DIAGNOSTIC-IMAGING WITH LIGHT

This paper reviews the evolution of optical imaging in diagnostic radi ology and examines recent progress. Although the idea has been around for many decades, interest in the development of an effective method h as never been so great. Optical imaging presents several potential adv antages over existing radiological techniques. First, the radiation is non-ionizing and therefore reasonable doses can be repeatedly employe d without harm to the patient. Second, optical methods offer the poten tial to differentiate between soft tissues with different optical abso rption or scatter, but which are indistinguishable using other modalit ies. And third, specific absorption by natural chromophores (such as h aemoglobin) allows functional information to be obtained. Principal cl inical applications include a means of detecting breast disease and a cerebral imaging modality for mapping oxygenation and haemodynamics in the brain of newborn infants or cortical functional activity in adult s. Past attempts to image tissues with light have been severely restri cted by the overwhelming scatter which occurs when optical radiation s preads through tissue: however, recent innovations in technology have suggested once again that it may be a practical possibility.