Introduction

While the earliest uses of MR perfusion imaging were primarily in oncological and neurovascular imaging, increasingly MR perfusion has shown its utility both in research and clinical practice in a large range of both normal physiological states and pathological conditions. MR perfusion improves disease characterization, and with the growing number of entities studied, it becomes useful and at times necessary to categorize perfusion patterns. Changes in brain perfusion parameters can loosely be grouped into either global or focal, and either hypo- or hyperperfusion (Table 10.1). Though it is useful to employ such a categorization scheme, several of the more common disease states can demonstrate both hypo- and hyperperfusion patterns, which can be seen synchronously or vary temporally (reflective of the underlying pathophysiology). This chapter will describe the typical perfusion patterns in the more commonly encountered physiological states and pathological conditions, primarily with an emphasis on the use of arterial spin labeling (ASL) techniques. Oncological and stroke imaging will only be discussed for completeness where appropriate, but are otherwise detailed in dedicated chapters (Chapters 11 and 8, respectively).