Chemical properties
Er-165 is an emerging medical radio-lanthanide that, as a pure Auger electron emitter, is well suited for targeted ultra-short-range cancer therapy. In aqueous solution, Er-165 is typically present in the trivalent oxidation state. The ionic radius of Er³⁺ is 89 pm, which is slightly larger than that of Lu³⁺, therefore established chelators used for ¹⁷⁷Lu can also be employed for Er-165, particularly 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 REF. 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 REF.
Production
Er-165 is produced by proton irradiation of natural Ho oxide targets at Hevesy Laboratory at DTU. A Ho/Er separation is performed by multi-step extraction chromatography.
Distribution
Activity will be shipped from the Hevesy Laboratory (DTU, Risø, Denmark) to the users in form of Er3+ solution.
Examples of use
| Parameter | Specifications |
|---|---|
| Production route | Ho-165(p,n)Er-165 |
| Daughter | Decays to stable Ho-165: 100% EC |
| Half-life | 10.4 h |
| Processing | Multi-step extraction chromatography |
| Primary Container | 2.5 mL borosilicate glass V-vial with silicon rubber screw cap |
| Product Grade | n.c.a. |
| Physical Form | Liquid |
| Chemical Form | Er3+ ion in 0.1 M HCl solution (1-2 ml) |
| Radioactive Concentration (gamma spectrometry) | Up to 1 GBq/ml |
| Appearance | Clear colourless solution |
| Radionuclide identification (gamma spectrometry) | No γ (X-rays around 47 and 54 keV present) |
| Radionuclidic Purity (gamma spectrometry) | >99 % |
| Chemical purity (ICP-OES) | Metal impurities determined by ICP-OES for each batch. Typical 20 nmol Ho, 2 nmol Er, 3 nmol Fe, 17 nmol Al, and 20 nmol Ca per batch. |
| Molar activity (ICP-OES) | t.b.d. |
| Apparent Molar Activity | t.b.d. |
| Microbiological quality | Bioburden and endotoxin burden can be analysed post release, upon request |
| Bacterial endotoxin | Bioburden and endotoxin burden can be analysed post release, upon request |
| pH (pH strips) | 1 |
| Additional information | |
| Activity available | 1 GBq (more to be discussed) upon request |
| Activity limit for UN2910 (excepted package) shipment | 20 MBq in dry state or 2 MBq in liquid form |
| Other information | - |
