CT Protocols: (Brain, ENT, Spine, Vascular) - Department of Radiology

135 Revised 7/22/09 (Gentry/Ranallo)
GE Advantage: CT Perfusion Post Processing Protocol
a. Select Perfusion series from patient list
b. From Applications menu at right of screen choose CT PerfusionN (exam will load)
c. From list of protocols choose Brain Tumor
d. Using slide bar at bottom of upper left port, slide back and forth to look for motion. If there
is motion click apply registration, then click next. If not, click next.
e. Now you will see a box called Processing Thresholds. Your object here is to get all little
boxes/pixels out of the brain tissue and include as much brain parenchyma as you can.
Your slide bar that you used to check for motion must be all the way to the left and rank
should be 1/89. Slide air bar to left to remove boxes/pixels from ventricles and there are
any diagonal lines with pieces missing, this air bar may fill them in. This is a very slight
movement. Your average range should be (-27 to around -63). It can go higher and that is
ok but usually doesn’t
f. Slide bone bar to right to bring circle out to edge of bone only. This is easiest when using a
bone window. Middle mouse will change window/level. Click next.
g. Using slide bar in upper left port again, move it left to right to find a slice where contrast is
fairly bright. Look on upper slices for anterior cerebrals, just above frontal horns.
This is the best place to look for an artery.
You can move up levels by right-clicking
on your image location in your upper left port. Click on ROI to the left of your screen
and place over an artery. Click next. This should result in a small purple circle being
placed in an artery with a label and arrow.
h. Now do the same for a vein. A good place to look is down in the sinus. Click next. If you
have gone up several levels to find your vein/artery, make sure you go back to the
beginning to place your ROIs! The vein and artery do not have to be on the same slice!
i. Roam your image over to the right. Do this by grabbing the “ P” on the bottom of your
upper left port (you will see a hand) and moving your head.
j. Now place your cursor in the upper right port and hit the space bar. This will bring up a
graph with 2 lines (1) and (2). 1 is the artery you marked and 2 is the vein. On the line that
says “Last pre-enhancement image” grab the number and a white line will appear in your
graph. You want to move the line to the last spot before the contrast spikes. You do this on
line 1 only. (If you are having trouble seeing the 2 lines separately, click on the word artery
in your upper left port. This will activate it and turn it green and you will be able to
distinguish the two lines. When you are done click in the upper left port to de-activate the
artery so it returns to purple.) Click next.
k. Click compute. This will take a minute. Close Final Settings box.
l. In the lower left port there will be a drop down menu under DFOV called Blood Flow.
Change this view to Mean Transit Time.
m. Click on Film/Save box and choose ROIs/Templates. Click on Neuro template for upper
levels and Neuro-lower for lower levels (the only difference between these two is that
Neuro-lower only has 2 ROIs to place instead of four. Hit Load. This will bring up your
ROIs and Axis line. You may need to adjust their placement depending on your centering.
You can now close this box.
n. Look for any obvious perfusion abnormality. This is where you will place your ROI. If there
isn’t any obvious abnormality then you will place your ROIs in the standard places.