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. IRON HAS LONG been recognized to play a key role in brain function such as in oxygen transport, neurotransmitter synthesis, electron transfer, and myelin production (1,2). Despite the positive implications of iron, in its free ferrous form, iron is known to be toxic and lead to free radical production. Recently, there has been a renewed interest in the role of iron in the pathogenesis of many diseases such as aging, multiple sclerosis, Parkinson's disease, and other diseases (1-5). The disturbance of iron metabolism can occur at several levels: iron uptake and release, storage, intracellular metabolism, and regulation. The body has several ways to deal with this issue by storing excess iron in the form of ferritin or hemosiderin. Ferritin appears to be the normal form of iron storage, whereas hemosiderin often appears when there has been bleeding and macrophages have helped to consolidate this iron (5-7). Using methods such as diaminobenzidine acid enhanced Perl's staining revealed iron in many cell types of the central nervous system such as neurons, microglia, oligodendroglia, astrocytes, and in some myelin sheaths (8). This iron is also found to be present in higher concentration in gray matter than white matter (9). Deep gray matter structures accumulate ferritin at different rates throughout different ages (8,(10)(11)(12). It is believed and often quoted (10) that iron increases quickly with age and then levels off or increases more slowly. Furthermore, it has been shown that there are major iron deposits in the form of ferritin associated with the basal ganglia (13,14). This interest in iron has led to attempts to quantify iron using imaging in neurodegenerative diseases to un...

Susceptibility weighted imaging (SWI) is a method that uses the intrinsic nature of local magnetic fields to enhance image contrast in order to improve the visibility of various susceptibility sources and to facilitate the diagnostic interpretation. It is also the precursor to the concept of using phase for quantitative susceptibility mapping (QSM). Nowadays, SWI has become a widely used clinical tool to image deoxyhemoglobin in veins, iron deposition in the brain, hemorrhages, microbleeds, and calcification. In this paper, we review the basics of SWI, including data acquisition, data reconstruction and post-processing. In particular, the source of cusp artifacts in phase images is investigated in detail and an improved multi-channel phase data combination algorithm is provided. In addition, we show a few clinical applications of SWI for imaging stroke, traumatic brain injury, carotid vessel wall, siderotic nodules in cirrhotic liver, prostate cancer, prostatic calcification, spinal cord injury and intervertebral disc degeneration. As the clinical applications of SWI continue to expand both in and outside the brain, improving SWI in conjunction with QSM is an important future direction of this technology.

We conclude that the age-susceptibility correlation can serve as a quantitative magnetic susceptibility baseline as a function of age for monitoring abnormal global and regional iron deposition. A regional analysis has shown a tighter age related behavior, providing a reliable and sensitive reference for what can be considered normal iron content for studies of neurodegenerative diseases. J. Magn. Reson. Imaging 2016;44:59-71.

BACKGROUND AND PURPOSE The mesencephalon is involved in a number of human neurodegenerative disorders and has been typically imaged with T1-, T2- and T2*-weighted methods. Our aim was to collect high-contrast susceptibility-weighted imaging (SWI) data to differentiate among and within the basic mesencephalic structures: namely, the red nucleus, substantia nigra, and crus cerebri. MATERIALS AND METHODS High-resolution SWI, 3D T1-weighted, and T2-weighted data were collected to study contrast in the mesencephalon at 1.5T and 4T. Contrast between structures was calculated for SWI high-pass (HP)-filtered-phase, T1 gradient-echo, and spin-echo T2-weighted data. RESULTS SWI HP-filtered-phase data revealed similar contrast for the red nucleus and substantia nigra when compared with T2-weighted imaging. However, SWI was able to show structures within the red nucleus, substantia nigra, and medial geniculate body that were invisible on T2-weighted imaging. T1-weighted imaging, on the other hand, did not reveal measurable contrast for any of the structures of interest. SWI HP-filtered-phase data at 4T agreed well with india ink – stained cadaver brain studies, which appear to correlate with capillary density. CONCLUSIONS With SWI, it is possible to create better anatomic images of the mesencephalon, with improved contrast compared with conventional T1- or T2-weighted sequences.

BACKGROUND AND PURPOSE:It is well known that patients with MS tend to have abnormal iron deposition in and around the MS plaques, in the basal ganglia and the THA. In this study, we used SWI to quantify iron content in patients with MS and healthy volunteers.