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Radiation Dose with CT Scan-Mayo Clinic

hi my name is aimy Hara and I'm an

associate professor of radiology at the

Mayo Clinic in Arizona and what I want

to talk to you today is about radiation

dose with CT scans now a CT scan is a

common procedure that we do every day

there's about 65 million of these

examinations performed every year in the

United States so this is a test where

you lay on your back on a table usually

have an IV and insert it into your arm

that gives you contrast during the

procedure and you hold your breath while

the table is slid through a doughnut

sized hole opening and pictures are

taken anywhere from head to toe so we do

this examination to look for a lot of

different tests like stroke

diverticulitis appendicitis renal stones

bowel obstruction cancer until look at

cancer spread so as a lot of different

uses recently in the publicity and media

there's been a lot of attention

concerning radiation dose with CT so

there have been headlines such as CT

scans can cause cancer that I believe

caused a lot of widespread fear in the

public and it's important to separate

fact from fiction when we talk about

this argument so a lot of the media

publicity came after an article that was

published in a prestigious medical

journal that said that was a theoretical

increased risk of cancer from CT scans

and it's important to know that this

article was based on a theoretical risk

so there's actually never been a patient

who's had a CT scan that then got cancer

because of that CT scan or any studies

have really shown that CT scans cause

cancer but that this article was based

on risk associated with radiation

exposure that was based on atomic bomb

survivor data so a lot of people in the

medical community really believe that

the fundamental basis of this article

was flawed because the radiation

exposure blast that you get from an

atomic bomb is obviously very different

from small radiation exposures that you

get from imaging over several years so a

colleague was talking about this with

another patient the other day and said

it's similar to a few walking across the

carpet and you get those little electric

shocks versus sticking your finger in an

electric socket you know those are two

very different things and that's similar

to the analogy that they're kind of

making in this paper that one is similar

to the other but in any event I think

that the paper raised important

choose that one CT scans are being done

more and more commonly today and there

is a small but real risk of the

radiation exposure with CT scans so I'm

going to talk a little bit about the

numbers because I think it helps to put

in perspective exposure from CT scans

versus other types of exposure that we

see every day so just from walking

around in the environment every day we

are all exposed to background levels of

normal radiation and that number in a

year is usually about 3.5 million

seabirds so in comparison a head CT is

about 1.8 million verts so it's less

than what you get from a year of walking

around just in your back yard on the

other hand a CT scan of your abdomen is

higher it can be eight to ten

millisieverts which is higher than what

you normally get from walking around but

it's actually the same background level

of radiation that somebody living in

Denver gets on a yearly basis so the

higher the altitude the higher levels of

normal background radiation that we all

have there are other types of radiation

exposure that people get every year that

are similar so airline pilots also

people at high altitudes frequent fliers

are exposed to more background radiation

as well and that can be five

millisieverts per year people that work

in nuclear plants as well are exposed to

exposure similar to an abdomen CT there

have been a lot of studies that have

looked actually at airline pilots people

that worked in nuclear plants and have

shown that those folks don't have any

higher risk of cancer than anybody else

in the general population so I think we

have real data to show that small levels

of radiation from one or two CT scans of

your lifetime doesn't have any increased

risk of cancer so when should you be

concerned well there's two groups of

patients that were really concerned with

for radiation exposure and one is

children we know that radiation exposure

and what happens with the radiation

occurs on a cellular level and so if you

get an imaging test you're not going to

see the effects of radiation today or

tomorrow it's something if it manifests

itself won't happen for ten or twenty

years down the road so that's why we're

really concerned about children because

they have a whole lifetime ahead of them

and we don't want any of those radiation

risks or changes to happen over their

lifetime now on the other hand if you

have a 70 year old patient that's

getting a CT scan you're very unlikely

to see any effect of that

radiation exposure during that patients

lifetime so those are two very different

groups of people that you need to be

concerned about so we're always

concerned with children and we're also

concerned with younger people that get

tests early in their lifetime if they

have a chronic disease and then get a

lot of scans over their lifetime as well

so what can you do to reduce and

minimize your dose if you have a child

you always want to ask your physician

unless you're in an emergent situation

can that clinical question be answered

with a test that doesn't require

radiation like MRIs or ultrasounds

sometimes you still need to do a CT scan

and in those instances you want to be

able to go to a facility that has a

newer type of CT scanner that allows you

to do lower radiation dose examinations

so we have one of those newer scanners

at Mayo Clinic Arizona that allows us to

scan patients at 50% lower dose than

some of the older scanners and actually

as time goes on if the all the CT

scanners will convert to a lower dose

type of technique but only certain

facilities have those scanners currently

now if you're a younger patient for

example someone with Crohn's disease

they're often diagnosed at a young age

and then get a lot of imaging over their

lifetime and in those patients we now

recommend they switch over and get their

questions answered with em our rather

than CT to save some of that exposure to

radiation so to try to put this all into

summary again the CT scans can be a

life-saving procedure and it really

shouldn't you should not refuse the CT

scan because of a fear of radiation

exposure if you're in one of those

emergent situations such as you need to

rule out a stroke or bleeding on the

inside of your body after a car accident

you really need to get that CT scan if

you have a child or a younger patient

that gets a lot of scans over their

lifetime you want to ask your physician

about changing to Mrs or ultrasounds or

low-dose CT scans so thank you very much