Chapter 7 X-ray production Flashcards
The relationship b/w x-rays and the electromagnetic spectrum.
X- ray production
The transport of energy through space as a combination of “electric”and magnetic fields.
Electromagnetic Radiation
All members of the electromagnetic spectrum, including x- rays, travel at the speed of light which is:
186,000 miles/sec
3x10^10 cm/ sec
3x10^8 m/sec
X-rays differ from other members of the EM spectrum in:
wavelength, frequency, energy and penetrating ability.
the distance b/w any two “successive” points on a wave.
Wavelength
Wavelength is usually measured from to:
Crest to crest
Wavelength it is represented by the Greek letter
lambda ( λ )
wavelength units are:
angstroms (Å)
1 Å is equal to
1/100,000,000 cm or 1X10^-8
useful range in diagnostic radiology:
0.1 to 0.5 Å
Frequency:
The number of cycles per second
Frequency is represented by? and its units are?
Nu (V) ; Hertz
which colors are found in Visible Light
red,orange, yellow,green,blue,indigo, violet.
Gamma rays range:
.5 Å ——- .1 Å
Bremsstrahlung (Brems) radiation are:
Heterogeneous or polyenergetic
Brems makes up _______of the primary beam in the 80-100 Kvp range.
90%
Energy of the resulting x-ray photon depends on the distance of the _______/_______from the nucleus of the target atom and the amount of kinetic energy lost by the incident e-.
projectile/ incident e_
energies of the resulting x-ray photon can range from
0 Kev to the Kev equivalent of the Kvp.
Quantity is control by?
mAs
Quality is control by?
Kvp
Energy of the resultant x-ray is “characteristic” of the “target” element (W) and the “ shells” involved in its production.
Characteristic Radiation
binding energy of the K shell is
69
Characteristic Radiation makes up ——— of the primary beam in the 80- 100 Kvp range.
10%
no useful characteristics radiation produced below——
69 Kvp
A photoelectron (negative ion and a positive Ion makes an:
ION PAIR
Characteristic x-ray emission spectrum for tungsten contains:
15 different x- ray energies
To increase the “ probability” of characteristic radiation forming
The incident e- must have a “Kev” >but close to the” Binding “ energy of the “K” shell e-.
Tungsten binding energy of K shell
70 Kev
To increase the “ probability” of characteristic radiation forming.
The target should have a high “Atomic Number”
The primary beam is?
polyenergetic
What are the 4 reasons the primary beam is polyenergetic:
A..The fluctuating “Kv” applied to the tube(a small amount of” Ripple” in the rectified voltage)
B. the combination of “Brems” and “Characteristics” radiations.
C.The multiple e- interactions with the target atoms.
D. The production of “ off focus radiation..
off focus radiation
e- from the cathode interact with the target only at the focal spot. however some of the e- bounce off the focal spot and then land on other areas of the target.
efficiency of x-ray production formula
%Eff.= (K)(Z)(Kvp)
at 80 Kvp:
0.6% production of x-rays; 99.4% production of heat.
Electrons from the cathode colliding with the outer shell e- of the target atoms results in:
Heat production
behavior of x-rays
sometimes they behaved as a” wave” and other times behaved as a “particles. “
sometimes they behaved as a” wave” and other times behaved as a “particles. “ this is known as the:
wave - particle duality
X-rays exists as vibrating electric charges or waves
Wave theory . C= λV
Wave theory C=λV
C=speed of light, and is always constant
λ= Wavelength in Cm (lambda)
V=Frequency in hertz (nu)
Wavelength is
“inversely” proportional to frequency and viceversa
X- rays exist as particles of energy theory:
E= h v
E= h v
E=photon energy
h= plank’s constant (4.15 x 10-15 eV-sec)
v=Frequency in Hertz
photon energy is ____ proportional to frequency
directly
wavelength formula; angstroms unit of minimum λ of any photon
λmin (λ)= 12.4/Kvp
photon Energy formula=
12.4/ λ (Å)
properties of x-rays:
1.Highly penetrating and ‘INVISIBLE”
2. Electrically ‘NEUTRAL”
3. Heterogeneous or polyenergetic
4. Liberate minute amounts of ‘HEAT”
5. Move in straight, “DIVERGENT”
lines from the focal spot
6. Travel at the “ SPEED OF LIGHT”
7. cannot be ‘FOCUSED by a lens
8. Produced “secondary” and scatter radiation
9. Capable of “IONIZING gases
10. Cause “FLUORESCENCE” of certain crystals
11. Affect photographic film
12. Produce chemical and biologic changes by “IONIZATION and excitation.
Refers to the ability of an x-ray beam to ““PENETRATE” matter.
Quality of X-ray beam
2 methods for the quality of X-ray beam:
- Half - value Layer: the thickness of a specified material (metal) which reduces the exposure rte to “1/2” its initial value.
- Applied Potential (Voltage ):For radiography the “PEAK” Kv is customarily used to designate beam quality, since the HVL does not routinely serve a useful purpose.
Properties of an X-ray beam as KVv or filtration is INCREASED:
- Beam quality ↑
- Beam energy ↑
- Beam penetrating ability ↑
- Quantity of X-rays with shorter wavelengths ↑
- Quantity of X-rays with longer wavelengths ↓
- Quantity of X-rays with higher frequencies ↑
- Quantity of X-rays with lower frequencies ↓
- Hardness of the beam ↑
A filter helps to:
Harden the beam via the process of photoelectric Effect.
characteristic x rays are emitted:
when an outer shell e- fills an inner -shell void.
approximately how much of the kinetic energy of projectile e- is converted to heat.
99%
only__________ x- rays of tungsten are useful for imaging
the K- characteristic
________ x rays are produced when a projectile e- is slowed by the nuclear field of a target atom nucleus
brems x rays
in the diagnostic range,most x-rays are
brems
A change in Kvp
affects both the amplitude and the position of the x ray emission spectrum
increasing Kvp increases
the quality of an x ray beam
increasing filtration increases
the quality of an x ray beam
added filtration results in
increased HVL
x ray quality can be identified by
Kvp or filtration, but HVL is most appropriate
adding filtration reduces
pt . dose
attenuation
is the reduction in x-rays intensity the results from absorption and scattering.
which is the best method for specifying x- ray quality?
HVL
______________ is one description of the ability of an x-ray beam to pass through tissue
penetrability
x ray_______is the number of x-rays in the useful beam
quantity
Brems x-ray emission spectrum extends from:
zero to maximum projectile electron energy, with the highest number of x-rays having approximately 1/3 the maximum
Electromagnetic Radiation :The transport of energy through space as a combination of ___and ____.
electric and magnetic fields.
