Usefulness of 3D T1-SPACE in Combination With 3D-TOF MRA for Follow-Up Evaluation of Intracranial Aneurysms Treated With Pipeline Embolization Devices

High-resolution vessel wall imaging for quantitatively and qualitatively evaluating in-stent stenosis of intracranial aneurysms

Background

It is critical to accurately and noninvasively evaluate the stented parent artery of intracranial aneurysms (IAs) with endovascular treatment.

Objective

To investigate high-resolution vessel wall imaging (HR-VWI) for quantitative and qualitative evaluation of in-stent stenosis (ISS) in IAs treated with stent placement (SP).

Methods

Fifty-five patients (58 aneurysms) underwent HR-VWI, contrast-enhanced (CE)-HR-VWI, CE-MR angiography (MRA), time-of-flight (TOF)-MRA, and digital subtraction angiography (DSA) six months after SP, and the reliability of quantitative stent lumen measurements was evaluated by intraclass correlation coefficient (ICC) analysis. Agreement and correlation of quantitative evaluation were estimated by comparing the four MR imaging modalities with DSA. The diagnostic performance for >0%, ≥25%, and ≥50% of ISS degrees and overall diagnostic accuracy for the ISS degrees of the four MR imaging modalities were calculated to qualitative evaluation.

Results

The reliability of CE-HR-VWI and HR-VWI for ISS quantitative measurements was excellent (ICC 0.955-0.989). The agreement and correlation of CE-HR-VWI, HR-VWI versus DSA for ISS quantitative measurements were better than those of CE-MRA and TOF-MRA (p < 0.05). The diagnostic performance for distinguishing the degree of ISS >0%, ≥25%, and ≥50% by CE-HR-VWI and HR-VWI was superior to CE-MRA and TOF-MRA, and their overall diagnostic accuracy was 96.55 and 94.83%, respectively. HR-VWI and CE-HR-VWI were not statistically significant in the quantitative and qualitative evaluation of ISS performance (p > 0.05).

Conclusion

HR-VWI and CE-HR-VWI have similar performance and value in the quantitative and qualitative evaluation of ISS, and HR-VWI without contrast media could be used as an ideal long-term follow-up approach after SP treatment for IAs.

Enhanced vessel wall magnetic resonance imaging in the follow-up of intracranial aneurysms treated with flow diversion

OBJECTIVE

This study aimed to compare the efficacy of enhanced 3D T1-weighted black-blood fast-spin-echo vessel wall magnetic resonance imaging (eVW-MRI) and time-of-flight magnetic resonance angiography (TOF MRA) for follow-up evaluation of aneurysms treated with flow diversion (FD).

METHODS

Our study enrolled 77 patients harboring 84 aneurysms treated with FD. Follow-up was by MRI (eVW-MRI and TOF MRA) and digital subtraction angiography (DSA). Two radiologists, blinded to DSA examination results, independently evaluated the images of aneurysm occlusion and parent artery patency using the Kamran-Byrne Scale. Interobserver diagnostic agreement and intermodality diagnostic agreement were acquired. Pretreatment and follow-up aneurysm wall enhancement (AWE) patterns were collected.

RESULTS

Based on the Kamran-Byrne Scale, the intermodality agreement between eVW-MRI and DSA was better than TOF MRA versus DSA for aneurysm remnant detection (weighted ĸ = 0.891 v. 0.553) and parent artery patency (ĸ = 0.950 v. 0.221). Even with the coil artifact, the consistency of eVW-MRI with DSA for aneurysm remnant detection was better than that of TOF MRA (weighted ĸ = 0.891 v. 0.511). The artifact of adjunctive coils might be more likely to affect the accuracy in evaluating parent artery patency with TOF MRA than with eVW-MRI (ĸ = 0.077 v. 0.788). The follow-up AWE patterns were not significantly associated with pretreatment AWE patterns and aneurysm occlusion.

CONCLUSIONS

The eVW-MRI outperforms TOF MRA as a reliable noninvasive and nonionizing radioactive imaging method for evaluating aneurysm remnants and parent artery patency after FD. The significance of enhancement patterns on eVW-MRI sequences needs more exploration.

CLINICAL RELEVANCE STATEMENT

The application of enhanced vessel wall magnetic resonance imaging has proven to be a promising tool to depict aneurysm remnant and parent artery stenosis in order to tailor the antiplatelet therapy strategy in patients after flow diversion.

KEY POINTS

• Enhanced vessel wall magnetic resonance imaging has an emerging role in depicting aneurysm remnant and parent artery patency after flow diversion. • With or without the artifact from adjunctive coils, enhanced vessel wall magnetic resonance imaging was better than TOF MRA in detecting aneurysm residual and parent artery stenosis by using DSA imaging as the standard. • Enhanced vessel wall magnetic resonance imaging holds potential to be used as an alternative to DSA for routine aneurysm follow-up after flow diversion.

Recurrent reversible in-stent-stenosis after flow diverter treatment

Flow diverter stents (FDS) are well established in the treatment of intracranial aneurysms which are difficult to treat with conventional endovascular techniques. However, they carry a relatively high risk of specific complications compared to conventional stents. A minor but frequent finding is the occurrence of reversible in-stent-stenosis (ISS) that tend to resolve spontaneously over time. Here, we report the case of a patient in their 30s who was treated with FDS for bilateral paraophthalmic internal carotid artery (ICA) aneurysms. ISS were found at the respective early follow-up examinations on both sides and had resolved at the 1-year follow-up examinations. Surprisingly ISS reoccurred at both sides in later follow-up examinations and again resolved spontaneously. The recurrence of ISS after resolution is a finding that has not been described previously. Its incidence and further development should be investigated systematically. This might contribute to our understanding of the mechanisms underlying the effect of FDS.

Diagnostic Performance of High-Resolution Vessel Wall MR Imaging Combined with TOF-MRA in the Follow-up of Intracranial Vertebrobasilar Dissecting Aneurysms after Reconstructive Endovascular Treatment

BACKGROUND AND PURPOSE

Few studies have reported the utility of high-resolution vessel wall MR imaging in the follow-up of endovascularly treated vertebrobasilar dissecting aneurysms. This study aimed to evaluate the diagnostic performance of high-resolution vessel wall MR imaging combined with TOF-MRA in the follow-up of intracranial vertebrobasilar dissecting aneurysms after reconstructive endovascular treatment.

MATERIALS AND METHODS

Patients with intracranial vertebrobasilar dissecting aneurysms with reconstructive endovascular treatment and followed up with TOF-MRA, high-resolution vessel wall MR imaging, and DSA were included. With DSA as the criterion standard, the diagnostic performance of TOF-MRA, high-resolution vessel wall MR imaging, and high-resolution vessel wall MR imaging combined with TOF-MRA in the evaluation of aneurysm occlusion status and parent artery patency was assessed. Visualization of the stented artery on TOF-MRA and high-resolution vessel wall MR imaging was rated on a 5-point scale.

RESULTS

Twenty-seven patients with 29 aneurysms were included. The sensitivity, specificity, positive predictive value, and negative predictive value of TOF-MRA, high-resolution vessel wall MR imaging, and high-resolution vessel wall MR imaging combined with TOF-MRA for diagnosing aneurysm remnants were 80.0%, 100.0%, 100.0%, and 82.4%; 53.3%, 100.0%, 100.0%, and 66.7%; and 93.3%, 100.0%, 100.0%, and 93.3%, respectively. For the visualization of the stented artery, the mean score of high-resolution vessel wall MR imaging was significantly higher than that of TOF-MRA (4.88 [SD, 0.32] versus 2.53 [SD, 1.25], P < .001). In the evaluation of parent artery patency (normal or pathologic), whereas TOF-MRA had a sensitivity, specificity, positive predictive value, and negative predictive value of 100.0%, 8.0%, 14.8%, and 100.0%, respectively, high-resolution vessel wall MR imaging was completely consistent with the DSA.

CONCLUSIONS

High-resolution vessel wall MR imaging combined with TOF-MRA at 3T showed good diagnostic performance in the follow-up of intracranial vertebrobasilar dissecting aneurysms after reconstructive endovascular treatment.

Intimal hyperplasia detection after aneurysm treatment by flow diversion using magnetic resonance vessel wall imaging

In-stent caliber reduction due to neo-intimal hyperplasia (NIH) is an underestimated event that may follow flow diverter stent (FDS) implantation. Although mostly asymptomatic, this vascular reaction is a well-known risk factor for delayed ischemic strokes. Here we report on the contribution of magnetic resonance vessel wall imaging (MR-VWI), performed on a 1.5 T scanner, to detect in-stent stenosis and mural inflammation in a 40-year-old woman with cerebral aneurysm previously treated with FDS and presenting with motor disturbances on follow-up. Digital subtraction angiography and cone-beam CT confirmed 1.5 T MRVWI findings, highlighting the potential value of this non-invasive imaging technique in investigating and detecting NIH.

Follow-up of Intracranial Aneurysms Treated by Flow Diverters: Evaluation of Parent Artery Patency Using 3D-T1 Gradient Recalled-Echo Imaging with 2-Point Dixon in Combination with 3D-TOF-MRA with Compressed Sensing

BACKGROUND AND PURPOSE

MRA assessment of parent artery patency after flow-diverter placement is complicated by imaging artifacts produced by these devices. The purpose of this study was to assess the accuracy of liver acquisition with volume acceleration-flex technique (LAVA-Flex) MRA in combination with 3D-TOF with HyperSense MRA for the evaluation of parent vessel status after intracranial flow-diverter placement.

MATERIALS AND METHODS

Fifty-six patients treated by flow diversion and followed with both DSA and 3T MRA between November 2020 and August 2021 were included. All patients were evaluated for parent artery patency using the same imaging protocol (DSA, noncontrast MRA including 3D-TOF with HyperSense and LAVA-Flex, and contrast-enhanced MRA, including time-resolved imaging of contrast kinetics MRA and delayed contrast-enhanced MRA).

RESULTS

With DSA as a criterion standard to evaluate the patency of the parent vessel, noncontrast MRA had a good specificity (0.83) and positive predictive value (0.65), better than contrast-enhanced MRA (0.55 and 0.41, respectively). Both had excellent sensitivity and negative predictive value: noncontrast MRA, 0.93 and 0.97, respectively; contrast-enhanced MRA, 0.93 and 0.96, respectively. Specificity and positive predictive value tended to be lower for patients treated with additional devices than for those treated with flow diverters exclusively and for patients treated with a specific type of flow diverter.

CONCLUSIONS

Noncontrast MRA can be used for noninvasive follow-up of intracranial aneurysms treated by flow diverters. The combined use of LAVA-Flex and 3D-TOF with HyperSense sequences allows monitoring the status of the parent artery and aneurysm occlusion.