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

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Abstract

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.

Introduction

Endovascular coiling for the treatment of ruptured intracranial aneurysms was introduced in the early nineties and this procedure has become an increasingly popular alternative to microsurgical clipping [1], [2]. However, the outcome of patients treated with platinum coils is not well established. Aneurysm regrowth or neck recurrence may be observed at follow-up [3].

Follow-up imaging is mandatory in order to detect aneurysmal regrowth and to determine the need for further therapy [3], [4]. Digital Subtraction Angiography (DSA) is considered as the reference method for treated aneurysm evaluation [4]. However, DSA is expensive, invasive, time-consuming, and carries a risk of complication [5]. To overcome the drawbacks associated with screening all patients with coiled aneurysms, accurate noninvasive imaging methods are of considerable value. Magnetic resonance angiography (MRA) using a 3D time-of-flight (TOF) technique is considered as an alternative approach to DSA. At 1.5 Tesla (T), previous authors have reported the ability of this technique to detect aneurysm regrowth or neck recurrence [6], [7] but not small residual or recurrent aneurysm [6], [7].

The approximate doubling of signal-to-noise ratio from 1.5 T to 3 T can improve the spatial and contrast resolution of 3 T MRA [8]. The increased T1 times lead to gains in blood-to-background contrast at 3 T MRA [9]. Image quality appears to improve with TOF-MRA at 3 T compared with 1.5 T.

The purpose of this prospective study was to compare TOF-MRA at 3 T with DSA for the evaluation of intracranial aneurysm occlusion after endovascular coiling and to determine whether TOF-MRA at 3 T can replace DSA in the imaging follow-up of coiled intracranial aneurysms.

Section snippets

Study design

To assess the value of TOF-MRA at 3 T for the evaluation of aneurysm occlusion following endovascular treatment with detachable coils, TOF-MRA and DSA were compared. DSA was considered as the reference technique. Patients were prospectively and consecutively included if they harbored intracranial aneurysms treated with coils and if a follow-up angiography was scheduled according to our usual follow-up protocol. Approval by the institutional review board of our hospital was not required because

Complications

Two complications (3.9%) were noted for two patients: one transient aphasia and one groin hematoma.

Image quality

Image quality was considered good, with minor artifacts (coils artifacts) in all but one case. Artifacts were considered major in one case: vessel overlapping was too great for aneurysm assessment. This DSA examination was considered as unreadable.

Artifactual occlusions of parent or branch vessels (partial overlapping of subtracted coils) were observed in seven cases (7/51).

DSA findings

Fifty angiograms were

Discussion

Our findings showed that TOF-MRA at 3 T is totally safe and feasible in the follow-up imaging of aneurysms treated with coils. Our results suggest that this technique is able to show neck or aneurysm permeability better than DSA.

Many authors have studied the role of noninvasive techniques in the necessary follow-up imaging of aneurysms treated with coils [6], [7], [11], [12], [13], [14], [15], [16], [17]. To our knowledge, only one study [7] has compared with few patients TOF-MRA at 3 T with DSA

Conclusion

This study showed that TOF-MRA at 3 T is a totally safe and valuable method for the follow-up of intracranial aneurysms treated with coils. This technique is at least as efficient as DSA and possibly better than TOF-MRA at 1.5 T in the evaluation of flow in intracranial aneurysms treated with coils. In the light of these observations, we suggest that TOF-MRA at 3 T can replace DSA for the follow-up imaging of intracranial aneurysms treated with platinum coils.

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