Quanlity And Dose Control Of CT Component In PET/CT

第一部分The study of CT scanner dose and quality test in PET/CTObjective:To investigate the method of dose and quality test for CT scanner in PET/CT and its application. To test the dose and quality of the CT scanner in PET/CTMaterials and Methods:Catphan500and head dose phantom was selected for the scan by PET/CT(GE Discovery ST-16). The image quality was evaluated by high resolution、low contrast、uniformity、noise. CTDIw and CTDIvol were calculated.Results:The image quality of CT in PET/CT is different in quality control test and those of clinical work. And the the image quality in quality control test is better than the quality of clinical work.CONCLUSION:There is little different focuses between the CT scanner quality control test in PET/CT and those of clinical work.The former aim to keeping the stability of CT scanner working. But the latter needs get more accuracy diagnosis information. After all, quality control tests are the guarantee of how to decrease of radiation dose caused by CT in PET/CT, while ensure quality of CT image. 第二部分Study on relationships between CT dose and CT image quality in PET/CT (1)Objective:The aim of the study was to examine how to decrease of radiation dose caused by CT in PET/CT without the decline of image quality.Materials and Methods:PET/CT (GE Discovery ST16) was used to scan to CT quality module (Catphan500) in PET/CT clinical acquisition protocol with30～210mA and Pitch0.938,1.375and1.75, total30groups. The image quality was evaluated by high resolution、low contrast、uniformity、noise. CTDIw and CTDIvol were calculated under the scan conditions mentioned above by DCT10dose module. The relationship between CT image quantity and CT dose was also estimated.Results:As the increase of tube current, CT dose have linear increase trend. CT dose decreased with the Pitch increasing. CT dose was related to uniformity, but not to high resolution. The low contrast of CT image improved with the CT dose increasing. And the decrease of noise with the increase of CT dose was showed with an expression.Conclusions:CT dose varied with tube current and Pitch in some disciplines. Some index of CT image quality declined with CT radiation dose decreasing, and with kinds of disciplines. However, the radiation dose by CT in PET/CT could be decreased appropriately by lowering the tube current or raising the Pitch, under the guarantee of the quality of the CT image. 第三部分Study on relationships between CT dose and CT image quality in PET/CT(2)Objective:The aim of the study was to examine how to decrease radiation dose caused by CT in PET/CT without the decline of image quality.Materials and Methods:PET/CT (GE Discovery ST-16) was used to scan to CT quality module (Catphan500).150mA, Pitch:1.375, tube voltage:80、100、120、140kV. The image quality was evaluated by CT linearity、high resolution、low contrast、 uniformity、noise in PACS. CTDIw and CTDIvol were calculated under the scan conditions mentioned above by head dose module. The relationship between CT image quality and CT dose was also estimated.Results:As the increase of tube voltage, CT dose have linear increase trend.The high resolution was not affected by tube voltage. Howerer, the uniformity was improved with the increase of the tube voltage, as well as the low contrast of CT image. But with the increase of the tube voltage, the noise of CT image decreased by exponential law. The CT linearity changed with tube voltage.Conclusions:CT dose varied with tube voltage in some disciplines. Some index of CT image quality declined with X-Ray tube voltage decreasing. However, the radiation dose by PET/CT could be decreased appropriately under the guarantee of the quality of the CT image.