Operating instructions

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Perfusion CT
3. What do pixel values mean in the Perfusion CT
images?
It is very important to realize that pixel values now
have a different meaning, which depends on the type
of image currently displayed. So if you point the cursor
into a parameter image bear in mind that you do not
read a CT-value but a functional unit. A time-to-peak
image, for example, displays numbers proportional to
the time until the bolus peak is reached; so higher
numbers mean later bolus arrival.
A CBF image, on the other hand, displays numbers
proportional to blood flow; so smaller numbers indicate
lower flow.
4. Filming color images
If a color hardcopy device is connected to the system,
color images can be printed via the filming task card.
It is recommended to send the color images from the
Viewing task card after having saved them on the Per-
fusion task card.
5. How to fine-tune the color mapping?
– For “flow images” (CBF and CBV) – the color palette
for the flow image is designed such, that after optimal
adjustment with the arrow buttons the following
approximate correspondence will result for a normal
brain:
red _ vessels
green/yellow _ gray matter
blue _ white matter
black _ no calculation (CSF space)