Chapter 6 radiographic imaging and exposure
without exposure technique compensation, increasing the OID by 4 inches for a knee film image would 1) increase magnification 2) decrease exposure to IR 3) increase contrast a) 1 and 2 only b) 1 and 3 only c) 2 and 3 only d) 1,2,3
1,2,3
a quality image is produced using 70 kVp and 25 mAs at a 40 in SID. What calculated change in the exposure technique is necessary to maintain radiation exposure to the IR when the SID is increased to 56 in? a) 60 kVp at 25 mAs b) 70 kVp at 12.5 mAs c) 70 kVp at 50 mAs d) 60 kVp at 50 mAs
70 kVp at 50 mAs note: (mAs1/mAs2) = [ (SID1)2/(SID2)2) --> (25/mAs2) = [(40)2/(56)2] --> mAs2 = [(56)2 x 25]/(40)2 = 49 mAs
a quality image is produced using 80 kVp at 10 mAs with a 6:1 ratio grid. Calculate the change in exposure technique to maintain radiation exposure to the image receptor when changing to a 12:1 ratio grid. a. 80 kVp at 17 mAs b. 68 kVp at 20 mAs c. 80 kVp at 6 mAs d. 92 kVp at 5 mAs
80 kVp at 17 mAs note: (mAs1/mAs2) = (GCF1/GCF2) --> (10/mAs2) = [(6:1)/(12:1)] --> (10/mAs2) = (3/5) --> mAs2 = 17 GCF: grid conversion factor a grid of 6:1 has conversion factor of 3 a grid of 12:1 has conversion factor of 5
The exposure indicator value reflects excessive exposure to the IR. Which of the following is the best for correcting the exposure error? a) decrease kVp by 50% b) increase mAs by 15% c) Decrease mAs by 50% d) decrease mAs by 15%
Decrease mAs by 50%
Which of the following factor does not affect the radiation exposure to the IR? a) collimation b) focal spot size c) compensating filters d) body habitus
Focal spot size
What exposure factor change is recommended to maintain radiation exposure to the IR when increasing the patient thickness by 5 cm? a) double the kVp b) Double the mAs c) Decrease the kVp by 15% d) increase the mAs by 15%
double the mAs
Which of the following would maintain radiation exposure to the IR when the kilovoltage is decreased by 15%? a) increase mAs by 15% b) increase mAs by 50% c) doubling mAs d) halve the mAs
double the mAs
which of the following factors does not affect spatial resolution? a) focal spot size b) SID c) OID d) Grid
grid
Which of the following is accurate regarding the relationship between mA and exposure time to maintain the exposure to the image receptor (IR)? a) direct proportional b) direct c) inverse d) inverse proportional
inverse proportional
What exposure factor affects both the quality and the quantity of x-ray beam? a) kVp b) SID c) mA d) Focal spot size
kVp
Increasing the mAs has ______ effect on brightness displayed in digital imaging. a) direct b) proportional c) an inverse d) no
no
Which of the following is not affected by kilovoltage? a) compton interactions b) spatial resoulation c) subject contrast d) radiation quantity
spatial resoulation
