Are CT Scans More Dangerous Than We Thought?

[Tom McCurdy]

I was recently reading pop sci and it revealed the following stats

For one full ct scan

• 1,300: Radiation dose in millirems
• 1.5 miles: distnace you would need to bee from the Hiroshima atomic explosion to receive an equivalent does
• 29: radiation does in mrem from smoking pack of cegarettes
• .08%: increase in risk of death from cancer

Also

• 3.75%: increase in risk of death from cancer if you have a full body CT scan annualy from age 25
• 300: Average annual radiation dose from natural sources a year in millirems
• 1: Average annual radiation doese in mrem from eating one or two bannas a week
• 57 million Number of full body CT scans performed in 2003
• $16 billion Estimated annual cost of unecessary diagonstic imagine
• 7%: Percentage of patients infromed of the risks of their CT scans

What are your opinions on this

 

[ZapperZ]

I'm sure people do CT scans for the fun of it, when they are bored with nothing better to do. We should outlaw such recreational CT scans, especially when they are people who are obviously addicted to them and want to do them once a year from the age of... what... 25?

Let me first apologize for what I'm about to say, but it is highly irresponsible for you to spew such meaningless statistics without even mentioning the possiblity of the benefits of such an procedure might outweigh the risk. There are people with serious illness who would tremendously benefit for such diagnostic procedure, the same way a memogram, dental x-ray, etc. would be even with the associated risk. People seem to forget that they accepted larger risks than these each day they get onto an expressway going to work.

Zz.

 

[Tom McCurdy]

I agree--- take nothing away of the importance of CT scans--- the facts i got were from an article from popsci that just gave the stats as i have mentioned... I do wonder about the number of ct scans that are done on doctor recomindation that could be avoided--- 16 billion dollars in scans were not needed

 

[ZapperZ]

I agree--- take nothing away of the importance of CT scans--- the facts i got were from an article from popsci that just gave the stats as i have mentioned... I do wonder about the number of ct scans that are done on doctor recomindation that could be avoided--- 16 billion dollars in scans were not needed

I question the number that is cited, and I will also question who decided that these scans were "not needed". This is especially true when insurance companies are scrutinizing everything a doctor is requesting. That many unneeded order on an expensive diagnostics passing through tight-wads insurance companies? I don't think so...

Zz.

 

[Hurkyl]

Well, my first and overwhelming reaction is "So what?"

 

[russ_watters]

Well, my first and overwhelming reaction is "So what?"

Me too. The reason, as already stated, these stats are utterly devoid of context.

 

[geometer]

Finally, from a health risk standpoint, an acute dose of 1300 millirem is negligible. Radiation workers (those who work regularly with radioactive materials) are allowed to get up to 5000 rem per year.

 

[Tom McCurdy]

Me too. The reason, as already stated, these stats are utterly devoid of context.

As i mentioned I got these stats directly from Popular Science page 48 November issue.

The sources are
American College of Radiology, David J Brenner/Columbia University Medical Center, U.S> Food and Druge Adminstation, David C Levin/Thomas Jefferson University Hospital, Natinal instuutes of Health, Nuclear Energy Institute, Yale University of Medience

It is hard to be out of context when the whole article was just the stats...

The thing that gets me is the 16 billion dollars and 7 percent... people should know when they need a CT scan and when other options are avalibable. I have had to get

CT Scan
X-ray
MRI

and now am supose to get a bone scan

for a groin injury... the doctors haven't done anything in pinpointing what has been the source of the injury that I have had for over a year...

a .08% increase in risk of death by cancer is ennough to make me look at other options first... plus the cost of the scans are ridicolus

 

[Tom McCurdy]

Finally, from a health risk standpoint, an acute dose of 1300 millirem is negligible. Radiation workers (those who work regularly with radioactive materials) are allowed to get up to 5000 rem per year.

I am not sure if it makes a difference if you get 1300 within an hour vs 5000 rem per year... but if it doesn't then 5,000 mrem should be taken a lot more seriously with the publication of data like this

 

[geometer]

I am not sure if it makes a difference if you get 1300 within an hour vs 5000 rem per year... but if it doesn't then 5,000 mrem should be taken a lot more seriously with the publication of data like this

First, my sincere apologies. Radiation workers are allowed to get 5,000 millirem in one year, not 5,000 rem! Whew!

But, that said, an acute dose of 1300 millirem or an acute dose of 5,000 millirem will have no somatic effects. For everyone's information, here is some data on acute radiation dose effects:

There will be no noticeable health effects from acute radiation exposures until the level reaches about 35,000 to 50,000 millirem. At that level there will be temporary detectable blood changes

Around 100,000 millirem, some people will exhibit the symptoms of radiation sickness: fatigue, nausea, vomiting. They will recover in a few days.

About 50% of people exposed to an acute dose of 450,000 millirem will die without medical treatment. With medical treatment, the percentage of deaths will go down, but some people will still die at this level of exposure.

Essentially 100% of those people exposed to 1,000,000 millirem or more will die, even with medical attention.

The main effect of chronic exposure to low levels of radiation is an increase in the chance of cancer. But, the data reported above (.08% increase in the chance of cancer after exposure to 1300 millirem) is misleading. I believe this comes from a 1990 report by the National Research Council's Committee on the Biological Effects of Ionizing Radiation (so it's not new data). This is actually a population risk not an individual risk. The proper interpretation of this is that exposing a population of 10,000 people to an acute dose of 1,000 millirem could result in as many as 8 cancer deaths in excess of what would be the normal number. It doesn't mean that your personal risk of developing cancer has increased by .08%. The normal number of people expected to die of cancer in a group of 10,000 is 2,000.

 

[Tom McCurdy]

thank you for your information--- I was not specifically trying to support the article as much as see some discussiona bout the figures your response was very helpful

 

[geometer]

thank you for your information--- I was not specifically trying to support the article as much as see some discussiona bout the figures your response was very helpful

You're welcome. I figured you were looking for some context for that information.

 

[pervect]

I was recently reading pop sci and it revealed the following stats

For one full ct scan

• 1,300:Radiation dose in millirems
• 1.5 miles: distnace you would need to bee from the Hiroshima atomic explosion to receive an equivalent does
• radiation does in mrem from smoking pack of cegarettes
• increase in risk of death from cancer

Let's see. Google finds

http://www.safety.duke.edu/radsafety/ct_ed/default.asp

With the default mass of 70kg, I get

402 millirem for abdominal CT
544 for chest CT

That's a total of 946 mrem, about 1 rem. There's no entry for "whole body CT", but the sum of chest + abdomen is reasonably close to your figure, though your figure is slightly high.

The EPA currently estimates

http://www.epa.gov/radiation/understand/health_effects.htm

What is the cancer risk from radiation? How does it compare to the risk of cancer from other sources?

Each radionuclide represents a somewhat different health risk. However, health physicists currently estimate that overall, if each person in a group of 10,000 people exposed to 1 rem of ionizing radiation, in small doses over a life time, we would expect 5 or 6 more people to die of cancer than would otherwise.

In this group of 10,000 people, we can expect about 2,000 to die of cancer from all non-radiation causes. The accumulated exposure to 1 rem of radiation, would increase that number to about 2005 or 2006.

To give you an idea of the usual rate of exposure, most people receive about 3 tenths of a rem (300 mrem) every year from natural background sources of radiation (mostly radon).

For a CAT scan, you get the dose in one lump, but if we use these figures as an estimate, that's about 1 chance in 2000 of dying of cancer as a result of the exposure. This is a small fraction of your chance of getting cancer "naturally". The EPA doesn't mention this, but as I recall, it will take 20-40 years after exposure for the cancer to develop. If you are old enough when you get the exposure, you may not live that long anyway . Somewher or other, I saw age adjusted charts, but I don't recall where or by whom, and I doubt that they are current in any event.

Sidenote & political comment: It's a bit hard to tell who to believe. I've seen far to many "pro-radiation" people in the health science fields for my comfort level - people who believe ionizing radiation is good for you. (It's very likely that they are having their research funded by pro-nuclear interests, too.).

One chance in 2000 of death is nothing to sneeze at. If you are sick (and especially if you are already old and sick), you have to factor in the benefits. If there is a 1% chance the CAT scan will find something serious that would otherwise be missed, this would far outweight the .05 percent chance that it kills you. It's hard for me to asses the specifics of "how good" CAT scans are.

 

[geometer]

Sidenote & political comment: It's a bit hard to tell who to believe. I've seen far to many "pro-radiation" people in the health science fields for my comfort level - people who believe ionizing radiation is good for you. (It's very likely that they are having their research funded by pro-nuclear interests, too.)

There are three major competing theories with regards to the effects of radiation exposure. The one that current exposure and radioactive material cleanup regulations are based on is the "Linear, No Threshold" theory. This theory assumes that any amount of radiation exposure, no matter how small, is harmful and that the consequences of exposure increase linearly from zero.

The second theory is basically the same except that it assumes there is a threshold exposure level, below which radiation has no adverse effects. There is some evidence of this, but it's still not widely accepted.

Finally, and this goes to what prevect was saying, there is the "Radiation Hormesis" theory. This theory says that small doses of radiation are actually beneficial. They are supposed to "tune up" your immune system. Believe it or not, there is some evidence to support this, but it is in a distant third place among most health physicists. There was however, an article in a recent Science magazine about the Radiation Hormesis theory.

There is active research going on concerning all three theories.

 

[Tsu]

Well, holy cow. Do I have a LOT to say about this! Unfortunately, there is an election going on that I am very involved and active in so, most of what I'd like to say will have to wait.

I have been an x-ray technologist for over 30 years. I have done general radiography, mammograms (NOT MEMOrams, Zapper Z! That was GREAT! I'm picturing us trying to compress a stack of MEMO's with the mammogram machine... Sorry. I digress... ) and I have done CT scans for almost 25 of those years.

CT scans ARE one of the highest dose exams you can have. But there are a number of factors to consider. The average 'technique' used on an abdominal helical CT is 400MA at .5 sec (or 200 MAS) at 120 KV. Generally speaking, the higher the KV, the more penetrating the beam. Also, the higher the MAS, the more photons you HAVE penetrating the part you are imaging. So with 200 MAS at 120 KV you have a moderate amount of photons going through the body at maximum penetration (120-130KV is typically the highest we use in diagnotic imaging). This combination keeps the biological damage to cells/tissues considerably lower than using LOW KV and HIGH MAS.

Now, consider the amount of radiation received to JUST the breast area (including the sternum - which is a major producer of bone marrow which makes your blood) during a routine screening mammogram. According to pervect's link to Duke's dose calculator, each image delivers an average dose of 143mr. Multiply that by 4 (two images of each breast) and you have considerably more dose than your average abdominal CT. What makes the dose so bad, is that the average kilovoltage setting for mammography is 25 KV. This is a very low-penetration photon going through the breast and doing MUCH damage along the way to its exit - IF it exits. A lot never make it out of the breast. To compound the problem, you need a VERY high MAS - LOTS of photons - to produce the detailed images you need in mammography. I've often wondered if mammogram dosage is the real reason why breast cancer is on the rise. I've discussed this with numerous radiologists and many of them have (off the record of course) have actually admitted to wondering that, too. When I asked them why no one is doing any kind of study on this, they indicated that because mammography is such a GIANT money-maker, there is just no incentive to find a different way of imaging breasts. I personally think that MR is the way of the future for breast imaging, but at this time, it is not a technological or financial possibility.

So, while the concern about the dose in CT scans is definitely warrented, (and please know that your CT technologists are HIGHLY trained professionals and ARE using the lowest dose possible to produce the best diagnostic image for your patricular exam - we are required to produce evidence of continuing education to maintain licensure), I feel there should be a WHOLE LOT more concern about mammogram dosage.

Gotta go to the dentist, now. See ya!

 

[Necrosis]

Ok, so I don't think most those numbers are that bad, but I do have a problem with the 7% of patients being informed of these side effects. The benefits outweigh the risk in most cases as stated earlier, but wouldn't you want to know the risks before going through one of these procedures? Or equivalence?

 

[Hurkyl]

Well, before you decide you have a problem, you should make sure there's enough risk to warrant informing patients.

 

[Necrosis]

Well, before you decide you have a problem, you should make sure there's enough risk to warrant informing patients.

If you bought a new car, but that car had a 7% risk of catching on fire, wouldn't you want to know? The car company may determine it not enough risk to tell the customer, and when it does happen, they can pay whatever suing fee or possible medical and mechanical bills, but I would at least want to know that it could happen to my brand new car. And the CT scan is on our body, it's not like we can bring it in for a tune up and just flat out replace bad parts...maybe in the future when we have a cure for cancer we can just say, oh well and give the cure, but today where cancer is a huge threat to life when you get it, that's kind of the sort of thing I would like to know.

 

[Hurkyl]

If you bought a new car, but that car had a 7% risk of catching on fire, wouldn't you want to know?

Yes, I would.

Fortunately, you don't have a 7% risk of catching fire in a CT scan.

 

[Necrosis]

But you do have a 7% increase of chance in developing cancer later in life, and isn't that just like a fire in our cells(abstractly put)?

 

[Hurkyl]

But you do have a 7% increase of chance in developing cancer later in life

Where did you get this figure?

 

[Necrosis]

my bad, interposed percentage figures, I meant .08% which is from the original post. And for such a potentially dangerous illness, I find that signifigant.

 

[Hurkyl]

If it's an 0.08% increase, I see nothing to worry about. 0.08 percentage points, though is something different. I've been surfing trying to find the study that originated these figures to clarify.

 

[Necrosis]

That's cool, please do clarify when you find it. I guess this is just kind of a personal opinion thing though, I personally would want to know the risks, and I even think it might be kind of fun to bring up with friends right afterwords, but I would still want to know, especially if say, said person has a large chance of developing cancer anyways due to family history, and the .08% is what pushes him over the boundries and develops it earlier in life or develops it even though before he would not have. :shrug:

 

[Hurkyl]

Wow, I never realized cancer mortality rates were that high to begin with... (on the order of 30%, I think) haven't found for what I'm looking, but I'm becoming less inclined to believe that 0.08% is anything significant.

 

[Necrosis]

ehh, personal opinion like I said, I think at least. I would still like to know the risks no matter how small, even if it only caused diarreah(sp?)

 

[russ_watters]

Necrosis, you really need to keep this in perspective: you likely have a similar risk of dying in a car crash on the way to the doctor's office (lifetime odds ~.4%) than you do of dying (years later) as a result of the CT scan. If you're going to worry about every .08% chance of death (yes, please check that, Hurkyl, but I'll assume the worst for now...), you're going to end up rolled up in a fetal ball on the floor of your bathroom, afraid to take a shower for fear of slipping and falling and killing yourself (lifetime odds ~.02%).

I sincerely hope THIS doesn't keep you up tonight...

 

[Loren Booda]

How do effects of radiation exposure vary with skin pigmentation?

 

[Hurkyl]

Well, I think

http://radiology.rsnajnls.org/cgi/content/full/232/3/735

is a good place to start.


There seem to be two key assumptions: CT scan radiation is comparable to A-Bomb radiation, and that this graph:

http://radiology.rsnajnls.org/cgi/content-nw/full/232/3/735/F1

is supposed to be linear through zero.


I'd like to hear someone knowledgeable comment on the first assumption... I might take a crack at the second one; that graph doesn't seem to support the linear through zero.

 

[Necrosis]

Well, I don't know what problem you have with me, but let me make this perfectly clear for you and any other person who loves to interpret words as what they don't mean but could mean;

I would want to know the risk, even if it meant all that would happen is my hair would stand on end. I do know that driving has more chance of me dying in an accident than me dying through cancer from a CT scan, hell, more so for me because I race at the strip and am an aggressive driver whose blinkers don't currently work. I could choke on my SOUP tonight and die. I do not care about the death or how the death occurs, it is statistically proven that you WILL die. My problem is that only 7% of people that get a CT scan are informed of the risks when it may mean something more to a cancer survivor or a family member of a cancer victim or likewise. I PERSONALLY like to know the knowledge associated with damn near everything I can or that pertains to me, it's a tall drink, but I eventually want to order another one.

Why don't you look up and link what the lifetime expectency of a Marine while deployed in the field is, because I was in the Marines, and I was in the field and I went through that. My father was a S.E.A.L. and he had an even smaller lifetime expectency while in the field. I look at chances and odds because to ignore them is pre-mature death, but to disregard them is the same.

Edit: Removed unecessary comments.
Integral

 

[Necrosis]

There seem to be two key assumptions: CT scan radiation is comparable to A-Bomb radiation, and that this graph:

http://radiology.rsnajnls.org/cgi/content-nw/full/232/3/735/F1

is supposed to be linear through zero.


I'd like to hear someone knowledgeable comment on the first assumption... I might take a crack at the second one; that graph doesn't seem to support the linear through zero.

I agree, it looks like, to me, that it is capping off...as for the first assumption, I'm not sure I can give you a knowledgeable answer as I don't know that much about the bodies reaction to repeated doses of radiation as compared to one large dose of radiation.

 

[geometer]

my bad, interposed percentage figures, I meant .08% which is from the original post. And for such a potentially dangerous illness, I find that signifigant.

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%

 

[Necrosis]

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%

I never meant to state that it was an individual risk, and If I did, I am sorry, but 8 more people is still 8 more people. :Shrug:

 

[Tsu]

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

All of these things give off radiation. Oh. And NEVER permit yourself to have ANY medical x-rays or you will DIE in 50 years or so. Of course it will probably be less if you have to have mammograms - but obviously none of you are concerned with such issues. Guess none of you have wives...

 

[Necrosis]

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

All of these things give off radiation. Oh. And NEVER permit yourself to have ANY medical x-rays or you will DIE in 50 years or so. Of course it will probably be less if you have to have mammograms - but obviously none of you are concerned with such issues. Guess none of you have wives...

POSTED BY ME
Well, I don't know what problem you have with me, but let me make this perfectly clear for you and any other person who loves to interpret words as what they don't mean but could mean;

I would want to know the risk, even if it meant all that would happen is my hair would stand on end. I do know that driving has more chance of me dying in an accident than me dying through cancer from a CT scan, hell, more so for me because I race at the strip and am an aggressive driver whose blinkers don't currently work. I could choke on my SOUP tonight and die. I do not care about the death or how the death occurs, it is statistically proven that you WILL die. My problem is that only 7% of people that get a CT scan are informed of the risks when it may mean something more to a cancer survivor or a family member of a cancer victim or likewise. I PERSONALLY like to know the knowledge associated with damn near everything I can or that pertains to me, it's a tall drink, but I eventually want to order another one.

Why don't you look up and link what the lifetime expectency of a Marine while deployed in the field is, because I was in the Marines, and I was in the field and I went through that. My father was a S.E.A.L. and he had an even smaller lifetime expectency while in the field. I look at chances and odds because to ignore them is pre-mature death, but to disregard them is the same.

Appearantly you don't like to read everything...and yes I do have a wife.

 

[Necrosis]

Necrosis,

My gut reaction is honed by working at a job where, rightly, I must be sensitive to people suffering from medical conditions. Of course this is PF reality, so I will take the original comment with a grain of NaCl. I appreciate your going out of your way to explain its content.

I originally had associated "Necrosis" with "brain dead." I am a Unitarian - no doubt some Satanists in that crowd. Back to the Thread?

No problem.

Do you know something about repeated doses of radiation as compared to a single large dose? When the small doses eventually add up to almost the same (we'll call it the same for this question) amount as the large dose?

 

[Loren Booda]

I think that question had been touched upon earlier, but not answered definitively by our "experts."

The local radio station has a commercial that warns of household radiation danger. Apparently radon ("the second leading cause of lung cancer") builds up in basements in geographical regions where this particular decay product is generated. The choice may be between an energy "tight" house and a house safe from radiation.

 

[Tsu]

Appearantly you don't like to read everything...and yes I do have a wife.

No, I read it.
I'm glad you have a wife. We wives are nice to have around.

My point was, there is radiation everywhere. You said you wanted to know the risks of everything you do. I was merely trying help you avoid having to take those risks by pointing out a few things to avoid.

Radiation dose is cumulative. You are 'allowed' just so much in your lifetime and it's dependent upon your age. I'll have to brush up on my radiation protection terms and formulas (a few things have changed since I studied it ) but IIRC, the maximum permissable dose (MPD) is calculated by your age minus 18, then multiply by 5. This will give your MPD in RADs (radiation absorbed dose). I believe 1 RAD = 1 Roentgen = 1 rem (radiation equivalent man).

The body is a remarkable machine with amazing powers of regeneration. Did you know that every 7 years you have a brand new liver? We are continually making new cells and repairing damaged ones. The only parts of the body that don't regenerate are the eyes and reproductive organs. We take GREAT care to protect those.

There is no doubt that medical radiation is the source of most absorbed dose, and you should always discuss your concerns of risks with your physician before any scheduled medical exam. However, if you fall and break your hip, or get into a big car wreck, I doubt that the risks of radiation will be first and foremost in your mind.

Now, since the title of this thread is 'Danger in CT scans', I felt that it was important to point out that mammograms are higher dose exams than many CT scans. What I found interesting was that no one seems to want to comment on that. Are you not concerned about the massive dose your women are receiving on an annual basis? Possibly your women aren't old enough to worry about that yet, but it is certainly something that I am concerned about - and I work in the profession! Wouldn't that be enough to get your attention?

So, to those of you who may be doing research in the field or if you really want to help to make a difference - PLEASE FIND A WAY OF IMAGING THE BREASTS WITHOUT RADIATION! I have huge concerns that the very method we are using to detect breast cancer is also CAUSING some of those cancers. I don't have these concerns about CT scans as much because they are done in the 120KV range instead of the more damaging 20-30KV range. BUT - you DON'T want to go to one of those Body Imaging places in the local mall to have your annual screening CT scans. Most of the medical community are STRONGLY against those places. They are a source of needless radiation and the exams are generally useless.

 

[russ_watters]

...PLEASE FIND A WAY OF IMAGING THE BREASTS WITHOUT RADIATION!

Must...resist...sexual...inuendo.

Seriously though, Necrosis, you are taking this waaaay to personally. I'm no one - I'm not worth the effort to flame. If you disagree with something I said, say why you disagree or ignore me. Life's too short to get upset about it.

Regarding you desire to know the risk in everything, what we're trying to convey to you is two-fold:

1. There are risks everywhere and it is impossible to know what they all are all the time. To want to know every risk will lead to risk-reward analysis controlling your entire life.
2. Rest assured, when you go for that CT scan, someone (who knows more than you or me about the subject) has analyzed the risks and determined that it the benefit outweighs the risk of the scan.

 

[Integral]

2. Rest assured, when you go for that CT scan, someone (who knows more than you or me about the subject) has analyzed the risks and determined that it the benefit outweighs the risk of the scan.

Unfortunately, Russ, I am not so sure this is true. The Medical "professionals" must justify and pay for expensive equipment Tsu's comments reinforce my believe that profits come before long term patient safety in the US medical system.

Unfortunately my mother in law (whom I never had the chance to meet) and a very dear aunt of mine died of breast cancer way to young, both were faithful in their mammograms and Hormon Replacement. Both of which are questionable medical practices which may in the long run shorten the life of the patient while padding the wallet of the medical professionals.

Fortunately my wife was astute enough to make a connection and has not bought into the common concept of what is good for the doctors wallet is good for me.

 

[Loren Booda]

How effective are sonograms in breast imaging?

 

[imabug]

How effective are sonograms in breast imaging?

Ultrasound in breast imaging is good a characterizing soft tissue masses, but you can't see small calcifications that are characteristic of many types of breast cancer. Good specificity for some things, lacking in sensitivity.

Mammography on the other hand has very good sensitivity at detecting many things, but is not very specific. You can detect that something is there, but you can't always determine whether it is malignant or not.

Ultrasound is commonly used as an adjunct to mammography imaging, particularly to characterize soft tissue masses seen in mammograms. Ultrasound will never replace mammography because the resolution is too coarse.

 

[imabug]

You are 'allowed' just so much in your lifetime and it's dependent upon your age. I'll have to brush up on my radiation protection terms and formulas (a few things have changed since I studied it ) but IIRC, the maximum permissable dose (MPD) is calculated by your age minus 18, then multiply by 5. This will give your MPD in RADs (radiation absorbed dose).

this is only true from a regulatory stand point. MPD limits come from the NRC and FDA based on recommendations from bodies such as NCRP and ICRP. As such, they are always subject to change. And don't expect anyone to arrest or fine you for exceeding your MPD. Don't expect to suddenly keel over and die or contract some form of cancer either.

I believe 1 RAD = 1 Roentgen = 1 rem (radiation equivalent man).

applies at diagnostic energies only (<150 kVp) and only for x-ray/gamma radiation.

Now, since the title of this thread is 'Danger in CT scans', I felt that it was important to point out that mammograms are higher dose exams than many CT scans. What I found interesting was that no one seems to want to comment on that. Are you not concerned about the massive dose your women are receiving on an annual basis? Possibly your women aren't old enough to worry about that yet, but it is certainly something that I am concerned about - and I work in the profession! Wouldn't that be enough to get your attention?

In the USA, MQSA regulations limit the maximum mean glandular dose to 3 mSv (300 mrem) per exposure. The majority of mammography units typically achieve about half this value. Digital mammography units, once regulators get a feel for how they behave and stop treating them like film/screen mammo units, i believe will be able to provide acceptable mammograms at even less exposure.

 

[imabug]

I was recently reading pop sci and it revealed the following stats

For one full ct scan

• 1,300: Radiation dose in millirems

• 
  a typical average dose for a body CT.
  

  [*].08%: increase in risk of death from cancer

It is usually not very meaningful to talk about risk as a straight percentage without referring to the amount of dose. A typical value for increased cancer risk that I see is about 4%/sievert (Sv) or 0.04%/mrem. Very important to remember that this is for a population (as someone else pointed out earlier).

Also

• 3.75%: increase in risk of death from cancer if you have a full body CT scan annualy from age 25

• 
  why anyone would want to have an annual full body CT scan is beyond me. Totally unecessary radiation exposure and expense.
  

  [*] 300: Average annual radiation dose from natural sources a year in millirems

  normally quoted value. dose from natural background sources varies quite a bit with location and altitude. People living in Denver CO get quite a bit more than this, and they seem to be doing just fine.
  

  [*] $16 billion Estimated annual cost of unecessary diagonstic imagine

  I would question how they determine something is unnecessary
  

  [*]7%: Percentage of patients infromed of the risks of their CT scans

Sad, but not very surprising. Consent forms generally don't get too specific on radiation risks and many places use a single generic consent form to cover just about everything done in the hospital. And it's like fine print. Nobody ever reads it anyway.

That said, there's nothing keeping a patient from asking the technologist, radiologist or staff physicist about radiation risks. most (at least the ones I know anyway) are more than happy to do discuss it with the patient.

 

[imabug]

Unfortunately, Russ, I am not so sure this is true. The Medical "professionals" must justify and pay for expensive equipment Tsu's comments reinforce my believe that profits come before long term patient safety in the US medical system.

In many hospitals (the ones I've worked at anyway), requests for CT scans are generally protocolled before being scheduled. The request is filled out by the requesting physician with a description of the patient's history and signs/symptoms. This is then reviewed by the radiologist or resident or sometimes the lead technologist to determine if the type of scan requested is suitable, whether to order a contrast enhanced scan. If there are any questions with regard to suitability, the radiologist or resident generally calls the referring physician and discusses the case.

I haven't worked everywhere yet, so I can't say that this is how everyone works, but I think it's a fairly common procedure.

studies that are scheduled just to generate revenue to pay for a scanner usually don't make it past this point (I wouldn't even expect it to make it past the insurer). And if they do, that would definitely be fraud. if Medicare/Medicaid is involved as a payor and the gov't finds out it would also be grounds for a hospital/clinic to lose their Medicare/Medicaid provider status which no one is going to risk because of the money involved.

 

[Loren Booda]

Has anyone mentioned MRIs for mammography?

 

[Tsu]

Unfortunately, Russ, I am not so sure this is true. The Medical "professionals" must justify and pay for expensive equipment Tsu's comments reinforce my believe that profits come before long term patient safety in the US medical system.

Actually, Integral, I don't really think it is so much about the money-making aspects with CT (not nearly as much as with mammography - that has almost become an industry all by itself!). With CT, I believe it is more of a CYA kind of a thing. Doctors are almost FORCED to order every conceivable test in the book just to avoid being sued. Medical lawsuits have also almost become an industry all by themselves. Not to mention physicians who come out of med. school being completely unable to clinically diagnose their way out of a box! I actually had an ER physician look at an abdomen xray and, seeing a collection of gallstones in the gallbladder, he pointed them out and said to me "See? I knew he had KIDNEY stones!" When I told him they were gallstones, he said "Oh. Yeah. I guess if they were kidney stones they would be in a little line going down the ureter." (ON WHAT PLANET WOULD THAT BE, DOCTOR?) I had to leave the ER at that point or I would have screamed to all of the patients "GO HOME! THIS DOCTOR DOESN'T KNOW WHAT HE'S DOING!" It's unbelievably frustrating to be stuck in these kinds of situations all of the time. I have been SO less than impressed with what medical schools are turning out these days. Whoops. I digress AGAIN... But you guys really got me where I LIVE with this thread...

Imabug! Thanks for jumping in here! As a medical physicist, you are in a position to help push my agenda for non-radiation breast imaging. Wanna help? Are you a radiation physicist? Do you know Tim Kasson?

 

[Tsu]

Has anyone mentioned MRIs for mammography?

Yes, I mentioned in an earlier post that I think MR is the way of the future for breast imaging. We are doing MR on breasts now, but usually only AFTER a mammogram and/or ultrasound has been done. MR is extremely sensitive to soft tissue differences and yields extremely diagnostic images. IIRC, they've been able to detect breast cancers where mammograms have not. They are not currently used as a screening tool, however, because of the time and cost factors.

Oh, Imabug...! That's where YOU come in...! Can you build me a MR Breast Imager that can perform breast exams in 15 minutes and is as (or MORE! ) cost effective as mammography? Pretty please? :shy:

 

[Tsu]

Must...resist...sexual...inuendo.

Pervert.

 

[imabug]

Imabug! Thanks for jumping in here! As a medical physicist, you are in a position to help push my agenda for non-radiation breast imaging. Wanna help?

anyone who comes up with an imaging method that's as sensitive as x-ray mammography, specific as MRI, cheap and fast will probably have it made. very challenging task.

there are several breast imaging techniques out there that use non-ionizing radiation. MRI and ultrasound are two. optical imaging is another one, but I don't really see it going very far. electrical impedance tomography is another one. I've even heard of some people trying to develop microwave imaging. I don't see any of these being anything more than adjuncts to x-ray mammography though.

x-ray mammography is currently the gold standard in breast imaging because it has excellent low contrast and resolution (15-20 line pairs/mm or < 0.03 mm), fast and easy to do so you can screen a lot of people and relatively cheap. beat those and you'll have a winner.

Are you a radiation physicist? Do you know Tim Kasson?

I'm a diagnostic medical physicst specializing in diagnostic x-ray and nuclear medicine. I'm afraid I don't know Tim Kasson.