Euromedim 2006 :1st European Conference on Molecular Imaging Technology

A simple method to estimate coordinate resolution of pixelized detectors

11 May 2006, 14:00

1h

Palais du Pharo, Marseille

poster • New ideas Poster session : Imaging systems, Molecular Imaging

Speaker

Dr Varlen Grabski (Instituto de Fisica UNAM)

Description

A simple method to estimate the coordinate resolution of pixelized detectors using non-single photon counting read out is proposed. This method can be useful particularly for testing the detectors used in digital imaging systems. The traditional technique of determining the coordinate resolution of this type of detectors is mainly based on the use of line spread function measurements that permit to recover the resolution distribution. The proposed method is based on the determination of the statistical correlation between neighbor elements in the detector. The correlation is determined by means of statistical noise measurement of the isolated elements and the linear combination of neighbor elements. To suppress the possible contribution of the beam spatial variation, the differences between neighbor elements is used. The distribution of differences between the detector neighbor pixels is constructed for the pixels sharing the same edge “X” and “Y”, or having only one common vertex “U” and “V”. For the validation of the method, the pixel detector of mammography unit General Electric Senographe 2000D has been used. For this purpose the pixelized detector has been irradiated by X-ray photons along the entire surface. The dependence of the resolution on the photon intensity value and the pixel coordinate has been studied. The asymmetry of correlation between the perpendicular directions has been studied to estimate the possibilities of this method to detect the existence of asymmetry in hardware design. The coordinate resolution of the studied detector, having pixel size of 100 µm, is of the order of 50 –55 µm, that is almost twice larger than the value conditioned by pixel geometrical sizes. A small asymmetry between the X and Y directions has been detected. By use of detector spatial resolution data in the approximation of Gaussian behavior of point spread function the modulation transfer function can be estimated. The reconstructed modulation transfer function is in good agreement with MTF measurements of the studied detector.