This is an open-label single photon emission computed tomography / computed tomography (SPECT/CT) study to investigate the safety and diagnostic performance of 99mTc-HYNIC-3PEG4-E[c(RGDfK)2) (99mTc-3PRGD2) in esophagus cancer patients. A single dose of nearly 11.1 MBq/kg body weight of 99mTc-3PRGD2 ( ≤ 20 µg 3PRGD2) will be intravenously injected into the patients in suspicion of esophagus cancer. Visual and semiquantitative method will be used to assess the whole-body planar and thoracic SPECT/CT images. Any adverse events will be collected from the patients.