Chapter 9 X-ray Interaction with Matter

wave or particle

Electromagnetic radiation interacts with matter as

wavelength

Interacts with structures similar in size to _____________

very short

X-rays have _____________ wavelengths

shorter wavelength

Higher energy =

whole atoms

electrons

nuclei

Low energy x-rays interact with ______________, moderate energy interact with ___________, high energy interact with __________

shorter the wavelength

higher the energy the

entire atom itself

Something that has low energy is going to interact with the

electrons

Moderate energy interacts with the

nucleus

High energy interacts with

-Coherent Scattering

-Compton Scattering

-Photoelectric Effect

-Pair Production

-Photodisintegration

X-rays interact with matter in 5 different ways

-

-

-

-

-

Compton Scattering

Photoelectric Effect

ONLY __________________ and _____________________ are important diagnostically

low energies, below 10kev

Coherent Scattering Occurs at

Classical Scattering

Thompson Scattering

Rayleigh Scattering

Other names for Coherent scattering

-

-

-

...

we do not usually use 10 kEv which is why it is not important to us

whole atom

Coherent Scattering Incident x-rays interact with a

scattered x-ray

Atom become excited

Releases excess energy immediately as a

energy is also equal

Scatter x-ray has wavelength equal to that of the incident x-ray so the

TRUE

(T/F) No energy loss with Coherent Scattering

Incident x-ray -

the x-ray that came into the atom

without a change in energy

Result of Coherent Scatter is change in direction of the x-ray

direction of travel

The difference in the incident and the scattered x-ray is the

NO ionization

No energy transfer so

forward direction

Scattered x-ray is usually scattered in the

is a different direction

give the atom that whole energy and shoots it out scatter x-ray in a different direction not a back scatter. but

Coherent Scatter

NOT important diagnostically-does not mean it does not occur diagnostically, 10kEv not usually used but sometime when lower kVp used this may occur. but because it fogs our image and decreases contrast we prefer not to have it. not nearly as common as the other two. not important.

Energy is too low

It causes fog on the image

Decrease in contrast

Coherent Scattering NOT important diagnostically because:

-

-

-

moderate

Compton Scatter/Effect Involves ______________ energy x-rays

loosely bound OUTER shell electrons

Compton Scatter/Effect Interacts with

Ionization DOES occur

Compton Scatter/Effect Outer shell electron is knocked out or ejected what occurs

Compton electron and scattering x-ray are produced

Interacts with loosely bound OUTER shell electrons

Outer shell electron is knocked out or ejected

Ionization DOES occur

What are produced in this process

Compton electron and scattering x-ray are produced

Compton Scatter/Effect one of the outer shell electrons will be ionized. When this happens

LESS energy than the incident x-ray

Compton Scatter/Effect The scattered x-ray has

Energy loss

Compton Scatter/Effect

what OCCURS

different direction

Compton Scatter/Effect Scattered x-ray travels in a

longer wavelength

Compton Scatter/Effect Scattered x-ray has _________________- than incident x-ray

...

Compton Scatter/Effect Incident x-ray comes in hits outer shell electoron energy from incident electron energy is then transferred to the 2 things. Scatter has less energy because it gets divided toward electron and scatter

less energy

Compton Scatter/Effect longer wavelength due to

difference between the energy of the incident x-ray and the energy of the ejected electron

The energy of the Compton scattered x-ray is equal to the

binding energy plus the kinetic energy it has when it leaves the atom

Compton Scatter/Effect

The energy of the ejected electron is equal to the

...

Compton Scatter/Effect Incident x-ray comes in and ejects electron we loose the energy to the binding energy because we had to knock out the electron and the rest is given to the scatter.

Ei=Es + (Eb+EKE)

Compton Scatter Equation

...

Compton Scatter/Effect the energy when the electron leaves can be more than the binding energy

the energy of the incident x-ray

Ei =

the energy of the scattered x-ray

Es =

kinetic energy of ejected electron

EKE =

binding energy of the ejected electron

Eb =

scattered x-ray and electron

Compton Scatter/Effect

Energy from incident is split between

scattered x-ray

Compton Scatter/Effect

Usually the _____________ retains most of the energy

more interactions before losing all their energy

Compton Scatter/Effect

Both scattered x-ray and electron can undergo

photoelectrically

Compton Scatter/Effect

Scattered x-ray is absorbed how?

Electron

Compton Scatter/Effect

___________ drops into vacancy in electron shell (can replace another whole made by same interaction in an different atom)

equally split.

Compton Scatter/Effect

Maybe not

...

Compton Scatter/Effect

When they leave that can continue to interact with other atoms until all their energy is gone.

partial absorption

Compton Scatter is a -________________ process

180 degrees

Compton Scatter/Effect

Scatter can deflect at any angle from the incident x-ray, including

Angle of deflection

Compton Scatter/Effect

is the angle between the incident x-ray and scattered x-ray

no energy is transferred

Compton Scatter/Effect

At 0 degrees deflection =

more energy is transferred to the Compton electron

Compton Scatter/Effect

As angle of deflection increases closer to 180 degrees

2/3 of incident x-ray energy

Compton Scatter/Effect

Even at deflection of 180 degrees scattered x-ray still retains about

...

Compton Scatter/Effect

The close you get to 180 the more scattered always retains most of the energy from the incident x-ray but closer to closer to 180 it is more likely to share with Compton s

...

Compton electron has more energy at 180 then scattered x-ray false. it gets more at different angles

66%

Compton Scatter/Effect

as the angle of deflection gets closer 180 the Compton electron will get more bu the scatter get 2/3 or ______ of what incident x-ray has

...

Compton Scatter/Effect

it gets more than it usually get but not More than scatter X-ray

Backscatter Radiation

X-rays scattered back in the direction of the incident x-ray

180

Backscatter Radiation______ degree deflection

artifacts on image

Backscatter Radiation Will cause

inversely proportional to x-ray energy (1/E)

The probability of Compton scattering is related how to x-ray energy?

atomic number,

Probability of Compton Scatter Occurring:

Independent of ________________- just as likely to undergo Compton in atom of soft tissue as bone

mass density of absorber

Probability of Compton Scatter Occurring:

Proportional increase in probability with increase in

probability of Compton occurring

Probability of Compton Scatter Occurring:

Increase in energy means decrease in

penetrability with higher energy

Probability of Compton Scatter Occurring:

This is because you have an increase in

mass density how compact something is

How tightly bound together something is-

scatter

decrease kvp increase

NOTHING

increase atomic number what happens

Compton Diagnostically

Important diagnostically

Compton Diagnostically

Can occur with all x-rays

negative way

Compton Diagnostically

Even though important it is in a

Compton Diagnostically

Does not provide useful information to the radiograph

uniform intensity

Compton Diagnostically

Produces _____________________ on the IR

image contrast

Compton Diagnostically

REDUCES __________________

...

Compton Diagnostically

but sometimes like an abdomen we want lower contrast with chest want shades of grey so sometime we need more Compton then other times. give us our grey on our image

radiography and more specifically fluoroscopy

Compton scattered x-rays can create hazard in both

fluoro

A lot of scatter from patient during

Compton Diagnostically

This radiation is the source of MOST of the occupational exposure that radiographer receive

leaves the exam area

Compton Diagnostically Radiography the hazard is less because radiographer

protective shielding in rooms

Compton Diagnostically

Still is enough scatter to need

Compton Diagnostically

is the process that produces scatter so it is the scatter that increases our exposure.

.....

Produces enough scatter which is why we need our control area lined with lead

...

only interacts with outer shell energy given off to thee two. scatted gets whats left when binding and kinetic energy are added together. The direction is changes and wavelength is longer how much Scatter gets most energy

-Outer shell electrons

-Loosely bound electrons

Compton Summary

Most likely to occur

-

-

-Increased penetration - less interactions

-Reduced Compton scattering overall

-Increased Compton when compared to photoelectric

Compton Summary

X-ray energy increases

-

-

-

No effect on Compton scattering

Compton Summary

Atomic number of absorber increases

-

Proportional increase in Compton scattering

Compton Summary

Mass Density increases

-

...

Compton is moderate energies are what interact with your electrons

Partial absorption

Photoelectric Effect

Total absorption process - incident x-ray NOT scattered, totally absorbed

Photoelectric Effect

Occurs in diagnostic range

Moderate

Photoelectric Effect

what energy levels

Photoelectric Effect

Interacts with INNER shell electrons

inner shell electrons

Photoelectric Effect

Ionization OCCURS with

ionized and knocked out

Photoelectric Effect

Electron in one of the inner shells is