Serial changes in regional blood flow in the cerebrum and cerebellum of stroke patients imaged by 99Tcm-HMPAO SPET. 
Luxury perfusion is a well-known phenomenon that can mask ischaemic lesions in patients with cerebral infarction, thus making diagnosis difficult.  In this study, we evaluated the incidence of luxury perfusion over a 3-week period following a stroke episode.  The usefulness of crossed cerebellar diaschisis (CCD) as a complementary feature in the diagnosis of cerebral infarction was also evaluated using 99Tcm-hexamethylpropyleneamine oxime (99TcmHMPAO) brain single photon emission tomography (SPET).  Twelve patients diagnosed as having a hemispheric ischaemic stroke of the middle cerebral arterial territory were enrolled in the study.  Each patient underwent a total of four 99Tcm-HMPAO brain SPET examinations, 1 day, 1 week, 2 weeks and 3 weeks following the stroke episode.  Our results show that the incidence of luxury perfusion was 67% (8/12) after 1 week, 75% (9/12) after 2 weeks and 83% (10/12) after 3 weeks.  The incidence of CCD was 33% (4/12) after 1 day, 50% (6/12) after 1 week, 42% (5/12) after 2 weeks and 33% (4/12) after 3 weeks.  We conclude that the detection of cerebral infarction is difficult 2 weeks or more after a stroke episode.  The interval between the stroke episode and examination must be considered when reading the 99Tcm-HMPAO image.  In addition, CCD may be helpful for the diagnosis of cerebral infarction within the first week after a stroke episode, especially in cases of an unidentified ischaemic region on the 99Tcm-HMPAO hemispheric image.  However, the value of CCD is limited 2 weeks or more following the stroke episode.