CT Safety Flashcards Preview

Computed Tomography (CT) > CT Safety > Flashcards

Flashcards in CT Safety Deck (73)
Loading flashcards...
1

"Radiation safety" refers to:

The methods and tools used to protect patients and personnel from ionizing radiation exposure

2

Organizations who set and enforce radiation standards include:

ICRP
NRC
EPA
FDA
OSHA

3

How can x-rays cause damage to the body as it passes through?

Directly interacting with DNA bonds within cells
Producing ion pairs

4

Radiation can cause the most harm during what peak of pregnancy?

First trimester

5

Rad is equal to:

The absorption of 0.01 joules of energy per kilogram of matter

6

Radiation can be measured as:

Rad
Gray (1 Gy = 100 rads)
Rem
Sievert (1 Sv = 100 rem)

7

Radiation dose at the _____ is greater than the dose at the ______ of the body

Skin / Center

8

What is unique about the radiation profile of a single slice?

It is rounded and the radiation actually extends outside of the intended slice

9

"Radiation penumbra" refers to:

The radiation that "leaks" outside of the intended slice thickness

10

Why does a radiation penumbra occurs?

Imperfect collimation of the x-ray beam (not due to service problems, but due to natural CT physics)

11

What are some indicators of radiation dose?

CT Dose Index
MSAD
Dose-length Product
Effective Dose

12

CTDI did not account for what type of scans?

Helical scanning
Cone beam irradiation
Simultaneous acquisition of multiple slices in a single rotation

13

When would a CTDI value be inaccurate?

If adjacent slices overlapped or had gaps

14

Which indicator of radiation penumbra would correct the CTDI on conventional scans?

MSAD

15

Where do we see the radiation penumbra on MDCT slices?

Only the end slices of the volume

16

The DLP accounts for:

Performance of helical scans
Total number of slices
Slice thickness

17

What is unit used to express DLP?

mGy-cm

18

How can you calculate the effective dose?

Multiplying the absorbed dose by a weighting factor assigned to each organ / body region

19

Effective dose is an indication of the :

Overall risk to the patient from radiation

20

What unit is used to express the effective dose?

Sv

21

What scan parameters can inadvertently affect patient dose?

mAs
Anatomical coverage
Slice thickness (single-row detectors)
Table increment
Pitch

22

On a single-row detector, how can you achieve fewer radiation penumbras?

Thicker slices

23

How can you decrease dose to a patient?

Decrease mAs / anatomical coverage
Increase slice thickness / table increment / pitch

24

What about the image quality would be most apparent when decreasing dose to a patient?

Increased noise

25

What scanning techniques can be used to minimize dose to the patients without repeating scans?

Noise reduction algorithms
Iterative reconstruction

26

What kind of material are some of the radiation shielding devices made of?

Lead
Tungsten
Bismuth

27

What is the federal government limit for occupational exposure?

5 rem in a given year
Pregnant workers: < 0.05 rem/month

28

The cumulative dose equivalent (in rem) must not exceed:

The age of the worker (in years)

29

Contrast agents are helpful in clarifying anatomical findings through what kind of mechanism?

Attenuation

30

What components used in CT are referred to as "negative contrast" in rectal administrations?

Air and water