All That Radiation!

The ultrasound and MRI don’t involve radiation. It would be a good idea to keep a running list of all of the x-rays, CAT scans, sestamibis, etc. that do use radiation that you are exposed to. Include time and place and if you are asked to repeat any for some reason, try to have it done on the same machine- it makes for a better comparison. No one else will be keeping track. Also, I hate to say it but facilities that own the machines love to use them (think $) especially emergency rooms. Once you have a scan that finds something incidentally that they weren’t looking for (like an asymptomatic benign lung nodule which many people have) they will want to follow it for 2 or 3 years to see if it grows. That happened to me and after the third one, the radiologist wanted a fourth because she said it was done on a different machine. (of course no one bothers to ask where your last one was taken- I could easily have returned to the last facility. At that point I said, “Hell no!” One doctor told me that if you have had three and nothing has changed, then it is time to stop. Luckily, newer machines apparently use less radiation.

It’s interesting to hear that mammos may become a thing of the past in Europe. Are they planning to do MRIs instead?

There's a nifty calculator here: http://www.xrayrisk.com/calculator/calculator-norm...

you enter the scan you had (note mammograms are unilateral so if you had both sides done, make sure to indicate 2 in number of exams, then click calculate, then click Add this to your report. You can get a tally of what you were likely exposed to & a calculation of risk.

I also find the 4th page of this pdf useful - it's a chart comparing the dosages of radiation from various procedures https://www.arpansa.gov.au/sites/g/files/net3086/f...

This thread is interesting to me because I have been participating in a related thread called "Is Ignorance Bliss" or something close to that and there are posters on there complaining because they are not getting regular CTs and PET scans to screen for mets. There doesn't seem to be awareness in those arguments for the dangers of these scans and why current guidelines do not allow for them to screen for mets. CTs are harmful beyond radiation of course because the dyes used are dangerous. The kidney blood test required immediately prior to a scan no matter how recently you already had that test illustrates quite clearly what a hit your kidneys are going to take. My first MO did not follow the guidelines and after surgery but before chemo ordered a CT which found a minute lung nodule and tiny spots in the liver. Very common in people my age but MO wanted another CT in 3 months. I refused. But because radiologist wanted one in 6 months I had another CT in Feb. No change. Protocol was to have one more in 6 months which would be this month. Last week I discussed this with my new MO and he agreed with me that there was no need for a followup as I have no clinical signs and even the radiologist did not call for a recheck. I totally agree with everyone who is concerned about too many tests with too much risk. What do you gain if you survive breast cancer but your kidneys fail or you get other cancers from the radiation. Polly

Hi Roxanne:

tl:dr I wouldn't worry but read on if you want to know why.

The radiation from mammograms does not stay in your body at all. You can think of X-Rays from an external source like an X-Ray machine like light from a light bulb. It's emitted when the machine is on and goes away when the machine is off. The difference between X-Rays and light from a light bulb is that we are kind of translucent/transparent to X-Ray photons...the "light" that is the X-Rays can shine through us, but some of the photons "collide" with the molecules in our DNA and are high enough energy to knock some of the atoms off and damage it. This type of radiation is called "ionizing radiation".

We are exposed to ionizing radiation in small amounts on a regular basis in the form of UV light from the sun, gamma rays from things in outer space, and various forms of ionizing radiation from small particles of radioactive minerals and elements in the environment from naturally occuring sources and nuclear testing and accidents. These sources of radiation contribute to what is called "background radiation".

In most instances, when cells are damaged by radiation, they self destruct or are destroyed by the body. This is how radiation is used to treat cancer. But in some rare instances the damage constitues a mutation that causes the cell to become cancerous or sets it up for it or it's prodigeny to become cancers down the road. This is how radiation causes cancer. It should be noted that anything that damages a cell at the level of the DNA can result in cancer. The more often ionizing radiation cells are bombarded by, the greater the chance of a cancer causing event.

The odds of cancer from one or even a few annual x-rays or mammogram are very low, especially today because technology enables them to use very little radiation. You are more likely to end up with cancer from sun exposure.

The PET/CT is a different story.

The CT part of the PET/CT is just like getting an X-Ray only you are getting a lot of them at once. The more of your body that is being imaged, the more the more X-Ray images have to be taken. How dangerous is this? The amount of radiation a CT scanner emits varies a lot between scanners and facilities but in the U.S., the risk of cancer is calculated to be 1 in 2000 from a typical CT which is not "full body". It puts it in the "limit use" category.

The PET part of a PET/CT uses radioactive isotopes that are injected in to you. They are attached to a substance that hypermetabolic cells such as cancer cells uptake quickly an in large quantity, concentrating the radioactive isotopes and causing the radiation to be emitted from that spot at levels the detectors in the scanner can detect. That shows up on the images as a glow. The radiation from this substance dies off after a few hours.

A PET and CT can be done separately but are often done together when looking for cancer.

The radiation exposure from a whole body PET/CT is considered to be significant compared to how hoe much radiation we are exposed to on a regular basis. A whole body PET/CT in the U.S. exposes a person to about 8 years worth of background radiation and that puts them in the "not for routine use" category. But it's important to understand what is meant by "significant" with respect to cancer risk.

Your risk of getting cancer from a single whole body CT or PET/CT in the U.S. is thought to be around 1 in 200 when you are 20 and declines with age.

While the risk of cancer from a whole body PET/CT for any one individual is relatively small, the medical community has too look at it in terms of how it translates to incident among the populations.

If 200 20 year olds have whole body PET/CTs they figure 1 will get cancer from it. If 1 million 20 year olds get whole body PET/CT they figure 5,000 will get cancer from it. Around 2 million PET and PET/CTs are done per year in the U.S.

I would not worry about a few mammograms or conventional x-rays used in regular screen or for diagnostic purposes.

I would not worry about a single full body CT or single full body PET/CT as they are typically only done when it is thought there is a more significant threat to your life or QOL from something else.

Lots of great info in this thread.

Marijen, I wish everyone would read that consumerreports.org article. It beautifully summarizes many key points.

I love that they also explain that we should not assume all doctors know the amount of radiation exposure involved in a particular test; and that we should tell them we want to minimize exposure, because most patients are not that concerned, even though they should be.

If I get your question: radiation dose to a body region, say, breast, depends on the test used, so, ultrasound involves no radiation, a mammogram involves some, a CT scan involves more radiation. If this is not what you are asking, let us know.

radiation is not really 'good' for us, no more than surgery or chemo are. It's just that in certain cases the benefits outweigh the risks. Radiation treatment for cancer is targetted to cancer cells & healthy tissue is supposed to have limited exposure. But radiation treatment itself does have a small risk of triggering a cancer later. So does chemotherapy.

Again, it's like most medicines & treatments: benefit v risk

Ahhh, well, it's the old saying "the dose makes the poison"

Radiation for cancer is MUCH more powerful than the radiation from scan. For example, I'm getting a total of 42.5 Gy (in 16 fractions, ie spread in 16 doses) + 10 Gy boost to the tumor bed (in 4 fractions).

1 Gy (short for gray) = 1,000 mSv (millisievert)

for comparison sake, a mammogram is 0.3 mSv so I'll be getting 175,000 times as much radiation to my breast as you would from a mammo

Strong radiation can kill cells - hence its usefulness in treating malignancies.

lifetime cumulative exposure to very weak radiation can cause some cells to mutate while replicating - hence its risk in triggering a malignancy.

Does that help?