1992; Cherubini et al. 2009; Long et al. 2012). Furthermore, as we find a reduction of vascular signal in striatal gray matter but no EGFR inhibitor drugs significant difference in total volume,

this may also support earlier considerations on a prominent role of vascular pathology in the process of aging-related changes of striatal gray matter (Mori 2002; Roman et al. 2002; Kling et al. 2013), observable on a single subject level. To our knowledge, this is the first study to use magnetic resonance imaging (MRI)-angiography for assessment of Inhibitors,research,lifescience,medical aging-related subcortical gray-matter vascularization and also the first to use TOF-MRI at 7T in combination with an automated parcellation algorithm to assess quantifiable indicators of subcortical vascular integrity. TOF-MRI is routinely used for assessment of cerebral vascular pathology and related subcortical gray-matter integrity. Using higher field strength in MRI applications is associated with significantly increased Inhibitors,research,lifescience,medical Signal to noise ratio (SNR) (Pruessmann 2004; Lu et al. 2005) and performing MRI-TOF angiography at 7T has been demonstrated to make possible the high spatial resolutions necessary for the assessment of small subcortical vessels, which have been shown to be particularly

vulnerable in the process of aging (Cho et al. 2008; Hendrikse et al. 2008; Madai Inhibitors,research,lifescience,medical et al. 2012). It has to be taken into account, however, that regional inhomogeneities due to the high fieldstrength at 7T may result in inconsistencies of the effective flip-angel in TOF-MRI (Pruessmann 2004).

To minimize this issue, maximum intensity projection was focused Inhibitors,research,lifescience,medical on the subcortical region of interest. Taken together, our study demonstrates interindividual Inhibitors,research,lifescience,medical differences in subcortical vascularization that possibly reflect aging-related vulnerability of gray-matter nuclei for vascular pathology (Murphy et al. 1992; Cherubini et al. 2009; Long et al. 2012). While we find most prominent changes for the thalamic region, our data may reflect reduced vascular activity as a proxy of reduced gray-matter viability (Kling et al. 2013). Moreover, our data demonstrate the applicability of TOF angiography together with the FreeSurfer subcortical parcellation algorithm on the single unless subject level, resulting in a quantifiable measure of regional subcortical vascularization. Additional studies are needed to validate this approach and to determine applicability as an outcome marker in therapeutic trials focussed on vascular integrity in the context of aging-related neuropsychiatric disorder. Acknowledgments We thank both study volunteers for their participation. We thank Esmeralda Gruber of the Division of Psychiatry Research and Psychogeriatric Medicine, University of Zürich, for technical assistance.