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Normal Animal > Imaging Modalities > Flashcards

Imaging Modalities Flashcards

1
Q

Fluoroscopy

A

An imaging technique used to obtain real time moving radio graphic images of internal structures, more radiation exposure than radiograph

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2
Q

What is a C-arm

A

Portable fluoroscopy, used commonly in the OR because can move arm do not need to move patient

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3
Q

What are examples of procedures or illnesses fluoroscopy is helpful with?

A

Esophagram, collapsing trachea, angiocardogram, orthopedic procedures

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4
Q

What are the basics of CT scanning?

A

An X ray technique where radiation goes through the body, differentiated by tissues it passes, forms cross-sectional slides, no superimposition, can create 3D images

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5
Q

How does the CT scanner work?

A

The X-ray tube rotates around the patient and detectors determine amount of radiation absorbed by the patient, then “black box” makes image

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6
Q

What is the old method of CT scanning?

A

Single slice rotations. The tube would make a complete rotation then the table moves before next rotation.

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7
Q

What is the new method of CT scanning?

A

The tube continuously rotates while the table continuously moves like a spiral

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8
Q

What is multi-detector CT?

A

New scanners have multiple rows of detectors - more slices

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9
Q

What is a pixel

A

Pixel is a picture element and has only 2 dimensions (x, y)

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10
Q

What is a voxel?

A

Voxel is a volume picture element with three dimensions (x, y, z) pixel with thickness, z is the thickness

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11
Q

Voxel average

A

Can create inaccuracies, thinner slices prevent this average but higher radiation exposure

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12
Q

What is an isotopic voxel?

A

X, Y, Z dimensions equal, can do multi-plane reconstructions without loss of resolution

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13
Q

Hounsfield unit

A

attenuation coefficient, water is 0 HU, range from -2,000 (attenuate less aka air) to 2,000 HU (attenuate more aka metal)

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14
Q

what is the window?

A

range of Hounsfield units (HU) in a specific image

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15
Q

what is the level

A

the central value of HUs displayed in CT image

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16
Q

Wide Window

A

best for imaging tissue that varies greatly

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17
Q

narrow window

A

best for imaging tissue with similar densities

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18
Q

hyperattenuating

A

CT term for white, high HU, ex: bone and metal

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19
Q

hypoattenuating

A

CT term for lowest HU values, black, ex: air

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20
Q

advantages of CT

A
  • more detailed view of anatomy with no superimposition like xray
  • faster and less expensive than MRI
  • best for bone, lung, abdomen
21
Q

disadvantages of CT

A
  • radiation exposure
  • more expensive than radiographs
  • poor soft tissue contrast (compared to MRI)
22
Q

Basics of MRI

A
  • no ionizing radiation
  • involves magnet, computer, radiowave receiver and transmitter, and patient (containing H+)
23
Q

MRI image formation

A

H has 1 proton, and is abundant in body can act like tiny magnet, once in magnet machine H atoms line up on magnetic field (some face opposite direction but more line up with field) a radiofrequency coil applies energy causing the non-cancelled H to flip direction, once RF pulse stopped the energy is released goes to receiver coil and H returns to normal orientation, different tissues relax at different rates

24
Q

weighting

A
  • the use of certain parameters to optimize the different relaxation rates of different tissues to provide contrast
  • main weights: T1 and T2
25
Q

T1 weighted

A

based on molecular construct
fluid is hypointense (black)
fat is hyperintense (white)

26
Q

T2 weighted

A
  • based on physical construct
  • fluid is hyperintense (white) (liquid soft material)
  • fat is hypointense (black) (firm solid tissue)
27
Q

hypointense

A

less bright than tissue you compare to

28
Q

isointense

A

same brightness as tissue you compare to

29
Q

hyperintense

A

brighter than tissue you compare to

30
Q

advantages of MRI

A
  • better for soft tissue contrast and detail
  • noninvasive
31
Q

disadvantages of MRI

A
  • long scan times
  • expensive
  • general anesthesia
32
Q

Choose CT for:

A
  • better bone detail
  • good for thorax and abdomen
33
Q

Choose MRI for:

A
  • better soft tissue
  • good for neuroimaging, musculoskeletal (especially horses), CNS
34
Q

Acquiring CT

A
  • heavy sedation or general anesthesia
  • faster scan time (seconds/minutes)
35
Q

Acquiring MRI

A
  • general anesthesia
  • longer scan time (1-2 hours)
36
Q

safety concerns of CT

A

ionizing radiation

37
Q

safety concerns of MRI

A

projectiles, metal implants

38
Q

basic of ultrasound

A
  • soon be commonplace like stethoscope
  • sound wave frequency bounces off body subjects
39
Q

ultrasound waves

A
  • sound waves above acoustic level (we cant hear them)
40
Q

what creates the sound waves?

A

ultrasound transducers transmit and receive sound waves, transmits 1% of time, receives 99% of time (measures intensity and time of arrival of returning waves

41
Q

ultrasound frequency

A
  • freq. inverse to wavelength
  • lower freq. transducers penetrate farther but lower resolution
  • higher freq. transducers do not penetrate far but higher resolution
42
Q

how is US image formed?

A
  • using the echoes returning from the tissues, sound travels at constant rate in tissue, white means reflection off tissue
43
Q

how does US interact with matter?

A

differences in resistance to flow of tissues will alter sound wave direction (refract, reflect, or attenuate)

44
Q

anechoic

A
  • in US, shows black
  • ex: fluid filled cyst
45
Q

hypoechoic

A
  • in US, darker than compared structure
46
Q

isoechoic

A
  • in US, same echogenicity to compared structure
47
Q

hyperechoic

A
  • in US, brighter than compared structure
48
Q

what is the doppler effect?

A
  • change in frequency occurs as result of motion between sound source and observer
  • can determine velocity and direction blood flow
  • RBCs sound source, transducer is observer
49
Q

color flow mapping

A
  • BART: blue away, red towards

Normal Animal (22 decks)

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