Propagation of light into scattering media is a complex problem that can be modeled using statistical methods such as Monte Carlo. Few Monte Carlo programs have so far included the information regarding the status of polarization of light before and after a scattering event. Different approaches have been followed and limited numerical values have been made available to the general public. In this paper, three different ways to build a Monte Carlo program for light propagation with polarization are given. Different groups have used the first two methods; the third method is original. Comparison in between Monte Carlo runs and Adding Doubling program yielded less than 1 % error.
In conclusion, circulating ANCA at transplant was associated with the development of vascular lesions in the graft but was not significantly correlated with graft survival. Most grafts were lost due to patient death, which was more likely if transplantation occurred <12 months following induction of remission of ANCA-positive vasculitis.
The development of a simple and well-tolerated rat window chamber has allowed direct comparison of the vascular effects of two photosensitizers, chloroaluminum sulfonated phthalocyanine (CASP) and dihematoporphyrin ether (DHE). CASP and DHE were given 4 days after the implantation of the window chamber. Photodynamic therapy (PDT) with CASP was performed 24 hours after intravenous injection (10 mg/kg) with light at 675 nm (power density 200 mW/cm2, incident energy 100 J). DHE was given in a similar fashion (5 mg/kg intraperitoneally; light at 630 nm with matching power density and energy settings 24 hours after injection). Using videomicroscopic and integrating sphere measurements, marked differences were noted in the vascular effects of these photosensitizers. DHE caused immediate hemorrhage and disruption of the postcapillary venules, while CASP induced vascular spasm starting 4 hours after the completion of PDT. Forty-eight hours after PDT, both systems demonstrated a loss of chamber-induced neovascularization.
This work has the potential to give an understanding of the time-scales of hypoxia and reoxygenation in vivo as tumors respond to radiation injury. This technique is of particular interest for hypofractionated therapies particularly treatments of only two or three treatments, where optimizing treatment timing can increase the tumorcidal effect of the remaining fractions.
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