How to calculate SAR for an implanted antenna in a medium

I'm a beginner with FEKO, and I'm trying to figure out how to calculate SAR for an implanted antenna in a human medium. I've placed a dipole antenna inside a cylindrical body like this. From my simulation results, the near-field SAR distribution and the peak spatial-average SAR are different by several orders of magnitude. However, when I take the antenna out and simulate it in free space, both results are roughly the same.

Also，should the antenna surface be covered with a dielectric layer in this kind of simulation？