CT perfusion scanning produces dynamic contrast-enhanced brain images, but to generate and interpret the colour maps of cerebral perfusion from these source images requires specialist neuroimaging knowledge. We hypothesized that physicians without such training might still utilise the CT perfusion source images (CTPSI) to diagnose early ischaemic change. Fifteen patients had cerebral non-contrast CT (NCCT) and perfusion CT within 6 hours of hemispheric stroke onset. We tested 15 non-stroke clinicians and radiology trainees, plus three experts, in assessing the presence and extent of early ischaemic change on NCCT versus CTPSI. Day 5-7 CT or MRI was used as the gold standard. Agreement with follow-up imaging was poor for both detection, and extent of early ischaemic change on NCCT (kappa = 0.01-0.11). There was a marked improvement in agreement for both the presence and extent of early ischaemic change on CTPSI (kappa = 0.67-0.83). CTPSI were much more accurate than NCCT in identifying acute ischaemic change. 'Less expert' users accurately identified major early ischaemic change on acute CTPSI. These findings suggest that such physicians might utilise CTPSI to screen potential thrombolysis candidates.