Endoscopic ultrasound and EBUS systems

Endoscopic ultrasound puts a miniature ultrasound transducer at the end of a flexible endoscope so that the probe sits millimetres from the target. Radial echoendoscopes give a 360-degree slice for staging how deeply oesophageal, gastric and rectal cancers invade the wall; linear or curvilinear scopes image in the plane of a needle channel so that fine-needle aspiration or core biopsy can be taken from pancreatic masses, lymph nodes, submucosal tumours and the left adrenal, and so that therapeutic procedures can be done: celiac plexus neurolysis for pancreatic cancer pain, fiducial placement for stereotactic radiotherapy, drainage of obstructed bile ducts and pancreatic collections, radiofrequency ablation of small pancreatic tumours and injection therapies. Endobronchial ultrasound applies the same design to the airway: a linear EBUS bronchoscope samples mediastinal and hilar lymph nodes for lung cancer staging, which the ASTER trial showed can replace surgical mediastinoscopy as the first test, and radial EBUS miniprobes guide biopsy of peripheral nodules. Olympus, Fujifilm and Pentax Medical (with Hitachi ultrasound processors) make the scopes and processors; Boston Scientific and Cook Medical make the needles.

EUS and EBUS are outpatient procedures under sedation with low complication rates and better accuracy than CT for wall depth and small nodes, but they depend heavily on operator skill, see only a few centimetres from the lumen, can miss nodes out of reach, and need cytopathology support on site.