Chapter 8 Xray Production

only FINAL review higlights

Chapter 8

What is Characteristic Radiation?

Projectile electron collides with inner-shell electron, removed from target atoms = ionized

What fills the inner shell vacancy (characteristic)? and what is produced?

Outer shell; x-ray emission

What does each photon have?

Has specific energy equal to the difference in binding energies of two shells involved

Projectile Electron=

Photoelectron

Which shell = characteristic x-ray? with what energy?

Only K Shell

with at least 69 keV = Diagnostic radiograph

higher atomic # of target = ?

increased energy

What is Brems Xrays?

Projectile electron passes nucleus of target atom, slows down, changed course and leaves with reduction KE

Which interactions happen in the tube?

Characteristic and Bremsstrahlung

What is lost in Brems X-rays?

energy lost

What do most X-rays = ?

Brems (diagnostic Range)

<69 kVp = what type of interaction?

Brems X-rays

over 69 kVp = Which interaction?

Characteristic and/or Brems

X-ray Emission Spectrum

illustrated relative number of x-rays at each energy levels, from 0 - 100 keV

aka Characteristic Xray

discrete, Specified Spectrum

Characteristic Xray Spectrum binding energy

= 69keV (limited energies)

Mono energetic

one energy

Poly energetic

many energies

Factors that affect size and position of x-ray spectrum

1. mAs

2. kVp

3. added filtration

4. target material

5. voltage waveform

mAs

Change in mAs is DIRECTLY PROPORTIONAL to change in amplitude of spectrum

Examples of mAs increase

if doubled 200 mA to 400 mA = twice the # of projectile electrons (from cathode to anode) = mAs doubled but energy is the same

increase in mAs = ?

increase in amplitude

increase in quantity =

NO change in quality

kVp increase

When kVp is increased = amplitude of spectrum increased BUT also more high energy emitted

kVp High Energy =

• higher potential for multiple penetrability

• increase both energy and quality

Increase voltage ripple =

Decrease quantity and decrease in quality

The shift of the characteristic x-ray spectrum to higher energy will occur because of

an increased in atomic number

Useful characteristic x-rays are produced in tungsten

by ionization of a k-shell electron

Characteristic x-ray

are characteristic of target Z

Brems radiation is produced by

a conversion of projectile electron kinetic energy to electromagnetic energy

If an average radiographic technique is used

most x-rays are bremsstrahlung

In bremsstrahlung x-ray production

the projectile electron is from the cathode

When Brems X-ray is produced

a projectile electron will lose enegry

The wavelength of an x-ray

becomes longer as projectile electron kinetic energy is reduced

An increase in mAs will

increase the number of bremsstrahlung x-rays

The area under the curve of the x-ray emission spectrum us representative of

the total number of x-rays

Normally the x-ray emission spectrum contaisn

both characteristic and bremsstrahlung x-rays

The characteristic x-ray emission spectrum principally depends on which of the following?

target material

The x-ray emission spectrum that represents several energy levels comes from

the x-rays emitted from the tube

Both the shape and position of the characteristic x-ray emission spectrum

correspond to target electron binding energies

Characteristic radiation is produced when

a vacancy in an electron orbit is filled

The x-ray emission spectrum is a plot of

the number of x-rays versus energy

The amplitude of the brems x-ray emissiono spectrum

has max value at an energy approx one third of the kVp

On s general x-ray emissiong spectrum, what 2 items are affected?

Quantity and Quality

Most of the x-rays produced at the target are

Bremsstrahlung

In order to construct an x-ray emission spectrum, one must know the

number of x-rays at each energy intervals

The wavelength of an x-ray is

inversely proportional to its energy

Minimum wavelength is related to

the KE of the Projectile Electron

The region of the x-ray emission spectrum associated with minimum wavelength

highest-energy brems x-ray

To calculate minimum x-ray wavelength, one must know the value of

kVp

Chapter 9