Physics

Question 1

What is the role of the anode in an x-ray tube?

Answer 1

Produces the focal spot.

Question 2

What happens to photon energy when kVp increases?

Answer 2

Photon energy increases.

Question 3

What does mAs control?

Answer 3

Beam quantity.

Question 4

What does the half value layer measure?

Answer 4

Beam attenuation per thickness.

Question 5

What is the purpose of a grid?

Answer 5

Reduces scatter.

Question 6

What does a higher grid ratio do?

Answer 6

Removes more scatter.

Question 7

What does focal spot size affect?

Answer 7

Spatial resolution.

Question 8

What happens when SID increases?

Answer 8

Geometric unsharpness decreases.

Question 9

What law describes beam intensity with distance?

Answer 9

Inverse square law.

Question 10

What is the purpose of filtration?

Answer 10

Removes low energy photons.

Question 11

What dose index is used in CT?

Answer 11

DLP.

Question 12

What is the unit of effective dose?

Answer 12

Sievert.

Question 13

What is the unit of entrance surface dose?

Answer 13

Gray.

Question 14

What does ALARA mean?

Answer 14

As low as reasonably achievable.

Question 15

When is gonadal shielding used?

Answer 15

When in primary beam and not obscuring anatomy.

Question 16

First step if patient is pregnant before x-ray?

Answer 16

Verify pregnancy and justification.

Question 17

Main difference between ionic and nonionic contrast?

Answer 17

Osmolality.

Question 18

First drug for severe contrast reaction?

Answer 18

Epinephrine.

Question 19

What is the MRI risk with ferromagnetic objects?

Answer 19

Projectile effect.

Question 20

What does CT windowing adjust?

Answer 20

Contrast display.

Question 21

What effect does scatter have on image contrast?

Answer 21

Reduces contrast.

Question 22

Radiographic density refers to what?

Answer 22

Film blackening.

Question 23

What is DICOM used for?

Answer 23

Image storage and communication.

Question 24

What is the function of PACS?

Answer 24

Archive and retrieve images.

Question 25

What is the purpose of collimation?

Answer 25

Reduce patient dose and scatter.

Question 26

Beam hardening artifact occurs near what?

Answer 26

Dense bone and metal.

Question 27

Who sets radiation protection rules?

Answer 27

National radiation regulator.

Question 28

Posterior to anterior projection is called?

Answer 28

PA.

Question 29

What does grid cutoff cause?

Answer 29

Uneven exposure and loss of density.

Question 30

Typical pulsed fluoroscopy frame rate?

Answer 30

7.5 to 30 fps.

Question 31

Types of image receptors?

Answer 31

CR, DR, and film-screen.

Question 32

Function of AEC?

Answer 32

Terminates exposure when receptor signal is reached.

Question 33

Ultrasound contrast agents are?

Answer 33

Microbubbles.

Question 34

Dosimeter badge measures what?

Answer 34

Cumulative occupational dose.

Question 35

Primary barrier design depends on?

Answer 35

Workload, use factor, occupancy factor.

Question 36

What causes magnification in radiography?

Answer 36

Larger object-image distance (OID).

Question 37

What does an increase in HVL indicate?

Answer 37

Harder beam.

Question 38

When should staff use thyroid shields?

Answer 38

During fluoroscopy near the beam.

Question 39

QC tests for x-ray generator include?

Answer 39

kVp and timer accuracy.

Question 40

Main focus in pediatric imaging?

Answer 40

Dose reduction, optimized technique, justification.

Question 41

What is the main source of x-rays in diagnostic tubes?

Answer 41

Bremsstrahlung radiation.

Question 42

What produces characteristic radiation?

Answer 42

Ejection of inner shell electrons.

Question 43

Common anode target material?

Answer 43

Tungsten.

Question 44

Heel effect causes what?

Answer 44

Lower intensity on anode side.

Question 45

Effect of increasing filtration?

Answer 45

Reduces patient skin dose.

Question 46

High kVp produces what contrast?

Answer 46

Low contrast.

Question 47

Low kVp produces what contrast?

Answer 47

High contrast.

Question 48

Shorter exposure time reduces what?

Answer 48

Motion blur.

Question 49

Increasing mAs affects image noise how?

Answer 49

Reduces image noise.

Question 50

What causes quantum mottle?

Answer 50

Too few x-ray photons.

Question 51

When does photoelectric effect dominate?

Answer 51

Low photon energy, high atomic number.

Question 52

When does Compton effect dominate?

Answer 52

High photon energy, soft tissue.

Question 53

Threshold energy for pair production?

Answer 53

Above 1.02 MeV.

Question 54

What energy are PET photons?

Answer 54

511 keV.

Question 55

What type of isotopes does SPECT use?

Answer 55

Gamma-emitting isotopes.

Question 56

Tc-99m emits what energy?

Answer 56

140 keV gamma rays.

Question 57

Which isotope is used for thyroid therapy?

Answer 57

Iodine-131.

Question 58

Common MRI contrast agent?

Answer 58

Gadolinium.

Question 59

On T1 MRI, what is bright?

Answer 59

Fat.

Question 60

On T2 MRI, what is bright?

Answer 60

Fluid.

Question 61

What does DWI MRI detect?

Answer 61

Restricted diffusion in acute stroke.

Question 62

What do ultrasound probes use?

Answer 62

Piezoelectric crystals.

Question 63

What does Doppler ultrasound measure?

Answer 63

Frequency shift from moving blood.

Question 64

How does ultrasound attenuation change with frequency?

Answer 64

It increases.

Question 65

Lower ultrasound frequency penetrates how?

Answer 65

Deeper.

Question 66

CT pitch >1 effect?

Answer 66

Reduces dose per rotation.

Question 67

CT pitch <1 effect?

Answer 67

Increases dose per rotation.

Question 68

What is multidetector CT?

Answer 68

Uses multiple rows of detectors.

Question 69

What reduces CT dose?

Answer 69

Iterative reconstruction.

Question 70

What does dual-energy CT differentiate?

Answer 70

Materials by attenuation at two kVp values.

Question 71

What does effective dose account for?

Answer 71

Tissue weighting factors.

Question 72

Unit of organ dose?

Answer 72

Gray.

Question 73

Whole-body occupational dose limit EU?

Answer 73

20 mSv/year averaged over 5 years.

Question 74

Lens of eye dose limit?

Answer 74

20 mSv/year.

Question 75

Extremity occupational dose limit?

Answer 75

500 mSv/year.

Question 76

In CT, what reduces dose most?

Answer 76

Collimation and optimization.

Question 77

Where should staff wear dosimeter badge?

Answer 77

Chest outside lead apron.

Question 78

Second badge worn where?

Answer 78

Under the apron.

Question 79

Lead apron 0.5 mm attenuates what % of scatter?

Answer 79

Over 90%.

Question 80

Most effective way to reduce staff exposure?

Answer 80

Increase distance.

Question 81

Controlled area access is limited to?

Answer 81

Radiation workers.

Question 82

Max leakage radiation from tube at 1 m?

Answer 82

1 mGy/h.

Question 83

Barrier dose design for controlled area?

Answer 83

6 mSv/year.

Question 84

Barrier dose design for uncontrolled area?

Answer 84

1 mSv/year.

Question 85

CT dose descriptors?

Answer 85

CTDIvol and DLP.

Question 86

Fluoroscopy dose metric?

Answer 86

Air kerma at reference point.

Question 87

Nuclear medicine dose unit?

Answer 87

Becquerel.

Question 88

1 curie equals?

Answer 88

3.7 × 10^10 Bq.

Question 89

Largest natural radiation source?

Answer 89

Radon.

Question 90

Cosmic radiation exposure increases with?

Answer 90

Altitude.

Question 91

Max fetal dose after declaration?

Answer 91

1 mSv.

Question 92

What does lead apron not protect against?

Answer 92

Primary beam.

Question 93

What is more effective than mobile shields?

Answer 93

Fixed barriers.

Question 94

PPE should be combined with what?

Answer 94

Time and distance optimization.

Question 95

DAP reflects what?

Answer 95

Dose and irradiated field size.

Question 96

Where is entrance skin dose highest?

Answer 96

Fluoroscopy.

Question 97

Effective dose combines what?

Answer 97

Equivalent dose with tissue weighting.

Question 98

What type of effect has no threshold?

Answer 98

Stochastic.

Question 99

What type of effect has a threshold?

Answer 99

Deterministic.

Question 100

Threshold for radiation skin erythema?

Answer 100

About 2 Gy.