7 ms·

I read that a CT scan outperforms the lab test at detecting it

by kuprel 7y ago

frisco 7y ago
CT scans involve a lot of ionizing radiation. Definitely something to be avoided unless necessary.
- ridgeguy 7y ago
  According to [1], a chest CT scan rad dose ranges from 4 to 18 milliSieverts. Annual background dose is ~3 milliSv. [2] states that a 100 mSv dose would increase risk of cancer by 0.5% (5/1000). [1] https://www.health.harvard.edu/cancer/radiation-risk-from-medical-imaging https://www.health.harvard.edu/cancer/radiation-risk-from-me... [2] https://www.scientificamerican.com/article/air-travel-exposes-you-to-radiation-how-much-health-risk-comes-with-it/ https://www.scientificamerican.com/article/air-travel-expose...
  - hcknwscommenter 7y ago
    You cannot compare an annual background dose to the dose received in a CT scan. Similarly, the 100 mSv dose of your reference number 2 is an inappropriate comparison because it is spread out over time compared to a CT scan. Your premise is like saying, walking puts an impact of .8 J on my foot. I walk 10,000 steps a day. 10,000*.8 is 8,000 J. A bullet produces an impact of 168 J when fired from a .22 rifle into a human body. Therefore walking is much more dangerous than a bullet from a rifle.
    - ridgeguy 7y ago
      What you suggest seems plausible, but I can't immediately calculate, for example, DNA repair rate vs. X-ray photon flux and cross-sections. Can you point me to something that confirms incidence or severity of radiation-induced disease depends on flux rather than dose? Tnx.
      - Retric 7y ago
        Sun burns are known to significantly increase cancer risks vs similar exposure over longer periods. Sun burns are rather similar to accuse radiation poisoning suggesting similar issues.
      - hcknwscommenter 7y ago
        Both dose and flux matter.
    - carterehsmith 7y ago
      Above, there is a link to a report from Harvard Medical School, that claims otherwise. Maybe they are wrong, but a post on HN is not exactly a credible refutation.
      - hcknwscommenter 7y ago
        And yet, this Harvard Medical School link (not a report, not peer reviewed, but whatevs) clearly states that one CT scan of 4 to 18 mSV increases cancer risk by 0.7%, which is higher than the increase of 0.5% from 100 mSV exposure over a greater period of time. So, no. The Harvard Medical School link does not refute in any way my point. In fact, it supports my point.
    - unsrsly 7y ago
      The Sievert unit is based upon the Gray unit of radiation dose, but it also includes a weighting factor for the type of biological tissue that is exposed to radiation. You can also read up on the linear no-threshold model of radiation exposure for more information. In terms of cancer risk, radiation doses on a range from 1 mSv to 100 mSv can definitely be compared, regardless of the duration of the exposure. There is a range of higher doses e.g. above 1 Gy that would cause acute radiation syndrome if received all at once, where different biological effects would predominate.
  - onlyrealcuzzo 7y ago
    0.5% absolute points or by 0.5%? Chance of cancer is already really low. Multiplying it by 1.005 doesn't make much of a difference. Adding 0.5% does.
- ineedasername 7y ago
  Wouldn't tracking a virus like this be such a necessary situation?
carbocation 7y ago
A CT scan is not an appropriate screening test for COVID-19. Also, that paper will have no clinical impact. Thread: https://twitter.com/drlukeor/status/1233547995192279040?s=21 https://twitter.com/drlukeor/status/1233547995192279040?s=21
- carbocation 7y ago
  Follow-up from the American College of Radiology: https://www.acr.org/Advocacy-and-Economics/ACR-Position-Statements/Recommendations-for-Chest-Radiography-and-CT-for-Suspected-COVID19-Infection https://www.acr.org/Advocacy-and-Economics/ACR-Position-Stat... "CT should not be used to screen for or as a first-line test to diagnose COVID-19"
zachguo 7y ago
The latest guidelines published by the Chinese CDC claimed so too, a CT scan is required, and RT-PCR tests have to be applied multiple times before claiming a patient is cured.
- TuringNYC 7y ago
  Any idea why a chest X-ray cannot be used, as is for TB?

I read that a CT scan outperforms the lab test at detecting it

by kuprel 7y ago

I read that a CT scan outperforms the lab test at detecting it

frisco 7y ago

CT scans involve a lot of ionizing radiation. Definitely something to be avoided unless necessary.

ridgeguy 7y ago
According to [1], a chest CT scan rad dose ranges from 4 to 18 milliSieverts. Annual background dose is ~3 milliSv. [2] states that a 100 mSv dose would increase risk of cancer by 0.5% (5/1000). [1] https://www.health.harvard.edu/cancer/radiation-risk-from-medical-imaging https://www.health.harvard.edu/cancer/radiation-risk-from-me... [2] https://www.scientificamerican.com/article/air-travel-exposes-you-to-radiation-how-much-health-risk-comes-with-it/ https://www.scientificamerican.com/article/air-travel-expose...
- hcknwscommenter 7y ago
  You cannot compare an annual background dose to the dose received in a CT scan. Similarly, the 100 mSv dose of your reference number 2 is an inappropriate comparison because it is spread out over time compared to a CT scan. Your premise is like saying, walking puts an impact of .8 J on my foot. I walk 10,000 steps a day. 10,000*.8 is 8,000 J. A bullet produces an impact of 168 J when fired from a .22 rifle into a human body. Therefore walking is much more dangerous than a bullet from a rifle.
  - ridgeguy 7y ago
    What you suggest seems plausible, but I can't immediately calculate, for example, DNA repair rate vs. X-ray photon flux and cross-sections. Can you point me to something that confirms incidence or severity of radiation-induced disease depends on flux rather than dose? Tnx.
    - Retric 7y ago
      Sun burns are known to significantly increase cancer risks vs similar exposure over longer periods. Sun burns are rather similar to accuse radiation poisoning suggesting similar issues.
    - hcknwscommenter 7y ago
      Both dose and flux matter.
  - carterehsmith 7y ago
    Above, there is a link to a report from Harvard Medical School, that claims otherwise. Maybe they are wrong, but a post on HN is not exactly a credible refutation.
    - hcknwscommenter 7y ago
      And yet, this Harvard Medical School link (not a report, not peer reviewed, but whatevs) clearly states that one CT scan of 4 to 18 mSV increases cancer risk by 0.7%, which is higher than the increase of 0.5% from 100 mSV exposure over a greater period of time. So, no. The Harvard Medical School link does not refute in any way my point. In fact, it supports my point.
  - unsrsly 7y ago
    The Sievert unit is based upon the Gray unit of radiation dose, but it also includes a weighting factor for the type of biological tissue that is exposed to radiation. You can also read up on the linear no-threshold model of radiation exposure for more information. In terms of cancer risk, radiation doses on a range from 1 mSv to 100 mSv can definitely be compared, regardless of the duration of the exposure. There is a range of higher doses e.g. above 1 Gy that would cause acute radiation syndrome if received all at once, where different biological effects would predominate.
- onlyrealcuzzo 7y ago
  0.5% absolute points or by 0.5%? Chance of cancer is already really low. Multiplying it by 1.005 doesn't make much of a difference. Adding 0.5% does.
ineedasername 7y ago
Wouldn't tracking a virus like this be such a necessary situation?

carbocation 7y ago

A CT scan is not an appropriate screening test for COVID-19. Also, that paper will have no clinical impact. Thread: https://twitter.com/drlukeor/status/1233547995192279040?s=21 https://twitter.com/drlukeor/status/1233547995192279040?s=21

carbocation 7y ago
Follow-up from the American College of Radiology: https://www.acr.org/Advocacy-and-Economics/ACR-Position-Statements/Recommendations-for-Chest-Radiography-and-CT-for-Suspected-COVID19-Infection https://www.acr.org/Advocacy-and-Economics/ACR-Position-Stat... "CT should not be used to screen for or as a first-line test to diagnose COVID-19"

zachguo 7y ago

The latest guidelines published by the Chinese CDC claimed so too, a CT scan is required, and RT-PCR tests have to be applied multiple times before claiming a patient is cured.

TuringNYC 7y ago
Any idea why a chest X-ray cannot be used, as is for TB?