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Rad Bio > CH.42 > Flashcards

CH.42 Flashcards

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1
Q

The rate of exposure is directly proportional to what?

A

The time exposed

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2
Q

Inverse Square Law does not apply to what?

A

Fluoroscopy

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3
Q

SCatter exposure at 1 meter from the patient is how much exposure to the tech?

A

1/1000th the patients beam exposure

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4
Q

Standing 1 meter away and wearing a lead apron will give how much exposure to the tech?

A

1/10,000th

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5
Q

This curve indicates that the least exposure to personnel is to the side of the table.

A

Iso-Exposure Curve

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6
Q

Radiation exposure to personnel is always the least at what angle to the central ray of the x-ray beam?

A

right angles

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7
Q

Which type of scatter is more intense, Backscatter or forward scatter?

A

Backscatter

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8
Q

This is the amount of radiation a person can receive with no significant somatic or genetic harm, it is for occupational dose only.

A

Dose Limit

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9
Q

95% of the radiographers occupational dose comes from what 2 areas?

A

Fluoroscopy and portables

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10
Q

This is defined as the summed total of the entrance exposure representative of the radiographic procedure.

A

Distributed Skin Exposure

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11
Q

This is the effective occupational dose limit.

A

Annual-50mSv

Cumulative- 10mSv * age

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12
Q

This is the equivalent annual dose for occupational workers lens of the eye dose limit.

A

150 mSv

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13
Q

This is the equivalent annual dose for occupational workers thyroid, skin, hands and feet dose limit.

A

500mSv

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14
Q

This is the effective dose frequent exposure limit for the public annually.

A

1 mSv

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15
Q

This is the equivalent dose limit of the publics lens of the eye.

A

15 mSv

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16
Q

This is the equivalent dose limit of the public skin, hands and feet.

A

50mSv

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17
Q

What is the annual effective dose for education and training exposures annually?

A

1mSv

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18
Q

What is the equivalent dose for education and training exposures to the tissues and organs?

A

lens of the eye- 15mSv
skin, hands, feet- 50mSv
Same as public exposures

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19
Q

What is the total equivalent dose limit for the embyro?

A

5mSv

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20
Q

What is the total equivalent dose for a fetus in 1 month?

A

.5mSv

21
Q

What is the negligible individual dose limit annually?

A

.01mSv

22
Q

For there to be fetal responses to irradiation there must be a very high dose of radiation greater than what?

A

25rad

23
Q

Leakage radiation from the tube housing must be less than what?

A

100mR/hr at 1 meter

24
Q

SID, Collimation and PBL must be accurate to what percent?

A

2% of SID (FFD)

25
Q

What is the total filtration for tubes operated at over 70kvp, 50-70kvp, 50kvp?

A

over 70- 2.5mm
50-70- 1.5mm
below 50- .5

26
Q

What are the 3 exceptions to the “dead mans” switch?

A
  1. portables
  2. FLuoro
  3. C-arm
27
Q

The source to table top distance for fixed fluoroscopic units should not be less than what? for mobile units?

A

Fixed- 38cm or 15in

Mobile- 30cm or 12in

28
Q

There is a 2mm lead equivalent barrier on the fluoro machine. at 100 kVp scatter from the patient is what at 1ft, 2ft, 3ft?

A

1ft- 500mR/hr
2ft- 100mR/hr
3ft- 50mR/hr

29
Q

Lead aprons must be worn by anyone whose exposure may exceed what?

A

5mR/hr

30
Q

What is the lead thickness required if a machine is routinely operated above 100kVp?

A

.5mm

31
Q

What is the average ESE of most conventional fluoroscopes?

A

5R/min

32
Q

What is the limit of ESE for conventional fluoroscopy?

A

10mA and 10R/min

33
Q

How many frames per second are sent to the TV monitor in pulsed mode fluoroscope?

A

30 frames per second

34
Q

What are spectral filters made of?

A

Copper or Copper/Aluminum

35
Q

What is pulsed width?

A

Exposure time for each pulse

36
Q

The fluoro procedure dose is affected by what 6 things?

A
  1. Mode used input phosphor diameter
  2. Selected mA
  3. OPeration in continuous vs pulsed
  4. Actual source skin distance
  5. Cumulative beam on time
  6. Number of “spots” taken
37
Q

All fluoroscopy examinations should be performed with the x-ray tube where?

A

Under the exam table

38
Q

What is the c-arm scatter radiation to the technologists eye/thyroid if the tube is under the table vs tube over the table?

A

12mR under table

60mR over table

39
Q

What is the c-arm scatter radiation to the technologist gonads if the tube is under the table vs over the table?

A

27mR under table

25mR over table

40
Q

Higher kVp increase the percentage of forward or backward scatter?

A

forward scatter

41
Q

Why does keeping the II as close to the patients surface as possible reduce pt and operator exposures?

A

The II will intercept the primary beam earlier and allow less scatter to the operator.

42
Q

What is the purpose of plastic “cones” on the collimator?

A

Prevents the x-ray tube from being brought closer than 12” to the pt

43
Q

What are the 3 high-risk procedures identified by the FDA which present the “possibility of exceeding 100 minutes fluoro time at 2-5R/min using 5” or 7” mode”

A
  1. PTCA- Percutaneous Transhepatic Cholangiography
  2. RFAB- Radio Frequency Ablation
  3. STEN- Stent Placement
44
Q

What is the most effective means the radiographer can use to limit radiation exposure to the patients?

A

Proper Collimation

45
Q

Which grid ratio should be used that will provide sufficient clean up of scatter?

A

the minimum grid ratio able

46
Q

Which speed class should be used to decrease exposure?

A

The highest speed class which does not present an unacceptable level of mottle.

47
Q

Patients gonads must be shielded anytime they lay how close to the edge of a collimated beam provided diagnosis is not compromised?

A

5cm (2’)

48
Q

What are the 4 types of shielding?

A
  1. Flat contact shields
  2. Shaped contact shields
  3. Shadow shields
  4. Contact lens and eye shields
49
Q

What is the difference between lead aprons and gonadal shields?

A

lead aprons are used to shield from scatter radiation and has a lower lead equivalency, they are also secondary barriers.

Rad Bio (5 decks)

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