Principles of Radiation Use, Protection, and Basic Physics Concepts Flashcards
What is the MATRIX trial?
A large-scale randomized controlled trial comparing radial and femoral access in 8,404 ACS patients
What was the risk ratio for all-cause mortality favoring radial access found in the meta-analysis following the MATRIX trial?
0.72 (95% CI 0.60 to 0.88; p = 0.0011)
What is the purpose of digital subtraction angiography?
To subtract a non–contrast-filled (mask) image from a contrast-filled (live) image
True or False: Subtraction studies require a lower dose of radiation compared to cardiac cine frames.
False
What are the main sources of radiation exposure during interventional procedures?
Scatter radiation and primary beam exposure
What is the FDA limit for maximum exposure rate for diagnostic fluoroscopy?
88 mGy per minute (10 R per minute)
What is quantum mottle?
The background granularity of the image due to random variation in x-ray photon distribution
Fill in the blank: An increase in filament current (mA) _______ the number of x-ray photons produced.
increases
How does collimation affect radiation exposure?
Reduces exposure for everyone in the room
What is photoelectric absorption?
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.
What are the two categories of radiation exposure-associated risks?
Stochastic and deterministic (tissue reactions)
-Stochastic risks are associated with cancer risk
-deterministic risks involve tissue reactions
True or False: Most x-ray-induced DNA damage results from direct structure alteration.
False
About two-thirds of cases result from free radical formation (indirect damage).
What does DAP stand for in radiation exposure metrics?
Dose Area Product
It is the product of air KERMA and the beam cross-sectional area.
What is the typical effective dose (ED) for a coronary angiography?
7 mSv
This exposure is significant compared to other diagnostic procedures.
What does DAP stand for in radiology?
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.
How does collimation affect radiation exposure?
Reduces beam area, DAP, total patient dose, and room exposure
Collimation is a technique used to limit the size of the x-ray beam.
What is the average radiation exposure from standard diagnostic coronary angiography?
About 7 mSv
This exposure is equivalent to 2 to 4 years of natural background exposure.
What is the radiation exposure from a single-isotope SPECT?
10 mSv on average
This is equivalent to 10 years of natural background exposure.
True or False: Pregnancy is an absolute contraindication to cardiac catheterization procedures.
False
Pregnancy is not an absolute contraindication, but risks must be discussed.
What is the guiding principle for radiation safety in medical settings?
ALARA (As Low as Reasonably Achievable)
This principle aims to minimize radiation exposure.
What is the difference between stochastic and deterministic effects of radiation?
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.
What are the key technical determinants of x-ray exposure?
Table height and detector position
These factors are under the operator’s control and can significantly affect patient dose.
The term ‘attenuation’ in radiology refers to what?
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.
What is the maximum voltage applied to an x-ray tube indicative of?
The maximum energy of the x-ray photons spectrum produced
For example, a 70 kVp produces x-rays with energies up to 70 keV.
What is recommended when exposing a pregnant woman to radiation?
Discuss cancer risk and utilize the smallest amount of radiation needed
Use the ALARA principle and limit the beam to the chest whenever possible.
What is the purpose of wearing two dosimeters in a medical setting?
To record accumulated doses of scatter radiation effectively
Ideally, one badge should be worn over the thyroid collar and one under the apron.
Fill in the blank: The Roentgen unit has been replaced by the _______.
Sievert
The Sievert is a measure of the biological effect of radiation on the whole body.
What is the significance of the K-edge absorption peak at 33.2 keV?
It relates to the transparency of iodine to high-energy photons
This transparency can lead to decreased image contrast in radiological images.
What is a common reason for the increased skin entry doses during cardiac fluoroscopy?
Patient obesity
Obesity can lead to higher doses due to increased tissue thickness.
What does the term ‘effective dose’ refer to in relation to radiation exposure?
A measure of the risk of cancer from radiation exposure
This risk is cumulative and varies based on patient age and exposure type.
What percentage of medical radiation exposure is attributable to cardiovascular imaging?
About 40%
This includes 10% directly attributable to interventional cardiology.
What is the purpose of Diagnostic Reference Levels (DRLs)?
To control radiation exposure on a population level
DRLs are typically set to the 75th percentile of dose distribution for a specific center.
True or False: All radiation exposure potentially adds to the lifetime risk of developing a malignancy.
True
This cumulative risk is particularly concerning for younger patients.
