| Summary: | Alterations in cerebral perfusion and metabolism in Parkinson's disease have been assessed in several studies,
using nuclear imaging techniques and more recently magnetic resonance imaging. However, to date there is
no consensus in the literature regarding the extent and the magnitude of these alterations. In this work, arterial
spin labeled perfusion MRI was employed to quantify absolute cerebral blood flow in a group of earlyto-
moderate Parkinson's disease patients and age-matched healthy controls. Perfusion comparisons between
the two groups showed that Parkinson's disease is characterized by wide-spread cortical hypoperfusion. Subcortically,
hypoperfusion was also found in the caudate nucleus. This pattern of hypoperfusion could be related
to cognitive dysfunctions that have been previously observed even at the disease early stages. The present
results were obtained by means of whole brain voxel-wise comparisons of absolute perfusion values, using
statistical parametric mapping, thus avoiding the potentially biased global mean normalization procedure.
In addition, this work demonstrates that between-group comparison of relative perfusion values after global
mean normalization, introduced artifactual relative perfusion increases, where absolute perfusion was in fact
preserved. This has implications for perfusion studies of other brain disorders.
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