In spite of the sharp increase in both private and government R&D fund, the number of newly approved medicines for market had decreased since the 1990s. This is attributed to a large extent to the bottleneck in the critical path arising from the great disparity between animal model in pre-clinical trial and human model in clinical trial. This bottleneck may be expected to be gotten rid of by change in paradigm of drug development based on microdosing, which is enabled by radiation-related imaging technology. However, this is impossible without being accompanied by interdisciplinary joint researches, in which clinical investigators belonging to medical schools or hospitals play the most decisive role. In this article, authors verify based on bibliometrics that Japan has not employed the opportunity for revitalizing drug research activities because Japanese researchers' attitude toward radiation technology may not be so positive in comparison with the US, and because the role which clinical investigators play in the phase of pre-clinical trial is smaller in Japan than in the US.