Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Principles > Radiology > Flashcards

Radiology Flashcards

1
Q

What is imaging?

A

All the tests that doctors use to see things inside the body that they can’t see or feel from the outside.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What tests are imaging tests?

A

Xrays

  • plain radiography
  • contrast studies (barium enema, arthrography)
  • computed tomography (CT)

Ultrasound

Magnetic resonance imaging (MRI)

Nuclear medicine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are x-rays?

A

Electromagnetic radiation produced by an electrical source which pass through body tissue to a degree dependent on its density.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the mechanics of producing an X-ray?

A
  • Electric current heats filament cathode
  • electrons are emitted and strike anode
  • generated X-rays exit window in casing and beam is collimated (so we can aim where we want to see)
  • x-rays penetrate patient and scatter
  • only 1% of x-rays reach the film and contribute to the image
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Why does scattering lead to concerns for imaing safety with X-rays?

A

We want to minimise the dose to the patient and staff so need to use precautions such as led lined rooms and aprons, etc.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Why are x-rays increasingly taken digitally?

A
  • When on film they often went missing
  • over and under exposure meant repeats often required
  • post-exposure manipulation reduces the need for repeats
  • PACS (picture archive and communication system) allows easier storage, access and retrieval of digital images (x-ray, CT, etc)
  • This can also be used by different people at the same time, allows sharing of expertise etc.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

The _______ a tissue the fewer X-rays pass through it.

A

Denser

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Due to their relative densities how many X-rays can pass through air, soft tissue and cortical bone?

A
  • Air lets all X-rays pass through
  • Soft tissue lets some X-rays pass through
  • Cortical bone lets no X-rays pass through
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the picture produced in an X-ray dependent upon?

A

X-ray film is blackened when x-rays hit it, so the picture is produced depending on what the x-rays have to pass through.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are X-rays good at showing?

A
  • Things surrounded by black air e.g. lung cancer
  • Things surrounded by white bone e.g. fractures
  • Things that destroy white bone e.g. bone cancer
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the main weakness of X-rays?

A
  • To be visible on a simple x-ray, an abnormality must be of very different density to the tissue that surrounds it
  • A lot of pathology, especially that effecting soft tissues, is of similar density to its surroundings and isn’t shown by simple x-rays
  • if two things are the same density you cannot tell where one starts and the other stops
  • 2D representation of a 3D strutcure so when there are many structures overlying x-rays will have weakness.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is a contrast study and the theory behind it?

A
  • contrast studies- application of an additional substance which is more or less dense than the substance adjacent to it.
  • liquids containing dense elements like barium or iodine can block x-rays
  • by putting them in the spaces between tissues, the tissue outlines become visible because the difference in density between two adjacent stuctures has been increased.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Give two examples of contrast studies

A
  • Barium enema in the colon
  • Arthrogram- direct injection of iodine rich fluid in a joint
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Why can X-rays be dangerous?

A

X-rays are radiation so can damage cell DNA leading to mutations which may kill the cell or make it turn cancerous.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the risk of X-rays related to?

A

X-ray dose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What does the IRMER (ionising radiation medical exposure regulation) 2000 state?

A
  • the benefit to patients must always outweigh the risk

Also hospital staff have no benefit from x-rays so must be protected

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Radiographs have limited ________ resolution and struggle to resolve different ____ tissue structures.

A
  • contrast
  • soft
18
Q

Describe why CT is better than radiographs

A
  • sophisticated way of using X-rays to produce images
  • More able than radiographs to distinguish between tissues of similar density and is often used to show tissue pathology
  • superior contrast resolution conpared to a radiograph
19
Q

How does a CT scan work?

A
  • Rotating x-ray source which moves around the patient coupled with a detector
  • x-rays are passed through the patient at various angles and picked up at various angles
  • advanced computer algorithm reconstructs the image to allow a cross sectional image
20
Q

Why are radiographs not sufficient to diagnose illness?

A

When obtaining a radiograph, the x-rays are ‘fired’ from only one direction producing an image where all structures between their source and the film are superimposed.

21
Q

How does CT overcome the issues with superimposition on a radiograph?

A

With CT, x-rays are ‘fired’ from all around the body and processed by a computer which produces a set of cross sectional pictures with no superimposition.

22
Q

Why does everyone not just automatically get a CT scan over a radiograph?

A
  • Gives large doses of ionising radiation (chest CT = 250 CXR)
  • soft tissues of very similar density cannot be distinguished by CT
    • pelvic organs (uterus, ovaries, prostate)
    • joint cartilage and ligaments
    • some areas of the brain
  • CT cannot resolve bone marrow disease
23
Q

What are the benefits of ultrasound and MRI over CT and X-ray?

A
  • neither employ ionising radiation
  • both can show pelvic organs
  • both can show muscles and tendons
  • MRI can show joints and bone marrow disease
  • MRI can show all areas of the brain
  • ultrasound is quick to do, easy for patients, completely safe and doesn’t rely on a £1.5million scanner to generate images.
24
Q

How does an ultrasound work?

A
  • piezoelectic crystals can convert electrical energy to acoustic energy
  • these crystals are housed in a transducer which has an electrical supply
  • the transducer produces pulses of sound waves
  • the skin is coated with jelly to assist sound transmission into the body
  • the transducer alternately transmits sound pulses and then listens for reflected sound returning
  • the returning accoustic energy is converted back into an electrical impulse and fed into a computer.
  • the computer ‘knows’ where the sound has come from by the time taken for it to return to the transducer
  • it uses this to create a cross-sectional picture of the soft tissues invisible to x-rays
25
Q

On what principle do ultrasounds work?

A

Body tissues have different accoustic properties- some tend to transmit sound while others tend to reflect it.

26
Q

How do fluid and soft tissues appear on US and what is this to do with their accoustic properties?

A

Fluid appears very black and allows sound to go all the way through.

Soft tissues reflect sound back to transducer and appear lighter.

27
Q

Ultrasound images are obtained _______________. During US, the diagnosis is made durig the scan, not afterwards.

A

intantaneously

28
Q

How can US scanner produce a complete survey?

A

By moving the trasnducer over the skin, the sonographer ‘sweeps’ the US beam thorugh the body tissues allowing for a complete survey.

29
Q

What makes a good ultrasound exam?

A
  • tissues that allow sound transmission
  • lots of sound reaches the target and returns to the transducer
    • good skin-transducer contact
    • superficial structures
    • slim patients
    • correct transducer selection
  • Tissues which have different accoustic properties (reflect different amounts of sound)
  • a well trained and experienced sonographer
  • modern equipment
30
Q

What makes a poor ultrasound exam?

A
  • tissues that prevent sound transmission (gas, bone)
  • sound can’t reach the target or return to the transducer
    • poor skin-transducer contact (not enough jelly, hairy)
  • tissues which have identical accoustic properties (reflect the same amount of sound)
  • an incompetent operator
  • antique equipment
31
Q

State 4 ultrasound strengths

A
  1. High spacial resolution, useful in imaging MSK soft tissue sturtcures- tendons and muscles
  2. body fluids readily transmit ultrasound whereas solid structures within the fluid reflect it.
  3. abnormal fluid collections are well shown e.g. pleural effusion, ascites, abscess, cytsts.
  4. soft tissues with different accoustic properties are well differentiated- soft tissue tumors
32
Q

What are 3 weaknesses of ultrasounds?

A
  1. bone blocks US, so it can’t see the brain, the spinal canal, inside joints or ascess bone marrow
  2. Gas blocks US, so ‘windy’ patients are difficult to assess and gas containing structures like the lungs or bowel can’t be assessed.
  3. Very fat patients make poor US subjects
33
Q

What happens in an MRI?

A
  • MRI creates a strong magnetic field
  • the scanner produces a burst of radio signal (RF pulse), which energises the body’s protons
  • the scanner waits
  • scanner listens for a return signal, produced by the protons
  • the amount of signal produced depends on the molecular movement of these protons
  • using the returned signal, the scanners computer peforms some amazingly complex calculations and creates an image.
34
Q

How is the magnetic fields in an MRI produced?

A

Magnetic field results from electrucal current passed through coiled metal wire surrounding the bore and relies on superconduction of current which occurs at very low temperatures, maintained by liquid He

35
Q

What are the dangers of an MRI scanner?

A
  • superconducting magnet
  • Very low temperature helium
  • frostbite and thermal burns
  • deafness
  • disturbance of surgical and non-surgical ferrous material
    • pacemakers
    • heart valves
    • mobile ferrous material eg shrapnel, intra-ocular foreign bodies
    • missile injuries
36
Q

What are the 4 rules around staff and MRI equipment?

A
  1. security keypad lock at entrance to MR suite
  2. all staff are vetted before entry to MR scanner room is permitted
  3. only MR approved cleaners, engineers, anaesthatists and equipment are allowed into the MR suite
  4. staff must remove watches, credit cards, metal keys etc before entering MR room
37
Q

How is patient injury prevented around MRI scanners?

A
  • request card safety questionnaire
  • patients must remove all ferrous metal, including dental plates, ear rings, belly button studs, belts, keys, etc
38
Q

What are the 4 strengths of MRI?

A
  1. MRI provides the most complete assessment of the brain of any modality
  2. It is a sensitive way to assess acute muscle and tendon tears, especially in deep tissues where US is less accurate.
  3. Provides excellent detail of spinal canal disease
  4. Allows the interiors of joints to be imaged, so injuries to cartilage and ligaments can be seen.
39
Q

What are some (5) weaknesses of MRI scanning?

A
  1. Expensive
  2. could harm some patients and so is contraindicated
  3. some patients find MRI too claustraphobic
  4. MRI scans take a long time so patients who are in pain or are restless, or those who are unstable and need monitoring can’t be scanned
  5. Poor at showing detail of the lungs
40
Q

What does imaging often provide even if immediate symptoms have been treated in a patient?

A

A diagnosis

41
Q

What is the role of clinical imaging?

A
  • To make or confirm a diagnosis
  • To help narrow a differential diagnosis
  • To ‘stage’ a known disease e.g. cancer to inform treatment
  • To monitor the effects of treatment and follow up a known disease
  • To aid intervention/deliver treatment e.g. image guided procedures or interventional radiology
    *

Principles (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions