Palladium 103 is a newer sealed source that is used in place of 125I, particularly for permanent interstitial prostate implants. It is coated onto graphite pellets and encapsulated within a titanium shell as seeds.
Physical Properties
103Pd is a pure gamma emitter, decaying through electron capture to 103Rh. Gamma energies range from 20 - 23 keV, with a mean energy of 21 keV. This is slightly lower than 125I, and 103Pd has a smaller HVL in lead and water (lead HVL 0.013 mm). The specific activity of 103Pd is $2.8 \times 10^3$ TeV/g.
Handling Issues
Like 125I, 103Pd has a relatively fragile capsule which may be damaged. As a permanent implant, it dose not requrie disposal, and its shorter half life means that precautions after death and cremation are less of an issue. It should be stored within a lead safe at least 3 mm thick. The low dose rate and low photon energies mean that handling is simpler than the older 226Ra and 198Au implants.
Supply and Disposal
103Pd is supplied by the manufacture and is sterilised prior to insertion. As a permanent implant, disposal issues are less of a concern but precautions following death of the patient should be observed for several months following insertion.
Summary
Advantages:
- Relatively safe for staff to handle during insertion due to low dose rate
- Patients discharged from hospital immediately after procedure
Disadvantages
- Single use only
- Fragile source capsule
