Ionizing radiation generated during medical imaging procedures is a matter of concern. However, the current status of radiopharmaceutical use in stress myocardial perfusion imaging (MPI) and the radiation exposure from these radiopharmaceuticals is unknown in Japan.

A nationwide survey was conducted from June through July 2016. The questionnaires on the radiopharmaceuticals used and their administered doses during stress MPI were sent to 641 nuclear medicine facilities. The responses were collected from 431 facilities and the effective dose (ED) for an adult with standard body weight was calculated. Forty-three percent of the facilities used only ²⁰¹TlCl, 35% used only ^99mTc radiopharmaceuticals, and the remaining 22% used both. The two main reasons for using ²⁰¹TlCl instead of ^99mTc radiopharmaceuticals were “more familiarity with the usage of ²⁰¹TlCl than ^99mTc radiopharmaceuticals” and “apprehension about increasing the burden of physicians performing tracer injection twice.” The mean ED was 14.0 ± 5.5 mSv (range, 3.9 to 25.2 mSv), which was higher than that reported in other countries.

The ED of stress MPI radiopharmaceuticals in Japan is probably higher than the world standard because more than 50% of the facilities still use ²⁰¹TlCl. We recommend revising the routine stress MPI protocol to reduce the effects of ionizing radiation.