characteristic radiation in tungsten targets shel l # of electrons binding energy l char m char n...
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Characteristic Radiation in Tungsten Targets
Shell
# of electrons
Binding
energyL
Char
M
Char
N
Char
O
Char
P
Char
Eff
X-ray
Energy
K 2 69 57.4 66.7 68.9 69.4 69.5 69
L 8 12 9.3 11.5 12 12.1 12
M 18 3 2.2 2.7 2.8 3
N 32 1 0.52 0.6 0.6
O 12 0.1 0.08 0.1
P 2
• In a tungsten target, at any kVp less than 69.5 all x-rays are Brems.
• At 100 kVp, 85% of photons are Brems and 15% are characteristic
• Only 15 different energy levels are possible with characteristic production in tungsten tube.
Lecture 5: Patient Dose Management
21
determine energy of electrons energy of X-ray photons
determine number of electrons number of X ray photons
Lecture 5: Patient Dose Management
22
X-ray tube
Photons entering the human body will either penetrate, be absorbed, or produce scattered radiation
Lecture 5: Patient Dose Management
23
Image Contrast
No object image is generated
Object image is generated
Object silhouettewith no internaldetails
Where do X-rays come from ?
Nucleus
Electrons
Atom of the target element Characteristic X-ray
Bremsstrahlung