Acquiring an optimal wrist image at 60 kVp and 2.5 mAs, and then using 72 kVp and 5 mAs for the same projection, will result in which of the following?

Acquiring an optimal wrist image at 60 kVp and 2.5 mAs, and then using 72 kVp and 5 mAs for the same projection, will result in which of the following?

• A. quantum mottle
• B. geometric distortion
• C. excessive patient dose
• D. loss of spatial resolution

Answer: (C)

Increasing the exposure factors here changes both beam energy and the amount of radiation entering the patient. The mAs controls how many photons are emitted, and thus how much radiation the patient receives. Doubling the mAs from 2.5 to 5 already raises the entrance skin dose, and although raising kVp from 60 to 72 increases beam energy (which can reduce surface dose per photon and lower image contrast), it does not compensate for the doubled photon quantity. The net effect is a higher patient dose. The other issues described (quantum mottle from too little exposure, geometric distortion from improper geometry, loss of spatial resolution from motion or focal spot size) are not the primary outcomes of this specific technique change.

Increasing the exposure factors here changes both beam energy and the amount of radiation entering the patient. The mAs controls how many photons are emitted, and thus how much radiation the patient receives. Doubling the mAs from 2.5 to 5 already raises the entrance skin dose, and although raising kVp from 60 to 72 increases beam energy (which can reduce surface dose per photon and lower image contrast), it does not compensate for the doubled photon quantity. The net effect is a higher patient dose. The other issues described (quantum mottle from too little exposure, geometric distortion from improper geometry, loss of spatial resolution from motion or focal spot size) are not the primary outcomes of this specific technique change.