Re: Effective Photon Energy of X-rays -Reply

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

>X-Sender: dsimpkin@mail.execpc.com
>Date:         Thu, 30 Jul 1998 17:47:28 -0500
>Reply-To:     Medical Physics Mailing List <MEDPHYS@LISTS.WAYNE.EDU>
>Sender:       Medical Physics Listserver <medphys@cwis-20.wayne.edu>
>From:         Douglas Simpkin <dsimpkin@EXECPC.COM>
>Subject:      Re: Effective Photon Energy of X-rays -Reply
>To:           MEDPHYS@LISTS.WAYNE.EDU
>
>re: this message (and the flippant responses it generated):
>>  I want to apply correction factor of effective photon energy to doses
>measured by a BeO TLD dosimetry.As you know I should estimate an effective
>photon energy for 150 kVp x-rays. any information regarding computation of
>effective energy for X-rays are appreciated.
>>thanks in advance.
>
>This is a tremendously complicated question. There is no one recipe to
>compress a broad bremsstrahlung energy spectrum down to single "effective
>energy." It depends on what "effect" you're after! (Rarely will the "mean"
>energy be that effective energy.)
>
>For this particular BeO TLD problem, I suggest the questioner consult the
>basic literature (or someone with TLD calibration experience). In my copy
>of Attix, Intro to Radiological Physics and Radiation Dosimetry, 1986, p.
>407 he states "...the same TL reading will result from a given average
>phosphor dose in a TLD, regardless of the spatial distribution of absorbed
>dose within it... The practical consequence of this is that a Co-60 gamma
>ray calibration in terms of average phosphor dose in the TLD can then be
>used as an approximate calibration for all low-LET radiations, including
>x-rays... even if they deposit dose nonuniformly in the dosimeter." Attix
>then shows the response for LiF to be flat above 100 keV, with a broadly
>~30% overresponse in the 10-80 keV range.
>
>Herb then gives (p. 411) a number of standard references that will describe
>the details of the photon energy response of BeO. See McKinlay
>"Thermoluminescence Dosimetry" 1981, Adam Hilger, Bristol, UK.
>
>Douglas J. Simpkin, Ph.D.
>Certified Radiation Physicist
>St. Luke's Medical Center
>2900 West Oklahoma Avenue
>Milwaukee, WI 53215
>(414)649-6457
>fax:(414)649-5061
>email: dsimpkin@execpc.com
>
>                    *****
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>
Chris Alston
alstonc@odrge.odr.georgetown.edu
I am not here a representative of my employer.

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