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SECTION 4

[pic]110 Formula Reviews

Write out the formula you need to use for the following.

1. To calculate mAs _______________________________

2. To change from one grid to another __________________________

3. To change screen speeds _________________________________

4. To determine what your field size will be______________________

5. Changes in technique when going from one field size to another___________________

6. To change kV when compensating for density_________________________________

7. To show a noticeable difference in density___________________________________

8. To double your density (without a change in kV)_______________________________

9. To determine you mAs when there is a change in SID___________________________

10. To determine the exposure time when thee is a change in SID____________________

11. To determine the grid ratio________________________________________________

12. To determine how much the image is magnified_______________________________

13. To change from a single phase unit to a three phase unit________________________

14. To change from a three phase unit to a single phase unit________________________

Set the following problems up.

15. What is the mAs when using 200mA @ .20 seconds

16. A technique of 10mAs @70kv works for a particular exam when using a 5:1 grid. What technique changes are needed when using a 12:1 grid?

17. If you are using 70KV @ 10 mAs on a 200 speed screen, what would the mAs be for an 800 speed screen?

18. If you are using 10mAs @ 70 KV on a 14x17, what changes will need to be made for another exposure on an 8x10?

19. Using 10mAs @ 70KV, what change can be made to increase the contrast and still maintain the same density?

20. If you are using 10mAs @ 70KV for an exposure at 40 SID what changes need to be made for another exposure at 58 SID?

Practical Problems

1. A radiograph is made using 90 kVp at 300 mA for 0.035 sec. The quality control technologist asks that you repeat this film using 40% less mAs. What new time would be needed if you are to continue to use the 300 mA station?

2. You radiograph the lumbar spine of an elderly woman and note that she has advanced osteoporosis with substantial calcium loss. The film fails to demonstrate the needed diagnostic information because of the lack of contrast. What change in the technique would you make if you originally used 90 kVp at 150 mAs?

3. You made a cross-table lateral radiograph of a broken femur employing a 6: 1 stationary grid and using 74 kVp at 300 mA for 0.05 sec. The orthopedic physician applies a long leg splint to the patient and requests that you repeat the film. Another technologist has taken the 6:1 grid on a portable and you must use an 8:1 grid for your follow-up film. What new technique would be needed to provide the same radiographic density?

4. You made a portable chest radiograph of a recumbent patient and are now asked to repeat the examination with the patient in the erect position. Your original technique was 86 kVp and 1.6 mAs at a 44-in distance. When you repeat the study in the erect position you will be using a 68-in distance. What new mAs would be needed to obtain equal density?

5. You make an AP abdominal radiograph of a patient who is unable to hold his breath. Because of excessive motion you must repeat the film. Your original technique was 80 kVp at 300 mA for 0.15 sec. How would you change this technique to try to eliminate the motion while maintaining the same density?

6. You made a PA chest radiograph of a patient using 120 kVp at 1.125 mAs. The radiologist requests a repeat PA chest film with the kVp not to exceed 80. What new technique would provide the radiologist with a film of the same density using no more than 80 k\Tp?

7. You are told to increase the density of a radiograph by 50%. Your original technique was 90 kVp at 600 mA for 0.05 sec. What new technique would be used if you were to change only the time, leaving the mA and kVp the same?

8. A radiograph is produced with a 6:1 grid using 70 kVp at 200 mA for 0.03 sec. You are asked to repeat the examination using an 8:1 grid. What new technique would be needed?

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9. A radiograph is produced with an 8:1 grid using 90 kVp at 400 mA for 0.08 sec. You are asked to repeat the examination using a 12:1 grid. What new technique would be needed?

10. A radiograph is produced with a 16:1 grid using 100 kVp at 800 mA for 0.02 sec. You are asked to repeat the examination using a 12:1 grid. What new technique would be needed?

11. A radiograph is produced with a 5:1 grid using 70 kVp at 800 mA for 0.02 sec. You are asked to repeat the examination using a 6:1 grid. What new technique would be needed?

12. A radiograph is produced with a 16:1 grid using 120 kVp at 600 mA for 1/10 sec. You are asked to repeat the examination using only 100 kVp. What new technique would be needed?

13. A radiograph is produced with a 12:1 grid using 100 kVp at 600 mA for 1/ 20 sec. You are asked to repeat the examination using 80 kVp. What new technique would be needed?

14. A radiograph is produced with an 8:1 grid using 80 kVp at 300 mA for 1.5 sec. You are asked to repeat the examination using 100 kVp. What new technique would be needed?

15. A radiograph is produced with a 6:1 grid using 70 kVp at 100 mA for 1/15 sec. You are asked to repeat the examination using 80 kVp. What new technique would be needed?

16. A radiograph is made using 10 mAs and 50-speed (detail) screens. What new mAs would be needed if 100-speed screens were substituted?

17. A radiograph is made using 200-speed screens, and the radiologist requests that you repeat the study using 50-speed (detail;) screens. If your original technique called for 3.5 mAs, what new mAs would be needed?

18. A radiograph made with 200-speed screens must be repeated using 100-speed screens. If your original technique called for 5 mAs, what new mAs would be needed?

19. You are using 10 mAs with 100-speed screens and decide to repeat the study using 200-speed screens to help eliminate motion. What new mAs would be needed?

Calculate the following

mAs

1. 200mA and .05 sec _________

2. 600 mA and 1/5 sec__________

3. 400 mA and .30 sec __________

mA

4. 30 mAs and .2 sec ___________

5. 10 mAs and 1/40 sec__________

6. 8 mAs and 20msec____________

Time

7. 12 mAs and 200 mA___________

8. 8 mAs and 500mA____________

9. 15 mAs and 300 mA___________

Reciprocity

10. 200 mA and .12 sec_____________

11. Calculate another mA and time that will equal the same mAs calculated in problem 10.______________

Density Maintance Formaula

New mAs Old mAs New SID Old SID

12. ________ 6 72 40

13. ________ 14 56 48

14. ________ 22 40 66

The 15% Rule

New kVp New mAs Old mAs Old kVp

15. ________ 15 30 68

16. ________ 40 20 75

17. 65 ________ 12 75

18. 90 ________ 6 80

Grid Ratio

New mAs Old mAs Old Grid Ratio New Grid Ratio

19. ________ 20 6:1 16:1

20. ________ 14 12:1 5:1

21. ________ 8 16:1 8:1

22. ________ 24 5:1 8:1

Collimation Field Size

New mAs Old mAs Old Field Size New Field Size

23. _________ 10 8x10 10x12

24. _________ 6 14x17 8x10

25. _________ 22 10x12 14x17

Screen Conversion

New mAs Old mAs Old screen New screen

26. ________ 5 200 400

27. ________ 16 500 300

28. ________ 22 600 100

Xray Generation

New mAs Old mAs Old Generator New Generator

29. ________ 6 single phase three phase

30. ________ 4.5 three phase single phase

Multiple Conversion Problems

1. Which of the following exposure would produce the greatest density?

|A |B |C |D |

|100 mA |200 mA |200mA |300mA |

|¾ sec |2 sec |½ sec |1 sec |

|80 kVp |70 kVp |80 kVp |70 kVp |

|40 SID |72 SID |42 SID |36 SID |

2. Which of the following exposure would produce the greatest density?

|A |B |C |D |

|200 mA |500 mA |500mA |400mA |

|.4sec |.12 sec |.25 sec |.3 sec |

|72 SID |60 SID |72 SID |64 SID |

|6:1 grid |8:1 grid |16:1 grid |12:1 grid |

3. Which of the following exposure would produce the least density?

|A |B |C |D |

|300 mA |400 mA |1000 mA |800 mA |

|40 msec |30 msec |10 msec |20 msec |

|70kVP |80kVP |80kVP |60kVP |

|50 RSV |100 RSV |200 RSV |100 RSV |

|Three phase |Single phase |Three phase |Single phase |

4. Which of the following exposure would produce the greatest density?

|A |B |C |D |

|500 mA |500 mA |100 mA |200 mA |

|.2 sec |.1 sec |1 sec |1 sec |

|90 kVP |80 kVP |80 kVP |90 kVP |

|12:1 grid |16:1 grid |16:1 grid |8:1 grid |

|40 SID |48 SID |36 SID |72 SID |

5. Which of the following exposure would produce the greatest density?

|A |B |C |D |

|100 mA |200 mA |400 mA |500 mA |

|½ sec |¼ sec |1/8 sec |1/10 sec |

|48 SID |36 SID |40 SID |62 SID |

|80 kVp |80 kVp |70 kVp |80 kVp |

|12:1 grid |12:1 grid |16:1 grid |8:1 grid |

|100 RSV |100 RSV |50 RSV |200 RSV |

6. Which of the following exposure would produce the least density?

|A |B |C |D |

|400 mA |300 mA |200 mA |500 mA |

|40 msec |60 msec |30 msec |10 msec |

|70kVp |80kVp |90kVp |80kVp |

|36 SID |54 SID |48 SID |68 SID |

|100 RSV |500 RSV |100 RSV |400 RSV |

| | | | |

7. Which of the following exposure would produce the least density?

|A |B |C |D |

|200 mA |300 mA |50 mA |200 mA |

|½ sec |1/6 sec |1 sec |1/8 sec |

|70kVp |80kVp |70kVp |80kVp |

|40 SID |50 SID |40 SID |60 SID |

|Single phase |Three phase |Single phase |Three phase |

8. Which of the following exposure would produce the greatest density?

|A |B |C |D |

|1000 mA |100 mA |800 mA |400 mA |

|.1 sec |.5 sec |.1 sec |.25 sec |

|90 kVp |104 kVp |80 kVp |80 kVp |

|12:1 grid |16:1 grid |8:1 grid |8:1 grid |

|14 x 17 collimation |8 x 10 collimation |10 x 12 collimation |14 x 17 collimation |

9. Which of the following exposure would produce the greatest density?

|A |B |C |D |

|500 mA |600 mA |400 mA |500 mA |

|.05 sec |.03 sec |.015 sec |.01 sec |

|70 kVp |80 kVp |90 kVp |80 kVp |

|40 SID |50 SID |48 SID |72 SID |

|100 RSV |200 RSV |600 RSV |400 RSV |

10. Which of the following exposure would produce the greatest density?

|A |B |C |D |

|200 mA |100 mA |500 mA |600 mA |

|3/10 sec |½ sec |3/10 sec |2/10 sec |

|80 kVp |90 kVp |80 kVp |105 kVp |

|8:1 grid |6:1 grid |16:1 grid |8:1 grid |

|40 SID |50 SID |36 SID |72 SID |

11. Which of the following exposure would produce the greatest density?

|A |B |C |D |

|400 mA |300 mA |600 mA |500 mA |

|.05 sec |.07 sec |.02 sec |.03 sec |

|70 kVp |90 kVp |80 kVp |70 kVp |

|5:1 grid |12:1 grid |8:1 grid |16:1 grid |

|14 x 17 collimation |10 x 12 collimation |14 x 17 collimation |10 x 12 collimation |

12. Which of the following exposure would produce the greatest density?

|A |B |C |D |

|200 mA |100 mA |300 mA |100 mA |

|½ sec |2/10 sec |2/15 sec |3/5 sec |

|70 kVp |80 kVp |90 kVp |70 kVp |

|40 SID |72 SID |54 SID |62 SID |

|100 RSV |50RSV |200 RSV |400 RSV |

Calculate the new mAs, mA or time required for column B

A B

|1 |200 mA |500 mA |

| |½ sec |_______sec |

| |6:1 grid |12:1 grid |

| |30 SID |40 SID |

|2 |400 mA |________ mA |

| |.04 sec |.02 sec |

| |64 kVp |74 kVp |

| |100 RSV |200 RSV |

|3 |400 mA |200mA |

| |.02 sec |_________sec |

| |65 SID |45 SID |

| |200 RSV |100RSV |

| |single phase |three phase |

|4 |600mA |__________mA |

| |1/15 sec |1/20 sec |

| |75 kVp |85 kVp |

| |56 SID |40 SID |

| |6:1 Grid |16:1 grid |

|5 |20mAs |_________mAs |

| |40 SID |48 SID |

| |80 kVp |70 kVp |

| |8:1 grid |6:1 grid |

| |8x10 collimation |10 x 12 collimation |

|6 |400 mA |500mA |

| |¼ sec |_________sec |

| |80 kVp |70 kVp |

| |16:1 grid |6:1 grid |

| |100 RSV |400 RSV |

|7 |100 mAs |__________mAs |

| |70 kVp |80 kVp |

| |14x17 collimation |10x12 collimation |

| |72 SID |44 SID |

| |Three phase |single phase |

|8 |100 mAs |__________ mAs |

| |8:1 grid |12:1 grid |

| |200 RSV |500 RSV |

| |40 SID |72 SID |

|9 |100 mAs |100 mAs |

| |.3 seconds |_________ seconds |

| |40 SID |72 SID |

| |60 kVp |70 kVp |

| |12:1 grid |6:1 grid |

|10 |50 mA |_____________ mA |

| |.10 seconds |.4 seconds |

| |54 kVp |62 kVp |

| |400 RSV |50 RSV |

| |14x17 collimation |8x10 collimation |

"CHECKLIST"-TYPE QUESTIONS

There will be many of these questions asked in the Image Production and Evaluation section and possibly in the Radiation Protection section. Because these can be very time-consuming, it is important to establish a strategy for tackling these types of questions.

Here is an example:

I. Which of the following sets of technical factors would provide the greatest radiographic density?

mA Time kVp Screen Speed Grid Ratio

A. 400 200 ms 90 200 12:1

B. 300 500 ms 70 400 8:1

C. 800 100 ms 80 100 10:1

D. 600 300 ms 80 200 6:1

Questions like these are extremely challenging because they combine an abundance of information in a single question. Thus, they are an easy way for the certification or licensure agency to establish your overall knowledge of a particular aspect of radiographic quality and factors affecting it such as density, contrast, and image blur.

First ask, "What is this question asking?" Well, it is asking the result of a variety of technical factors and their influence on radiographic density. Radiographic density is affected by all of the factors listed in the previous question, requiring you to put your knowledge of all of these aspects together to solve the problem (knowledge of screens, grids, milliamperes, and kilovolt [peaks]).

NOTE: Sometimes, these questions will include factors that have no influence on the elements in question. For instance, a question dealing with the effect of geometric blur on an image may throw in the factors of milliampere and kilovolt (peak) along with the factors most affecting blur, which include SID, object-image receptor-distance (OlD), and focal spot size. Be careful not to include the erroneous factors.

Assuming you already possess the knowledge to solve this problem, a fast and easy way to do this is as follows:

1. First solve for milliamperes (mA X time)

2. Next assign a number to each factor in the list according to its effect on density. For example, if there are four different milliampere settings for the four choices, assign a 1 to the milliampereseconds that would create the least radiographic density and a 4 to the milliampere seconds that would create the greatest radiographic density. Do this for each of the factors listed that affect radiographic density.

3. Finally, add up all of the numbers from each factor for each item across the row. The item with the highest sum will be the radiograph with the greatest density.

Here is an example using this question:

Which of the following sets of technical factors would provide the film with the greatest radiographic density?

Screen Grid

mA Time mAs kVp Speed Ratio

A. 400 200ms 801 903 2002 12:11

B. 300 500ms 1502 701 4003 8:12

C. 800 100ms 801 802 1001 10:11

D. 600 300ms 1803 802 2002 6:13

The answer would be D using this method because it contains the highest sum from each of the contributing factors (A = 7, B = 8, C = 5, D= 10).

Bear in mind that this method has been found to be correct only 75 percent of the time. Therefore, you may have to find the answer the long way by using all of the radiographic quality rules that were learned (15 percent rule, new grid and old grid, old screen and new screen, etc.). You will feel much more relaxed knowing that you can spend very little time on each of these questions and still be confident choosing the correct answer.

If there is time at the end of the examination, it would not hurt to go back and recheck the answers to ensure that each has been calculated correctly. It is easy to get confused using the shortened method because you may have inadvertently assigned a "1" to one contributing factor and a "4" to another, both of which will have the greatest effect on density. Be careful not to do this. If this method does not work, stick to a method that does. Whatever method used, just remember to practice and practice solving these questions and they will become easier.

1. Which of the following will produce the greatest density?_______________

| |MA |Seconds |SID |

|A |400 |.075 |72 |

|B |200 |.075 |36 |

|C |200 |.150 |72 |

|D |400 | .150 |72 |

2. Which will produce the least density______

| |MA |SID |

|A |400 |72 |

|B |200 |36 |

|C |50 |36 |

|D |400 |72 |

3. Which will produce the longest scale

of contrast?_____

| |MA |kVp |Screen Speed |Grid |Field Size |

|B |12 |90 |200 |8:1 |14x17 |

|C |15 |60 |200 |12:1 |8x10 |

|D |20 |80 |400 |10:1 |11X14 |

4. the shortest scale contrast?___________

| |MA |kVp |Screen Speed |Grid |Field Size |

|B |12 |90 |200 |8:1 |14x17 |

|C |15 |60 |200 |12:1 |8x10 |

|D |20 |80 |400 |10:1 |11X14 |

5. Of the following groups of, which will produce the shortest scale of contrast?____

| |MA |Seconds |kVp |

|A |500 |.040 |70 |

|B |100 |.1 |80 |

|C |800 |.25 |92 |

|D |700 |.014 |80 |

6. the longest scale__________

| |MA |Seconds |kVp |

|A |500 |.040 |70 |

|B |100 |.1 |80 |

|C |800 |.25 |92 |

|D |700 |.014 |80 |

7. The greatest density________

| |MA |Seconds |kVp |

|A |500 |.040 |70 |

|B |100 |.1 |80 |

|C |800 |.25 |92 |

|D |700 |.014 |80 |

8. Which of the following will produce the greatest radiographic density?____________

| |MA |Seconds |kVp |Screen Speed |

|A |400 |.01 |94 |200 |

|B |500 |.008 |94 |100 |

|C |200 |.040 |94 |200 |

|D |100 | .02 |80 |200 |

9. Which of the following will produce the

least density________

| |MA |seconds |kVp |Screen Speed |

|A |400 |.01 |94 |200 |

|B |500 |.008 |94 |200 |

|C |200 |.040 |94 |50 |

|D |100 | .02 |80 |200 |

10. the highest contrast_________

| |MA |seconds |kVp |Screen Speed |

|A |400 |.01 |94 |200 |

|B |500 |.008 |94 |200 |

|C |200 |.040 |94 |50 |

|D |100 | .02 |80 |200 |

11. Which of the following will produce the longest scale of contrast?

| |MA |Seconds |kVp |Grid |

|A |200 |.08 |95 |12:1 |

|B |500 |.03 |81 |8:1 |

|C |300 |.05 |95 |8:1 |

|D |600 |1/40 |70 |6:1 |

12. The shortest scale contrast___________

| |MA |Seconds |kVp |Grid |

|A |200 |.08 |95 |12:1 |

|B |500 |.03 |50 |none |

|C |300 |.05 |95 |8:1 |

|D |600 |1/40 |70 |6:1 |

13. The most density_______________

| |MA |Seconds |kVp |Grid |

|A |200 |.08 |95 |12:1 |

|B |500 |.03 |81 |8:1 |

|C |300 |.05 |95 |8:1 |

|D |600 |1/40 |70 |6:1 |

14. Which of the following will produce the

greatest detail?________

| |mAs |kVp |Screen Speed |Grid |Field Size |SID |

|B |12 |90 |200 |8:1 |14x17 |72 |

|C |15 |90 |200 |12:1 |8x10 |56 |

|D |20 |80 |400 |10:1 |14x17 |36 |

15. The least detail_____________

| |mAs |kVp |Screen Speed |Grid |Field Size |SID |

|B |12 |90 |200 |8:1 |14x17 |72 |

|C |15 |90 |200 |12:1 |8x10 |56 |

|D |20 |80 |400 |10:1 |14x17 |36 |

16. The most density____________

| |mAs |kVp |Screen Speed |Grid |Field Size |SID |

|B |12 |90 |200 |8:1 |14x17 |72 |

|C |15 |90 |200 |12:1 |8x10 |56 |

|D |20 |80 |400 |10:1 |11x14 |36 |

17. The highest contrast_________

| |mAs |kVp |Screen Speed |Grid |Field Size |SID |

|B |12 |90 |200 |8:1 |14x17 |72 |

|C |15 |90 |200 |12:1 |8x10 |56 |

|D |20 |80 |400 |10:1 |11x14 |36 |

18. The least contrast___________

| |mAs |kVp |Screen Speed |Grid |Field Size |

|B |12 |90 |200 |8:1 |14x17 |

|C |15 |90 |200 |12:1 |8x10 |

|D |20 |80 |600 |10:1 |11x14 |

19. the most density____________

| |mAs |kVp |Screen Speed |Grid |Field Size |

|B |12 |90 |200 |8:1 |14x17 |

|C |15 |90 |200 |12:1 |8x10 |

|D |20 |80 |600 |10:1 |11x14 |

20. Which of the following will produce the

greatest detail?________

| |mA |second |SID |F/S |Grid |

|B |200 |.075 |36 |100 |6:1 |

|C |200 |.150 |36 |400 |5:1 |

|D |400 |.150 |72 |1000 |12:1 |

21. The most density__________

| |mA |second |SID |F/S |Grid |

|B |200 |.075 |36 |100 |6:1 |

|C |200 |.150 |36 |400 |5:1 |

|D |400 |.150 |72 |1000 |12:1 |

22 . Which of the following will produce the

greatest detail?_____________

| |mA |second |kV |F/S |SID |Focal Spot |

|B |500 |.008 |94 |200 |40 |1.2 |

|C |200 |.04 |94 |50 |72 |.3 |

|D |100 |.02 |80 |200 |72 |1.0 |

23. The least density_______________

| |mA |second |kV |F/S |SID |Focal Spot |

|B |500 |.008 |94 |200 |40 |1.2 |

|C |200 |.04 |94 |50 |72 |.3 |

|D |100 |.02 |80 |200 |72 |1.0 |

24. The highest contrast______________

| |mA |second |kV |F/S |SID |Focal Spot |

|B |500 |.008 |94 |200 |40 |1.2 |

|C |200 |.04 |94 |50 |72 |.3 |

|D |100 |.02 |80 |200 |72 |1.0 |

25. Which will produce the longest scale of contrast?

|mAs|kV |F/S |grid |Field size |OID |Filter | |

|B |12 |90 |200 |8:1 |14x17 |0in |2.0mm |

|C |15 |90 |200 |12:1 |8x10 |5in |.8mm |

|D |20 |80 |400 |10:1 |11x14 |1in |1.2mm |

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