Tech, Positioning, Special Imaging Flashcards

1
Q

What part of the x-ray machine PRODUCES x-ray?

A

The tube comprised of a glass envelope, exit window, cathode (- small and large filaments with focusing cup) and anode (+ target plate slanted 12o)

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2
Q

What is the housing of the tube made of?

A

Lead-lined steel or aluminum and contains oil

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3
Q

When to use small vs large filaments?

A

Small: smaller targets, longer exposure time, more penumbra
Large: larger objects, shorter exposure time, less penumbra

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4
Q

Characteristic radiation aka Hard x-rays:

A

10-15% of beam and doesn’t contribute to formation of image

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5
Q

Bremsstrahlung radiation aka Braking radiation AKA soft x-rays:

A

85-90% of x-ray beam and creates image

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6
Q

Deflected x-rays create?

A

Filmfog

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7
Q

Compton effect:

A

interacts with matter causing ionizing radiation which may damage tissues with lots of H+ (fat)

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8
Q

How does a grid help with the Compton effect?

A

Reduces scatter radiation that reaches the film

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9
Q

Photoelectric effect:

A

X-rays completely absorbed by patient and has no effect on film

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10
Q

Radiographic noise:

A

Unwanted radiographic densities that obstruct viewing of structural details on film

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11
Q

Artifact:

A

Caused by objects in or on patient like necklaces, rubber bands, implanted medical devices or caused by damage to film emulsion

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12
Q

Three types of mottle:

A

Quantum: variation in density of uniformly exposed film from random spatial distribution of x-ray quanta absorbed in screen
Structure
Film graininess

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13
Q

Ways to reduce scatter radiation:

A

Reduce beam size, increasing kVp, decreasing field size (collimation, grid, air-gap),

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14
Q

Thermionic emissions:

A

Boiling off of electrons from heated filament, current is mA increasing current current increase temperature increases number of electrons generated

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15
Q

Rectifier:

A

Converts AC to DC voltage measured in kVp and affects speed of electrons

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16
Q

Port filters:

A

made of aluminum and decrease amount of radiation patient is exposed to and decrease the amount of tissue damage

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17
Q

Collimator:

A

Device made of two layers of metal laid at right angles narrows field size to reduce pt exposure dose, scatter and improves quality of film

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18
Q

Lead shields

A

Prevent x-rays from passing through organs like gonads, thyroid, etc

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19
Q

Increasing the mA brings what filament into play? Decreasing?

A

Large filament

Small filament - sharper image

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20
Q

Good and best grid ratios?

A

12: 1
6: 1

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21
Q

Put in order: grid, film, pt

A

Pt, grid, film

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22
Q

Intensifying screen:

A

Made of small phosphorus crystals, two of them on either side of film, crystals fluoresce and expose film, large crystals increase light and small ones increase detail

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23
Q

Silver halide crystals:

A

embedded in emulsion layer of gelatin in film plastic which is sensitive to light emitted by screens and x-rays

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24
Q

Six processing steps of film:

A
  1. Pre-wet - allow chemicals to penetrate emulsion uniformly
  2. Develop: in solution for 5 seconds so silver halide crystals reduce to black metallic silver raising temperature 1o will decrease developing time by 20%
  3. Stop bath: water + acetic acid for 30s to stop action of developer
  4. Fix: solution for 10 minutes, stops development, hardens film, sodium thiosulfite and reclaim silver from old films
  5. Wash: removes developer and fixer, prevent brown film
  6. Dry
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25
Q

Density:

A

Overall blackness of film

Directly proportional to kVp and mA (1o)

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26
Q

Contrast:

A

Differences in shades of gray in film and indirectly related to kVp (low contrast high kVP, high contrat, low kVp)

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27
Q

Detail:

A

How clear structures are visualized

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28
Q

How would you increase detail?

A

Increae FFD, decrease OFD or kVp

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29
Q

FFD of 40” vs 72”

A

40: more radiation, penumbra, magnification and less detail
72: less radiation, penumbra, magnification, and more detail

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30
Q

Inverse square law:

A

radiation intensity is inversely related to square of FFD

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31
Q

50/15 rule:

A

50% decrease in mAs is equivalent to a 15% increase in kVp

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32
Q

16:20% rule:

A

Decrease kVp by 16% you have to double mAs or it will halve the film density
If you increase kVp 20% you have to decrease mAs by half or you will double the film density

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33
Q

Increasing kVp will:

A

increase film exposure, scatter radiation, fog and decrease contrast

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34
Q

Increasing mAs will:

A

increase film exposure and darken film

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35
Q

Anode heel effect:

A

Cathode should be closer to larger or fatter part of the object

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36
Q

Bergonie-Tribondeau law:

A

Radiosensitivity of tissue is directly proportional to the rate at which the tissue multiples

37
Q

What are radiosensitive tissues?

A

Gonads, bone marrow, lymphoid tissue, colon, lungs

38
Q

What are radioresistant tissue?

A

Brain, spinal cord, thyroid, muscle

39
Q

HVL:

A

High value laser, thickness of a material needed to attenuate intensity of the x-ray by 50%

40
Q

Rem:

A

Roentgen equivalent in man; unit of ionizing radiation

41
Q

Sievert:

A

Unit of ionizing radiation absorbed dose equivalent to 100 Rems

42
Q

Millisievert:

A

1000th of a Sievert [10^-3 SV]

43
Q

RAD:

A

Radiation absorbed dose

44
Q

RBE:

A

Relative biological effectiveness

45
Q

What to do if a film is underexposed? Overexposed?

A

Increase mAs

Decrease mAs

46
Q

What films are taken at 72”?

A

Cervicals: lateral, obliques, flexion, extension
Chest: P-A, lateral
Lateral sternum
Full spine AP and later

47
Q

What film are PA?

A

Skull, mandible, chest, wrist, tunnel, patella

48
Q

Which films are inhale and hold?

A

PA, lateral chest (not if pneumothorax)
AP full spine
AP and lateral thoracic spine

49
Q

When should grids be used?

A

Body parts >12cm to reduce scatter radiation with at least 70 kVp

50
Q

Which films have caudal tube tilts?

A

Cervical anterior oblique
Lateral lumbar
AP coccyx
Y-scapular

51
Q

Holmblad is also known as?

A

Intercondylar and Tunnel

52
Q

The sunrise view of the knee is also known as?

A

Tangenital

53
Q

The abduction view of the shoulder is also known as?

A

Baby arm

54
Q

The caldwell view is for what anatomy?

A

Frontal sinus

55
Q

The towne view is for what anatomy?

A

Foramen magnum

56
Q

The water view is for what anatomy?

A

Maxillary sinus

57
Q

The lateral skull view is for what anatomy?

A

Sella turcica

58
Q

The apical lordotic view is for what anatomy?

A

Pancoast tumor

59
Q

The Sunrise view is for what anatomy?

A

Apical view of the patella and intercondylar groove

60
Q

Cervical anterior oblique tube tilt, central ray focus?

A

150 caudal

C4; RAO shows R intervertebral foramina

61
Q

Cervical posterior oblique tube tilt, central ray focus?

A

15o cephalad

C4; RPO shows L intervertebral foramina

62
Q

AP Lower cervical tube tilt, central ray focus?

A

15o cephalad

C4

63
Q

Lateral lumbosacral tube tilt?

A

5o caudal

64
Q

AP coccyx tube tilt, central ray focus?

A

10o caudal

1” superior to symphysis pubis

65
Q

PA lumbosacral spot tube tilt, central ray focus?

A

30o cephalad

L5 spinous process

66
Q

AP sacrum tube tilt, central ray focus?

A

15o cephalad

1/2 btw ASIS and symphysis pubis

67
Q

AP Foot and medial oblique tube tilt, central ray focus?

A

10o cephalad

Base of 3rd metatarsal

68
Q

Axial patella tube tilt?

A

10-20o cephalad

69
Q

Lateral and AP knee? tube tilt, central ray focus?

A

5o cephalad

Center of joint and inferior pole of patella

70
Q

APOM tube tilt, central ray focus?

A

5o cephalad

Through the uvula of the soft palate

71
Q

CT (Computerized Tomography)

A

Conventional X-radiation measured in Hounsfield unit produces reconstructed axial images with a thin fan-shaped x-ray beam (rotate around pt in 180o arc in serial or spiral fashion) producing slices 1-10mm thick, image tends to be grainy

72
Q

Pros to CT:

A

Contrast resolution 95X better than conventional radiography, can make 3D images of any part of the body, good for intraspinal and intracranial masses, bleeding, spinal canal stenosis, abdominal masses, bony structures, lung pathology, disc

73
Q

Cons to CT:

A

Excludes very large patients, pregnant people, induce sense of claustraphobia, increased exposure to ionizing radiation

74
Q

MRI:

A

Large magnetic field (30,000X >than Earth’s magnetic field) to generate radio frequency waves measured in Tesla units and measures how much H+ reacts to magnetic and radio waves
T1 for fatty tissues as white - gadolinium contrast
T2 for water as white

75
Q

Pros to MRI:

A

No radiation, good for spinal cord and brain pathology, disc lesions, solid organ pathology, mets, demyelinating CNS disorders, musculotendinous disorders

76
Q

Cons to MRI:

A

claustraphobia, no large patients, contraindicated for pacemakers and defibrillators, intracranial aneurysm, surgical clips, cochlear implants, neurostimulators

77
Q

Radionuclide Bone Imaging (Bone scan, Bone Scintigraphy):

A

Use radioactive pharmaceuticals (technetium 99, indium 111 labeled WBCs) injected into patient and gamma camera to create the images, radioactive material is taken up by osteoblastic tissue (SI, AC, SC joints, kidney, tips of scap, frontal parasagittal regions of the skull, costochondral joints, occult fx, AVN,PE, blastic mets, osteomyelitis)

78
Q

Diagnostic Ultrasound:

A

High frequency sound waves to investigate suspected vascular diseases (AAA, carotid/vertebral A disease, pregnancy, ovarian disease, cholelisthiasis)

79
Q

fMRI

A

Measuring brain activity by detecting changes inblood oxygenation (hemoglobin contains iron can be magnetized) and more active areas of the brain require more oxygen resulting in change in density of the magnetic signal
For pt’s suffering from depression, schizophrenia, fibromyalgia

80
Q

PET

A

Measure regional cerebral BF using radioactively labeled tracer glucose molecules since most tumors preferentially use glycolytic pathway for energy there’s a greater concentration of radioactive glucose in malignant tissues (Warburg effect)

81
Q

SPECT

A

Injection of radionuclide into blood stream and pictures are taken w/gamma camera

82
Q

When do you use a barium swallow?

A

Visualize

83
Q

ALARA:

A

Radiation exposure should be kept AS LOW AS REASONABLY ACHIEVABLE

84
Q

10 day rule:

A

Limit exposure to radiation to 10 day period following onset of menses in a female

85
Q

American College of Radiology Practice Guidelines for the performance of Spine Radiography in Children and Adults (2007):

A

Evaluation of: pain or limitation of motion, spinal trauma (symptomatic or in at risk patients), previous surgery, suspected malignancy, congenital anomalies, previously detected spinal abnormality, alignment abnormalities including scoliosis and kyphosis, shoulder or arm pain from suspected cervical radiculopathy, occipital headache, pain radiating around the chest wall, pain radiating into buttock/hip/groin, compression fracture

86
Q

Canadian C-spine rules:

A

Radiographs if after trauma
High risk factors such as older than age 65, work with dangerous mechanisms or paresthesia in extremities
Presence of midline cervical spine tenderness or delayed onset neck pain
Unable to actively rotate the neck beyond 45o

87
Q

NEXUS rules:

A

No x-ray needed if present after hx of injury to neck:
No posterior cervical spine tenderness, evidence of intoxication, focal neurological damage, painful distracting injury
Normal level of alertness

88
Q

Ottawa knee rules:

A

X-rays recommended if hx of trauma to knee and:
>55 years, isolated tenderness of patella, tenderness at head of fibula, inability to flex to 90o inability to take more than 4 steps immediately and in office

89
Q

Ottawa ankle rules:

A

> 55 years, inability to take more than 4 steps immediately and in office, local tenderness at talus, navicular, cuboid, 5th met or posterior/crest of either malleolus