High precision anatomy for MEG

• Published in: NeuroImage (Orlando, Fla.) Vol. 86; pp. 583 - 591
• Main Authors: Troebinger, Luzia, López, José David, Lutti, Antoine, Bradbury, David, Bestmann, Sven, Barnes, Gareth
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01.02.2014; Elsevier; Elsevier Limited; Academic Press
• Subjects: 3-D printers; 3D printer; Biological and medical sciences; Brain Mapping - instrumentation; Casts, Surgical; Coregistration; Design; Equipment Design; Equipment Failure Analysis; Fundamental and applied biological sciences. Psychology; Head movement; Head Protective Devices; Humans; Image Enhancement - instrumentation; Longitudinal MEG; Magnetoencephalography; Magnetoencephalography - instrumentation; Magnetoencephalography - methods; Manufacturers; MEG; MSP; Reproducibility of Results; Restraint, Physical - instrumentation; Restraint, Physical - methods; Sensitivity and Specificity; Spatial resolution; Studies; Technical Note; Vertebrates: nervous system and sense organs; Magnetoencephalography; Head movement; 3D printer; Coregistration; Longitudinal MEG; MSP; Spatial resolution; MEG; Anatomy
• ISSN: 1053-8119; 1095-9572; 1095-9572
• DOI: 10.1016/j.neuroimage.2013.07.065

Precise MEG estimates of neuronal current flow are undermined by uncertain knowledge of the head location with respect to the MEG sensors. This is either due to head movements within the scanning session or systematic errors in co-registration to anatomy. Here we show how such errors can be minimized using subject-specific head-casts produced using 3D printing technology. The casts fit the scalp of the subject internally and the inside of the MEG dewar externally, reducing within session and between session head movements. Systematic errors in matching to MRI coordinate system are also reduced through the use of MRI-visible fiducial markers placed on the same cast. Bootstrap estimates of absolute co-registration error were of the order of 1mm. Estimates of relative co-registration error were <1.5mm between sessions. We corroborated these scalp based estimates by looking at the MEG data recorded over a 6month period. We found that the between session sensor variability of the subject's evoked response was of the order of the within session noise, showing no appreciable noise due to between-session movement. Simulations suggest that the between-session sensor level amplitude SNR improved by a factor of 5 over conventional strategies. We show that at this level of coregistration accuracy there is strong evidence for anatomical models based on the individual rather than canonical anatomy; but that this advantage disappears for errors of greater than 5mm. This work paves the way for source reconstruction methods which can exploit very high SNR signals and accurate anatomical models; and also significantly increases the sensitivity of longitudinal studies with MEG. •We introduce MEG coregistration scheme using 3D printed subject specific head casts.•Using this scheme reduces relative/absolute coregistration errors to 1–2mm levels.•The ability to reposition between sessions results in high SNR data sets.•At this level of coregistration error, we see a clear benefit for using individual cortical meshes.