Detecting subarachnoid hemorrhage: Comparison of combined FLAIR/SWI versus CT
Introduction
Computed tomography (CT) is the preferred method for routine imaging of patients with suspected subarachnoid hemorrhage (SAH) due to its high sensitivity and wide availability [1], [2]. Until recently, MRI was thought to be less sensitive for detection of SAH. However, recent studies have demonstrated that fluid attenuated inversion recovery (FLAIR) MRI is equal to or even more sensitive than CT for detection of acute or subacute SAH [3], [4], [5]. Both methods have their limitations; CT has a lower sensitivity in the posterior fossa due to beam-hardening artifacts, whereas cerebrospinal fluid (CSF) pulsations, vascular pulsation or supplemental oxygen may cause FLAIR artifacts in the form of hyperintense signal of the subarachnoid spaces [4], [5], [6], [7].
Susceptibility weighted imaging (SWI) is extremely sensitive for susceptibility dephasing from deoxyhemoglobin, hemosiderin, iron and calcium. Hence, SWI is considered to be a sensitive method for the identification of intracranial hemorrhage [8], [9], [10]. Recent work from Wu et al. highlighted the utility of SWI in cases with traumatic SAH [11]. The aim of this study is to make a step further. We hypothesized that a combination of FLAIR and SWI would improve the detection rate compared to CT alone in acute SAH. Another objective is to compare SWI alone with the established methods, FLAIR and CT, in SAH. To our best knowledge, no study has yet compared FLAIR and SWI regarding their differing capacities for detecting SAH in diverse anatomical areas of subarachnoid space, or investigated whether SWI can provide additional information.
Section snippets
Patient data
For this retrospective study, we examined patients with acute SAH admitted to our institution from July 2010 to November 2011. Patients were included if they underwent CT and MRI within 6 days after symptom onset. A total of 25 patients (8 women, 17 men; age range, 13–80 years; mean age, 48.1 years) fulfilled the inclusion criteria (Table 1). Based on the clinical and imaging assessment, the causes of SAH were head trauma (n = 9), ruptured aneurysm (n = 6), ruptured arteriovenous malformation (AVM)
Results
A total of 146 regions with SAH were identified by combining CT, FLAIR and SWI (Table 2). Subdivided in regions, 61 (41.8%) of these hemorrhages were interhemispheric, 34 (23.3%) were located in the Sylvian, basal or mesencephalic cisterns, another 32 (21.9%) were seen in the posterior fossa including the superior cerebellar cistern, and 19 (13.0%) were intraventricular.
CT alone identified less SAH (75.3%), than FLAIR (87.0%) or SWI (88.4%). SWI and FLAIR combined detected all identifiable SAH
Discussion
Detection of SAH with CT depends on the attenuation values of blood and the individual hemoglobin levels [14], [15], [16]. Sensitivity of SAH detection decreases with time with the reduction of hemoglobin concentration. In contrast, signal intensity on FLAIR imaging correlates with cellularity and protein levels, which increase in CSF over time in case of SAH [6], [17]. SWI is widely used for detection of parenchymal hemorrhage due to its sensitivity to blood products [9], [10], [18]. Whereas
Conflict of interest
We declare that we have no conflict of interest.
References (20)
- et al.
Subarachnoid haemorrhage
Lancet
(2007) - et al.
Susceptibility weighted imaging: a new tool in magnetic resonance imaging of stroke
Clinical Radiology
(2009) - et al.
evaluation of subarachnoid hemorrhage: a practical review for the radiologist interpreting emergency room studies
Emergency Radiology
(2009) - et al.
Comparison of magnetic resonance imaging sequences with computed tomography to detect low-grade subarachnoid hemorrhage: Role of fluid-attenuated inversion recovery sequence
Journal of Computer Assisted Tomography
(2006) - et al.
Problems with diagnosis by fluid-attenuated inversion recovery magnetic resonance imaging in patients with acute aneurysmal subarachnoid hemorrhage
Neurologia Medico-Chirurgica
(2010) - et al.
Acute subarachnoid hemorrhage: MR imaging with fluid-attenuated inversion recovery pulse sequences
Radiology
(1995) - et al.
Hyperintensity in the subarachnoid space on FLAIR MRI
American Journal of Roentgenology
(2007) - et al.
Artifacts in computed tomography of the posterior fossa: a comparative phantom study
Journal of Computer Assisted Tomography
(1986) - et al.
Susceptibility weighted imaging (SWI)
Magnetic Resonance in Medicine
(2004) - et al.
Clinical applications of neuroimaging with susceptibility-weighted imaging
Journal of Magnetic Resonance Imaging
(2005)
Cited by (89)
Conventional MR Imaging in Trauma Management in Adults
2023, Neuroimaging Clinics of North AmericaThe Current State of Susceptibility-Weighted Imaging and Quantitative Susceptibility Mapping in Head Trauma
2023, Neuroimaging Clinics of North AmericaModern Imaging of Aneurysmal Subarachnoid Hemorrhage
2023, Radiologic Clinics of North AmericaEmergency Department Neuroimaging for the Sick Child
2022, Emergency Imaging of At-Risk Patients: General PrinciplesThunderclap headache
2022, Headache and Migraine in Practice
- 1
Tel.: +41 31 6322655.