1. Medical Physics Laboratory; University of Ioannina Medical School; Ioannina 45110 Greece
2. Departamento de Física - CIOyN, Regional Campus of International Excellence ‘Campus Mare Nostrum’; Universidad de Murcia; E-30100 Murcia Spain
3. Departament de Física Aplicada; Universitat d'Alacant; E-03080 Alacant Spain