An affordable, portable fluorescence imaging device for skin lesion detection using a dual wavelength approach for image contrast enhancement and aminolaevulinic acid-induced protoporphyrin IX. Part I. Design, spectral and spatial characteristics

Steady-state fluorescence imaging can be used in conjunction with selective exogenous or endogenous fluorescent compounds for the diagnosis of skin le sions, for example cancerous lesions. Depending on the excitation and emiss ion properties of the fluorescent compound used, various excitation and/or emission wavelengths can be chosen in order to allow fluorescence imaging. Unwanted background signals like autofluorescence and scattering can decrea se the image quality and hence the diagnosis potential of this imaging meth od. A method involving two excitation and/or emission wavelengths was used in order to suppress the unwanted background signal and allow contrast enha nced fluorescence imaging. A fluorescence imaging device prototype was asse mbled using both the two wavelength excitation method and the two wavelengt h emission method. Additionally, a white light source was included to allow the collection of images as seen with the naked eye. The prototype was des igned to be affordable and portable and was laid out towards the diagnosis of skin lesions using aminolaevulinic acid-induced protoporphyrin IX (PpIX) . This paper describes the excitation and detection characteristics of a fl uorescence imaging device prototype. This includes spectral and spatial cha racteristics of the various light sources included in the device as well as specifications of the image detector used. Furthermore, the image analysis procedure used for the dual wavelength excitation/emission is described.