Proposed changes to ANSI/HPS N13.32 "Performance Testing of ExtremityDosimeters"

["Sandy Perle" <sandyfl@EARTHLINK.NET>]

In order to provide the health physics community information 

regarding the development of standards, and, to obtain pertinent 

feedback that can be incorporated into the standards development 

process, various venues are being pursued. Below are draft positions 

taken by the N13.32 Working Group. Formal presentations are being 

made, including the recent 22nd Annual International Dosimetry 

Symposium and National Dosimetry Records Conference, and the upcoming 

Thermo Electron Users Meeting, and, the FL HPS and AAPM Meeting. 



The N13.32 Working Group had identified twelve major issues for 

consideration.  The following paragraphs describe how the Group 

implemented the draft resolution of the issues.  Some of the issues 

are treated in greater detail in the appendices that were written to 

provide greater insight and convenience.  The working group made the 

most significant changes to the 1995 version of the standard in the 

areas of test categories and test criteria.



The working group attempted to harmonize the test categories with 

those in the sister standard, ANSI HPS N13.11-2001.  Particularly, 

the photon test categories in the protection level dose range were 

combined so that the previous test categories for low-energy and high-

energy photons, categories II and III, are now both included in test 

category II for photons.  In addition, the number of x-ray fields 

available for testing in the photon category was increased from four 

x-ray fields and one high-energy photon field to six x-ray fields and 

two high-energy photon fields.  The beta category now included as 

category III, remains unchanged except for the addition of a low-

energy beta source as an alternative to 204Tl.  



The working group considered the inclusion of a neutron-testing 

category based on the recommendation in the journal of the ICRU, 

Volume 1, No. 3 (2001) "Dosimetry for Irradiation of the 

Extremities."  At this time, though, the working group felt that the 

theoretical basis of neutron dosimetry to extremities has not reached 

a level of national and international agreement to promote the 

practice of neutron extremity dosimetry by inclusion of a testing 

category.  



At the request of the dosimetry community, two additional test 

categories were added, photon-mixture and beta/photon-mixture 

categories.  These categories were added to accommodate test 

participants submitting wrist dosimeters with the capabilities to 

interpret Hp (0.07) in mixed fields.  To clarify the intent of the 

new categories, the working group also added an option, requested by 

the test participant, for blind testing.  Participation in the 

mixture categories is only available to participants who submit 

dosimeters for blind testing.  Normal testing, as in the last version 

of the standard, includes only categories I through III with the 

testing source identified to the participant before analysis.  The 

working group does not recommend blind testing for single element 

extremity dosimeters. 



The range of testing doses has remained unchanged, although the 

working group agreed to adopt personal dose equivalent at 0.07 mm as 

the basis of the test of performance.  Guidance provided in 

international documents indicates that directional dose equivalent is 

a suitable approximation to personal dose equivalent.  Conversion 

coefficients for photons, listed in ICRU 67, were used with digitized 

spectra for the NIST x-ray beams to determine coefficients to convert 

air kerma to personal dose equivalent for the x-ray testing fields.  

Research has shown that the dose rate at 0.07 mm used for beta 

particles incident on the slab phantom is applicable for use with the 

rod and pillar phantoms.  In selecting personal dose equivalent at 

0.07 mm, the working group chose to exclude a discussion of lens-of-

the-eye (LOE) dose.  The group concluded that it was inappropriate to 

include LOE dose as part of a standard addressing extremity dose.



For practical purposes, the polylmethyl methacrylate  (PMMA) rod 

phantom will continue to be used for testing of finger dosimeters.  

The pillar phantom with the aluminum insert will be replaced by a 

PMMA phantom of the same dimensions.  The backscatter from the PMMA 

pillar phantom in photon fields is more similar to the ICRU tissue 

phantom for which the conversion coefficients have been determined.  

The working group considered the use of the water-filled PMMA pillar 

phantom by conducting a controlled irradiation of extremity 

dosimeters on PMMA, water-filled PMMA, aluminum-core PMMA and 

Styrofoam pillar phantoms.  The results did not yield evidence that 

the backscatter conditions to the dosimeter were significantly 

enhanced using the water-filled PMMA phantom over the PMMA phantom.  



The criteria for testing the performance of personal extremity 

dosimeter systems has historically taken a systematic approach, i.e., 

testing the performance of a group of dosimeters rather than basing 

the test on individual dosimeter results.  This philosophy was 

continued for this version of the standard; however, the model for 

testing was modified.  In the past, the test of performance was based 

on a) the sum of the absolute value of the bias and standard 

deviation of fifteen dosimeters irradiated in a single test category 

and b) limits on the individual values of bias and standard 

deviation.  In this standard, an approach was taken to combine the 

two values in quadrature consistent with current theory in quality.  

The approach has decreased the area of acceptable performance by less 

than three percent.



The working group modified the required ancillary tests to further 

distinguish between type tests and periodic tests.  The requirements 

for the lower limit of detection and angular response testing were 

removed from this standard, as they constitute one-time tests that 

should be performed upon the initial implementation or modification 

of a dosimeter system.  Recommended protocols for those studies are 

described in the attached appendices.  In addition to those studies, 

the working group modified the standard to also recommend the study 

of uncertainty for each dosimeter system.  Guidance, based on the ISO 

Guide to Uncertainty in Measurements, is given in the appendices for 

the approach to uncertainty analysis.



The Working Group anticipates ballotting this standard sometime 

during the next 6 months. Additional updates will be provided to the 

industry for feedback.



If you have specific comments, please provide them to Rick Cummings 

CUMMFM@inel.gov .. Chair, N13.32 Working Group, or directly to me.



Sandy Perle

Chair, HPSSC





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