Cylindrical Light Diffuser Research Articles

A Comparative Optical Analysis of Cylindrical Diffuser Fibres for Laser Therapy Using Fluorescence Imaging

. Cylindrical light diffusers are commercially available for clinical applications such as photodynamic therapy (PDT) and interstitial laser photocoagulation (ILP). A fluorescence imaging technique has been used to quantify the light distribution produced by each of six different diffuser fibres. The light distribution produced by each device was found to depend on the distance the light propagated in the fluorescent dye solution. At a distance of 1 mm from the diffuser midline, the measured profiles were found to be consistent with published results obtained in air at a similar distance. The three devices intended for PDT utilised scattering particles and reflectors in their construction. The profiles produced by these applicators revealed peaks that were attributed to the reflectors located at their distal tips. By comparison, the two etched ILP fibres displayed either a strong modulation in the profile due to non-uniform etching or a predominant forward peak associated with the conical shape of the tip. We conclude that it is important to take into account the forward-directed light emitted by the diffusers when considering clinical applications using these devices.

Measurement of the Emission Profiles of Cylindrical Light Diffusers Using a Video Technique

The uniformity of the emission profile produced by a cylindrical light diffuser is an important parameter for determining the light dose received by the target tissue during laser therapies such as photodynamic therapy (PDT) and interstitial laser photocoagulation (ILP). A technique originally used for determining the profile of a laser beam with a commercial video camera is adapted in order to measure the distribution of light from a cylindrical diffuser. The method can produce quantitative one-dimensional beam profiles in both the circumferential and axial direction of the light diffuser. The system allows the use of tissue phantoms that provide a convenient and effective method for comparing manufacturer's measurements often made in air with those to be expected in vivo. The technique is a quick and easy method for assessing light diffusers before treatment, and utilises readily available equipment that does not require specialist knowledge. Also, the response of the video camera facilitates the assessment of diffusers over a relatively broad optical spectrum, which encompasses the range of wavelengths currently used for both PDT (515-675 nm) and ILP (800-1064 nm).

Cylindrical fiberoptic light diffuser for medical applications.

A cylindrical light diffuser has been developed mainly for medical applications, including photodynamic therapy (PDT), in particular interstitial PDT, PDT of the bronchi, or intravascular PDT. The diffuser is based on a polymer optical fiber. The coupling of the light out of the core is controlled by the roughness mechanically induced on the surface of the core. The light is then isotropically diffused by a thin layer of a scattering medium. The active length can be 100 mm or more, whereas the outer diameter is 1 mm or less. The diffuser is flexible and can be introduced in tissue though a hypodermic needle. The main property of this light diffuser is the homogeneity of the light intensity emitted along its whole active length and around its circumference (360 degrees). Various intensity profiles can be made, including M-shape profiles for a homogeneous irradiance (+/- 10%) at a certain depth in the tissue. Furthermore, the diffuser is essentially isotropic and its optical properties are hardly dependent on wavelength. A diffuser for interstitial and intraluminal PDT has been developed. It is flexible, homogeneous, independent on wavelength, and can be made with a very high length-to-diameter ratio.