2 - Aldridge - Imaging Flashcards
Ionizing Radiation Methods?
Non-Ionizing Radiation Methods?
Ionizing: Radiohraphs (x-rays, conv. films), Fluoroscopy, Computed Tomography (CT)
Non-Ionizing: MRI, Ultrasound (US)
Conventional Radiographs/Plain Films
(x-ray)
No added contrast material
Energy detection by film or digital detector
Images named w/consideration to the direction of the X-ray beam
X Ray Absorbance
Based on density of tissue, very dense will not allow X-rays to pass through, white, called radiopaque / radiodense
Low density, more will pass, black image–radiolucent
Gray somewhere in between
5 Basic Densities on Radiographs
What is an issue with the dimensions for radiographs?
Radiographs are a 2D projection of a 3D patient and flatten everything, multiple views are needed
Advantages to Plain Films?
Disadvantages to Plain Films?
(+) Fast, cheap, mobile machines, most common
(-) Radiation, not good for pregnant, soft tissue not very good
Fluoroscopy
Continuous x rays pass through
Barium swallow
real time
apparatus placement in surgery
Computed Tomography (CT)
Similar to radiograph (uses ionizing radiation)
Source rotates 360 deg
multiplanar images
Computer renders final image
How do you read CT?
Patient laying down, face up, your standing at their feet looking through their body
Hounsfield Units
Measurement of CT density
Dense = higher number = white = increased attenuation
Less Dense = lower number = black = decreased attenuation
CT Windowing
Post-processing that allows manipulation of multiple layers of at once
CT Scans and Contrast
Can be performed with or without contrast
With = enhanced
Iodinated contrast used via IV, better distinguishing of structures
Iodinated contrast can have adverse effects and serious reactions in some people (kidney failure)
CT Advantages and Disadvantages
(+) Resolution excellent (small fractures), multiple planes, widely available, cheaper than MRI, fast, multiple windows
(-) High radiation, IV contrast can be bad for kidneys, much more expensive than Xray
MRI
Not use ionizing radiation, uses radio waves
Computer manipulates pulse data from electromagnetic wave radiation
Weighted MRI Images
Signal Intensity?
T1 = anatomical detail
water = dark
T2 = pathological lesions
water = bright
- -
Increased Signal Intensity = white or bright area
Decreased Signal Intensity = black or dark area
MRI Advantages and Disadvantages
(+) No radiation, multiple planes, better soft tissue than CT
(-) Not manipulated on viewing screen like CT, claustrophic/fat ppl bad, long-time, metal/implants can’t be scanned, no movement, expensive, contrast reactions
MRI Safety
Can’t be around anything:
ferromagnetic, electronic, anything not certified MRI compatible
Magnet is always on
Metal than can’t move = not an issue (fillings, orthopedic hardware)
Metal than can move = issue (metal in eyes, old aneurysm clips)
Old Pacemakers = could drain battery, dork up coding, fire erratically
Nephrogenic System Fibrosis (NSF)
Can occur if patients who are renally compromised are given gadolinium-based contrast agents
Ultrasound (US)
Uses high frequency sound waves
Dense = sonodense = bright/white
Less Dense = sonolucent = dark/black
Ultrasound Advatages and Disadvantages
(+) Noninvasive, no radiation, real-time, no discomfort, cheap, portable
(-) Bone and air-filled structures interfere, difficult w/obese patients
Radiation Exposure
Large doses can be baaad, mkay?
Shield eyes, gonads, thyroid
Avoid X-rays on pregnant people
