CT Flashcards
CT scans
CT number will vary according to density of tissue scanned and is a measure of how much of the x-ray beam is absorbed by the tissues at each point in the scan
Air hounsfield number
-1000 HU
Water hounsfield number
zero
Fat hounsfield number
-40 to -100
Soft tissue hounsfield number
20 to 100 hu
Bone Hounsfield number
400 to 600 H
Metal Hounsfield number
>1000 HU
Denser sustances
absorb more x-rays, less dense sunstances absorb fewer x-rays
CT scans post porcessing
CT scans can be windowed to optimize visibility if differnet types of pathology after they are attained
What disease states can you use a CT to evaluate?
Tumors
Trauma
Infections
Bleeding
CT Scan represent
a moment in time are structural not functional
Floroscopy only dymanic one
What are the limitations of CTs
- Size of patients- app 500lb max weight
- claustrophobia
- paitents that cannot hold still for extended period of time
- patient needs to hold breath for extended period
- use water-soluble oral contrast if perforation suspected aspiration concern
What kinds of contrast are there? what is it important? what are the risks?
Types- IV, enertic (oral or rectal) constrast administration
Important- Omitting constrast when it is inidcated, or giving when not, can lead to diagnostic/ treatment errors
Risk- ADR, contrast- induced nephropathy
IV contrast is
iodine based
Classification of IV constrast
High-osmoloarity contrast (not commonly used)
Low-osmolality contrast media (Most common)
Iso-somolality contrast media
Importance of timing and contrast
Timing matters becasue the dye must enter the portion of the body you want to see
ex. barium dye swallowe must wait two hours for the dye to enter the intestines and then take pics
