Comparative Analysis Between Tofu-MRA And TOF-MRA In Evaluation Of Carotid Artery Stenosis

ObjectiveTo evaluate the clinical value of the time of flight with sparse undersampling MRA(TOFu-MRA)compared with the time of flight MRA(TOF-MRA)in diagnosing the carotid artery stenosis,regarding the DSA results as the gold standard.Materials and MethodsFrom May 2015 to May 2016,30 patients in our hospital were recruited consecutively(20 males,10 females,aged 28 to 70)with the symptoms of recurrent vertigo,amaurosis and limb transient activity obstacle,and they were diagnosed with carotid artery stenosis by ultrasound.All the 30 cases took the examinations of TOFu-MRA,TOF-MRA and DSA within a week successively.Sensitivity,specificity,positive predictive value,negative predictive value and Youden index of both TOFu-MRA and TOF-MRA were obtained.Through analyzing the match degree of TOFu-MRA and TOF-MRA based on the DSA results respectively,the clinical value of these two techniques were evaluated precisely.The written informed consents concerning the use of data for the purpose in this study were obtained from the patients.This study was reviewed and approved by the Ethics Review Board of our hospital.All cases were examined by using Siemens Magnetom Skyra 3.0T MR scanner(Siemens Healthcare,Erlangen,Germany)with a standard high definition receive-only multi-element(eight-elements)surface head and neck coils.The axial scan parameters of TOFu-MRA:TR/TE=21.0ms/3.43ms,Scan Time=5min07s,Voxel Size=0.3*0.3*0.4mm,Slice Thickness=0.36mm,FOV=220mm*198mm.The axial scan parameters of TOF-MRA:TR/TE=20.0ms/3.30ms,Scan Time=6min36s,Voxel Size=0.6*0.6*0.6mm,Slice Thickness=0.6mm,FOV=220mm*165mm.DSA was performed via artery catheterization by using the digital subtraction technique(Philips).Patients need preoperative preparation,exposed bilateral inguinal,regular disinfection,1%lidocaine with local anesthesia.Common carotid arteries were selectively catheterized.Images were obtained in anteroposterior,lateral,and two oblique projections for each catheterization,so can clearly display narrow vessels.Commercially available 3D software(Syngo,Siemens)was used to create maximum intensity projection(MIP)and volume rendering(VR)from the original image of the TOFu-MRA and the TOF-MRA of carotid vessels.Bilateral of internal carotid artery,external carotid artery,vertebral artery and common carotid artery were observed.MR images were evaluated independently by two radiologists with at least five years' experience.All the primary data and the MIP images of 3D TOFu-MRA and TOF-MRA were reviewed in terms of image qualityand stenosis.Two interventional radiologist with at least five years' experience assessed the stenosis on DSA.Results:1.Image qualityThere were 26 cases with excellent image quality,2 cases with good image quality and 2 cases with poor image quality of the TOFu-MRA,however,there were 22 cases with excellent image quality,3 cases with good image quality and 5 cases with poor image quality of the TOF-MRA.2.Scanning timeThe scanning time of TOFu-MRA is 5min07s,while the TOF-MRA needs 6min36s on the same condition of scanningscope.3.Diagnostic confidenceThe sensitivity ofthe TOFu-MRA indiagnosing mild,moderate,severe stenosis and occlusion were 100%,93.75%,100%and 100%,the specificity were 100%,100%,97.56%and 100%,the positive predictive value were 100%,100%,91.70%and 100%,the negative predictive value were 100%,97.30%,100%and 100%,the Youden index(%)were100%,93.75%,97.56%and 100%.The sensitivitythe TOF-MRA in diagnosing mild,moderate,severe stenosis and occlusion by TOF-MRA were 100%,75%,72.73%and 100%,the specificity were 96.88%,100%,92.68%and 93.62%,the positive predictive value were 95.2%,100%,72.73%and62.50%,the negative predictive valuewere 100%,90%,92.68%and100%,the Youden index(%)were 96.88%,75%,65.41%and 93.62%.The Kappa values between TOFu-MRA with DSA and TOF-MRA with DSA in measurement of carotid stenosis grade were 0.973 and 0.811 respectively.Conclusions1.Compared with the TOF MRA,the TOFu-MRA can provide vessel image with higher quality with shorter scan time.2.The TOFu-MRA images show higher sensitivity,specificity,positive predictive value and negative predictive value for carotid artery stenosis and occlusion than the TOF-MRA images,particularly for the moderate and serious stenosis vessels.In some cases,the TOFu-MRA can be the optimal choice for carotid arteries instead of the TOF-MRA because of its superior accurate evaluating capability.