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PHA223 > Radiopharmacy (Cheng) > Flashcards

Radiopharmacy (Cheng) Flashcards

1
Q

What are radiopharmaceutcials?

A

a dosage form consisting of radioactive compounds used for wither the diagnosis or therapeutic treatment of human diseases

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2
Q

What gives an unstable nucleus?

A

change in the number of neutrons (N)

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3
Q

What does Z stand for?

A

atomic number

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4
Q

Z > 83

A

radioactive

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5
Q

What happens when radionuclides decay?

A

they emit particles/energy in the form of stable nuclide

- alpha, beta, positron, neutrons, gamma

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6
Q

Where is alpha decay seen?

A

heavy metals (uranium)

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7
Q

What is alpha emission? (alpha, 4He nucleus)

A

2+ charge of high energy and limitied penetration range

-> nucleus has too many protons

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8
Q

What is beta decay? (beta-)

A

various energy
random motion
negative charge
-> nucleus is neutron rich

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9
Q

What are gamma rays/gamma decay? (y)

A

when nucleus energy is too high
no mass loss
photon energy
high penetration range
isomeric transition - exicted nucleus emits gamma rays
-> if isomeric state is long lasting then it’s meta stable (m)

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10
Q

What is positron decay? (beta+)

A 
positive charge (loss is a proton)
various energy
random motion
proton rich
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11
Q

What is neutron emission? (n)

A

during fusion of heavy metals
no charge loss
loss of mass

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12
Q

What is the disintegrating rate?

A

average number of nuclei that disintegrate during a period of time

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13
Q

What is physical half life?

A

time required to reduce the initial disintegrating rate or activity to one half (outside the body)
tp

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14
Q

What is biological half life?

A

time needed for half of the radiopharmaceutical or radionuclide to disappear from the biological system (inside body)
tb

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15
Q

effective half life (te) formula

A

1/te = 1/tb + 1/tp

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16
Q

dps

A

disintegrations per second

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17
Q

units for radioactivity

A

curies (Ci)

Bacquerel (Bq) - SI unit

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18
Q

How to convert Curies to Bacquerel

A

1 Bq = 2.7 x 10^-11 Ci

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19
Q

How to produce radionuclides?

A 
nuclear reactor (neutrons)
OR
cyclotron (charged particles)
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20
Q

What does a nuclear reactor do?

A

produces neutron rich radionuclides

-> fission/reaction of 235U or 239Pu

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21
Q

What does a cyclotron do?

A

produces proton rich radionuclides

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22
Q

properties of reactor/cyclotron

A

expensive

produce radionuclides have long half life

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23
Q

What is used for radiopharmacy in hospitals?

A

generator system

  • portable and reusable system
  • lead shiels
  • radionuclides have short half life
  • cheaper
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24
Q

What is the most widely used imaging radionuclide?

A

99Mo to produce 99mTc

-> molybdenum and technetium

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25
Q

How is 99Mo produced?

A

from 235U fission

uranium

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26
Q

solid and solvent phase in 99Mo 99mTc generator

A

solid - alumina column

solvent - 0.9% saline

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27
Q

properties of 99Mo 99mTc generator

A

sterile and pyrogen free

physiological pH and isotonic

28
Q

What element is Tc?

A

technetium

29
Q

dosage forms of radiopharmaceuticals

A 
solution
suspension
capsule
gas
-> in a lead container
30
Q

forms of radiopharmaceuticals

A

ions
molecules
complexes

31
Q

What is idrect labeling?

A
  • tagging radioisotope with biological molecules

- non-specific binding to antibodies, RBC etc

32
Q

How to label 99mTc with chelate?

A
  • the oxidation state of Tc needs to be lower (1+ - 5+)
  • use reducing agents like stannous chloride (SnCl2) in acid
  • > lowers Tc oxidation state
  • use a chelating agent
  • > donates a lp of e- to Tc to form a stable complex by formation of a covalent bond
33
Q

How to lower the oxidation state of 99mTc?

A

use a reducing agent in acid

-> SnCl2 (stannous chloride)

34
Q

How to stabilise the bonds in 99mTc?

A

using a chelating agent

  • it donates a lp of electrons to Tc
  • coordinates a covalent bond to stabilise 99mTc
35
Q

2 structures of 99mTc labelled complexes

A

Tc-HMPAO

Tc-sestamibi

36
Q

What do commercial 99mTc labelling kits contain?

A

NO RADIOISOTOPE

  • reducing agent (SnCl2)
  • chelating agent
  • antimicrobial
  • antioxidant
  • buffers (acid/base)
  • solution or lyophilised powder
  • vials for reconstitution/reaction
37
Q

What does the antimicrobial do in a labelling kit and an example?

A

benzyl alcohol

maintains sterility of the kit

38
Q

What do antioxidants do and example of one in labelling kit?

A

sodium bisulfite

avoid re-oxidation of reduced Tc if Sn delpetes

39
Q

What do buffers do in labelling kit?

A

maintain pH of the kit

40
Q

2 types of quality control tests for radiopharmaceuticals

A
  1. physiochemical tests

2. biological tests

41
Q

What do physiochemical tests do in quality control of radiopharmaceuticals?

A
  • radioactivity and specific radioactivity
  • radionuclidic species and radionuclidic purity
  • chemical purity for radiopharmaceuticals and radiochemical purity
  • particle size
  • pH
42
Q

What do biological tests do in quality control?

A

sterility and pyrogen tests

43
Q

What is radionuclidic purity?

A

fraction of total radioactivity in form of the desired radionuclide present in a radiopharmaceutical

44
Q

Where can impurities come from?

A

extraneous nuclear reaction

isotope impurities in target materials

45
Q

impurity in 99mTc

A

99Mo

46
Q

What detects impurities in radionuclidic?

A

gamma spectrometry

47
Q

What is radiochemical purity?

A

fraction of total radioactivity in desired chemical form in a radiopharmaceutical

48
Q

What can cause radiochemical impurity?

A

decomopsition action of solvent, heat, light and radiolysis

49
Q

What detects radiochemical impurities?

A

chromatographic techniques

50
Q

examples of radiochemical impurities

A

free 99mTcO4-
OR
hydrolysed 99mTcO2 in 99mTc labelled albumin

51
Q

What does specific activity mean?

A

total amount of radioactivity per unit mass of a radionuclide or labelled compounds

52
Q

What does specific activity account for?

A

radioactive concentrations and chemical substance concentrations

53
Q

What does specific activity change with?

A

date and time

54
Q

What is radiolysis?

A

decomposition of radiopharmaceutical by radiation

-> 2 types - auto-radiolysis and indirect radiolysis

55
Q

What is auto-radiolysis?

A

absorption of radiation leads to free radical formation

56
Q

What is indirect radiolysis?

A

production of peroxide or radical from decomposition of water

57
Q

What does stability of radiolaballed product depend on?

A

specific activity
energy of emitted radiation
half life

58
Q

Why can positrons be given at a higher dose and higher radiation dosing?

A

they have a very short half life

59
Q

How to image the thyroid gland?

A
  • radioactive iodine given as sodium iodide 131I or 123I capsule given orally
  • uptake is monitored, gamma detector used
  • absorbed into thyroid gland
  • 10-35% after 24hrs
  • hot spot = hyperthyroidism
  • cold spot = carcinoma
60
Q

What is used for thyroid imaging?

A

sodium iodine-123 or I-131

61
Q

alternative for sodium iodine for thyroid imaging

A

99mTc pertechnetate preparation

62
Q

What radiopharmaceutcials are used as therapeutic agents?

A
  • particle emitters - alpha and beta ionisation energy
  • direct/indirect free radical induction
  • permanent damage to DNA
  • induces cellular apoptosis
63
Q

How do alpha/beta particles cause permanent damage to DNA?

A

via strand clevage and base pair mutations

64
Q

How to treat bone matastasis with radiopharmaceuticals?

A
  • 32 P-sodium orthophosphate IV (radioactive sodium phosphate injection)
  • deposits in the bone
65
Q

What radiopharmaceutical is used to treat hyperthyroidism?

A

NaI (131 I) - sodium iodine 131

emits beta- and gamma rays/particles

larger gland = larger dose

PHA223 (43 decks)

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