Flashcards in CT Safety Deck (73)
"Radiation safety" refers to:
The methods and tools used to protect patients and personnel from ionizing radiation exposure
Organizations who set and enforce radiation standards include:
How can x-rays cause damage to the body as it passes through?
Directly interacting with DNA bonds within cells
Producing ion pairs
Radiation can cause the most harm during what peak of pregnancy?
Rad is equal to:
The absorption of 0.01 joules of energy per kilogram of matter
Radiation can be measured as:
Gray (1 Gy = 100 rads)
Sievert (1 Sv = 100 rem)
Radiation dose at the _____ is greater than the dose at the ______ of the body
Skin / Center
What is unique about the radiation profile of a single slice?
It is rounded and the radiation actually extends outside of the intended slice
"Radiation penumbra" refers to:
The radiation that "leaks" outside of the intended slice thickness
Why does a radiation penumbra occurs?
Imperfect collimation of the x-ray beam (not due to service problems, but due to natural CT physics)
What are some indicators of radiation dose?
CT Dose Index
CTDI did not account for what type of scans?
Cone beam irradiation
Simultaneous acquisition of multiple slices in a single rotation
When would a CTDI value be inaccurate?
If adjacent slices overlapped or had gaps
Which indicator of radiation penumbra would correct the CTDI on conventional scans?
Where do we see the radiation penumbra on MDCT slices?
Only the end slices of the volume
The DLP accounts for:
Performance of helical scans
Total number of slices
What is unit used to express DLP?
How can you calculate the effective dose?
Multiplying the absorbed dose by a weighting factor assigned to each organ / body region
Effective dose is an indication of the :
Overall risk to the patient from radiation
What unit is used to express the effective dose?
What scan parameters can inadvertently affect patient dose?
Slice thickness (single-row detectors)
On a single-row detector, how can you achieve fewer radiation penumbras?
How can you decrease dose to a patient?
Decrease mAs / anatomical coverage
Increase slice thickness / table increment / pitch
What about the image quality would be most apparent when decreasing dose to a patient?
What scanning techniques can be used to minimize dose to the patients without repeating scans?
Noise reduction algorithms
What kind of material are some of the radiation shielding devices made of?
What is the federal government limit for occupational exposure?
5 rem in a given year
Pregnant workers: < 0.05 rem/month
The cumulative dose equivalent (in rem) must not exceed:
The age of the worker (in years)
Contrast agents are helpful in clarifying anatomical findings through what kind of mechanism?