Application Of 3D T1-SPACE High Resolution MR Vessel Wall Imaging In The Follow-Up Of Cerebral Artery Stenting

Background:At present,endovascular treatment has become one of the important methods for the treatment of cerebrovascular diseases.Among them,stent has been widely used in the field of neurointervention,especially in the treatment of intracranial atherosclerotic stenosis and cerebral aneurysm.However,in-stent restenosis and delayed thrombosis may occur in some patients after intracranial stenting.Therefore,it is necessary to have regular imaging examination after stenting.Digital subtraction angiography(DSA)is the "gold standard" of imaging examination after endovascular treatment,but it is an invasive examination with certain radiation,so it is difficult for patients to accept longterm repeated examination.Traditional magnetic resonance angiography(MRA)technology including three-dimensional-time of flight magnetic resonance angiography(3D-TOF MRA)or contrast-enhanced magnetic resonance angiography(CE-MRA)has no radiation exposure,simple operation,and is widely used in clinical practice.However,due to the metal artifacts of stent itself and the shielding effect of stent magnetic field,it is easy for conventional MRA to mistake for the false stenosis or occlusion of stent vessels when displaying stent lumen.In recent years,threedimensional T1-sampling perfection with application-optimized contrasts using different flip angle evolutions,3D T1-SPACE(3D T1-SPACE)has emerged,which can provide three-dimensional,large-scale,high spatial resolution imaging of intracranial vessel at the same time.At present,it has been applied to the imaging of intracranial artery wall,and achieved good results.Therefore,this study used 3D T1-SPACE highresolution wall imaging technology to follow up intracranial artery stents,in order to explore its application value in intracranial atherosclerotic stenosis and intracranial aneurysm stenting.Part 1 Preliminary study of 3D T1-SPACE combined with 3D-TOF MRA in the follow-up for the intracranial aneurysm treated with Pipeline Flex embolization deviceObjective:To evaluate the 3D T1-SPACE in combination with 3D-TOF sequence for followup of intracranial aneurysms treated with Pipeline embolization devices.Methods:Forty patients with 53 intracranial aneurysms who were treated with Pipeline Embolization Devices(PED)in People’s Hospital of Zhengzhou University from October 2018 to July 2019 were enrolled in this study.All patients were evaluated for aneurysm occlusion and stent patency 4 to 7 months post-treatment using 3D T1SPACE sequence,3D-TOF MRA,and DSA examinations.Magnetic resonance and DSA images were independently read by two interventional neuroradiologists.When a different reading was proposed,consensus was found after an intensive discussion between the two neuroradiologists.And the Kendall’s coefficient test was used to test the consistency of the DSA and MRI results between the two neuroradiologists.O’kelly-Marotta(OKM)classification was used to evaluate the aneurysm residual and the four-point scale was used to evaluate the in-stent lumen visibility.The κ statistic was used to analyze the aneurysm occlusion between DSA and 3D TOF-MRA,and Wilcoxon singed rank test was used to analyze the quality of parent artery images after the stent implantation.P<0.05 were considered statistically significant.DSA was used as the reference standard to calculate the specificity and total coincidence rate of the aneurysm occlusion degree evaluated by 3D TOF-MRA after the PED implantation.Results:The Kendall’s coefficient between the 2 neuroradiologists in evaluating the aneurysms occlusion status in DSA,aneurysms occlusion status in 3D-TOF MRA,the parent artery pantency in 3D T1-SPACE sequence and the parent artery pantency in 3D-TOF MRA were 0.988,0.892,0.807,and 0.901,respectively,all P<0.001.With regards to aneurysm occlusion,the intermodality(DSA and 3D-TOF MRA)agreement was good(κ=0.755).The sensitivity of 3D-TOF MRA combined with source images to evaluate aneurysmal lumen was 76.5%(13/17),the specificity was 94.4%(34/36),the total coincidence rate was 88.7%(47/53).With regards to the patency of the stented arteries after PED treatment,3D T1-SPACE sequence was more accurate compared to 3D-TOF MRA(Z=-6.283,P<0.001),with a no-artifact rate of 95.7%(44/46).Conclusion:3.0T 3D-TOF MRA can evaluate the aneurysm residual.3D T1-SPACE sequence provides better image quality and higher accuracy for evaluating stented parent arteries compared to TOF-MRA.The combination of these two modalities may be used for long-term follow-up of intracranial aneurysms treated with Pipeline Embolization Devices.Part 2 Application of 3D-SPACE combined with 3D-TOF sequence in the follow-up of stentassisted coil embolization for intracranial aneurysmObjective:To assess 3D T1-SPACE combined with 3D-TOF sequence for follow-up evaluation of stent-assisted coil embolization for intracranial aneurysm.Methods:From December 2017 to October 2018,25 patients with intracranial aneurysm who underwent stent□assisted coil embolization in People’s Hospital of Zhengzhou University were prospectively enrolled.All of them were followed up for 6 to 10 months after endovascular treatment using 3D□TOF MRA,3D T1□SPACE sequence and DSA.Magnetic resonance and DSA images were independently read by two interventional neuroradiologists.When a different reading was proposed,consensus was found after an intensive discussion between the two neuroradiologists.And the Kendall’s coefficient test was used to test the consistency of the DSA and MRI results between the two neuroradiologists.The DSA and 3D□TOF MRA were performed to evaluate aneurysm remnants using Raymond grade scale.3D□TOF MRA and 3D T1□SPACE sequence were performed to evaluate in□stent lumen visibility using the 4□point scale.The Wilcoxon paired singed rank test was used to analyze the aneurysm remnants evaluated by 3D□TOF MRA and DSA,and the parent artery patency evaluated by 3D□TOF MRA and 3D T1□SPACE.DSA was used as the gold standard to calculate the specificity and accuracy of the aneurysm remnants evaluated by 3D□TOF MRA.Results:The Kendall’s coefficient between the 2 neuroradiologists in evaluating the aneurysms occlusion status in DSA,aneurysms occlusion status in 3D-TOF MRA,the parent artery pantency in 3D T1-SPACE sequence and the parent artery pantency in 3D-TOF MRA were 0.957,0.841,0.876,and 0.688,respectively,all P<0.05.Taking DSA as standard,the specificity of 3D-TOF MRA was 86.9%(20/23)and the accuracy was 84%(21/25).For aneurysm occlusion,the Raymond grade scale of the 25 patients evaluated by DSA indicated grade 1 in 23 patients,2 in 1 and 3 in 1.For patients evaluated by 3D□TOF MRA,the results demonstrated grade 1 in 21 patients,2 in 3 and 3 in 1.There was no statistical significance between the 2 methods(Z=-0.557,P=0.577).The in□stent lumens of parent vessel evaluated by 3D□TOF MRA showed that there were 14 patients with grade 3,8 patients with grade 2 and 3 patients with grade 1.However,3D T1□SPACE demonstrated that all 25 patients were grade 4.The 3D T1□SPACE was superior to evaluate the in □stent lumens than 3D□TOF MRA(Z=-4.484,P<0.001).Conclusion:3.0T 3D T1-SPACE sequence provides better image quality and higher accuracy for evaluating stented parent arteries compared to TOF-MRA.This study also shows that 3D-TOF MRA has a merit to evaluate aneurysm occlusion.The combination of these two modalities can be used as an optional follow-up evaluation after endovascular treatment of intracranial aneurysms.Part 3 Application of 3D T1-SPACE Vessel Wall Imaging in the follow-up after stent implantation for intracranial arterial stenosisObjective:In-stent restenosis after stenting for intracranial stenosis is a significant issue.This study aimed to evaluate the value of the 3D T1-SPACE vessel wall imaging technique in the follow-up of patients after stent implantation.Methods:Fifteen patients with intracranial arterial stenosis were prospectively enrolled 6 to 8 months after stenting from April 2017 to June 2018 at People’s Hospital of Zhengzhou University.Digital subtraction angiography(DSA)and 3D T1-SPACE were performed to evaluate the degree of in-stent lumen stenosis and the enhancement of the vessel wall.Magnetic resonance and DSA images were independently reviewed by two neuroradiologists.The intraclass correlation coefcient(ICC)was performed to assess the intrarater and inter-rater reliability.Pearson correlation analysis was used to compare the consistency of two vascular imaging techniques in measuring stenosis rate after stenting.Results:In the measurement of the stenosis rate of the target vessel,the ICC value between the two neuroradiologists was 0.996-0.999,both P<0.001.In the DSA and 3D T1SPACE sequences,the ICC values between the two neuroradiologists were 0.990 and 0.984,respectively,with all P<0.001.Seven Wingspan and eight Enterprise stents were used in 15 patients.The average stenosis rate before stent implantation was 81.60%±8.67%.The follow-up DSA after 6 to 8 months showed that the degree of stenosis was 40%(range,30%-72%),and ISR occurred in 4 of 15(26.7%)lesions.The degree of stenosis assessed using the 3D T1-SPACE imaging technique was 35%(range,30%-75%).Enhanced MRI scan revealed that enhancement of in-stent plaque was observed in five patients,among them enhancement level 2 was seen in 4 patients(all were ISR patients)and enhancement level 1 was seen in one patient.The Pearson correlation coefficient between the two methods was 0.959(p<0.05),and the BlandAltman plot showed that all data points were within the consistency limits(x±1.96s).Conclusion:As a non-invasive imaging modality,3D T1-SPACE showed great consistency with DSA in measuring the degree of stenosis after intracranial stenting.Therefore,this technique can be used in postoperative follow-up of stent implantation for intracranial artery stenosis.