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.