About article "Construct and predictive validity of clinical caries diagnostic criteria assessing lesion activity."

Letter to the editor about article: Nyvad B, Machiulskiene V, Baelum V (2003). Construct and predictive validity of clinical caries diagnostic criteria assessing lesion activity. J Dent Res 82:117-122. Published in: J Dent Res 82(11):862-863, 200

Anisotropy of volume-backscattered light

In many measurements used for the determination of optical properties of biological tissues, a detector with a small cone of acceptance is used. Therefore a small part of the anisotropically distributed backscattered light is detected. We present the results of Monte Carlo calculations and study the anisotropy of the direction distribution of volume-backscattered photons. Close to the source it is impossible to give a general correction factor to relate the measurements to theoretical results. Far from the source, the measured radiation divided by the square of the sine of the accepting angle of the detector is a relatively good approximation of the radiant exitance at the surface of the sample under investigation. We recommend the use of a detector with a large angle of acceptance for these kinds of measurements. (C) 1997 Optical Society of America

Optical properties of bovine muscle tissue in vitro; a comparison of methods

Abstract. We measured the optical properties of muscular tissue using several methods. Collimated transmission measurements of thin slabs showed spatial anisotropy of the scattering processes. Surface roughness of the sample disables the calculation of the extinction coefficient from these measurements. From angular intensity measurements we found a scattering asymmetry parameter g = 0.96. In fresh samples the optical diffusion constant D depends on the orientation with respect to the longitudinal direction of the muscular cells. From the D values we calculated s perpendicular to the longitudinal direction as 0.19 mm −1 (at 543 nm), 0.39 mm −1 (at 594 nm) and 0.59 mm −1 (at 632 nm). The values for D which we measured from samples that were frozen and thawed did not show dependence on orientation. From spectral dependent reflectance measurements we found an oxygenation degree of 0.61 and a reduced scattering coefficient s = 0.85 mm −1 around 560 nm

Use of tabulated cumulative density functions to generate pseudorandom numbers obeying specific distributions for Monte Carlo simulations

A new method for the generation of pseudorandom numbers, which obey a specific statistical distribution, is presented. As an example the generation of the scattering angle theta for Monte Carlo light-scattering simulations is shown, using real, peaked, scattering phase functions.</p

About article "Construct and predictive validity of clinical caries diagnostic criteria assessing lesion activity."

Letter to the editor about article: Nyvad B, Machiulskiene V, Baelum V (2003). Construct and predictive validity of clinical caries diagnostic criteria assessing lesion activity. J Dent Res 82:117-122. Published in: J Dent Res 82(11):862-863, 200

Autofluorescence of bulk sound and in vitro demineralized human root dentin

The aim of this paper is to report on the demineralization-induced changes in dentin autofluorescence. Confocal laser scanning microscopy (CLSM) images and fluorescence excitation and emission spectra of in vitro demineralized root surfaces and sound controls on the same tooth roots were compared. When observed in CLSM images, demineralized dentin, excited at 488 nm, gave an increased emission at 529 nm compared to sound dentin. The difference in fluorescence decreased deeper into the root, as the sound dentin underneath the lesion was reached. In contrast, when using fluorescence spectrophotometry, excitation around 460 and 488 nm yielded a lower emission around 520 nm for demineralized dentin than for sound dentin, but in a more pronounced peak. From excitation spectra for emission around 520 nm, it could be seen that in demineralized dentin the contribution of excitation between 480 and 520 nm was more important than in sound dentin. The recorded fluorescence in CLSM images was not affected by demineralization-caused changes in scattering and absorption properties, due to the small measurement volume. Thus, the increased fluorescence for demineralized dentin implies an increased quantum yield. In fluorescence spectrophotometry, where the measurement volume is large, changes in scattering and absorption do have an influence on the fluorescence signal. Then, increased absorption by non-fluorescing chromophores and increased re-absorption around the emission wavelength may compensate for the increase in quantum yield and absorption around the excitation wavelength by fluorophores