg, Germany). Three radiologists determined the presence of an appreciable difference in image quality and ranked them using a five-point scale.

The new detector delivered a significantly better image quality especially in ultra low dose levels such as 2.4 or 6μGy compared to the flat-panel detector system. At higher dose levels the new system was ranked equivalently to the DR-system. However, we noticed some small artifacts of different origin due to slight instability of detector elements.

In our study the prototype of an X-ray machine based on direct capture of X-ray photons with solid-state pixel detectors coupled to photon counting readout electronics achieved better image quality in musculoskeletal images compared to an established direct detector system.

An X-ray machine based on direct capture of X-ray photons with pixel detectors coupled to photon counting readout electronics has big potential to obtain excellent image quality even at very low dose.

Gruber, M, Chmeissani, M, Homolka, P, Tortajada Gimenez, M, Pretterklieber, M, Kainberger, F, Musculoskeletal Imaging by a Prototype of a Digital Imaging X-ray Machine Based on Direct Capture of X-ray Photons with Pixel Detectors Coupled to Photon Counting Readout Electronics.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6012711.html