Application Of 3.0T Cardiac Magnetic Resonance Imaging In Pediatric Myocarditis

Part ⅠThe impact of dual-source parallel radiofrequency transmission with patient-adaptive shimming on the pediatric cardiac magnetic resonance at 3.0 TPurposeThe aim of our study was to evaluate the effect of dual-source parallel radiofrequency(RF)transmission with patient-adaptive shimming on the B1 homogeneity and image quality of pediatric cardiac magnetic resonance(CMR)at 3.0 T compared with conventional single-source RF transmission.BackgroundThe pediatric CMR scanning protocol presents a unique set of technical challenges compared with adult,because of the small cardiac anatomical structures,fast heart rates and the limited ability to keep motionless and hold breathe.High field(3.0 T)magnetic resonance with multiple signal averaging could improve spatial and temporal resolution and decrease motion artifacts,while they could cause problems associated with field inhomogeneity and degrade the image quality.Materials and Methods30 free-breathing children and 30 breath-hold children were performed CMR examinations with both dual-source and single-source RF transmission.B1 homogeneity was evaluated quantitatively using the achieved mean percentage of nominal flip angle(FA)and its coefficient of variation(CV)in B1 maps.T-test was used to compare the B1 homogeneity and contrast ratio(CR)of cine images between dual-source and single-source RF transmission.The off-resonance artifacts of cine images were evaluated independently by two experienced CMR radiologists with four-point grading scale.The scores of artifacts were compared by Mann-Whitney U test and Cohen’s kappa test was performed to evaluate the inter-observer agreement.ResultsIn both free-breathing and breath-hold groups,higher mean percentage of FA(Free-breathing group:104.2±4.6 VS 95.5±16.3,P<0.001;Breath-hold group:101.5±5.1 VS 92.5±6.3,P<0.001)and lower CV(Free-breathing group:0.06±0.02 VS 0.09±0.03,P<0.001;Breath-hold group:0.07±0.03 VS 0.10±0.04,P=0.005)were found with dual-source RF transmission compared with conventional single-source mode.All the CRs of cine images with dual-source RF transmission could be significantly improved(all P<0.05).The scores of off-resonance artifacts with dual-source RF transmission in the horizontal long axis(HLA)were higher than that with single-source mode(all P<0.05),with substantial interreader agreement(kappa values from 0.68 to 0.74).ConclusionsCompared with conventional single-source mode,dual-source parallel RF transmission could significantly improve B1 homogeneity and image quality of pediatric CMR at 3.0 T.This technology could be taken into account in the pediatric CMR scanning protocols.Part ⅡThe value of cardiac magnetic resonance in the diagnosis and prognosis of pediatric fulminant myocarditisPurposeThe aim of our study was to assess the cardiac magnetic resonance(CMR)findings of pediatric fulminant myocarditis(FM)at different course,to evaluate the short-term outcomes and to find out the predictors of short-term outcomes of pediatric FM.BackgroundFM is an inflammatory disease of the myocardium that results in severe ventricular systolic dysfunction and acute-onset heart failure.CMR has become the primary noninvasive tool for the diagnosis and evaluation of myocarditis.However,the value of CMR findings in the diagnosis and prognosis of pediatric FM was rarely reported.Materials and MethodsEight FM children with two CMR examinations were included in our study.Initial baseline CMR was performed 10 days(range,7 to 20 days)after onset of FM and follow-up CMR after 55 days(range,33 to 75 days).Cardiac morphology and function and myocardial tissue characterization at baseline and follow-up CMR examinations were compared using paired T-test and Mann-Whitney U test.The short-term outcomes of FM were evaluated from the aspect of clinical manifestations,immunological features and initial CMR findings.The clinical data and initial CMR findings between different short-term outcomes of FM children were also compared to find out the predictors.ResultsThe median age of eight FM children was 8.5 years old(range,3 to 14).The initial CMR findings were most common with early gadolinium enhancement(EGE,100%),followed by signal increasing on T2WI and late gadolinium enhancement(LGE,87.5%),increased septal thickness(75.0%)and increased left ventricle ejection fraction(LVEF,50.0%).Only three LGE(37.5%),one signal increasing on T2WI(12.5%)and one increased LVEF(12.5%)were found at follow-up.Statistically significant differences were found between initial and follow-up CMR abnormalities in the septal thickness,left ventricular end-diastolic diameter(LVEDD),end-systolic volume(ESV),LVEF,left ventricular mass,T2 ratio and LGE area(P=0.01l,P=0.042,P=0.016,P=0.001,P=0.003,P=0.011,P=0.020).Five children performed full recovery,which had higher incidence of Ⅲ° atrioventricular block(AVB,5 cases VS 0 case)and smaller LGE area(104.0±14.5 mm2 VS 138.0±25.2 mm2)at baseline CMR.ConclusionsThe CMR findings of pediatric FM were characteristic and useful for early diagnosis.Full recovery of clinical manifestations,immunological features and CMR findings could be found in most FM children.The presence of Ⅲ° AVB and smaller LGE area at baseline CMR might indicate better short-term outcomes.CMR imaging showed great value in the early diagnosis and short-term outcomes of pediatric FM.Part ⅢIdentifying myocardial injuries of "normal-appearing"myocardium in pediatric patients with clinical suspected myocarditis using mapping techniquesPurposeTo determine if T1 and T2 mapping techniques could identify diffuse myocardial injuries of "normal-appearing" myocardium in pediatric patients with clinical suspected myocarditis,and to evaluate the associations between T1 and T2 values and left ventricular(LV)cardiac function.BackgroundConventional cardiac magnetic resonance(CMR)imaging has performed considerable diagnostic accuracy in myocarditis patients with focal myocardial injuries,while the diagnostic sensitivity for diffuse myocardial injuries might be decreased.Novel CMR T1 and T2 mapping techniques offer a quantitative assessment of the myocardium and diffuse myocardial injuries in the "normal-appearing" myocardium have been reported in many myocardial diseases.Materials and MethodsWe included 46 subjects in this study-20 acute myocarditis patients(AM group),11 chronic myocarditis patients(CM group)and 15 healthy children(NC group).Linear regression analysis was used to compare T2 values,native T1 values,post-contrast T1 values and extracellular volume(ECV)of "normal-appearing" myocardium between AM,CM,and NC groups.Associations between post-contrast T1 values,ECV,and LV cardiac function were also evaluated.ResultsCompared with NC group,significantly lower post-contrast T1 values of"normal-appearing" myocardium were observed in AM group(Horizontal long axis,HLA:718.3±65.3 ms VS 776.5±62.4 ms,P=0.005;Short axis,SA:723.9±61.2 ms VS 787.7±62.3 ms,P=0.002)and CM group(HLA:693.0±77.7 ms VS 776.5±62.4 ms,P=0.001;SA:710.9±75.9 ms VS 787.7±62.3 ms,P=0.001)and higher ECV in CM group(SA:30.1±2.8 VS 27.0±2.4,P=0.004).In CM group,significant associations between post-contrast T1 values,ECV and left ventricle ejection fraction(LVEF)as well as stroke volume(SV)were found(P<0.05).ConclusionsMyocardial post-contrast T1 mapping and ECV could detect diffuse myocardial injuries in pediatric patients with clinical suspected myocarditis and are associated with LVEF and SV in pediatric CM patients.Therefore,mapping techniques could increase the overall sensitivity of CMR in the diagnosis of myocarditis,monitoring disease progression and the efficacy of therapies.