[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
RE: Equine radiology
Hi
Actually, it is 20 mA. Most equine portable units are underpowered as
compared to general diagnostic x-ray units. The average output is 20 mA, 80
kVp, and time being the variable. Some machines may say they vary the mA
(10- 15 -20), but usually if you use 10 mA you get 90 kVp, 15 mA @ 80, and
20 mA at 70 kVp. Again, Time being the only variable.
If using an average 400 speed film/screen combination, the time averaged
about .15 to .2 seconds for a P3 (hoof and distal foot x-ray at 30 inches)
up to .25 to .3 seconds for a carpal study. The machines are single phase,
half wave and 30 inches is used as SID to compensate for the half wave. The
machines are designed to be positioned on a stand to the operator can stand
away from the box and the horse. They are lightweight and most meet the 100
mR scatter limit due to small amounts of lead wrapped around the miniature
x-ray tube. The person holding the cassette should be using some type of
mechanical holder and not his hands to hold the cassette to position himself
away from the primary beam.
I cannot find the actual scatter and leakage figures I did when I was at a
Veterinary Teaching Hospital, but the student holders and myself received
minimal readings on our badges for the years I was there doing this time of
work. Other examinations gave us a reading but for equine work with this
machine, there shouldn't be any reading.
On the other hand, in the field, I have seen veterinarians holding the x-ray
machine (a box about 9 inches square) directly on their pelvis to steady it
and not using a stand. There the dosimeter on their collar might not read
anything, but the gonadal area is receiving about 1-2 mRem per exposure from
tube leakage. They sometimes had the owner of the animal holding the
cassette and from some of the radiographs I've seen, they were directly in
the primary beam. Usually the owner had no apron, gloves, or dosimeter to
measure a dose.
Questions? contact me.
Richard Kay, MSc, RT(R)(M), MSRP, FASRT
Imaging Resources, Inc.
richard@imaging-resources.com
-----Original Message-----
From: owner-radsafe@list.vanderbilt.edu
[mailto:owner-radsafe@list.vanderbilt.edu]On Behalf Of
garyi@trinityphysics.com
Sent: Tuesday, April 06, 2004 12:20 PM
To: radsafe@list.vanderbilt.edu; Stabin, Michael
Subject: Re: Equine radiology
Eyeball estimate from NCRP 54 Fig 4 is 6 mR/mAs at 90 kVp 40". It
seems likley that your suplicant meant mAs instead of mA, so using 20
mAs gives 120 mrem entrance dose per image. Using the rough
approximation of 0.1% scatter at 1 meter, the handlers will get about
0.2 mrem per image, of course dependent on how close they are.
So, ~ 100 to 160 mrem to the horse and ~ 0.1 to 0.4 mrem for the
handlers.
-Gary Isenhower
Subject: Equine radiology
Date sent: Tue, 6 Apr 2004 11:44:48 -0500
From: "Stabin, Michael"
<michael.g.stabin@vanderbilt.edu>
To: <radsafe@list.vanderbilt.edu>
Send reply to: "Stabin, Michael"
<michael.g.stabin@vanderbilt.edu>
Anyone with some equine radiology experience out there? Got this
request this morning:
"Please tell me approximately how many mrem the equine patient and
horse handler are exposed to during a standard limb
(hoof)radiographic
procedure using a portable x-ray machine (70-90 kVp and 10-30
mA)?"
Hey, with a question like this, "who ya gonna call?" Radsafe, of
course, Dosebusters Extraodinaire.
Mike
Michael G. Stabin, PhD, CHP
Assistant Professor of Radiology and Radiological Sciences
Department of Radiology and Radiological Sciences
Vanderbilt University
1161 21st Avenue South
Nashville, TN 37232-2675
Phone (615) 343-0068
Fax (615) 322-3764
Pager (615) 835-5153
e-mail michael.g.stabin@vanderbilt.edu
internet www.doseinfo-radar.com
**********************************************************************
** You are currently subscribed to the Radsafe mailing list. To
unsubscribe, send an e-mail to Majordomo@list.vanderbilt.edu Put
the
text "unsubscribe radsafe" (no quote marks) in the body of the e-mail,
with no subject line. You can view the Radsafe archives at
http://www.vanderbilt.edu/radsafe/
************************************************************************
You are currently subscribed to the Radsafe mailing list. To
unsubscribe, send an e-mail to Majordomo@list.vanderbilt.edu Put the
text "unsubscribe radsafe" (no quote marks) in the body of the e-mail,
with no subject line. You can view the Radsafe archives at
http://www.vanderbilt.edu/radsafe/