[ RadSafe ] bakscatter x-ray

[Cary Renquist]

I took a quick look at one of the papers that they cite for dose per
scan data... The paper was by some researchers at John Hopkins U. 

(Been a long time since I have played with x-rays and I have never dealt
with 50 kVp x-rays)
Their list of equipment for dose measurement was a large ion chamber
(1800 cm^3 volume) and a Thermo Sci. (Bicron) micro-rem survey meter.
Neither of those seem especially appropriate for rigorously
characterizing the dose from such a low energy x-ray source.
Particularly where the concern might be entrance dose.

As I indicated above, I took a really quick look -- haven't read the
experimental protocol/analysis or any of the other papers that are
available.  
They can be downloaded from the TSA site: TSA Electronic reading room
http://j.mp/92qzyT

Probably a good read for my flight back home for Thanksgiving...
(perhaps I should grab some heavy metal carrier solution from the lab
(bismuth?/barium?) and paint a smiley face on my skin)

Best regards,
Cary

---
Cary Renquist
cary.renquist at ezag.com


-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu
[mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Brennan, Mike
(DOH)
Sent: Tuesday, 16 November 2010 08:53
To: radsafe at health.phys.iit.edu
Subject: Re: [ RadSafe ] bakscatter x-ray

X-ray isn't my corner of the rad world, but the more I think about the "
The majority of their energy is delivered to the skin and the underlying
tissue. Thus, while the dose would be safe if it were distributed
throughout the volume of the entire body, the dose to the skin may be
dangerously high." Statement, the less sense it makes to me.  It seems
to me that for any x-ray the majority of the absorption is in first
dense material it encounters; the skin.  It also seems to me that if one
set up detectors to collect and process the backscatter from a
diagnostic x-ray procedure, you could image the target's skin through
their clothing (though this would be far more difficult than just asking
them to take it off).  Unless someone can point out where I am wrong
(and I well might be), it seems that this objection is without merit.   

-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu
[mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Brennan, Mike
(DOH)
Sent: Monday, November 15, 2010 4:05 PM
To: radsafe at health.phys.iit.edu
Subject: Re: [ RadSafe ] bakscatter xray

If the majority of the energy is delivered to the skin, then wouldn't it
follow that the majority of THAT energy is delivered to the outer layer
or the skin; the layer of dead skin cells?  If the claim is that the
radiation penetrates the dead layer, but is then deposited in the living
tissue, I would think that there should be some support for that.  


-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu
[mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of conrad sherman
Sent: Sunday, November 14, 2010 6:57 PM
To: radsafe at health.phys.iit.edu
Subject: [ RadSafe ] bakscatter xray

here is the letter from ucsf and response

LETTER OF CONCERN

...Snip.....

(28keV).The majority of their energy is delivered to the skin and the 
Underlying tissue. Thus, while the dose would be safe if it were
distributed 
throughout the volume of the entire body, the dose to the skin may be 
dangerously high.

....Snip....
_______________________________________________