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Classifying the Patency of GDC-Treated Aneurysms

February 10, 2010
Written by: , Filed in: Interventional Radiology
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Patients who have undergone treatment of intracranial aneurysms with Guglielmi detachable coils (GDC) need regular follow-up studies to confirm long-term occlusion of the aneurysm, because the coils can change shape, or the aneurysm can grow.

CT evaluation is limited by streak artifact, and the radiation dose is significant, especially since patients will require multiple follow-up studies.

However, 3D time of flight (TOF) and contrast-enhanced MR angiography (CE-MRA) have been demonstrated to be reliable in assessing aneurysm patency, particularly on 3T imaging, which has improved signal intensity-to-noise and/or resolution.

A recent study was conducted to determine whether parallel acquisition technique with CE-MRA or 3D-TOF are superior for follow-up of GDC-treated intracranial aneurysms on 3T imaging.

The study has shown that on 3T MRA imaging with parallel acquisition technique, time-of-flight and contrast-enhanced MRA are similarly effective at classifying patency of coiled aneurysms, but contrast images better demonstrated the patent portion of the aneurysm in this study.

Patients undergoing scheduled routine follow-up of coiled aneurysms.

Non-contrast 3D-TOF images were acquired with 1 x 1 x1-mm voxel size and reconstructed to 0.5 x 0.5 x 1 mm. Time of acquisition was 5 minutes and 40 seconds. CE-MRA was performed following administration of gadobenate dimeglumine with a dose of 0.1 mmol/kg at a rate of 2 mL/second. Imaging time was 24 seconds. Acquisition voxel size was 0.72 x 0.72 x 0.8 mm, reconstructed to 0.43 x 0.43 x 0.4 mm.

Source images as well as various 3D reconstructions were generated. They were evaluated in a randomized order and were classified as occluded or as demonstrating residual patency. If patency was seen, the quality of visualizing the patency was compared.

There were 52 patients with 54 aneurysms. Fifty-three aneurysms were classified equally by both sequences; 21 were occluded, 16 had a residual neck (type I), and 16 were patent (type II).

In 1 giant aneurysm measuring 26 mm, the TOF indicated occlusion, but the CE-MRA demonstrated a residual neck. In addition to this 1 case, the CE-MRA demonstrated the patency better than the TOF in 10 aneurysms with patency.

Eight of these were type II and 2 were type I.

In no case was visualization superior on TOF. In 5 cases on TOF imaging, the parent vessel appeared partially obscured by artifact, but this did not affect evaluation of the vessel.

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3D-TOF and CE-MRA performed on 3T with parallel imaging technique were similarly effective at classifying patency of GDC-treated aneurysms. However, CE-MRA demonstrated improved visualization of patency and fewer artifacts.

Reviewer’s Comments
Although apparently not statistically significant, the fact that 1 aneurysm was misclassified would suggest that CE-MRA should be preferred.

Where contrast is contraindicated, TOF is nearly as reliable for determining whether the aneurysm is occluded or not.

Regarding patent aneurysms, the authors did not comment as to whether improved visualization was clinically significant.

Author: Yaron Lebovitz, MD

Anzalone N, Scomazzoni F, et al. Follow-Up of Coiled Cerebral Aneurysms at 3T: Comparison of 3D Time-of-Flight MR Angiography and Contrast-Enhanced MR Angiography. AJNR; 2008;29 (September): 1530-1536


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