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RA6007: Radiation Physics > Nuclear Medicine > Flashcards

Nuclear Medicine Flashcards

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1
Q

what is the main radionuclide used in nuclear medicine

A

Technetium (Tn)

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2
Q

how is technetium produced

A

Tn is produced in a generator from Molybdenum

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3
Q

what process is involved in Tn 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

In Nuclear Medicine, what does the generator consist of

A

the generator is a lead lined container with the parent radionuclide

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6
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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7
Q

the eluate from a technetium generator is called?

A

sodium pertechnetate

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8
Q

what are some advantages of technetium

A

6hr half life
pure gamma emitter
easy to shield
combines well with other chemicals used in bone scans and renal imaging
non-toxic

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9
Q

what is molybdenum breakthrough

A

tiny amounts of molybdenum in solution of sodium pertechnetate

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10
Q

how is Mo breakthrough measured?

A

comparing eluate activity with and without Pb shielding

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11
Q

what is the main imaging device in NM

A

gamma camera

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12
Q

what is the gamma camera combined with

A

a collimator

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13
Q

what is the purpose of the collimator

A

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

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14
Q

what is the gamma camera made of

A

sodium iodide doped with thalium

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15
Q

what effect does crystal thickness have on detector efficiency and spatial resolution

A

thicker the crystal, greater detector efficiency but lower spatial resolution

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16
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

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17
Q

the light emitted is proportional to what?

A

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

18
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

19
Q

where does the Zpulse go

A

to the pulse height analyser

20
Q

what does the pulse height analyser do

A

PHA selects the isotope peak

21
Q

what is the Z pulse proportional to

A

the z pulse is proportional to the total light output from one scintillation

22
Q

what happens if z pulse is accepted

A

the positional circuitry is triggered to locate the gamma ray interaction

23
Q

what is the PHA purpose

A

choice of photo peak
exclude compton scatter

24
Q

what is the energy spectrum

A

the number of measured events with a given energy plotted as a function of energy

25
Q

what is the goal of NM

A

To map the distribution of radiotracers

26
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

27
Q

what does the collimator design effect

A

spatial resolution
sensitivity
size of FOV
magnification/minification

28
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

29
Q

what is the point spread function (PSF)

A

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

30
Q
A
30
Q

line spread function

A

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

31
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

32
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

33
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

34
Q

`what is the unit of radioactive decay?

A

Becquerel (in NM, we use MBq)

35
Q

what has replaced lung perfusion with technetium

A

CT pulmonary angiography

36
Q

what is the annual whole body dose limit for a member of the public

A

1mSv

37
Q

what is the limit for the lens of the eye

A

15mSv

38
Q

what is the whole body dose limit for a category B worker?

A

6mSv

39
Q

How is Tc predominantly excreted?

A

via urine

40
Q

what is encouraged to lower body dose?

A

frequent bladder emptying

41
Q

what is the typical whole body dose in a bone scan

A

5mSv

RA6007: Radiation Physics (2 decks)

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