Correlation of Putative Iron Content as Represented by Changes in R2* and Phase With Age in Deep Gray Matter of Healthy Adults

Purpose: To establish a correlation between putative iron content using susceptibility weighted imaging (SWI) phase and T2* weighted magnitude values in the basal ganglia and the thalamus as a function of age in healthy human brains. Materials and Methods: One hundred healthy adults (range, 20-69 years; mean, 43 years) were evaluated for this study using a gradient echo sequence. The original magnitude and high pass filtered phase data were analyzed as proxy variables for iron content in the substantia nigra, red nucleus, globus pallidus, putamen, caudate nucleus, thalamus, and pulvinar thalamus. Each structure was broken into two parts, a high iron content region and a low iron content region. Results: Both magnitude and phase data showed an increase in putative iron content with age. However, the high iron content region revealed two new pieces of information: both the average iron content per pixel and the area of high iron increased with age. Furthermore, significant increase in iron uptake as a function of age was found past the age of 40. Conclusion: A two region of interest analysis of iron is a much more sensitive means to evaluate iron content change over time. Contrary to the current belief that iron content increases level off with age, the putative iron deposition in the high iron content region is seen to increase with age.