Radiation Oncology/Unsealed sources

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See also: Isotopes used in Radiation Oncology

For bone metastases[edit]

These have usefulness in treating blastic bone lesions (basically anything that lights up a bone scan). The dose limiting toxicity is bone marrow. Observe platelet counts.


  • Phosphorus 32 - beta emitter
Gets taken up in bone
Not commonly used
  • Strontium 89 (Metastron) - beta emitter
Calcium analog, gets taken up in bone
Long half life (50.5 days physical half-life)
Usual dose 4 mCi (supplied as a 4 mCi vial)
May also be dosed at 0.040-0.060 mCi/kg
  • Samarium 153 (Quadramet) - beta and gamma emitter
Bound to a tetraphosphonate, which gets taken up in area of active
Usual dose 1 mCi/kg (may use 0.5 mCi/kg)
Short half life (about 3 days)
Can repeat dose after about 6-8 weeks
Lowest effective range (compared to Sr and P) and thus lower bone marrow toxicity
Can be used for imaging also due to its photon component


P-32[edit]


  • Pure Beta emitter
    • Energy: 1.71 MeV and 0.69 MeV electrons
    • Average tissue penetration: 1.4-3mm
    • T ½ : 14.3 days
    • Benefit: no photon contamination
  • Typical dose: 10-15 mCi
    • 10 mCi gives equivalent of 30Gy to the peritoneum
  • Distribution
    • Test intraperitoneal distribution with T-99mc prior to treatment
    • Inhomogeneous dose distribution.
    • Mainly absorbed in the peritoneal surface
    • Some enters systemic circulation via lymphatics and is removed by the liver
    • LNs receive low, subtheraputic doses
    • Little hemopoetic toxicity
    • Peripheral blood dose: 1.2 cGy
    • Bone marrow dose: 6 cGy


Research[edit]

  • Experimental antibody based methods - alpha emitters
At the ITU (Institute for Transuranium Research; website) work is being done on Alpha-Immunotherapy, an experimental method using antibodies bound to alpha isotopes. Bismuth-213 is one of the isotopes which has been used. This is made by the alpha decay of Ac-225. The generation of one shortlived isotope from longer lived isotope is a useful method of providing a portable supply of a shortlived isotope. This is similar to the generation of technetium-99m by a technetium cow. The actinium-225 is made by the irradation of radium-226 with a cyclotron.

Guidelines[edit]

Reviews[edit]

Samarium-153:

  • 2004 PMID 16985930 -- Full text "Overview of Samarium Sm 153 Lexidronam in the Treatment of Painful Metastatic Bone Disease" (Sartor O, Rev Urol. 2004;6 Suppl 10:S3-S12.)