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Cellular Pathology > X-Ray, CT, PET > Flashcards

X-Ray, CT, PET Flashcards

1
Q
  1. What are 6 examples of imaging with radiation?
A 
Ionising Radiation
Planar X-ray
CT
Gamma Camera and SPECT
PET
Hybrid Imaging
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2
Q
  1. What is ionising radiation?
A

Radiation that causes ionisation when it interacts with matter, it’s used due to it’s penetrative ability.

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3
Q
  1. What are the two types of ionising radiation used for medical imaging?
A

Gamma rays

X-Rays

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4
Q
  1. What is the INDIRECT radiation action?
A

Radiation breaks down water into highly reactive free radicals (charged) that impart energy on cells.

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5
Q
  1. What is the DIRECT radiation action?
A

Radiation directly affects DNA by breaking it down.

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6
Q
  1. What do both indirect and direct radiation lead to?
A

Both lead to mutations which cause biological responses e.g. death, cancer, or changes to the genetic code (may not affect us but are passed on).

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7
Q
  1. Does increased radiation dose proportionally increase damage risk?
A

Yes

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8
Q
  1. What are two indirect risks of radiation?
A

Risk of cancer induction and risk of genetic change in subsequent population

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9
Q
  1. What are some direct effects of radiation?
A

Erythema (Skin Burn)

Hair loss

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10
Q
  1. What is the threshold effect? What is the consequence of this?
A

•Threshold effect: Only at high radiation dose not noticed at usual diagnostic doses.
oMedical imaging designed to be very low (below the threshold and low risk

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11
Q
  1. What is the risk of fatal cancer induction?
A
  • 5% per Sievert, 1 in 20000 per mSv,

* 1 in 2000 per PET scan.

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12
Q
  1. What is the annual radiation dose in the UK average?
A

2.7 mSv

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13
Q
  1. How are positrons used in PET scanning?
A

Positive electrons interact with matter to create gamma rays

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14
Q
  1. How are Gamma Rays used in Gamma camera imaging eg SPECT?
A

Penetrating radiation

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15
Q
  1. How are X-Rays used in X-Ray imaging eg radiographs, CT?
A

Spectrum of electromagnetic

radiation

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16
Q
  1. What is similar between Positrons and Gamma rays
A

Emitted following the radioactive decay of an unstable nucleus

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17
Q
  1. How are X-Rays different to Positrons and X-Rays
A

Artificially produced in an X‑ray tube

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18
Q
  1. What is attenuation and what does increase with?
A

o Attenuation (tissues with ability to block the x-rays) increases with higher atomic number and a higher density.

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19
Q
  1. X-rays are essentially an attenuation map, we can use them to see bone and air- how?
A

X-rays pass through air in the lungs most easily and then muscle, doesn’t pass through bone very well.

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20
Q
  1. How do we achieve a transmission map , what is it useful for?
A

o Radiation is directed through the patient and a transmission map is collected (attenuation map).
o Good at showing structure, especially between tissues of different densities or atomic number

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21
Q
  1. What is Emission Imaging?
A

o Radiation is administered to a patient in the form of a tracer and the radiation emitted outside the patient is detected.

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22
Q
  1. What is the process of X-ray tube?
A

oThere is a voltage difference between the filament and target in the vacuum tube.
When a current is applied, electrons are fired from the filament to the target. A beam of x-rays is produced when the electrons hit the target.
oControl of the amount/energy of x-rays produced: High voltage controls the energy of the x-rays while current control the amount of x-rays.
oX-rays only produced when tube is in action (switched on/off).

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23
Q
  1. How can we use X-rays to diagnose?
A

Fractures eg clavicle, radius, phalanx

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24
Q
  1. How do we use low dose dental radiology to diagnose areas of tooth decay and infection?
A

Areas of tooth decay and Infections look darker than bones because they don’t absorb as much x-rays

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25
Q
  1. Why would you need to do a chest X-Ray?
A

We can test for pulmonary embolism (wedge-shaped defects) however its only seen on X-Ray when its large
Also test for Squamous Cell lung cancer.

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26
Q
  1. What is Mammography?
A

process of using low-energy X-rays to examine the human breast for diagnosis and screening.

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27
Q
  1. Very briefly explain the process of mammography?
A

A compression plate is used to reduce breast thickness – this improves resolution and lowers the radiation dose (used as a screening tool)

Breasts lay on cassette, compression plate on top of them, x ray tube above plate at face level.

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28
Q
  1. What are benign micro-calcifications and what do they look like on a mammogram?
A

Breast calcifications are small calcium deposits that develop in a woman’s breast tissue. They are very common and are usually benign (noncancerous)
look like white specks on a mammogram

29
Q
  1. What would you do if you found a dense speculated mass in the breast?
A

You would follow up with a biopsy

30
Q
  1. What is the process of real time X-Ray?
A

o Real-time imaging where a catheter is fed inside an artery and used to inject a opaque dye is injected.
o It shows blood flow inside vessels (e.g. occlusions) and can be used to assist with interventions.

31
Q
  1. What is Coronary angiography?
A

a procedure that uses a special dye (contrast material) and x-rays to see how blood flows through the arteries in your heart.

o Real-time imaging using an image intensifier called fluoroscopy
o It allows us to visualise blood vessel and soft tissue – treatment can be balloon angioplasty or stent insertion

32
Q
  1. What are some limitations of planar X-Ray?o
A

Cannot distinguish between overlying tissues and the tissues other than those being observed -reduce contrast in the image.
-Historically partially solved by moving the film cassette and X-ray relative to the patient to blur out overlying tissues, called “tomography” (from Greek “part/slice” - “write”).
o Superseded by Computed Axial Tomography, now abbreviated to CT.

33
Q
  1. What kind of image does a CT scanner produce?
A

Shows us a 3D image

34
Q
  1. Explain the anatomy of a CT Scanner?
A

Ok so basically the like tube around the patient is called the aperture/bore
On top of the aperture you have a fan beam and them like at the top of the whole CT scanner right above the head you can the X-ray tube

35
Q
  1. Approximately how many seconds per rotation in fast gantry rotation?
A

0.33 seconds per rotation

36
Q
  1. Compare Helical/Spiral scanning and Helical MSCT?
A

Helical/Spiral Scanning:

  • Continuous rotation and table feed
  • For every turn – 1 image/slice

Helical MSCT:

  • Multi-slice, faster scan and more coverage per rotation
  • For every turn: multiple slices.
37
Q
  1. How would you identify a haemorrhage in a CT scan?
A

Bright white blob/area

38
Q
  1. Why is an urgent diagnosis required if you’re testing for haemorrhage or blood clot?
A

Urgent diagnosis required for treatment because clot busting drugs may increase bleeding

39
Q
  1. Why would you use a CT scan to test for Haemorrhage or blood clot?
A

Better contrast and allows imaging of underlying tissue because it takes slices rather than 1 image.

40
Q
  1. How can we use CT to monitor disease progression?
A

oMeasurement of the size of the left inguinal lymph node shows progression of disease

oImaging is used for monitoring response to therapy

41
Q
  1. Why are CT effective at treatment planning?
A

o External beam radiotherapy normally irradiates normal tissue as well as tumour.
o Multiple beams can be used to spare normal tissue and only target tumour.
o CT is used to define area to be treated and the direction of the radiotherapy beams that are used.

42
Q
  1. What is the process of using nuclear medicine in emission imaging?
A
  • Inject radioactive tracer causing patient to emit the gamma rays
  • Produces an image of the distribution of the radioactive tracer.
  • Nuclear Medicine only shows function and is a functional modality (equipment providing structural/functional images).
  • It may reflect anatomy but without metabolism, the tracer will not be taken up – no image.
43
Q
  1. What does the image produced in emission imaging depend on?
A

Image depends on the metabolism of the tracer: this is functional Imaging (not anatomy).

44
Q
  1. Compare the kind of radionuclides used and images produced in Gamma camera and PET?
A

Gamma Camera:

  • Uses Single photon emitting radionuclides
  • Can operate in 2D (planar) or 3D (SPECT)

PET:

  • Uses Positron emitting radionuclides
  • Always 3D
45
Q
  1. What does PET stand for?
A

Positron Emission Tomography

46
Q
  1. How would you detect cancer in gamma camera imaging?
A

More tracer taken up —> More black dots

47
Q
  1. What is half life?
A

Time taken for the radioactivity to reduce to 50%

48
Q
  1. What is the equation for radioactive decay ?

What does each symbol mean?

A

A= A0e^(upside down y and then t)

A= Activity Remaining
A0= Initial Activity
t= Decay time
upside down y= Decay constant - half life

49
Q
  1. Following questions refer to gamma imaging :
    -Gamma camera’s have imaging **
    -Used for radionucleotides that decay with ** emission of *** rays
    ?
A

Gamma cameras have imaging “heads” and are used for radionuclides that decay with direct emission of gamma rays.

50
Q
  1. What is the most common nucleotide for gamma imaging?

What is its half life?

A

Tecnesium-99m

T1/2 = 6 hours

51
Q
  1. List the correct tracer used in gamma camera imaging for:
    -Bone
    -Kidneys
    -Infection/Immunity
    ?
A
  • Bone = Tc-99m MDP
  • Kidneys= Tc-99m DTPA
  • Infection/Immunity = Tc-99m White cells
52
Q
  1. How would you complete a Dynamic renal transplant scan?
A

o Camera positioned above the patient and Tc-99m DTPA is injected IV.
o Gamma camera records gamma rays and collects
o Functional Time –Activity curves are obtained

53
Q
  1. How would you complete a Single -photon Emission Computerised Tomography (SPECT):
A

o Acquire up to 64 images from around the head

o Reconstruction of transaxial (superior/inferior) slices.

54
Q
  1. Give a case scenario where SPECT identified issues that a usual planar bone scan couldn’t identify?
A

53-y-old man with NSCLC
=Planar Bone Scan=
No obvious defects

Same patient=SPECT Bone Scan (coronal view)=Lesions at lower and lumber spine

55
Q
  1. Explain the process of using the Datscan for Parkinsons disease?
A

o It uses SPECT agents that bind (Iodine-123 FP-CIT, Ioflupane) to the dopamine transporters (DAT) on the neurons.
o Parkinson’s disease: reduced uptake in the Putamen differentiates from Essential Tremor

56
Q
  1. Explain the process of beta+ particle radiation in PET?
A

o In PET, when positrons combine with electrons, they give out 2 gamma rays at 180o to each other. These are both detected within a short time (ns) and they define the ray path for reconstructing the image.
o After this, both positron and electron are annihilated.

57
Q
  1. Does nuclear medicine produce 1 gamma ray or 2 (like PET)?
A

Nuclear medicine only produces 1 gamma ray (not 2).

58
Q
  1. What is FDG? What do we use it to indicate?
A

o FDG is a glucose analogue which enters cells in the same way as glucose. This is why it’s a good reflection of the distribution of glucose uptake and phosphorylation by cells in the body.

59
Q
  1. What is FDG phosphorylated by? What is the consequence of this?
A

o Phosphorylation by hexokinase (creates FDG-6) traps the FDG, this causes increased uptake and retention in metabolically active tissue.

60
Q
  1. How can we use FDG to test for neurodegenerative dementia or pick’s disease?
A

FDG reflects metabolic activity
Alzheimer’s disease (hypometabolism, mostly in temporal and parietal regions)
Pick’s disease (fronto-temporal hypometabolism)

61
Q
  1. How does PET scanner work?
A

o A ring of scintillation detectors (flash of light produced in a transparent material by the passage of a particle) supported in a fixed gantry.
o Operated in “coincidence mode” - only photons emitted from an annihilation event are recorded.

62
Q
  1. List some examples of Ionising Radiation Imaging- small animal scanners:
A

o High resolution, CT, SPECT, PET

63
Q
  1. List some examples of Hybrid Imaging?
A

o PET-CT, SPECT-CT, PET-MR.

64
Q
  1. How do we use an exact location of the “hot spot”?
A

Fused PET & CT show the exact location of the “hot spot”

65
Q
  1. What is attenuation correction?
A

o Gamma rays originating from the centre of the patient will travel through more tissue which mean they are attenuated more
o The CT image is used as an attenuation map to correct the PET image.

66
Q 
66. Following questions are about DOSAGE:
What is it like for :
-Planar X-Ray
-CT
-Planar NM
-SPECT
-PET
A
  • Planar X-Ray = LOW
  • CT = HIGH
  • Planar NM = MEDIUM
  • SPECT = MEDIUM
  • PET = HIGH
67
Q 
67. Following questions are about COST:
What is it like for :
-Planar X-Ray
-CT
-Planar NM
-SPECT
-PET
A
  • Planar X-Ray = LOW
  • CT = MEDIUM
  • Planar NM = MEDIUM
  • SPECT = HIGH
  • PET = V.HIGH
68
Q 
68.  Following questions are about RESOLUTION:
What is it like for :
-Planar X-Ray
-CT
-Planar NM
-SPECT
-PET
A
  • Planar X-Ray = V. GOOD
  • CT = GOOD
  • Planar NM = POOR
  • SPECT = V. POOR
  • PET = MEDIUM
69
Q 
69.  Following questions are about CONTRAST:
What is it like for :
-Planar X-Ray
-CT
-Planar NM
-SPECT
-PET
A
  • Planar X-Ray = POOR
  • CT = GOOD
  • Planar NM = GOOD
  • SPECT = V.GOOD
  • PET = V.GOOD

Cellular Pathology (13 decks)

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