Radiology Grad Class Flashcards
What is the difference between a pixel and a voxel?
A pixel is a 2D structure; a voxel incorporates a third dimension (the slice thickness of that tissue).
What is the approximate window level for air?
-1000
What is the approximate window level for fat?
-100
What is the approximate window level for soft tissue [brain]?
+30-40
What is the approximate window level for bone?
500-1000
What is pitch?
The distance of table movement per rotation
What does changing the pitch from 1 to >1 do to image quality? What about
1 - normal
>1 - worse quality (gaps)
What is the relationship between photoelectric effect and atomic number?
PE effect is related to the cube of the atomic number
What are three contraindications for IV use of an iodinated contrast agent?
Dehydration/hypovolemia
Renal failure (ARF or CRF)
Disruption of BBB
In very general terms, what do T1 and T2 refer to regarding electron behavior?
T1 is how long the electrons take to come back up. T2 is related to their spin.
What is the safest position if performing a negative contrast (air) cystogram? Why?
Left lateral recumbency. If air embolizes it will get trapped in uppermost part of right ventricle and is less likely to go to lungs.
What is the normal diameter (relative to another anatomic structure) of the small intestine in dogs? Cats?
What is definitive for ileus in dog?
Dogs - no more than 2x width of rib
Cats - no more than 2x height of central L4
Dog ileus - 4x width of rib
What is the barium dose for a GI series?
5-6 ml/lb
On the “mushroom” view on echo, what is normal L ventricle size relative to R ventricle?
L should be 3x the size of R
What is normal fractional shortening for
- small breed dogs?
- large breed dogs?
- cats?
small breed: 35-45%
large breed: >25%
cat: 45-55%
What is the normal ratio of aorta to left atrium in dogs?
1 : 1.3
What is the normal left atrium diameter in cats?
less than or equal to 1.5 cm
What is the limitation of pulsed-wave doppler for echocardiogram?
It can’t measure high velocities
What is the normal thickness for septum and left ventric free wall in systole for cats?
less than or equal to 0.6 cm
On echo, what is the diagnostic view for diagnosis of PDA?
RVOT
What is particulate radiation?
Beta articles/electrons
What is electromagnetic radiation?
X rays and gamma rays
What is the definition of a Gy?
100 J/kg
Give 3 examples of teletherapy?
Orthovoltage, Cobalt, Linac