Deck 10: Radiation Dose in Computed Tomography

Question 1

What is the easiest and probably the most accurate method used to report dose?

A) TLD
B) Film dosimeter
C) Ionization chamber
D) Geiger counter

Answer 1

Ionization chamber

Question 2

Each of the following are radiation bioeffect classifications except:

A) stochastic.
B) nonstochastic.
C) coulombs.
D) deterministic.

Answer 2

nonstochastic.

Question 3

What is the term used to describe the instrumentation and methods used to measure patient dose from a CT scanner?

A) CT dosimetry
B) CT absorptiometry
C) Radiation intensity
D) Dose distribution

Answer 3

CT dosimetry

Question 4

Deterministic effects follow a:

A) linear dose.
B) nonlinear dose.
C) threshold dose.
D) nonthreshold dose.

Question 5

What is the dose limit for radiation workers in the United States?

A) 20 mSv/year
B) 50 mSv/year
C) 75 mSv/year
D) 100 mSv/year

Question 6

What term is used to refer to the size and shape of the beam emanating from the X-ray tube and passing through the patient?

A) Fan beam
B) Cone beam
C) Beam geometry
D) Cone geometry

Question 7

What is the term used to describe a ratio of the difference the table travels per revolution to nominal beam collimation?

A) Dose length product (DLP)
B) Pitch
C) Scan ratio
D) Tilt ratio

Question 8

Examples of stochastic effects include each of the following except:

A) cancer.
B) leukemia.
C) hereditary effects.
D) cataracts.

Question 9

What instrument is used to measure the charge removed from the ionization chamber?

A) Absorptometer
B) Thermometer
C) Electrometer
D) Dosimeter

Question 10

What is used to quantify the risk from partial body exposure to that from an equivalent whole-body dose?

A) Quantity effective dose
B) Quantity absorbed dose
C) Absorbed dose
D) Entrance dose

Question 11

What is the unit of the CTDI?

A) gray
B) Roentgen
C) rem
D) seivert

Question 12

What dose-response model is a radiation risk model most favored by radiobiologists in estimating the risk of exposure in radiology?

A) Linear threshold
B) Linear nonthreshold (LNT)
C) Nonlinear threshold
D) Nonlinear nonthreshold

Question 13

What is/are the unit(s) of absorbed dose?

A) Roentgen (R)
B) Gray (Gy)
C) Sievert (Sv)
D) rem

Question 14

Each of the following are types of dosimeters that have previously been used to measure dose in CT except:

A) film dosimeter.
B) electrometer.
C) thermoluminescent dosimeter (TLD).
D) ionization chamber.

Question 15

What dose descriptor is used to describe a measurement of the total amount of exposure for a series of scans?

A) CTDI volume
B) DLP
C) MSAD
D) single-scan peak dose

Question 16

Which of the following are recommended by the CDRH as CT dose descriptors?

A) Multiple-scan average dose (MSAD)
B) Dose profile
C) Single-scan peak dose
D) Nonthreshold dose

Question 17

What was the first dose descriptor to be identified?

A) Dose profile
B) CTDI
C) MSAD
D) Multiscan peak dose

Question 18

What is used to measure exposure?

A) Geiger counter
B) Ionization chamber
C) Detector chamber
D) Scintillation detector

Question 19

What is the unit of exposure?

A) Roentgen (R)
B) Sievert (Sv)
C) Gray (Gy)
D) rad

Question 20

Which classification of factors has a direct influence on image quality but no direct effect on radiation dose in CT?

A) Direct
B) Indirect
C) Proportional
D) Nonproportional

Question 21

Radiation protection principles include all of the following except:

A) justification.
B) optimization.
C) dose limitation.
D) clarification.

Question 22

Each of the following classify as a proper radiation protection action except:

A) decrease exposure time.
B) increase distance.
C) increase shielding.
D) justifying physician orders.

Question 23

What provides the most comprehensive approach to CT dose reduction?

A) Longitudinal tube current module
B) Angular tube current module
C) Angular-longitudinal tube current module
D) Uniform TCM

Question 24

What is the process by which additional rotations before and after the planned length are taken?

A) z-overscanning
B) Doubling scan
C) Tripling scan
D) Over-rotating

Question 25

What term refers to the automatic control of the milliamperage in two directions during data acquisition by specific technical procedures?

A) Automatic tube current modulation (TCM)
B) Automatic exposure control
C) Miscentering
D) Quantum mottling

Question 26

What is a goal of automatic TCM?

A) Increase scan speed
B) Improve patient comfort
C) Control dose to the patient
D) Measure patient size

Question 27

If a technologist decreases slice thickness by a factor of two, he/she would need to increase dose by a factor of ______ to keep noise constant.

A) two
B) four
C) eight
D) sixteen

Question 28

What technical factor determines the penetrating power of the photons coming from the X-ray tube?

A) kVp
B) mA
C) seconds
D) mAs

Question 29

Effective mAs can be described as:

A) effective mAs = kilovolts/pitch.
B) effective mAs = true mAs + pitch.
C) effective mAs = true mAs/pitch.
D) effective mAs = pitch/kilovolts.

Question 30

The radiation quantity exposure refers to the concentration of radiation at a particular point on the patient.

Question 31

If the pitch increases, the dose:

A) decreases.
B) increases.
C) stays the same.
D) pitch and dose are unrelated.

Question 32

Which technique factor determines the quantity of photons (dose) incident on the patient for the duration of the exposure?

A) kV
B) mA
C) seconds
D) mAs

Question 33

What is the purpose of the use of bowtie filters in CT?

A) Increase scan time
B) Increase patient exposure
C) Shape the beam intensity
D) Ensure correct patient centering

Question 34

The principle of _____________ refers to the reduction of the radiation dose while maintaining the required image quality needed for making a diagnosis.

A) as low as reasonably achievable
B) collimation
C) optimization
D) shielding

Question 35

What consideration does effective dose account and weigh?

A) Patient size
B) Tissue radiosensitivities
C) Photon energy
D) Source distance

Question 36

Which registry collects CT exam doses and transmits them to the American College of Radiology (ACR) to provide feedback and compare institutions?

A) Multiple Scan Dose Index
B) Dose Index Registry (DIR)
C) Image Wisely
D) Image Gently®

Question 37

Iterative reconstruction algorithms have proven beneficial in dose reduction in each of these CT exams except:

A) pediatric studies.
B) abdominal examinations.
C) brain perfusion imaging.
D) CT angiography.

Question 38

Which website resource provides essential radiation safety for the pediatric community?

A) CTDI Registry
B) Image Wisely
C) Image Gently®
D) Image Purely

Question 39

What portion of the collimated beam contributes to the patient's radiation dose but does not contribute to the produced image?

A) Direct beam
B) Penumbra
C) Beam width
D) Divergence

Question 40

Which of the following factors of dose cannot be controlled by the technologist?

A) Technique factors
B) X-ray beam collimation
C) Filtration
D) Patient centering

Question 41

The method suggested by the Center for Devices and Radiological Health for CT dose measurement is the pencil ionization chamber.

Question 42

Please match the following units of dose measurement. All answer selections will be used just once.

rem

A)Old unit of effective dose
B)Conventional unit of exposure
C)Old unit of absorbed dose
D)SI unit of effective dose
E)SI unit of absorbed dose

Question 43

Stochastic effects are those effects for which the probability of the effect occurring depends on the dose.

Question 44

Please match the following units of dose measurement. All answer selections will be used just once.

Roentgen

A)Old unit of effective dose
B)Conventional unit of exposure
C)Old unit of absorbed dose
D)SI unit of effective dose
E)SI unit of absorbed dose

Question 45

The old unit of effective dose was the rad.

Question 46

Please match the following units of dose measurement. All answer selections will be used just once.

Gray

A)Old unit of effective dose
B)Conventional unit of exposure
C)Old unit of absorbed dose
D)SI unit of effective dose
E)SI unit of absorbed dose

Question 47

Phantoms are not used for the process of CT dose measurement.

Question 48

Factors directly affecting CT dose cannot be controlled by the technologist.

Question 49

The DLP is directly proportional to the scan length.

Question 50

The CTDI was developed by the U.S. Food and Drug Administration.

Question 51

The measured radiation dose is inversely proportional to the number of detector rows.

Question 52

Please match the following units of dose measurement. All answer selections will be used just once.

Sievert

A)Old unit of effective dose
B)Conventional unit of exposure
C)Old unit of absorbed dose
D)SI unit of effective dose
E)SI unit of absorbed dose

Question 53

Shielding is a radiation protection action specially designed to only protect the patient.

Question 54

Please match the following units of dose measurement. All answer selections will be used just once.

rad

A)Old unit of effective dose
B)Conventional unit of exposure
C)Old unit of absorbed dose
D)SI unit of effective dose
E)SI unit of absorbed dose