Moa Yveborg MSc, Abstract Co-Author: Stockholder, Prismatic Sensors

Cheng Xu, Abstract Co-Author: Nothing to Disclose

Mats Persson, Abstract Co-Author: Nothing to Disclose

Staffan Karlsson, Abstract Co-Author: Nothing to Disclose

Hans Bornefalk MS, Abstract Co-Author: Nothing to Disclose

Han Chen, Abstract Co-Author: Nothing to Disclose

Ben Huber, Abstract Co-Author: Nothing to Disclose

Xuejin Liu, Abstract Co-Author: Nothing to Disclose

Mats Danielsson PhD, Presenter: Stockholder, Prismatic Sensors AB President, Prismatic Sensors AB Stockholder, Innovicum AB President, Innovicum AB Research Grant, Koninklijke Philips NV Stockholder, Biovica International AB Board Member, Biovica International AB

Indicative research have shown electronic noise to be a limiting factor in low-dose clinical computed tomography (CT) using energy integrating x-ray detectors. We are developing a photon-counting silicon detector with 8 energy bins and 0.2x0.3 mm^2 detector elements at the isocenter for clinical CT applications. The purpose of this work is to measure the detective quantum efficiency (DQE) in the projection domain of our silicon detector when mounted in a Philips iCT gantry and show that the electronic noise has little impact on the measured signal.

The detector module consists of a diode array on a silicon substrate with a thickness of 0.5 mm. One module contains 50 strips constituting the detector elements, each with a cross-section of 0.2x0.3 mm^2 at the isocenter transverse to the beam direction. For this work, we have tested the first modules of a full photon counting CT system mounted in a Philips iCT gantry. We measure the pre-sampled MTF of the silicon detector at by scanning a single pixel using a narrow slit source of x-rays and taking the Fourier transform of the resulting profile. The noise power spectrum (NPS) and DQE are calculated from measurements at several clinically relevant input count rates. We use GATE (Geant4 Application for Emission Tomography) to simulate the photon interaction in a model of the silicon detector and compare the results to corresponding physical measurements.

The results of the measurements demonstrate the electronic noise to have little impact on the measured signal. The simulation model is validated using physical measurements and the estimated DQE of the final detector configuration presented.

The first modules of a full photon counting CT photon-counting silicon detector with eight energy bins has successfully been mounted and tested in a Philips iCT gantry. Measurements of the MTF, NPS and DQE is presented, demonstrating a dose-reduction potential in low-dose clinical CT applications compared to conventional energy integrating detectors.

A typical application is low dose CT imaging, such as lung cancer screening and pediatric imaging.

Yveborg, M, Xu, C, Persson, M, Karlsson, S, Bornefalk, H, Chen, H, Huber, B, Liu, X, Danielsson, M, First Measurements of Projection DQE on Photon Counting Silicon-based Spectral CT System.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14013003.html