Re: AW: Effective Photon Energy of X-rays

[Chris Alston <alstonc@odrge.odr.georgetown.edu>]

>From: "Robert G. Zamenhof" <zamenhof@MIT.EDU>
>Subject:      Re: AW: Effective Photon Energy of X-rays

>This discussion about estimating the single keV equivalence of a specific
>kVp spectrum is interesting.  Many older texts (e.g., Meredith & Massey and
>TerPergossian) give a crude rule-of-thumb of 1/3 the kVp--independent of
>HVL.  I looked at this some time ago to check whether such a rule-of-thumb
>would be correct to teach to the residents.  My conclusion was that for W
>targets only, at typical HVLs of 2.5-3.5 mm Al, kVp/2.2 was a more accurate
>estimate FOR 20 CM TRANSPORT THROUGH H2O.  Different body "filters" will
>affect this estimate.  Using this rule, one can explain to residents why
>70-75 kVp x-rays are close tooptimal for angiography and why Ce would be a
>preferable contrast element for CT applications.
>
>Yours, definitely off a cholestrerol-free diet, from beautiful Leukerbad, CH,
>
>Robert
>
>                    *****
>Frequently Asked Questions (FAQ) for Medphys at:
>http://www.mindspring.com/~sherouse/MPFAQ/
>
>Archives of recent Medphys postings at:
>http://www.escribe.com/medicine/medphys/
>
Chris Alston
alstonc@odrge.odr.georgetown.edu
I am not here a representative of my employer.

************************************************************************
The RADSAFE Frequently Asked Questions list, archives and subscription
information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html