Radiology 2 Flashcards
What is fluoroscopy?
real-time moving radiographic images
What is a c-arm?
portable fluoroscopy
What does a ct scan create?
Cross sectional imaging, using computer data can create 3-d images
CT Scan problem
- increased radiation exposure
- more expensive than radiographs
- poor soft tissue contrast
CT pros
detailed view of anatomy without superimposition
faster and less expensive than MRI
best for bone, lung, abdomen
Types of CT scans
single splice (slow old)
Spiral (fast, new)
Multi-detector (fast, new, better)
pixel vs voxel
radiograph creates pixel (2-D)
Ct creates voxel (3-D, has slice thickness)
- thinner slices are better (isotopic =cube= great)
hounsfield U
there are more than 4,000 HU
(human eye can see 20 shades of gray)
Use WINDOWS and LEVEL to see image better
What is window and level?
Window= selected range of HU (can see tissues better at a certain range) Level = central value of HU displayed
Word used to describe CT scans color?
attenuation
Word to describe radiograph color?
opacity
Hyperattenuating color
Highest HU value (bone, metal)
WHITE COLOR
Hypoattenuating color
lowest HU value (air)
BLACK
MRI principles
Needed: Magnet, computer, hydrogen protons
odd number of protons( like abundant hydrogen)
act like a tiny magnet - as tissues relax at different rates an image is formed (simplified)
what is weighting?
using parameters to optimize the differences in relaxation rates of different tissues in order to provide contrast in the image
Most important weights
T1, T2
Qualities of T1 weighted images
Fluid is black
Fat is white
(bone is also black, and muscle/tissue is gray)
word to describe MRI
intense
hypointense
MRI- less bright (black)
hyperintense
MRI- brighter than (white)
isointense
MRI- same brightness
Pros of MRI
better soft tissue contrast and detail
noninvasive
no radiation!
cons of MRI
long scan times (anesthesia)
cost! (most expensive)
projectiles (magnet is ALWAYS on)
Ultrasound principles
- high sound wave frequency
- transmits sound waves, and MEASURES the intensity/time of returning waves
low US frequency transducers
penetrate farther, but have lower resolution
high US frequency transducers
do not penetrate far, but have high resolution
word to describe US
echoic
Anechoic color?
Black
urine/bile
Hypoechoic color?
Dark gray (darker than…)
Isoechoic color?
same echogenicity (color)
Hyperechoic color
White (brighter than…)
bone, gas, organ boundaries
Doppler Effect in US (what it needs, colors, etc.)
Allows for determination of velocity and direction of blood flow (needs constant motion and direction like blood flow)
Blue= away
Red= towards
(car physics example)
