Dose calculations involving I-125 interstitial brachytherapy sources were affected by two changes in low-energy seed dosimetry: implementation of a new primary air-kerma strength standard at the National Institute of Standards and Technology (NIST) on 1 January 1999 and (b) publication of revised dose-rate distributions in AAPM's Task Group 43 Report. AAPM guidance regarding these changes is available here: Guidance to Users of Nycomed Amersham and North American Scientific, Inc. I-125 Interstitial Sources: Dosimetry and Calibration Changes.

The .iphys physics files which accompany Plaque Simulator Version 6 use the NIST 1999 standards by default.