Re: Doctors' knowledge of radiation exposure

[John Jacobus <crispy_bird@YAHOO.COM>]

Peter,

I think you may be correct in your assessment of how

much the "correct" dose plays into this issue. 

Whether a chest AP is 0.02 or 0.04 or 0.10 mSv is

really a question of which set of data you use.  The

real issue is that physicians and technologist really

understand the procedures and resulting relative

exposures received.  Your example of exposures during

a leg arteriograms is a classic example of the

problem.  



I have included technologist, because I am sure a quiz

of x-ray technologists would provide similar

disheartening results.  And they are usually the ones

the patients ask.  That is why I think it is useful to

post a list of exposures for the standard procedures

performed on each x-ray unit based on measurements

made on that machine.  It may not be patient specific,

but it is sure better that being caught flat-footed by

a patient.



I would add that I have always considered the exposure

values as guidelines, and not absolute values, e.g.,

"a chest x-ray is about 0.04 mSv."  As soon as you say

it is exactly such and such, your start moving from

stochastic to detetministic responses.  Medicine does

not deal in absolutes, and neither are the adverse

effects of such exposures.  It would be interesting to

survey patients about their chances of getting cancer

or heart disease.  



By the way, how well do you think the physicians at

your facility do on this kind of survey?





--- Peter.Thomas@health.gov.au wrote:

> Dan & Radsafe,

> 

> While agreeing that it is lamentable that only about

> 5% of the 130 

> respondents

> in the survey could produce the "correct" answer I

> feel that 

> interpretation of

> this survey is a little problematic.

> 

> The thing that struck me most was the fact that 6

> out or 130 appeared to 

> think

> ultrasound involved ionising radiation and 11 out of

> 130 appeared to 

> believe

> the same for MRI.

> 

> It's also unclear whether an equivalent answer was

> accepted for the base

> question regarding a "chest x-ray".  That is, 0.02

> mSv was deemed to be 

> correct,

> but was 2 mrem also accepted ?

> 

> The HPS "Ask the expert" pages have the very list in

> a question asked by

> the lead author of this little note, Sandy

> Shiralkar. (Q813)  The HPS 

> expert response is that

> a chest PA is 0.04 mSv and a chest LAT is 0.1 mSv. 

> The UK data such as

> Hart and Wall BRJ 70, 437-439 (1997) and NRPB-W4

> (2002) say 0.02 mSv for

> a chest PA and 0.04 mSv for a chest LAT.  There is,

> however a factor of 5 

> difference

> between the 5th and 95th percentiles.

> 

> Taking chest=0.02mSv and applying the list of

> "correct" answers one gets

> 1.5 mSv for an abdomen (AP?) whereas Hart and Wall

> say 0.7 mSv, with a 

> range

> from 0.25 to 1.6.  "Lumbar spine x-ray" becomes 2.4

> mSv, the HPS expert

> response gives a total for 5 films, Hart and Wall

> list values for AP, LAT 

> and

> a LAT of the lumbo-sacral junction, totalling 1.3

> mSv and this highlights 

> another

> issue of what one means when referring to

> such-and-such "x-ray".

> 

> Much also depends on how much one knows of the

> details of a procedure,

> admittedly a very important thing for a requesting

> physician but perhaps

> less so for others.  Leg arteriograms are a case in

> point in my opinion, I

> remember my and my colleagues profound shock when we

> realised that

> this was a multi-mSv procedure (4 mSv or 200 chest

> x-rays according to

> Thwaites et al Phys Med Biol 41 899-907 {1996})

> having only had a mental

> picture of knee and leg x-rays from our

> understanding of the purpose of

> the exam in a particular case.

> 

> I think a "Price is Right" (showing my

> demographic!!) type of ranked list

> might have been more appropriate or something giving

> order of

> magnitude groupings (tens, hundreds, etc of chest

> x-rays)

> 

. . .



=====

-- John

John Jacobus, MS

Certified Health Physicist

e-mail:  crispy_bird@yahoo.com



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