CT Tough Practice Questions Flashcards
What is the maximum IV contrast dose for a child?
3 mg per kg of body weight
A 1% difference in contrast between two structures is a difference in ____ HU.
10 HU
The pterygoid plate is ________ to the maxillary sinus.
posterior
What is the normal GFR for a woman? For a man?
women: 60 +/- 10 mL/min/mm^2
men: 70 +/- 14 mL/min/mm^2
If a patient has normal renal function, what is the excretion half-time for IV iodinated contrast?
1-2 hours
A tissue’s linear attenuation coefficient (LAC) is 0.31. The CT system’s LAC for water is 0.24. What CT number would be applied to a voxel representing this tissue?
292 HU
tissue LAC - water LAC / water LAC x 1000
A(n) _______ in aperture size would increase signal to noise ratio. Why?
increase. increasing aperture size (decreasing collimation) would allow more radiation to the tissue, which would reduce noise and increase the SNR.
A solid state detector emits a(n) _____ signal proportional to radiation detected.
analog
The ability of IV contrast to move from extravasculature to intravasculature is termed:
osmolality.
The technique that allows a user to select a range of pixels for a 3D CT reformation is called what?
thresholding
The liver receives 75% of its blood from what? What about the remaining 25%?
75% comes from the portal vein; 25% comes from the hepatic artery
The ability of a CT scanners’s ability to differentiate objects with similar linear attenuation coefficients is called what two terms?
contrast resolution and sensitivity
What gas is used in CT ionization chambers?
xenon
Measuring the uniformity of a CT system is checking for the negative effects of what?
beam hardening
What agent works well to visualize the GI wall after IV contrast enhancement?
water
