Follow-up of coiled cerebral aneurysms at 3T: comparison of 3D time-of-flight MR angiography and contrast-enhanced MR angiography

BACKGROUND AND PURPOSE: Our aim was to compare contrast-enhanced MR angiography (CE-MRA) and 3D time-of-flight (TOF) MRA at 3T for follow-up of coiled cerebral aneurysms.MATERIALS AND METHODS: Fifty-two patients treated with Guglielmi detachable coils for 54 cerebral aneurysms were evaluated at 3T MRA. 3D TOF MRA (TR/TE = 23/3.5; SENSE factor = 2.5) and CE-MRA by using a 3D ultrafast gradient-echo sequence (TR/TE = 5.9/1.8; SENSE factor = 3) enhanced with 0.1-mmol/kg gadobenate dimeglumine were performed in the same session. Source images, 3D maximum intensity projection, 3D shaded surface display, and/or 3D volume-rendered reconstructions were evaluated in terms of aneurysm occlusion/patency and artifact presence.RESULTS: In terms of clinical classification, the 2 MRA sequences were equivalent for 53 of the 54 treated aneurysms: 21 were considered fully occluded, whereas 16 were considered to have a residual neck and 16 were considered residually patent at follow-up MRA. The remaining aneurysm appeared fully occluded at TOF MRA but had a residual patent neck at CE-MRA. Visualization of residual aneurysm patency was significantly (P = .001) better with CE-MRA compared with TOF MRA for 10 (31.3%) of the 32 treated aneurysms considered residually patent with both sequences. Coil artifacts were present in 5 cases at TOF MRA but in none at CE-MRA. No relationship was apparent between the visualization of patency and either the size of the aneurysm or the interval between embolization and follow-up.CONCLUSION: At follow-up MRA at 3T, unenhanced TOF and CE-MRA sequences are similarly effective at classifying coiled aneurysms as occluded or residually patent. However, CE-MRA is superior to TOF MRA for visualization of residual patency and is associated with fewer artifacts.

Regular imaging follow-up of patients with intracranial aneurysms treated with Guglielmi detachable coils (GDCs) is necessary because of the risk of aneurysm reconfiguration (ie, coil compaction and/or growth of a residual aneurysm neck or body remnant) with time.^1–4 Of the techniques available for monitoring the results of embolization therapy, MR angiography (MRA) has emerged as the technique of choice at most institutions. Advantages over conventional digital subtraction angiography (DSA) include minimal invasiveness with no associated risk of neurologic complications, reduced patient discomfort and inconvenience, greater cost savings, and no exposure to ionizing radiation or potentially nephrotoxic iodinated contrast media. An alternative minimally invasive procedure is CT angiography (CTA). However, whereas this technique has proved useful for aneurysm detection,^5–9 limitations to its use for follow-up of coiled aneurysms include streak and other coil-related artifacts.^10–12 Moreover, CTA also requires exposure to ionizing radiation and iodinated contrast media, which may be undesirable if repeat follow-up examinations are required.Studies performed to date have shown that nonenhanced 3D time-of-flight (TOF) MRA sequences on 1.5T scanners are frequently satisfactory for the follow-up of coiled aneurysms^1–20 but that 3D TOF MRA on 3T scanners offers improved depiction of both treated²¹ and untreated²² aneurysms due to the greater spatial and contrast resolution achievable at a higher magnetic field strength. Concerning the use of gadolinium contrast material, some studies have suggested that contrast-enhanced MRA (CE-MRA) provides no additional benefit compared with nonenhanced 3D TOF MRA at either 1.5T^15,20 or 3T,²¹ whereas other studies have shown that CE-MRA permits better visualization of coiled aneurysms and of branch arteries and residual neck, particularly in large or giant aneurysms.^14,22–26 Recently, Nael et al²⁷ demonstrated that CE-MRA with highly accelerated (×4) parallel acquisition at 3T provides comparable information to accelerated (×2) 3D TOF MRA at 3T for the characterization of untreated intracranial aneurysms without the known drawbacks of TOF MRA techniques (ie, prolonged acquisition time, spin saturation, and flow-related artifacts). On the other hand, Gibbs et al²⁸ showed that with elliptic-centric imaging, 3D TOF MRA at 3T is superior to CE-MRA at 3T in terms of both image quality and detection of untreated intracranial aneurysms. Our study was performed to evaluate CE-MRA with accelerated (×3) parallel acquisition at 3T compared with accelerated (×2.5) 3D TOF MRA at 3T for the follow-up of GDC-treated intracranial aneurysms. To the authors’ knowledge, this is the first study to compare MRA sequences at 3T for follow-up of coiled aneurysms.     

Comparison of remnant size in embolized intracranial aneurysms measured at follow-up with DSA and MRA

Introduction

The possibility of recanalization and the need for retreatment are the most important limitations of intracranial aneurysm embolization. The purpose of the study was to compare the size of aneurysm remnants measured at follow-up with three-dimensional digital subtracted angiography (3D-DSA) and magnetic resonance angiography (MRA).

Methods

Twenty-six aneurysms were found incompletely occluded in 72 consecutively examined patients at a follow-up after 3?months. The diameters and volume of aneurysm remnants were compared between 3D-DSA, time-of-flight MRA (TOF-MRA), contrast-enhanced TOF-MRA (CE-TOF-MRA), and contrast-enhanced MRA (CE-MRA) at 1.5?T.

Results

There was a significant correlation between remnant volumes calculated based on 3D-DSA and all MRA modalities. The intraobserver variability of the measurements ranged from 3.4 to 4.1?% and the interobserver variability from 5.8 to 7.3?%. There were no significant differences in the variability between the techniques. The mean residual filling volume ranged from 16.3?±?19.0?mm³ in TOF-MRA to 30.5?±?44.6?mm³ in 3D-DSA (P?<?0.04). Significant differences were found in the volumes measured with 3D-DSA and CE-MRA as compared to TOF-MRA and CE-TOF-MRA (P?<?0.01). There was a moderate significant correlation between the residual filling and the relative error of measurement in the case of TOF-MRA and CE-TOF-MRA.

Conclusions

TOF-MRA seems to underestimate the size of aneurysm remnants detected at follow-up and should not be used as a sole imaging method to decide on re-embolization.     

Factors predicting retreatment and residual aneurysms at 1?year after endovascular coiling for ruptured cerebral aneurysms: Prospective Registry of Subarachnoid Aneurysms Treatment (PRESAT) in Japan

Introduction

Endovascular treatment of cerebral aneurysms includes follow-up imaging to identify aneurysms that may need retreatment. The aim of this study was to determine predictors of incomplete aneurysm occlusion at 1?year after endovascular coiling for ruptured cerebral aneurysms.

Methods

In 129 patients of the Prospective Registry of Subarachnoid Aneurysms Treatment cohort, ruptured aneurysms were coiled within 14?days of onset and both initial post-coiling and 1-year follow-up digital subtraction angiography or magnetic resonance angiography were obtained. Factors predicting 1-year incomplete aneurysm occlusion (retreatment within 1-year or residual aneurysms at 1?year) were determined using multivariate logistic regression analyses.

Results

One-year incomplete aneurysm occlusion was identified in 59 patients, including ten patients who were retreated within 1-year post-coiling. Dome size ≥7.5?mm (P?=?0.007, odds ratio (OR)?=?5.00, 95% confidence interval (CI)?=?1.55–16.15), pre-treatment aneurysm re-rupture (P?=?0.023, OR?=?3.50, 95% CI?=?1.19–10.31), non-small size/small neck aneurysm (dome size, ≥10?mm or neck size, ≥4?mm; P?=?0.022, OR?=?3.26, 95% CI?=?1.19–8.96), and residual aneurysms on immediate post-coiling angiograms (P?=?0.017, OR?=?1.43, 95% CI?=?1.07–1.93) significantly predicted incomplete aneurysm occlusion at 1-year post-coiling.

Conclusions

In addition to the characteristics of aneurysm and initially incomplete aneurysm occlusion, this study showed pre-treatment aneurysm re-rupture to be a predictor that favors closer imaging follow-ups for coiled aneurysms.     

Contrast-Enhanced Time-Resolved MRA for Follow-Up of Intracranial Aneurysms Treated with the Pipeline Embolization Device

BACKGROUND AND PURPOSE:Endovascular reconstruction and flow diversion by using the Pipeline Embolization Device is an effective treatment for complex cerebral aneurysms. Accurate noninvasive alternatives to DSA for follow-up after Pipeline Embolization Device treatment are desirable. This study evaluated the accuracy of contrast-enhanced time-resolved MRA for this purpose, hypothesizing that contrast-enhanced time-resolved MRA will be comparable with DSA and superior to 3D-TOF MRA.MATERIALS AND METHODS:During a 24-month period, 37 Pipeline Embolization Device–treated intracranial aneurysms in 26 patients underwent initial follow-up by using 3D-TOF MRA, contrast-enhanced time-resolved MRA, and DSA. MRA was performed on a 1.5T unit by using 3D-TOF and time-resolved imaging of contrast kinetics. All patients underwent DSA a median of 0 days (range, 0–68) after MRA. Studies were evaluated for aneurysm occlusion, quality of visualization of the reconstructed artery, and measurable luminal diameter of the Pipeline Embolization Device, with DSA used as the reference standard.RESULTS:The sensitivity, specificity, and positive and negative predictive values of contrast-enhanced time-resolved MRA relative to DSA for posttreatment aneurysm occlusion were 96%, 85%, 92%, and 92%. Contrast-enhanced time-resolved MRA demonstrated superior quality of visualization (P = .0001) and a higher measurable luminal diameter (P = .0001) of the reconstructed artery compared with 3D-TOF MRA but no significant difference compared with DSA. Contrast-enhanced time-resolved MRA underestimated the luminal diameter of the reconstructed artery by 0.965 ± 0.497 mm (27% ± 13%) relative to DSA.CONCLUSIONS:Contrast-enhanced time-resolved MRA is a reliable noninvasive method for monitoring intracranial aneurysms following flow diversion and vessel reconstruction by using the Pipeline Embolization Device.

Surgical clipping or endovascular coil embolization is generally the preferred treatment for intracranial aneurysms.¹ The Pipeline Embolization Device (PED; Covidien, Irvine, California) is an endovascular device that has redefined the scope of treatment for large, giant, wide-neck, or fusiform aneurysms or aneurysms having failed coil embolization, by reconstructing the parent artery and restoring its natural course.² The PED is designed for 85% reduction of blood flow within an aneurysm, which induces thrombosis² while keeping perforators and/or side branch vessels patent.³ Results from a multicenter prospective trial for treatment of uncoilable or failed large and giant ICA aneurysms with the PED demonstrated 99% technical success and 74% complete occlusion with 6% major ipsilateral stroke or death.⁴ Flow diversion with the PED has also been reported in the treatment of HIV vasculopathy, with fusiform cerebral aneurysms precluding parent vessel sacrifice or surgical bypass.⁵Digital subtraction angiography is the reference standard for the evaluation of aneurysms after endovascular treatment due to its unsurpassed spatial resolution; however, DSA is invasive and not without risks of puncture site and neurologic complications.⁶ Posttreatment follow-up of intracranial aneurysms after coil embolization with MRA by using 3D-TOF or contrast-enhanced techniques is a potential noninvasive alternative to DSA for the evaluation of PED-treated aneurysms without the use of ionizing radiation.⁷ Contrast-enhanced time-resolved MRA (CE-TR MRA) uses acquisition schemes aimed at accelerated data collection, primarily using parallel imaging algorithms and novel k-space trajectories to achieve high temporal resolution for multiphasic MRA examinations. This technique provides consistent, technologist-independent, optimal arterial enhancement for contrast-enhanced MRA and provides information on temporal contrast kinetics.^8,9 Use of CE-TR MRA has been reported in the evaluation of intracranial lesions such as arteriovenous malformations and dural arteriovenous fistulas and for assessment of stenosis of the extracranial carotid artery, and it seems to be a promising technique for evaluating aneurysms after stent-assisted coil embolization.^9–11We hypothesized that TR-CE MRA could provide information comparable with DSA and would be superior to 3D-TOF MRA in the evaluation of intracranial aneurysms and the parent artery following flow diversion and parent vessel reconstruction with the PED.     

The clinical value of MRA at 3.0?T for the diagnosis and therapeutic planning of patients with subarachnoid haemorrhage

Objective

To evaluate the clinical value of unenhanced magnetic resonance angiography (MRA) at 3.0?T for the diagnosis and therapeutic planning of patients with subarachnoid haemorrhage (SAH).

Methods

A total of 165 patients with SAH were referred for three-dimensional time-of-flight MRA (3D-TOF-MRA) before digital subtraction angiography (DSA). For each aneurysm, 3D-TOF-MRA was used to determine whether the aneurysm was suitable for coil placement with or without balloon/stent-assisted coiling, surgical clipping or conservative treatment. Treatment planning with 3D-TOF-MRA was compared with actual treatment decisions or treatment that had been carried out in each aneurysm decided using DSA.

Results

The aneurysm-based evaluation yielded accuracy of 96.9%, sensitivity of 97.6%, specificity of 93.1%, positive predictive value (PPV) of 98.8% and negative predictive value (NPV) of 87.1%, in the detection of intracranial aneurysms. Treatment planning could be correctly made on the basis of aneurysm anatomy and working view by volume rendering (VR) 3D-TOF-MRA with accuracy, sensitivity, specificity, PPV and NPV of 94.9%, 94.0%, 100%, 100% and 74.4%, respectively, on a per aneurysm-based evaluation.

Conclusions

VR 3D-TOF-MRA offers high diagnostic accuracy in the detection of ruptured intracranial aneurysms, and appears to be an effective treatment planning tool for most patients with SAH.

Key Points

? VR 3D-TOF-MRA offers high diagnostic accuracy for detecting ruptured intracranial aneurysms. ? VR 3D-TOF-MRA helps treatment planning for patients with subarachnoid haemorrhage. ? 3D-TOF-MRA is non-invasive and avoids using ionising radiation or contrast agents.     

Contrast-Enhanced and Time-of-Flight MRA at 3T Compared with DSA for the Follow-Up of Intracranial Aneurysms Treated with the WEB Device

BACKGROUND AND PURPOSE:Imaging follow-up at 3T of intracranial aneurysms treated with the WEB Device has not been evaluated yet. Our aim was to assess the diagnostic accuracy of 3D–time-of-flight MRA and contrast-enhanced MRA at 3T against DSA, as the criterion standard, for the follow-up of aneurysms treated with the Woven EndoBridge (WEB) system.MATERIALS AND METHODS:From June 2011 to December 2014, patients treated with the WEB in our institution, then followed for ≥6 months after treatment by MRA at 3T (3D-TOF-MRA and contrast-enhanced MRA) and DSA within 48 hours were included. Aneurysm occlusion was assessed with a simplified 2-grade scale (adequate occlusion [total occlusion + neck remnant] versus aneurysm remnant). Interobserver and intermodality agreement was evaluated by calculating the linear weighted κ. MRA test characteristics and predictive values were calculated from a 2 × 2 contingency table, by using DSA data as the standard of reference.RESULTS:Twenty-six patients with 26 WEB-treated aneurysms were included. The interobserver reproducibility was good with DSA (κ = 0.71) and contrast-enhanced-MRA (κ = 0.65) compared with moderate with 3D-TOF-MRA (κ = 0.47). Intermodality agreement with DSA was fair with both contrast-enhanced MRA (κ = 0.36) and 3D-TOF-MRA (κ = 0.36) for the evaluation of total occlusion. For aneurysm remnant detection, the prevalence was low (15%), on the basis of DSA, and both MRA techniques showed low sensitivity (25%), high specificity (100%), very good positive predictive value (100%), and very good negative predictive value (88%).CONCLUSIONS:Despite acceptable interobserver reproducibility and predictive values, the low sensitivity of contrast-enhanced MRA and 3D-TOF-MRA for aneurysm remnant detection suggests that MRA is a useful screening procedure for WEB-treated aneurysms, but similar to stents and flow diverters, DSA remains the criterion standard for follow-up.

Endovascular treatment is now the first-line treatment for the management of ruptured and unruptured intracranial aneurysms.^1–4 However, the limitations of standard coiling for complex aneurysms (large, wide-neck, or developed in a bifurcation) have contributed to the development of new endovascular approaches, including balloon-assisted coiling, stent-assisted coiling, flow diversion, and flow disruption.⁵The Woven EndoBridge (WEB) aneurysm embolization system (Sequent Medical, Aliso Viejo, California) is an intrasaccular device designed to disrupt the intra-aneurysmal flow at the level of the neck.^6,7 Initial experience with the WEB–Dual-Layer (DL) showed the clinical utility of this device in wide-neck bifurcation aneurysms with high technical success and low acute morbidity and mortality.^6–16 Several WEB devices are now available, including Single-Layer (WEB-SL), Single-Layer Sphere (WEB-SLS), and WEB-DL subtypes.^12,13 Recently, Enhanced-Visualization (EV) versions were developed to improve fluoroscopic visualization of the devices during treatment.Because of the potential risk of aneurysm recanalization after endovascular treatment, regular imaging follow-up is recommended. Digital subtraction angiography is the criterion standard for the follow-up of intracranial aneurysms after endovascular treatment but has some disadvantages, including potential neurologic complications, iodinated contrast injection, and radiation exposure. With the goal of avoiding DSA drawbacks, several MR angiography techniques have been tested to follow intracranial aneurysms. 3D-TOF-MRA and contrast-enhanced MRA (CE-MRA) at 3T are appropriate techniques for the follow-up of coiled aneurysms but have some limitations for the aneurysms treated with stents or flow diverters.^17–23 Because the WEB is a relatively new device, the value of 3D-TOF-MRA and CE-MRA for the follow-up of WEB-treated intracranial aneurysms has been evaluated in a small number of patients at 1.5T.²⁴The aim of this single-center prospective study was to assess the diagnostic accuracy of 3D-TOF-MRA and CE-MRA at 3T against DSA, as the criterion standard, for the evaluation of aneurysm occlusion after WEB treatment.     

Characterization of aneurysm remnants after endovascular treatment: contrast-enhanced MR angiography versus catheter digital subtraction angiography

BACKGROUND AND PURPOSE: A substantial percentage of coiled aneurysms are associated with persistent filling of an aneurysmal component due to incomplete initial treatment or re-growth. Traditionally follow-up of coiled aneurysms has consisted of repeated intra-arterial cerebral catheter angiography, an invasive procedure with associated risks. Hence, many authors have advocated the use of non-invasive imaging techniques for this purpose. Our aim was to compare contrast-enhanced MR angiography (CE-MRA) with digital subtraction angiography (DSA) for depiction of aneurysmal remnants of coiled cerebral aneurysms.MATERIALS AND METHODS: Aneurysms coiled between September 2003 and October 2006 were retrospectively reviewed. We included patients meeting the following criteria: 1) residual/recurrent aneurysm measuring 2 mm or greater, and 2) CE-MRA and DSA performed no more than 60 days apart. Three readers were asked to determine which technique was superior for characterization of the aneurysmal remnant: CE-MRA, DSA, or indeterminate. Statistical analysis included most rule and κ statistics.RESULTS: Of 232 patients who underwent coiling, 44 met the inclusion criteria (33 women and 11 men; 24–72 years of age). Sixteen patients had neck remnants and 28 had body remnants. The first study to identify the remnant was DSA in 35 patients and CE-MRA in 9. In 32 patients (32/44, 73%), the readers indicated that CE-MRA was superior to DSA for remnant characterization. CE-MRA and DSA were thought to be equivalent in 7 (16%), and DSA was preferred in 3 (7%). Two cases (5%) yielded ambiguous results. Of the 28 body remnants, 22 (78.6%) were characterized by remnant protrusion into the coil mass: In 20 of these (91%), the readers preferred CE-MRA over DSA, and in 2 cases (9%), the techniques were thought to be equivalent.CONCLUSION: In patients with known aneurysm remnants, CE-MRA is at least equivalent to DSA for characterization of aneurysmal remnants after coiling. Contrast filling within the coil mass was more clearly seen with CE-MRA than with DSA.

Since the publication of the International Subarachnoid Aneurysm Trial,¹ intracranial aneurysms are increasingly treated with endovascular coiling. A substantial percentage of coiled aneurysms are associated with persistent filling of an aneurysmal component either due to incomplete initial treatment or regrowth.^1,2 Reconfiguration of the coil mass with time results in a recurrent aneurysmal neck or body remnant,^3,4 which leads to reperfusion of the aneurysm, exposing the patient to a risk of rupture and rebleeding.¹ For this reason, follow-up imaging (surveillance) of coiled aneurysms is important. When a considerable aneurysmal remnant is identified, recoiling is commonly advised. Traditionally this surveillance has consisted of repeated digital substraction angiography (DSA) in the months and years following the initial endovascular coiling. DSA is, however, an invasive procedure with well-known associated risks.⁵ Additional disadvantages include a short postprocedural hospital stay, radiation exposure, allergic or nephrotoxic effects of iodinated contrast medium, and patient discomfort and expense. Hence, many authors have developed and advocated the use of noninvasive imaging techniques for the surveillance of aneurysm postcoiling.^6-15The accuracy and reliability of contrast-enhanced MR angiography (CE-MRA) to identify an aneurysm recurrence in coiled patients has been established.^6,7,10,13 Although it is now recognized that CE-MRA is not devoid of risks,^16,17 these risks are negligible and avoidable, compared with those of DSA. The purpose of this trial was to further evaluate the performance of CE-MRA for the depiction of the size and configuration of these aneurysmal remnants compared with DSA (the gold standard). This trial will help further define the role of noninvasive imaging in the surveillance of patients with previously coiled aneurysms.     

Comparison of 3D TOF-MRA and 3D CE-MRA at 3 T for imaging of intracranial aneurysms

Purpose

To compare 3 T elliptical-centric CE MRA with 3 T TOF MRA for the detection and characterization of unruptured intracranial aneurysms (UIAs), by using digital subtracted angiography (DSA) as reference.

Materials and methods

Twenty-nine patients (12 male, 17 female; mean age: 62 years) with 41 aneurysms (34 saccular, 7 fusiform; mean diameter: 8.85 mm [range 2.0–26.4 mm]) were evaluated with MRA at 3 T each underwent 3D TOF-MRA examination without contrast and then a 3D contrast-enhanced (CE-MRA) examination with 0.1 mmol/kg bodyweight gadobenate dimeglumine and k-space elliptic mapping (Contrast ENhanced Timing Robust Angiography [CENTRA]). Both TOF and CE-MRA images were used to evaluate morphologic features that impact the risk of rupture and the selection of a treatment. Almost half (20/41) of UIAs were located in the internal carotid artery, 7 in the anterior communicating artery, 9 in the middle cerebral artery and 4 in the vertebro-basilar arterial system.All patients also underwent DSA before or after the MR examination.

Results

The CE-MRA results were in all cases consistent with the DSA dataset. No differences were noted between 3D TOF-MRA and CE-MRA concerning the detection and location of the 41 aneurysms or visualization of the parental artery. Differences were apparent concerning the visualization of morphologic features, especially for large aneurysms (>13 mm). An irregular sac shape was demonstrated for 21 aneurysms on CE-MRA but only 13/21 aneurysms on 3D TOF-MRA. Likewise, CE-MRA permitted visualization of an aneurismal neck and calculation of the sac/neck ratio for all 34 aneurysms with a neck demonstrated at DSA. Conversely, a neck was visible for only 24/34 aneurysms at 3D TOF-MRA. 3D CE-MRA detected 15 aneurysms with branches originating from the sac and/or neck, whereas branches were recognized in only 12/15 aneurysms at 3D TOF-MRA.

Conclusion

For evaluation of intracranial aneurysms at 3 T, 3D CE-MRA is superior to 3D TOF-MRA for assessment of sac shape, detection of aneurysmal neck, and visualization of branches originating from the sac or neck itself, if the size of the aneurysm is greater than 13 mm. 3 T 3D CE-MRA is as accurate and effective as DSA for the evaluation of UIAs.     

The accuracy and utility of contrast-enhanced MR angiography for localization of spinal dural arteriovenous fistulas: the Toronto experience

Objectives

The purpose of this study was to determine the accuracy and utility of contrast-enhanced MR angiography (CE-MRA) in spinal dural arteriovenous fistulas (SDAVF).

Methods

A retrospective analysis from 1999–2012 identified 70 patients clinically suspected of harboring a SDAVF. Each patient underwent consecutive conventional MR-imaging, CE-MRA, and digital subtraction angiography (DSA). The presence or absence of serpentine flow voids, T2-weighted hyperintensity, and cord enhancement were evaluated, as well as location of the fistula as predicted by CE-MRA. DSA was used as the reference standard.

Results

Of the 70 cases, 53 were determined to be a SDAVF, 10 cases were shown to be other forms of vascular malformation, and 7 were DSA-negative. On MRI, all reported cases of SDAVF showed serpentine flow voids (100 %). T2-weighted hyperintensity was seen in 48 of 50 cases (96 %), extending to the conus in 41 of 48 cases (85 %). Cord enhancement was seen in 38 of 41 cases (93 %). CE-MRA correctly localized the SDAVF in 43 of the 53 cases (81 %).

Conclusions

CE-MRA is a useful non-invasive examination for the detection and localization of SDAVF. CE-MRA facilitates but does not replace DSA as confirmation of location, fistula type, and arterial detail, which are required before treatment.

Key Points

? CE-MRA correctly localized the site of the SDAVF in over 80 % of cases. ? CE-MRA facilitates diagnostic DSA and expedites the diagnostic process. ? CE-MRA does not replace diagnostic DSA in SDAVF cases as confirmative test. ? CE-MRA provides better understanding of missed or mislocalized SDAVF cases.     

Time-of-Flight Magnetic Resonance Angiography for Follow-Up of Coil Embolization with Enterprise Stent for Intracranial Aneurysm: Usefulness of Source Images

Objective

The aim of this study was to determine the interobserver and intermodality agreement in the interpretation of time-of-flight (TOF) MR angiography (MRA) for the follow-up of coiled intracranial aneurysms with the Enterprise stent.

Materials and Methods

Two experienced neurointerventionists independently reviewed the follow-up MRA studies of 40 consecutive patients with 44 coiled aneurysms. All aneurysms were treated with assistance from the Enterprise stent and the radiologic follow-up intervals were greater than 6 months after the endovascular therapy. Digital subtraction angiography (DSA) served as the reference standard. The degree of aneurysm occlusion was determined by an evaluation of the maximal intensity projection (MIP) and source images (SI) of the TOF MRA. The capability of the TOF MRA to depict the residual flow within the coiled aneurysms and the stented parent arteries was compared with that of the DSA.

Results

DSA showed stable occlusions in 25 aneurysms, minor recanalization in 8, and major recanalization in 11. Comparisons between the TOF MRA and conventional angiography showed that the MIP plus SI had almost perfect agreement (κ = 0.892, range 0.767 to 1.000) and had better agreement than with the MIP images only (κ = 0.598, range 0.370 to 0.826). In-stent stenosis of more than 33% was observed in 5 cases. Both MIP and SI of the MRA showed poor depiction of in-stent stenosis compared with the DSA.

Conclusion

TOF MRA seemed to be reliable in screening for aneurysm recurrence after coil embolization with Enterprise stent assistance, especially in the evaluation of the SI, in addition to MIP images in the TOF MRA.     

Accuracy of 3 T MR angioraphy in vertebral artery stenosis and coincidence with other cerebrovascular stenoses

Introduction

Ostium of vertebral artery (VA) is a common site of pseudostenosis on contrast-enhanced MR angiography (CE-MRA). The purpose of this study was to determine the diagnostic accuracy of CE-MRA at 3 T in the evaluation of ostial stenosis of VA and to find associated coincidental stenoses using logistic regression analysis.

Methods

One hundred and thirty-five VA ostial regions from 72 patients who received CE-MRA of neck vessels, intracranial time of flight (TOF) MRA, and digital subtraction angiography (DSA) were retrospectively reviewed. The sensitivity and specificity of the CE-MRA in detection of ostial stenosis were calculated with reference standard of DSA. Ostial stenosis on MRA was correlated with coincidental lesions in intracranial and cervical arteries by logistic regression analysis.

Results

The sensitivity and specificity of the CE-MRA were 100% and 80.4% for detection of significant stenosis. In case of significant stenoses, CE-MRA showed a tendency of overestimation with a false-positive rate of 52.5%. Logistic regression analysis showed that the stenoses of middle cerebral artery (MCA) on TOF MRA was associated with significant stenoses of VA ostia (OR?=?5.84, 95% confidence intervals 1.41–24.17).

Conclusion

CE-MRA is sensitive in detection of VA ostial stenosis although it has high false-positive rate. True positive ostial stenosis should be considered in cases of coincidental stenoses of MCA on TOF MRA.     

Patency of runoff detected by MR angiography at 3.0 T with cuff-compression: a predictor of successful endovascular recanalization below the knee

Objectives

Our aim was to assess the reliability of detecting distal runoff vessels using contrast-enhanced MR angiography (CE-MRA) that were occult on digital subtraction angiography (DSA) for predicting the outcome of endovascular recanalization (ER).

Methods

This retrospective analysis comprised 63 patients with diabetes (98 limbs) who underwent ER for infrapopliteal lesions. Before ER, they underwent CE-MRA and DSA for peripheral arterial disease; runoff vessels were detected with CE-MRA, but not with DSA. Immediate and follow-up postoperative outcomes were assessed. Univariate analysis was performed to identify variables associated with successful ER.

Results

Successful ER was achieved in 85.7 % of limbs, and runoff score was significantly lower than in failure limbs (5.1?±?1.1 vs. 6.2?±?1.3; P?Restenosis/occlusion rate was higher for patients with CLI at 12 months (48.8 % vs. 96.3 % in claudication; P?P?Conclusion Runoff vessels detected using CE-MRA could indicate immediate success and better outcome of ER for infrapopliteal occlusions.

Key Points

? 3-T MRA with cuff compression displayed distal below-the-knee (BTK) runoffs better than DSA ? Detected runoffs indicate high recanalization rate and good clinical outcome ? Runoff display provides potential opportunity to perform other backup recanalization strategies     

Time-of-flight MR angiography at 3T versus digital subtraction angiography in the imaging follow-up of 51 intracranial aneurysms treated with coils

Objective

To compare 3D time-of-flight MR angiography (TOF-MRA) at 3 Tesla (3 T) with digital subtraction angiography (DSA) for the evaluation of intracranial aneurysm occlusion after endovascular coiling.

Methods

In a prospective study, 51 consecutive patients (25 females, 26 males; median age, 51 years) with 51 saccular aneurysms treated with endovascular coiling underwent simultaneous DSA and 3 T TOF-MRA at follow-up. DSA and TOF-MRA images were analyzed independently by two senior neuroradiologists. Findings were assigned to 1 of 3 categories in the Raymond classification: complete obliteration, residual neck or residual aneurysm. Agreement between observers and techniques was evaluated using κ statistics.

Results

DSA images were not interpretable for one patient. Interobserver agreement was determined as excellent for DSA (κ = 0.86) and TOF-MRA (κ = 0.80). After reaching a consensus, DSA follow-up showed 26 (51%) complete obliterations, 20 (39%) residual necks and 4 (8%) residual aneurysms. TOF-MRA showed 23 (45%) complete obliterations, 22 (43%) residual necks and 6 (12%) residual aneurysms. Comparison between TOF-MRA and DSA showed excellent agreement between the techniques (κ = 0.86). In the four cases that were misclassified, TOF-MRA findings were assigned to a higher class than for DSA.

Conclusion

TOF-MRA at 3 T is at least as efficient as DSA for the evaluation of intracranial aneurysm occlusion after endovascular treatment with detachable coils. We suggest that TOF-MRA at 3 T might be used as the primary method for imaging follow-up of coiled intracranial aneurysms.     

Comparison of 3D computer-aided with manual cerebral aneurysm measurements in different imaging modalities

Introduction

To compare intra- and inter-observer reliability of aneurysm measurements obtained by a 3D computer-aided technique with standard manual aneurysm measurements in different imaging modalities.

Methods

A total of 21 patients with 29 cerebral aneurysms were studied. All patients underwent digital subtraction angiography (DSA), contrast-enhanced (CE-MRA) and time-of-flight magnetic resonance angiography (TOF-MRA). Aneurysm neck and depth diameters were manually measured by two observers in each modality. Additionally, semi-automatic computer-aided diameter measurements were performed using 3D vessel surface models derived from CE- (CE-com) and TOF-MRA (TOF-com) datasets. Bland–Altman analysis (BA) and intra-class correlation coefficient (ICC) were used to evaluate intra- and inter-observer agreement.

Results

BA revealed the narrowest relative limits of intra- and inter-observer agreement for aneurysm neck and depth diameters obtained by TOF-com (ranging between ±5.3 % and ±28.3 %) and CE-com (ranging between ±23.3 % and ±38.1 %). Direct measurements in DSA, TOF-MRA and CE-MRA showed considerably wider limits of agreement. The highest ICCs were observed for TOF-com and CE-com (ICC values, 0.92 or higher for intra- as well as inter-observer reliability).

Conclusion

Computer-aided aneurysm measurement in 3D offers improved intra- and inter-observer reliability and a reproducible parameter extraction, which may be used in clinical routine and as objective surrogate end-points in clinical trials.     

Stability of intracranial aneurysms adequately occluded 6 months after coiling: a 3T MR angiography multicenter long-term follow-up study

BACKGROUND AND PURPOSE: The long-term fate of coiled intracranial aneurysms is largely unknown, and prolonged imaging follow-up has been advocated. The yield of follow-up imaging in coiled aneurysms adequately occluded at 6 months is unknown. In such patients, we performed time-of-flight MR angiography (MRA) to assess the incidence and therapeutic consequences of reopening 5–11 years after coiling.MATERIALS AND METHODS: Between 1995 and 2002, 661 aneurysms in 607 patients were coiled in 3 participating centers. Six-month follow-up angiograms were obtained in 497 (75%) aneurysms, of which 316 (64%) in 297 patients were adequately occluded. Of 297 patients, 84 were excluded for various reasons and 73 could not be traced. Of 140 eligible patients, 104 (74%) with 111 aneurysms were studied with 3T MR imaging and high-resolution MRA at a mean of 6.0 years after coiling (median, 5.6 years; range, 5.0–10.6 years).RESULTS: The proportion of aneurysms with reopening was 3.6% (4/111; 95% confidence interval [CI], 1.1%–9.2%). One reopened aneurysm, which initially contained intraluminal thrombus, was additionally coiled (0.9%; 95% CI, 0.0%–5.4%).CONCLUSION: In intracranial aneurysms with adequate occlusion at 6 months after coiling, the proportion of reopening needing retreatment after >5 years is low. The number of reopened aneurysms with therapeutic consequences was too small to assess risk factors, but probably the presence of intraluminal thrombus is one such risk factor. Most patients with coiled intracranial aneurysms that are adequately occluded at 6 months might not need prolonged imaging follow-up.

Endovascular embolization with detachable coils has become an established technique for the treatment of patients with intracranial aneurysms.^1,2 In approximately 15%–40% of patients, the coiled aneurysm reopens at follow-up due to coil compaction or resolution of intraluminal thrombus.^3-13 The most important and constantly found risk factors for reopening with time are large aneurysm size, low packing attenuation, initial incomplete occlusion, and the initial presence of intraluminal thrombus. Risk factors in some but not all studies are rupture status, aneurysm location, and neck size. In several studies, more first-time recurrences were found with longer follow-up.^4,5,8 In contrast, we found in a previous study of 164 aneurysms with angiographic follow-up at fixed intervals of 6 and 18 months that all aneurysm recurrences were apparent at first angiographic follow-up and aneurysms that were adequately occluded at 6 months remained so at the 18-month interval.³ We postulate that if this stability of aneurysm occlusion between 6 and 18 months could be confirmed in a longer follow-up study, it could have important consequences for the follow-up strategy of coiled intracranial aneurysms. In this long-term follow-up study, we performed 3T MR imaging and MR angiography (MRA), 5–11 years after coiling, in a sample of a large multicenter cohort of patients with aneurysms that were adequately occluded at first angiographic follow-up at 6 months to assess the incidence and therapeutic consequences of long-term reopening.     

Long-term MRA follow-up after coiling of intracranial aneurysms: impact on mood and anxiety

Introduction

Magnetic resonance angiography (MRA) screening for recurrence of a coiled intracranial aneurysm and formation of new aneurysms long-term after coiling may induce anxiety and depression. In coiled patients, we evaluated effects on mood and level of anxiety from long-term follow-up MRA in comparison to general population norms.

Methods

Of 162 patients participating in a long-term (>4.5?years) MRA follow-up after coiling, 120 completed the EQ-5D questionnaire, a visual analog health scale and a self-developed screening related questionnaire at the time of MRA. Three months later, the same questionnaires were completed by 100 of these 120 patients. Results were compared to general population norms adjusted for gender and age.

Results

Any problem with anxiety or depression was reported in 56 of 120 patients (47%; 95%CI38?56%) at baseline and 42 of 100 patients (42%; 95%CI32?52%) at 3?months, equally for screen-positives and -negatives. Compared to the reference population, participants scored 38% (95%CI9?67%) and 27% (95%CI4?50%) more often any problem with anxiety or depression. Three months after screening, 21% (20 of 92) of screen-negatives and 13% (one of eight) of screen-positives reported to be less afraid of subarachnoid hemorrhage (SAH) compared to before screening. One of eight screen-positives reported increased fear of SAH.

Conclusions

Patients with coiled intracranial aneurysms participating in long-term MRA screening reported significantly more often to be anxious or depressed than a reference group. Screening did not significantly increase anxiety or depression temporarily. However, subjectively, patients did report an increase in anxiety caused by screening, which decreased after 3?months.     

Three-dimensional time-of-flight (3D TOF) magnetic resonance angiography (MRA) and contrast-enhanced MRA of intracranial aneurysms treated with platinum coils

Background: Contrast-enhanced magnetic resonance angiography (CE-MRA) is less prone to flow-related signal intensity loss than three-dimensional time-of-flight (3D TOF) MRA and may therefore be more sensitive for detection of residual patency in platinum coil-treated intracranial aneurysms.

Purpose: To compare MRA and CE-MRA in the follow-up of intracranial aneurysms treated with platinum coils.

Material and Methods: CE-MRA and 3D TOF MRA (pre- and postcontrast injection) of the intracranial vasculature was performed at 1.5T in 38 patients (47 aneurysms) referred for DSA in the follow-up of coiled intracranial aneurysms.

Results: DSA showed aneurysm patency in 22/47 investigations. Patent aneurysm components were observed with CE-MRA in 18/22 cases, and with 3D TOF MRA in 21/22 cases. There was no significant difference in patent aneurysm component size between CE-MRA and 3D TOF MRA. In addition, CE-MRA showed six, 3D TOF MRA before contrast injection showed seven, and 3D TOF MRA after contrast injection showed eight cases with patent aneurysm components not observed on DSA.

Conclusion: 3D TOF MRA was highly sensitive for detection of patent aneurysm components, and at least as sensitive as CE-MRA. Residual aneurysm patency seems to be better visualized with MRA than with DSA in some cases.     

Correlation of aneurysm occlusion with actual metal coverage at neck after implantation of flow-diverting stent in rabbit models

Introduction

A remarkable curing rate has been achieved in the treatment of intracranial intractable aneurysms by using flow-diverting stents (FDS). An appropriate metal coverage (MC) of this device influences the hemodynamics of aneurysm significantly but little to branches in vitro. The MC changes after elongation or compression and the actual changes are still unknown in vivo. In this paper, we analyzed the correlation of aneurysm occlusion with actual MC after implantation of FDS in rabbit models.

Methods

FDS was implanted across the necks of 22 elastase-induced aneurysms in rabbits. Animals were performed for angiography at 4?weeks and sacrificed at 3?months after angiography for pathology. Tissue was explanted with stent for micro-computed tomography scan, and local shape of stent at neck was reconstructed. Actual MC at neck was calculated, and the correlations of aneurysm occlusion with effective factors were analyzed.

Results

Greater than 95% angiographic aneurysm occlusion rates for the FDS, which covered the neck of aneurysms, were 61.9% at 4?weeks and 57.9% by angiography at 3?months. Aneurysm occlusion was positively correlated with local MC of stent at neck (r _s?=?0.486; P?=?0.026). A 35% actual MC at the neck predicted greater than 95% angiographic aneurysm occlusion with a specificity of 100% and sensitivity of 53.8%.

Conclusion

Aneurysm occlusion was positively correlated with local MC of stent at the neck. The FDS with 35% MC can predict greater than 95% angiographic aneurysm occlusion.     

Angiographic CT with intravenous contrast agent application for monitoring of intracranial flow diverting stents

Introduction

Intracranial flow diverting devices are increasingly used to treat cerebral aneurysms. A reliable, non-invasive follow-up modality would be desirable. Our aim was to compare intra-arterial digital subtraction angiography (ia DSA) to angiographic computed tomography with intravenous contrast agent application (iv ACT) in the visualisation of flow diverting devices and aneurysm lumina.

Methods

Follow-up monitoring by iv ACT (n?=?36) and ia DSA (n?=?25) in 14 patients treated with flow diverting devices for intracranial aneurysms was evaluated retrospectively. Images were evaluated by two neuroradiologists in anonymous consensus reading regarding the device deployment, wall apposition, neck coverage of the aneurysm, opacification of the vessel and device lumen, as well as the degree of aneurysm occlusion.

Results

Corresponding ia DSA and iv ACT images were scored identically in all patients regarding the stent deployment, wall apposition and neck coverage, as well as the degree of aneurysm occlusion and patency status of the device and parent artery. Opacification of the parent vessel lumen and perfused parts of the aneurysm was considered slightly inferior for iv ACT in comparison with ia DSA (seven of 36 cases), without impact on diagnosis.

Conclusions

We demonstrated the feasibility and diagnostic value of iv ACT in follow-up imaging of intracranial flow diverting devices. Due to its high spatial resolution and non-invasive character, this novel technique might become a valuable imaging modality in these patients.     

3D FIESTA pulse sequence for assessing renal artery stenosis: is it a reliable application in unenhanced magnetic resonance angiography?

Objectives

To assess the capability of the three-dimensional (3D) Fast Imaging Employing Steady-State Acquisition (FIESTA) sequence in evaluating renal artery stenosis (RAS).

Methods

We retrospectively analysed 79 patients referred for suspected RAS, examined by 3D FIESTA and contrast-enhanced magnetic resonance angiography (CE-MRA), using a 1.5T whole-body scanner. Image quality was assessed as well as the presence and grade of RAS. Patients with RAS?≥?50 % were evaluated for possible digital subtraction angiography (DSA). Sensitivity, specificity, negative predictive value (NPV), positive predictive value (PPV), and accuracy of 3D FIESTA were calculated with ROC analysis using CE-MRA and DSA as the standard of reference.

Results

A total of 186 renal arteries were assessed; 36 had RAS?≥?50 % demonstrated by CE-MRA. Ten patients underwent DSA, for a total evaluation of 22 arteries. Sensitivity, specificity, NPV, PPV, and accuracy of 3D FIESTA were 91.7 %, 100 %, 98 %, 100 %, and 98 %, respectively, as compared to CE-MRA, and 88.2 %, 100 %, 71.4 %, 100 %, and 91 %, respectively, as compared to DSA. The area under the ROC curve (AUC) of 3D FIESTA as compared to CE-MRA and DSA was 0.958 and 0.941, respectively.

Conclusions

Our study demonstrated the capability of the 3D FIESTA sequence in evaluating RAS, with high-quality images and good diagnostic accuracy.

Key Points

? The 3D FIESTA sequence provides a robust evaluation of RAS. ? The 3D FIESTA sequence allows non-invasive evaluation of the renal arteries. ? The 3D FIESTA sequence could be a useful tool in evaluating RAS.