Fig 1.
A typical CT perfusion summary map and blood volume map.
An example of a thick slice (5 mm) CTP summary map (left) for acute stroke assessment of a patient with an occluded left middle cerebral artery. The red area indicates the infarct core and the green area indicates the penumbra (tissue at risk). The right parameter map shows the cerebral blood volume (CBV). Both maps were generated by the Philips EBW 4.0 Brain Perfusion software (Philips Healthcare, Best, The Netherlands). The thresholds for the infarct core and penumbra were respectively CBV < 2.0 mL/100g and MTT > 145% of the contralateral side, as suggested by Wintermark et al. [11].
Fig 2.
A raw CT perfusion scan at different slice thicknesses.
An example of a raw, sagittal reformatted CT perfusion slice at axial slice thicknesses of 0.8, 2.4, 4.8, and 9.6 mm.
Table 1.
Slice thicknesses and filter types.
Table 2.
Filter settings.
Fig 3.
Arterial input functions and venous output functions.
The mean arterial input function (AIF, left) and venous output function (VOF, right) at different slice thicknesses. Scheme 2 (see Table 1) was used for processing this data. Before averaging all AIFs and all VOFs were aligned to their time-to-peak. The areas under the curves are listed in Table 3.
Table 3.
Properties of the AIF and VOF curves.
Fig 4.
Thin and thick slice perfusion maps.
An example of axial and sagittal reformatted non-contrast CT (NCCT) slices and perfusion maps with an axial slice thickness of 0.8 mm (top row) and 4.8 mm (bottom row). Scheme 2 (bilateral filtering, see Table 1) was used for processing this data. The slice positions are indicated by a dashed line in the NCCT images. The cerebral blood volume (CBV) map shows a right posterior infarct core (low blood volume), whereas the cerebral blood flow (CBF) and mean transit time (MTT) maps clearly show the surrounding penumbra (low blood flow and elevated transit time). An elevated permeability-surface area product (PS) suggests increased vascular permeability. The 4.8 mm axial slices show slightly elevated CBF and CBV values, and decreased MTT values. The 4.8 mm sagittal slices have a pixelated appearance due to the anisotropic voxels. The raw sagittal slices are shown in Fig 2.
Fig 5.
Absolute perfusion values in the ipsilateral and contralateral hemispheres.
Box plots showing the absolute perfusion values that were measured in the tissue within the ipsilateral hemisphere (red) and in the contralateral hemisphere (green). Outliers, marked by circles, are defined as points that are more than 1.5× the interquartile range above the 75% quartile or below the 25% quartile.
Table 4.
Mean and variation in absolute perfusion parameters.
Table 5.
Mean and variation in relative perfusion parameters.