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Body logistics > L18- Introduction to medical imaging > Flashcards

L18- Introduction to medical imaging Flashcards

1
Q

two broad typical of medical imaging

A

plain filming imaging

cross sectional imaging

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2
Q

plain film imaging

A

X-ray

Fluoroscopy

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3
Q

cross sectional imaging

A

CT

MRI

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4
Q

x-rays are part of the

A

electromagnetic spectrum

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5
Q

X-ray is higher frequency than….. but lower than …..

A

UV

Gamma

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6
Q

how does an X-ray work

A
  1. X-ray soruce focuses a beam of high energy electrons that pass through the body onto an X-ray receiver
  2. Some X-rays are absorbed
  3. Some x-rays are scattered (attentuation)
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7
Q

attenuation is dependent on

A

the density and atomic number of tissue constituents e.g. metals like calcium in the bone

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8
Q

the more dense (e.g. bone)

A

the more attenuation (scattering) and lighter the appearance

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9
Q

in X-rays there are .. principle densities

A

5

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10
Q

name 5 principle densitities

air

fat

soft tissue

bone metal

A
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11
Q

X-rays used to be visualised manually on film, however now they can be visualised on

A

Picture Archiving and Communication Systems (PACs)

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12
Q

Picture Archiving and Communication Systems (PACs) advantages

A

Zoom

Alter density

Measure distances

Measurement of angles

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13
Q

fluoroscopy is a method used in

A

X-ray

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14
Q

fluorscopy can be used to

A

Examination of anatomy and motion

  • Uses constant stream of x-rays
  • Enhanced by contrast
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15
Q

Contrast media

A

Where contrast agents is used to better differentiate tissue during medical imaging.

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16
Q

Contrast media:

A

a substance used to increase the contrast of structures or fluid within the body in medical imaging. Contrast agents absorb or alter external electromagnetism or ultrasounds.

Different types based on modality of examination

(Different radiopharmaceuticals, which emit radiation themselves).

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17
Q

Examination techniques which use contrast media

A

Fluoroscopy

CT

MRI

Arteriograms (e.g. cardiogram with dyes)

Ultrasound

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18
Q

Two categories of contrast agentP

A

Positive agents- appears white (high atomic number)

  • Barium
  • Sulphate
  • Iodine

Negative agents- appears black (gases of low density)

  • Air
  • Oxygen
  • Carbon dioxides

Agents can be combined to produce a double-contrast

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19
Q

Ideal Phase Contrast Agents

A
  • Low osmolality and viscosity
  • High water solubility
  • Biologically inert
  • Safe
  • Heat and chemical satiability
  • Cost-effective
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20
Q

Administration

A
  • Oral
  • Rectal
  • IV
  • IA
  • Filling a space or cavity (cavity, bladder, intrathecal space, gall bladder etc)
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21
Q

phase contrast can be used to

A

detect blockages or tears e.g. in the bowel (e.g. perforation of bowel)

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22
Q
A
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23
Q

Excretion of phase contrast

A
  • Glomerular filtration (95%)
    • Important kidneys are working
  • Tubular excretion and protein being negligible
  • Half life: 30-60 minutes
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24
Q
A
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25
Q
A
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26
Q

Side effects of phase contrast

A
  • Reactions due to osmolality
  • Endothelial damage
  • Thrombosis and thrombophlebitis
  • Vasodilation
  • Vasodilation
  • Vascular pain
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27
Q

Idiosyncratic reactions

A

Cant predict (within 30 mins)

  • Mild (most- rash etc~)
  • Moderate
  • Severe (0.03%)- very rare
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28
Q

Nonidiosyncratic reactions

A

( beyond 30 mins to 7 days)

  • Cardiac
  • Nephrogenic
  • Extravasations
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29
Q

how do patient do a gluorscopy

A

Patients swallow contract (barium, iodine, gadolinium (MRI))

Strongly absorbs X-any dense white

Any space it can be swallowed, inserted or injected

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30
Q

fluoroscopy used in

A
  • Angiography
  • Contrast GI studies
  • Therapeutic joint injection
  • Arthrograms
  • Screening in theatre
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31
Q

advanatges of fluoroscopy

A
  • Cheap
  • Dynamic
  • Interventional procedures e.g. stunting
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32
Q

disadvantages of fluorscopy

A

radiation

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33
Q

systemic approach of reading an X-ray e.g.

A

Date taken

Patient demographic

Penetration- are we using the correct amount of energy beams to get good photo

View- how the X-ray beams pass through the patients (PA/AP/ lateral)

Rotation- how the patient is positioned

34
Q

how to read a chest X-ray (CXR)

A

A-Airways -trachea and bronchi

B-Breathing- lungs should be black. Trace all the way around the edge- can you see the nice angels

C-Circulation- the heart and aorta. Should see the heart easily- white

D-Disability- bone

E-Everything else- tubes and lines

35
Q

how to a read an abdominal x-ray (AXR)

A

A-Air

B-Bowel

a. Small bowel
b. Large bowl

D-Densities (bone)

O- Organs

36
Q

fractures =

A

displacements

37
Q

bone abnormality

A

bone qaulity (lytic, sclerotic, mixed)

38
Q

advantages of X-ray

A

Advantages

Quick

Portable

Cheap

Simple

39
Q

disadvantages of X-rays

A

Disadvantages

Radiation

One plane so 2D

Would not see all pathology

Cant visualise all areas

Poor soft tissue imaging

40
Q

uses of X-rays

A
  • Chest
    • Infection, pneumothorax, trauma, effusion, oedema
  • Bowel
    • Dilation, perforation
  • Orthopaedic
    • Fracture, trauma
  • Post-procedure
    • Nasogastric tube, pacemaker
  • Dentist
41
Q

CT (computed tomography) uses what machinary

A

Uses rotating gantry

X-ray tub on one side

Detectors on the other

42
Q

how does a CT give a detailed image

A

Lots of slices of images up together by computer- same principle of attenuation as X-ray

Usually transverse images

43
Q

density in CT measured in

A

hounsfield units

44
Q

advantages of CT scan

A
  • Quick
  • Good spatial resolution
  • Can scan most areas (not all)
45
Q

disadvantages of CT scan

A

Radiation

Lower contrast resolution

Affected by artefact

Requires breath holding (not all patient can manage)

Overuse (fishing for diagnosis)

Incidental findings

46
Q

CT scan uses

A

Diagnosis- cancer, stroke, bony injury, blood flow

Guide further tests or treatment- radiotherapy, biopsy

Monitor conditions e.g. cancer treatment

47
Q

MRI (magnetic resonance imaging) uses…

A

magnetic field instead of X-ray

48
Q

How does MRI work

A
  • Relies on narrow gantry
  • Uses a strong magnetic field
    • Image quality relies on magnetic field
  • Aligns hydrogen atoms
  • Some point towards the head and some towards the feed
    • Not 50/50
  • Unmatched ions remain
  • Radiofrequency pulse applied
  • Unmatched ions absorb energy and spin in different directions
  • Pulse is turned off and atoms spin returns which emits energy
  • Computer processing to generate image.
49
Q

in M RI different relaxations produce different

A

weighting from tissues

50
Q

T1 weigthing

A

fat is white

water is black

51
Q

T2 weighting

A

water is white

fat is black

52
Q

white

A

high signal

53
Q

black

A

low signal

54
Q

uses of MRI

A

CNS - brain and spinal cord

Bones and joints

Heart and blood vessels

Internal organs

55
Q

Advantages of MRI

A
  • no radiation
  • Good contract resolution
56
Q

Disadvantages

A
  • Time consuming
  • Expensive
  • Limited availability
  • Some patients won’t fit
  • Claustrophobic
  • Loud
  • Need to lie still
  • Metalwork
57
Q

scintigraphy (nuclear medicine)

A
  • Injection radiopharmaceuticals
  • Emit gamma rays which an be detected
  • Highly sensitive
  • Functional and anatomical info
58
Q

example of imaging that uses scintigraphy

A

Positron emission tomography (PET)

59
Q

PET scan overview

A
  • Radionuclides that decay by positron emission
  • Bound to glucose
  • PET cameras detect high energy gamma rays (annihilations) - the more annhiliation the bigger the signal
  • Used in combination with CT/ MRI
  • Hot spots= areas of high glucose metabolism (heavily used in oncology)
60
Q
A
61
Q

how do ultrasounds work

A
  • High frequency sound waves from transducer probe
  • This sound wave is reflected back by tissues where densities (impedance) differs
  • Probe defects reflected sound waves

Creates electrical signal

  • Determines distance- time taken to come back
  • Determine impedance- proportion of reflected waves
62
Q

in US hyperchoic

A

more reflective= white

63
Q

in US hypoechoic

A

less reflective= dark grey

64
Q

in US anechoic

A

not reflective (pure fluid (black))

65
Q

duplex ultrasound

A

= 2D and doppler

66
Q

uses of ultrasound

A
  • Can be used in body cavities e.g. transvaginal, transrectal and transoesophageal
  • Solid organs- liver, kidney, spleen, pancreas, thyroid
  • Urinary tract- stone, dilation, volume
  • Obs and gynae- pregnancy and uterus
  • Musculoskeletal
67
Q

advantages of ultrasound

A
  • Lacks ionising radiation
  • Low cost
  • Portable
  • Can be inserted into body cavities
  • Babies
  • Dynamic (blood flow)
68
Q

disadvanatges of ultrasound

A
  • Operator dependant
  • No bone or gas penetration
  • Body habitus
69
Q

myelination in peripheral neurones

A

1) Axon sitting in a groove surrounded by a schwann cell
2) Mesaxon membrane initiates myelination by surrounding the embedded axon
3) A sheet-like extension of the mesoaxon membrane then wraps successively around the axon- forming multiple membrane layers
4) Cytoplasm is extruded between the two apposing plasma memebranes of the schwann cell, which become compacted to form myelin (19-20 round)

70
Q

outer mesaxon

A

invaginated plasma membrane extending from the aboaxonal surface of the schwann cell to the myelin

71
Q

inner mesaxon

A

extends from the adaxonal surface of the schwann cell (part facing the axon) to the myelin

72
Q

oligodendrocytes

A
  • Does the same thing as shwann cell but in the CNS
  • Cytoplasmic processes from the oligodendrocyte cell body to form flattened cytoplasmic sheaths that wrap around each of the axons
73
Q

difference between oligodendrocytes and schwann cells

A

wraps around more than one axon simultaneously

74
Q

Unmyelinated nerve cells

A

Slower propagation of action potential

75
Q

support cells of the CNS

A
  • oligodendrocytes
  • astroctes
  • microglial cells
  • ependymal cells
76
Q

astrocytes

A
  • Star-like structure
  • Have ‘perineural feet’ that contain gap junctions
  • Biochemical support for endothelial cells
  • Transport of nutrients (lactate) from blood to nerve cells
  • Regulate nerve impulses by releasing glutamate
  • Contribute to the BBB
77
Q

microglial cells

A
  • Large cell with elongated nucleus and relatively few processes emanating from cell body
  • Found throughout the CNS
  • Resident macrophages
  • Immune function
    • Remove damaged nerve cells
    • Digest protein tangles associated with senile dementia and Alz
  • Sense increase K+ ions
78
Q

ependymal cells

A
  • Line the spinal canal and the ventricular of the brain
  • Look like columnar epithelial cell lining of spinal canal and ventricles (CSF) of the brain
  • Joined by junction complex (JC) that separates the lumen of the canal from the lateral intercellular space
  • Apical surface has both cilia and microvilli
  • Function:
    • Synthesise and secrete CSF in the ventricles
    • Cilia move CSF through ventricles to the spinal cord
    • Microvilli absorb CSF for removal of pathogens
      • Present pathogens to microglial cells and astrocytes
  • Modified tight junctions between epithelial cells control fluid release into the brain
79
Q
A
80
Q

Mulitiple sclerosis

A
  • Remitting and relapsing disease
  • Degenerative
  • Caused by autoimmune degradation of myelin
  • Symptoms caused by loss of conduction velocity
81
Q

symptoms of MS

A

fatigue, vision problems (Diplopoda), slurred speech (dysarthria), numbness and tingling sensation (paraesthesis), mobility issues (muscle spasms), urinary retention, constipation

Body logistics (39 decks)

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