Quantity and quality X ray

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1. What happens to the energy of the electron beam striking the tube target as kV is increased?

Penetration is the degree to which X-rays have passed through the body. Increasing the kVp increases the potential difference between the cathode and anode, thus

increasing the energy of each electron when it strikes the target. The greater the potential difference the faster the electrons travel from the cathode to the anode.

The increased number of high-energy photons by use of higher kVp results from the greater efficiency in the production of Bremsstrahlung photons that occurs when increased number of higher-energy electrons interact with the target. High-energy x-ray photons have a greater probability of penetrating matter. In our experience, with increasing kVp, increased mR that means penetrating capability of x-ray  is increased and it plotted below.

        …..kVp

Al

60. 70. 80. 90. 100 110 120
0   660   1166   1774  
1 mm              
2              
3        336          
4               592    
5           908  
6              
7              

 

2. What happens to the energy of the electron beam striking the tube target as mAs is increased?

As the mA setting is increased, more power is applied to the filament, which heats up and releases more electrons. Increasing mAs results more photons to be formed. This is beneficial when bigger parts are imaged, because they require more photons.

 

…..mAs

Al

30. 40. 50. 63. 70. 80 90
0   922   1468   1872  
1 mm              
2              
3              
4             470      748        954  
5              
6              
7              

 

3. Define quantity and quality as it applies to an X-ray beam. (2 marks).
The quality of the x-ray beam is controlled by the amount of voltage. X-ray Quality is a measurement of the penetrating capability of x-ray beam. Penetrability describes the distance an x-ray beam travels in matter. X-ray quality is numerically represented by half-value layer. HVL is the thickness of absorbing material needed to reduce the x-ray intensity (quantity) to half its original value. X-ray quality is affected by kVp and filtration. The x-ray beam quantity is controlled by the mA. X-ray quantity is the number of x-ray photons in the useful beam. Unit of measurement is roentgen (R). It is affected by mAs, kVp, distance and filtration

 

4. What effect does changing kV have on quantity and quality of an X-ray beam? Support your answer with your experimental data.

As quality of an x-ray beams increases the penetrating ability of X ray increased. Increasing kVp will increase the speed and energy of the electrons applied across the x-ray tube. In our lab experience we have changes shown with table below . As shown on table with increasing kV, the mR is increased and for reaching to HVL we needed more sheet of Al. It characterize the penetrating quality of an x-ray beam by its half-value

layer. We made difrent thickness of an absorber (aluminum), required to

reduce by one half the number of x-ray photons passing through it . The table describes as the average energy of an x-ray beam increases, so does it HVL.

 

mAs kVp mR- without Al filter mR- HVL
50 70 660 336
50 90 1166 592
50 110 1774 908

 

5. What effect does changing mAs have on quantity and quality of an X ray beam? Support your answer with your experimental data.

mA is a measurement of x-ray tube current (the number of electrons crossing the tube from cathode to anode per second). As mA increases so does the number of electrons. mA is directly proportional to the tube current. mAs is the primary controller of x-ray quantity. mAs doubles, x-ray exposure doubles.In our lab experience we had next changes and it shows the increasing the mA, result to increasing x-ray exposure.

 

mAs kVp mR- without Al filter mR- HVL
40 90 922 470
50 90 1468 748
63 90 1872 954

 

 

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