Ponencia presentada en el XIX Congreso Internacional de Acústica (ICA2007), Madrid, 2-7 Sep 2007.-- PACS: 43.35Zc.A new transduction system for obtaining ultrasonic images of flaws in pieces accessible from two external planes, using a very low number of piezoelectric transducers, is analysed. The system is based on two arrays of transducers working in near field conditions and which insonify the inspected piece from perpendicular planes.Two data acquisition techniques have been developed from the transduction system proposed, depending on how complex the defect of the piece inspected is. Ultrasonic images are generated by combining different traces that are acquired by the transducers. To this purpose, specific digital signal processing algorithms developed for each of the two acquisition techniques are required.The results of the inspection of a methacrylate piece with reflectors located in different positions are presented using the two data acquisition techniques based on the transduction system put forward. Three case studies are presented: in the first only one punctual flaw is included, in the second two punctual reflectors have been simulated, whereas in the third, and more complicated case, several flaws are included forming a "<" sign.This work has been partially supported by the Spanish MEC, R&D Project CICYT Ref. DPI2005-00124 of the I+D National Plan.Peer reviewed