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Comment by jozvolskyef | Hacker News Reader

It is a tough call this one. If my calculations are correct, based on data from[1], male infant head CT scans cause one excess death per ~3k scans. There must have been something else than a remote possibility to warrant ordering it.

[1]: https://www.ajronline.org/doi/full/10.2214/AJR.12.10294

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Maybe being an ER doctor itself could bias their decisions more favorable toward CT scans. ER people may see dead people & people with tumors more often than pediatric doctors in their offices. The usual pediatric doctors would see much more patients with ear infections.

Also, to ER people, knowing the root cause is probably important for patients' survival, whereas for pediatric doctors, more often than not, lives are not at stake and customer service/easing parents' fear is more important.

I interpret the linked article different. Can you elaborate?

For example (from the summary):

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"CONCLUSION. Radiation exposure from the use of CT in the evaluation and management of severe traumatic brain injury causes negligible increases in lifetime attributable risk of cancer and cancer-related mortality. Treating physicians should not allow the concern for future risk of radiation-induced cancer to influence decisions regarding radiographic evaluation in the acute treatment of traumatic brain injury."

(edited: formatting)

Excess Cancer Mortality per 100,000 individuals exposed to 100mSv is ~1000 in the 1 year-old male cohort. A single scan is ~3mSv, which makes the mortality ~30 per 100k, or 1 in ~3333, assuming the linear no-threshold model[1].

When someone comes to the ER with a traumatic brain injury, a CT scan is the standard practice because they are at a high risk of dying and presumably the scan is important for reducing the risk.

[1]: https://en.wikipedia.org/wiki/Linear_no-threshold_model

I'm so glad you mentioned the linear no-threshold model.

Do you believe in it? I don't, particularly at the single digit mSv level.

At some point there will be enough data from different countries to confidently support or reject it. Until then I see it as the preferred hypothesis by Occam's razor and also because I'd rather err on the side of caution.

You need to read those things literally. It doesn't mean CT scans should be used whenever a doctor thinks. It means that a doctor evaluating a TBI should be ok with using it. Basically, the odds switch when there is an additional symptom that there is something wrong with the head.

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