Calculating potential error in sodium MRI with respect to the analysis of small objects. Issue 6 (11th October 2017)

• Record Type: Journal Article
• Authors: Stobbe, Robert W.; Beaulieu, Christian
• Is Part Of: Magnetic resonance in medicine. Volume 79:Issue 6(2018)
• Page Start: 2968
• Page End: 2977
• Publication Date: 2017-10-11
• Subjects: sodium -- MRI -- brain -- quantification -- multiple sclerosis; Nuclear magnetic resonance -- Periodicals; Electron paramagnetic resonance -- Periodicals; 616.07548
• DOI: 10.1002/mrm.26962
• Languages: English
• ISSNs: 0740-3194

Abstract

Abstract : Purpose: To facilitate correct interpretation of sodium MRI measurements, calculation of error with respect to rapid signal decay is introduced and combined with that of spatially correlated noise to assess volume‐of‐interest (VOI) 23 Na signal measurement inaccuracies, particularly for small objects. Methods: Noise and signal decay–related error calculations were verified using twisted projection imaging and a specially designed phantom with different sized spheres of constant elevated sodium concentration. As a demonstration, lesion signal measurement variation (5 multiple sclerosis participants) was compared with that predicted from calculation. Results: Both theory and phantom experiment showed that VOI signal measurement in a large 10‐mL, 314‐voxel sphere was 20% less than expected on account of point‐spread‐function smearing when the VOI was drawn to include the full sphere. Volume‐of‐interest contraction reduced this error but increased noise‐related error. Errors were even greater for smaller spheres (40–60% less than expected for a 0.35‐mL, 11‐voxel sphere). Image‐intensity VOI measurements varied and increased with multiple sclerosis lesion size in a manner similar to that predicted from theory. Correlation suggests large underestimation of 23 Na signal in small lesions. Conclusions: Acquisition‐specific measurement error calculation aids 23 Na MRI data analysis and highlights the limitations of current low‐resolution methodologies. Magn Reson Med 79:2968–2977, 2018. © 2017 International Society for Magnetic Resonance in Medicine.