Amir Livne

Experimental evaluation of image-based spectral analysis method for multi energy window photon counting x-ray CT

Photon counting spectral x-ray CT provides powerful techniques for analyzing various materials in-situ by utilizing multiple separate energy windows. In the recent few years, preliminary results of humans and animals which were scanned with such prototype systems have been shown. Although photon counting technology allows numerous separate energy windows, practical system design should consider and optimize the advantages of additional windows relative to the complexity, image quality and system’s cost. In this work we investigated experimentally intricate material differentiation with dedicated multi energy window spectral analysis method. Particular attention was given to the simultaneous presence of several mixtures and partial volume regions of different materials. These scenarios resemble complicated analyses in potential medical and pre-clinical applications. The results show that multi energy window setting has a great advantage over dual-energy setting especially where multiple material mixtures should be differentiated one from each other.

Measurement of charge division in pixelated CZT

In medical X-ray imaging using semiconductor detectors, small pixels are employed to increase image resolution and count rate capability. However, the use of small pixels increases the occurrence of imaging signals that are split between neighboring pixels or even lost in the gap regions between pixels. To assess this problem monolithic pixelated CZT blocks were scanned from pixel to gap to pixel using a filtered X-ray beam and a narrow diameter collimator. A novel technique for recording and digitizing time series data from neighboring pixels for analysis offline was employed. Singles and coincidence spectra were compiled for each location and energy. The extent of charge splitting or charge loss was determined. The technique of digital summing of coincidence signals in neighboring pixels to recover split events is demonstrated.