Presence of thymic tissue on MRI scans of patients thymectomized during infancy. Summary of MRI scans of 32 patients (study group, 8 patients; additional group, 24 patients) after surgery for a congenital heart defect. ○ represents MRI scans with no evidence of thymic tissue. represents scans with evidence of thymic tissue, but small for the age of the individual. ● represents MRI scans with evidence of thymic tissue of similar size as healthy age-matched controls. Lines connect consecutive scans of the same patient (n = 7). Only 42 of the 48 MRI scans that were made are plotted in this figure; once an MRI scan of a patient showed thymic tissue of normal size for the age of the individual, any follow-up MRI scans (which consistently reconfirmed the normalization of thymic tissue) were not plotted in this figure.