I am writing the Acknowledgements of my thesis and I would like to know if it's necessary to use the official academic titles. For instance "Thanks Dr.X for his invaluable help in ....", but it could happen that actually Dr.X is a Professor, or he prefers the D.Phil or PhD. Should I make a little research to be sure that no one will feel "offended"? Or is there some consensus about this matter?
Thanks in advance.