Danger in CT scans [Archive]

Tom McCurdy

Oct24-04, 07:17 PM

ZapperZ

Oct24-04, 07:38 PM

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

Oct24-04, 08:18 PM

ZapperZ

Oct24-04, 08:23 PM

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

Oct24-04, 09:09 PM

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

russ_watters

Oct25-04, 11:15 AM

Well, my first and overwhelming reaction is "So what?" Me too. The reason, as already stated, these stats are utterly devoid of context.

geometer

Oct25-04, 11:32 AM

Tom McCurdy

Oct25-04, 02:35 PM

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

Oct25-04, 02:36 PM

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

Oct25-04, 04:03 PM

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

Oct25-04, 06:22 PM

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

Oct25-04, 07:07 PM

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

Oct25-04, 08:38 PM

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 recieve an equivalent does
radiation does in mrem from smoking pack of cegarettes
increase in risk of death from cancer

Let's see. Google finds

duke CAT dose calculator (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

Epa rad effects (http://www.epa.gov/radiation/understand/health_effects.htm)

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

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 :frown:. 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

Oct25-04, 11:17 PM

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

Oct26-04, 02:44 PM

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!! :rofl: :rofl: That was GREAT!! I'm picturing us trying to compress a stack of MEMO's with the mammogram machine... :rofl: :rofl: :rofl: Sorry. I digress... :biggrin: ) 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 definately 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. :eek: See ya!

Necrosis

Oct26-04, 06:47 PM

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

Oct26-04, 06:58 PM

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

Necrosis

Oct26-04, 07:06 PM

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 jsut 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

Oct26-04, 07:10 PM

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

Oct26-04, 07:12 PM

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

Oct26-04, 07:16 PM

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

Where did you get this figure?

Necrosis

Oct26-04, 07:19 PM

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

Oct26-04, 07:24 PM

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

Oct26-04, 07:32 PM

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

Oct26-04, 07:38 PM

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

Oct26-04, 07:41 PM

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

Oct26-04, 07:42 PM

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 (http://www.nsc.org/lrs/statinfo/odds.htm) doesn't keep you up tonight...

Loren Booda

Oct26-04, 07:56 PM

How do effects of radiation exposure vary with skin pigmentation?

Hurkyl

Oct26-04, 08:00 PM

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 knowledgable 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

Oct26-04, 08:01 PM

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

Oct26-04, 08:09 PM

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 knowledgable 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 knowledgable 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

Oct26-04, 08:28 PM

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

Oct26-04, 08:47 PM

Tsu

Oct26-04, 11:59 PM

Necrosis

Oct27-04, 10:35 AM

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. :rolleyes: 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

Oct27-04, 10:37 AM

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

Oct27-04, 11:56 AM

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

Oct27-04, 01:37 PM

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. :smile:

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. :surprised :rofl: :rofl:

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 :surprised ) 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). :surprised

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

Oct27-04, 04:07 PM

...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

Oct27-04, 04:38 PM

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

Oct27-04, 04:55 PM

How effective are sonograms in breast imaging?

imabug

Oct27-04, 06:22 PM

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

Oct27-04, 06:31 PM

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 :surprised ) 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

Oct27-04, 06:53 PM

[SIZE=4][SIZE=3][FONT=Verdana]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

Oct27-04, 07:06 PM

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

Oct27-04, 11:33 PM

Has anyone mentioned MRIs for mammography?

Tsu

Oct27-04, 11:51 PM

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... :biggrin: But you guys really got me where I LIVE with this thread... :wink:

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

Tsu

Oct28-04, 04:53 AM

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. :grumpy:

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! :biggrin:) cost effective as mammography? :biggrin: Pretty please? :shy:

Tsu

Oct28-04, 04:56 AM

Must....resist....sexual...inuendo.
:rofl: :rofl: :rofl: :rofl:
Pervert. :biggrin:

imabug

Oct28-04, 12:45 PM

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.

Tsu

Oct28-04, 03:15 PM

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.
DR/CR is, no doubt, the future of radiology. But even so, aren't we still dealing with the extremely low KV ranges? 20-30? Can you convince me that those 'soft' rays are not CAUSING the very cancers we are trying to detect?

(Hey, guys! Sorry I hijacked this thread. :redface: We'll get back to CT in a minute. OK? I tried to start a thread about mammography about a year ago, but no one would touch it. This is a subject that has been eating at me for 20 years and it IS (somewhat :redface:) relative to the topic...)

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.

Are you up for it? :biggrin:

More to the point, how can this get pushed to the forefront in R&D? I've written to most of the major producers of mammography equipment trying to nudge them along, but... :rolleyes:

BACK TO CT!!

I'm really questioning that 1,300mr dose for an average CT scan. I thought it was about half that. In fact... Yeah! Pervect showed that on page one. I'll try to check my scanner tonight and get a few dose readouts.

Here's the interesting thing about CT dose. (Imabug, correct me if things have changed!) If you have a chest CT, you'll receive a dose of 500mr along the length of the chest scan. (NOW think about a dose of 300mr to each BREAST in an annual screening mammogram!! :surprised - sorry - had to throw that in... :biggrin: ) If you have a chest AND abdomen CT at the same time, you'll still receive a dose of... 500mr!!! - but it's along the length of the chest and the abdomen. They aren't added together to get a dose of 1000mr. However, it is still cumulative. Two chest CT's in one week will yield a dose of 1000mr.

imabug

Oct28-04, 03:44 PM

DR/CR is, no doubt, the future of radiology. But even so, aren't we still dealing with the extremely low KV ranges? 20-30? Can you convince me that those 'soft' rays are not CAUSING the very cancers we are trying to detect?
I ran across a paper a while back discussing the cancer induction risks associated with screening mammography. As I recall, they were relatively low (not insignificant though). However, I think the benefits of finding a cancer early via screening mammograms vastly outweighs the slight increase in risk of developing a cancer years later because of screening mammography. it will probably take some time to dig it up, but I'll see if I can find a reference.

BACK TO CT!!

I'm really questioning that 1,300mr dose for an average CT scan. I thought it was about half that. In fact... Yeah! Pervect showed that on page one. I'll try to check my scanner tonight and get a few dose readouts.

CT doses vary significantly from machine to machine, but anywhere from 10-30 mGy (1-3 rad) is probably typical. Body CT doses can range anywhere from 3-4 rad for older single slice machines to less than 1 rad for newer machines with automatic technique adjustments (these have software that adjust the x-ray technique throughout the scan to compensate for changing body thickness). A lot of places are starting to modify their CT protocols to lower patient dose, particularly for pediatric studies.

Here's the interesting thing about CT dose. (Imabug, correct me if things have changed!) If you have a chest CT, you'll receive a dose of 500mr along the length of the chest scan. (NOW think about a dose of 300mr to each BREAST in an annual screening mammogram!! :surprised - sorry - had to throw that in... :biggrin: ) If you have a chest AND abdomen CT at the same time, you'll still receive a dose of... 500mr!!! - but it's along the length of the chest and the abdomen. They aren't added together to get a dose of 1000mr. However, it is still cumulative. Two chest CT's in one week will yield a dose of 1000mr.

yes, this is correct, but only if the slices don't overlap. doses quoted for CT scans are typically dose/slice, but having a 40 slice CT scan doesn't mean you get 40 times the dose.

Not very intuitive, but obvious if you know what dose represents.

Dose (in rad/Gray) is a unit of absorbed energy measured in J/kg. The dose from 1 CT slice might be 1.3 rad. The dose from 2 CT slices is still 1.3 rad. You've deposited twice the energy (2 slices vs 1 slice), but at the same time the total mass you've irradiated has doubled. The factors of 2 cancel out.

However, if you irradiate the same volume of tissue twice, you've deposited twice the energy, but the total mass of tissue you've irradiated stays the same. Therefore dose adds up.

Math Is Hard

Oct28-04, 06:14 PM

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.
I am glad you weighed in on this thread, Tsu. Your comments have really made me think. I can't even imagine how difficult it would be to do a study on the correlation of mammograms and incidence of breast cancer. Women who are getting annual (or more frequent) mammograms are going to be in a group that has a greater risk for the disease, so choosing groups for a study would be very problematic, I'd think.
Interesting that you mentioned those "Body Imaging" places. I hear them advertised on the radio frequently and I was very curious as to what traditional radiologists had to say about them.

imabug

Oct28-04, 06:55 PM

Interesting that you mentioned those "Body Imaging" places. I hear them advertised on the radio frequently and I was very curious as to what traditional radiologists had to say about them.

FDA's page on whole body CT screening (http://www.fda.gov/cdrh/ct/)
American College of Radiology's position on CT screening (http://www.acr.org/s_acr/doc.asp?CID=2192&DID=16014)

The American College of Radiology (ACR) recognizes that an increasing number of computed tomography (CT) screening examinations are being performed in the United States. Much CT screening is targeted at specific diseases, such as lung scanning for cancer in current and former smokers, coronary artery calcium scoring as a predictor of cardiac events and CT colonography (virtual colonoscopy) for colon cancer. Early data suggest that these targeted examinations may be clinically valid. Large, prospective, multicenter trials are currently under way or in the planning phase to evaluate whether these screening exams reduce the rate of mortality.

The ACR, at this time, does not believe there is sufficient evidence to justify recommending total body CT screening for patients with no symptoms or a family history suggesting disease. To date, there is no evidence that total body CT screening is cost efficient or effective in prolonging life. In addition, the ACR is concerned that this procedure will lead to the discovery of numerous findings that will not ultimately affect patients' health but will result in unnecessary follow-up examinations and treatments and significant wasted expense.

The ACR will continue to monitor scientific studies concerning these procedures.

Math Is Hard

Oct28-04, 07:02 PM

Thank you, imabug.

In addition, the ACR is concerned that this procedure will lead to the discovery of numerous findings that will not ultimately affect patients' health but will result in unnecessary follow-up examinations and treatments and significant wasted expense.

Sounds like the advice is: Don't borrow trouble.

russ_watters

Oct28-04, 08:37 PM

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. Well, like Tsunami said, I think that's more about money and CYA than risk/reward. But I was talking as much about the science that went into designing these machines and the approvals that had to be gotten before they could ever use them. Its not just the doctor ordering the test that you are putting your trust in. But still, doctors are human, so there are times when doing your own homework is a good idea. But a standard test done in a standard way doesn't ring my warning bell (and trust me - I'm a very distrustful person).

Even I have a story about a doctor who wasn't motivated by a patients' best interest: My grandfather at an aneurism of the aorta about 15 years ago. Standard treatment at the time was to crack the chest and wrap some dacron around it. A surgeon in Allentown (where it was diagnosed) wanted to perform the surgery. He'd done 5 - 3 successful. This wasn't good enough for my mom, who started asking questions and researching and found that the best place to have this done was in Dallas, by a surgeon who had done hundreds. So that's where they went and my grandfather is still active today at 88.

I know some doctors are pushing yearly full-body scans for profit, but AFAIK, few reputable doctors' groups/medical journals say thats a good idea (though probably at least as much because of the unnecessary expense). We may yet get to the point where your yearly physical includes some type of full-body scan, but we're not there yet. A Star Trek style tricorder that can non-invasively diagnose anything would be the holy grail of diagnostic tools.

Loren Booda

Oct28-04, 11:44 PM

In graduate school we were once asked to determine a lower limit for proton decay halflife by considering the effect of such radiation on ova production!

imabug

Oct29-04, 01:35 PM

In graduate school we were once asked to determine a lower limit for proton decay halflife by considering the effect of such radiation on ova production!
interesting, although I'm not quite seeing the connection. how did you go about solving the problem?

Tsu

Oct29-04, 11:39 PM

Loren Booda

Oct29-04, 11:40 PM

imabug,

I'm sorry. If it does have a legitimate answer, I have long since forgotten it.

Tsu

Oct30-04, 12:11 AM

imabug,

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

Loren Booda

Oct30-04, 02:24 AM

Tsu,

I'm even enrolled in obedience school, taught by my girlfriend's 14 year-old Cocker, Dyna.

Tsu

Oct30-04, 02:55 AM

Good boy!!! :biggrin:

pervect

Oct30-04, 08:33 PM

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.

pervect

Oct31-04, 01:03 AM

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).

imabug

Oct31-04, 07:38 AM

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 gonna 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.

Tsu

Oct31-04, 09:35 AM

<groan> oh, god!... I hate conversions...

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.

imabug

Oct31-04, 12:27 PM

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.