Assessing the conditions for in vivo electrical virtual biopsies in Barrett's oesophagus

It has previously been shown that it is possible to differentiate between s quamous and columnar epithelia in rat and resected human tissues using an i mpedance probe to make in vitro measurements. This probe can be passed down an endoscope allowing measurements to be made in patients. However, the pr obe emerges parallel to the oesophageal wall, with little room to manoeuvre . The conditions of control required to give reliable readings have been in vestigated The importance of pressure applied and the angle of approach to the oesophagus was assessed. Pressures in the range 26.6 Pa to 46.3 kPa and angles in the range 15-90 degrees were considered. In in vitro studies it was observed that it was possible to obtain consistent readings with pressu res greater than 2.9 kPa and with angles greater than 15 degrees between th e probe and the oesophagus. These conditions can be achieved in vivo, and r eadings obtained from twelve patients are shown (45 readings on normal squa mous, 34 on Barrett's oesophagus and 22 on stomach). At low frequencies (9. 6-153.2 kHz), a Mann-Whitney test shows a significant difference (p < 0.001 ) when comparing the means from squamous and columnar, and also when readin gs from Barret's and normal gastric epithelia are compared (p < 0.001).