فصلنامه لیزر در پزشکی
سال ششم شماره 3 (پیاپی 32، پاییز 1388)

In this paper, Thermal stress in dentin and enamel has been simulated and investigated, analytically. For this reason, we consider heat deposited in dentin and enamel due to CW Er: YAG laser radiation. The steady state heat conduction equation has been solved and the temperature distributions in dentin and enamel have been derived and thermal stress due to nonhomogenous temperature distribution then has been obtained. By using the enamel and dentin data and the obtained equations the thermal stress in dentin and enamel have been investigated and discussed.

The main problem of the most previous works on DTI segmentation is the parametric approach used for modeling tensor statistics in a region of interest which may not effectively model the tensor statistics in white-matter fiber bundles. In this work, we propose the Parzen density estimation with a Gaussian kernel to define region statistics in diffusion tensor images. This estimation is used to segment biological rat spinal cord phantom in a nonparametric statistical surface evolution algorithm framework. We demonstrate through numerical experiment that the statistical evolution surface with Euclidean distance derived from the non-parametric approach outperforms the evolution surface associated to the parametric case. In fact, both statistical modeling and metric are important to improve the quality of DTI segmentation results. Finally, it has shown that the most important element of kernel density estimation is the choice of the bandwidths. We conclude that if the parametric statistical modeling does not end up in a specific application with desired segmentation results, despite high computation cost of nonparametric method, nonparametric method is a reasonable choice.

To evaluate the clera canal diameters at optic nerve head in patients with nonarteritic anterior ischemic optic neuropathy (NAION) using optical coherence tomography (OCT) and compare the results with fellow eyes and control group. In a prospective study, optic nerve head OCT was performed in acute phase of NAION. Horizontal and vertical diameters of the scleral canal at optic disc i.e. the termination of the retinal pigment epithelium, were recorded. The data was compared with fellow eyes and an age- and sex-matched normal control group. Thirty eyes of 30 patients and 20 eyes of 20 normal subjects were studied. Scleral canal diameters were the same for normal fellow eyes, optic atrophy fellow eyes and control eyes. Scleral canal diameters of NAION eyes were significantly greater than control and normal fellow eyes (P<0.001), however, the difference was not significant for optic atrophy fellow eyes. Although in the acute phase, the scleral canal diameters were greater in NAION eyes, no significant difference was found between normal fellow eyes and control eyes.

Glioblastoma is one of the most common and a dangerous cancer of central nervous system. Targeted radiotherapy is an effective method in its treatment. IUdR is -a thymine analog- known as a radiation sensitizer in cancer therapy. It has been reported that Methoxyamine increase base cutting healing blocking in DNA damages levels in cells derived from human Glioblastoma, while the degree of DNA fractures in larger spheroids were decreased, this matter was affected by increasing in IUdR uptake by harvested cells in G0 phase is. HIF-1α is a transcription factor for endothelial cells stop cell cycle phase G o / G 1. Recently has been recognized that activity by HIF-1α can be cause 2 - Methoxyestradiol inhibited, this issue that is leads to inhibition of cell cycle stopping. In this study we have investigated combineding effect 2 - Methoxyestradiol on radio sensitivity consideration of IUdR in Spheroid cell culture model Glioblastoma. U87MG cells cytotoxic damages were tested by colony assay and the colonogenic ability of cells were evaluated and compared in 350 microns spheroieds. Our results shown that the damage resulted by ionizing radiation before yielding in IUdR treated with estradiol and Methoxyamine much more (001 / 0 ≥ p) of the use each of these factors alone are. These results were indicated the important role of methoxyestradiol in related by IUdR in cancertherapy.

Rhegmatogenous retinal detachment (RRD) is a grave ocular disease which is caused secondary to the presence of a retinal break or hole and fluid current through them into the subretinal space.There are multiple peripheral retinal lesions predisposing thinner peripheral retina to creation of a break. Closing these breaks and holes by creating a chorioretinal adhesion is a logic treatment. Laser photocoagulation is the most convenient and widely used method to make a firm adhesion between retina and underlying choroid. Considering the wide variety of the retinal lesions and the unique potential of each lesion to advance toward retinal detachment, prophylactic treatment of peripheral retinal lesions with laser should be restricted only to the evidence based indications. In this brief review different predisposing lesion and studies encouraging their treatment will be discussed.