[ RadSafe ] x-ray tube fade

Richardson David (RDE) Essex Rivers David.Richardson at essexrivers.nhs.uk
Mon Oct 16 09:02:32 CDT 2006

I concurr,

for exposures of this size, I would expect to wait between 3 and 5 minutes between exposures. If you check the operators manual, it should tell you the time to wait between exposures.

Speaking personally, given the fall off you are noting, I would not be too concerned.

Best regards 

David Richardson 
MTO Radiation Protection 
Essex County Hospital 
Lexden Road 
CO3 3NB 
01206 744579 
01206 744101 (fax) 
mailto:david.richardson at essexrivers.nhs.uk 

-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl]On
Behalf Of John Jacobus
Sent: 14 October 2006 20:31
To: cehn at aol.com; radsafe at radlab.nl
Subject: Re: [ RadSafe ] x-ray tube fade

What was the interval between each exposure? X-ray
tubes have a rated heat capacity.  The tube needs to
cool down in order to provide the same output.  Also,
your exposure times of 2.5 seconds is very long which
may also be a problem. Dental x-ray tubes are not
designed to heavy workloads which is what you may
subjecting it to. 

--- cehn at aol.com wrote:

> Doing QC checks with a dental x-ray unit & RadCal,
> I'm seeing fading of the dose with successive
> exposures.  Did 10; the first 2 were about the same
> dose (~40 mrem; 77 kVp, 12 mA; 2.5 sec).  Next 8
> dropped by about 0.1% each time. Final exposure was
> about 1% less than the first. Steady drop.  But kVp
> measurements held steady.  Is this normal, or does
> it indicate a problem?  Thanks in advance.
> Joel Cehn
> joelc at alum.wpi.edu

May we never confuse honest dissent with disloyal subversion. 
Dwight D. Eisenhower  

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

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