Koen W.A. van Dongen received his MSc degree from Utrecht University, the Netherlands, in 1997. From 1998 to 2002, he worked for T&A Survey on the development of a directional borehole radar system. In 2002 and 2003 he worked as postdoctoral researcher on ground penetrating radar in the Laboratory of Electromagnetic Research at Delft University of Technology. From 2003 to 2005, he worked as a Marie-Curie Fellow on ultrasound thermometry in the Ultrasonic Research Group at University College Cork. In 2006, he moved to the Faculty of Applied Sciences, Delft University of Technology. Throughout these years, he worked on imaging, inversion, and modelling of (nonlinear) acoustic and electromagnetic wave fields.