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• Work the problem• Re-read the question to see if you did what it

asked• Do a “quick mental check”

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)?

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)?

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?

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?

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?

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?

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?