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Area Problems

Area Problems. You have 20” of string; figure the square area of: A 5 X 5” square A 4 X 6” rectangle A 6.66 “ X 3.33” X 5.76” right triangle A circle with a periphery of 20” (R= 3.183”). Steps. Draw the DAMN picture! Write the equation Fill in the knowns and unknowns on the picture

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Area Problems

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  1. Area Problems • You have 20” of string; figure the square area of: • A 5 X 5” square • A 4 X 6” rectangle • A 6.66 “ X 3.33” X 5.76” right triangle • A circle with a periphery of 20” (R= 3.183”)

  2. Steps • Draw the DAMN picture! • Write the equation • Fill in the knowns and unknowns on the picture • Work the problem • Re-read the question to see if you did what it asked • Do a “quick mental check”

  3. Problems • If you had collimator settings of 8 X 10” at 40” SID , what would the resultant field size be at 50” SID if NO changes in collimator settings were done (direct proportion)? • If you were in fluoro and standing 24” away from the fluoro tube and received a dose of 20mR, what dose would you receive at 48” (inverse square law)?

  4. More problems • If you were doing a PCXR and used 10 mAs and 80 kVp at an SID of 40”, what distance would receive only 2.5 mAs (inv. sq. law)? • If you had a great technique for a CXR of 115 kVp and 10 mAs at 40: SID, what mAs would you need to use at 80” SID to get the SAME radiographic density (Old mAs/New mAs)?

  5. No more clues! • You did a PCSR yesterday using 10 mAs, 70 kVp @ 40” SID. Today, you can only get a 50” SID. What technique would give you the same radiographic density as yesterday’s? • You received a dose of 10mR/min @ 2Ft. From the fluoro table in 5 minutes. How far away would you need to stand to only receive 2.5 mR in 5 minutes?

  6. Con’t • A man was stabbed with a 4” blade. The blade shows up as 6” long on the image made @40” SID. How far away from the film/receptor is the blade? • You totaled 182 pts. Of 200 possible in this class, what is your percentage of the total pts?

  7. More • You used 100 mA @ 1 sec with 70 kVp, but got motion on the image. What new time can you use to lesson motion if you now use 500 mA? • If you had a great technique @40” SID with 6 mAs/70kVp, but could only get a 50”SID on a follow up, what new mAs would you use?

  8. Ditto • If you were receiving 4 R/min. during fluoro @ 20” from the fluoro table, how far away would you need to stand to only receive 2 R/min? • An x-ray unit puts out 80 mR@ 40” SID. How far away from the same unit with the same factors would receive only 20mR?

  9. Double ditto • A portable machine exposure is 20 mR @ 40” SID. What is the new exposure at 80 SID (w/o technique changes)? • You are using a technique of 20 mAs and 70 kVp. You must double your exposure density, but you have exceeded tube limits. What should you do to be able to make a more dense OD, but NOT exceed tube limits?

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