Radiopharmaceuticals

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Radiopharmaceuticals
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Objective

• understand the procedure involved in the
  preparation of radiopharmaceutical
• Appreciate the biological and radiological
  properties

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General stages in the preparation

• Preparation of primary radionuclide
• Conversion of radionuclide into the chemical form

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Preparation of primary radionulcide

• Nuclear reactor
• Nuclei are bombarded with neutrons in a nuclear
  reactor
• (n,3n) , (n,p) and (n,?)
• Cyclotron
• Nuclei are bombarded with charge particle
  accelerated in a cyclotron
• (d,n),(a,2n),(a,np) etc

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Comparision

• Majority of isotopes are prepared by reactor
  method
• Cost is less
• Can deal with large quantity of material

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Conversion into chemical form

• Egs
• Technetium (99 TC m)
• Used in nuclear medicine scan of
• brain
• lungs
• liver
• bone
• heart

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The 99Mo-99Tc m generator

• The parent Molybdenum is obtained from the
  nuclear reactor
• (n,?) or by fission of uranium
• Molybdenum is prepared as ammonium molybdenate.
• Heat in air Mo ----MoO3-
• This reacts with NH4 to form NH4MoO3
• Absorbed on alumina in a glass or plastic column

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• 99 Mo undergoes ß-decay, to form Technitium
• the chemical state will be NH4TcO4
• This is treated with a strong solution of sodium
  chloride during which TcO4- ions are exchanged
  for Cl- .
• This is done by ellution
• The solution is then collected and used for
  treament
• The concentration of the solution is determined
  according to the patient.
• The generator has to be replaced after about a
  week.

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Reasons for use of 99 Tc m

• Only emits ? rays
• The ? rays have an energy of 140 keV.
• Half life is very short ( 6 hours)
• Can be incorporated into wide variety of
  radiopharmaceuticals
• Relatively cheap

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To think about

• What are the factors affecting the choice of
  radionuclide used for diagnosis
• Radiological factor(s)
• Biological factor(s)