Re 188 Generators in Nuclear medicine

1. Dr.Vishnukumar R, MD Nuclear Medicine
Jawaharlal Institute of Post graduate Medical
Education and Research (JIPMER),
Puducherry, India.

2. Learning objectives
• Production of W-188
• Types of Re-188 generator.
• Properties of W-188/Re-188 column
generator.
• Basic radiochemistry.
• Brief applications.

3. • Naturally occurring Rhenium isotopes are Re-
185 and Re-187.
• About 45 isotopes have been reported for
Rhenium.
• Discovered in Srilanka and named after Rhine
river in Europe.
• Most commonly studied are Re-186 and Re-
188

5. Rhenium-188

7. • Enriched = Purity
• Nuclear cross section- Probability that the
desired nuclear reaction will takes place.
• Neutron flux- density of flow.

8. Problems in production of W-188
• Natural abundance of W-186 is 26.8%.
Requires enrichment.
• W-188 is produced from W-186 by double
neutron capture process.
• Cross section for double neutron capture is
less.
• Only way to increase cross section is to
increase the flux.

10. • Tungsten is converted into sodium tungstate
before transferring into generator.
• Low density target- chance of burn up is
more.
• Require pressed targets.
• Once tungsten is formed it is heated in
furnace, in order to facilitate the ease of
solubility into NaOH.

11. Availability of high flux reactors
• ORNL & ATR- USA
• BR2- Belgium
• SM3- Russia
• ITM- Munich, Germany.
• Specific activities ranges between 1-5Ci/g.

12. Re 188 generators
• Types of generators:
– Gel generator.
– Alumina column generator.
– Solvent extraction generator.
• Gel generator:
– Sodium tungstate was made to react with zirconium
nitrate in acidic medium and precipitated as zirconium
tungstate.
– This is dried and packed in powder form.
– Eluted using normal saline. Obtained in the form of sodium
perrhenate.
– Not commercialised due to less yield.

13. • Column generators:
– Acidic Alumina matrix used.
– Eluted using normal saline.
– Due to less specific activity, yield of Re-188 is 75-80%
of W-188.
– W-188 exhibits limited binding with alumina, requiring
large column.
– This mandates elution with large volume of normal
saline resulting in low activity concentrations.
– Minimum concentration required for labelling is
20mCi/ml.
– Concentration circuits are required

14. • Concentration circuits:
– Silver/QMA anion exchange pumps.
– Chloride anion binds to silver and perrhenate
binds to QMA.
– This has to be washed with water followed by
elution with NS.
– Volume of NS depends on void volume of QMA
column.
– Automated and semi-automated circuits available.
– Final concentration- 1Ci/3ml.

19. Radiochemistry
• Exhibits 7+ oxidation state.
• Energy required for reducing perrhenate is more.
• Expansion of coordination sphere.
• Perrhenate will be made to react with oxalate
ions.
• This oxalate ions will substitute the oxo groups.
• This intermediate product will be made to react
with desired radiopharmaceuticals in the
presence of SnCl2.

20. Applications
S.NO PROCEDURE AGENTS
1 Bone pain palliation Re 188-HEDP
2 Radiation synovectomy Re 188 colloids and
microspheres
3 Non melanoma skin tumours Re 188 skin patch
4 Primary liver malignancy and liver metastases Re 188 labelled Lipodol,
microspheres
5 Intravascular radionuclide therapy Re 188 MAG3, DTPA and
perrhenate
6 Marrow ablation Re 188 labelled MAb
7 Treatment of medullary carcinoma of thyroid Re 188 DMSA (V)

21. Summary
• W188 decays to Re188.
• Half life of W188 is 69.2 days and Re188 is
16.9 hours.
• Beta max- 2.12 Mev.
• Gamma energy- 155 Kev (15%).
• Yield is 75-80%.

22. • Eluted with NS.
• Automated and semi automated generators
available.
• Unlimited shelf life. Limited only by activity
concentrations.
• Imaged with HE collimators.
• 7+ oxidation state.
• An intermediate compound is formed which is
made to react with desired radiopharmaceuticals.

23. References
• 1. Argyrou M, Valassi A, Andreou M, Lyra M. Rhenium-
188 Production in Hospitals, by W-188/Re-188 Generator,
for Easy Use in Radionuclide Therapy. Int J Mol Imaging.
2013;2013:1–7.
• 2. Boschi A, Uccelli L, Pasquali M, Duatti A, Taibi A, Pupillo
G, et al. 188 W/ 188 Re Generator System and Its Therapeutic
Applications. J Chem. 2014;2014:1–14.
• 3. R.A. Pillai M, Dash A, F. Knapp F. Rhenium-188:
Availability from the 188W/188Re Generator and Status of
Current Applications. Curr Radiopharm. 2012 Jun
1;5(3):228–43.
• 4. Therapeutic nuclear medicine. New York: Springer;
2014.