[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Seed dosimetry quiz results
>Date: Wed, 3 Jun 1998 17:58:40 -0400
>Reply-To: oncology@hgo.net
>Sender: Medical Physics Listserver <medphys@lists.wayne.edu>
>From: Wayne Butler <oncology@HGO.NET>
>Organization: Wheeling Hospital
>Subject: Seed dosimetry quiz results
>To: MEDPHYS@LISTS.WAYNE.EDU
>
>There were only 9 responses to the quiz, but the results were
>heartening. All 7 of the TG-43 users were within 0.2% of their mean.
>
>1. Calculate the total dose at 1 and 2cm from a 1mCi Amersham 6711
>I-125 seed.
>
> @ 1cm: 2137Gy +- 3cGy (7 answers), 2651cGy, 1.41cGy (This submitter
>probably calculated rate in cGy/h. If so, total dose = 2900cGy)
>
> @ 2cm: 445cGy +- 1cGy (7 answers), 556cGy, 0.31cGy (per hour? =
>638cGy total dose)
>
> Sample hand calc using TG-43 point source, I-125 @ 2cm: D = Sk *
>Lambda * Anis * g(2) * Tmean
>
> D = (1mCi*1.27U/mCi) * 0.88cGy/hr*U * 0.93 * 0.832 *
>(59.4d*24hr/d/ln(2)) = 445cGy
>
>2. Calculate total dose at 1 and 2cm for a 1mCi Theragenics 200 Pd-103
>seed.
>
> @ 1cm: 506cGy +- 1cGy (7 answers), 562cGy
>
> @ 2cm: 73cGy (7 answers), 82cGy
>
>3. Which calculation formalism do you use?
>
> 7 use point source TG-43 (one uses Memorial as double check), 1
>Memorial, 1 uncertain, but home grown.
>
>4. Could your docs writing prostate brachytherapy prescriptions answer
>#3 satisfactorily?
>
> 8 yes, 1 no
>
>5. Would it be clear to an outsider reading the prescription which
>calculation protocol was intended?
>
> 5 yes, 4 no Two of the yesses mentioned that they document charts
>in great detail, using either dictated transcripts or preprinted
>stickers, the changes invoked by switching to TG-43.
>
>Thanks to all who participated.
>
>Wayne
>
>
>--
>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>Wayne Butler, Ph.D.
>Schiffler Oncology Center
>Wheeling Hospital Phone: 304-243-3983
>One Medical Park Fax: 304-243-5047
>Wheeling, WV 26003 E-mail: oncology@hgo.net
>
>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> *****
>Frequently Asked Questions (FAQ) for Medphys at:
>http://www.mindspring.com/~sherouse/MPFAQ/
>