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Radiographs
Week 1 Radiograph Lectures
33
Veterinary Medicine
Graduate
07/06/2015

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Term
ICRP
Definition
International Commission on Radiological Protection
each country interprets (UK VERY STRICT)
Term
Types of imaging
Definition
radiographs
CT (computed tomography)
Fluoroscopy
Scintigraphy
Term
Grays (unit)
Definition
Gy: absorbed dose (what causes ill effects)
defined as the absorption of one joule of radiation energy per one kilogram of matter.
Term
Sieverts (unit)
Definition
SV: quality factor
one sievert is generally defined as the amount of radiation roughly equivalent in biological effectiveness to one gray (or 100 rads) of gamma radiation
Term
Amount of Gy and Sv in radiation
Definition
x-Rays: 1 Gy, 1 Sv
Beta: 1 Gy, 1 Sv
Neutrons: 1 Gy, 10 Sv
Alpha: 1 Gy, 20 Sv
Term
Exposure Levels
Definition
Lateral Throacic Rad: 0.2 Gy
Atom Bomb: 4.5 Gy
Term
Stochastic vs. Non-Stochastic
Definition
by chance vs. dose dependent effects
Term
Somatic effects
Definition
"general effects"
cataracts, skin burns, scarring, carcinogenic
Term
Mutagenic effects
Definition
"biological effects"
effects on descendants of exposed individuals due to mutation of genetic material
Term
X-rays
Definition
emitted by electrons, longer wavelengths, lower frequencies, and lower energy than GAMMA rays
Term
Gamma rays
Definition
emitted from NUCLEUS, shorter wavelengths, higher frequencies, higher energy
Term
Prodution of X-Rays
Definition
Cathode: high speed electrons in vacuum
Anode: abruptly stopped, x-rays emmited
transformers: needed to make voltage
Term
Metal of Anode
Definition
needs to have high melting point.
high atomic # defined as Z
TUNGSTEN
Term
kV
Definition
kilovolts
potential difference between anode and cathode
controlled by radiographer
POWER/PENETRATION
changes quality
Term
mA
Definition
milliamperes
# of electrons passing from cathode to anode (current)
leads to # of rays emitted
controlledby radiographer
changes quality
Term
s
Definition
seconds
time of exposure
controlled by radiographer
Term
mAs
Definition
milliamperes/second
# of rays/time
governs amount of rays reaching the film
Term
Interaction of rays and subject
Definition
Transmission: passes through
Attenuation: gradual loss of intensity while passing through
Term
Attenuation Effects
Definition
Photoelectric effect (absorption based on Z of subject)
Compton Effect (scattering based on density of subject and kV of rays)
Term
Effect of Attenuation
Definition
air: black - most passes through
fat: dark grey
soft tissue: soft grey
bone: white
lead: bright white - least passes through
Term
Scatter control
Definition
scatter goes in all direction
decreases with distance (inverse square law)
Grids (stationary, parallel, focussed, Potter-Bucky)
CAN CAUSE NON-SPECIFIC GREYING OF FILM
Term
Detection of Photons
Definition
FILM not sensitive to x-rays. need INTENSIFYING SCREENS (give off light when hit by x-ray)
DIGITAL done by computed or direct counts
Term
Operator protection
Definition
control area within 2m of tube
if manual restraint necessary: gloves, gowns, thyroid shield, glasses, and film badge
room: 1mm lead shielding or equivalent
Term
Density of Radiograph
Definition
(visibility of details)
controlled by mAs
mAs too low (underexposure) results in a pale film
mAs too high (overexposure) results in a dark film
Term
Contrast of Radiograph
Definition
(difference in blackness)
kV: low kV gives high contrast
mAs: low mAs gives low contrast
Term
Under-exposure
Definition
kV too low (not enough power to get to plate)
mAs too low (not enough rays/time to get to plate)
Term
Over-exposure
Definition
kV too high (too much power)
Term
Penumbra
Definition
blurring at the edge of an object on film (due to rays not all being from same point)
OFD (object to film distance) decrease
FFD (focus to film distance) increase
Term
Nomeclature of radiographs
Definition
DIRECTION where beam ENTERS and EXITS
VD 20 degrees RCd: beam goes ventral to dorsal offset by 20 degrees rostral to caudal
Term
Orthogonal views
Definition
Lat, VD, DV for thorax, abd, skull
Lat, CrCd - limbs
Term
Oblique views
Definition
FML
used in equine rads
DLPMO - dorsal lateral to palmar/plantar medial oblique
DMPLO - dorsal medial to palmar/plantar lateral oblique
Term
Hock oblique view
Definition
tibia-tarsal bones
Spavin (DJD)
Term
Fetlock oblique views
Definition
meta carpo/tasro - phalangeal joints
Chips
DJD
Sesamoiditis
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