PT  - JOURNAL ARTICLE
AU  - Raslau, F.D.
AU  - Lin, L.Y.
AU  - Andersen, A.H.
AU  - Powell, D.K.
AU  - Smith, C.D.
AU  - Escott, E.J.
TI  - Peeking into the Black Box of Coregistration in Clinical fMRI: Which Registration Methods Are Used and How Well Do They Perform?
AID  - 10.3174/ajnr.A5846
DP  - 2018 Dec 01
TA  - American Journal of Neuroradiology
PG  - 2332--2339
VI  - 39
IP  - 12
4099  - http://www.ajnr.org/content/39/12/2332.short
4100  - http://www.ajnr.org/content/39/12/2332.full
SO  - Am. J. Neuroradiol.2018 Dec 01; 39
AB  - BACKGROUND AND PURPOSE: Interpretation of fMRI depends on accurate functional-to-structural alignment. This study explores registration methods used by FDA-approved software for clinical fMRI and aims to answer the following question: What is the degree of misalignment when registration is not performed, and how well do current registration methods perform?MATERIALS AND METHODS: This retrospective study of presurgical fMRI for brain tumors compares nonregistered images and 5 registration cost functions: Hellinger, mutual information, normalized mutual information, correlation ratio, and local Pearson correlation. To adjudicate the accuracy of coregistration, we edge-enhanced echo-planar maps and rated them for alignment with structural anatomy. Lesion-to-activation distances were measured to evaluate the effects of different cost functions.RESULTS: Transformation parameters were congruent among Hellinger, mutual information, normalized mutual information, and the correlation ratio but divergent from the local Pearson correlation. Edge-enhanced images validated the local Pearson correlation as the most accurate. Hellinger worsened misalignment in 59% of cases, primarily exaggerating the inferior translation; no cases were worsened by the local Pearson correlation. Three hundred twenty lesion-to-activation distances from 25 patients were analyzed among nonregistered images, Hellinger, and the local Pearson correlation. ANOVA analysis revealed significant differences in the coronal (P < .001) and sagittal (P = .04) planes. If registration is not performed, 8% of cases may have a >3-mm discrepancy and up to a 5.6-mm lesion-to-activation distance difference. If a poor registration method is used, 23% of cases may have a >3-mm discrepancy and up to a 6.9-mm difference.CONCLUSIONS: The local Pearson correlation is a special-purpose cost function specifically designed for T2*–T1 coregistration and should be more widely incorporated into software tools as a better method for coregistration in clinical fMRI.AFNIAnalysis of Functional Neuro ImagesCRcorrelation ratioHELHellingerLADlesion-to-activation distanceLPClocal Pearson correlationMImutual informationNMInormalized mutual informationNRnonregistered