Abstract TP258: Comparison of 0.23-Tesla MRI and CT for Detection of Subarachnoid Hemorrhage in Emergency Settings

Introduction: Headache ranks as the fifth most common reason for emergency department visits. This common symptom requires careful evaluation to distinguish between benign causes and conditions requiring urgent intervention. Proper triage and assessment of headache in the emergency setting remain challenging, headache may manifest as the sole or predominant presenting symptom in various types of acute stroke, including acute ischemic stroke, subarachnoid hemorrhage (SAH), and intracerebral hemorrhage (ICH). Disorders characterized by prominent headache symptoms, particularly migraine with aura, may elevate the risk of both ischemic and hemorrhagic stroke, underscoring the critical importance of timely imaging to guide appropriate treatment decisions. While CT is fast and widely used, its sensitivity for early ischemia is limited. Previous experimental–clinical study demonstrated that 0.23 T MRI can rapidly and accurately differentiate between stroke types, including cerebral hemorrhage and infarction. However, clinical studies that conduct a comparison of 0.23T MRI and CT in patients with SAH remain unclear. Hypothesis: To evaluate the diagnostic accuracy of portable low-field (0.23 T) MRI for acute SAH. We hypothesized that 0.23 T FLAIR MRI is comparable to CT in detecting SAH. Methods: This study included adults who visited the emergency department of Beijing Tiantan Hospital. Patients who underwent both CT and 0.23T MRI examinations were included in the study. The 0.23-T MRI protocol consisted of diffusion-weighted imaging (DWI), fluid-attenuated inversion recovery (FLAIR), and haematoma enhanced inversion recovery (HEIR) sequences, with a total scan time of 7.2 minutes. Four blinded raters independently assessed image quality and SAH presence. CT served as the reference standard. Sensitivity and specificity of 0.23T MRI for detection of SAH were calculated. Results: We selected 40 cases of SAH, among which 20 patients without positive neurological symptoms. Overall, 0.23-T MRI showed comparable sensitivity and specificity to CT for SAH detection, especially among the patients who underwent scans 24 to 72 hours after the onset of the disease. Figure 1 shows several cases. Conclusion: Low-field 0.23-T FLAIR MRI is comparable to CT in detecting SAH, which indicates that the application of 0.23T low-field MRI in emergency situations maybe reliable.