Matsui, Kazuma
Yanagi, Itaru
Goto, Yusuke
Takeda, Ken-ichi
Article History
Received: 26 June 2015
Accepted: 6 November 2015
First Online: 4 December 2015
Competing interests
: Financial support for this study was provided by Hitachi, Ltd. K. M., I. Y., Y. G. and K. T. are current employees of Hitachi, Ltd.