Radiographic dose and risks

[Douglas Benn]

I did not explain that this information was provided to the dental
health public list server in response to a request I received.

Douglas


Dr. Douglas K. Benn,
Professor & Director of Oral Diagnostic Systems,
Dept. Oral and Maxillofacial Surgery & Diagnostic Sciences,
University of Florida College of Dentistry,
Box 100414,
Gainesville, FL 32610-0414,
USA.

Tel: (352) 392 5210.
Fax: (352) 392 2507
Email: benn at dental.ufl.edu
See website: http://oralsurgery.dental.ufl.edu for our presentation
 "How to heal tooth decay and avoid fillings"

Personal website: http://www.dental.ufl.edu/benncv.htm

>>> TSCHIFF at SFMAIL.DENTAL.UOP.EDU 11/03/00 12:41PM >>>
Thanks for this great information. Are you now teaching in your school
not to use lead aprons?? ( I hope not )
Thomas.

>>> Douglas Benn <BENN at DENTAL.UFL.EDU> 11/03 9:08 AM >>>
As a follow-up to the inquiry about the need for protective patient
lead aprons, a  little additional information:

The risk of fatal cancer from a dental radiographic examination is:

                   D* speed film     E* speed       E with rectangular
collimator
One pa  1: 1.5 million        1:3 million       1:6 million
4 BWs      1: 375,000          1: 750,000    1: 1.5 million
FMX **  1:    90,000          1: 180,000    1: 400,000

PAN     1: 500,000

* assumes round collimators  ** 20 films

The average individual person whole body  dose equivalent annual
exposure of natural background radiation (including medical/dental
exams)  is 3.6 milli sieverts (Sv) per year.

Dental radiographic examinations can be expressed in terms of days of
background radiation:

Exam                    Dose  micro Sv          Days equivalent
background radiation
                                                                D
speed
               E speed
Full mouth      150             11                            5.5
4BWs                      38                    4.8
     2.4
1 PA                             9                          1.2
               6 hours

Pan                          26         1.9

The new Kodak F speed film needs 20% less radiation than E speed film.

The dose is primarily from the main beam, not from scattered x-ray
photons. The risk from the primary beam is already very low compared
to
other daily activities and using a lead apron does not significantly
reduc these risks. However, changing from D speed film with a round
collimator  to E speed film with a rectangular collimator will reduce
the primary main beam dose by  four times - far more important than
the
use of a lead apron.


Comparative risks of 1: 100,000 of death

1 milli Sv of radiation (approx 3 months of background radiation)
Travelling approx 500 miles by air or car
15 minutes of rock climbing
Smoking 10 cigarettes.

During pregnancy a woman who:

Receives 10 milli Sv of radiation to womb (approx 3 years of whole
body
background radiation) has a 1:3,300 of the baby dying from cancer
during
childhood.
Smokes 1 pack or more a day has a 1:3 chance infant death
Alcohol 2-4 drinks per day Fetal alcohol syndrome 1:10 or 2.75% risk
of
major malformation at delivery.

The extra dose above background to a dental worker is approx
equivalent
to 3 weeks of natural background radiation per year.

Source of data  In: White & Pharoah. Oral Radiology (4th Edn) , Mosby
2000.

I hope this information is useful.

Douglas Benn

ps I am editor-elect of  Dentomaxillofacial Radiology, the journal of
the International Association of Dentomaxillofacial Radiology.

Dr. Douglas K. Benn,
Professor & Director of Oral Diagnostic Systems,
Dept. Oral and Maxillofacial Surgery & Diagnostic Sciences,
University of Florida College of Dentistry,
Box 100414,
Gainesville, FL 32610-0414,
USA.

Tel: (352) 392 5210.
Fax: (352) 392 2507
Email: benn at dental.ufl.edu
See website: http://oralsurgery.dental.ufl.edu for our presentation
 "How to heal tooth decay and avoid fillings"

Personal website: http://www.dental.ufl.edu/benncv.htm