Rt-l3 Q&a

RT LEVEL-III MODEL QUESTION PAPER BY: N.KUPPUSAMY Some step wedges were used to produce 6 sets of radiographs of same density at same processing parameters. Same kV was used to expose each set of radiographs. The thickness and corresponding exposure times are as follows: Set # 1 S.No. 1. 2. 3. 4.

Set # 2 Thickness (mm) 2.5 5.0 8.0 10.0

Exposure time 3 minutes 7 minutes 20 minutes 40 minutes

S.No. 1. 2. 3. 4.

Set # 3 S.No. 1. 2. 3. 4.

Exposure time 1.8 minutes 3.0 minutes 5.0 minutes 8.3 minutes

Set # 4 Thickness (mm) 10.0 12.5 14.5 18.5

Exposure time 4.4 minutes 7.0 minutes 10.1 minutes 21.2 minutes

S.No. 1. 2. 3. 4.

Set #5 S.No. 1. 2. 3. 4.

Thickness (mm) 2.5 5.0 7.5 10.0

Thickness (mm) 4.0 6.0 9.0 12.0

Exposure time 3.5 minutes 4.2 minutes 5.5 minutes 7.2 minutes

Set # 6 Thickness (mm) 8.0 11.0 13.0 16.0

Exposure time 2 minutes 3 minutes 3 min. 56 sec. 5 min. 54 sec

S.No. 1. 2. 3. 4.

Thickness (mm) 5 7.5 10.0 14.0

Exposure time 1.5 minutes 2.1 minutes 2.95 minutes 5.08 minutes

Answer the following questions based on the above data c. Set # 2 exposed with higher kV d. Both a & b e. Both b & c

1. What is the HVL for Set # 1 radiographs? a. b. c. d.

1.8 mm 2.0 inches 2.0 mm 6.0 mm

8. What is the difference between Set #5 and Set # 6 radiographs? a. b. c. d. e.

2. What is the HVL for Set # 2 radiographs? a. b. c. d.

2.5 mm 3.4 mm 2.0 mm 4.0 mm

9. Which set-up gives maximum back scattering?

3. What is the HVL for Set # 3 radiographs? a. b. c. d.

a. b. c. d.

4.0 mm 3.4 mm 3.6 inches 3.7 mm

a. b. c. d.

7.5 mm 7.7 mm 8.0 mm 3.7 mm

a. b. c. d. e.

5.1 mm 7.7 mm 17.0 mm 15.0 mm

6. What is the HVL for Set # 6 radiographs? a. b. c. d.

A C D E

11. Which set-up produces maximum enlargement?

5. What is the TVL for Set # 5 radiographs? a. b. c. d.

A C D E

10. Which set-up gives minimum back scattering?

4. What is the HVL for Set # 4 radiographs? a. b. c. d.

Set # 6 exposed with higher kV and same mA than Set # 5 Set # 6 exposed with lower kV and higher mA than Set # 5 Set # 5 exposed with higher mA & same kV Set # 5 exposed with lower mA and same kV Both sets were exposed identically

B C E F G

12. Which set-up meets the requirement unsharpness? (Discard back scatter)

17.0 mm 6.0 mm 4.7 mm 5.1 mm

a. b. c. d. e.

7. What is the difference between Set # 1& Set # 2? a. Set # 2 exposed with same kV and higher mA b. Set # 1 exposed with higher kV and lower mA

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of

minimum

A C D E All of the above

Feb 1998

RT LEVEL-III MODEL QUESTION PAPER BY: N.KUPPUSAMY Answer Questions from 9 to 16 based on the following radiographic exposure arrangements: Source

Source

Source

Film Film

Object

Object

Film Object Ground

A.

Ground

B.

Ground

C.

Source

Source

Source

Object

Film Film Object Ground

D.

Object

Lead Sheet

E.

Lead Sheet

Ground

Lead Sheet

Film

F.

Ground

Source

Film Object

Lead Sheet

G. 13. Which set-up gives maximum unsharpness?

15. Which set-up eliminates or reduces scattering from the object?

a. b. c. d. e.

a. b. c. d. e.

B C F E G

B E F both ‘a & b’ both ‘a & c’

14. Which set-up among A, C, D, E, & G produces highest Penumbral shadow?

16. Which set-up gives least scattering from the lead sheet?

a. b. c. d. e.

a. b. c. d. e.

C G D A E

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D E F G None of the above

Feb 1998

RT LEVEL-III MODEL QUESTION PAPER BY: N.KUPPUSAMY An exposure chart for steel is given below. Each line depicts a type of film. The radiographic equivalence factor for Steel, Aluminum and Brass is 1, 0.18, and 1.3 respectively.

1 2

3

4

5

mA.Minutes

6 42

7

28

1"

2" 3" Thickness (inches)

4"

5"

Answer Questions from 17 to 30 using this chart 17. a. b. c. d.

Which is the fastest film? type-1 type-3 type-7 type-5

a. b. c. d. e.

type-3 type-4 type-5 both ‘a & c’ both ‘b & c’

18. a. b. c. d.

Which is the slowest film? type-1 type-3 type-7 type-5

19. a. b. c. d.

Type-2 film is _______ faster than type-1 slower than type-3 both ‘a & b’ none of the above

24. Which film produces best radiograph (with good contrast and latitude) when radiograph a specimen with the thickness of 2.25” & 2.75”. a. type-3 b. type-4 c. type-5 d. type-6 e. type-7

20. a. b. c. d. e.

Type-4 film is ________ slower than type-3 faster than type-3 faster than type-5 both ‘a & c’ both ‘b & c’

21. a. b. c. d.

Which film has widest latitude? type-6 type-5 type-4 type-3

25. Which film gives lowest contrast? a. type-3 b. type-4 c. type-6 d. type-7 26. Type-3 & type-4 films were used to radiograph a 2” thick specimen. Type-3 film was exposed for 7 minutes, while type-4 film was exposed for 5 minutes. The mA and FFD were same for both exposures. Which film gives high density? a. type-3 gives high density b. type-4 gives high density c. both gives same density d. none of the above

22. A specimen with a thickness range of 0.7” to 1.2” has to be radiographed. Which of the following will give most satisfactory radiograph? a. type-1 b. type-2 c. type-3 d. any of the above

27. Type-5 & type-6 films were used to radiograph a 3.5” thick steel specimen at same FFD. Type-5 exposed for 6 minutes type-6 exposed for 7 minutes. What could be the reason? a. type-5 exposed with lower mA b. type-6 exposed with higher mA c. type-5 exposed with higher mA d. type-6 exposed with higher FFD e. some other reasons which are not mentioned above

23.

28. Type-7 film is best suited when radiographing: a. test part thickness less than 3 inches

Type-6 film at one point matches the speed of:

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Feb 1998

RT LEVEL-III MODEL QUESTION PAPER BY: N.KUPPUSAMY b. c. d.

test part thickness between 3 to 5 inches test part thickness above 5 inches test part thickness below 0.5 inch

29. a. b. c. d.

Which film can be used to radiograph 2” thick Aluminum? type-1 type-2 type-3 type-4

30. a. b. c. d. e.

Which film can be used to radiograph 3” thick brass? type-5 type-6 type-7 both ‘a & b’ both ‘b & c’

Concrete wall

Halve Value Layers Co.60

Ir-192

Cs-137

12.7 mm 22.0 mm 66.0 mm

5.00 mm 15.5 mm 48.25 mm

6.35 mm 17.25 mm 53.3 mm

Spherical Lead container 25.4mm thick

Concrete wall - 132mm thick 34. If the dose rate at 1 meter from concrete wall is 0.8 mRem/hr for Ir-192 source, what would be the source strength? a. 84 Ci b. 87.8 Ci c. 4.5 Ci d. 7.8 Ci

Radiation Output at one foot per Ci Source

Co.60

Ir-192

Cs-137

Th-170

Output

14.5 R/hr

5.9 R/hr

4.2 R/hr

0.03 R/hr

Half-Life 1. Co.60 2. Ir.192 3. Cs.137 4. Th.170

44mm thick

Internal Dimension:8M3

10 meters

A Co-60 source of 3.8 Ci strength is kept at the center of lead sphere with internal radius of t” and thickness of 25.4 mm. This sphere is placed at the center of a hollow steel cubical container of 8m3 internal dimensions and 44 mm thickness. This cube is placed at the center of a concrete room of internal dimensions 10m x 10 m x 10m and wall thickness of 132 mm. Refer adjacent figure for schematic diagram.

Source /Material Lead Steel Concrete

Steel Cubic container

= 5.3 years = 75 days = 30 years = 130 days

Answer the following questions based on these. 31. Minimum cordoning off distance from the source for safe radiation level of 0.2 mRem/hr is: a. 14.14 meter b. 20 meter c. 20 feet d. 28.28 meter 32. What is the radiation level at 1 meter from the outer surface of concrete wall? a. 2.1 mRem/hr b. 42.8 mRem/hr c. 136 mRem/hr d. none of the above 33. If the dose rate at 6 meter from concrete wall is 3 mRem/hr, what would be the source strength? a. 17664 Ci b. 17.664 Ci c. 1.6 Ci d. 0.483 Ci

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35. If the thickness of concrete is now reduced to 3.9” and size of concrete room is reduced to 8m x 8m x 8m and thickness of steel cube is increased to 66 mm. Minimum cordoning off distance from the source for safe radiation level of 0.2 mRem/hr is: a. 55.15 feet b. 55.15 meter c. 16.80 feet d. 28.00 meter 36. If the source is replaced by Cs-137 and safe radiation level of 0.2 mRem/hr is achieved at 15 meter from the source. Strength of source is: a. 52 Ci b. 32 Ci c. 60 Ci d. 84.35 Ci 37. If the lead sphere is now removed, what will be the minimum cordoning of distance for 60 Curie Cs-137, if safe radiation level is 0.4 mRem/hr? a. 416 feet b. 42 meter c. 84.8 meter d. 60 meter 38. If the maximum permissible dose is 16 mRem/day, How long can a worker work at a distance of 10 meters from the concrete wall, when the activity of stored source is 30 Ci of Co-60. a. 57 hours b. 0.53 hours c. 5.7 hours d. 8 hours 39. A 34 Ci Cs-137 source is kept inside the lead sphere and the steel container thickness is increased to 100 mm. What is the radiation level at the external surface of the steel container?

Feb 1998

RT LEVEL-III MODEL QUESTION PAPER BY: N.KUPPUSAMY a. b. c. d.

c. d.

15 mR/h 3.74 mR/h 12.37 mR/h 10.97 R/h

Answer Question # 40 to 43 based on the below description: In the above storage facility a source was stored inside the lead sphere. Dose rate on the surface of steel cubical container measured after 11.4 days & 22.8 days was 9.0 mR/h & 8.1 mR/h respectively. 40. a. b. c. d.

What is the half life of the source? 75 minutes 75 days 100 minutes 130 days

41. a. b. c. d. e.

What is the type of source? Ir-192 Cs-137 Co-60 Th-170 more information required

42. a. b. c. d. e.

If the source is Ir.192, What was the initial activity? 5.3 Ci 4.3 Ci 24 mCi 176.8 Gbq None of the above

characteristic curve do not indicate fog density none of the above.

46. Characteristic curves are drawn for 4 different films and the average gradients at the two specified densities calculated as 4, 3, 2, and 1. The film having highest gradient is by definition: a. Renders large density difference with limited change in exposure. b. has highest film contrast at that specified densities with corresponding change in exposure. c. both ‘a and b’ d. neither ‘a nor b’ 47. Find the average gradient from the characteristic curve for film A, between densities 2.0 and 2.5. a. 6.2 b. 5 c. 8 d. 1.5

3.5 3 2.5

Density

2 1.5 1

43. How long will it take to reduce the leakage level to 3 mR/hr from the initial dose rate at the steel container surface? a. 130.3 minutes b. 360.7 days c. 130.3 days d. 75 days 44. From the characteristic curve given below calculate the gamma or the average gradient at the given densities. a. 2.5 b. 1.25 c. 3.0 d. 4.0 3.5 3

Density

1.5 1 0.5 0 Log(Relative Exposure 1 2 3 4 ) 1.3 51.7

45. is: a. b.

0 1

2

3

4

Log(Rel. Exp )

5

6 0.3 0.4

7

48. 10 Ci Iridium-192 with 3x3 mm size was used to take a radiograph of 35 mm steel specimen. The exposure was 20 minutes. The same specimen was radiographed with 5 Ci source of size 1x1 mm. As per code the image unsharpness should not exceed 0.02 inch, and all other conditions remaining unchanged. What would be the new exposure time? a. 40 min. b. 4.4 min. c. 6.6 min. d. 10.5 min. 49. The average gradient of brand A film is 1.25 between the densities 2 and 2.3. What is the Relative Exposure for density 2.3, if the Relative Exposure for density 2 was 1.1 a. 1.4 b. 2.53 c. 1.91 d. None of the above

2.5 2

0.5

6

The fog density of the film given in the characteristic curve difference in densities between 2.5 and 2.0 0.5

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50. In the above problem, if 10 mA.min was the exposure for density 2.0, What would be the exposure for density 2.3? a. 66.06 b. 20.21 c. 32.00 d. 17.36 51. The radiation level at 4 meters from Co-60 source after passing through 1HVT and 1TVT was found to be 40mR/hr, the activity of the source is: a. 10 Ci

Feb 1998

RT LEVEL-III MODEL QUESTION PAPER BY: N.KUPPUSAMY b. c. d.

a. b. c. d.

273.06 GBq 9.5 Ci 27.306 Ci

52. A 20 minutes exposure is made with 4x4 mm 10 Ci Iridium192 source on 25 mm specimen at 700 mm SFD and a satisfactory film density is obtained. It is now required to repeat the exposure using 1 Ci 0.5x0.5 mm source with the same Ug. What is the exposure time? a. 25 minutes b. 7.8 minutes c. 4.9 minutes d. 4.0 minutes e. Exposure does not change as the distance is compensated with the size of the source. 53. A steel plate 37.5 mm thick is radiographed with Ir-192 source using D-5 film for a density of 2.0. Exposure time for this radiograph is 9 minutes. If a lead plate of 23.5 mm thickness is to be radiographed with the same source using same film and required density is 2.50. Required exposure time will be: (log relative exposure for density 2.0 and 2.5 is 2.55 and 2.65 respectively) a. 30 minutes b. 55 minutes c. 60 minutes d. 72 minutes 54. A 19 mm thick plate was radiographed with an Ir.192 source, and density achieved is 2.9. Exposure time with 750 mm SFD was 12 minutes. Plate of 8.2 mm thickness is to be radiographed with the SFD of 500 mm after 120 days using a similar type of film. Exposure time for this exposure will be: a. 6 minutes b. 12 minutes c. 18 minutes d. 24 minutes 55. An object is radiographed with an x-ray source, using D-7 film and a density of 3.5 is achieved with an exposure of 5 minutes. Using same setting of x-ray machine, radiograph is to be repeated with D-2 film and a density of 2.0 is to be achieved. Exposure time for this radiograph will be: (refer graph on page 13) a. 20 minutes b. 08 minutes c. 40 minutes d. 31.75 minutes 56. A 20 mm thick plate is radiographed with Ir-192 using D-5 film for 2.0 density with an exposure time of 12 minutes. If a 30 mm thick steel plate is to be radiographed with same source and film for the density of 1.50. Exposure time for this new exposure will be:

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26.50 min. 13.30 min. 5.50 min. 19.0 min.

57. Three sets of exposures of a steel step wedge resulted in the tables given below, the KV, Film, density and processing were constant in each group.

A.

Volt XKV

B.

YKV

C.

ZKV

T(in) 0.15 0.20 0.25 0.20 0.30 0.40 0.30 0.35 0.45

mAmin 27 50 100 18 45 110 22 30 60

Identity the exposure that used the highest KV. a. b. c. d.

x y z all same kV

58. Three sets of exposures of a steel step wedge resulted in the tables given below, the KV, Film, density and processing were constant in each group. T(in) mAmin 0.15 27 0.20 50 0.25 100 B. YKV 0.20 18 0.30 45 0.40 110 C. ZKV 0.30 22 0.35 30 0.45 60 What is the half value layer thickness of each group? A.

a. b. c. d.

Volt XKV

0.05, 0.08, 0.1 respectively 02, 0.7, 0.35 respectively 0.05, 0.1, 0.15 respectively 0.05, 0.01, 0.7 respectively

Feb 1998

RT LEVEL-III MODEL QUESTION PAPER BY: N.KUPPUSAMY

Sensitometric curve of STRUCTURIX D2 Film 5 minutes development at 20°C

Sensitometric curve of STRUCTURIX D7 Film 5 minutes development at 20°C

4

4 3.8

3.8 3.6

3.6

3.4

3.4

3.2

3.2

3

3

2.8

2.8

2.6

2.6

2.4

2.4 S

2.2

2.2

2

2

1.8

1.8

1.6

1.6

1.4

1.4

1.2

1.2

1

1

0.8

0.8

0.6

0.6

0.4

0.4

0.2

0.2

0

S

0

1

2

1.0

3

4

2.0

5

3.0 6

7 of 8

1

2

2.0

3

4

Feb 1998

3.0

5

6 4.0

RT LEVEL-III MODEL QUESTION PAPER BY: N.KUPPUSAMY

RT Level-III Model Exam Answers 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20.

c b d b c d c c a d d e c b e e c a c e

21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40.

a b d b d a c b a e b a b b a c d c c b

41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60.

e d c b b c c c c d c c b b c b c a c b

61. 62. 63. 64. 65. 66. 67. 68. 69. 70. 71. 72. 73. 74. 75. 76. 77. 78. 79. 80.

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d a b c d b a c a b d a c a d b a c c b

81. 82. 83. 84. 85. 86. 87. 88. 89. 90. 91. 92. 93. 94. 95. 96. 97. 98. 99. 100.

b d c d c d a b a d a c d e a c b a c b

101. 102. 103. 104. 105. 106. 107. 108. 109. 110. 111. 112. 113. 114. 115. 116. 117. 118. 119. 120.

c c c b c d a a b e c b d c a b d c c c

121. 122. 123. 124. 125. 126. 127. 128. 129. 130. 131. 132. 133. 134. 135.

Feb 1998

b b e e c e b b a b a b c d d