CleverOrca Vet Tech Studies > Diagnostic Imaging > Flashcards

Diagnostic Imaging Flashcards

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1
Q

Who discovered radiation?

A

Wilhelm Conrad Roentgen in 1895

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2
Q

What is radiation?

A

The propagation of energy through space in the form of particles or waves

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3
Q

What is ionization?

A

Process by which an atom gains or loses electrons to become a negatively or positively charged atom
Ion - charged particle that is either positive or negative
Ion pair - positive ion (atom missing an electron) and negative ion (ejected electron)

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4
Q

What is ionizing radiation?

A

Any type of radiation that is high in energy and capable of producing ions

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5
Q

Describe particulate radiation

A

Involves particles that have a mass and travel in straight lines at high speeds
Cannot reach the speed of light
May have a charge, except for neutrons

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6
Q

How much volts does a high-voltage x-ray circuit use?

A

65,000 to 100,000 volts

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7
Q

What does a transformer do?

A

Used in an electrical circuit to increase or decrease voltage

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8
Q

What is ampere?

A

Number of electrons per second

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9
Q

What is a kilovoltage peak?

A

Peak voltage of an alternating current
Determines speed at which the electrons are propelled from the cathode
Determines the penetrating power of the x-ray beam, called quality

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10
Q

Describe the cathode.

A

Negative
Controlled by mA settings

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11
Q

What is the tungsten filament?

A

Located in cathode
Emits electrons when heated - when mA is applied to the filament, electron cloud forms around it

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12
Q

What is the molybdenum cup?

A

Located in cathode
Focuses the direction of the electrons towards the anode

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13
Q

Describe the anode.

A

Positive
Controlled by kVp settings

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14
Q

What is the tungsten target?

A

Located in anode
Spot where electrons hit to produce x-rays

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15
Q

What is the focal spot?

A

Located in anode
Small area on target on the anode toward which the electrons from the focusing cup of cathode are directed
X-ray originate at the focal spot

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16
Q

What is the copper stem?

A

Located in anode
Dissipates excessive heat
X-ray production results in the generation of 1% X-rays and 99% heat

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17
Q

What is electromagnetic radiation?

A

Flow of energy through free space (or through a material medium in the form of electric and magnetic fields

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18
Q

X-rays are formed at the tube by what 2 mechanisms?

A

Braking radiation
Characteristic radiation

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19
Q

What is Bremsstrahlung (Braking) radiation?

A

Major source of X-rays produced in dentistry (70%)
Results when high-energy electrons come close to the nuclei of tungsten atoms
Electrons move towards the nucleus and then slow down due to the opposite charge- energy is then released

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20
Q

What is characteristic radiation?

A

Electrons from cathode dislodge electrons from inner orbital K/L shell of tungsten atoms
When electrons of inner shells are dislodged, electrons from other orbits fill empty space left by ejected electrons, producing energy
Not a significant source of X-rays as compared to braking radiation

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21
Q

What may cause fogging of a radiographic image?

A

Scatter radiation

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22
Q

How does F-speed film affect exposure?

A

F-speed film produces a 60% reduction in exposure

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23
Q

How does the silver halide crystals in faster film affect the image?

A

Faster film has larger silver halide crystals, which may lower the quality of the image

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24
Q

What are intensifying screens?

A

Plastic sheets coated with fluorescent material called phosphors that convert photon energy into visible light photons

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25
What is maximum permissible dose (MPD)?
Dose of radiation not expected to produce any significant radiation effects MPD for occupational persons: 5 rem/year Maximum accumulated dose: 5 rem x N -18 (N = age)
26
What is the general recommended Focal Film Distance?
Conventional: 40 inches Small/portable: 26 inches
27
What is a latent image?
An image formed by x-rays on the film, but are not visible yet
28
Describe developing.
Developing: 5 minutes at 68 F Reduction: reduces exposed silver halide crystals into black metallic silver (hydroquinone) Alkalizer: softens film emulsion and speeds up action (sodium carbonate) Restrainer: inhibits development of unexposed silver halide crystals (potassium bromide) Preservative: prevents oxidation (sodium sulfite)
29
What does fixing do?
Clears unexposed silver halide crystals (sodium thiosulfate)
30
What does the hardener do?
Shrinks and hardens emulsion (potassium alum)
31
What does the acidifier do?
Keeps medium acidic and stops additional development (acetic acid)
32
What are developing causes for film that is too dark?
Too much time in the developer High developer temperature
33
What are developing causes for film that is too light?
Too little time in the developer Developer temperature too low Developer exhausted Developer diluted with water Developer poisoned fixative
34
What are human causes for lack of contrast in film?
KVP set too high Radiation fog Increased temperature and humidity during film storage Out of date film Not using a grid with a high kVp Double exposure Safelight failure or light leakage
35
What is a cause for yellow film?
Incorrect fixation (not fixed long enough, film sticking together during fixation, incomplete final wash)
36
How will the ribs appear if the patient is in a true lateral position?
Superimposition of the rib heads throughout the thoracic spine
37
When taking an x-ray of a horse's oblique metacarpus, how many metacarpal bones will be in the view?
Horses have 4 metacarpal bones - when taking an x-ray of the metacarpus, the view will show MC bones 2-4
38
How does negative contrast media appear?
More radiolucent than surrounding tissues
39
What are some characteristics of negative contrast media studies?
Shows location, size, and wall thickness of organ and large luminal filling defects (masses, foreign bodies) Gives little information about mucosal surface/smaller defects due to overexposure - small tears may be missed
40
What are negative contrast studies generally used in?
Bladder studies (pneumocystogram) GI tract (pneumogastrogram, pneumocolon) Joints (negative arthrogram)
41
What is the most common negative contrast agent used in veterinary radiography?
Room air
42
How does positive contrast media appear?
More radiopaque than surrounding tissues
43
What are some characteristics of positive contrast media studies?
Give less information than negative contrast studies, but best way to detect small defects
44
What are the most common positive contrast medias used in veterinary radiography?
Barium and iodine preparations
45
What is a complication of barium administration in a patient with a perforated gut?
Barium leakage remains indefinitely in the mediastinum or peritoneal cavity, causing granulomas and adhesions
46
What is ionic, water-soluble iodine contrast media used for?
Commonly used for IV (excretion) urography Must not be used for myelography as their high osmotic pressure causes sever damage to nervous tissues that may be fatal
47
What media is mainly used for myelography?
Non-ionic, water-soluble iodine contrast media
48
How can double contrast studies be beneficial?
Gives better mucosal detail than a positive/negative study alone and more reliably shows small filling defects in the puddle of residual positive contrast medium
49
How do double contrast studies work?
Use a small amount of positive contrast medium to coat mucosal surface of a hollow organ, followed by distension with air
50
How does brightness relate to reflection?
The brighter the object, the bigger the reflection. The darker the object, the fewer reflections it is receiving back (such as with fluid field structures)
51
How are ultrasound waves created?
Through special piezoelectric crystals in the transducer - the crystals oscillate with electrical currents; returning sound waves strike the crystal and the crystal oscillations are converted to electrical signals
52
What is the ultrasound frequency range?
2-15 MHz
53
How does frequency effect imaging?
Higher frequencies produce better images, but don't transmit as deeply into tissues at lower frequencies
54
What are the 2 types of tranducers?
Linear - wide, create a rectangle picture that has a wider near field than a sector transducer Sector - pie-shaped picture; good for looking in between ribs to image the heart
55
How many images at once can modern multi-slice CT scanners take?
Can acquire up to 620 cross-sectional images at once; each rotation may be as short of 1/4 second
56
How does CT differ from ordinary X-rays?
Creates cross-sectional images of a body part By sequentially scanning a body area, an entire organ or other structure can be imaged without interference from neighboring or overlaying structures
57
What is a mirror artifact?
Occurs when there is a highly reflective surface in the path of the primary beam, causing the appearance of an object mirror image under examination on the far side of the interface
58
What is an acoustic shadow artifact?
Occurs when there is a large difference in acoustic impedance between 2 tissues - sound will be reflected and will not penetrate deeper tissues
59
What is acoustic enhancement?
Occurs when there is less loss of energy of sound waves passing through a fluid filled structure than through soft tissue, resulting in the region beyond a fluid filled structure to appear brighter than adjacent tissues
60
What is reverberation artifact?
Produced when sound reflected from a highly reflective interface hits the transducer face and is reflected back into the tissue, resulting in appearance of multiple parallel echoes regularly spaced beyond the interface
61
How can radiographic detail or definition be increased on an image?
Increasing the source-image distance - the distance from the tube to the image receptor
62
What describes the use of sound waves to form bubbles around fat cells that burst and cause the cells to break down?
Cavitation
63
How long does it take for barium to move through the upper GI tract?
180 minutes
64
What is likely to cause black crescent-shaped marks on an image?
Bent film
65
What is the amount of time an X-ray film must be kept in an archive?
Varies by state or province
66
What results when the contrast of a radiograph decreases?
Grayer radiographs with many steps but fewer differences between each step
67
What is the dosage for barium for a lower-GI series in a 25-pound dog?
3 to 5 mL/lb
68
What can decrease the length of service of a film?
Old fixative chemical
69
What is the likely cause of yellow-brown staining on a film that has been archived for 6 years?
Incomplete rinsing of the film
70
What besides patient movement can cause a radiograph to come out blurry?
Poor film-screen contact
71
What dental imaging technique is less likely to cause distortion?
Paralleling technique
72
A dog comes in for a severe infection of the nasal cavity. What is the most important view?
Lateral skull view - best for nasal cavity, frontal sinuses, and osseous bulla
73
Most states have a requirement to trap elemental silver from which chemicals after processing?
Fixative
74
A dog comes in with a facial fracture of the zygomatic arch. What view will show the fracture the best?
Ventrodorsal View
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