4 ms·

> The danger of an unnecessary CT/PET is causing cancer You'd have to be massively overexposed to CT or PET scanning to cause cancer, like in the region of spe

> The danger of an unnecessary CT/PET is causing cancer You'd have to be massively overexposed to CT or PET scanning to cause cancer, like in the region of spending months being scanned continuously with it at full beam current.

rustyhancock 9mo ago
Even if you don't agree with linear no threshold models for cancers induced by radiation (I don't think LNT is accurate). It comes down to the scan and the age. 3 scans for a 1 year old? Strongly associated with cancers later in life. 5 scans of a 50 year old? Less so. The 1 year old has an 80 year run way to develop cancer, along with cells already set in a state of rapid division, and a less developed immune system. But the association is quite strong. https://www.sciencedirect.com/science/article/pii/S0720048X25005571 https://www.sciencedirect.com/science/article/pii/S0720048X2...
- pfdietz 9mo ago
  > I don't think LNT is accurate There's excellent reason to think LNT is accurate: at low doses, almost every cell is exposed to at most one radiation event. The dose affects how many cells experience a (single) event, but does not affect the level of damage to those exposed cells. Linearity naturally falls out of this. To abandon linearity you have to imagine some sort of signalling system (not observed) that kicks in at just the dose we're talking about (not lower, not higher) to allow exposure to one cell to affect other cells. There's also no good evidence that LNT is wrong. The typical things that are pointed to by anti-LNT cranks are cherrypicked, often involving interim results from studies the full results from which do support LNT, which is evidence it was statistical noise.
- ErroneousBosh 9mo ago
  > 3 scans for a 1 year old? Strongly associated with cancers later in life. 5 scans of a 50 year old? Less so. Someone being born with no legs is strongly associated with them using a wheelchair in later life. Why are you giving a one-year-old three CT scans? For shits and giggles? Or because you think they might have cancer?
- pedalpete 9mo ago
  I think the bigger point you are making is that the 50 year old is also more likely to have developed cancer. Maybe a full body MRI once a decade is fine until your 30s, then once every 5 years until 50, then once ever 2 years beyond 50. The test should scale with the probability of cancer.
  - deleted 9mo ago
    [deleted]
  - bondarchuk 9mo ago
    They were not talking about MRI, there is a significant difference.
  - bondarchuk 9mo ago
    They were not talking about MRI, there is a significant difference (purported).
lostlogin 9mo ago
> You'd have to be massively overexposed to CT or PET scanning to cause cancer The mean effective dose for all patients from a single PET/CT scan was 20.6 mSv. For males aged 40 y, a single PET/CT scan is associated with a LAR of cancer incidence of 0.169%. This risk increased to 0.85% if an annual surveillance protocol for 5 y was performed. For female patients aged 40 y, the LAR of cancer mortality increased from 0.126 to 0.63% if an annual surveillance protocol for 5 y was performed. https://pubmed.ncbi.nlm.nih.gov/36856709/ https://pubmed.ncbi.nlm.nih.gov/36856709/
- ErroneousBosh 9mo ago
  > 0.126 to 0.63% So, a just-about-measurable increase, if you pick and choose your values carefully? You are not going to die from cancer caused by getting a PET scan. This will not happen. You're going to die of heart disease or as a not-too-distant second in a car accident.
  - lostlogin 9mo ago
    That data is for one scan, ever. Continuous scanning for months would give a dose many orders of magnitude higher.
azan_ 9mo ago
Approx. 5% of all cancers in US are caused by CTs
- ErroneousBosh 9mo ago
  [citation needed]
  - lostlogin 9mo ago
    5% seems a bit high, but we are nearly there. https://www.facs.org/for-medical-professionals/news-publications/news-and-articles/acs-brief/may-13-2025-issue/ct-imaging-increases-lifetime-cancer-risks/ https://www.facs.org/for-medical-professionals/news-publicat...
    - ErroneousBosh 9mo ago
      I think they're reading too much into it. How are they determining "this cancer was caused by the CT scan" versus "this cancer was caused by the cancer we were originally looking for that was there all along"?
      - lostlogin 9mo ago
        Radiation doesn’t label the cancers it causes. Other than comparing population groups, what method do we have?
        ErroneousBosh 9mo ago
        Well, you could work backwards and look at your assumptions. Why is "We think this person has cancer so we gave them a CT scan and look! Now they've got cancer! It must be because of the CT scan!" the conclusion to jump to?
        azan_ 9mo ago
        Please just read this article - https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2832778 https://jamanetwork.com/journals/jamainternalmedicine/fullar... It's funny that you instantly assumed that authors are stupid and did not think about this obvious pitfall. It's extra funny that you also accuse them of jumping to conclusion without actually reading the article.

rustyhancock 9mo ago

Even if you don't agree with linear no threshold models for cancers induced by radiation (I don't think LNT is accurate). It comes down to the scan and the age. 3 scans for a 1 year old? Strongly associated with cancers later in life. 5 scans of a 50 year old? Less so. The 1 year old has an 80 year run way to develop cancer, along with cells already set in a state of rapid division, and a less developed immune system. But the association is quite strong. https://www.sciencedirect.com/science/article/pii/S0720048X25005571 https://www.sciencedirect.com/science/article/pii/S0720048X2...

pfdietz 9mo ago
> I don't think LNT is accurate There's excellent reason to think LNT is accurate: at low doses, almost every cell is exposed to at most one radiation event. The dose affects how many cells experience a (single) event, but does not affect the level of damage to those exposed cells. Linearity naturally falls out of this. To abandon linearity you have to imagine some sort of signalling system (not observed) that kicks in at just the dose we're talking about (not lower, not higher) to allow exposure to one cell to affect other cells. There's also no good evidence that LNT is wrong. The typical things that are pointed to by anti-LNT cranks are cherrypicked, often involving interim results from studies the full results from which do support LNT, which is evidence it was statistical noise.
ErroneousBosh 9mo ago
> 3 scans for a 1 year old? Strongly associated with cancers later in life. 5 scans of a 50 year old? Less so. Someone being born with no legs is strongly associated with them using a wheelchair in later life. Why are you giving a one-year-old three CT scans? For shits and giggles? Or because you think they might have cancer?
pedalpete 9mo ago
I think the bigger point you are making is that the 50 year old is also more likely to have developed cancer. Maybe a full body MRI once a decade is fine until your 30s, then once every 5 years until 50, then once ever 2 years beyond 50. The test should scale with the probability of cancer.
- deleted 9mo ago
  [deleted]
- bondarchuk 9mo ago
  They were not talking about MRI, there is a significant difference.
- bondarchuk 9mo ago
  They were not talking about MRI, there is a significant difference (purported).

lostlogin 9mo ago

> You'd have to be massively overexposed to CT or PET scanning to cause cancer The mean effective dose for all patients from a single PET/CT scan was 20.6 mSv. For males aged 40 y, a single PET/CT scan is associated with a LAR of cancer incidence of 0.169%. This risk increased to 0.85% if an annual surveillance protocol for 5 y was performed. For female patients aged 40 y, the LAR of cancer mortality increased from 0.126 to 0.63% if an annual surveillance protocol for 5 y was performed. https://pubmed.ncbi.nlm.nih.gov/36856709/ https://pubmed.ncbi.nlm.nih.gov/36856709/

ErroneousBosh 9mo ago
> 0.126 to 0.63% So, a just-about-measurable increase, if you pick and choose your values carefully? You are not going to die from cancer caused by getting a PET scan. This will not happen. You're going to die of heart disease or as a not-too-distant second in a car accident.
- lostlogin 9mo ago
  That data is for one scan, ever. Continuous scanning for months would give a dose many orders of magnitude higher.

azan_ 9mo ago

Approx. 5% of all cancers in US are caused by CTs

ErroneousBosh 9mo ago
[citation needed]
- lostlogin 9mo ago
  5% seems a bit high, but we are nearly there. https://www.facs.org/for-medical-professionals/news-publications/news-and-articles/acs-brief/may-13-2025-issue/ct-imaging-increases-lifetime-cancer-risks/ https://www.facs.org/for-medical-professionals/news-publicat...
  - ErroneousBosh 9mo ago
    I think they're reading too much into it. How are they determining "this cancer was caused by the CT scan" versus "this cancer was caused by the cancer we were originally looking for that was there all along"?
    - lostlogin 9mo ago
      Radiation doesn’t label the cancers it causes. Other than comparing population groups, what method do we have?
      - ErroneousBosh 9mo ago
        Well, you could work backwards and look at your assumptions. Why is "We think this person has cancer so we gave them a CT scan and look! Now they've got cancer! It must be because of the CT scan!" the conclusion to jump to?
        azan_ 9mo ago
        Please just read this article - https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2832778 https://jamanetwork.com/journals/jamainternalmedicine/fullar... It's funny that you instantly assumed that authors are stupid and did not think about this obvious pitfall. It's extra funny that you also accuse them of jumping to conclusion without actually reading the article.