CT FINAL EXAM QUESTIONS AND ANSWERS

CT FINAL EXAM QUESTIONS AND ANSWERS
CT technologists must understand both the ___________ & ___________ of examinations and take
steps to maximize the ________ & minimize the ____________. - CORRECT ANSWER✅✅risks &
benefits

positive, negative



What are the two components regarding radiation dose to the patient? - CORRECT ANSWER✅✅1)
appropriate patient selection

2)minumizing the dose to the pt w/ out compromising the diagnostic image quality



CT scans provide one of the ____________ radiation doses in diagnostic radiology. *** (slide 3) -
CORRECT ANSWER✅✅higher

--large # w/ very thin slices



X-rays damage cells in _______ ways.....how? - CORRECT ANSWER✅✅2; 1) Direct interaction between
an x-ray photon and DNA bonds with the nucleus of the cell within the patient. 2) X-ray photon
indirectly produces ion pairs in tissues as it passes through the body



X-rays damage cells in two ways: - CORRECT ANSWER✅✅-Direct interaction with DNA bonds.

-Indirect effect caused by ionization of chemicals in the body.



Direct Interaction is also known as.... - CORRECT ANSWER✅✅Target Theory



Gestating babies are ________ radiosensitive. - CORRECT ANSWER✅✅most



Radiation effects may be __________ but are more likely to be seen___________________ . - CORRECT
ANSWER✅✅-immediate

-over a long period of time



What are the effects of x-ray radiation?(4) - CORRECT ANSWER✅✅-cancer

,-genetic effects of future generations

-Long term effects (10-20 yrs)

-effects of the embryo & fetus

--first trimester=maximum radiosensitivity



The unit of x-ray exposure in air - CORRECT ANSWER✅✅Roentgen (R)



Units of absorbed dose - CORRECT ANSWER✅✅radiation absorbed dose=rad

SI unit=Gray(Gy)

100 rad=1 Gy

1 rad= .01 Gy or 1 cGy



Convert the following:

50 rad =

200 Gy =

.1 rad = - CORRECT ANSWER✅✅.5 Gy

20,000 rad

.001 Gy or 1mGy



Determine the total dose in Gy if an exam acquires

300 slices producing 2 rads per slice. - CORRECT ANSWER✅✅300 slices x 2 rad/slice = 600 rad x .01 = 6
Gy



Accounts for different types of ionizing radiation - CORRECT ANSWER✅✅Quality factor (Q)



In CT, the quality factor is ? - CORRECT ANSWER✅✅1



Attempts to account for the effects particular to the patient's tissue that has absorbed the radiation
dose - CORRECT ANSWER✅✅Effective dose

, Effective dose attempts to quantify dose based upon the_________________ of certain tissues or
organs. - CORRECT ANSWER✅✅radiosensitivity



The uniformity of the dose __________ as the SFOV and patient thickness ___________. - CORRECT
ANSWER✅✅decreases

increase



organ doses are higher for children (or small adults) compared with (larger) adults - CORRECT
ANSWER✅✅........



Body scans are________uniform than head scans - CORRECT ANSWER✅✅less



The central dose of a body scan is approximately one third - one half that of the peripheral dose -
CORRECT ANSWER✅✅.......



Z axis dose distribution profile describes variations that occur along the________________? - CORRECT
ANSWER✅✅length of the patient



-Total dose is from the radiation to the selected slice and from scatter radiation, or "tails," from
neighboring slices

-In general, the tails will contribute approximately 25% to 40% to the total dose - CORRECT
ANSWER✅✅.......



Multiple scan average dose (MSAD) - CORRECT ANSWER✅✅Dose calculated from multiple scans



Computed tomography dose index (CTDI) - CORRECT ANSWER✅✅Reported to FDA

Slices must be contiguous



CTDIw - CORRECT ANSWER✅✅Weighted average

The weighted CTDI takes into account patient size and mAs used.