Hacker News Reader

Comment by snarkconjecture | Hacker News Reader

It would be astonishing if it were a mistake.

And yes, it's a detectable signal. "in a large population-based cohort it was found that up to 4% of brain cancers were caused by CT scan radiation" --somewhere on Wikipedia

CT scans vary in dosage. Wiki gives ~10 Sv for an abdominal CT; I don't know where Scott got 30, but maybe the kidney screening is multiple scans or otherwise higher dose. Or he was wrong by a factor of 3, which is not a factor of 100.

CT scans aren't done frivolously, and the current rate of scans is hotly debated for exactly this reason. I'm a little surprised that kidney donation involves CT over MRI by default, but I'm not an expert.

View on HN

> I don't know where Scott got 30, but maybe the kidney screening is multiple scans or otherwise higher dose.

Scott called it "multiphase abdominal CT". Quick searching on-line suggests[0] that the "multiphase" here stands for doing 3-4 scans within a minute or two of each other, as the contrast agent diffuses through the organ, giving you multiple images that inform you about different parts of the target structure.

> Wiki gives ~10 Sv for an abdominal CT; (...) Or he was wrong by a factor of 3

If what I wrote above is correct, then it tracks - ~10 mSv for one CT, multiplied by 3-4 scans done in a multiphase CT, gives you ~30-40 mSv, which matches the number Scott posted.

[0] - https://www.barnardhealth.us/dynamic-contrast/multiphasic-im... - First link I found; CTRL+F "multiphase", as the relevant information is spread throughout the comments section.

> I don't know where Scott got 30

The text where he says that is a clickable link! https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4635397/

> CT scans aren't done frivolously

As someone who works in the ED, we pretty much give CTs out like candy to avoid a lawsuit if we miss something.

I stand corrected.

Abdominal stuff often involves CT scans that need to be done in phases. For brain stuff, some things require CT vs MRI.

Another risk is the contrast dye that’s often used in these studies. If you’re dealing with cancer monitoring or something that requires monitoring, you can develop allergies and poor reactions to that as well.

Reply on news.ycombinator.com