Research On Key Parameters Of Quality Testing Technology For The Spectral CT Imaging

Compared to traditional Computed Tomography(CT),spectral CT provides more useful information and functions for clinical applications.However,due to the lack of corresponding and suitable standards,old techniques are still being used for the performances testing of spectral CT,for example,some significant functions parameters such as energy spectrum curve,quantitative analysis of material,metal artifact reduction have not been included,which makes the advanced equipment can not give full play to its maximum benefits.It is essential to develop objective and practical standards and techniques for the performance assessment and the quality control of the spectral CT.This thesis systematically summarizes the research progress of spectral CT and its application image quality,and analyzes the related problems,some quantitative parameters such as mono-energy curves and beam-hardening artifacts reduction are in-depth studied as well as a result,the testing and assessing methods were proposed,the main works are as following:(1)The spectral CT principle has been introduced briefly,and key spectral CT parameters have been discussed in detail in combination with clinical cases.(2)Based on the imaging principle,a phantom which could be used for quantitative analysis and testing of different compositions was designed and produced.this phantom has been used to do experimental testing on both Siemens Force CT and GE Discovery 750.through the experiments,the different CT numbers with various keV(60keV,70keV,80keV)were obtained,and by using the energy spectrum function software analysis tools,energy spectrum diagram,iodine base water map,effective atomic number histogram and matrix scatter distribution map are analyzed,the key functional parameters of the two CT's energy spectrum technology are verified,and the feasibility of the spectral CT image quality testing technology is to be evaluated.(3)A phantom was designed and produced,this phantom is used as a tool for making assessment of metal artifacts reduction(MAR).there are several different materials including pure ionized water,Teflon and stainless steel nail,various materials is being used to analog different issues,among these materials,water improves the uniformity of the phantom image and offers better contrast to metal.The phantom is used to do the experiment on GE Discovery 750 CT,there are three groups depending on different scan protocols,the artifact index AI is used to analyze the artifact image objectively.The results show that under the conditions of MONO and MARS,the AI value of image is significantly lower than that of the other two models,while as the quality of MONO image is better than that of 120kVp mode.The image quality of MONO is better than that of 120kVp mode.The noise of MONO and MARS images is obviously lower than that of the 120kVp mode and the MONO mode.The main innovations in the study are below:(1)We propose to establish a set of techniques,methods and procedures to assess the performance of spectral CT objectively;(2)We analyze and compare the performances to optimize the phantom designs.Phantoms were developed with different materials and manufacture precsions.