<prompt> Best investigation of planning radiotherapy for carcinoma of esophagus?PETCT ScanUSGMRI  <response>: Ans. isai.e., PETPrior to radiotherapy, the extent of tumor and its spread is assessed to target tre area for radiotherapy.CT scan, endoscopic USG and FDG-PET are used for esophageal carcinoma, bt for accurate radiotherapy planning PET scan is far superior to CT or endoscopic USG. 