Evaluation Of Magnetic Resonance Diffusion-weighted Intravoxel Incoherent Motion Imaging In Liver Based On ECG-triggered Technique

ObjectiveTo evaluate the image quality,the reproducibility of apparent diffusion coefficient and IVIM related parameters measurements on the magnetic resonance diffusion-weighted intravoxel incoherent motion imaging with electrocardiograph-triggered.On the basis of that to evaluate the diagnostic value of IVIM-DWI based on ECG gating in clinical liver disease.MethodsExperiment one:A total of 116 volunteers were enrolled in the IVIM-DWI scan with six b values(b = 0,50,100,150,300,600s/mm2)from May 2015 to December 2015.Those subjects were divided into 2 groups according to the heart rate.The heart rate of the subjects in the low heart rate group was less than or equal to 70 bpm,while of the high heart rate group subjects was≥80 bpm.The single exponential linear function model and the double-exponential nonlinear model were used to fit the full liver IVIM-DWI images,and the mean ADC images and the D,D*and f value pseudo color parameter charts were obtained.In this study,three consecutive 100 mm2 round ROIs were placed on the left and right leaves of the selected level.The ADC values and the D,D*and f values of the left and right liver lobe were the mean values of the nine ROIs,followed by statistical analysis of these data.Experiment two:A total of 21 volunteers were selected during the period from May 2016 to June 2016.Each volunteer was performed twice IVIM-DWI exams with six b values(b=0,50,100,150,300,600s/mm2).The free breath and free breath combined with electrocardiograph-triggered were used in the scanning process to collect 5 layers of liver IVIM-DWI images.Three 100 mm2 area ROIs were placed in the left and right lobe of the liver and in the backgrounds,respectively.Then the corresponding signal intensity(SI)and signal noise were obtained to calculate the signal-to-noise ratio.The mean ADC,D,D*and f value of liver were obtained by the method of experiment one.The paired t test,Pearson Correlation Coefficientwas analysis and the correlation coefficients(ICCs)were used to evaluate the consistency evaluations of the two measurements.The Bland-Altman method was used to evaluate the consistency of ADC,D,D*and f measurements obtained by two scans.The mean SNR,ADC,D,D*and f value of left and right lobe of the two techniques were statistically analyzed.Experiment three:A total of 66 patients(including 84 lesions)who were diagnosed of focal liver lesions and had routine abdominal MR examination and IVIM-DWI examination with free breath and free breath combined with electrocardiograph-triggered with six b values(0,50,100,150,300,600s/mm2)in Panyu Center Hospital of Guangzhou were collected from June 2006 to December 2016.Three 100 mm2 area ROIs were placed in the left and right lobe of the liver and lesions and abdominal wall,respectively.The SNR and CNR were calculated.The mean ADC,D,D*and f value of the lesions were obtained by placing ROIs on the maximum lesion level.The SNR,CNR and ADC,D,D*and f values of free breath and free breath combined with electrocardiograph-triggered were analyzed by paired t-test.ResultsExperiment one:(1)The ADC,D and f measurements of the left hepatic lobe of the low heart rate group and the high heart rate group were higher than the right hepatic lobe(P<0.05).(2)The mean ADC,D and f measurements of the left hepatic lobe of the low heart rate group were lower than those of the high heart rate group(P<0.01).(3)The mean ADC and f measurements of the right hepatic lobe of the low heart rate group were lower than those of the low heart rate group(P<0.05).Experiment two:(1)The SNR measurement of left and right hepatic lobes with free breath combined with electrocardiograph-triggered were higher than those of free breath,and the difference was statistically significant(P<0.05).(2)The ICC range of twice measurements,the ADCs,D,and f values of the left and right lobes had well consistent(left:0.869 to 0.987;right:0.776 to 0.980).The D*values of left and right liver lobe were poor(left:0.153 to 0.846;right:0.312 to 0.574).(3)The two scan measurement repeatability of the ADC,D and f values of the left hepatic lobe with free breath combined with electrocardiograph-triggered were better than that of the free breath,the repeatability of f value was the best(LOA was 0.03%).The two scan measurement repeatability of D*values were poor than free breath(LOA was 20.95%).The two scan measurement repeatability of the ADC,D*,f of the right hepatic lobe with free breath combined with electrocardiograph-triggered were poor than that of free breath,the repeatability of D*was the worst(LOA:14.75%).The repeatability of f value was better than free breath(LOA:0.03%).In all IVIM-DWI parameter values,the repeatability of D*value was the worst.(4)The ADC,D measurements of left hepatic lobe that were obtained with different acquisition techniques were greater than the right hepatic lobe(P<0.01);the D*values of the left hepatic lobe were less than right hepatic lobe(P<0.01);the f values of the left hepatic lobe were greater than the right lobe of the liver,but the difference was statistically significant only in free breath condition(P<0.01).(5)The measuerments of ADC,D,f of the left and right hepatic lobe with free breath combined with electrocardiograph-triggered were lower than the free breath(P<0.05).There was no significant difference in the D*of left liver lobe(P=0.464).There was no significant difference in the D(P=0.781),D*(P=0.161)of right liver lobe.The difference of ADC,f value(P<0.01)of the right liver lobe had statistically significant.Experiment three:(1)The liver IVIM-DWI image SNR,contrast to noise ratio that were obtained with free breath combined with electrocardiograph-triggered were higher than that of free breath(P<0.001).(2)The values of ADC and IVIM parameters of liver benign lesions under both conditions of two techniques were higher than those of liver malignant lesions,and the difference was statistically significant(P<0.05).(3)The values of ADC and IVIM parameters of liver benign and malignant diseases which were obtained by free breath combined with electrocardiograph-triggered were lower than that of free breath,and there was no significant difference in D*between the two groups(P=0.073).Conclusion(1)Proper control and reduction of heart rate can reduce the motion artifacts of liver IVIM-DWI image,resulting in relatively accurate parameter values,especially in the left lobe of the liver.(2)In IVIM-DWI imaging,the image quality of liver would be significantly improved by free breath combined with electrocardiograph-triggered technology,improving the image SNR,especially when the heart rate is below 70bmp,the liver image could have high signal-to-noise ratio,clear focus and good image quality.(3)Free breath combined with electrocardiograph-triggered technology influence the ADC and IVIM parameters measurement and its repeatability.The left hepatic lobe is affected more obviously,and the stability is better.(4)The ADC,D,D*,f values can be used for the identification of benign and malignant lesions of liver.Considering that the repeatability of D*is poor,it would have a high measurement error,it is recommended that clinical use should be cautious.