TG-66 Memorizing information Flashcards

1
Q

How often do you measure CT number accuracy?

A

Daily for CT number of water only
Monthly for 4 to 5 difference materials
Annually for a electron density phantom

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2
Q

Tolerance for daily CT number accuracy

A

0 +- 5 HU

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3
Q

How often do you measure image noise?

A

Daily

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4
Q

In-plane spatial integrity tolerance

A

1 mm

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5
Q

How often do you measure in-plane spatial integrity?

A

Daily for x or y direction

Monthly for both directions

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6
Q

When do you measure field uniformity and for what kVp settings?

A

Monthly - most commonly used kVp

Annually - other used kVp settings

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7
Q

What kVp’s do we use in our clinic?

A

140 kVp for everything

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8
Q

Why do we only use 1 kVp setting for all scans?

A

So we don’t need multiple HU maps for eclipse

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9
Q

Field uniformity tolerance

A

Within +- 5 HU

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10
Q

When are you supposed to measure spatial and contrast resolution?

A

Annually, but we do it monthly as well

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11
Q

Tolerance for spatial and contrast resolution

A

Vendor specification +- 1 visible node on catphan

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12
Q

How often should you measure CT slice width?

A

Monthly

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13
Q

Frequency of patient dose from CT-scan, CTDI measurement

A

Annually

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14
Q

Frequency of table movement and positioning tests

A

Monthly

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15
Q

Frequency of artifact evaluation

A

Monthly

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16
Q

What are some common CT artifacts?

A
Beam hardening (cupping artifact, streak and dark bands, metal artifacts)
Metal artifacts
Ring artifacts
Motion artifacts
Photon starvation
Partial volume averaging
Truncation artifact
17
Q

Bore size of a CT sim

Bore size of a standard CT

A

CT sim: 85 cm

Standard CT: 70 cm

18
Q

Three differences between CT sim and a regular CT

A

Flat couch top
Lasers
Larger bore

19
Q

Why does TG 66 recommend not having a beam interlock for door opening?

A

Interrupting a scan means you need to redo it, resulting in more dose to patient.

Dose to anyone entering room during scan is much lower than dose to patient, so it’s not worth stopping.

Also, additional concerns for contrast scanning