Detection of subarachnoid haemorrhage with magnetic resonance imaging

Abstract

Objectives-To measure the sensitivity and specificity of five MRI sequences to subarachnoid haemorrhage. Methods-Forty one patients presenting with histories suspicious of subarachnoid haemorrhage (SAH) were investigated with MRI using T1 weighted, T2 weighted, single shot fast spin echo (express), fluid attenuation inversion recovery (FLAIR), and gradient echo T2* sequences, and also by CT. Lumbar puncture was performed in cases where CT was negative for SAH. Cases were divided into acute (scanned within 4 days of the haemorrhage) and subacute (scanned after 4 days) groups. Results-The gradient echo T2* was the most sensitive sequence, with sensitivities of 94% in the acute phase and 100% in the subacute phase. Next most sensitive was FLAIR with values of 81% and 87% for the acute and subacute phases respectively. Other sequences were considerably less sensitive. Conclusions-MRI can be used to detect subacute and acute subarachnoid haemorrhage and has significant advantages over CT in the detection of subacute subarachnoid haemorrhage. The most sensitive sequence was the gradient echo T2*. (J Neurol Neurosurg Psychiatry 2001;70:205-211) Keywords: magnetic resonance imaging; subarachnoid haemorrhage Computed tomography has been the imaging investigation of choice in cases of suspected subarachnoid haemorrhage (SAH) since its introduction into clinical practice because of high sensitivity to acute SAH, short scan times, and widespread availability. Lumbar puncture is performed in cases of suspected SAH with negative CT.The sensitivity of CT to SAH is more than 90% within 1 day of the haemorrhage 1-3 but falls oV rapidly with time and approaches 0% at 3 weeks.1 4 5 Although much of these data relate to previous generations of scanners, more recent results from higher resolution scanners show only modest improvements.2 3 This is because contrast resolution rather than spatial resolution is the limiting factor for sensitivity. Brain CT remains relatively insensitive to SAH more than a few days old especially in cases where the bleed is small. This is a particular problem as these patients are usually in good condition and have the most to lose from a missed diagnosis of SAH and subsequent rebleed from a ruptured aneurysm.As CT cannot exclude SAH, lumbar puncture is used as the longstop of investigation. Lumbar puncture has the advantage that its sensitivity remains high for several weeks after the ictus. 6Conventional MR T1 and T2 weighted images are relatively insensitive to SAH. Scan times for MRI are longer and allow less access to the patient than CT, making it unsuitable for confused or restless patients. For these reasons MRI has not had a role in the detection of SAH until recently. In 1994 Noguchi et al 7 reported the use of a FLAIR sequence in the detection of SAH in three cases. Since then other reports have confirmed the usefulness of FLAIR in this role. [8][9][10][11][12] There has been general agreement that the sensitivity of MRI to SAH increases over the few days after the bleed. 9 10 13 As...

Double Inversion Recovery MR Sequence for the Detection of Subacute Subarachnoid Hemorrhage

“…13,14 T2* is considered useful for the diagnosis of subacute or chronic SAH. 6,16 This sequence appears effective in detecting a prior SAH indicating the location of a ruptured aneurysm. 16 On T2* images, SAH signal is dependent on the state of oxygenation and the integrity of red blood cell walls.…”

“…13,14 T2* gradient-echo sequences are useful for subacute or chronic SAH depiction. 6,15,16 Susceptibility-weighted imaging uses tissue magnetic-susceptibility differences to generate a unique contrast, based on a 3D flow-compensated gradient-echo sequence. 17 Previous studies have suggested that SWI could accurately detect small amounts of SAH and intraventricular hemorrhage (IVH).…”

“…3 When performed several days after symptom onset, CT does not appear reliable for the diagnosis of SAH 4,5 and is outperformed by brain MR imaging in this setting. 6 Indeed, FLAIR MR imaging is more sensitive than CT for SAH detection at both acute [7][8][9] and subacute 10 stages. 3D FLAIR is even more specific than 2D FLAIR by reducing flow-related artifacts, which are known to provide falsepositive findings on 2D FLAIR.…”

Does oxygen use during general anesthesia cause an artifact in magnetic resonance images?

“…[13][14][15][16] Bu konuda yapılan çok fazla çalışma olmasa da mevcut çalışmalar, anestezi altındaki hastalarda gözlenen HSA için başlıca iki faktörün sorumlu olabileceğini ileri sürmektedirler: kullanılan anestezik maddeler ya da anestezi/sedasyon sırasında hastaya uygulanan oksijen. Bugüne kadar gerçek-leştirilen çalışmalar incelendiğinde, çoğunda anestezi yönteminin standardize edilmemiş olduğu göze çarpmaktadır.…”

The Critical Care Management of Aneurysmal Subarachnoid Hemorrhage

“…MRI offers a higher sensitivity to detect SAH in patients presenting outside of first 48 hours after onset; however MRI is not readily available at most institutions and some patients may not be suitable for MRI. The FLAIR (fluid attenuated inversion recovery) and GRE (gradient echo) sequences are the most reliable method for detection of SAH in MRI [16].…”