UNIVERSITY OF WISCONSIN RADIATION CALIBRATION LABORATORY

1111 Highland Avenue, B1002 WIMR Building, Madison, Wisconsin 53705 Phone: (608) 262-6320 Fax: (608) 262-5012

Report of Radio-Opaque Fabric Measurement Project

I. Introduction

At the request of Jeff Buske of Rocky Flats Gear, measurements were performed on October 20, 2010 to determine the x-ray exposure attenuation of three radio-opaque fabric samples.

II. Irradiation Methodology

The instruments used in this investigation included the following: UWRCL Exradin A3 (s/n XR022483) reference ion chamber, SI model Max 4000 (s/n E001225) standard electrometer, Mensor digital pressure gauge (s/n 531059), and Omega temperature probe (s/n T-226542).

A. The irradiation procedure for determination of the reference exposure rate and attenuation of the supplied fabric samples was as follows:

1. Position the UWRCL standard reference chamber at an anode source to detector distance (SDD) of 100cm in a 10cm x 10cm field in the UWRCL Advanced X-ray constant potential x-ray source standard calibration geometry.

2. Take a series of charge readings to determine the exposure rate at this location and geometry using the assigned NIST air kerma (and exposure) calibration coefficient for the reference ion chamber on the UW120-M x-ray beam.

3. Place the supplied sample at a location of 50cm SDD in the beam, to fully attenuate the beam midway between the x-ray tube anode and the reference ion chamber.

4. Take a series of charge readings to determine the exposure rate of the attenuated beam with the fabric sample in place.

5. Calculate the exposure rate of the attenuated beam, and divide by the exposure rate of the unattenuated beam from step 2.

6. Tabulate the results to include the unattenuated beam exposure rate, the fabric-attenuated exposure rate, and the ratio of attenuated exposure to unattenuated exposure.

7. Repeat steps 1 through 6 for two additional UWRCL x-ray beams, UW80-M and UW50-M. (UWRCL beam quality specifications are described in the attached Table I: Tungsten Anode X-ray Beam Qualities).

10/21/10 University of Wisconsin RCL

III. Measurement Results

The  exposure  rate attenuation results for the supplied fabric samples are detailed in the tables below. The fourth column, Ratio of Attenuation, is the quotient of the value stated in column 3 divided by the value stated in column 4.

Table 1: Sample 1, Grey Sports Bra, Left Side

Table 2: Sample 2, Bra Insert, Brief, Single layer shiled material.

Table 3: Sample 3, Leaf Sample, 2 Layers thick (Ovary Plus )

Report prepared by John A. Micka, UWRCL on October 21, 2010.

University of Wisconsin RCL     10/21/10

UNIVERSITY OF WISCONSIN RADIATION CALIBRATION LABORATORY

Rm. B1002 WIMR, 1111 Highland Ave., Madison, WI 53705-2275 Phone: (608) 262-6320 Fax: (608) 262-5012

TABLE 1: TUNGSTEN ANODE X-RAY BEAM QUALITIES

The University of Wisconsin Accredited Dosimetry Calibration Laboratory has created a series of X-ray beam qualities that were selected to match the beam qualities offered by the National Institute of Standards and Technology (NIST). The University of Wisconsin matches these beam qualities with an Advanced X-Ray constant potential generator by setting the same kVcp as the NIST beam quality and adjusting the additional filtration to appropriate NIST beams. The following table lists the beam qualities now offered by the University of Wisconsin. The numeric value in the beam code corresponds to the kVcp of the x-ray unit. The letters L and M in the beam code indicate Light and Moderate filtration, respectively. HVL1 is the first Half-Value Layer and HC is the Homogeneity Coefficient (Ratio of HVL1/HVL2 times 100). Inherent filtration for the UW Tungsten Anode X-ray unit is 3.0 mm of beryllium. Please note that interpolation of calibrations between the L and M beams is not recommended.

Added Filter HVL1 HVL1 HC Air Kerma Rate

Beam Code (mm Al or Cu) (mm Al) (mm Cu) (percent) (mGy/sec)

Form Revised 01/SEP/2008

80 kVp Spectra vs Tungsten Filtration

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