Properties and Application of Ac-225

Properties and Application of ²²⁵Ac

 

•  Application: Targeted alpha therapy (TAT) nuclear medicine for the treatment of cancers (Prostate, Brain and Neuroendocrine).

• Injected as: ²²⁵Ac-HEHA, ²²⁵Ac-BF-HEHA complex, ²²⁵Ac-DOTA complex

• HEHA: 1,4,7,10,13,16-hexaazacyclohexadecane-N,N′,N″,N‴,N′‴,N″‴-hexaacetic acid  

• BF-HEHA: bifunctional HEHA

• DOTA: 1,4,7,10-tetraazacyclododecane-N,N′,N″,N‴-tetraacetic acid.

• Major decay mode: Alpha particle

• Decay energy: 5.8 MeV (18.9%) α particle + 3 more = 28 MeV alpha

• Half-life(t_1/2): 10 d 

 

• Mode of Production

• Radioactive decay:

²³³U (1.6x10⁵ a)(α) ²²⁹Th (7932a)(α)²²⁵Ra (14.82d) (β-)²²⁵Ac

• Cyclotron/ Accelerator: 

²²⁶Ra(p,2n)²²⁵Ac 

 ²³²Th(p, x)²²⁵Ac (Spallation reaction)

²²⁶Ra(γ,n)²²⁵Ra(β-) ²²⁵Ac (Photonuclear reactions)

• Reactor:  

²²⁶Ra(n, 2n)²²⁵Ra

 

• Chemistry

• Separation in radionuclidic generator ²²⁹Th/²²⁵Ac: Selective adsorption of ²²⁹Th parent and elution of ²²⁵Ac daughter

• Separation of Ac from Th and Ra: Anion and cation exchange chromatography.

•  Assay

Alpha Spectrometry

• Challenges

• Absence of stable targets and non availability of targets in bulk quantity

• No stable isotopes of this element.

• Chemistry of Ac, not well studied

• Presence of Radioactive daughters in the decay products
  

• Approval status: In progress

• Manufacturer

ORNL, TN, USA

ITU, Karlsruhe, Germany

IPPE, Obninsk, Russia

• Reference

[1] A Scheinberg, David, and Michael R McDevitt. "Actinium-225 in targeted alpha-particle therapeutic applications." Current radiopharmaceuticals 4.4 (2011): 306-320.

[2] Robertson, Andrew KH, et al. "Development of 225Ac radiopharmaceuticals: TRIUMF perspectives and experiences." Current radiopharmaceuticals 11.3 (2018): 156-17

 

 

Further Reading Suggestion

Radioisotopes used in Medicine and Industry