Actually high energy electrons can and do penetrate body tissue quite easily within the body, which is why it is used to destroy cancer cells
Missed this earlier, but it demonstrates the dangers of attempting to extend one's knowledge base outside its realm. All electrons are not created equal. The electron beams used in cancer therapy range up to 25MeV, (and they're still only useful for superficial tumors. ) Whereas the electrons emitted by Ni-63 are only 17 KeV (0.017 MeV). Equating the two is like comparing the risk of being hit by a high-speed concrete truck, vs. a slow-walking turtle.
My nuclear chemistry professor taught me a very relevant rule of thumb when it comes to messing with isotopes, it goes like this, “the human physiology has had time to adapt a means to tolerate the radioactive atoms naturally found on Earth, however there are no such mechanisms present to tolerate synthetic isotopes”.
This is quack witch-doctor pseudo-science, sorry. All radioisotopes emit alpha, beta, gamma, or neutrons, and we have a simple, accurate means to equate the relative fluxes and energy-levels to a standardized dose (the roentgen-equivalent man, or (in SI terms) the Gray.
The notion that "synthetic" isotopes are somehow worse than natural ones because we've "evolved to adapt" to radium, thorium, or U-235 would be laughable, were it not outright dangerous. This quack "professor" needs to be fired, then horse-whipped out of town before he gets someone killed.