A. Angelopoulos

Peripheral giant cell granuloma. Clinicopathologic study of 224 new cases and review of 956 reported cases

The clinical and histopathological features of 224 new cases of peripheral giant cell granuloma were studied. In addition, the data from 956 previously reported cases in the literature were evaluated and compared with the present series. Females were found to be more commonly affected than males. All age groups were found to be affected with a relative predilection from 40 to 60 years of age. The mandible was more often affected than the maxilla. Clinically, the lesions were red in color, had a smooth surface and were rubbery or with a soft consistency. The most characteristic histologic features included a non-encapsulated highly cellular mass with abundant giant cells, inflammation, interstitial hemorrhage, hemosiderin deposits, mature bone or osteoid.

First direct observation of time-reversal non-invariance in the neutral-kaon system

Abstract We report on the first observation of time-reversal symmetry violation through a comparison of the probabilities of K 0 transforming into K0 and K0 into K 0 as a function of the neutral-kaon eigentime t. The comparison is based on the analysis of the neutral-kaon semileptonic decays recorded in the CPLEAR experiment. There, the strangeness of the neutral kaon at time t=0 was tagged by the kaon charge in the reaction p p → K ± π ∓ K 0 ( K 0 ) at rest, whereas the strangeness of the kaon at the decay time t=τ was tagged by the lepton charge in the final state. An average decay-rate asymmetry 〈 R( K 0 t=0 → e + π − ν t=τ )−R( K 0 t=0 → e − π + ν t=τ ) R( K 0 t=0 → e + π − ν t=τ )+R( K 0 t=0 → e − π + ν t=τ ) 〉=(6.6±1.3 stat ±1.0 syst )×10 −3 was measured over the interval 1 τ S τ S , thus leading to evidence for time-reversal non-invariance.

Experimental determination of the energy generated in nuclear cascades by a high energy beam

An already existing, sub-critical arrangement made of natural uranium and water moderator has been exposed to a low intensity (≈ 109 ppp) proton beam from CERN-PS at several kinetic energies from 600 MeV to 2.75 GeV. The energy delivered by the hadronic cascade induced by the beam in the device has been measured by the temperature rise of small sampling blocks of uranium located in several different positions inside the device and counting the fissions in thin probe foils of natural uranium. We find typically G ≈ 30 in reasonable agreement with calculations, where G is the ratio of the energy produced in the device to the energy delivered by the beam. This result opens the way to the realisation of the so-called Energy Amplifier, a practical device to produce energy from thorium or depleted uranium targets exposed to an intense high energy proton beam. Results show that the optimal kinetic is ≥ 1 GeV, below which G decreases but is still acceptable in the energy range explored

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.

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.

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.

Tests of CPT symmetry and quantum mechanics with experimental data from CPLEAR

Abstract We use fits to recent published CPLEAR data on neutral kaon decays to π + π − and πeν to constrain the CPT-violation parameters appearing in a formulation of the neutral kaon system as an open quantum-mechanical system. The obtained upper limits of the CPT-violation parameters are approaching the range suggested by certain ideas concerning quantum gravity.

Narrow stereotactic beam profile measurements using N-vinylpyrrolidone based polymer gels and magnetic resonance imaging

In this work, polymer gel-MRI dosimetry (using VIPAR gels), radiographic film and a PinPoint ion chamber were used for profile measurements of 6 MV x-ray stereotactic beams of 5 and 10 mm diameter. The VIPAR gel-MRI method exhibited a linear dose response up to 32 Gy. VIPAR gels were found to resolve the penumbra region quite accurately, provided that the in-plane image resolution of the related T2-map is adequate (< or = 0.53 mm). T2-map slice thickness had no significant effect on beam profile data. VIPAR measurements performed with a spatial resolution of 0.13 mm provided penumbra widths (80%-20% distance) of 1.34 and 1.70 mm for the 5 and 10 mm cones respectively. These widths were found to be significantly smaller than those obtained with the film (2.23 mm for the 5 mm cone, 2.45 mm for the 10 mm cone) and PinPoint (2.25 mm for the 5 mm cone, 2.52 mm for the 10 mm cone) methods. Regarding relative depth dose measurements, good correlation between VIPAR gel and PinPoint data was observed. In conclusion, polymer gel-MRI dosimetry can provide relatively accurate profile data for very small beams used in stereotactic radiosurgery since it can overcome, to some extent, the problems related to the finite size of conventional detectors.

Experimental verification of neutron phenomenology in lead and transmutation by adiabatic resonance crossing in accelerator driven systems

Energy and space distributions of spallation neutrons (from 2.5 and 3.57 GeV/c CERN proton beams) slowing down in a 3.3 x 3.3 x 3 m3 lead volume and neutron capture rates on long-lived fission fragments 99 Tc and 129 I demonstrate that Adiabatic Resonance Crossing (ARC) can be used to eliminate efficiently such nuclear waste and validate innovative simulation.

Dosimetry comparison of 192Ir sources.

192Ir sources besides being widely utilized in the field of conventional brachytherapy also find use in contemporary peripheral and coronal intravascular applications. In this study, the same Monte Carlo simulation code and input data were used to investigate differences between the dose rate distributions of the most commonly used 192Ir sources in the cm and mm distance range. Findings are discussed in view of differences in source and encapsulation dimensions as well as structural details. Results are presented in the AAPM TG-43 formalism, as generalized by AAPM TG-60, for five 192Ir HDR source designs as well as an LDR seed and an LDR wire source. Dose rate constants of the sources at r0 = 1 cm and r0 = 2 mm were found proportional to the corresponding geometry factors along the transverse source bisectors and an equation of the form lambda r0(cGyh(-1) U(-1)) = 1.12 x G(r0,90 degrees) provides results within clinical accuracy (less than 2%) for any 192Ir source. Radial dose functions do not depend significantly on source and encapsulation geometry and agree within 2% with that of a point 192Ir source. Anisotropy is of importance for accurate dosimetry at the cm distance range but it does not affect dose rate in the mm distance range significantly. At such short radial distances the source geometry factor defines the shape of isodose lines. Dose uniformity at given distances from the sources is strongly dependent on source dimensions as indicated by dose rate profiles in polar and Cartesian coordinates.