4 ms·

There's a letter here from a group of X-ray imaging and cancer experts recommending further study: http://www.scribd.com/doc/35498347/UCSF-letter-to-Holdren-con

by DanI-S 16y ago

There's a letter here from a group of X-ray imaging and cancer experts recommending further study: http://www.scribd.com/doc/35498347/UCSF-letter-to-Holdren-concerning-health-risks-of-full-body-scanner-TSA-screenings-4-6-2010 http://www.scribd.com/doc/35498347/UCSF-letter-to-Holdren-co...

yummyfajitas 16y ago
I'm no expert, but I have a basic understanding of radiation physics. And this letter reads like FUD: The majority of their energy is delivered to the skin and the underlying tissue.Thus, while the dose would be safe if it were distributed throughout the volume of the entire body, the dose to the skin may be dangerously high. This statement is very shady. When a photon interacts with a cell, it has a certain (small) probability of causing a carcinogenic mutation. The probability that the radiation is safe is (1-P)^N, where N is the number of interactions [1]. The fact that it is all deposited in the skin is irrelevant to leading order [2], this simply makes skin cancer more likely than breast or liver cancer. I.e., if the dose in the form of a chest x-ray caused a 1e-9 chance of skin cancer and 1e-9 chance of breast cancer, it instead causes a 2e-9 chance of skin cancer with comparably reduced breast cancer risk. [1] I'm ignoring high field (nonlinear) effects, since if the field were strong enough to cause them, it would probably also vaporize the person being scanned. [2] It's actually a good thing since many skin cells are dead or will soon die, and thus carcinogenic mutations will harm them less.
- DanI-S 16y ago
  "When a photon interacts with a cell, it has a certain (small) probability of causing a carcinogenic mutation." I'm also no expert, but surely there is a risk of more significant, irreparable genetic damage accumulating if several photons interact with the same skin cell, as opposed to those same photons interacting with several different cells throughout the body?
- jbjohns 16y ago
  >I'm no expert Well they are, so perhaps we should give their word a bit more credibility than yours?
  - yummyfajitas 16y ago
    I'm not asking you to take my word for anything. My reasoning is laid out and explicit. If I made a flaw, point it out. But I guess it's much easier to criticize me for being a mathematical physicist rather than a medical doctor. After all, finding flaws in an argument takes work!

by DanI-S 16y ago

yummyfajitas 16y ago

I'm no expert, but I have a basic understanding of radiation physics. And this letter reads like FUD: The majority of their energy is delivered to the skin and the underlying tissue.Thus, while the dose would be safe if it were distributed throughout the volume of the entire body, the dose to the skin may be dangerously high. This statement is very shady. When a photon interacts with a cell, it has a certain (small) probability of causing a carcinogenic mutation. The probability that the radiation is safe is (1-P)^N, where N is the number of interactions [1]. The fact that it is all deposited in the skin is irrelevant to leading order [2], this simply makes skin cancer more likely than breast or liver cancer. I.e., if the dose in the form of a chest x-ray caused a 1e-9 chance of skin cancer and 1e-9 chance of breast cancer, it instead causes a 2e-9 chance of skin cancer with comparably reduced breast cancer risk. [1] I'm ignoring high field (nonlinear) effects, since if the field were strong enough to cause them, it would probably also vaporize the person being scanned. [2] It's actually a good thing since many skin cells are dead or will soon die, and thus carcinogenic mutations will harm them less.

DanI-S 16y ago
"When a photon interacts with a cell, it has a certain (small) probability of causing a carcinogenic mutation." I'm also no expert, but surely there is a risk of more significant, irreparable genetic damage accumulating if several photons interact with the same skin cell, as opposed to those same photons interacting with several different cells throughout the body?
jbjohns 16y ago
>I'm no expert Well they are, so perhaps we should give their word a bit more credibility than yours?
- yummyfajitas 16y ago
  I'm not asking you to take my word for anything. My reasoning is laid out and explicit. If I made a flaw, point it out. But I guess it's much easier to criticize me for being a mathematical physicist rather than a medical doctor. After all, finding flaws in an argument takes work!