Principles of Radiation Use, Protection, and Basic Physics Concepts

Question 1

What is the MATRIX trial?

Answer 1

A large-scale randomized controlled trial comparing radial and femoral access in 8,404 ACS patients

Question 2

What was the risk ratio for all-cause mortality favoring radial access found in the meta-analysis following the MATRIX trial?

Answer 2

0.72 (95% CI 0.60 to 0.88; p = 0.0011)

Question 3

What is the purpose of digital subtraction angiography?

Answer 3

To subtract a non–contrast-filled (mask) image from a contrast-filled (live) image

Question 4

True or False: Subtraction studies require a lower dose of radiation compared to cardiac cine frames.

Answer 4

False

Question 5

What are the main sources of radiation exposure during interventional procedures?

Answer 5

Scatter radiation and primary beam exposure

Question 6

What is the FDA limit for maximum exposure rate for diagnostic fluoroscopy?

Answer 6

88 mGy per minute (10 R per minute)

Question 7

What is quantum mottle?

Answer 7

The background granularity of the image due to random variation in x-ray photon distribution

Question 8

Fill in the blank: An increase in filament current (mA) _______ the number of x-ray photons produced.

Answer 8

increases

Question 9

How does collimation affect radiation exposure?

Answer 9

Reduces exposure for everyone in the room

Question 10

What is photoelectric absorption?

Answer 10

A sudden jump in absorption when incident photon energy exceeds the binding energy of an electron

It is a significant source of tissue attenuation in the diagnostic range.

Question 11

What are the two categories of radiation exposure-associated risks?

Answer 11

Stochastic and deterministic (tissue reactions)

-Stochastic risks are associated with cancer risk
-deterministic risks involve tissue reactions

Question 12

True or False: Most x-ray-induced DNA damage results from direct structure alteration.

Answer 12

False

About two-thirds of cases result from free radical formation (indirect damage).

Question 13

What does DAP stand for in radiation exposure metrics?

Answer 13

Dose Area Product

It is the product of air KERMA and the beam cross-sectional area.

Question 14

What is the typical effective dose (ED) for a coronary angiography?

Answer 14

7 mSv

This exposure is significant compared to other diagnostic procedures.

Question 15

What does DAP stand for in radiology?

Answer 15

Dose Area Product

DAP is also known as kerma-area product and is the product of the air KERMA and the beam cross-sectional area.

Question 16

How does collimation affect radiation exposure?

Answer 16

Reduces beam area, DAP, total patient dose, and room exposure

Collimation is a technique used to limit the size of the x-ray beam.

Question 17

What is the average radiation exposure from standard diagnostic coronary angiography?

Answer 17

About 7 mSv

This exposure is equivalent to 2 to 4 years of natural background exposure.

Question 18

What is the radiation exposure from a single-isotope SPECT?

Answer 18

10 mSv on average

This is equivalent to 10 years of natural background exposure.

Question 19

True or False: Pregnancy is an absolute contraindication to cardiac catheterization procedures.

Answer 19

False

Pregnancy is not an absolute contraindication, but risks must be discussed.

Question 20

What is the guiding principle for radiation safety in medical settings?

Answer 20

ALARA (As Low as Reasonably Achievable)

This principle aims to minimize radiation exposure.

Question 21

What is the difference between stochastic and deterministic effects of radiation?

Answer 21

Stochastic effects are random and can lead to cancer; deterministic effects have a threshold dose and cause immediate cell death

Stochastic effects are unpredictable, while deterministic effects are predictable and preventable.

Question 22

What are the key technical determinants of x-ray exposure?

Answer 22

Table height and detector position

These factors are under the operator’s control and can significantly affect patient dose.

Question 23

The term ‘attenuation’ in radiology refers to what?

Answer 23

The reduction of the intensity of x-ray photons as they pass through tissue

Attenuation is influenced by multiple factors including tissue density and thickness.

Question 24

What is the maximum voltage applied to an x-ray tube indicative of?

Answer 24

The maximum energy of the x-ray photons spectrum produced

For example, a 70 kVp produces x-rays with energies up to 70 keV.

Question 25

What is recommended when exposing a pregnant woman to radiation?

Answer 25

Discuss cancer risk and utilize the smallest amount of radiation needed

Use the ALARA principle and limit the beam to the chest whenever possible.

Question 26

What is the purpose of wearing two dosimeters in a medical setting?

Answer 26

To record accumulated doses of scatter radiation effectively

Ideally, one badge should be worn over the thyroid collar and one under the apron.

Question 27

Fill in the blank: The Roentgen unit has been replaced by the _______.

Answer 27

Sievert

The Sievert is a measure of the biological effect of radiation on the whole body.

Question 28

What is the significance of the K-edge absorption peak at 33.2 keV?

Answer 28

It relates to the transparency of iodine to high-energy photons

This transparency can lead to decreased image contrast in radiological images.

Question 29

What is a common reason for the increased skin entry doses during cardiac fluoroscopy?

Answer 29

Patient obesity

Obesity can lead to higher doses due to increased tissue thickness.

Question 30

What does the term ‘effective dose’ refer to in relation to radiation exposure?

Answer 30

A measure of the risk of cancer from radiation exposure

This risk is cumulative and varies based on patient age and exposure type.

Question 31

What percentage of medical radiation exposure is attributable to cardiovascular imaging?

Answer 31

About 40%

This includes 10% directly attributable to interventional cardiology.

Question 32

What is the purpose of Diagnostic Reference Levels (DRLs)?

Answer 32

To control radiation exposure on a population level

DRLs are typically set to the 75th percentile of dose distribution for a specific center.

Question 33

True or False: All radiation exposure potentially adds to the lifetime risk of developing a malignancy.

Answer 33

True

This cumulative risk is particularly concerning for younger patients.