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Year One - Principles of Disease > Imaging > Flashcards

Imaging Flashcards

1
Q

What is an X-Ray?

A

An electromagnetic packet fo energy with an extremely short wavelength between 0.1 and 10nm.

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2
Q

What is electromagnetic energy comprised of?

A

Quantum energy (photons)

Waveform energy (transverse waves)

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3
Q

How do X-Rays interact with dense matter, like bone?

A

Absorbed

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4
Q

How do X-Rays interact with air?

A

Completely transmitted

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5
Q

How do X-Rays interact with matter between densities of bone and air (soft tissue or fat) ?

A

Scattered

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6
Q

What is attenuation?

A

The process by which radiation loses power as it travels through matter and interacts with it.

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7
Q

What increases attenuation?

A

Atomic no.

Density

Thickness

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8
Q

How do ultrasounds work?

A

Transmit high frequency sound waves that travel into the body and hit a boundary between tissues, between soft tissues and fluid and between soft tissue and bone.

Some of the sound waves get reflected back to the probe, while some travel on until they reach another boundary and are reflected. The reflected waves are picked up by the probe and relayed to the machine. The machine calculates the time of each echo’s return to create a 2-D image.

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9
Q

What does CT scans involve?

A

A rotating X-ray tube and multiple beams.

Give iodinated contrast to the patient prior to the scan, which can be administered IV or orally.

However, IV administration can lead to kidney failure

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10
Q

What is radiation?

A

Process of emitting energy in the form of either particles of waves

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11
Q

What is ionising radiation?

A

A particle or wave with sufficient energy to ionise a neutral atom or molecule and leave them with a charge.

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12
Q

What can ionising radiation lead to?

A

Disruption of chemical bonds within DNA.

This can lead to altered cell metabolism and function - can lead to cancer development

Cell death - ONLY if the rate of cell death exceeds rapid ability, effects are present

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13
Q

What cells are more likely to be affected by ionising radiation?

A

Rapidly dividing cells

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14
Q

What does a sievert unit measure?

A

The absorption of radiation by the human body

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15
Q

Do different types of radiation have varying abilities to penetrate different materials?

A

Yes

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16
Q

How can we minimise our exposure to radiation?

A

Being as far from the radiation as possible

Minimise the time staff and patients are exposed to the radiation for

Wearing a shield

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17
Q

What does functional imaging detect?

A

Changes in physiological activities within a certain tissue or organ through the use of traces and probes

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18
Q

What are tracers attached to in functional imaging? Why?

A

Isotopes

Have similar chemical and biological characteristics

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19
Q

What does molecular imaging detect?

A

Changes in molecular pathways using biomarkers

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20
Q

Why are biomarkers used in molecular imaging?

A

Interact chemically with their surroundings and therefore detect changes within it

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21
Q

What are the five types of molecular imaging?

A

Radionuclide

SPECT

PET

MRI

Optical

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22
Q

What is radionuclide imaging?

A

The production of internal body images by cameras thet detect the radioactive emissions of an injected radionuclide as it moves through the body

23
Q

What are the properties of an ideal isotope used in radionuclide imaging?

A

Half-life similar to the length of examination

Emit gamma radiation (50-300 keV)

Readily available

Bind to a pharmaceutical component easily

Excreted shortly after examination

24
Q

What common isotope is used in radionuclide imaging? Why?

A

99m Technecium

Accumulates in different proportions in different tissues

25
Q

What are radionuclides composed of?

A

Radioactive element

Pharmaceutical element

26
Q

What is the role of the radionuclide in radionuclide imaging?

A

Taken up by the organs in the body and then emit gamma ray signals which are measured by a gamma camera.

The gamma camera detects radiation and converts it into light, then an electrical signal, which is digitised and reconstructed into an image by a computer.

27
Q

What is the wavelength, frequency and energy of gamma radiation?

A

Low wavelength

High frequency

High energy

28
Q

What four factors affect image quality in radionuclide imaging?

A

Radiation dose

Collimator

Metal objects

Proximity of area to camera

29
Q

What does SPECT involve?

A

Mapping the distribution of radioisotopes in the organ or tissue using radiotracers

30
Q

What is the role of radiotracers in SPECT?

A

Taken up by organ or tissue and emit gamma rays which are detected by a rotational gamma camera.

The gamma camera detects radiation and converts it into light, then an electrical signal, which is digitised and reconstructed into a 3D image by a computer.

31
Q

What does PET involve?

A

Produces a 3D image of functional process in the body using a molecule that is tagged with a positron emitting isotope

32
Q

What is the role of the position emitting isotopes in PET?

A

These positrons annihilate with nearby electrons, to emit two gamma rays directed 180 degrees apart in opposite directions. These rays are then detected by the scanner.

33
Q

What is the most common isotope used in PET? Why?

A

18F

Suitable half-life time

Strong enough to produce a good image

Decays quickly after use

Binds to glucose easily, which is taken up by all metabolic cells but cancerous and inflamed cells will take up more as they require more energy

34
Q

What is barium sulphate used for?

A

Outlining the GI tract on scans

35
Q

Why is barium sulphate a radio-opaque contrast?

A

It has a high atomic number which means that it absorbs more X-rays than surrounding tissues and appears white and and opaque on scans

36
Q

Why is barium sulphate used?

A

Does not interact with the body

Easy to identify

37
Q

What is a barium swallow administration? What is it used to visualise? How are patients prepped for this administration?

A

Barium is administered as a meal.

Oesophagus, stomach and duodenum

Fasting for 4-6 hrs before

38
Q

What is a barium follow-through used to visualise? How are patients prepped for this administration?

A

Small bowel

Fasting for 4-6 hrs before

39
Q

What is a barium enema used to visualise? How are patients prepped for this administration?

A

Large bowel

Low residue diet 48 hours prior and they usually undergo bowel cleansing with Picolax

40
Q

What is the difference between single and double contrast imaging?

A

Single - allows you see the outline of the tissue/organ

Double - allows you to look inside tissue/organ, useful to visualise tumours

41
Q

How do CT scans work?

A

The computer knows the exact number of photons it releases and the receptor on the other side detects how many photons reaches it. The number sent vs the number received is what determines the shade of grey that the organ appears on the scan.

42
Q

How are iodine-based contrast agents in CT scans administered?

A

Orally - outline GI tract

Intravenously - visualise blood vessels or the vascularity of different tissues

43
Q

How do CT scans detect the stage of cancer?

A

Visualise whether the cancer has spread locally or distantly

44
Q

What do MRI scans involve?

A

MRI scans use radio frequency to displace protons, which are normally aligned in one direction by strong magnetic fields. The images are created by displaying the time taken for the protons to relax back to their original aligment.

45
Q

What are the disadvantages of MRI scans?

A

Unpleasant for the patient

Cannot be used in patients with pacemakers and aneurysm clips

46
Q

What is the contrast agent used in MRIs?

A

Gadolinium DTPA, which causes changes in the local magnetic field.

47
Q

What is t-staging? What does it allow? What two stages have the worst prognosis?

A

Tumour staging. A realistic prognosis to be made.

Cancers at stage four and three have a poor prognosis compared to cancers at stage one and two.

48
Q

What is tumour staging based on?

A

Position of the tumour, tumour depth, tumour relationship to adjacent structures, involvement of lymph nodes and the presence of distant metastases

49
Q

What are PET scans not used to image?

A

Brain

Spinal cord

50
Q

What are CT scans not used to image?

A

Spinal cord

51
Q

What are MRI scans not used to image?

A

Organs/tissues within the body that move, like stomach or the oesophagus

52
Q

What does screening allow?

A

Earlier diagnosis before symptoms are present.

Cancers detected at this stage are easier to treat and more likely to be curable.

53
Q

What three screening programmes are set up by the NHS?

A

Breast

Bowel

Cervical

54
Q

What are the requirements of screening tests?

A

Detect disease at an early stage

Cause no harm and be specific

Benefits should outweigh the cost to the individual and the population

Year One - Principles of Disease (15 decks)

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