Accuracy Of ZTE ASL MRA Versus TOF-MRA For Diagnosis Of Intracranial Artery Stenosis

ObjectiveThis study sought to evaluate the image quality and diagnostic accuracy of ZTE ASL MRA versus TOF-MRA in patients with intracranial artery stenosis,with invasive digital subtrac-tion angiography(DSA)as the reference standard.MethodsIn this study,twenty-five patients(11 male,14 female;range: from 48 to 80 years;mean age±SD;60.8±7.4years)underwent TOF-MRA due to transient ischemic attack or stroke from November 2017 to November 2018.ZTE ASL MRA was performed within two days after the TOF-MRA examination.For the next two days,patients who performed DSA for further confirming the disease or treatment were included in the research.Twenty-six arterial segments were analysed for each patient.For all imaging modalities,the North American Symptomatic Carotid Endarterectomy Trial(NASCET)criteria were used for stenosis calculations: [(Dn-Ds)/Dn]/100,where Dn is normal diameter distal to the stenotic lesion and Ds is stenosed diameter.Vascular stenosis was graded using 5-point grading scale as follows: normal(0～9%),mild(10～29%),moderate(30～69%),severe(70～99%),or occluded(no flow detected).Diseased vessels were defined as those whose NASCET stenosis rates fell into the moderate,severe,or occluded categories.Four-point Likert scale was used for subjective image quality evaluation: one score(vascular segment was not assessable due to arterial segments was not visible or severe image artifacts);Two score(vascular segment was poorly visible with substantial artifacts impairing the diagnostic image quality);Three score(vascular segment was sufficient to assess with slight artifacts);Four score(excellent arterial segment for assess with none to minimal artifact).MRAs were evaluated by two observers with more than five years’ working experience using dual-blind method.In case of disagreement,unblinded consensus readings were obtained for all discre-pancies.The image quality between ZTE ASL MRA and TOF-MRA were compared using the Mann–Whitney U.Sensitivity and specificity of ZTE ASL MRA and TOF-MRA for diseased v-essels were compared using the Mc Nemar-test.Agreement regarding the image quality and detection of stenosis between observers was assessed using Kappa-statistics.ResultsOf 650 segments in 25 patients,138(One score:100 segments;Two score: 38segments)and 105(One score: 71 segments;Two score: 34 segments)inconclusive segments were excluded from ZTE ASL MRA and TOF-MRA analysis respectively because of vascular segments was not visible or poorly visible with substantial artifacts impairing the diagnostic image quality.The DSA results were available for 506 of the remaining segments.The Mann–Whitney U test shows that TOF-MRA’s overall subjective image quality was rated better than ZTE ASL MRA(Z=-5.131,P<0.001).The sensitivity,specifi-city and accuracy of ZTE ASL MRA for diseased stenosis were 90.7%,97.6% and97.0%,respectively,similar to those of TOF-MRA(93.0%、96.8% and 96.4%,respectively).Mc Nemar-test shows that no difference between the diseased segments detection rates of ZTE ASL MRA and TOF-MRA(P=0.307>0.05).Interobserver agreements in ZTE ASL MRA and TOF-MRA were good to good for the assessment of overall subjective image quality: ZTE ASL MRA(κ=0.668,P<0.05)and TOF-MRA(κ=0.625,P<0.05).Both interobserver agreements regarding the detection of any stenosis in ZTE ASL MRA and TOF-MRA were good: ZTE ASL MRA(κ=0.660,P<0.05)and TOF-MRA(κ=0.653,P<0.05).ConclusionsThe image quality of TOF-MRA is better than ZTE ASL MRA,but no difference was obse-rved for the diagnosis of intracranial artery stenosis.ZTE ASL MRA can be used as a non-contr-ast enhanced MRA technique for the precise evaluation of vascular stenosis,especially for noise-averse patients.