Purpose: Thalamic nuclei are largely invisible in conventional MRI due to\npoor contrast. Thalamus Optimized Multi-Atlas Segmentation (THOMAS) provides\nautomatic segmentation of 12 thalamic nuclei using white-matter-nulled (WMn)\nMPRAGE sequence at 7T. Application of THOMAS to Magnetization Prepared 2 Rapid\nGradient Echo (MP2RAGE) sequence acquired at 7T has been investigated in this\nstudy.\n Methods: 8 healthy volunteers and 5 pediatric-onset multiple sclerosis\npatients were recruited at the Children's Hospital of Philadelphia and scanned\nat Siemens 7T with WMn-MPRAGE and multi-echo MP2RAGE (ME-MP2RAGE) sequences.\nWhite-matter-nulled contrast was synthesized (MP2-SYN) from T1 maps from\nME-MP2RAGE sequence. Thalamic nuclei were segmented using THOMAS joint label\nfusion algorithm from WMn-MPRAGE and MP2-SYN datasets. THOMAS pipeline was\nmodified to use majority voting to segment the bias corrected MP2-UNI images.\nThalamic nuclei from MP2-SYN and MP2-UNI images were evaluated against\ncorresponding nuclei obtained from WMn-MPRAGE images using dice coefficients,\nvolume similarity indices (VSI) and distance between centroids.\n Results: For MP2-SYN, dice > 0.85 and VSI > 0.95 was achieved for the 5\nlarger nuclei and dice > 0.6 and VSI > 0.7 was achieved for the 7 smaller\nnuclei. The dice and VSI were slightly higher whilst the distance between\ncentroids were smaller for MP2-SYN compared to MP2-UNI, indicating improved\nperformance using the synthesized WMn image.\n Discussion: THOMAS algorithm can successfully segment thalamic nuclei in\nroutinely acquired bias-free MP2RAGE images with essentially equivalent quality\nwhen evaluated against WMn-MPRAGE, hence has wider applicability in studies\nfocused on thalamic involvement in aging and disease.\n