Improving reliability in clinical neuroimaging: a study in transgender persons
Although the neuroanatomy of transgender persons is slowly being charted, findings are presently discrepant. One important factor is the issue of power and low signal-to-noise (SNR) ratio in neuroimaging studies of rare study populations including endocrine or neurological patient groups. The present study assessed whether the reliability of findings across structural anatomical measures including thickness, volume, and surface area could be increased by using two back-to-back within session structural MRI scans in 40 transgender men (TM), 40 transgender women (TW), 30 cisgender men (CM), and 30 cisgender women (CW). Overall, findings in transgender persons were more consistent with at-birth assigned sex in brain volume and surface area while no group differences emerged for cortical thickness. Repeated measures analysis also indicated that having a second scan increased SNR in all ROIs, most notably bilateral frontal poles, accumbens nuclei and putamina. Furthermore, additional significant group differences emerged in cortical surface area when age and ICV were used as covariates. The results suggest that a simple time and cost effective measure to improve signal to noise ratio in rare clinical populations with low prevalence rates is a second anatomical scan when structural MRI is of interest.