16. Introduction to Anatomical Imaging Flashcards
What color would the contrast agent be in a normal X-Ray with contrast?
What color would it be in a negative image / subtraction technology?
White
Black
What is the correct orientation for a cardiac (thorax) Xray?
Why?
PA (Posterior to Anterior)
Because AP makes the heart look enlarged, since it is closer to the tungsten target
How many frames per second would you use for fluoroscopy of the peripheral vasculature?
What about for coronary artery studies?
Two to Three FPS
15 to 30 FPS
What is digital subtraction angiography?
A fluoroscopy method by which an image is taken, contrast is introduced, and then another image is taken and compared with the first. Everything that doesn’t show the contrast is removed from the display for better imaging.
What is the downside of digital subtraction angiography?
You have to inject the contrast directly into an artery, which can cause a pulsatory bleed
What is computed tomography?
Helical Xrays are reconstructed into an axial (transverse) view of a body section
Which direction are you looking when reading a CT?
From the feet up
What is the correct Hounsfield Scale window level and width for
Lung Tissue
Level: -550
Width: 1600
Remember that air is -1000, so it makes sense that lung is really low, and since we’re starting so low, we need a wide window.
What is the correct Hounsfield Scale window level and width for
Soft Tissue
Level: 70
Width: 450
What is the correct Hounsfield Scale window level and width for
Bone
Level: 500 ish
Width: 1000-3000 ish
Really high and really wide, since bone varies greatly in density, and is obviously very dense.
What is cheaper, CT or MRI?
MRI costs roughly double
What must you do before you order a CT with contrast?
Check renal function!
Would you have to have your patient hold still more for an MRI or a CT?
MRI
CT’s are more resistant to motion
Which image can be manipulated post hoc; MRI or CT?
CT
MRI has to be set beforehand, CT has adjustable grey scale using the Hounsfield scale
Is fluid light or dark in T1 MRI?
Dark