FIG 1. A and B, Registered and normalized ^99mTc-HMPAO images at the two injection rates in two different patients (A and B) in coronal (top) and axial (bottom) planes. For each patient, the images on the left are after a rapid bolus injection and those on the right are after slow continuous injection. There is no visible difference between the two rates of injection, with the exception of minimal cross-flow to the contralateral frontal area on the bolus injection images in the second patient (B).