Application Of Zero Echo Time MRA Combined With High Resolution Vessel Wall Imaging In The Follow-Up Of Intracranial Aneurysms After Stent Implantation

Objectives: To explore the clinical value of high resolution vessel wall imaging sequence(3DT1-CUBE)combined with zero-echo time magnetic resonance angiography(ZTE-MRA)in the follow-up of intracranial aneurysms after stent implantation.The purpose of this paper is to effectively reduce the metal artifacts caused by stents and coils by non-invasive image acquisition technology,display the corresponding vascular lumen and vessel wall more effectively,become the optimization and supplement of routine follow-up methods after operation and provide more choices for clinical follow-up.Methods: The imaging and clinical data of 35 patients treated with stent-assisted coil embolization and flow diverter device in the intervention room of the first affiliated Hospital of Kunming Medical University from September 2020 to November 2022 were prospectively collected.All patients were admitted to hospital regularly from 1 to 24 months after operation,and the interval between magnetic resonance imaging and cerebral angiography was less than 1 week.First of all,the3DT1-CUBE,ZTE-MRA and TOF-MRA image quality of the stent-segment parent artery of each patient was subjectively scored and counted by using a 4-subscale.After that,the occlusive degree of aneurysm was evaluated by two-stage scale on ZTE-MRA and TOF-MRA images,and the patency of parent artery of stent segment was evaluated on 3DT1-CUBE,ZTE-MRA and TOF-MRA images.The above DSA and MRI images were evaluated by two interventional neuroradiologists respectively.If the evaluation results were inconsistent,the final score was given after discussion by the two experts for statistical analysis.The occlusive state of aneurysm and the patency of parent artery in stent segment were evaluated by Kappa consistency test,and the sensitivity,specificity,positive predictive value,negative predictive value and accuracy of each MRI technique were calculated.Finally,we use Image J software to draw and measure the relative value of the mean gray value of the parent artery lumen in the area where different metal coverage stents are located,and compare the impact of different metal coverage stents on ZTE-MRA image quality by objective evaluation method.Results: A total of 36 patients with 35 aneurysms were included in this study.The overall image quality of 3D T1-CUBE,ZTE-MRA and TOF-MRA of stent-segment parent arteries in all patients were scored as 3.94±0.23、3.36±0.762.47±0.74,respectively.The overall image quality of 3D T1-CUBE in all patients was significantly better than that of ZTE-MRA(Z=-3.59,P<0.001)and TOF-MRA(Z=-5.32,P<0.001).The overall image quality of ZTE-MRA was significantly better than that of TOF-MRA(Z=-5.17,P<0.001).In the evaluation of the degree of aneurysm occlusion,there were 29 cases of complete occlusion and 7 cases of incomplete occlusion on DSA.There was an extremely high consistency between DSA and ZTEMRA in detecting the embolic state of aneurysms,with a Kappa value of 0.840(95%CI:0.626-1.053),P < 0.001,the sensitivity,specificity,PPV,NPV and accuracy of ZTE-MRA were100%、93.1%、77.8%、100%、94.4%,respectively.There was a high consistency between DSA and TOF-MRA in detecting the embolic state of aneurysms,with a Kappa value of 0.645(95% CI:0.326-0.964),P<0.001,the sensitivity,specificity,PPV,NPV and accuracy of TOF-MRA were71.4%、93.1%、71.4%、93.1%、88.9%,respectively.In the evaluation of patency of parent artery in stent segment,DSA showed patency in 34 cases and stenosis in 2 cases.The weighted Kappa value of DSA and 3D T1-CUBE was 0.640(95% CI:0.188-1.092),P < 0.001,showing high consistency.The weighted Kappa value of DSA and ZTE-MRA in evaluating the patency of stent-segment parent artery was 0.455(95% CI:0.032-0.877),P < 0.001,showing moderate consistency.And the weighted Kappa value of DSA and TOF-MRA was 0.060(95% CI:-0.023-0.143),P >0.05,with no statistical significance and poor consistency.Through the simplified two-stage evaluation,the sensitivity,specificity,PPV,NPV and accuracy of 3D T1-CUBE were 100%,94.1%,50%,100% and 94.4%,respectively.The sensitivity,specificity,PPV,NPV and accuracy of ZTE-MRA were 100%,88.2%,33.3%,100% and 88.9%,respectively.The sensitivity,specificity,PPV,NPV and accuracy of TOF-MRA were 100%,44.1%,9.5%,100% and 47.2%,respectively.The relative values of the mean gray level of the parent artery lumen generated by ZTE-MRA at the stents with metal coverage ≥ 30%and < 30% were 1.35 ±0.12 and 1.33 ±0.13,respectively,and there was no significant difference between the two groups(t=0.629,P=0.534)。Conclusions:1.In the postoperative follow-up of patients with intracranial aneurysms treated with stent-assisted coil and flow diverter,ZTE-MRA images are less affected by metal artifacts than TOF-MRA,and can well evaluate the state of aneurysm lumen occlusion and signals around aneurysms.2.3D T1-CUBE sequence shows higher diagnostic performance than MRA in evaluating the patency of parent arteries.3DT1-CUBE combined with ZTE-MRA sequence can be used as a routine way of follow-up after intracranial aneurysm stent implantation,which can significantly reduce traumatic DSA follow-up.3.3DT1-CUBE images are less affected by metal artifacts than MRA in displaying the visualization of stent-segment parent arteries.Both 3DT1-CUBE and ZTE-MRA images can better evaluate the lumen signals in stents,and stents with different structural components and metal coverage have little effect on image quality,so they can be widely used in the follow-up of various types of intracranial stents.