ABSTRACT
OBJECTIVE@#Based on the Magphan phantom,a baseline value of low contrast resolution was established,and the stability of the imaging performance of the system was monitored.Drift and correction were found in time to give full play to the performance of the device.@*METHODS@#The general test evaluation method for low-contrast resolution was not suitable for the characteristics of long-term monitoring equipment performance changes,and the test evaluation of low-contrast resolution that incorporates the -test method in statistical principle was proposed.@*RESULTS@#By analyzing and evaluating the test results of the low contrast resolution of the standard water model image,and verifying the correctness of the evaluation method,according to the correct test method,the test statistic value was used as the low contrast resolution value of the MRI equipment to test the boundary of the region.The value was used as a baseline value for low contrast resolution to establish a long-term stable quality assurance system.@*CONCLUSIONS@#In this paper,the data of the low contrast resolution test on Magphan phantom was in line with practical experience,therefore the test method of low contrast resolution was verified.The baseline value of the indicator can be established based on the detection and evaluation method of low contrast resolution based on phantom,then to ensure the stability of the imaging performance of the system.
Subject(s)
Contrast Media , Magnetic Resonance Imaging , Phantoms, ImagingABSTRACT
Objective To explore the feasibility and reasonable of low-dose scan on abdominal angiography in 64-slice spiral helical CT. Methods Phantom test: at 120 KV and from 200 mAs to 30 mAs at an interval of 10 mAs in each image acquisition, it was measured standard deviation (SD) of CT number, high contrast resolution and low contrast resolution, and then analyzed the relationship between the three parameters and the mAs values. Three mAs values were chosen to undertake clinical analysis.Clinical analysis: 90 randomly selected objects with abdominal angiography were divided into three groups,scanning with above three mAs values.Measurement of the SD value at the plain scan images was performed and the enhanced low-dose scan images were used post-processing with three-dimensional volume reconstruction (VR). The VR images were classified into three grades (excellent, moderate, bad) with the blind evaluation of three CT radiologists. The quality-correlation analysis was used between the standard deviation (SD) values of plain scan image and abdominal angiography VR image. Results According to the quality-correlation analysis between the standard deviation (SD) value of plain scan image and abdominal angiography VR image, the area under curve in receiver-operated characteristic (ROC) analysis was 0.921, 0.906 and 0.893 in each three group, respectively. Conclusions The low-dose scan of abdominal angiography is feasible. 80mAs can ensure better image quality. The enhanced scan probably can use 60mAs when the SD value is less than 5.78 in the plain scan; but when the SD value of plain scan is greater than 11.8, the enhanced scan is used best 100 mAs or higher.