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          X-RAY DOSE-MEASURING SERVICE FOR PHYSICIANS AND DENTISTS
                              January 21, 2001

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         *  The entrance dose of x-rays is the dose received at the
     body's surface, where the x-ray beam enters. The exit dose, which
     is what results in an image, is very much lower. The body absorbs
     the difference between the entrance and exit doses.

         *  TLDs (ThermoLuminescent Dosimeters) can measure the x-ray
     entrance dose received by any patient during an x-ray imaging
     procedure. TLDs are small, nearly flat crystals (about the
     diameter of a pencil eraser), sometimes with a self-adhesive back.

         *  On the patient's skin, in the field where the x-ray beam
     will hit, the x-ray technician just tapes the TLD. The TLD does
     not interfere with the image. After the x-ray procedure, the
     irradiated TLDs are sent to a "reading" machine which reveals the
     entrance dose.

         *  X-ray practitioners can obtain the TLDs, the instructions,
     and the reading service by mail from an accredited laboratory at
     the University of Wisconsin:

            Radiation Monitoring by Mail
            Univ. of Wisconsin Radiation Calibration Lab
            1530 Medical Sciences Center
            1300 University Avenue
            Madison WI 53706-1532.
            Tel: 608-262-6320, Dr. Larry Dewerd, or Keith A. Kunugi.
            E-mail: kakunugi@facstaff.wisc.edu

         *  TLDs are inexpensive (probably less than $3 each), but they
     are useless without a laboratory's services (instructing,
     shipping, reading, record-keeping, supplying and reading the
     control-TLD which measures the radiation exposure accumulated from
     natural sources by each batch of TLDs before and after the x-ray
     exposure). These services cost more than the TLDs themselves.
     There are probably reduced fees for volume.

         *  For FLUOROSCOPY machines, "real-time" (immediate)
     dose-measuring equipment has been available for decades, and is
     highly recommended, because of the high doses delivered by an
     x-ray beam which stays "on" continuously for many seconds, even
     for many minutes. Such equipment tells the fluoroscopist the x-ray
     dose already accumulated by the patient's surface from fluoroscopy
     at any instant during a procedure.


     X-rays and Health 
     Committee for Nuclear Responsibility, Inc.
     January 2001

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