A case report of contrast‐enhanced harmonic ultrasonography for the diagnosis of an esophageal duplication cyst oleh Kazunori Adachi, Takashi Tashiro, Makiko Kato, Takanori Ito, Aya Kato, Masaaki Takayama, Shunsuke Kato, Satoshi Ono, Hisako Yoshimine, Akira Koshino, Kazuhiro Nagao, Yuji Kobayashi, Masahide Ebi, Naotaka Ogasawara, Makoto Sasaki, Kunio Kasugai