Equations Flashcards
What does Io (I knot) stand for?
The inital intensity before passing through matter
What does x stand for in relation to photons passing through matter?
The thickness of the material
What does I stand for in relation to photons passing through matter?
The intensity after going through the material
What is the probability of the photoelectric?
Probability of PE=denisty (Z^3)/E^3
What is the probability of compton scatter?
Probability of CS=denisty/E
How do you find the kinetic energy of a photoelectron?
Incident x-ray photon E-BE of electron
How do you find the energy of the primary photon with the photoelectric effect?
EP=EBE+EKE
EP=energy of the primary photon
EBE=Binding energy of the orbial electron
EKE=kinetic energy of the photoelectron
How do you find the energy of the primary photon during a compton electron interaction?
EP=ES+EBE+EKE
EP=energy of the primary photon
EBE=Binding energy of the orbial electron
EKE=kinetic energy of the recoil electron (compton electron)
ES=Energy of the scattered photon
Within the patients body, a 30 kV x ray undergoes a photoelectric interaction with a k-shell electron in a calcium atom. IF the e- binding E of a K-shell e- in a calcium atom is 4kV, what will be the kinetic energy of the photoelectron speeding away from the atom?
EP=EBE+EKE
30=4+x
x=26 kEV
Within the patients body, a 40 kV x ray undergoes a CS interaction with an L-shell e- in a calcium atom. The absolute value for the binding E of the L shell is .5 KV. The compton (recoil) e-speeds away from the atom with 5kV of KE. What is the energy of the compton scattered photon?
EP=ES+EBE+EKE
40=x+.5+5
40-.5-5=34.5
What is the probability of an 80 keV x-ray interacting with fat (z=6.3) and barium (z=56) compared to soft tissue (7.4)?
Clarify with teacher
How much more likely is an x ray to interact with bone (z=13.8) than with muscle (z=7.4)
(13.8/7.4)^3=2628/405=6.5
How do you find the TMAC?
Divide total linear attenuation (u) by density (p)
What is the unit for PE absorption?
t
What is the unit for CS?
o (sigma)
How do you find the PEMAC?
t/p
How do you find the CEMAC?
o/p
How do you find the probability of P.E. absorption when using PEMAC?
t/p (z^3)/E^3
How do you find the probability of compton scatter when using CEMAC?
o/p(p)/E
The HVL of a beam of radiation is 3mm of tin. What % of the beam will be transmitted though a tin sheet 9mm thick?
12.5 %
What does e represent?
Base of the natural log
What is the basic logarithmic function formula?
Logb(X)=Y
b^y=X
What is log3(9)=?
3^x=9
x=2
What is logx(1)=?y
X^y=1
y=0
What is the base of the natural log?
e=2.718
How do you calculate the intensity after passing though a material?
I(x)=(Io)e^-ux
How do you find the attenuation coefficent?
u=-ln(Ix/Io)/x or u=-ln(0.5)/HVL
How do you find the HVL?
I(x)/Io=.5
How do you calculate the TVL?
TVL=2.303/u
If 6x10^7 x ray photons enter a 2cm thick layer, what will be the number of x ray photons transmitted though the layer if u=1.42?
3.5x10^6
What is the attenuation coefficient of a certian material if we know that 5cm of the material absorbs 80% of the gamma rays?
0.322 cm
How do you calculate the PMT gain?
PMT gain=g^n
g=dynode gain
n=number of dynodes
An 8 stage PMT (8 dynodes) has a dynode gain of 3. What is the PMT gain?
PMT gain=g^n
=6561
How do you calculate flux gain?
Flux gain= # of output light photons/ # of input x ray photons
How do you calculate minification gain?
Minification gain=d1^2/do^2
d1=Diameter of the IP
do=Diameter of the OP
How do you calculate brightness gain?
Brightness gain=Flux gain x minification gain
What is the brighness gain for a 17 cm II tube with a flux gain of 120 and a 2.5 output phosphor?
5548.8
How do we find the electronic magnification factor?
MF=IP new size/IP old size
How magnified is the image of a 25/17/12 II in the 17 cm mode compared with that produced in the 25 cm mode?
MF=1.47 times more magnififed in the 17 cm mode
A 23/15/10 II tube is sued in the 10 cm mode. How much higher is the patient dose in this mode compared with the 23 cm mode
5.29 times higher in the 10 cm mode
How do we find the patient dose factor?
Patient dose factor=(IP old size/IP new size)^2
