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A Angelopoulos

Publications and source records attributed to A Angelopoulos.

34 records · Page 2Linked to original sources
PubMed1998

Monte Carlo and TLD dosimetry of an 192Ir high dose-rate brachytherapy source.

An analytical Monte Carlo simulation code has been used to perform dosimetry calculations around an 192Ir high dose-rate brachytherapy source utilized in the widely used microSelectron afterloaded system. Radial dose functions, dose rate constant and anisotropy functions, utilized in the AAPM Task Group 43 dose estimation formalism, have been calculated. In addition, measurements of anisotropy functions using LiF TLD-100 rods have been performed in a polystyrene phantom to support our Monte Carlo calculations. The energy dependence of LiF TLD response was investigated over the whole range of measurement distances and angles. TLD measurements and Monte Carlo calculations are in agreement to each other and agree with published data. The influence of phantom dimensions on calculations was also investigated. Radial dose functions were found to depend significantly on phantom dimensions at radial distances near phantom edges. Deviations of up to 25% are observed at these distances due to the lack of full scattering conditions, indicating that body dimensions should be taken into account in treatment planning when the absorbed dose is calculated near body edges. On the other hand, anisotropy functions do not demonstrate a strong dependence on phantom dimensions. However, these functions depend on radial distance at angles close to the longitudinal axis of the source, where deviations of up to 20% are observed.

Anisotropy↗
PubMed1992

Dose rate distributions around 60Co, 137Cs, 198Au, 192Ir, 241Am, 125I (models 6702 and 6711) brachytherapy sources and the nuclide 99Tcm.

Simple analytical functions derived from our point source Monte Carlo calculations on the combined attenuation and scatter factor, B exp(-mu r), for 60Co, 137Cs, 198Au, 192Ir, 241Am, 125I (models 6702 and 6711) brachytherapy sources and the nuclide 99Tcm, for water spherical geometries of radii R = 15 and 20 cm, are presented. Our results for the broadly used 60Co, 137Cs, 198Au and 192Ir brachytherapy sources can be compared directly and found in excellent agreement with the widely accepted data of Meisberger et al in the limited distance range for which the latter are valid. Our data, however, can be used with high accuracy outside this distance range. Many discrepancies observed among different data sets available in recent literature are attributable to differences in geometries used. The results for the recently introduced 241Am source are very dissimilar to those produced by any other currently used brachytherapy source. Dose rate distributions, based on the above simple functions, are proposed in accordance with the recommendations for calibration of the brachytherapy sources in terms of reference air kerma rate and were found to be in good agreement with data available in the literature. Our calculations for 125I sources (models 6702 and 6711), provided that the characteristic x-rays from titanium encapsulation are taken into account, support recent experimental and theoretical dose rate distributions indicating that currently accepted values for 125I may be overestimated.

Americium↗
PubMed1991

Accurate Monte Carlo calculations of the combined attenuation and build-up factors, for energies (20-1500 keV) and distances (0-10 cm) relevant in brachytherapy.

The combined build-up and attenuation factor, B exp (-mu r), of point isotropic photon sources in a water medium has been calculated using the Monte Carlo method, for energies (20-1500 keV) and distances (1-10 cm) relevant in brachytherapy. For the transport of photons and electrons, up-to-date and self-consistent total, partial and differential cross sections were used. The influence of coherent (Rayleigh) and incoherent (Compton) scattering, as well as the effects of the source and medium geometries on the calculations, were investigated in detail and it was found that these effects can lead to significant deviations from published data, especially at low energies and/or large distances from the sources. Our results can be used for any mono- or multi-energetic photon source in the energy range 20-1500 keV with uncertainties of the order of 2-3%, and they may influence treatment planning especially in the case of organs at risk which are usually near the edge of the body.

Brachytherapy↗
PubMed1987

Changes of oscillatory potentials of the ERG in diabetic retinopathy.

Disturbances of the oscillatory potentials of the ERG are examined in diabetic patients with and without vascular lesions of the retina. More specifically, the changes of the oscillatory potentials are investigated in relation to the manifestation and evolution of diabetic retinopathy and neovascularization of the optic disk and the retina. Particular stress is laid on the direct relation between the disturbances of the oscillatory potentials and the occurrence of neovascularization, as well as on the prognostic significance of these disturbances.

Aneurysm↗
PubMed1982

Direct immunofluorescence in oral lichen planus.

Direct immunofluorescent staining (DIF) was performed on biopsy specimens from thirty-five patients with oral lichen planus. The results showed fibrin deposition in all cases at the mucosal-submucosal interface, within colloid bodies (fourteen of thirty-five) and within vascular walls (five of thirty-five). Deposition of IgG, IgA and IgM was detected to a lesser extent, while complement (C3) could not be identified in any case. The significance of these findings was assessed by comparison with the IF results obtained in thirty-five biopsies from various oral diseases other than lichen planus and ten healty persons. Although the presence of fibrin deposition at the mucosal-submucosal junction, within vessels and cytoid bodies, was found to be highly characteristic of lichen planus, these findings were not specifically diagnostic. Morphologically identical deposits were also seen in lupus erythematosus. It is known at present whether immunologic reactions may play a role in the pathogenesis of lichen planus. However, the immunopathologic findings may occasionally be additional suggestive markers in the diagnosis of the disease.

Complement C3↗
PubMed1982

Verruciform xanthoma of the oral mucosa.

An additional case of verruciform xanthoma in the oral cavity is presented. The clinical and light microscopic findings in this case are similar to those previously described. In addition, the clinical features of 47 cases that could be found in the literature are summarized and discussed.

Adolescent↗
PubMed1981

Immunofluorescent study of cytologic smears in oral pemphigus: A simple diagnostic technique.

This study was undertaken in order to explore the diagnostic efficacy of the direct immunofluorescent technique for demonstration in vivo bound immunoglobulins to desquamated epithelial cells from patients with oral pemphigus. Cytologic smears were obtained with a wooden spatula from the oral lesions of thirty patients with known pemphigus vulgaris. Control smears were taken from thirty-five patients twenty suffering from various other mucosal diseases and fifteen devoid of oral lesions. The smears were stored at -30 degrees C. and prepared within 48 hours for examination by the direct immunofluorescent technique. Deposition of IgG was demonstrated in all thirty smears from the oral pemphigus lesions. None of the control smears gave positive results. These findings suggest that the direct immunofluorescent technique using cytologic smears may provide an additional simple and reliable method in the diagnosis or oral pemphigus vulgaris.

Diagnosis, Differential↗
PubMed1981

Cicatricial pemphigoid: direct and indirect immunofluorescent studies.

Oral mucosa, skin tissue, and serum samples from thirty-three patients with cicatricial pemphigoid were studied by the direct and indirect immunofluorescent techniques to determine the presence of tissue-bound and circulating antibodies. A linear continuous basement membrane zone pattern was observed in 96.9 percent of the oral mucosa biopsy specimens studied. This pattern is indistinguishable from the pattern observed in bullous pemphigoid. In 97 percent of the cases clinically healthy skin biopsy specimens were negative for basement membrane zone staining. Circulating anti-basement membrane zone antibodies were present in 36.4 percent of thirty-three patients with cicatricial pemphigoid in low titer (1:10 to 1:40), when normal oral mucosa was used as substrate. The demonstration of tissue-bound and circulating basement membrane zone antibodies in cicatricial pemphigoid morphologically identical to those found in bullous pemphigoid provides further support for the concept that the two diseases may represent variants of the same entity.

Adult↗
PubMed1981

Immunofluorescent studies in desquamative gingivitis.

Twenty-seven patients (19 females and 8 males) with a clinically diagnosed desquamative gingivitis were used in this study. Twenty-seven additional patients with oral and skin diseases and with gingival involvement other than that of the desquamative gingivitis type served as controls. Biopsy gingival specimens were sectioned and stained with H and E. The rest of the tissue specimen was cut with a cryostat and used for immunofluorescent assays of the tissue-bound antibodies (IgG, IgA, IgM, C3 anf fibrin). Circulating antibodies were determined by using the indirect immunofluorescence method in serum samples. Normal human oral mucosa and several animal epithelial tissues were used as substrates. The immunopathologic findings suggest the diagnosis of lichen planus in the presence of linear or granular fibrin deposition at the basement membrane zone/mucosal submucosal interface with or without cytoid bodies and cicatricial pemphigoid, in the presence of circulating and/or tissue-bound immunoglobulins and C3 in a linear continuous pattern along the BMZ. It is suggested that an accurate diagnosis of the underlying disease of the desquamative gingivitis can be made on the bases of the clinical, histopathologic, immunopathologic and follow-up findings.

Adult↗
PubMed1981

Melanin pigmentation and inflammation in human gingiva.

The study was carried out to determine the distribution of melanin granules in different anatomical areas of the gingiva and to relate the density of melanin granules to the degree of gingival inflammation. Specimens including free and part of the attached gingiva were secured from the vestibular surfaces of the six maxillary or mandibular teeth of 21 Caucasian subjects during periodontal surgery. Serial histologic sections 5 to 6 mu thick were prepared and stained with Hematoxylin and Eosin or Masson-Fontana. Evaluation of the H & E stained sections disclosed that the number of melanophores and melanin granules in the epithelium and the inflammatory cells of the subepithelial connective tissue gradually decreased from the free gingival groove area to the free gingival crest and from the free gingival groove to the mucogingival junction. The density of melanophores in the vestibular epithelium showed a significant positive correlation (r = 0.38, P less than 0.00003) with the severity of inflammation (numbers of inflammatory cells) in the attached gingiva but not in the free gingiva (r = -0.033, P less than 0.2643). There was a positive significant correlation between the density of melanin granules of the vestibular epithelium and that of the adjacent connective tissue in both the free (r = 0.57, P less than 0.0003) and attached gingiva (r = 0.46, P less than 0.0003).

Adult↗