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Objective@#To analyze the absorptive radiation dose of non-target sensitive organs under the NewTomVGi oral and maxillofacial cone-beam CT scanning in different view fields.@*Methods@#The thermoluminescence dosimeter chip was placed in the non-target sensitive organ of the simulated radiology head model, and 6 scanning fields were measured and analyzed (standard resolution: scanning range was 15 cm×15 cm, 15 cm×12 cm, 12 cm×8 cm, 8 cm×8 cm respectively). High definition resolution: the radiation absorption dose of thermoluminescence with the scanning range of 12 cm×8 cm, 8 cm×8 cm, respectively.@*Results@#Under the same resolution, the absorptive dose increased with the expansion of scanning field, and the amount of absorbent during high resolution scanning was higher than that during the standard resolution with the same scanning field.@*Conclusions@#New TomVGi oral and maxillofacial cone-beam CT has sighificant difference in radiation dose in different view fields. The appropriate view field should be selected according to the patient′s clinical needs, so as to reduce unnecessary radiation dose during medical imaging examination.
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Objective:Rudimental contrast media in the subclavian vein often influence the display of carotid on dual-source computer tomography angiography.This article aimed to investigate this influence,and find a best solution.Methods:One hundred patients were randomly divided into Groups A(n=52) and B(n=48).The former received traditional imaging,with 65 ml contrast media,4.0 ml/s injection flow and caudocranial scanning direction,while the latter kept all the parameters unchanged except the scanning direction,from caudocranial to craniocaudal.Each group was graded by original axial images,maximum intensity projection(MIP),silhouette images and VR images for vascular delineation of the carotid.Results: The carotid artery was clearly displayed in Group B,while the subclavian vein was unsatisfactorily revealed in Group A,with statistically significant differences in extent scores between the two groups(P
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Objective To probe into the optimization of scanning parameters of chest with low-dose spiral CT.Methods The phantom was scanned with different scanning parameters.The image quality obtained with the standard dose parameters and the low-dose technique were compared to evaluate the spatial resolution,low contrast resolution,noise level field uniformity and radiation dose,then the optimal scan parameters were defined.The scanning parameters were 120 kV,0.75 s,Pitch 1.0,FOV 360,RF3 reconstruction model(standard filter).Different thickness and tube electricity were used and the data were analyzed with the statistical method.Results There was significant difference about the data of the CTDI between the 160 mA conventional spiral CT and the low dose groups(30 mA,50 mA,70 mA,90 mA).There was no significant difference about the CTDI between 30 mA and 50 mA,and between 50 mA and 70 mA.There was obviously significant difference about the image noise on 1 mm slice and 10mA with other groups.The spatial resolution and low contrast resolution increased along with the increase of tube electricity,and 50mA was a inflexion of low contrast resolution.Conclusion 50mA and 5mm slice are the best scanning parameters in low-dose lung scanning and adapt to routine screening and early lung cancer screening.
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Objective To analyze and discuss how the scanning parameters influence the quality of dual source CT(DSCT) images by the various settings and the corresponding scans.Methods Testees were scanned with corresponding settings of scanning parameters in SOMATOM Definition DSCT produced by SIEMENS and then the results were analyzed and discussed.Results Parameters in relation with the quality of DSCT images could be influenced by the settings of corresponding scanning parameters.Conclusion The settings of scanning parameters have close relationship with the quality of DSCT images,and sometimes one kind of setting can improve image quality in one field but depress image quality in another field,so all factors should be considered synthetically.[Chinese Medical Equipment Journal,2008,29(2):102-104]