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Body log > Radiology > Flashcards

Radiology Flashcards

1
Q

How does an x-ray work

A

Focused beam of high energy electrons
These can pass through the body onto receiver
But some are absorbed or scattered (attenuation- the higher the density and atomic number the higher the attenuation
Depends upon density and atomic number (metals)

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2
Q

What are the principle densities?

A 
Air 
Fat 
Soft tissue 
Bone 
Metal
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3
Q

How to read a CXR

A 
AIR
Breathing
Circulation
Disabilities (bones
Everything else
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4
Q

How to read a AXR?

A

AIR
BOWEL
DENSITIES (BONES)
ORGANS

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5
Q

How to read orthopaedic film

A

Fractures - displacement

Bony abnormality - bone quality

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6
Q

Advantages and disadvantages of X-ray

A 
Advantages 
Quick 
Simple 
cheap
Portable 
Disadvantage
Ionising Radiation (low)
Poor soft tissue imaging 
One plane two dimensional 
Cant visualise all areas
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7
Q

Uses of x-ray

A

Chest
Bowel
Orthopaedic

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8
Q

What occurs in fluoroscopy?

A

Examination of anatomy and motion.

Uses constant steam of x-rays

Often enhanced by contrast

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9
Q

What are the contrast used in fluoroscopy?

A

Barium, iodine or gadolinium (MRI)

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10
Q

What are the uses of fluoroscopy?

A

Angiography
Contrast GI studies
Screening in theatre

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11
Q

What are the two cross sectional imaging?

A

CT

MRI

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12
Q

What occurs in CT ?

A

There is a rotating gantry

X-ray tubes on one side
Detectors on the other side
The patient lays in the trolly, then they will pass through it as the gantry spins around them.

Images put together by computer

Same principle of attenuation as x-ray

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13
Q

What are Hounsfield Units (HU)?

A

Ability to distinguish densities in CT scans

Less dense = negative HU
E.g. air (more negative) and fat

More dense = positive HU
E.g. bone and metal

Water = 0HU

Pg29

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14
Q

What are the advantages and disadvantages of fluoroscopy?

A

Advantages
Dynamic studies
Cheap interventional procedures

Disadvantages
Clinician exposure must be minimised
Radiation

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15
Q

Advantages and disadvantages of CT scans?

A

Advantages

Quick
Good spatial resolution
Can scan most areas

Disadvantage

Radiation
Affected by artefacts
Requires holding breathe
Lower contrast resolution

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16
Q

Uses of CT Scans

A

Diagnosis e.g. cancer, stroke

Guide further test or treatment e.g. biopsy and radiotherapy

Monitor condition e.g. cancer treatment

17
Q

How does an MRI work?

A

Strong magnetic field , aligns hydrogen atoms

Some point towards the head and some towards the feet and unmatched ions remain (creating a bit of an overall polarisation).

Radio frequency pulse applied

Unmatched ions absorb energy and spin in different directions

Pulse is turned off and atoms spin returns which emits energy ( the atoms that were unmatched and absorbed the energy will release the energy again abs the computer will detect this energy and create an image.

Computer processing to generate image

18
Q

What is needed in an MRI?

A

Image quality relies on magnetic field

Narrow gantry

19
Q

What are the specifics of MRI weighting?

A

Relaxations (when you turn off radio frequency pulse, provides different weighting for tissue).

Different relaxations produce different weighting’s from tissues

20
Q

What is T1 and T2?

A

T2 weighting : Fat is white, water is black
T2 weighting: Water is white, fat is black

T2 = High signal water 
T2 = Water 
White = High signal 
Black = Low signal
21
Q

Uses of MRI’s

A

CNS - Brain and Spinal cord

Bones and joints

Heart and blood vessels

Internal organs

22
Q

Advantages and disadvantages of MRI

A

Advantages
No radiation
Good contrast resolution

Disadvantages 
Expensive 
Time consuming 
Metalwork + artificial joints and pacemakers are now MRI safe, due to the magnetic field some things can be ripped out of the body at very high forces 
Claustrophobic 
Some patients don’t fit
23
Q

What is Scintigraphy (Nuclear Medicine)

A

Injection of radio pharmaceuticals
Emits gamma rays - which are detected

Highly sensitive
Functional and anatomical information - often combined with MRI and CT Scans

24
Q

How does Positron Emission Tomography (PET) work?

A

Insert radionuclides that decay by Positron emission
Bound to glucose

PET scan detect annihilations (high energy gamma rays)

  • More annihilation’s the bigger the signal
  • Tends to be combined with CT/MRI

Hot spots - Areas of high glucose metabolism

25
Q

What are the uses of PET scans?

A

Heavily used in Oncology

  • Tumour staging
  • Assessment of treatment
  • differentiating between benign and malignant
  • detects tumour recurrence
26
Q

How does ultrasound work?

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

Creates electrical signals:

  • Determined distance - time to come back
  • Determined impedance - proportion of reflected waves
27
Q

How are waves seen on ultrasounds?

A
  • Hyperchoic = more reflective = white
  • Hypoechoic = Less Reflective = Dark grey
  • Anechoic = Not Reflective (pure fluid) = Black
28
Q

What are the specifics of Doppler Ultrasound?

A

Moving objects influence sound waves

Therefore flowing blood can affect ultrasound signal

  • Coming towards - Increased Frequency
  • Going Away - Decreased Frequency
29
Q

Uses of ultrasound

A

Solid organs
Obs and gynae
Urinary tract
Musculoskeletal

30
Q

Advantages and disadvantages of Ultrasound

A

Advantages

  • Lack of ionising radiation
  • Low cost
  • portable
  • Dynamic flow

Disadvantages

  • Operator dependant
  • no bone or gas penetration
  • Body habitus - harder to use on patients with more fat
31
Q

Why is contrast media needed?

A

Helps in better differentiation of tissues
Various different types based on modality of examination

Most commonly used in:

  • Fluroscopy
  • CT
  • MRI
  • Arteriograms
  • Ultrasound
32
Q

Types of contrast media

A
  • Positive: Barium, iodine, Gadolinium
  • Negative: water, air and CO2

Sodium iodide is only used in contrast agent
Barium sulphate is used in GI Imaging

33
Q

What is the Ideal contrast media?

A
  • Low osmolality and viscosity
  • High water solubility
  • Biologically inert
  • Safe
  • Heat and chemical stability
  • Cost effective
34
Q

What are the different ways Contrast media can be administered?

A
  • Oral
  • Rectal
  • IV
  • IA
  • Filling a space or cavity (cavity, bladder, gall bladder)
35
Q

What is the important aspect of excretion of contrast media?

A
  • the patient needs to have good kidneys and the kidneys have to be functioning well because contrast media could cause risks (renal failure or complications).
  • Glomerular filtration - 95%
  • Tubular excretion and protein binding negligible
  • Half life: 30-60 minutes - it doesn’t last long, it needs to be done in appropriate time
36
Q

What are the side effects of contrast media?

A
  • Reactions due to osmolality
  • Endothelial damage - occasionally causes below
  • Thrombosis and thrombophlebitis

Which can lead to

  • Vasodilation
  • Vascular pain
37
Q

Disadvantages of contrast media

A

Idiosyncratic reactions - within 20 minutes - unpredictable

  • mild
  • moderate
  • severe - 0.03% -true allergic reactions are extremely rare

Non idiosyncratic reactions - predictable

  • Cardiac
  • Nephrogenic
  • Extravasations
  • delayed reactions - beyond 30 min - 7 days

Body log (13 decks)

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