Since 1991 Mr Hopper has been working in the National Medical Centre. In this position he has lead a variety of research projects on the use of photodynamic therapy in the treatment of oral squamous cell carcinoma. This program is currently one of the largest in the world with over 400 treatments using the three main photosensitizers. Mr Hopper is the principal investigator on a series of ethically approved projects. His work has resulted in a number of publications and helped establish a clear role for this treatment in a variety of neoplastic conditions in the head and neck. This work has advanced rapidly by the development of interstitial treatment of tumours using image guidance systems developed with the department of imaging and medical physics. This has become a national referral service and approval of PDT for treat of cancer has been recognised as such in 2002. Other related areas of research are fluorescence diagnostics (optical techniques for tissue interrogation) and the use of PDT in the treatment of non-malignant conditions such as neurofibromatosis.