Are CT Scans More Dangerous Than We Thought?

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CT scans expose patients to significant radiation, with a full scan delivering about 1,300 millirems, comparable to being 1.5 miles from a Hiroshima explosion. This exposure correlates with a 0.08% increase in cancer death risk, which rises to 3.75% for annual scans starting at age 25. Concerns were raised about the high number of unnecessary scans, costing an estimated $16 billion annually, and the lack of informed consent, with only 7% of patients aware of the risks. While some argue that the benefits of CT scans can outweigh the risks for serious health issues, others question the necessity of many scans ordered. Overall, the discussion highlights the need for better patient education and consideration of alternative diagnostic methods.
  • #61
Loren Booda said:
imabug,

I'm sorry. If it does have a legitimate answer, I have long since forgotten it.
:smile: :smile: :smile: :smile: :smile: :smile:
Welcome to the Old Dogs Club, Loren!
:smile: :smile: :smile: :smile: :smile: :smile:
 
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  • #62
Tsu,

I'm even enrolled in obedience school, taught by my girlfriend's 14 year-old Cocker, Dyna.
 
  • #63
Good boy! :biggrin:
 
  • #64
geometer said:
As I mentioned earlier, this is a population risk, not an individual risk. This means that in a population of 10,000 individuals, exposure at this level could be expected to result in as many as 8 additional deaths over what would normally be expected. It doesn't mean that your individual risk has increased by .08%

Are you a frequentist or something? If 10,000 people play russian roulette, and 1000 of them die, one can reasonably estimate that if one plays russian roulette, one's individual risk is 1 chance in 10 of dying.

[add]
The best thing I can in support of this position say is that if you have some reason to suspect that your radiation resistance is different from the rest of the population, your risk would be different from the population risk. But I can't see any reason one would believe that they were "radiation resistant" (or, for that matter, radiation prone).

Unless there is some reason to believe you are not representative of the population, population risk IS your risk.
 
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  • #65
Tsunami said:
If you're that concerned about radiation, stay away from the following:
Airplanes
Microwaves
Tobacco
Televisions
Smoke detectors
Lantern mantles
Building materials
Luminous watches and dials
Water
Rocks
Sunshine
Other people

This advice is extremely vague, and tends to divert the discussion from the actual risks, IMO (falsely downplaying them). Microwaves, for instance, aren't even ionizing radiation, so there is no radiation risk associated with using them.

One chance in 2000 of dying is significant. Think of your life as being worth at least $10 million dollars (perhaps more). You're talking about an insurance risk of say, $5,000 per exposure to the risk.

$10 mil isn't much, actually, when you consider how much the treatment for cancer will cost if you develop it, plus lost income & lost wages, even if you don't put any intrinsic value on your life (which would be distinctly odd).
 
  • #66
Tsunami said:
Hi. Wow. Did the ER kick our butts last night! I checked my scanner dose - an average chest scan runs a dose of 456mGy.cm. An abdomen is around 620 while a pelvis is around 600-650. Heads are less than 100. So your dose for a mammogram is higher than for most CT work.
the numbers you quote are for a quantity called dose-length product (CT dose/slice multiplied by total scan length), which is a measure of the total energy deposited during the scan. AFAIK, there is little information yet as to how this number relates to risk. To me though, it's one of those bean-counting quantities used to keep track of someone's total radiation exposure. Useful, but not quite sure how useful.

The mean glandular dose (dose to glandular tissue in the breast) from mammograms is typically 1-3 mGy.

edit: on the other hand, what is the conversion factor from rems to Grays? I'm actually going to have to finally LEARN the new Rad Safety Speak!? Why the hell did they change everything anyway? I know. It was just to mess with the heads of all of us old dogs, right?? :cry: :cry: :cry: :cry:
can of worms! can of worms! :smile:

convering from absorbed dose in gray (or rad) to dose equivalent/effective dose equivalent in sieverts (or rem) is a non-trivial task and involves many factors such as the type of radiation, duration and frequency of exposure and the types of organs exposed.

Different types of radiation (x/gamma, electron, proton, alpha) deposit energy at different rates along their track through matter (linear energy transfer). This gets bundled into a factor called the Quality Factor (QF) with x/gamma rays and slow electrons having a QF of 1 and alphas being much higher.

The same amount of each radiation also has a different effect on biological tissues, which gets bundled into a factor called relative biological effectiveness (RBE). For x/gamma and slow electrons, RBE is 1 while alphas have an RBE as high as 20.

Put those together with your absorbed dose (in gray) and you have a value known as Dose Equivalent (DE).

In addition, when it comes to radiation exposure in people, body parts and organs have different sensitivities to radiation. Organs such as the brain and skin are relatively radioresistant while other parts such as bone marrow and digestive tract lining are very radiosensitive. In general, any part that has rapid cell turn over will be the most radiosensitive. The radiosensitivity of the different organs gets bundled into a weighting factor (there is a list compiled by the NCRP in a document somewhere).

Apply this weighting factor to Dose Equivalent and you end up with a value known as Effective Dose Equivalent (EDE), which reflects the radiation risk associated with that exposure.

Lots of hand-wavy values that change over time as people do research and studies.
 
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  • #67
<groan> oh, god!... I hate conversions...[/size]

So, have you got that breast MR unit built yet? :biggrin:

I still don't follow how the Duke dose calculator can show 400mr for an abdomen CT and 600mr for a mammogram while the mGy for these are 10-30 and 1-3 respectively. This does not compute. What are your comments on the 120 KV for CT exams vs. the 25KV for mamms? Over the years this has been a key point in my discussions with Radiologists and physicists. They have all agreed that 25 does far more cellular (and subcellular) damage than 120.
 
  • #68
Tsunami said:
I still don't follow how the Duke dose calculator can show 400mr for an abdomen CT and 600mr for a mammogram while the mGy for these are 10-30 and 1-3 respectively. This does not compute.
The conversion factor between the SI (gray) unit and old (rad) unit of absorbed dose is 1 Gy = 100 rad. Similarly, 1 Sv = 100 mrem.

The absorbed dose delivered by most CT scanners is in the range of 1-3 rad (10-30 mGy). When you take into account the region being scanned and the radiosensitivities of the organs in the region, you will end up with another value in mrem (or mSv) reflecting the radiation risk from exposure. if the organs being scanned are radioresistant, then the calculated value in mrem (mSv) will be low. if the organs being scanned are more radiosensitive, then that value will be a higher.

Most people are taught that 1 Roengten (exposure) ~ 1 rad (absorbed dose) ~ 1 rem (biological risk), which is ok for a 1st order approximation. But to go from absorbed dose to biological risk accurately, you need to consider the region being exposed, the radiosensitivity of the organs being exposed and duration of exposure.

What are your comments on the 120 KV for CT exams vs. the 25KV for mamms? Over the years this has been a key point in my discussions with Radiologists and physicists. They have all agreed that 25 does far more cellular (and subcellular) damage than 120.

The reason low kVp is used for mammography is to get image contrast. This allows fatty tissue to be distinguished from glandular tissue, and soft tissue masses to be distinguished from the rest of the breast tissue. Using a higher kVp would result in less radiation dose, but less contrast and decreased visibility of soft tissue masses.

There is no question that the low kVp gets absorbed more and results in an increase in cancer risk. In most other diagnostic modalities, we are using aluminum and copper filters to remove low energy x-rays from the beam to reduce radiation dose to patients.

The real question is whether this risk of developing a future cancer a decade or two down the road due to mammography screening outweighs the risk of dying in a couple of years from an undetected cancer growing now.
 
  • #69
Bump ;-/

(Reuters) - Radiation from CT scans done in 2007 will cause 29,000 cancers and kill nearly 15,000 Americans, researchers said on Monday.

http://www.reuters.com/article/2009/12/14/us-cancer-radiation-idUSTRE5BD4VD20091214


Diagnostic tests after a heart attack linked to increased cancer risk

http://www.theglobeandmail.com/life/health/scans-boost-cancer-risk-for-heart-attack-survivors-study-finds/article1897387/
 
  • #70
Wow. This must break some record in terms pf necroposting.

Zz.