FOR IMMEDIATE RELEASE:        NIST 96-05
Feb. 20, 1996

Linda Joy                     NEW NIST FACILITY WILL IMPROVE
(301) 975-4403                ACCURACY OF RADIATION
linda.joy@nist.gov            MEASUREMENTS IN MAMMOGRAPHY


     Women undergoing mammography exams at accredited U.S. facilities
soon will have much improved assurance of receiving proper X-ray
exposures thanks to a new radiation standard and instrument calibration
facility at the Commerce Department's National Institute of Standards
and Technology in Gaithersburg, Md.

     This new NIST facility will allow the operators and inspectors of
more than 10,000 U.S. mammography centers to trace the accuracy of their
X-ray exposure measurements to the primary mammography X-ray standards
at NIST. "One of the critical parameters in mammographic procedures is
the X-ray exposure to the breast," explains Michelle Johnson, a
physicist in NIST's Ionizing Radiation Division. "The radiation exposure
to the breast should be kept to a minimum while ensuring adequate
diagnostic quality in the recorded image."

     Johnson, along with colleagues Paul Lamperti, Julian Sparrow and
Manfred Osti, developed the new calibration facility, which makes NIST
only the second national standards laboratory in the world to provide
primary standards for mammography.

     The calibration facility was established to assist the U.S. Food
and Drug Administration implement the Mammography Quality Standards Act
of 1992. This law requires the FDA to set up a certification and
inspection program for all U.S. mammography clinics. The instruments
used by the FDA inspectors to measure the X-ray exposure from the
clinical units will be calibrated using standards traceable to the new
NIST reference X-ray beams.

     For many decades NIST has maintained national standards for medical
diagnostic X-ray beams generated by tungsten-anode machines. NIST now
can meet important needs in measurement quality that are specific to
mammography units, nearly all of which generate X-ray beams from
molybdenum or rhodium anodes, with added filtration to improve the beam
characteristics. These dedicated mammography X-ray units produce a
higher image quality with a lower radiation dose to the breast. The new
reference X-ray beams available at NIST include anode and filter
combinations of molybdenum and rhodium, and cover the range of beam
qualities used in mammography clinics.

     The primary standard that defines and measures the reference X-ray
beams will be used to establish the calibration factor for each
radiation measuring instrument sent to NIST for calibration in this new
specialized facility. Anyone wanting to calibrate an X-ray exposure
measuring instrument for mammography beams may send the instrument to
NIST. Typical users of this service are expected to be secondary
calibration laboratories, inspectors of mammography units and instrument
manufacturers. The new facility will begin performing calibrations in
early 1996.

     For further information on the new facility, contact Michelle
Johnson, C229 Radiation Physics Building, NIST, Gaithersburg, Md.
20899-0001, (301) 975-2014.

     A non-regulatory agency of the Commerce Department's Technology
Administration, NIST promotes U.S. economic growth by working with
industry to develop and apply technology, measurements and standards.

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