Reliability of Synthetic Brain MRI for Assessment of Ischemic Stroke with Phantom Validation of a Relaxation Time Determination Method

• Main Authors: Chia-Wei Li, Ai-Ling Hsu, Chi-Wen C. Huang, Shih-Hung Yang, Chien-Yuan Lin, Charng-Chyi Shieh, Wing P. Chan
• Format: Article
• Language: English
• Published: MDPI AG 2020-06-01
• Series: Journal of Clinical Medicine
• Subjects: brain; magnetic resonance imaging; technology; white matter
• Online Access: https://www.mdpi.com/2077-0383/9/6/1857

The reliability of relaxation time measures in synthetic magnetic resonance images (MRIs) of homemade phantoms were validated, and the diagnostic suitability of synthetic imaging was compared to that of conventional MRIs for detecting ischemic lesions. Phantoms filled with aqueous cupric-sulfate (CuSO₄) were designed to mimic spin-lattice (T₁) and spin-spin (T₂) relaxation properties and were used to compare their accuracies and stabilities between synthetic and conventional scans of various brain tissues. To validate the accuracy of synthetic imaging in ischemic stroke diagnoses, the synthetic and clinical scans of 18 patients with ischemic stroke were compared, and the quantitative contrast-to-noise ratios (CNRs) were measured, using the Friedman test to determine significance in differences. Results using the phantoms showed no significant differences in the interday and intersession synthetic quantitative T₁ and T₂ values. However, between synthetic and referenced T₁ and T₂ values, differences were larger for longer relaxation times, showing that image intensities in synthetic scans are relatively inaccurate in the cerebrospinal fluid (CSF). Similarly, CNRs in CSF regions of stroke patients were significantly different on synthetic T₂-weighted and T₂-fluid-attenuated inversion recovery images. In contrast, differences in stroke lesions were insignificant between the two. Therefore, interday and intersession synthetic T₁ and T₂ values are highly reliable, and discrepancies in synthetic T₁ and T₂ relaxation times and image contrasts in CSF regions do not affect stroke lesion diagnoses. Additionally, quantitative relaxation times from synthetic images allow better estimations of ischemic stroke onset time, consequently increasing confidence in synthetic MRIs as diagnostic tools for ischemic stroke.