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PTRS 746 > Medical Imaging > Flashcards

Flashcards in Medical Imaging Deck (77):
1

What two errors can be made in imaging?

Errors of observation, errors of interpretation

2

How is imaging important to PT?

diagnostics are a tool, not the answer. relate imaging to clinical care
enhances comprehensive exam, guides and informs treatment, improves communication between PT and Dr., PT is direct access

3

What is a true positive?

test detects something that is really there

4

What is a false positive?

test detects something that is not really there

5

What is a true negative?

test detects nothing, and there is nothing there

6

What is a false negative?

test detects nothing, but there is something there

7

What is sensitivity?

at test's ability to identify a true positive
negative test means you definitely don't have the condition
SNOUT

8

What is specificity?

test's ability to identify a true negative
positive test means you definitely have the condition
SPIN

9

What is an example of a sensitive test?

HIV blood test. have low false negative but can have high false positives

10

What is an example of a specific test?

home pregnancy test. have low false positives but can have high false negatives

11

What are advantages of X-ray?

time and cost efficient
non-invasive
low risk
good for screening

12

What are disadvantages of x-ray?

may be normal when pathology actually exists

13

What is attenuation?

reduced strength or density of the x-ray beam as it passes through a medium

14

What is permeability?

ability of xray beam to pass through substance to reach film plate

15

What is radiodensity?

x-ray absorption capacity based on substance's composition, density, and thickness

16

How is radiodensity of an object related to radiodensity of the x-ray?

radiodensity of an object is inversely related to radiodensity (amount of blackening) on the radiograph

high object density results in lower density on film so the object appears whiter

17

What is a radiolucent substance?

easily penetrated by x-rays (low attenuation)

18

What is a radiopaque substance?

not easily penetrated by x-rays (high attenuation)

19

How is air shown on an x-ray? Where is it normally present?

least radiodense substance in the body.
Will show up black on film
normally present in trachea, lungs, stomach, digestive tract

20

How does fat and water show up on x-ray?

fat appears gray-black on film
water appears gray on film

21

How does bone, contrast, heavy metals show up on x-ray?

bone appears gray-white
contrast media appears as white outline
heavy metal appears solid white

22

What does "one view is no view" mean?

at least two views ideally at 90 degree angle to each other, are necessary to visualize an object in three dimensions
radiograph is two dimensional picture of a three dimensional object

23

What are two photographic qualities of imaging?

density: amount of blackening on radiograph dependent on distance, time, and current
contrast: differences between adjacent tissue densities

24

What are two geometric (clarity) qualities of imaging?

detail: aka sharpness or resolution; maximized by positioning patient so structure of interest is closest to film plate
distortion: usually occurs due to distance between beam source, patient, and image receptor, and from alignment and positioning issues

25

What to structures closest to the film plate look like?

they are more sharply defined and are imaged with less size distortion

26

What is foreshortening

image appears shorter and wider than the actual object or structure

27

What is magnification

objects or structures further from film appear larger than closer points

28

How are radiographs named?

named for beam direction relative to patient and patient's position

29

What is AP image?

x-rays travel through the patient from an A to P direction: the x-ray tube is in front of patient and the film plate is behind

30

What is lateral/oblique views?

named for side closer to film plate

31

What are some special x-ray positions?

oblique, open mouth: upper c spine, flexion/extension, sunrise or tangential: patellofemoral joint, upright weight bearing

32

How are AP/PA and lateral radiographs viewed?

AP/PA: viewed with patient facing viewer in anatomical position; hands, feet, and digits point upwards
Lateral: viewed in direction the x-ray beam traveled

33

What does the A in ABCs of radiology stand for?

Alignment: gross bone size, number of bones, shape and contour of cortical outline, joint position and alignment

34

What lines do you need to reference to with images of the spine?

anterior vertebral line
posterior vertebral line
spino-laminar line
posterior spinous line

35

What is the B in the ABCs of radiology?

Bone density: weight bearing surfaces should have higher density, cortical margin should be dense with lower density cancellous bone and medullary cavity, low contrast bone suggests osteoporosis, excessive sclerosis may suggest arthritic or rheumatic condition

36

What is the C in ABCs of radiology?

Cartilage: joint space width, subchondral bone, joint margins, epiphyses and growth plates

37

what is the s in the ABCs of radiology?

soft tissue: gross size of musculature, outline of joint capsules, periosteum

38

What is contrast enhancement?

injection or ingestion of radio-contrast medium prior to radiographic study
e.g.- arthrography, myelography, barium swallow studes, angiography, arteriorgraphy, cholecystography, urograms

39

What is a CT?

computed tomography: uses x-ray attenuation to produce cross sectional images

40

How is a CT set up?

x-ray tube and film move about a fulcrum

41

What does a CT provide an image of?

provides detailed anatomical imaging of bone

42

How are CTs read?

transverse images are read from the bottom looking up (feet to head)

43

What are advantages of CT?

sensitive and specific for fracture
useful for rapid assessment of brain or neurologic injury

44

What are disadvantages of CT

radiation exposure
discriminates density, but limited in precise histologic differences
small volumes of tissue image as a uniform shade of gray

45

How does an MRI work?

uses pulses of radio frequency and a strong external magnet to generate an electromagnetic field
When the field is removed the nuclei realign to their resting state releasing resonance energy
this produces a radio frequency signal that can be captured and processed into an MRI

46

What is resonance?

alignment of atomic nuclei to the electromagnetic field

47

What are advantages of MRI?

good sensitivity
images soft tissue well
no radiation
little distortion, as images are obtained in one plane

48

What are disadvantages of MRI?

relatively low specificity
expensive
contraindicated if patient has a ferrous metal implant or exposure (orthopedic hardware is not ferromagnetic, but surgical clips usually are; pacemaker function can be compromised by magnetic field)

49

What is a T1 image?

longitudinal magnetization: how long it takes protons to 'relax' back to resting state following a RF pulse
has short repetition and echo times

50

What is a T2 image?

transverse magnetization: how long resonating protons remain 'in phase' following a RF pulse
has long repetition and echo times

51

How do T1 images show up on an MRI?

bone, fat, and hemorrhage have high (bright) signal
fluid and soft tissue have low (dark) signal
good gray/white matter discrimination
T1= 1ong bone is bright

52

How do T2 images show up on an MRI?

fluids and fluid filled structures are bright
fat and bone are dark
useful fro imaging CSP, edema
T2=H2O is bright

53

What are T2 images good for?

show soft tissue pathology and are ideal for acute trauma

54

What are T1 images good for?

weighted images reveals details of anatomy in high resolution

55

What is contrast MRI?

intravenous or intra-joint injection (arthrogram)
tissue enhancement is proportional to blood flow to the tissue
increased signal to T1 weighted images
before and after contrast image comparisons

56

What is a functional MRI?

technique based on increased blood flow that accompanies neural activity in the brain (BOLD technique)

57

What is contrast agent?

uses magnetic properties of deoxyhemoglobin as an endogenous contrast agent

58

What is DEXA used for?

widely used method of measuring bone mineral density
can also determine body composition

59

How does a DEXA work?

high and low energy x-rays are directed at bone from two different sources
difference in absorption between the beams is used to determine bone density

60

What is nuclear medicine used for?

use of radiopharmaceuticals for diagnosis, therapy, and research

61

How does nuclear medicin work?

radiopharmaceuticals are radioactive tracers that are absorbed according to the tissue's metabolic properties
detection of the location and concentration of radioactive elements is used to produce an image

62

What modalities fall under nuclear medicine?

single photon emission computed tomography (SPECT)
positron emission tomography (PET)
PET/CT and SPECT/CT
radionuclide scintigraphy (bone scan)

63

What is radionuclide scintigraphy used for?

detection of stress fractures and detection and follow up of metastatic bone disease

64

How is scintigraphy done?

labeled methylene is injected, scanning occurs 2-3 hours following injection

65

What does high uptake indicate in scintigraphy?

indicates areas of increased bone activity or mineral turnover

66

What are advantages of scintigraphy?

highly sensitive for early bone and joint disease
fast
reasonable cost

67

What are disadvantages of scintigraphy?

poor specificity
easily influenced by osteoblastic activity or blood flow of any etiology

68

What is ultrasonography?

anatomic images achieved through sound waves
different tissues have different acoustic qualities

69

What can ultrasonography be used for in PT?

during physical exam and with active functional activity
only be used to confirm diagnosis

70

Is ultrasonography easy to use?

operator dependent, good technique requires practice

71

What is the order of imaging done when evaluation a patient?

conventional radiographs are the first order modality
CT is used to visualize complex anatomy
MRI is used to assess soft tissue

72

What is the trauma survey?

diagnose and evaluate fracture or dislocation
match mechanism of injury to clinical presentation
assess treatment and monitor healing

73

In trauma what images are done?

lateral C-spine
AP chest
AP pelvis
possibly: x-ray of extremities, lateral views of T-L spine, CT of head, CT of C-spine, CT of thorax abdomen pelvis with/without contrast

74

What is Pittsburg decision rule for knee trauma?

x-ray ordered if history of blunt trauma or fall AND age under 12 or over 50 AND/OR inability to walk 4 weight bearing steps in ER

75

What is Ottawa knee rule?

x-ray ordered if age >55 years, tenderness at fibular head, isolated tenderness at patella, inability to flex knee to 90, inability to walk 4 weight bearing steps in ER

76

What is Ottowa ankle and foot rules?

ankle: pain in malleolar area AND tenderness at posterior aspect or tip of lateral malleolus, OR tenderness at posterior aspect or tip of medial malleolus, OR inability to WB immediately and in ER

foot: pain in midfoot area AND tenderness at base of 5th MT, OR tenderness at navicular bone, OR inability to WB immediately and in ER

77

What are imaging guidelines for acute low back pain?

1) For adults 50 with findings suggestive of systemic disease, conventional radiography and simple lab testing can almost completely r/o underlying systemic disease
3) Advanced imaging should be reserved for patients who are considering surgery or those in whom systemic disease is strongly suspected