[ RadSafe ] Myth or Fact? (Dental dose)

Fri Aug 25 14:44:54 CDT 2006

Jim,
This is not unusual.  You could certainly have a chest
CT performed using a spiral CT scanner, but the is not
the "typical" standard of care.  Now facilities are
using multidetector CT (MDCT) scanners.  Faster. 
Better images. More costs.

Check your medical insurance rates.

--- "Muckerheide, Jim  (CDA)"
<Jim.Muckerheide at state.ma.us> wrote:

> Ahh..  Another ICRP et al. success, requiring the
> purchase of more and
> more (and ever more costly) machines.  This is
> ICRP's mission since it
> was formed by the radiologists in 1928, when UK
> machine-makers were
> complaining that the UK radiologists were buying
> lower cost German
> machines.
> 
> Regards, Jim 
> 
> 
> > -----Original Message-----
> > From: radsafe-bounces at radlab.nl 
> > [mailto:radsafe-bounces at radlab.nl] On Behalf Of
> Robert Atkinson
> > Sent: Friday, August 25, 2006 5:11 AM
> > To: yhayaka at tdc.ac.jp; radsafe at radlab.nl
> > Subject: RE: [ RadSafe ] Myth or Fact? (Dental
> dose)
> > 
> > 
> > Hi,
> > In the UK the use of 50kV inter-oral X-Ray sets
> was phased out from
> > about 1990 with a ban from 2001 (some special
> exceptions), along with
> > other measures to reduce the dose. These include
> adjustable 
> > output and a
> > minimum focus to skin distance of 200mm.
> > 
> > See <
> >
>
http://www.hpa.org.uk/radiation/publications/documents_of_nrpb
> > /abstracts
> > /absd5-3.htm >
> > 
> > Regards,
> > Robert Atkinson.
> > 
> > -----Original Message-----
> > From: radsafe-bounces at radlab.nl
> [mailto:radsafe-bounces at radlab.nl] On
> > Behalf Of Yoshihiko Hayakawa
> > Sent: 25 August 2006 09:30
> > To: radsafe at radlab.nl
> > Subject: Re: [ RadSafe ] Myth or Fact? (Dental
> dose)
> > 
> > Dear RADSAFE subscribers,
> > 
> > I think that the entrance skin dose of 4.71 mGy is
> slightly high.
> > 
> > There are at least three recent survey reports as
> follows;
> > UK survey: Napier, I.D. Reference doses for dental
> radiography.
> >      British Dental Journal, 1999; 186: 392-396.
> > US survey: Suleiman, O.H. et al. Radiographic
> trends of dental
> >      offices and dental schools.
> >      Journal of American Dental Association, 1999;
> 130: 1104-1110.
> > Spain survey: Gonzalez, L, et al. Reference doses
> in dental
> >      radiodiagnostic facilities.
> >      The British Journal of Radiology, 2001; 74:
> 153-156.
> > 
> > UK and US survey reports are cited by the
> UNSCEAR2000 Report.
> > 
> > UK survey: The average entrance dose was 3.3 mGy,
> which included
> >    the data at lower kV sets (45-55 kV). The
> average obtained at
> >    kV sets commonly used (60-70 kV) was 2.2 mGy.
> The report
> >    included much higher doses which I can not
> believe. The highest
> >    at 60-70 kV sets was 20.5 mGy...
> >    (Many years ago a professor in Sweden told me
> that the operation
> >     at less than 60 kV is illegal in Sweden.)
> > US survey: Mean entrance air kerma values ranged
> approx. between
> >    1 mGy and 2 mGy. Sometimes X-ray equipments
> were operated at
> >    higher kV settings in the United States.
> > Spain survey: The mean value of skin doses was
> 2.89 mGy.
> > 
> > If measurements are carried out at my school now,
> average entrance
> > doses distribute approx. between 1 mGy and 2 mGy
> at 60-70 kV
> > settings.
> > 
> > - - - - - -
> > The record of dental doses in the 20th century was
> described by
> > S.C. White, UCLA, in 1992 as follows;
> > White SC. 1992 assessment of radiation risk from
> dental
> > radiography.
> > Dentomaxillofacial Radiology, 1992 Aug;
> 21(3):118-26.
> > 
> > Based on White's report, I can describe, "Doses
> with a single
> > dental exposure (bitewing/intraoral radiography)
> are equivalent
> > to between approx. 7 hours and 1 day background
> exposure.
> > 
> > - - - - - -
> > A reasonable estimate in my opinion of the
> effective dose from
> > a single dental (bitewing/intraoral) radiography
> ranges between
> > 1 to 5 microSv (0.1 to 0.5 mrem). Another estimate
> in my opinion
> > of the effective dose from the full mouth survey
> ranges between
> > 10 to 50 microSv (1 to 5 mrem).
> > 
> > I agree the statement that in Europe a skilled
> dentist (or his
> > technician) with state-of-the-art equipment will
> expose you to
> > about 0.01 mSv effective dose per examination. But
> in a recent
> > decade some sophisticated equipments have become
> world-wide
> > available.
> > 
> > Now it can be said in my opinion, "Every year, the
> average
> > globe citizen is exposed to natural radiation
> equal to about
> > 720-3,600 dental X-rays."
> > 
> > Sincerely.
> >    Yoshihiko Hayakawa
> >    Tokyo Dental College
> >     mailto:yhayaka at tdc.ac.jp
> > 
> > Peter Thomas wrote:
> > 
> > > New Zealand's NRL produced a report 15 years ago
> based on TLD
> > > measurements in a RANDO phantom to get the ratio
> of organ 
> > doses to the
> > > entrance skin dose for a couple of dental exams.
>  The 
> > following is for
> > a
> > > single bitewing film at 60kV based on an
> entrance skin dose of 4.71
> > mGy
> > > (471 mrad).  It's an old report but I'd expect
> similar results under
> > > today's conditions given the same entrance skin
> dose.
> > > 
> > > Entrance skin  4.71 mGy
> > > Ovaries 0.0000047 mGy
> > > Testes 0.00044 mGy
> > > Bone (in head/neck) 0.019 mGy
> > > Breast 0.00196 mGy
> > > Lungs 0.00106 mGy
> > > Thyroid 0.0215 mGy
> > > Brain 0.0094 mGy
> > > Sinuses 0.426 mGy
> > > Salivary Glands 0.275 mGy
> > > Pharynx 0.327 mGy
> > > Larynx 0.048 mGy
> > > Liver 0.00011 mGy
> > > Stomach 0.000052 mGy
> > > Kidneys 0.000033 mGy
> > > Small Intestine 0.000014 mGy
> > > Eyeballs 0.021 mGy
> > > 
> > > The main contributors to the effective dose are
> the dose to the
> > thyroid
> > > and the dose to the salivary glands (0.025
> weighting factor under
> > ICRP60
> > > rules where a remainder tissue has a higher does
> than any of the
> > tissues
> > > with individual weighting factors).  The skin
> dose drops by a factor
> > of
> > > 600 due to the ratio of the irradiated area to
> that of the 
> 
=== message truncated ===

+++++++++++++++++++
>From an article about physicians doing clinical studies: 

"It was just before an early morning meeting, and I was really trying to get to the bagels, but I couldn't help overhearing a conversation between one of my statistical colleagues and a surgeon.

Statistician: "Oh, so you have already calculated the P value?"

Surgeon: "Yes, I used multinomial logistic regression."

Statistician: "Really? How did you come up with that?"

Surgeon: "Well, I tried each analysis on the SPSS drop-down menus, and that was the one that gave the smallest P value"."

-- John
John Jacobus, MS
Certified Health Physicist
e-mail:  crispy_bird at yahoo.com

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