Re: Re: CT-Scan Radiation

[Guest guest]

Dear all,

Here is a very informative post revealing the statistics involved in some of the

scans we are talking about. it's good to read and comes from at CLL

Research: K.

[Do you, or even your doctor, know how much radiation you get when

you have an abdominal CT scan? Did you know just one scan is the

equivalent of 400 chest X-rays?

I think I'm going to run this post from September 2004 every year or

so...]

From the archives of (2 papers):

BMJ 2003;327:371-372 (16 August)

Doctors' knowledge of radiation exposure:

questionnaire study

S Shiralkar, consultant surgeon1, A Rennie, senior

house officer in

general surgery2, M Snow, senior house officer in

general surgery3, R

B Galland, consultant surgeon2, M H , consultant

surgeon3, K

Gower-, consultant radiologist3

1 s Hall Hospital, Dudley, West Midlands DY1

2HQ, 2 Royal

Berkshire Hospital, Reading RG1 5AN, 3 Royal Glamorgan

Hospital,

Llantrisant CF72 8XR

Despite the small but definite risk to patients'

health,

investigations involving radiation are an accepted and

fundamental

part of medical practice. In the United Kingdom an

estimated 100-250

deaths occur each year from cancers directly related

to medical

exposure to radiation.1 In March 2000, the UK

secretary of state

issued new regulations that emphasised the importance

and dangers of

radiation.2 3

We investigated the level of knowledge doctors have

concerning

radiation doses received by patients when they undergo

commonly

requested radiological investigations.

We compiled a questionnaire listing the most commonly

requested

radiological investigations. Participants were asked

to identify the

average dose of radiation received when a person

underwent a standard

chest x ray. This was then used to represent a single

dose of

radiation, and doctors were asked to estimate the

equivalent doses of

radiation for various radiological investigations

(table).

Table 1

Equivalent number of doses of radiation for most

commonly requested

investigations. Dose for chest x ray used as single

unit dose of

radiation. Figures are numbers (percentage) of doctors

with correct

answer for each investigation

Radiological Equivalent No of No of correct % of

correct

investigation of chest x-rays answers answers (n=130)

Abdominal x ray 75 3 1.5

Lumbar spine x ray 120 3 2

Thoracic spine x ray 50 4 3

Barium swallow 100 6 5

Peroperative

cholangiogram 65 3 2

Fixation of fractured

neck of femur 45 10 8

Ultrasound of abdomen 0 124 95

CT of abdomen 400 8 6

Spiral CT of abdomen 300 9 7

MRI of abdomen 0 119 92

MRI of knee 0 119 92

MRI of spine 0 119 92

Leg arteriogram 400 0 0

Renal arteriogram 80 1 1

Thyroid isotope scan 50 8 6

White cell scan 150 2 1.5

CT=computed tomography; MRI=magnetic resonance

imaging.

Equivalent number of doses of radiation for most

commonly requested

investigations. Dose for chest x ray used as single

unit dose of

radiation. Figures are numbers and percentages of

doctors with correct

answer for each investigation

We asked a convenience sample of 130 doctors at all

different grades

from two separate hospitals (South Wales and Oxford)

to take part in

the study and interviewed each doctor on a one to one

basis. All

doctors agreed to complete the questionnaire. There

was no negative

marking. We accepted a deviation of 20% above and

below the correct

value (wider variations were allowed for those

procedures for which

the radiation dose can vary enormously). Correct

answers to the

questions were derived from information available on

the internet4 and

counter checked with the Royal College of

Radiologists.5

We interviewed 40 senior house officers, 40 specialist

registrars, 40

consultants, and 10 consultant radiologists. None of

them knew the

approximate dose of radiation received by a patient

during a chest x

ray or even the measurement in units of radiation

(0.02 mSv). The

minimum score was 0% and the maximum score was 59%.

Five doctors (4%)

gave no correct answers. The estimated doses of

radiation were much

lower than the correct doses. For example, a patient

undergoing an

arteriogram of the leg would receive 400 times the

radiation of a

chest x ray, but the average mean answer was 26

times—that is, doctors

were submitting their patients to a radiation dose

that was 16 times

larger than they thought it was. The average mean dose

of irradiation

was six times the quantity estimated by the doctor.

Overall, 97% of the answers were underestimates of the

actual dose;

six (5%) doctors did not realise that ultrasound does

not use ionising

radiation; and 11 (8%) did not realise that magnetic

resonance imaging

does not use ionising radiation.

In a convenience sample of doctors few had any

knowledge about the

level of radiation that their patients were exposed to

during

radiological investigations. Most patients entering

hospital will have

at least one x ray investigation and usually many more

subsequent x

rays. It is well known to both the lay public and to

medical

professionals that although radiological

investigations are valuable,

they represent a small but definite potential risk to

health through

exposure to ionising radiation.

The interviewed doctors came from two hospitals in two

different

regions. Therefore our results may not apply

throughout the United

Kingdom, but it does seem that most doctors have no

idea as to the

amount of radiation received by patients undergoing

commonly requested

investigations, despite them all having undertaken the

radiation

protection course. This lack of awareness of the

degree of exposure to

ionising radiation becomes particularly pertinent when

we consider the

number of patients who receive inappropriate or repeat

examinations.

1. Royal College of Radiologists and National

Radiological

Protection Board. Patient dose reduction in diagnostic

radiology.

Documents of the National Radiological Protection

Board 1990;1:No 3.

2. The Ionising Radiation (Medical Exposure)

Regulations 2000.

www.doh.gov.uk/irmer.htm (accessed 14 Oct 2002).

3. Statutory instrument 2000 number 1059. The Ionising

Radiation

(Medical Exposure) Regulations 2000.

www.legislation.hmso.gov.uk/si/si2000/20001059.htm

(accessed 14 Oct 2002).

4. Health Physics Society.

www.hps.org/publicinformation/asktheexperts.cfm

(accessed 12 Nov 2001).

5. Royal College of Radiologists. Making the best use

of department

of clinical radiology: guidelines for doctors. 4th ed.

London: Royal

College of Radiologists, 1998.

http://bmj.com/cgi/content/full/327/7411/371?etoc

And:

Reuters Health

By Will Boggs, MD

Wednesday, May 5, 2004

NEW YORK (Reuters Health) - How much radiation do you

get from a CT

scan? It's substantially higher than most patients,

and even their

doctors, realize, according to a new report.

The radiation dose from one abdominal CT scan has been

estimated to

be equivalent to 100 to 250 chest X-rays, the authors

explain in the

May issue of Radiology. One controversial study has

attributed 2,500

deaths annually to CT examinations in the United

States.

Dr. P. Forman and colleagues from Yale

University in New

Haven, Connecticut, surveyed patients, emergency

department (ED)

physicians, and radiologists to determine the

awareness level

concerning radiation dose and possible risks

associated with CT

scans.

Only 5 of 76 patients (7 percent) reported being

informed of the

risks and benefits before their CT scan, the authors

report, and only

10 of 45 ED physicians (22 percent) reported

explaining those risks

and benefits to their patients.

Nearly half the radiologists (47 percent) believed

that a CT scan

increased the lifetime risk of cancer, the results

indicate, but a

similar belief was reported by only 3 percent of

patients and 9

percent of ED physicians.

Ninety-two percent of patients estimated the radiation

dose of one CT

scan to be no more than 10 chest X-rays, the

researchers note, as did

51 percent of ED physicians and 61 percent of

radiologists.

Only 22 percent of ED physicians and 13 percent of

radiologists (and

none of the patients) had dose estimates in the

accurate range.

" Given the current debate about the possible increased

cancer risk

associated with diagnostic CT scans, " the

investigators write, " we

believe that it is important that the radiology

community make

current information regarding CT radiation dose more

widely

available. "

Physicians are not adequately prepared to answer

questions their

patients should be asking about the risks and benefits

of imaging

studies, Forman told Reuters Health. " We must empower

our patients to

ask questions, and our physicians ... must become

better prepared to

answer these important questions. "

" Not all imaging is necessary and unnecessary imaging,

with its

attendant risk, is bad medicine, " Forman concluded.

" On the other

hand, I would not want to frighten patients from

having necessary

studies performed; they should be informed, though. "

SOURCE Radiology, May 2004.

-------------- Original message --------------

From: Carolyn Swift <swift_carolyn@...>

Thanks, Kurt, for your caution to me about CT-Scans. I

will raise the question with my onc. Also thanks for

the compliment on how I take care of myself; I hope

you're correct! Carolyn, age 77, dx 9/04,w & w