Problem 1(10 marks)
Problem 1 (10 marks) A y-ray of frequency 6 x 1020 Hz collides with an atom and undergoes Compton scattering. If the change in the angle of the y-ray is 30° what is the frequency of the wave as it exits the atom?
Problem 2 (10 marks) What is the radiation contrast for lead if two thicknesses of 8.0 mm and 8.4 mm are used to measure it? Assume that the attenuation constant for lead is 3.5 cm-' and the build up factor is 4.0.
Problem 3 (10 marks) a) During a measurement ofa film it is found that 6.5 % of the light passes through the film. What is the optical density of that film? b) For another film it is found that the optical density is 1.4. What percentage of light gets through the film?
Problem 4 (10 marks) a) A characteristic curve for a particular brand of film shows the following values. What is the gradient, G, of this film?
b) A film with a gradient of 10 has the following values. What would the exposure be at K2?
Problem 5 (10 marks) What is the granularity of a film if the following 8 measurements are taken using a microdensiometer? Number I 2
3 4 5 6 7 8
Optical Density D, D2 DJ D. D, D6 D, D,
Measurement 1.978917085 2.010227217 1.973853014 2.029188123 1.974563634 2.026266777 2.012200998 197399667
Problem 6 (10 marks) Using the reference values of S, = 1.98 and C, = 1.24, a film is tested using the step wedge approach, and is found to have the following values: Do = 0.16, D, = 2.12, D, = 3.41. Calculate the new values for the speed index and contrast index, and check to see if the deviation from the reference values is within the permissible tolerances of," I0% for the speed index and -10% to + 15% for the contrast index and that the fog is less than 0.3.
Problem 7 (10 marks) Find the minimum source-to-object distances for Class A and Class B, if the value ofb is 20 mm and d is 1.2 mm, using either the equations or the nomogram.
Problem 8 (10 marks) A pinhole camera is used to detennine the focal spot size. The distance from the source to the diaphragm is 80 mm, the distance of the diaphragm to the film is 40 mm, and the measured size is 1.5 mm (a) What is the focal spot size? (b) If the distance between the source and the film stays constant, using the same focal spot as in a), where would the aperture have to be placed to get a measured image size of 2 mm?
Problem 9 (10 marks) (a) Using the exposure chart in Fig. I, what would be a suitable exposure time for a sheet of steel 2.0 cm thick, if the current used is lOrnA? (b) Using an exposure chart it is found that the exposure required using a Co-60 source is 3200 GBq.min when the FFD is 500mm. If the source that is used has an activity of740 G Bq, and the actual FFD is 400mm, what is closest to the recommended exposure time?
Problem 10 (10 marks) (a) In a radiographic system, the focal spot size, d, is 2.5 mm, the object to film distance, b, is 5 mm, and the source to object distance, 1',is 60 mm. What is the geometric unsharpness? (b) An X-ray film of Type A is subjected to an exposure 01'20 mA.min and achieves a density 01'2.5. Iftype C film is used instead, use Figure 2 to find the exposure that would be required to achieve the same density.
Exposure diagram
, ,
, ,
500
I j
,
,
500
I , I
1
I
!
I
! ,00
2(1)
100
50
III
10 lS0VOLT 320/13
, ;
~1.5
mm 6."
4 rnA
mm l"".,=13 Film= Agfa 07 FFA~ 800 mm d •••..••=4.0
)
rnA
SCreens: Pb 0.02/0.02 mm 0:2.2 Malerial: Fe
I
I I
o
30
;5
~H -I' wlmrn)--
Figure I X-ray exposure diagram
,
o
1
10
100
'000
10:0:)
Rolatlve ExpGSum
Figure 2 Characteristic curve for Problem 1O(b)
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Problem 2 (10 marks) What is the radiation contrast for lead if two thicknesses of 8.0 mm and 8.4 mm are used to measure it? Assume that the attenuation constant for lead is 3.5 cm-' and the build up factor is 4.0.
Problem 3 (10 marks) a) During a measurement ofa film it is found that 6.5 % of the light passes through the film. What is the optical density of that film? b) For another film it is found that the optical density is 1.4. What percentage of light gets through the film?
Problem 4 (10 marks) a) A characteristic curve for a particular brand of film shows the following values. What is the gradient, G, of this film?
b) A film with a gradient of 10 has the following values. What would the exposure be at K2?
Problem 5 (10 marks) What is the granularity of a film if the following 8 measurements are taken using a microdensiometer? Number I 2
3 4 5 6 7 8
Optical Density D, D2 DJ D. D, D6 D, D,
Measurement 1.978917085 2.010227217 1.973853014 2.029188123 1.974563634 2.026266777 2.012200998 197399667
Problem 6 (10 marks) Using the reference values of S, = 1.98 and C, = 1.24, a film is tested using the step wedge approach, and is found to have the following values: Do = 0.16, D, = 2.12, D, = 3.41. Calculate the new values for the speed index and contrast index, and check to see if the deviation from the reference values is within the permissible tolerances of," I0% for the speed index and -10% to + 15% for the contrast index and that the fog is less than 0.3.
Problem 7 (10 marks) Find the minimum source-to-object distances for Class A and Class B, if the value ofb is 20 mm and d is 1.2 mm, using either the equations or the nomogram.
Problem 8 (10 marks) A pinhole camera is used to detennine the focal spot size. The distance from the source to the diaphragm is 80 mm, the distance of the diaphragm to the film is 40 mm, and the measured size is 1.5 mm (a) What is the focal spot size? (b) If the distance between the source and the film stays constant, using the same focal spot as in a), where would the aperture have to be placed to get a measured image size of 2 mm?
Problem 9 (10 marks) (a) Using the exposure chart in Fig. I, what would be a suitable exposure time for a sheet of steel 2.0 cm thick, if the current used is lOrnA? (b) Using an exposure chart it is found that the exposure required using a Co-60 source is 3200 GBq.min when the FFD is 500mm. If the source that is used has an activity of740 G Bq, and the actual FFD is 400mm, what is closest to the recommended exposure time?
Problem 10 (10 marks) (a) In a radiographic system, the focal spot size, d, is 2.5 mm, the object to film distance, b, is 5 mm, and the source to object distance, 1',is 60 mm. What is the geometric unsharpness? (b) An X-ray film of Type A is subjected to an exposure 01'20 mA.min and achieves a density 01'2.5. Iftype C film is used instead, use Figure 2 to find the exposure that would be required to achieve the same density.
Exposure diagram
, ,
, ,
500
I j
,
,
500
I , I
1
I
!
I
! ,00
2(1)
100
50
III
10 lS0VOLT 320/13
, ;
~1.5
mm 6."
4 rnA
mm l"".,=13 Film= Agfa 07 FFA~ 800 mm d •••..••=4.0
)
rnA
SCreens: Pb 0.02/0.02 mm 0:2.2 Malerial: Fe
I
I I
o
30
;5
~H -I' wlmrn)--
Figure I X-ray exposure diagram
,
o
1
10
100
'000
10:0:)
Rolatlve ExpGSum
Figure 2 Characteristic curve for Problem 1O(b)
, ; ;
