Dear all especially Marko and Christian Gaser, Marko, thank you very much for your quick answer. Indeed, my error was due to the modulation step but I need to obtain the modulated results for my job. How can I solve this modulation bug? Thanks in advance, Elena -- ********************************************************************** * Dra. María Elena Martino Casado * Unidad de Medicina y Cirugía Experimental * Hospital General Universitario Gregorio Marañón * Dr. Esquerdo, 46. E-28007 Madrid. SPAIN. * Fax #: +34 91 426 5108 Telf #: +34 91 426 5067 ext. 17 * e-mail:[log in to unmask] http://www.hggm.es/image **********************************************************************