<title>Clinical optical dose measurement for PDT: invasive and noninvasive techniques</title>

Light dosimetry for photodynamic therapy in the esophagus

“…Usually, radiant energy fluence rate is used to describe the light in the tissue since this quantity is related in a straightforward way to the radiant energy absorbed in the tissue, particularly by the sensitizer. From an experimental point of view, the radiant energy fluence rate is measured by using an isotropic optical probe [14][15][16][17][18][19][20], i.e., a detector with an omnidirectional sensitivity to the light. Irradiance is preferentially used to describe the light transferred at the boundaries, e.g., at the tissue surface or at the surface of the light distributor.…”

“…The first method consists of measuring this distribution by inserting an optical microprobe with an isotropic response [14][15][16][17][18][19][20] in the tissue. The position of the microprobe in the tissue must be known accurately and the microprobe should not significantly perturb the light distribution in the tissues.…”

“…The position of the microprobe in the tissue must be known accurately and the microprobe should not significantly perturb the light distribution in the tissues. In our experiments we use an isotropic probe based on the fluorescence of a ruby sphere glued to the end of an optical fiber [14,15]. The principle of this probe is that the fluorescence of the ruby sphere can be excited by visible light (between 350 and 650 nm) at the wavelengths of interest coming from nearly all directions in space.…”

Three-dimensional optical phantom and its application in photodynamic therapy

“…Typical values of g for soft tissue and 500-900 nm light vary between 0.7 and 0.99 [14]. The effective scattering coefficient Ј s ‫ס‬ s (1 − g) of the lung phantom was measured as 0.35 mm −1 by a non-invasive technique based on the measurement of the diffuse reflectance [15,16]. The predicted value was 0.3 mm −1 .…”

“…The visible radiation to be measured also causes broad band tissue/phantom autofluorescence which could interfere with the measurement of the isotropic probe [15]. Part of this autofluorescence, near 693 nm, interferes by directly entering the fiber.…”