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Reconstruction of spectral CT images
KTH, School of Engineering Sciences (SCI), Physics, Medical Imaging.
2011 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]


X-ray computed tomography (CT) is a medical imaging modality that allows reconstruction of

the internal stucture of the human body from a large number of x-ray attenuation measurements.

In recent years, the development of spectral CT, in which the energy dependence of the x-ray

attenuation coe-cient is utilized, has attracted considerable interest. This thesis is concerned with

a spectral CT system based on a photon-counting silicon strip detector which is being developed

in our group.

A computer model for photon counting spectral CT was developed and used for simulating

the proposed CT system as well as a laboratory CT setup designed for testing purposes. The

simulations were used to compare the performance of two reconstruction methods for spectral CT,

image-based energy weighting and basis material decomposition. The study shows that the two

methods perform equally well when the number of x-ray photons in each measurement is high, while

basis material decomposition performs signcantly worse than energy weighting for data with few

photons in each measurement.

Also included in the thesis is a simulation study of the detrimental eects of electronic noise

and thresold variations on image quality. It is shown that a proposed electronic noise reduction of

20% in the readout channels gives an improvement in mean



over many channels of only

1.8%. In addition, a scheme for countering electronic noise contamination of the lowest energy bins

due to threshold variations is discussed.

The nal chapter of the thesis describes an experiment which demonstrates that the CT detector

design studied here can indeed be used to obtain high-quality images.

Place, publisher, year, edition, pages
2011. , 60 p.
URN: urn:nbn:se:kth:diva-31676OAI: diva2:405436
Educational program
Master of Science in Engineering -Engineering Physics
Physics, Chemistry, Mathematics
Available from: 2011-03-22 Created: 2011-03-22 Last updated: 2011-11-09

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