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POM - mine > 3 - Introduction to Imaging > Flashcards

3 - Introduction to Imaging Flashcards

1
Q

What should I know?

A
  1. How x rays are made
  2. The 2 main densities on x ray exams
  3. Which radiology exams use x rays
  4. Understand some of the other techniques used for investigations i.e. us, ct, nm, mri, pet
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2
Q

What did the discovery of x rays follow

A

Electricity, magnetism and importantly the ability to produce a vacuum within a glass tube

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3
Q

What 4 things does an x ray tube consist of?

A
  1. An electron source (the cathode)
  2. A strong accelerating force
  3. A vacuum within a glass (no air)
  4. Tungsten focal spot that creates x rays upon impact (the anode)
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4
Q

What are the 2 types of radiation created when tungston is bombarded with electrons?

A
  1. Braking Radiation (the e- whirls around the nuclei and is bent)
  2. Characterestic Radiation (e- hits another e- to an outer level)
    The energy given off by these forms x rays
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5
Q

Wavelength of xrays?

A

0.01nm - 0.1nm

Only gamma rays are shorter

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6
Q

When first discovered how did they enhance xrays

A

They put a photosensitive source under the body part and subsequently saw the shadows of bones

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7
Q

What kind of radiation is xrays

A

electromagnetic

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8
Q

What initially happened when people used xrays without control

A

Radio-necrosis

Was 5 years until it what recognised as dangerous

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9
Q

Grid?

A

Ensures that only the direct rays make it through to the film and the ones at weird angles that would blur the film are bounced out

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10
Q

What are the 4 x ray density levels (important)

A
  1. Calcium (bone) - white
  2. Water (tissue) - grey
  3. Fat - darker grey
  4. Air (lung/fundus) - black
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11
Q

What is the 5th density

A

Metal. Shows as white i.e. medical tools

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12
Q

How are x rays made

A
  • play a high electrical potential across and evacuated tube and pass a current through it
  • the resulting x rays penetrate tissue and densities to varying degrees and creates shadows
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13
Q

Why is viewing soft tissue structures less successful in xray

A

The difference in density and penetration and so shadowing of middle level tissues (fat, tissues, blood) is small

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14
Q

How may an x ray contrast be improved

A

Using less voltage like in a mammograph

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15
Q

Difference between radiographer and radiologist

A

grapher - takes x ray (medical imaging technologist)

ologist - interprets the x rays

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16
Q

X ray diagnosis (pros and cons)

A
  • good spatial resolution
  • limited contrast resolution
  • depicts differences in density via ranges of greys
  • can age and stage kids wrists
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17
Q

How many views do you do

A

at least 2 of every bone

18
Q

Why does the heart look radio opaque?

A

Bones behind it

19
Q

What does pneumonia look like on an x ray

A

Opaque (shouldn’t as should be filled with air and be black). Takes out whole lobe while a mass is more well defined (also get weight loss with a tumour)

20
Q

Completely white lungs?

A

Drowned and filled with water

21
Q

What does a pneumothorax look like

A

Air in pleural space so looks like lung has collapsed. If it is filled with fluid it is called a hydropneumothorax

22
Q

What is a pleural effusion?

A

Excess fluid build up around the lung. Looks like a great big white opacity at the bottom of the lung

23
Q

4 ways to increase contrast in x ray

A
  1. Barium sulphate
  2. Iodine
  3. Gadolinium (MRI)
  4. Air
24
Q

Barium Sulphate

A

Given by mouth, injected into gut, up rear (enemas) GI studies, no one is allergic to barium some people are allergic to iodine. Can see ulcers

25
Q

Iodine

A

Injected into BVs (angiography). 1/40 000 people die from iodine. Excreted by kidney so good to view.
Plain x rays and ct to enhance vessels and kidney

26
Q

Gadolinium

A

MRI. Injected. Used as iodine isn’t good in a magnet

27
Q

Air

A

Brain (encephalograms) - used to make air go into brain. Not used anymore as high mortality

28
Q

Haematuria?

A

RBCs in urine

29
Q

Presentation of kidney stones?

A
  • groins pain and haematuria
  • inject iodine
  • US in young CT in old
30
Q

Why use an angiogram?

A

With iodine. See if vessels still patent

31
Q

Nuclear medicine

A
  • radioactive substances are ingested or injected
  • gamma rays detected using a gamma camera
  • bone scans (goes to osteoblasts), thyroid scans, lung scans
  • head (stroke), bone, lung, thyroid, renal
32
Q

Ultrasound

A
  • short pulses of sound waves
  • piezo-electric crystal
  • images by the transmission or reflection of waves
  • inexpensive, safe, portable
  • but can’t penetrate bone and air containing structures
33
Q

How much does a US machine cost

A

more than $1 million probes $10 000

34
Q

US

A
  • produces 2d or 3d images
  • the location is determined by the time taken to receive the reflected signal
  • appearance is determined by differences in tissue impedence (Z)
    Z = pc
35
Q

In US what colour are vessels and the GB

A

Fluid is black as no sound waves reflected

36
Q

What is US used for

A 
abdominal pain
LFT
bumps/mass
swelling
renal dysfunction
vascular imaging 
cancer screening 
pregnancy
children 
pelvic pain 
ovarian pathology
scrotum
37
Q

CT (computed tomography)

A
  • xrays in transverse plain
  • cross sectional imaging
  • LESS spatial resolution than x ray but much better contrast resolution
  • added contrast with iodine
  • 300 xrays
  • blood is white
  • bowel obstruction
  • go to first for trauma
38
Q

When would you do a head ct

A

headache, dizziness, hemiplegia (paralysis on one side of body), trauma
- may be a haemorrhage (sudden severe headache and vomiting
)

39
Q

When would you do abd ct

A
  • when us not helpful
  • trauma
  • cancer
  • bowel obstruction
  • vascular imaging
40
Q

Magnetic Resonance Imaging (MRI)

A
  • uses magnetism in any plane
  • hydrogen nuclei within the body align with the mag field
  • added radiofrequency pulses change this alignment and energy is released when the protons realign to the mag field
  • no radiation
  • good brain pics
  • renal cancer
  • BOTH good spatial and contrast resolution
  • can get 3D images in any plane
  • expensive and takes a long time to set up and image
  • availability
  • contradictions (pacemakers, claustraphobia)
  • gadolinium used to increase contrast
41
Q

PET imaging

A
  • die with radioactive tracers
  • injected into veins
  • cancer soaks up and shows bright node at metastases
  • ## short 1/2 life

POM - mine (17 decks)

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