The Value Of 3D-SPACE Sequence High-resolution MRI In The Follow-up Of Intracranial Artery Stenting

BackgroundIn-stent restenosis(ISR)is the most common and urgent clinical problem after stenting.Especially intracranial ISR is closely related to transient ischemic attack(TIA)and stroke after stenting.Therefore,regular follow-up is often required to monitor the occurrence of ISR for early intervention.However,due to the limitations of stent interference and intracranial anatomy,the choice of imaging methods to follow-up the intracranial artery stents is still controversial.At present,the main imaging follow-up methods include magnetic resonance angiography(MRA),high resolution magnetic resonance imaging(HRMRI),CT angiography(CTA),transcranial Doppler ultrasound(TCD),optical coherence tomography(OCT),digital subtraction angiography(DSA).(DSA)and so on,but these methods have various limitations.Combined with the mechanism of ISR in peripheral artery stents,it is related to the excessive inflammation of arterial wall and intimal hyperplasia.Because intracranial artery is not easy to obtain pathological results,it can only be analyzed by imaging.Therefore,the imaging examination method combining intravascular stent imaging and wall imaging will be the trend of research and development in the future.HRMRI can evaluate the wall condition by different sequence and signal changes before and after enhancement.Based on this advantage,the application of HRMRI to intracranial artery stents has been carried out,but its clinical value is limited due to the limitations of HRMRI scanning range and thickness.As the three-dimensional HRMRI,the three-dimensional sampling perfection with application optimized contrasts using different flip angle evolutions(3D-SPACE)sequence can not only perform high-resolution imaging of the tube wall,but also perform thin-layer scanning.The axial,sagittal and coronal images are reconstructed in any plane,and the enhancement of the whole length is fully displayed.It may be of great value to analyze the enhancement characteristics of intracranial artery stent segment and the wall at both ends of stent.But the application of 3D-SPACE sequence in the follow-up of intracranial artery stents has not been reported now.The purpose of this study is to investigate three aspects:(1)the imaging value of 3D-SPACE sequence for different types and locations of intracranial stents;(2)the assessment of intracranial stent stenosis and ISR enhancement characteristics by 3D-SPACE sequence;(3)the multi-factor analysis of intracranial ISR and wall enhancement by 3D-SPACE sequence.To evaluate the related factors of intracranial ISR and wall enhancement.Part 1 The value of 3D-SPACE sequence for different intracranial stents ObjectiveTo explore the imaging value of 3D-SPACE sequence for different materials,design types and different position of intracranial stents.MethodsRetrospectively included 44 patients who underwent stent implantation for intracranial atherosclerotic stenosis in Department of Neurointervention of our hospital from April 2017 to October 2018.All patients underwent 3D-SPACE sequence examination,including 30 males and 14 females,aged from 34 to 75 years,with an average age of 57.21 + 9.61 years.The 3D-APCE sequence images were double-blindly read by two physicians to classify the image quality,and the image quality of different materials,design types and different position stents on the 3D-SPACE sequence was analyzed.Results44 stents were implanted in 44 patients,and 1 patient was excluded due to stent occlusion.Only images of 43 patients were analyzed.The images were divided into groups according to the stent material: 3 cases of stainless steel stent,40 cases of Nitinol stent,and 3 cases of full-course metal artifacts of the MRI image of stainless steel stent,with the image quality of grade 1,and the image quality of Nitinol stent group was grade 2 or grade 3.According to stent design,40 cases of nickel-titanium alloy stent were divided into open-loop stent group and closed-loop stent group.The analysis of image quality showed that there was no significant difference between the two groups(P=1.000,P>0.05).Similarly,40 cases of nickel-titanium alloy stents were divided into anterior circulation group and posterior circulation group according to the position of stents.Statistical analysis showed that there was no significant difference in image quality between the two groups(P=0.457,P>0.05).Conclusion3D-SPACE sequence magnetic resonance imaging can be used as a non-invasive imaging method to follow up the intracranial nickel-titanium alloy stents.In terms of imaging quality,3D-SPACE sequence has better imaging quality for stents of different design types and different positions.Part 2 The value of 3D-SPACE sequence in the demonstration of intracranial ISR and wall imagingObjectiveTo explore the clinical value of 3D-SPACE sequence in the demonstration of intracranial ISR and wall imaging.Methods 39 patients with intracranial atherosclerotic stenosis after stent implantation from April 2017 to October 2018 were collected.All patients were followed up with DSA and 3D-SPACE sequence examination,or 3D-SPACE sequence examination within one week after stent implantation.DSA and MRI images were read by two physicians,and the degree of stenosis in stents was measured by Warfarin-Aspirin Test(WASID).Intra-group correlation coefficient(ICC)was used to evaluate the consistency of DSA and 3D-SPACE measurements between two physicians.DSA was used as the "gold standard" to evaluate the sensitivity,specificity,positive predictive value and negative predictive value of 3D-SPACE sequence measurements,which were divided into ISR group and non-ISR group according to the degree of stenosis.The difference of stenosis degree between 3D-SPACE sequence and DSA was compared by Wilcoxon Matched-Pairs Signed-Ranks Test.The in-stent restenosis images were typed,and the DSA and 3D-SPACE sequences were compared to measure the range of the lesions,and the value of the 3D-SPACE sequence in the wall imaging after stenting was preliminarily evaluated.Results The consistency of the results between the two physicians was well evaluated.The ICC value of DSA was 0.914(P<0.01),and that of 3D-SPACE sequence was 0.887(P < 0.01).Compared with DSA,the sensitivity,specificity,positive predictive value and negative predictive value of 3D-SPACE sequence in diagnosis of stent stenosis were 100.0%,91.3%,88.9%,and 100.0%,respectively.The average degree of stenosis in the stent was(49.7±24.1)% in DSA,and(50.1±24.4)% in the 3D-SPACE sequence.The difference was not statistically significant(Z=-1.501,P=0.133).15 cases of ISR images confirmed by DSA were analyzed.It was found that the enhancement range of 2 cases of Neuroform stents on 3D-SPACE was larger than that of DSA,and the other 6 cases were consistent with restenosis.In 8 cases of Neuroform stent restenosis,3 cases showed diffuse enhancement on the 3D-SPACE sequence.Conclusion The 3D-SPACE sequence is consistent with DSA in the diagnosis of intracranial nickel-titanium alloy stent ISR,but whether the in-stent enhancement features have clinical guiding value or not can not be concluded at present.It needs to be prospective,large sample and long-term follow-up.