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#2 BOARDS > Radiology Physics & Safety > Flashcards

Radiology Physics & Safety Flashcards

1
Q

Radiology physics

A
  • X-rays are part of the electromagnetic spectrum, which also includes radio waves, microwaves, infrared, visible light, UV, and gamma rays
  • The difference between these rays is the amount of energy, frequency and wavelength
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2
Q

Wavelength

A

Defined as the distance between two similar points on two successive waves

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3
Q

Frequency

A

Can be defined as the number of waves that pass a given point per unit time

  • The sorter the wavelength, the higher the frequency
  • X-rays have very short frequency and high energy
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4
Q

X-ray production

A
  • Fast moving electrons are released from x-ray tube
  • The tube contains a heated tungsten filament and a cathode
  • The electrons slam into a metal object (the anode)
  • 99% of the electrons produce thermal energy in this process, only 1% actually produce x-rays
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5
Q

Energy difference and transfer

A
  • The energy difference going from cathode to anode is measured in kilivolts (kV)
  • When the electrons strike the target, the energy is transfered in the form of kinetic energy (KE=1/2mv^2) where m = mass and v = velocity
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6
Q

Image formation

A

Factors controlled by operator:

  • mA, which idicates number of electrons that reach the anode (high mA = dark film, low mA = light film)
  • kV, which indicates the penetrating power of the electrons
  • Distance from x-ray tube
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7
Q

“Soft x-rays”

A
  • Lower voltage = decreased speed of electrons
  • Lower speed electrons = longer wavelength x-rays
  • Decreased penetrating power

Produced by decreased kVp, have long wavelength, low frequency, low penetration and are more dangerous to the patient

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8
Q

“Hard x-rays”

A
  • Increased voltage = increased speed of electrons
  • High speed electrons = shorter wavelength x-rays
  • Increased penetrating power

Produced by increased kVp, have shorter wavelength, higher frequency, increased penetration and are less dangerous to the patient

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9
Q

Intensifying screens

A

Intensifying screens, which are within the film cassette, convert the energy of the x-ray beam into visible light

After the image is intensified, a fluorescent image is produced and recorded on photosensitive film

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10
Q

Roentgen

A

International unit of quantity of radiation exposure

Ionization of air by radiation

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11
Q

Radiation absorbed dose (rad)

A

Unit of absorbed dose by the patient

1 RAD = 100 ERGS of energy per gram of tissue

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12
Q

Roentgen equivalent man (rem)

A

Unit of biological exposure in man

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13
Q

Equivalence between roentgen, rad and rem

A

1 roentgen = 1 rad = 1 rem

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14
Q

Curie (Ci)

A

Unit to measure radioactivity

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15
Q

Lethal dose

A

The dose of radiation that will result in death within 30 days in 50% of people

300 rad in a human

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16
Q

Radiation effects of gonads

A

10 rads = delayed menstruation/decreased spermatozoa
200 rads = temporary sterility
500 rads = permanent sterility

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17
Q

Fetal dose of radiation

A

10 rads

  • Spontaneous abortion rate increases by 0.1%
  • Congenital abnormalities increase by 1%
  • Malignant disease increases
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18
Q

Leakage radiation

A

All radiation from within the x-ray tube housing except the useful beam

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19
Q

Scatter radiation

A

Radiation that, during the passage through matter, has deviated in a direction beyond the image plane

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20
Q

Radiation protection ALARA concept

A

“As low as reasonably achievable”

  • A principle to protect occupational exposure to radiation
  • Three basic principles: time, distance and shielding
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21
Q

Time, distance, shielding

A
  • Radiation directly proportional to time exposed to radiation
  • Reduced radiation by keeping greater distance
  • Shielding your body from radiation via protective equiptment
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22
Q

Structural barriers

A
  • Walls and doors

- Control-booth barrier

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23
Q

Control booth barriers

A

Must be at least 7 feet tall from floor and be permanently secured

24
Q

Primary protective barrier

A

A wall that lies directly perpendicular to un-deflected line of travel of x-ray beams and its purpose is to prevent direct or un-scattered radiation from reaching the public

25
Q

Secondary protective barrier

A

Protects the personnel/public against secondary radiation that may leak or scatter, essentially, it is any wall or barrier that is never struck by the primary x-ray beam

26
Q

Accessory protective equiptment

A

Lead impregnated vinyl

  • Aprons
  • Gloves
  • Thyroid and neck shields

Protective eye glasses to shield lens of eye

Protective maternity apparel to protect pregnant radiologists and radiographers

27
Q

Limiting x-rays

A

Avoiding repeated x-rays, which diminishes unnecessary exposure

28
Q

Collimating (restricting) and filtrating x-ray beam

A

Limits the amount of low-energy photons that interact with the patient’s body and the amount of scattered radiation that enters the room

29
Q

Compton effect

A

Scatter radiation caused by interaction with outer shell electrons

It causes less radiation exposure to the patient and is detrimental to the image

30
Q

Collimators

A

Light beam that shows where the x-ray beam will project

31
Q

Photoelectric effect

A

The absorbed radiation involving interaction with the inner electron shell

It is beneficial to the image and increases the exposure to the patient - increases at lower kVp

32
Q

Orthoposer

A

The elevated lead lined base of the x-ray unit which the patient stands on during the x-ray

33
Q

Relative densities

A 
HIGH density 
- Cortical bone 
- Cancellous bone 
- Muscle 
- Nerve 
- Tendon 
- Ligament 
- Subcutaneous tissue 
- Fat 
- Air 
LOW density
34
Q

AP image

A
  • Aimed at lateral portion of navicular

- 15 degrees from vertical

35
Q

Lateral image

A
  • Medial side of foot against film
  • Central ray aimed at cuboid
  • Tube angled 90 degrees from vertical
36
Q

Medial oblique image

A
  • Center beam at lateral (3rd) cuneifom)

- Angle unit 45 degrees from vertical

37
Q

Lateral oblique image

A
  • Central ray aimed at navicular

- Center beam at 45 degrees from vertical

38
Q

Stress lateral or stress dorsiflexion image

A
  • Flex knees and maximally dorsiflex ankle

- Demonstrates any anterior ankle impingement (osseous equinus)

39
Q

Plantar axial image (sesamoid axial)

A
  • Head angled at 90 degrees to vertical
  • Aimed at plantar aspect of sesamoids
  • Good view of sesamoids and plantar aspect of metatarsal heads
  • Toes dorsiflexed against film and then raise heel
40
Q

Harris Beath (ski-jump)

A
  • Good for posterior or middle STJ coalitions
  • Angle unit 45 degrees
  • Patient stands on film with knees and ankles flexed 15-20 degrees
  • Take 3 views: 35, 40 and 45 degrees
41
Q

Calcaneal axial

A
  • Central ray aimed at posterior aspect of calcaneus
  • Angle unit at 45 degrees
  • Examines calcaneus for fracture, abnormalities in shape or internal fixation in major tarsal fusion
42
Q

Stress inversion (talar tilt) image

A
  • Patient supine or sitting in chair, internally rotate foot 15 degrees while stabilizing leg
  • Central ray focused at ankle joint
  • Performed after ankle inversion sprains
  • May need to anesthetize foot for pain relief and relaxation
  • Assesses for lateral ligamentous injury
  • Positive if talar tilt is greater than 4 degrees of inversion
43
Q

Anterior drawer test

A

Positive test is greater than 2 mm excursion of the talus out of the ankle mortise

44
Q

Ankle mortise image

A
  • Leg internally rotated 15 degrees, placing malleoli in a plane parallel to the film
  • Better view of tib fib articulation
  • X-ray head set at 90 degrees to vertical
  • Aimed at center of ankle joint
  • Articular relationship between trochlea of talux and tibial plafond
  • Space between lateral malleolus and talus
45
Q

Accessory bones

A

12 to know in the foot…

46
Q

Os vesalianum

A

5th metatarsal styloid process

47
Q

Os trigonum

A

Lateral tubercle of posterior process of talus

48
Q

Os peroneum

A

In peroneus longus as it courses under cuboid

49
Q

Os sustentaculum tali

A

Sustentaculum tali

50
Q

Os calcaneus secondaris

A

Anterior process of calcaneus

51
Q

Os tibiale externum

A

In tibialis posterior tendon at medial aspect of navicular, AKA accessory navicular

52
Q

Os intercuneiform

A

Intermediate cuneiform

53
Q

Os intermetatarsum

A

Between bases of 1 and 2

54
Q

Os talonavicular dorsale

A

Dorsal TN joint

55
Q

Fabella

A

Sesamoid bone in teh lateral head of gastroc muscle (behind knee)

#2 BOARDS (14 decks)

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