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ORIGINAL ARTICLE
Year : 2022  |  Volume : 70  |  Issue : 2  |  Page : 694-698

Clinical Study of High-Resolution C-Arm CT in Mechanical Recanalization and Stent Implantation for Chronic Cerebral Artery Occlusion


Department of Interventional Radiology, First Affiliated Hospital of Zhengzhou University; Interventional Institute of Zhengzhou University, Zhengzhou, China

Date of Submission04-Jan-2020
Date of Decision02-Apr-2020
Date of Acceptance18-May-2020
Date of Web Publication3-May-2022

Correspondence Address:
Dr. Jian-Zhuang Ren
No. 1 Jianshe East Road, Zhengzhou City
China
Dr. Xin-Wei Han
No. 1 Jianshe East Road, Zhengzhou City
China
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.344607

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 » Abstract 


Background: In recent years, among patients with chronic cerebral artery occlusion, recanalization can be achieved by an endovascular operation. However, complications and restenosis rates remain high.
Objective: To evaluate the utility of high-resolution C-arm CT (Dyna micro-CT) for stent placement in patients with chronic cerebral artery occlusion.
Methods and Materials: We retrospectively reviewed the clinical data of 27 patients with chronic cerebral artery occlusion who underwent mechanical recanalization and stent implantation. Images were reconstructed using conventional C-arm CT (Dyna CT) and Dyna micro-CT. Whether the stent was fully expanded and image quality was evaluated. Follow-up assessments included clinical and angiographic outcomes and complications.
Results: Twenty-two patients successfully underwent stenting (22 stents; 14 cases: Neuroform EZ; eight cases: Enterprise); stenting failed in five patients. Compared to Dyna CT, Dyna micro-CT afforded improved visualization of the stent structure, providing significantly improved image quality (P < 0.05). In seven patients, the stent under-expanded and dilatation was performed; thereafter, stent malapposition improved. One patient experienced sudden headache 22 hours after the procedure; CT showed intraparenchymal hemorrhage. The remaining 21 patients did not have acute thrombosis or bleeding complications and were followed up by imaging for 3-6 months. In three patients, digital subtraction angiography showed mild in-stent stenosis.
Conclusions: High-resolution C-arm CT can improve visualization of stent structures in chronic cerebral artery occlusion, making it easy to determine the extent of stent deployment and potentially reduce complications and stent restenosis.


Keywords: C-arm CT, occlusion, stents, therapeutic
Key Message: High-resolution C-arm CT can improve the visibility of intracranial stents and may be beneficial for reducing the incidence of complications in mechanical recanalization and stent implantation for chronic cerebral artery occlusion.


How to cite this article:
Li TF, Shi CC, Ma J, Fu PJ, Zhu M, Ren JZ, Han XW. Clinical Study of High-Resolution C-Arm CT in Mechanical Recanalization and Stent Implantation for Chronic Cerebral Artery Occlusion. Neurol India 2022;70:694-8

How to cite this URL:
Li TF, Shi CC, Ma J, Fu PJ, Zhu M, Ren JZ, Han XW. Clinical Study of High-Resolution C-Arm CT in Mechanical Recanalization and Stent Implantation for Chronic Cerebral Artery Occlusion. Neurol India [serial online] 2022 [cited 2022 Oct 2];70:694-8. Available from: https://www.neurologyindia.com/text.asp?2022/70/2/694/344607




Chronic cerebral artery occlusion is a major but rare cause of ischemic stroke; the main pathogenesis of the condition is watershed infarction or a transient ischemic attack[1],[2] due to occlusive stump thrombus or arteriosclerosis plaque embolism and decreased cerebral perfusion pressure. In recent years, with the improvement of interventional instruments and techniques, recanalization by endovascular operation can be achieved in some patients with chronic cerebral artery occlusion.[3],[4],[5],[6] However, complications and restenosis rates remain high due to a lack of surgical experience, non-visualization of the occlusive vascular lumen on digital subtraction angiography (DSA), unknown condition of the distal vascular bed, and unclear stent expansion at the occluded site. Dyna micro-CT is a new generation high-resolution C-arm CT developed by Siemens, Germany. Compared to conventional C-arm CT, Dyna micro-CT affords improved local spatial resolution and stent visibility.[7],[8] Therefore, this study retrospectively evaluated the utility of high-resolution C-arm CT (Dyna micro-CT) for mechanical recanalization and stent placement in patients with chronic cerebral artery occlusion.


 » Subjects and Methods Top


Ethics statement

Written informed consent was obtained from each patient for the use of the images. The study protocol was approved by the Ethics Committee of Zhengzhou University. All procedures were in accordance with the Helsinki Declaration of 1975 (and its revision in 1983).

General data

The study cohort comprised 27 patients with chronic cerebral artery occlusion (12 men and 15 women; age range: 35–69 years; mean age: 52.0 ± 8.7 years) who were treated by interventional therapy at the department of interventional radiology of the First Affiliated Hospital of Zhengzhou University (eastern district) from December 2016 to August 2018. The mean disease duration was 9.0 ± 8.7 months (range: 3–36 months). Computed tomography angiography (CTA) and/or magnetic resonance angiography (MRA) showed occlusion in the anterior circulation in 21 cases (15, two, and four cases of occlusion in the middle cerebral artery, C6 segment of the internal carotid artery, and C7 segment, respectively). The patients' initial symptoms included dizziness, numbness, paroxysmal or persistent weakness of the contralateral limb, and aphasia. Occlusion in the posterior circulation was noted in six cases, including basilar artery occlusion in two cases and occlusion in the V4 segment of the vertebral artery in four cases. The initial symptoms of these patients included dizziness, giddiness, ataxia, blurred vision, nausea, vomiting, and dysarthria. MRI showed small subacute infarction in six cases, old infarction in 19 cases, and no obvious infarction in two cases.

Procedure, Dyna micro-CT, and post-processing of images

Preoperative preparation, mechanical recanalization of the occluded blood vessel, and stent implantation were as those reported previously.[3],[4],[5],[6] Residual stenoses were measured and recorded after stenting based on angiography findings. Anterograde blood flow after reperfusion was evaluated according to the thrombolysis in cerebral ischemia (TICI) grading system, and a score ≥2b indicated successful recanalization.[9] Dyna CT and Dyna micro-CT were used to scan the stent implantation area during and after the operation. The data for the latter were collected using the following parameters: 20S high-resolution flat CT scan (x-ray tube voltage: 109 kV; current: 460 ma); field of view, 22 cm; maximum rotation, 200°; frames, 496; and rotation acquisition, 20 s. After obtaining the image, the image was reconstructed using Siemens workstation (InStudio 3D). Images reconstructed using Dyna CT can show the overall intracranial situation, for example, whether there was high-density contrast media overflow, which helped determine if there was intraparenchymal hemorrhage or subarachnoid hemorrhage or not. Through the local reconstruction using Dyna micro-CT, the details of the stent wires and marks and the degree of stent expansion can be observed.

Evaluation of image quality

Images obtained using Dyna CT and Dyna micro-CT combined with SMART image quality evaluation were evaluated by two experienced neurointerventional doctors. The evaluation criteria were as follows: (1) Platinum-iridium marks (Neuroform EZ stent) or Tantalum marks (Enterprise stent), 0: not seen; 1: unclear; and 2: clear. (2) Nickel-titanium wire, 0: not seen, 1: unclear; and 2: clear.

Postoperative management and follow-up

After successful operation, patients' vital signs were measured strictly and the systolic blood pressure was controlled in the range of 90-110 mmHg for more than 48 hours. If there were postoperative National Institute of Health Stroke Scale (NIHSS) or modified Rankin Scale (mRS) score changes, head CT and/or MRI were performed to evaluate bleeding or ischemic events. According to the results of thromboelastography or antiplatelet drug gene detection, the patients were prescribed oral clopidogrel for 3- 6 months, followed by long-term aspirin enteric-coated tablets and statins. Postoperative imaging follow-up was performed with DSA, Dyna micro-CT, or CTA to determine whether there was restenosis or occlusion in the stent. The improvement of cerebral perfusion was evaluated by MRI or CT perfusion imaging. A modified Rankin scale (mRS) score of 0–2 was considered to indicate a good prognosis while that of 3–6 was considered to indicate a poor prognosis.

Statistical analyses

Statistical analyses were performed using SPSS 22.0 software. The (x̄ ± s) is used to describe the measurement data, which accorded with normal distribution and the Chi-square test or Fisher precision test was used to evaluate image quality. P <0.05 was considered statistically significant.


 » Results Top



 » Technical and anatomic postoperative results Top


Of the 27 patients, 22 were successfully recanalized and 22 intracranial stents (including 14 Neuroform Ez and eight Enterprise stents) were implanted. Dyna micro-CT was performed for the stent area during the operation. The reconstructed images showed incomplete expansion of seven stents. After balloon dilatation, the stents fully expanded, which was confirmed using Dyna micro-CT [Figure 1]. Immediate postoperative angiography showed a residual stenosis rate of 0%–22% in 22 patients. In these patients, anterograde blood flow returned to TICI 3 in 17 patients and TICI 2B in five patients.
Figure 1: Mechanical recanalization and stenting for basal artery chronic occlusion. A 63-year-old man was admitted with a 2-month history of dizziness and instability while standing. (a) High-resolution MRI atherosclerotic occlusion of the basal artery (white arrow). (b) Three-dimensional digital subtraction angiography (3D-DSA) showing a rat tail-shaped occlusion at the beginning of the basal artery (white arrow). (c) Gateway balloon (2 mm × 9 mm) dilation was performed followed by insertion of a Neuroform EZ stent measuring 2.5 mm × 15 mm (white arrow) at the occlusion. The measured vascular remnant stenosis was 50%. (d) High-resolution Dyna CT showing the partially expanded stent. (e-f) Introduction of Gateway balloon (2.5 mm × 9 mm) to dilate the residual stenosis of the stent, and review of the 3D-DSA findings showed that the stenosis significantly improved. The residual stenosis was 15%. Anterograde blood flow was restored to Thrombolysis in Cerebral Infarction grade III. (g) Local expansion of the stent significantly improved, as confirmed by Dyna micro-CT. (h) CT angiography performed at the 6-month follow-up shows smooth blood flow in the basal artery stent (white arrow)

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Dyna micro-CT combined with SMART image quality evaluation

Compared to reconstruction with normal Dyna CT, image reconstruction using Dyna micro-CT provided significantly improved image quality (P < 0.05). Dyna micro-CT could clearly show the metal wire of the stent, help to evaluate the extent of stent expansion and the situation of wall apposition [Table 1]; [Figure 2].
Table 1: Evaluation of image quality with Dyna CT and Dyna micro-CT (n=22)

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Figure 2: The right middle cerebral artery (MCA) chronic occlusion was mechanically recanalized and stented. (a) A 52-year-old male presented with paroxysmal left limb weakness for half a year with one-week aggravation. CT angiography of the right MCA showed a rat tail-shaped occlusion (white arrow). (b) DSA showed that the right MCA was occluded at the beginning and disordered collateral circulation was found at the occluded site. (c) CT perfusion imaging showed that the right hemisphere was significantly less perfused than the contralateral hemisphere. (d) Neuroform EZ 2.5 mm × 15 mm stent (black arrow) was placed at the occlusion. The stent was found to be well dilated, the remaining stenosis was 15%, and anterograde blood flow was restored to Thrombolysis in Cerebral Infarction grade III. (e) Immediately after the operation, the stent's mark and metal wire were not clear on the Dyna CT scan and reconstruction, and complete expansion of the stent could not be confirmed. (f) After the operation, high-resolution Dyna micro-CT clearly showed the mark and nickel-titanium wire of the stent; the stents had expanded satisfactorily, and the image quality was improved obviously. (g) Six months of review DSA showed smooth blood flow in middle cerebral artery stent. (h) Re-examination of CT perfusion imaging findings showed a significant improvement in right hemisphere perfusion in comparison with preoperative findings

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Complications

Of the 22 patients, three showed mild-to-moderate dysphoria after the operation. After sedation and control of blood pressure for 1–3 days, the patients' condition recovered to that before the operation. In one patient, Dyna micro-CT showed a subacute small infarct in the left basal ganglia area with continuous retention and stratification of the contrast agent and bleeding could not be excluded. The patient was treated with neutralizing heparin and double antiplatelet medication was stopped. The patient's condition was closely monitored; 22 hours after the operation, the patient experienced headache. CT showed intraparenchymal hemorrhage in the stent area. Thus, the patient was treated with evacuation of the hematoma plus bone flap decompression. After 3 weeks, the right upper limb muscle strength was grade III, the right lower limb muscle strength was grade IV, and mRS score was 3 [Figure 3]. The remaining 18 patients were stable without acute thrombosis or bleeding complications. Among the six patients who were not recanalized, one patient's language function worsened compared to that before the operation. After conservative treatment for 2 weeks, the patient's language function recovered to the preoperation level; thereafter, roofing of the temporal muscle and bypass surgery were performed.
Figure 3: The left middle cerebral artery (MCA) chronic occlusion was mechanically recanalized and stented. (a) A 61-year-old woman was admitted with dizziness and right limb numbness for 4 months. The CT scan showed an old infarction in the left basal ganglia (black arrow). (b-d) Magnetic resonance angiography, digital subtraction angiography (DSA), and 3D images showed a rat tail-shaped occlusion at the beginning of the left middle cerebral artery (black arrow); (e-f) Enterprise 4.5 mm × 22 mm stents (white arrow) were implanted at the occlusion. The stent were dilated well and the residual stenosis was 18%, and the anterograde blood flow was restored to Thrombolysis in Cerebral Infarction grade 3. (g) After the operation, high-resolution Dyna micro-CT clearly showed the mark and nickel-titanium wire of the stent, and the stent had expanded satisfactorily. (h-i) Dyna micro-CT performed immediately after the operation showed that the contrast agent in the left basal ganglia infarction was retained and stratified, and the possibility of bleeding was considered. (j) After the 22-hour operation, CT shows an intraparenchymal hemorrhage in the left hemisphere stent area

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Follow-up

All 22 patients were followed up for 6-26 months (average, 12.0 ± 5.9 months) after stent implantation. The improvement rate of symptoms was 95.5% (21/22), and the complete remission rate was 77.3% (17/22). The mRS scores were as follows: 0 in four cases, 1 in seven cases, 2 in ten cases, and 3 in one case. None of the patients died or showed a recurrent stroke or transient ischemic attack after the operation. All 21 patients underwent imaging follow-up for 6 months (CTA, four cases; DSA, 17 cases), and three patients showed mild-to-moderate stenosis and no reocclusion. CT or MRI perfusion imaging was performed in 15 patients. The results showed a significant improvement in the hypoperfusion area in comparison with that before the operation.


 » Discussion Top


Recanalization and stenting for chronic cerebral artery occlusion are more difficult and riskier than those for symptomatic intracranial artery stenosis, posing a major challenge to interventional neurologists. The limited available literature suggests that in patients with subacute or chronic cerebral arterial occlusion, the recanalization rate is 85.7%–100%, perioperative complication rate is 8.3%–44.4%, and mortality rate is 44.4%.[10],[11],[12] In order to minimize risks and improve outcomes, in addition to rigorous screening of cases, perioperative care, and fine surgical operations, it is important to use advanced imaging techniques for preoperative evaluation.[2],[13]

The development of C-arm CT has solved many problems associated with the presence of invisible structures in previous neurointerventional therapy and has cross-era significance. However, for patients undergoing stent implantation, fluoroscopy and conventional angiography cannot easily reveal stent incomplete expansion, and the application of conventional C-arm CT is limited by the stents' high-density wire artefacts.[14],[15] This is an important risk factor for thrombotic events and long-term stent restenosis. Dyna micro-CT is a new-generation high-resolution C-arm CT system developed by Siemens. It was introduced in Germany in 2016. In comparison with traditional Dyna CT, it uses a smaller scanning area (stent area), a non-binned mode technique instead of the original 2 × 2 pixel binning technique, and optimized exposure conditions and image-processing methods, thereby improving the spatial resolution of local lesions without using low-concentration contrast agents. In comparison with the former technique, Dyna micro-CT shows an obvious improvement in stent visibility, which has been proven in animal experiments.[8] In early clinical studies, we found that with appropriate post-processing of the image and angle selection, Dyna micro-CT can show the tangent position and cross-section of the stent more clearly than traditional Dyna CT. It is helpful to observe the expansion of the stent and the situation of apposition to undertake the corresponding treatment measures. However, only a few previous reports have discussed the clinical effectiveness of Dyna micro-CT in intracranial stent implantation.[7],[8],[16]

In this study, Dyna micro-CT detected seven cases of incomplete stent expansion, which was not easy to detect with routine CT and conventional C-arm CT, either because of the metal artefact of the stent or the hard plaque in the occluded part. These seven cases were treated with balloon dilatation and the apposition was improved. Caroff et al.[17] used high-resolution flat CT (Vaso CT) to observe the stent-assisted embolization of cerebral aneurysms and concluded that high-resolution flat CT could reduce the incidence of thromboembolic events. In the present study, this was also confirmed by the absence of severe intraoperative and postoperative complications such as acute thrombosis. In cases of hemorrhage, CT and MRI showed that the primary infarction was located in the left basal ganglia region and the focus was small (<1 cm) and not acute, so it was not clear on C-arm CT after stenting and could be easily ignored or thought to be the overflow of contrast agent from the infarct lesion. Dyna micro-CT can clearly show the stratified state of the contrast agent in the lesion (shown by the arrow, [Figure 3]h, [Figure 3]i), indicating that the possibility of bleeding is high. As the patients' speech and limb movements were normal, they were treated with neutralizing heparin and double antiplatelet therapy was stopped. The hematoma was subsequently enlarged and removal of hematoma plus bone flap decompression was conducted, and the patient recovered well. This suggests that on the one hand, we should strictly control the indications in the selection of cerebral artery occlusive cases, and be cautious in patients with acute-stage large-area cerebral infarctions. After the occlusive artery is recanalized, blood pressure should be strictly controlled to prevent reperfusion hemorrhage. On the other hand, in patients with infarction due to artery occlusion, the integrity of the blood-brain barrier is destroyed, and some patients may show overflow of the contrast agent due to increased vascular permeability in the infarcted area. This situation should be promptly reviewed using CT to assess the status of contrast agent dispersion and rule out the possibility of bleeding.

In conclusion, Dyna micro-CT shows good applicability in operations involving chronic cerebral artery occlusion and stent placement, which helps reduce the incidence of postoperative complications and improve the long-term patency rate of the stent. However, this study is a single-center retrospective study and has limitations, and its reliability and long-term efficacy need to be further confirmed by a long-term, large-sample, multi-center, double-blind control study.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

This work was supported by the National Natural Science Foundation of China (Grant No. 81801806) and the Technological Research Project of Henan Provincial Science and Technology Department (172102310397).

Conflicts of interest

There are no conflicts of interest.



 
 » References Top

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Wang D, Wang Y. Opening already occluded middle cerebral artery, internal carotid artery or other cerebral arteries: When, where, how and why? Stroke Vasc Neurol 2017;2:106-7.  Back to cited text no. 2
    
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Ma L, Liu YH, Feng H. Endovascular recanalization for symptomatic subacute and chronic intracranial large artery occlusion of the anterior circulation: Initial experience and technical considerations. Neuroradiology 2019;61:833-42.  Back to cited text no. 3
    
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Guo D, Ma J, Li TF. Stent-assisted mechanical recanalization for symptomatic subacute or chronic middle cerebral artery occlusion. Int J Clin Exp Med 2015;8:21818-21.  Back to cited text no. 4
    
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Yu Jia Z, Sun Song Y, Jon Sheen J. Endovascular recanalization of symptomatic non-acute intracranial artery occlusion: Procedural and mid-term clinical outcomes in the anterior circulation. Interv Neuroradiol 2019;25:380-9.  Back to cited text no. 5
    
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Kim JE, Kim AR, Paek YM. Safety and efficacy of mechanical thrombectomy with the Solitaire device in large artery occlusion. Neurol India 2012;60:400-5.  Back to cited text no. 6
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Li TF, Ma J, Han XW. Application of high-resolution C-arm CT combined with streak metal artifact removal technology for the stent-assisted embolization of intracranial aneurysms. AJNR Am J Neuroradiol 2019;40:1752-8.  Back to cited text no. 7
    
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Aghaebrahim A, Jovin T, Jadhav AP. Endovascular recanalization of complete subacute to chronic atherosclerotic occlusions of intracranial arteries. J Neurointerv Surg 2014;6:645-8.  Back to cited text no. 10
    
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Struffert T, Lang S, Adamek E. Angiographic C-arm CT visualization of the Woven EndoBridge cerebral aneurysm embolization device (WEB): First experience in an animal aneurysm model. Clin Neuroradiol 2014;24:43-9.  Back to cited text no. 14
    
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Caroff J, Mihalea C, Neki H. Role of C-arm VasoCT in the use of endovascular WEB flow disruption in intracranial aneurysm treatment. Am J Neuroradiol 2014;35:1353-7.  Back to cited text no. 17
    


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