Are CT Scans Safe

[The Jogger]

I had one about three years ago to do with kidney stones and pain in the side and I guess it was fine, now urology want to do another one re side pain again. Its a scan of the whole area probably prostate kidneys bladder etc. I was thinking about not going for it as I'm due the camera again. Concerned over the radiation that turned out to be unnecessary last time and symptoms are the same. I think I'll do the camera firs, cancel ct and talk to the urologist about it first?

 

[ColinJ]

I have had 4 CT scans done in the past couple of years after my clotting problems. I don't really fancy volunteering for many more because each one is a pretty massive dose of x-rays. According to this article one CT scan might expose a patient to the equivalent radiation dose of between 150 and 1,100 conventional x-rays!

I would discuss your concerns with the doctor.

 

[ColinJ]

Oh, and I asked the radiographer about allergic reactions to contrast dye. I was told not to worry about it. I found out later that my brother-in-law had nearly died from an adverse reaction when he was scanned!

 

[Wobblers]

Firstly, they won't ask you to have a CT scan if they don't think there's a clinical need. There are only so many CT machines, and they're always in use, with long waiting lists (I had to wait almost a month before getting one to determine just how badly I'd damaged my ankle) so this isn't a procedure that they're just going to casually ask for.

Secondly, the dangers of radiation are almost certainly exaggerated. As the Scientific American article says, most work on radiation risks are based on the A-bomb survivors. But most of them received large doses. A linear dose/effect relationship has been used to extrapolate cancer risk down to the small doses you'll receive in CT scans (and it is small). However, research in recent years has cast doubt on this assumption. In fact some research suggests that low radiation doses have a beneficial effect. Put simply, the risks have almost certainly been substantially over estimated - otherwise workers in the nuclear industry and users of the major scientific neutron and x-ray facilities would be dropping like flies. They're not. While there are many things to worry about, CT scans aren't amongst them.

 

[slowmotion]

I had one twenty years ago when I had a horrendously prolapsed disc in my back. In those days it was a real privilege to be invited to slide into the tube. I seem to have survived. Don't worry about it.

 

[classic33]

I've had a few done over the years and I'm still here. If you are bothered about the radiation dosage you might receive, I'll point out that they have access to your records with regards any previous X-rays you may have had and the interval between each.
Never had a CT or MRI scan refused, but I was refused an X-ray years ago because the radiographer felt that I'd too many done over the previous year. Hazard of hitting the head on something solid, whilst in a fit.

See CT Scan Radiation Risk

The dye as pointed out by @ColinJ might be of more concern. This is covered in a standard set of questions asked beforehand.

 

[Pumpkin the robot]

I have one every 6 months to see if the tear in my aorta has not increased in size. I have not actually thought about the radiation dosage, I wouldnt have thought they would do it so often if there was a risk.

 

[ufkacbln]

Radiation "damage" is always possible!

IF a packet of radiation hits a DNA strand and breaks it and it repairs correctly - no damage occurs

However IF the DNA strand repairs incorrectly, and IF that cell survives and IF that cell then replicates and IF that replicating cell forms a grup of cells and IF that group of cells is malignant then you have a problem.

So really it is down t chance.

However these chances are all very small

Modern CT scanners are very efficient and teh dose used has dropped over the years.

To put this into perspective, depending upon the scanner, it is often no greater a risk than that of having an accident whilst driving to or from the appointment, taking a Holiday in a high natural radiation area like Cornwall for a fortnight or half a dozen transatlantic flights

I will get some more accurate figures and some references whilst at work

If you wish to continue the discussion on here then I am quite happy to do so, or if there is something you wish to discuss off the forum, please feel free to use the conversation option

 

[MartinQ]

A bit like Colin I've had a few (~5) a few x-rays and a nuclear v/q test, in the last couple of years. Must be addicted to the stuff. A good reply from a medic who got clots recently, from http://www.dailystrength.org/c/Pulmonary_Embolism/forum/18697455-willing-help-i/page-2

CT scans. A chest CT angiography (used for diagnosing PE) is more radiation than just a regular chest CT. It's equal to about 2 years of "average" background radiation exposure in the U.S. (approximately nine months if you live in Denver, where the elevation means more cosmic radiation exposure and there are uranium deposits in the soil). What does this mean in terms of risk?
Well, one in five people in the U.S. will develop cancer in their lifetime. One chest CT means that as many as 1 in 1000 people who are part of the 4/5 that wouldn't have gotten cancer will get it from the CT. And that's the risk of developing a cancer spread throughout the patient's lifetime. So if you're young, there's more time after the exposure for a cancer to develop than if you're older. The time frame used to calculate the increased risk is 30-40 years. So if you're 70 you don't have as much to worry about as if you're 20, because the chance that you are going to live to be 110 is about the same if you have a CT or if you don't.
That being said, younger people have stronger immune systems and better cellular repair systems than older people do. So they have a lower chance of "mis-repair" of radiation-damaged cells than older people do, which is what causes these cancers down the road.
Also, one must take a lot of the information out there about radiation exposure with a grain of salt. Most of the studies conducted on it were done on survivors of Hiroshima and Nagasaki or on patients who had neck irradiation in the mid-1900's as children to treat enlarged thymus glands. These patients were exposed to very high doses in a very short time period, whereas our modern radiology testing exposes patients to smaller doses over a longer time period. Dose rate does matter, to a certain extent. Of course, someone already diagnosed with cancer who has had 30-40 CTs over a 5 year period and who is also having radiation therapy (which is many, many CT's per treatment) has reached a point where exposure is exposure.
All in all, one or two CT scans performed on a patient who could very well die without the information the CT provides poses a pretty minimal risk to the patient. It's all about benefit vs. risk. I see my physicians wrestle with this on a daily basis. Your doctor, you see, can't just order a CT or Nuclear Medicine study without it being approved by the specialist physician. Our physicians routinely reject requests for exams if they feel that there is a more appropriate exam to diagnose the patient, especially if all options for not using radiation or using less radiation have not been exhausted (MRI, ultrasound, plain X-ray, etc.)
Many patients who have large amounts of medical radiation exposure (PET/CT every 3 months, for example--which is 7 years of background each) already have a malignancy. The benefit for them is targeted treatment. Being able to tell whether the chemo and radiation treatments are bringing about a reduction in tumor size or number is a very good way of judging the effectiveness of treatment or a need to change course. For these patients, the risk of developing an additional cancer is negligible compared to their risk of succumbing to their present cancer.
I would say that if you go into the ED with all the symptoms of a recurrence that CTA is the fastest, most accurate way to diagnose a PE and get you the immediate treatment you require to save your life. I wouldn't necessarily be worried about the radiation exposure at that moment, because you might not have 30-40 years of life left without that treatment. Recheck with CT on a non-symptomatic patient who wants to know if the clots are gone? Not so fast. What is the risk to the patient from not doing the test? Minimal. So don't do the test. If your symptoms come back, by all means get into that machine so you can get diagnosed and treated.
It's like driving your car on the freeway at rush hour. Do you take the surface streets because it's safer or the freeway because it's faster? You do benefit vs risk analysis in your everyday life all the time, you just don't realize it.
Just one more note. That CT scan is 7mSv. I know that number doesn't mean much to you, but realizing that every single radiation worker in this country is allowed 50mSv per year of employment as occupational exposure over top of the incidental background everyone else gets should put it in some perspective. I've been doing this 22 years. That means I've been allotted 1100mSv of extra exposure for that time just to do my job. That's 150 CT scans. Just for some idea of scale. That doesn't mean you still shouldn't do your own benefit/risk analysis on any non-emergency scanning. Bring your doctor into the conversation. Ask what other tests can be done. Ask what happens if you don't do the test, if the diagnosis can't be confirmed any other way, if you put it off and don't get the proper treatment. Be your own advocate, but out of a due amount of caution, not sheer terror.

 

[SatNavSaysStraightOn]

To the OP, talk with your urologist and GP and go with their advice. It may be possible for some other non-radiation using test to be used (both ultrasound and MRI's are radiation free - I used to work with nmr technology in a chemistry lab).

otherwise workers in the nuclear industry and users of the major scientific neutron and x-ray facilities would be dropping like flies. They're not. While there are many things to worry about, CT scans aren't amongst them.

From personal observation, I only wish that was true for my mother's friends. - sadly I think it only applies to the current generation and the current equipment in use which for the OP is good news, but not so for my family or my mother's friends. Her friends (the other nurses she trained with and worked with) have been dropping dead like flies for the last 20 odd years and no-one who knows their background has failed to notice that they are all dying of the same thing - cancer or leukaemia. the only difference has been 'of what'... There could be other factors involved, such as the era they were in, not exactly known for its lack of smoking and the likes, but also the fact that even with standard x-rays nurses were not shielded from the radiation and the radiation dose was much higher then as well... None of them have died from anything else, unlike their partners/husbands.

To the OP... there are risks, but from current experience (my sister collapsed with a bleed on the brain after knocking herself out) they won't do another CT scan on her unless she collapses again (which is about every 6 months at the moment, with no reason known). She had 3 done inside 6 months before they called it as too many and now have her on this 'restriction'.

I have one every 6 months to see if the tear in my aorta has not increased in size. I have not actually thought about the radiation dosage, I wouldnt have thought they would do it so often if there was a risk.

I would imagine the risk of it increasing in size and the life threatening consequences are far higher that the risks regarding radiation dosage with modern equipment.

 

[classic33]

The time they refused to X-ray me, I was issued with a lead blanket, whilst they X-rayed the ankle I'd snapped.

 

[machew]

 

[swansonj]

Firstly, they won't ask you to have a CT scan if they don't think there's a clinical need. There are only so many CT machines, and they're always in use, with long waiting lists (I had to wait almost a month before getting one to determine just how badly I'd damaged my ankle) so this isn't a procedure that they're just going to casually ask for.

Secondly, the dangers of radiation are almost certainly exaggerated. As the Scientific American article says, most work on radiation risks are based on the A-bomb survivors. But most of them received large doses. A linear dose/effect relationship has been used to extrapolate cancer risk down to the small doses you'll receive in CT scans (and it is small). However, research in recent years has cast doubt on this assumption. In fact some research suggests that low radiation doses have a beneficial effect. Put simply, the risks have almost certainly been substantially over estimated - otherwise workers in the nuclear industry and users of the major scientific neutron and x-ray facilities would be dropping like flies. They're not. While there are many things to worry about, CT scans aren't amongst them.

ooo errr, @McWobble, controversial stuff! Are you really aligning yourself with the hormesis lobby? [inset suitable smiley to indicate I'm being friendly not critical]

As you are clearly aware (but others may not be so familiar), most radiation protection (below the doses that produce acute, deterministic effects) is indeed based on LNT - linear no threshold. But as @Cunobelin suggests, that's not as silly as it can sometimes sound - it's based on the premise that each alpha particle (or beta or gamma or neutron) has a certain probability of causing a DNA strand break, and each strand break has a certain probability of resulting in a cancer. So the chance of getting cancer depends on how many strand breaks you get which depends simply on how many bits of radiation your body has stopped in total, not on how rapidly they were accumulated. Or that at least is the argument for LNT.

Of course there are alternatives suggested. Trouble is, this is a political as well as a scientific area, and when we look at the alternatives that are suggested, we need to be aware of the interests of those promoting them. Basically, the green movement (or those bits of the green movement who oppose nuclear power) have an interest in low doses and low dose rates having GREATER effect than LNT suggests, because those are the doses associated with nuclear plants, and if the risks were higher than the LNT orthodoxy, the health argument against nuclear power would be strengthened. Conversely, the nuclear industry has an interest in low doses and low dose rates being LESS harmful than LNT suggests, because then nuclear power looks safer, and they don't have to bother expensively remediating sites any more.

What everyone (except the lunatic fringe) agrees on is that, as you say, risks from the doses received from xrays, occupational exposures, etc, are low whether assessed under LNT or an alternative. Which is why I'm not fully persuaded of your comment about not seeing occupationally exposed workers dropping like flies. There have been a lot of epidemiological studies of occupational groups - a new one looking at the BNFL workforce came out earlier this year - and while they all generally find excess risks, they all struggle to say anything truly definitive about whether those excess risks are LNT-compatable or not because the risks are just too damn small to start with.

 

[PK99]

Chapter and verse with dose comparisons

http://www.radiologyinfo.org/en/safety/?pg=sfty_xray

 

[The Jogger]

Thank you all very much for taking the time to reply to my query/worry. It has been really informative and reassuring. Lets hope the head can rationalise all this and calm down. Just received a copy of the letter from my consultant to my GP saying reason for CT is because of my history of kidney stones, the pain in the side and neither x ray or ultrasound could detect a stone.