An Ultrasound Imaging Technique to Measure Tumors in People With Pancreatic Ductal Adenocarcinoma (PDAC) or Gastrointestinal (GI) Adenocarcinoma

Participants will undergo research ultrasound (rUS1) within three days of their routine CECT scan. A subset of participants (up to 10) will undergo a second research US (rUS2) at 3-4 weeks after rUS1 and at least one month prior to the next planned clinical CECT