Ytterbium-169 (169Yb) was explored as a potential radioisotope for LDR and HDR applications due to it’s low average energy (93keV). The lower energy allows for reduced shielding and opens the potential for small directionally shielded sources or applicators. A 169Yb LDR source, the GAMMAclip, was developed by Source Production & Equipment Co (New Orleans, LA).

Sample of Ytterbium-169

Quick Facts 

  • Half life: 32.03 days
  • Average Energy: 93keV (Excluding <10keV photons)
  • Exposure Rate Constant1
    • \(\Gamma_{\delta} = 1.80\frac{R \\ cm^2}{mCi-h}\)
  • Air Kerma Rate Constant1
    • \(\Gamma_{AKR} = 0.427 \frac{cGy \ cm^2}{h \ MBq}\)
  • Roentgen-to-rad conversion factors (\(f_{med}\))
    • \(f_{soft tissue} = 0.922 \frac{cGy}{R}\)
    • \(f_{bone} = 2.12 \frac{cGy}{R}\)
  • Lead attenuation1
    • First HVL = 0.2mm
    • First TVL = 1.6mm
  • Decay Mode: Electron Capture
Ytterbium-169 decay scheme

Works Cited

  1. 1.
    Mason D, Battista J, Barnett R, Porter A. Ytterbium-169: calculated physical properties of a new radiation source for brachytherapy. Med Phys. 1992;19(3):695-703.