Patent ID: 8467587

Claim:
A method for determining a region of gray matter in a brain starting from a time-dependent computed tomography image data record from a perfusion CT examination, the method comprising: defining a work region in the time-dependent computed tomography image data record which only comprises healthy gray matter, healthy white matter and ischemic gray matter; calculating a plurality of three-dimensional time-independent images from the time-dependent computed tomography image data record, the plurality of three-dimensional time-independent images including an average image with and without a contrast agent being present, a maximum value image over time and a baseline image without a contrast agent being present; determining a normalized difference image from the image data of a difference image, the difference image being determined from the average image and the maximum value image; generating a high-contrast image with increased contrast between white matter and gray matter from the average image, the maximum value image and the normalized difference image; determining a first grayscale value range, which only comprises gray matter, and a second grayscale value range, which only comprises white matter, by threshold histogram analysis of the high-contrast image, wherein only the image data of an undamaged hemisphere of the brain is considered; determining a third grayscale value range which comprises both the healthy white matter and the ischemic gray matter by threshold histogram analysis of the normalized difference image; determining a fourth grayscale value range which comprises both the healthy gray matter and the ischemic gray matter by threshold histogram analysis of the baseline image; generating a fifth grayscale value range which lies in the damaged hemisphere and only comprises the ischemic gray matter by a logical combination of the third grayscale value range and the fourth grayscale value range; determining seed points for respectively the first grayscale value range, the second grayscale value range and the fifth grayscale value range; performing a region growing method respectively starting at the previously determined seed points and generating a first image region, a second image region, and a fifth image region; generating an expanded first image region by adding cerebral regions which constitute anatomically assured gray matter to the first image region; and determining a resultant image region which comprises both the healthy gray matter and the ischemic gray matter and all regions of the brain which have not yet been acquired by way of a logical combination of the changed first image region, the second image region and the fifth image region.