Left MCA ischaemic stroke (stroke window setting)
75 year old male brought in by ambulance after wife noticed he had trouble getting out of bed in the morning. The patient has right arm/leg paralysis, a right facial droop and fecal incontinence.
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Non-contrast CT head (stroke window level 32 HU/ width 8 HU) shows obscuration of the left caudate and lentiform nucleus. There is loss of gray-white matter differentiation in the posterior portion of the left insula cortex and the left superior temporal gyrus. Dense vessel sign is present in the M1 and M2 segments of the left middle cerebral artery. The left fronto-parietal cortex maintain normal gray-white differentiation at this stage. No intraparenchymal haemorrhage.
Stroke window setting is used to optimized visual depiction of subtle loss of gray-white matter differentiation. Window level of 32 Hounsfield unit (HU) and width of 8 HU has been shown to improved sensitivity in detection of acute ischaemic stroke on CT. The sensitivity is increased from 57% to 71% compared to normal window setting (level of 20 HU and window width of 80 HU) .1
- Lev MH, Farkas J, Gemmete JJ, Hossain ST, Hunter GJ, Koroshetz WJ, Gonzalez RG. Acute stroke: improved nonenhanced CT detection--benefits of soft-copy interpretation by using variable window width and center level settings.Radiology. 1999;213(1):150-5.