Patient with a persistent right middle cerebral artery (MCA) occlusion: 2 hours after symptom onset the FLAIR sequence is normal. The apparent diffusion coefficient (ADC) values are substantially reduced in a small region of the right hemisphere (pink on the RAPID DWI map). Perfusion is substantially delayed (> 6 seconds) in a much larger region of the right hemisphere (green on the RAPID Tmax map).

By 8 hours the early ischemic lesion is now visible on the FLAIR and the volume of the lesion with a severed reduction in ADC has grown (pink on DWI map). The degree of perfusion delay (green on Tmax map) is unchanged.

At 24 hours the full ischemic lesion is now clearly seen on both the DWI and FLAIR. Note that the ischemic lesion may increase in size for several days in patients who do not reperfuse. Therefore, a 24 hour scan may underestimate the final infarct volume.

Regions with apparent diffusion coefficient (ADC) reduced <600 are pink on DWI maps
Regions with perfusion delay >6 seconds are green on Tmax >6 s maps


Patient with a right middle cerebral artery (MCA) occlusion and early reperfusion: 2 hours after symptom onset the FLAIR sequence is normal. The apparent diffusion coefficient (ADC) values are substantially reduced in a small region of the right hemisphere (pink on the RAPID DWI map). Perfusion is substantially delayed (> 6 seconds) in a much larger region of the right hemisphere (green on the RAPID Tmax map).

Early reperfusion occurs resulting in complete resolution of the green perfusion lesion and an increase in ADC values. The ischemic lesion remains pink on the RAPID DWI map because the ADC values are still below 600. At 24 hours a small ischemic lesion is now clearly seen on both the FLAIR and the DWI in the same region as the initial DWI lesion.

Regions with apparent diffusion coefficient (ADC) reduced <600 are pink on DWI maps
Regions with perfusion delay >6 seconds are green on Tmax >6 s maps


Patient with a right middle cerebral artery (MCA) occlusion and early reperfusion: 2 hours after symptom onset the FLAIR sequence is normal. The apparent diffusion coefficient (ADC) values are substantially reduced in a small region of the right hemisphere (pink on the RAPID DWI map). Perfusion is substantially delayed (> 6 seconds) in a much larger region of the right hemisphere (green on the RAPID Tmax map).

Following reperfusion, the rise in ADC is variable. Frequently, ADC values increase to values above 600 in part or all of the ischemic lesion. This increase in ADC typically does not indicate tissue salvage. If the ADC values (blue line) rise to levels above the RAPID threshold (dotted yellow line) then the lesion will no longer be labeled in pink but typically will still be visible as a bright lesion on both the DWI and FLAIR map. Therefore, following reperfusion, the automated RAPID ADC volume frequently underestimates the volume of the ischemic lesion that is visible on the DWI or FLAIR.

Regions with apparent diffusion coefficient (ADC) reduced <600 are pink on DWI maps.
Regions with perfusion delay >6 seconds are green on Tmax >6 s maps