3T magnetic resonance arteriography in pediatric cerebrovascular disease

Assessment of Moyamoya disease with 3.0-T magnetic resonance angiography and magnetic resonance imaging versus conventional angiography

3.0-T magnetic resonance (MR) angiography and MR imaging were compared with conventional angiography for the evaluation of moyamoya disease in 13 preoperative patients (26 hemispheres) with moyamoya disease (4 males and 9 females aged 21-54 years). The correlation between MR angiography scores determined by modified Houkin's grading system (MRA score) and conventional angiography stages determined by Suzuki's grading system (CA stage) was analyzed. Other MR findings such as moyamoya vessel scores, "ivy sign" scores, and the presence of small, medium, and large cerebrovascular attack (CVA) lesions were compared with CA stages. MRA scores were significantly correlated with CA stages (p < 0.01). Moyamoya vessel scores correlated well with CA stages (p < 0.01). There was no significant correlation between "ivy sign" scores and CA stages, and no significant differences in CA stages with the presence and absence of CVA lesions of any size. 3.0-T MR angiography can be used as a vascular assessment in moyamoya disease with its priority of noninvasive nature and visual clarity compared with conventional angiography. The findings of 3.0-T MR angiography may reflect the steno-occlusive changes in moyamoya disease.

Moyamoya disease: a summary

Moyamoya, meaning a "hazy puff of smoke" in Japanese, is a chronic, occlusive cerebrovascular disease involving bilateral stenosis or occlusion of the terminal portion of the internal carotid arteries (ICAs) and/or the proximal portions of the anterior cerebral arteries and middle cerebral arteries (MCAs). The Ministry of Health and Welfare of Japan has defined 4 types of moyamoya disease (MMD): ischemic, hemorrhagic, epileptic, and "other." The ischemic type has been shown to predominate in childhood, while the hemorrhagic type is more often observed in the adult population. The highest prevalence of MMD is found in Japan, with a higher female to male ratio. Studies have shown a possible genetic association of MMD linked to chromosome 17 in Japanese cases as well as in cases found in other demographics. During autopsy, intracerebral hematoma is found and most commonly serves as the major cause of death in patients with MMD. Moyamoya vessels at the base of the brain are composed of medium-sized or small muscular arteries emanating from the circle of Willis, mainly the intracranial portions of ICAs, anterior choroidal arteries, and posterior cerebral arteries, forming complex channels that connect with distal positions of the MCAs. Off of these channels are small tortuous and dilated vessels that penetrate into the base of the brain at the site of the thalamoperforate and lenticulostriate arteries. On angiography, there is the characteristic stenosis or occlusion bilaterally at the terminal portion of the ICAs as well as the moyamoya vessels at the base of the brain. Six angiographic stages have been described, from Stage 1, which reveals a narrowing of the carotid forks, to Stage 6, in which the moyamoya vessels disappear and collateral circulation is produced solely from the external carotid arteries. Cases with milder symptoms are usually treated conservatively; however, more severe symptomatic cases are treated using revascularization procedures. Surgical treatments are divided into 3 types: direct, indirect, and combined/other methods. Direct bypass includes superficial temporal artery-MCA bypass or use of other graft types. Indirect procedures bring in circulation to the intracranial regions by introducing newly developed vasculature from newly approximated tissues. These procedures may not be enough to prevent further ischemia; therefore, a combination of direct and indirect procedures is more suitable. This article will give a review of the epidemiology, natural history, pathology, pathophysiology, and diagnostic criteria, including imaging, and briefly describe the surgical treatment of MMD.

Brain and spine MRI artifacts at 3Tesla

INTRODUCTION

We illustrate here the most common MRI artifacts found on routine 3T clinical neuroradiology that can simulate pathology and interfere with diagnosis.

MATERIALS AND METHODS

Our group has worked with a 3-T Magnetom Trio (Siemens, Erlangen, Germany) system for two years, with 50% of our time devoted to clinical work and 50% dedicated to research; 65% of the clinical time is dedicated to neuroradiology (2705 patients) and the remaining time to whole-body MRI. We have detected these artifacts during our case readings and have selected the most representative of each type to illustrate here.

RESULTS

We have observed magnetic susceptibility artifacts (29%), pulsation artifacts (57%), homogeneity artifacts (3%), motion artifacts (6%), truncation artifacts (3%) and, finally, artifacts due to poor or inadequate technique in the examined region.

CONCLUSION

High-field imaging offers the benefit of a higher signal-to-noise ratio, thus making possible the options of a higher imaging matrix, thinner slices, the use of spectroscopy and diffusion tensor imaging in the routine clinical neuroradiology with a reduction in time spent. It is vital to be able to recognize these artifacts in everyday practice as they can mimic pathological appearances, thus causing diagnostic errors that could lead to unnecessary treatment. Indeed, most of these artifacts could be avoided with an adequate technique.