If this were true, we should be seeing a detectable, statistically significant higher rate of cancer in Japan, which has by far the highest rate of CT machines per person. (almost 3× that of the USA, which is still high even among high-income countries)
Considering the health and life expectancy in Japan, I call BS.
Is the load factor of those Japanese machines similar to those used in the US? Isn't life expectancy multifactorial?
The load factor would need to be lower than one third of the US to balance it out, which I'd claim is quite unlikely.
And yeah of course it's multifactorial. It'd make more sense to look at cancer data specifically, but I don't have that at hand. However, cancer is a leading factor in lifespan limits…