Abstract
We present a unified P-value for assessing the significance of peaks in statistical fields searched over regions of any shape or size. We extend this to 4-D scale space searches over smoothing filter width as well as location. The results are usable in a wide range of applications, including PET and fMRI, but are discussed with particular reference to PET images which represent changes in cerebral blood flow (CBF) elicited by a specific cognitive or sensorimotor task.