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RE: Different colors of dose
Hi All,
I think that it is time that we again look at the question of meaningful
digits in a calculated or measured number! If we were all dedicated to
giving those numbers as the stochastic numbers they are, we would realize
that the errors do not allow you to give too many digits for a dose.
From the attached post re-read and wonder how they do it:
" participating in this study, you will receive a total of 6293.7 mrad to
your Bone Surfaces, 4795.2 mrad to your Urinary Bladder Wall and 919.079
mrad to your Red Marrow. Although each organ will receive a different dose,
the amount of radiation exposure that you will receive from these procedures
is equivalent to a whole body exposure of 693 days (1.898 years) of exposure
to natural background radiation. "
Here I cannot but cite the famous German mathematician Carl Friedrich Gauss:
"Nichts beweist wissenschaftliche Ignoranz besser als uebertriebene
Genauigkeit im Zahlenrechnen!"
"Nothing proves scientific ignorance more conclusively that excessive
precision in
numerical calculations!"
Well have a nice weekend anyway :-)
Fritz
*****************************************************
Fritz A. Seiler, Ph.D.
Sigma Five Consulting: Private:
P.O. Box 1709 P.O. Box 437
Los Lunas, NM 87031 Tome', NM 87060
Tel.: 505-866-5193 Tel. 505-866-6976
Fax: 505-866-5197 USA
*****************************************************
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"This is the hour when democracy must justify
itself by capacity for effective decision, or risk
destruction or desintegration. Europe is dotted
with the ruins of right decisions taken too late."
"America's Responsibility in the Current Crisis"
Manifesto of the Christian Realists. May, 1940.
******************************************************
-----Original Message-----
From: owner-radsafe@list.vanderbilt.edu
[mailto:owner-radsafe@list.vanderbilt.edu]On Behalf Of Shackford, Hobart
W
Sent: Friday, April 02, 2004 7:18 AM
To: Donna O'Kelly; Radsafe@list.vanderbilt.edu
Subject: RE: Different colors of dose
Donna:
I think that perhaps the Nuclear Medicine tech needs a dose refresher
in-service. If you check the Radar dosimetry site at
http://www.doseinfo-radar.com/RADARDoseRiskCalc.html
you will get the following statement to plug into a human research
disclosure form for the 27 mCi bone scan:
"This research study involves exposure to radiation from a Tc-99m Medronate
also known as Tc-99m Methyenediphosponate (MDP), . This radiation exposure
is not necessary for your medical care and is for research purposes only.
Using the standard way of describing radiation dose, from participating in
this study, you will receive a total of 6293.7 mrad to your Bone Surfaces,
4795.2 mrad to your Urinary Bladder Wall and 919.079 mrad to your Red
Marrow. Although each organ will receive a different dose, the amount of
radiation exposure that you will receive from these procedures is equivalent
to a whole body exposure of 693 days (1.898 years) of exposure to natural
background radiation. This use involves minimal risk and is necessary to
obtain the research information desired."
The calculated total effective dose was 569 mrem (5.69 mSv).
As was stated in a previous posting, the risks of radiation harm are far
outweighed by the benefits but I do not think that it is proper to provide
such a gross understatement of the dose to the patient. your posting is
prompting me to check out what our techs are telling their patients.
I hope you have been following the postings concerning outpatient I-131
therapy treatments. With a 225 mCi load I am sure you are aware of how
significant a source you will be. That dosage is just below our upper limit
for outpatient treatment without specific patient uptake/excretion
measurements and would only be given to patients that we are reasonable sure
would abide with isolation restrictions for the first two days after
administration (to give a 0.125 occupancy factor in the NRC NUREG-1556 App U
equation).
Best of luck with your therapy.
Hobie Shackford, RSO
Roger Williams Hospital
Providence, RI
401-456-2471
hshackford@rwmc.org
-----Original Message-----
From: owner-radsafe@list.vanderbilt.edu
[mailto:owner-radsafe@list.vanderbilt.edu]On Behalf Of Donna O'Kelly
Sent: Thursday, April 01, 2004 11:26 PM
To: Radsafe@list.vanderbilt.edu
Subject: Different colors of dose
I have been a member of this list for almost two years now and never felt
the need to post until now. In the last six months, I have been diagnosed
with two primary cancers, kidney and thyroid. Luckily - both were caught
early, so I expect to be around for a long while.
My issue originates from my going to get a bone scan (27 mCi Tc-99m-MDP)
and the rad tech telling me I'm not getting any more dose than if I stayed
out in the sun for an hour. How do you even begin to counter that? (A
Landauer OSL on my hip over 3 days gave a dose of 67 mrem). Secondly, is
the fact that this 27 mCi is completely "safe" for me for medical purposes,
but if I wee to encounter this same isotope and activity at my facility, it
would be regulated and *I* would become a radiation area and visitors
wouldn't be allowed near it. But since I got it from a medical facility,
it was okay. I dunno is the 140 keV gamma from safer if it is given to me
in a medical facility??? I think not. There's so much hypocrisy to the
whole thing in my mind.
What about from CTs of the head, neck, abdomen and pelvis? Again, no harm
since it's a medical issue - but I encounter it at work...and it's just a
horrible thing.
I won't even go into the 225 mCi I-131 I'm getting ready to ingest..
I think this is a discrepancy that should be pointed out and addressed with
folks across the board. I've certainly incorporated this information into
the tours that I give at my facility.
Thoughts anyone?
Donna J. O'Kelly, Ph.D
Laboratory Manager
Reactor Health Physicist
Nuclear Engineering Teaching Laboratory
The University of Texas at Austin
J.J. Pickle Research Campus
10100 Burnet Road, Building 159
Austin, TX 78758
office: (512) 232-4174
fax: (512) 471-4589
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