Chemical properties

Er-165 is a radiolanthanide, usually in trivalent state. The ionic radius of Er3+ is 89 pm, i.e. just 3% larger than Lu3+, which explains that chelators suitable for Lu-177 can be directly employed for Er-165 too, in particular DOTA.

Nuclear properties

Er-165 decays by electron capture decay with a half-life of 10.36 hours to stable Ho-165.

Er-165 emits no gamma-rays, but X-rays, notably Kα at ≈47 keV (59.4(9) %) and Kβ at ≈54 keV (14.3(19) %). These energies make Er-165 suitable for SPECT-imaging.

The mean photon energy per decay is 37 keV and the mean electron energy emitted per decay is 5 keV . Most electrons are short-range Auger electrons with <1 µm and <26 µm respectively. Er-165 has therefore been proposed as therapeutic Auger electron emitter .


Er-165 is produced by proton irradiation of natural Ho carbonate targets at Hevesy Laboratory at DTU. A Ho/Er separation is performed by ion exchange chromatography.


Activity will be shipped from the PRISMAP facility Hevesy Laboratory (DTU, Risø, Denmark) to the users in form of Er3+ solution.

Examples of use

  • Preclinical imaging with Er-165 has been reported .
  • Er-165-EDTMP as bone seeker has been tested preclinically .
  • A Gd3+/Er-165 cocktail was used to assess the Zn2+ dependent MRI response .

Purity grades available


No carrier added (n.c.a.)

Half-life10.36 h
DaughterStable Ho-165
Branching Ratio/Decay100% EC
Purificationmulti-step ion exchange
Chemical FormEr3+ ion in 0.1 M HCl solution (1-2 ml)
Specific Activityt.b.d.
Radionuclidic Purityt.b.d.
Radiochemical Purityt.b.d.
Chemical PurityMetal impurities determined by ICP-OES for each batch.
IdentificationX-ray spectroscopy and half-life
AppearanceClear colourless solution
Activity available1 GBq (more to be discussed)
AvailabilityUpon request
GradeResearch grade, n.c.a.
Other informationBioburden and endotoxin burden can be analysed post release, upon request.


  • Auger

Point of supply

  • Risø, Denmark

Involved production facilities

DTU, Denmark