Chapter 9
Concepts you already
know!!!
INTENSITY = ROENTGENS
AKA EXPOSURE
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mAs and mR
proportional?
kVp and mR
proportional?
Distance and mR proportional?
How do you “harden” the beam
“The disadvantage of x-ray
beam filtration is reduced image
contrast owing to beam
hardening.” Why?
HALF VALUE LAYER
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What is penetrability?
HIGH QUALITY VS LOW
QUALITY X-RAYS
HVL See last green box on pg
155
FILTRATION
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Inherent
Added
• What affect does added filtration
have to HVL?
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Compensating
Chapter 10
Interaction with Matter
X-RAYS
AND
INTERACTION
WITH
MATTER
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Low energy
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Medium energy
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High energy
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interact with
whole atom
interact with
electrons
interact with
nuclei
Low energy
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Classical or
coherent or
Thomson,
Rayleigh
interacts with
target atom
excites it
DOES NOT
IONIZE IT
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NO ENERGY
TRANSFER
change of
direction
(scatter) but no
ionization
little
significance in
diagnostic x-ray
Medium energy
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Photoelectric
effect
lower KvP
(atomic #)
inner shell
electrons
x-ray totally
absorbed
secondary/
characteristic
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brightness
(white) on film
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Medium energy
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Compton Effect
Increases with
higher energy
interacts with
outer shell electron
IONIZES ATOM
energy divided
between scattered
x-ray &compton
electron
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Scattered x-ray
can go many
directions
not useful
happens with all
exams
backscatter
High energy
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Pair production-interaction near
the nuclei
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Photodisintegration-absorbed by
nucleus
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1.0 MeV and 10MeV
respectively
What does all this mean
in terms of images on
the film?
COMPTON VS
PHOTOELECTRIC EFFECT
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Compton-produces film fog
Photoelectric effect results in
no x-rays reaching the film
(radioopaque)
DIFFERENTIAL
ABSORPTION
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Difference of those x-rays
absorbed photoelectrically and
x-rays not absorbed at all.
Radiolucent
<5% reach film
<1/2 which reach film interact
1% of x-rays emitted produce
film image
WHAT IS MASS DENSITY?
Contrast examination
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Barium
Iodine
Air
Exponential attenuation
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X-ray interaction in any of the
five mechanisms already note
Which are…
Exponential attenuation (pg 185
figure 12-15