Perturbative forward solver software for small localized fluorophores in tissue

In this paper a forward solver software for the time domain and the CW domain based on the Born approximation for simulating the effect of small localized fluorophores embedded in a non-fluorescent biological tissue is proposed. The fluorescence emission is treated with a mathematical model that describes the migration of photons from the source to the fluorophore and of emitted fluorescent photons from the fluorophore to the detector for all those geometries for which Green’s functions are available. Subroutines written in FORTRAN that can be used for calculating the fluorescent signal for the infinite medium and for the slab are provided with a linked file. With these subroutines, quantities such as reflectance, transmittance, and fluence rate can be calculated

Uptake and localisation of mTHPC (Foscan®) and its14C-labelled form in normal and tumour tissues of the hamster squamous cell carcinoma model: a comparative study

The aim of this study was to evaluate the pharmacokinetics of meta(tetrahydroxyphenyl)chlorin (mTHPC) on different tissues of interest in a hamster tumour model and to confirm our earlier animal studies on semi-quantitative fluorescence microscopy. The results obtained by three different evaluation methods were compared: in vivo spectrofluorometry, ex vivo fluorescence microscopy and chemical extraction of 14C-labelled mTHPC. Following intracardiac injection of 0.5 mg kg−1 mTHPC, groups of five tumour-bearing animals were used for in situ light-induced fluorescence spectroscopy. Afterwards, the biopsies were taken and snap frozen for fluorescence microscopy. The presence of radioactivity in serum and tissues was determined after chemical digestion in scintillation fluid using a scintillation counter. For each analysed tissue, a good correlation was observed between the three evaluation methods. The highest fluorescence intensity and quantities of mTHPC were observed between 12 and 24 h in liver, kidney, serum, vascular endothelium and advanced neoplasia. The majority of mTHPC was found at around 48 h in smooth muscle and at 96 h in healthy cheek pouch mucosa and early malignant lesions. The lowest level of mTHPC was noted in striated muscle at all times. No selectivity in dye localisation was observed between early squamous cell carcinoma and healthy mucosa. Soon after the injection, a significant selectivity was noted for advanced squamous cell carcinoma as compared to healthy cheek pouch mucosa or striated muscle. A significant difference in mTHPC localisation and quantity was also observed between striated and smooth muscle during the first 48 h following the injection. Finally, this study demonstrated the usefulness of non-invasive in situ spectroscopic measurements to be performed systematically prior to photodynamic therapy as a real-time monitoring for each treated patient in order to individualise and adapt the light dosimetry and avoid over or under treatments

Laser chemical vapor deposition of platinum: conductivity measurements and Schottky diodes

Laser chem. vapor deposition (LCVD) of Pt from Pt bishexafluoroacetylacetonate was studied. The elec. cond. of the metallic deposit was investigated as a function of the writing speed, the vapor pressure of the organometallic compd., and the laser power at 458 and 514 nm. The current-voltage characteristics of Schottky diodes made by LCVD of Pt on n-GaAs was compared for 2 different LCVD mechanisms. Suggestions to optimize the LCVD process are given

Gas phase versus surface contributions to photolytic laser chemical vapor deposition rates

The rate of cw photolytic laser chem. vapor deposition (LCVD) of Pt was measured for l = 350 nm as a function of light intensity and metalorg. vapor pressure. The growth of the metal films was studied in situ and in real time by monitoring optical transmission. At low intensities the transmitted light decreases monotonically with time, and the LCVD process is photolytic with its rate limiting step in the surface adlayer. At higher intensities 2 distinct time domains were obsd. An improved method for distinguishing between adlayer and gas-phase limiting processes is demonstrated. These observations are confirmed by studying the photolytic deposition rates while varying the thickness of the adlayer