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Radiation Safety > Dose Measurement in CT (CTBC 23) > Flashcards

Dose Measurement in CT (CTBC 23) Flashcards

1
Q

CTDI

A

Computed Tomography Dose Index

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2
Q

CTDI is calculated using phantoms of what size

A

16cm (head)/32cm (body)

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3
Q

CTDI phantoms are embedded with _______ in order to measure absorbed dose

A

Ionization Chambers

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4
Q

Phantoms scanned numerous times under average patient-scanning-parameters can be used to validate

A

CTDI measurements produced by the scanner

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5
Q

One of many reasons (phantom-related) CTDI is not a direct estimate of patient dose

A

Patients come in more sizes than 16cm/32cm

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6
Q

_______ represents the average dose to any area of the patient in the scan field

A

CTDI (the actual dose to specific tissues can vary significantly: e.g., skin will receive the highest and center will receive much lower)

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7
Q

Unit for CTDI

A

mGy

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8
Q

CTDI is useful for comparing…

A

Radiation output b/w patients (e.g., max mA of 300/Pt A vs max mA of 400/Pt B would display increase from 1st to 2nd Pt)

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9
Q

DLP is useful since CTDI indicates nothing about

A

length of scan

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10
Q

DLP

A

Dose Length Product (CTDI x scan length) measure of radiation output

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11
Q

DLP units

A

mGy-cm

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12
Q

CTDI measure of radiation output is affected by (5+)

A

mA
kVp
Rotation Time
Pitch
Collimation
Etc

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13
Q

Best for evaluating total amount of radiation received by the patient

A

DLP

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14
Q

Best for comparing the technique used between scan

A

CTDI

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15
Q

Best for estimating biological effects of radiation

A

DLP

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16
Q

EfD can be calculated using _______, but not _______

A

DLP, not CTDI

17
Q

ACR reference CTDI level: Adult Head

A

75 mGy

18
Q

ACR reference CTDI level: Adult Abd/Pelv

A

25 mGy

19
Q

ACR reference CTDI level: Adult Chest (non-angio)

A

20 mGy

20
Q

ACR reference CTDI level: Pediatric Head (5yo)

A

40 mGy

21
Q

CTDI and DLP must be recorded for every procedure and every _______ _______ in a retrievable format such as

A

Scan series (within that procedure)
DICOM in PACS

22
Q

Intensity 1/Intensity 2=

A

distance 2^2/distance 1^2

Radiation Safety (4 decks)

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