Feasibility Study Of Navigator-Gated 3D Delayed-Enhancement And 2D DIR FSE Black-Blood Cardiac MRI

Part 1Feasibility Study of PAWS Algorithm Navigator-Gated 3D DE-MRI of Infarcted Myocardium Compared with Breathhold 2D DE-MRIPurpose:To evaluate the feasibility of navigator-gated three-dimensional (3DNAV)delayed-enhancement MRI(DE-MRI)sequence using PAWS algorithm for infarcted myocardium detection compared with standard breathhold two-dimensional(2DBH)DE-MRI sequence.Materials and Methods:Three myocardium infarction dog-models underwent 2DBH DE-MRI and 3DNAV DE-MRI(with random order) sequentially 10 to 25 minutes after contrast injection at 1.5T MR scanner. Recorded scan time of the two sequences,and evaluated the image quality.It included:(1)semiqualitative evaluation(by two experienced cardiovascular MR radiologists,independently):image quality grade(grade 0 represented being not able to diagnose,gradeâ… was poor,gradeâ…¡was good,and gradeâ…¢was excellent)and relative diagnostic confidence score(-1 represented image quality of 2DBH sequence was better,0 showed the same,and 1 indicated 3DNAV was better);(2)quantitative analysis(by two experienced cardiovascular MR radiologists with a consensus):infarct volume,infarct signal-to-noise ratio(SNR₁), viable myocardium SNR(SNR₀),and infarct-viable myocardium contrast-to-noise ratio(CNR_1-0)in slices with hyperenhanced myocardium of the two sequences. Kappa test was used to evaluate consistency of the two radiologists' evaluation of 3DNAV image quality,the correlation of their relatively diagnostic confidence score and infarct volume measurements obtained based on the two sequences was assessed by using Spearman rank correlation and Pearson linear correlation, respectively.Two-tailed paired-sample t-tests were used to assess the differences of SNR₁,SNR₀ and CNR_1-0between the two sequences.P values of less than 0.05 were considered statistically significant.Results:Good consistency(Kappa=0.532,P＜0.05)of the two radiologists' evaluation of 3DNAV image quality was obtained and the correlation of their relatively diagnostic confidence score was statistically significant (r=0.609,P＜0.05).The mean of relatively diagnostic confidence score of the two radiologists were both beyond 0.Scan time of 3DNAV sequence significantly decreased than 2DBH sequence(88.2%,62.4%and 79.5%for each dog model, respectively).And infarct volume measurements obtained based on the two sequences was significantly correlated(r=0.998,P＜0.05).SNR₁(t=-5.691,P＜0.001),SNR₀(t=-3.317,P＜0.001)and CNR_1-0(t=-6.005,P＜0.001)of 3DNAV sequence markedly improved than those of 2DBH sequence and their differences were statistically significant.Conclusion:PAWS algorithm 3DNAV DE-MRI of infarcted myocardium provides less scan time,higher imaging efficiency,improved image quality and improved myocardial infarction diagnosis and evaluation confidence in compared to the standard 2DBH DE-MRI. Part 2Feasibility Study of PAWS and SMV Algorithm Navigator-Gated 2D DIR FSE Black-Blood Cardiac MRIPart 2-1Imaging Quality Evaluation of PAWS and SMV Algorithm Double Navigator-gated 2D DIR FSE Black-Blood Cardiac MRI compared with Breathhold SequencePurpose:To assess the imaging quality of double navigator-gated 2D DIR FSE black-blood cardiac MRI with PAWS and SMV algorithm compared with breathhold sequence,and evaluate the feasibility and value of clinical application.Methods and Results:Eighteen healthy adult volunteers(male:15,female: 3,mean age:34±6 years,age range:22～49 years)underwent double navigator-gated 2D(2DNAV)DIR FSE black-blood MRI with PAWS and SMV algorithm and standard breathhold 2D(2DBH)DIR FSE black-blood MRI. Imaging parameters for the two sequences were the same and 4-slice short axial of left ventricle images were obtained for each sequence.Recorded scan time of the two sequences,and assessed the image quality.It included:(1)semiqualitative evaluation(by two experienced cardiovascular MRI radiologists,independently): image quality grade(grade 0 represented being not able to diagnose,gradeâ… was poor,gradeâ…¡was good,and gradeâ…¢was excellent)and relative diagnostic confidence score(-1 represented image quality of 2DNAV sequence was worse and unable to use to diagnose,0 showed 2DNAV image quality was not so good but was still valuable for diagnosis compared with 2DBH image,and 1 indicated the same image quality and diagnostic value of the two sequences);(2) quantitative analysis(by two experienced cardiovascular MR1 radiologists together):left ventricular myocardium signal-to-noise ratio(SNR₁),left chamber SNR(SNR₀),and left ventricular myocardium-left chamber contrast-to-noise ratio (CNR_1-0)of the two sequences.Kappa test was used to evaluate consistency of the two radiologists' evaluation of 2DNAV image quality,the correlation of their relatively diagnostic confidence score was assessed by using Spearman rank correlation.Two-tailed paired-sample t-tests were used to assess the differences of scan time,SNR₁,SNR₀ and CNR_1-0between the two sequences.P values of less than 0.05 were considered statistically significant.Results:Fifteen healthy adult volunteers of being scaned successfully with 60 corresponding slices images were enrolled in this study.Good consistency (Kappa=0.573,P＜0.001)of the two radiologists' evaluation of 2DNAV image quality was obtained and the correlation of their relatively diagnostic confidence score was statistically significant(r=0.733,P＜0.001).The mean of relatively diagnostic confidence score of the two radiologists were both beyond 0.Scan time of 2DNAV sequence slightly decreased than 2DBH sequence and their difference was statistically significant(t=-2.248,P＜0.05).SNR₁(t=-15.847,P＜0.05), SNR₀(t=-18.399,P＜0.05)and CNR_1-0(t=-14.824,P＜0.05)of 2DNAV sequence markedly decreased than those of 2DBH sequence and their differences were statistically significant.Conclusion:PAWS and SMV algorithm 2DNAV DIR FSE black-blood MRI shows advantage in poor breathhold subject cardiac imaging.Less scan time, comparable diagnostic value and no need of repeated breathhold in compared to the standard 2DBH DE-MRI indicate its value of clinical application.However, 2DNAV sequence should not be considered as the first choice of cardiac imaging of excellent breathhold subject for its lower SNR and CNR compared with 2DBH sequence. Part 2Feasibility Study of PAWS and SMV Algorithm Navigator-Gated 2D DIR FSE Black-Blood Cardiac MRIPart 2-2Demonstration Efficacy of PAWS and SMV Algorithm Double Navigator-Gated 2D DIR FSE High-Resolution Black-Blood Coronary Artery Wall MRIPurpose:To explore the demonstration efficacy of PAWS and SMV algorithm double navigator-gated 2D DIR FSE high-resolution black-blood coronary artery wall MRI and evaluate its feasibility and limitation of imaging.Methods and Results:PAWS and SMV algorithm double navigator-gated 2D(2DNAV)DIR FSE high-resolution black-blood MRI of coronary artery wall was performed in 21 healthy adult volunteers(male:17,female:4,mean age: 30±7 years,age range:22～50 years).Use navigator-gated 3D FIESTA sequence to perform the right coronary artery(RCA)and left anterior descending branch (LAD)MRA(MR angiography)and reconstruct RCA and LAD long axis images by MIP(maximal intensity projection)technique.They were used to locate the transverse plane black-blood images of middle segment of RCA and proximal or middle segment of LAD.Measure the thickness of RCA and LAD wall respectively by two experienced cardiovascular MR radiologists together and assess their difference by using two-tailed paired-sample t-tests.P values of less than 0.05 were considered statistically significant.Results:Thirty-one slices(RCA:13 slices,LAD:18 slices)were obtained for evaluation,excluding the poor quality images for some reasons.The mean thickness RCA and LAD was 0.94±0.16mm and 0.89±0.15mm,respectively.And their difference was not statistically significant(t=-0.790,P＞0.05).Conclusions:PAWS and SMV algorithm 2DNAV DIR FSE high-resolution black-blood MRI has initial value of clinical application and feasibility for manifestation of thickness measurement of coronary artery wall,but it is also limited by the relatively lower spatial resolution,SNR and overestimation of the coronary artery wall thickness.