Noninvasive imaging after stent-assisted coiling of intracranial aneurysms: comparison of 3-T magnetic resonance imaging and 64-row multidetector computed tomography--a pilot study

Abstract

Background and purpose: Follow-up imaging after stent-assisted coiling of intracranial aneurysms is limited by signal loss in the stented vessel segment using magnetic resonance imaging or by streak artifacts caused by aneurysm coils using multidetector computed tomography. In the search for a noninvasive surveillance in this condition, we propose a technique to minimize streak artifacts in multidetector computed tomography by gated data reconstruction and shifting the reconstruction window.

Methods: The effect of the gated data acquisition in 64-row computed tomographic angiography (gCTA) on artifact reduction was evaluated in a preliminary phantom study and compared with nongated CTA, time-of-flight magnetic resonance angiography (TOF-MRA), and digital subtraction angiography (DSA). Scans were also obtained from 5 patients treated with stent-assisted coiling as part of their follow-up protocol. The length of impaired vessel segments (LIVS) in TOF-MRA and gCTA was compared and correlated with the stent's length, the number of coils, and the packing density. The assessment of treatment outcome in TOF-MRA and gCTA was compared with DSA as the standard of reference.

Results: The phantom study revealed 2 aspects: first, a distinct reduction of streak artifacts caused by coils using gated data acquisition; and second, because artifact orientation could be rotated systematically by shifting the reconstruction window, visualization of treated vessel segments was significantly superior in gCTA. In magnetic resonance imaging, all stented vessel segments were characterized by signal loss in both phantom and patients. The LIVS was 78% shorter in gCTA (4.86 ± 6.93 mm) compared with that in TOF-MRA (21.82 ± 7.47 mm, P < 0.01). In TOF-MRA, the LIVS correlated with the stent's length, in gCTA with the number of coils. With regard to assessment of treatment outcome, gCTA and TOF-MRA correlated with DSA in 3 and in none of 5 patients, respectively.

Conclusions: Gated CTA is a promising technique to reduce the amount of artifacts induced by stent-assisted intracranial coils. Image quality and assessment of treatment outcome in patients with stent-assisted coiling is superior compared with TOF-MRA.