> For context, the 0.1 rem yearly dose to the patient is about 1/6th of the average background dose we all get every year.
Wouldn't you be more concerned about dose rates in tissues near the device though, rather than whole body dose? At the surface of the pacemaker it would be about 90 rem / year.
Obviously. That doesn't address my question though, the dose of concern is surely the nearby tissue rather than one calculated over the whole body. If the pacemaker is resting against my lungs, I'm not going to be concerned about foot cancer.
I'm not implying the risk was miscalculated in the medical approval process, I'm sure it's safe enough. I'm just questioning OP's statement about radiation dose, yes it's strictly true but seems to underplay the importance of the nature of the dose.
Thanks. Presumably we're talking about "Dose rates at the surface of the pacemaker are approximately 5 to 15 mrem per hour from the emitted gamma rays and neutrons" though.
> Dose rates at the surface of the pacemaker are approximately 5 to 15 mrem per hour from the emitted gamma rays and neutrons.
Where are these gamma rays and neutrons coming from? The decay chain for Pu-238 is via alpha emission (Pu-238 -> U-234 -> Th-230 -> ...) which won't penetrate the casing.
Alpha particles will produce secondary radiation occasionally when they hit light nuclei. The oxygen in the Pu oxide is almost entirely O-16 to minimize neutron production.
For similar / further reading on historical pacemakers, check out https://www.implantable-device.com/category/implantable-comp... where David Prutchi has amassed what I think is a comprehensive history of pacemakers / neurostimulators ranging from these early atomic designs up through current day devices / companies.
This Pu-238 is the same stuff that's powering the Voyager probes and a few Mars rovers.
Note that it's not Pu-239, which is fissile nuclear fuel for chain reactions (power plants, bombs, etc.)