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 γ-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 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.)

Production routeHo-165(p,n)Er-165
DaughterDecays to stable Ho-165: 100% EC
Half-life10.36 h
ProcessingMulti-step ion exchange
Primary Container2.5 mL borosilicate glass V-vial with silicon rubber screw cap
Product Graden.c.a.
Physical FormLiquid
Chemical FormEr3+ ion in 0.1 M HCl solution (1-2 ml)
Radioactive Concentration (gamma spectrometry)Up to 1 GBq/ml
AppearanceClear colourless solution
Radionuclide identification (gamma spectrometry)Metal impurities determined by ICP-OES for each batch
Radionuclidic Purity (gamma spectrometry)t.b.d.
Chemical purity (ICP-OES)t.b.d.
Molar activity (ICP-OES)t.b.d.
Apparent Molar Activityt.b.d.
Microbiological qualityBioburden and endotoxin burden can be analysed post release, upon request
Bacterial endotoxinBioburden and endotoxin burden can be analysed post release, upon request
pH (pH strips)t.b.d.
Additional information
Activity available1 GBq (more to be discussed) upon request
Activity limit for UN2910 (excepted package) shipment20 MBq in dry state or 2 MBq in liquid form
Other information


  • Auger

Point of supply

  • Risø, Denmark

Involved production facilities

DTU, Denmark