ABSTRACT
Objective:To explore the influence of region of interest(ROI)size on signal-to-noise ratio(SNR)measurement during the test of magnetic resonance(MR)quality control(QC),so as to provide references for selecting ROI in conducting SNR measurement during MR QC test.Methods:According to the national health industry standard"Specification of image quality test and evaluation for medical magnetic resonance imaging(MRI)equipment"(WS/T 263-2006),this study utilized Magphan SMR170 performance test phantom(abbreviation:SMR170 phantom)to perform QC test on MR equipment after conducted three times tests.The slices of SNR measurement were selected on the obtained QC images,and 41 circular ROIs,which were incremental from 200mm2 to 4200mm2 as 100mm2,were sequentially chosen in the central region of the images on the SNR slices.The SNR was calculated according to formula,and then,the SNR curve that changed with the increasing of ROI size was formed.Finally,the influence of ROI size on SNR was obtained.Results:In conducting the QC test for MRI equipment by SMR170 phantom,the influence of the selected ROI size of central region of image on SNR was significant.The SNR fluctuation could not be really reflected when ROI>1000mm2 because the basically stable SNR leaded to the SNR change could not be timely found.When ROI<1000mm2,the signal means slowly increased with the increasing of ROI size,and the increase amplitude of noise was larger,and the SNR faster decreased and was smaller and smaller with ROI increase,and it tended towards stability at finally.Conclusion:When SMR170 phantom is used to conduct QC test for MR equipment and SNR is measured,it is recommended to select≤1000 mm2 of ROI size of the central region of the images,and to choose the same ROI for each measurement,which can really reflect the SNR change and ensure the result of each measurement has comparability.