<prompt> The Investigation of choice for diagnosing Zollinger Ellison syndrome includesCT scanSelective angiographyMRIEndoscopic ultrasound  <response>: D Endoscopic ultrasound Endoscopic ultrasound EUS permits imaging of the pancreas with a high degree of resolution 5 mm. EUS modality is particularly helpful in excluding small neoplasms within the pancreas in assessing the presence of surrounding lymphnodes vascular involvement.SENSITIVITY OF IMAGING STUDIES IN ZOLLINGER ELLISON SYNDROMEStudySensitivity, Primary GastrinomaMetastatic GastrinomaUltrasound21-2814CT scan35-5935-72Selective angiography35-6833-86Portal venous sampling70-90NASASI55-7841MR!30-6071Octreoscan67-8680-100EUS80-100NA 