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Influence of Different ROI Extraction Methods to the Measurement of Glomerular Filtration Rate in Gates′ Method

WANG Chang-yin,WEN Bin,ZHANG Xiang-yuan.Department of Nuclear Medicine,Zhong Nan Hospital,Wuhan University,Wuhan 430071,P.R.China  
Objective:To investigate the influence of different kidney and background region of interest (ROI ) extraction methods to the measurement of glomerular filtration rate (GFR) in Gates′method.Methods:Dynamic renal imaging was performed in forty-one patients;GFR was obtained using different ROI extraction methods.After changing the position,size of background ROI,the distance between background ROI and kidney ROI,the magnitude and local deviation of kidney ROI,the variation of GFR were studied.Each of the GFR variation was compared with standardized GFR in Gates′ method,to learn the degree of variation and factors leading to these variations.Results:① Study by logistic regression,it was demonstrated that the position and size of background ROI,distance between background ROI and that of kidney,magnitude and local deviation of kidney ROI were all important factors in influencing GFR (χ2 was 250.9,73.9,53.5,215.8 respectively,P=0.000).②Measured GFR was very much similar to the standardized one in Gates′ method when background ROI was put just beneath the kidney in a large dimension or the kidney ROI was deviated to the outer-inferior direction.A relative obvious influence was showed in the other changes of background ROI and kidney ROI.Conclusion:① Various factors must be considered when ROI is extracted in Gates′ method;② The influence of the size、distance of back ground ROI can be reduced by drawing background ROI just beneath the kidney in a pixel size of 20~160 and in a pixel distance of 0~16.
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