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RA6007 Advanced Medical Radiation Science > Nuclear Medicine > Flashcards

Nuclear Medicine Flashcards

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USMLE® Step 1 flashcards Biology 101 flashcards
1
Q

What is the main radionuclide used in Nuclear Medicine?

A

(Metastable) Technetium (Tc)

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2
Q

What produces Tc in the nuclear medicine department?

A

A generator made from parent atom Molybdenum (Mb)

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3
Q

what process is involved in Tc production

A

isomeric transition

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4
Q

what is isomeric transition?

A

the production of a gamma ray without any change in atomic mass or number

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5
Q

What is the half life of Technetium?

A

6 hrs

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6
Q

What does the generator consist of?

A

the generator is a lead lined container with the parent radionuclide

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7
Q

Where is the Mb in the generator?

A

It is adsorbed onto a column of alumina, silica or an ion-exchange resin

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8
Q

What is the eluate from a Technetium generator called?

A

Sodium
pertechnetate

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9
Q

Why do we need a generator?

A

Time available for processing, transporting, storage and dispensing is limited because of its short half-life

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10
Q

Advantages of Molybdenum as the parent radioisotope

A

Half-life of 66hrs which allows it to be transported easily without loss of activity
This allows the daughter radioisotope to be easily produced at the facility

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11
Q

how is the carrier free daughter eluted from the generator?

A

this is done by passing a solvent like saline over the column

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12
Q

what are some advantages of using Tc in Nuclear Medicine?

A

6hr half life
pure gamma emitter
easy to shield
easy incorporation with other chemicals
non-toxic
rapid excretion

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13
Q

How long does a typical generator last?

A

1 week

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14
Q

Technetium decays with the emission of…

A

a 140 kEv gamma
ray

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15
Q

What is transient equilibrium?

A

When equilibrium is reached by a parent-daughter radioactive isotope pair where the half-life of the daughter is shorter than the half-life of the parent.

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16
Q

What is Molybdenum breakthrough?

A

When tiny amounts of Molybdenum are contained in the solution of sodium pertechnetate

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17
Q

How is Mo breakthrough measured?

A

Comparing eluate activity with and without Pb shielding using a well counter

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18
Q

What imaging device is used in Nuclear Medicine?

A

Gamma camera

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19
Q

What is the gamma camera combined with?

A

a Collimator

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20
Q

What is the purpose of the collimator on the gamma camera?

A

to establish a relationship
between the distribution of isotope in the patient and the
position at which gamma rays are detected in the crystal

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21
Q

What is the gamma camera made of?

A

sodium iodide doped with thalium

22
Q

What effect does crystal thickness have on detector efficiency and spatial resolution?

A

The thicker the crystal, greater detector efficiency but lower spatial resolution

23
Q

The amplitude of the signal detected in the PM tube is proportional to what?

A

The amplitude of the signal detected is proportional to the amount of light emitted

24
Q

The light emitted is proportional to what?

A

The light emitted is proportional to the energy of the gamma ray

25
Q

What is the Z pulse?

A

the summation of the PM tube outputs provides an energy, which is proportional to the total light produced in the crystal

26
Q

Where does the Z pulse go?

A

to the pulse height analyser (PHA)

27
Q

What does the Pulse Height Analyser do?

A

PHA selects the isotope peak & excludes compton scatter

28
Q

What is the Z pulse proportional to?

A

The Z pulse is proportional to the total light output from one scintillation

29
Q

what happens if Z pulse is accepted?

A

the positional circuitry is triggered to locate the gamma ray interaction

30
Q

what is the PHA purpose?

A

choice of photo peak
exclude compton scatter

31
Q

What is the goal of Nuclear Medicine?

A

To map the distribution of radiotracers

32
Q

What renders gamma rays not useful for accurate measurement of radionuclide location?

A

when gamma rays scatter in the body first and change direction

33
Q

What does the collimator design affect?

A

spatial resolution
sensitivity
size of FOV
magnification/minification

34
Q

What does spatial resolution depend on?

A

diameter of holes in the collimator
length of holes
septal thickness
distance of pt from collimator surface
intrinsic resolution of detector

35
Q

What is the point spread function (PSF)?

A

a profile of measured counts as a function of position across a point source

36
Q

What is the modulation transfer function?

A

MTF is one way to more completely characterise the ability of a system to reproduce spatial frequencies

37
Q

How is the MTF calculated?

A

It is calculated as the fourier transform of the PSF or LSF and is a plot of the response of a system to different spatial frequencies

38
Q

What is the relationship between resolution and sensitivity?

A

If resolution is increased by a factor of 2, the sensitivity is decreased by a factor of 4

39
Q

What is the unit of radioactive decay?

A

Becquerel (in NM, we use Mega Becquerel [MBq])

40
Q

what has replaced lung perfusion with technetium

A

CT Pulmonary Angiogram

41
Q

How is Tc predominantly excreted?

A

Urination

42
Q

What is encouraged to lower body dose post NM imaging?

A

Frequent urination/bladder emptying

43
Q

What effect does the collimator have on the gamma camera?

A

it reduces sensitivity to improve spatial resolution and ensure image accuracy.

44
Q

What is the typical administered activity for an isotope bone scan?

A

400-750 MBq

45
Q

What is often used for Lung Perfusion Scans?

A

technetium-99m macroaggregated albumin (Tc-99m MAA)

46
Q

What is the weakest link of Nuc Med, and what should be done because of it?

A

The collimator is the weakest link. Keep the patient close to the collimator

47
Q

What is intrinsic resolution determined by?

A

Multiple compton scattering in detector crystal ( minor limitation )
Statistical fluctuations in the distribution of light photons between PM tubes ( major limitation )

48
Q

The collimator improves..

A

The spatial resolution of the gamma camera

49
Q

Clinical uses of Nuclear Medicine

A

Helps in early diagnosis
Determines severity of disease
Determines response to therapy

50
Q
A

RA6007 Advanced Medical Radiation Science (6 decks)

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