Changes in hydrocarbons and elemental distribution in peloids during maturation processes (Secovlje Salina Nature Park Slovenia).

In Secovlje Salina Nature Park, the therapeutic mud matured in the natural sedimentary environmental site. This work aimed to determine the influence of the peloid maturation process on the hydrocarbon and elemental distributions, as well as changes in morphology. For this purpose, the sample before and after maturation was examined using various methods. n-Alkanes were the most abundant among saturated hydrocarbons in both immature and mature peloid samples. The results showed that the maturation mainly influenced the change in distribution and concentration (from 378 to 1958 ppm) of n-alkanes. The organic matter (OM) of the immature peloid sample was characterized by a slight prevalence of long-chain and odd carbon-numbered n-alkanes, maximizing at n-C27. However, mature peloid's OM showed a similar share of short-, mid- and long-chain n-alkanes with a slight dominance of short-chain members, maximizing at n-C16. The origin of short-chain and even carbon-numbered n-alkanes was attributed to microbial precursors (e.g., Leptolyngbyaceae). Hopanes were considerably more dominant compared to steranes in both peloids. The hopane series of immature peloid was characterized by the dominance of 22,29,30-trinor-hop-5(6)-ene (C27 hopene), as well as the presence of C30-hop-22(29)-ene (diploptene), which are widespread in cyanobacterial species. The aromatic fraction of immature peloid pointed to the predominance of polycyclic aromatic hydrocarbons (PAHs). As peloid aging progressed, the sample was richer in methyl-branched alkanes, carboxylic acids, their methyl esters, and thermodynamically more stable hopanes and steranes. The presence of elements with toxicological relevance during maturation was reduced below the limits prescribed in most of the directives for cosmetic products. It specifically refers to: As, Ni and Se. A higher concentration of total sulfur in the mature peloid can be related to gypsum precipitation in the summer and/or more intensive microbial activity.

Photocatalytic degradation of methylene blue under natural sunlight using iron titanate nanoparticles prepared by a modified sol-gel method.

The aim of this work was to synthesize semiconducting oxide nanoparticles using a simple method with low production cost to be applied in natural sunlight for photocatalytic degradation of pollutants in waste water. Iron titanate (Fe2TiO5) nanoparticles with an orthorhombic structure were successfully synthesized using a modified sol-gel method and calcination at 750°C. The as-prepared Fe2TiO5 nanoparticles exhibited a moderate specific surface area. The mesoporous Fe2TiO5 nanoparticles possessed strong absorption in the visible-light region and the band gap was estimated to be around 2.16 eV. The photocatalytic activity was evaluated by the degradation of methylene blue under natural sunlight. The effect of parameters such as the amount of catalyst, initial concentration of the dye and pH of the dye solution on the removal efficiency of methylene blue was investigated. Fe2TiO5 showed high degradation efficiency in a strong alkaline medium that can be the result of the facilitated formation of OH radicals due to an increased concentration of hydroxyl ions.

SU-E-T-386: Gamma Analysis of Normalized and Un-Normalized Dose Distributions.

PURPOSE: The gamma index method, as currently implemented in all commercial QA software, calls for selection of a normalization point to evaluate agreement between two dose distributions. The implication of this is that there is an infinite number of possible solutions! Which one to pick? A unique and more relevant solution is obtained only if no normalization point is used. METHODS AND MATERIALS: The set of test cases suggested by the AAPM TG1 19 were planned using Pinnacle 8.0m and delivered on a Varian 21EX linac for 6 and 18 MV photons. The recommended point and planar dose measurements were obtained using a Pinpoint ion chamber, EDR2 film and MatriXX. The gamma index method using typical 3%, 3 mm criteria with and without a normalization point was used to assess the agreement between calculated and delivered planar dose distributions. The analysis was extended to a set of data for clinically treated patients. RESULTS: The comparison with the TG119 benchmark data showed that all point dose and planar measurements for 6 MV were within the published range. Similar results, although without published data to compare with, were obtained for 18 MV as well. For all complex tests, the percentage of points passing the gamma criteria of 3%, 3 mm was (95.8±1.6)% and (95.6±1.0)% for 6 MV and 18 MV, respectively. Without a normalization point, however, the same gamma analysis fell to (20.7±6.7)% and (13.9±4.0)% for 6 MV and 18 MV, respectively. The clinical data set showed the same trend, with the gamma passing rate declining from (98.9±0.7)% to (33.4±13.1)%. CONCLUSION: The gamma index method provides a unique answer for gamma passing rate only without normalizing dose distributions to any particular point. The common gamma criteria of 3%, 3 mm, however, is a very poor metric in that case.

SU-E-T-274: Monte Carlo Simulations of Output Factors for a Small Animal Irradiator.

PURPOSE: Measurement of dosimetric parameters of small photon beams, with field sizes as small 1 mm in diameter, is particularly challenging. This work utilizes Monte Carlo techniques to calculate percent depth dose (PDD) and output factors for small photon fields from a kV x-ray based small animal irradiator. METHODS: Absolute dose calibration of a commercial small animal stereotactic irradiator (XRAD225, Precision X-ray) was performed in accordance with the recommendations of AAPM TG-61 protocol. Both in-air and in-water calibrations were performed at a 30.4 cm source-to-surface distance (SSD) for a reference collimator 50 mm in diameter. The BEAM/EGS was used to model 225 kV photon beams used for most therapeutic applications. The Monte Carlo model was provided good agreement with measured beam characteristics, e.g. PDD and off-axis ratios. Subsequently, output factors for various square and circular applicators were measured using an ionization chamber and radiochromic film, and compared with MC simulations. Directional Bremsstrahlung splitting (DBS) was utilized for variance reduction to improve efficiency of the output factor simulations. The statistical uncertainty on the MC- calculated results is between 0.5% and 1% for most points. RESULTS: The absolute dose measured for reference collimator at 30.4 cm SSD in water and in air is 4.1 and 4.12 Gy/min. The agreement between simulated and measured output factors was excellent, ranging from 1% to 2.84%. The MC- simulated and measured depth dose data, normalized at the surface, show excellent agreement, with a maximum deviation is approximately 2.5 %. CONCLUSIONS: Monte Carlo simulation provides an indispensible tool for validating measurements of the smallest field sizes used in preclinical small animal irradiation.

Dosimetric characterization of an image-guided stereotactic small animal irradiator.

Small animal irradiation provides an important tool used by preclinical studies to assess and optimize new treatment strategies such as stereotactic ablative radiotherapy. Characterization of radiation beams that are clinically and geometrically scaled for the small animal model is uniquely challenging for orthovoltage energies and minute field sizes. The irradiator employs a commercial x-ray device (XRAD 320, Precision x-ray, Inc.) with a custom collimation system to produce 1-10 mm diameter beams and a 50 mm reference beam. Absolute calibrations were performed using the AAPM TG-61 methodology. Beam's half-value layer (HVL) and timer error were measured with an ionization chamber. Percent depth dose (PDD), output factors (OFs) and off-axis ratios were measured using radiochromic film, a diode and a pinpoint ionization chamber at 19.76 and 24.76 cm source-to-surface distance (SSD). PDD measurements were also compared with Monte Carlo (MC) simulations. In-air and in-water absolute calibrations for the reference 50 mm diameter collimator at 19.76 cm SSD were measured as 20.96 and 20.79 Gy min(-1), respectively, agreeing within 0.8%. The HVL at 250 kVp and 15 mAs was measured to be 0.45 mm Cu. The reference field PDD MC simulation results agree with measured data within 3.5%. PDD data demonstrate typical increased penetration with increasing field size and SSD. For collimators larger than 5 mm in diameter, OFs measured using film, an ion chamber and a diode were within 3% agreement.

An x-ray image guidance system for small animal stereotactic irradiation.

An x-ray image-guided small animal stereotactic irradiator was developed and characterized to enable tumor visualization and accurate target localization for small field, high dose irradiation. The system utilizes a custom collimation system, a motorized positioning system (x, y, θ), a digital imaging panel and operating software, and is integrated with a commercial x-ray unit. The essential characteristics of the irradiator include small radiation fields (1-10 mm), high dose rate (>10 Gy min(-1)) and submillimeter target localization. The software enables computer-controlled image acquisition, stage motion and target localization providing simple and precise automated target localization. The imaging panel was characterized in terms of signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and spatial resolution. Overall localization accuracy and precision were assessed. SNR, CNR and spatial resolution are 24 dB, 21 dB and 2.8 lp mm(-1), respectively, and localization accuracy is approximately 65 µm with 6 µm precision. With the aid of image guidance, system performance was subsequently used to evaluate radiation response in a rat orthotopic lung tumor effectively sparing normal tissues and in a mouse normal lung. The capabilities of 3D treatment and cone-beam computed tomography are presented for 3D localization and delivery as a work in progress.

MicroRT-small animal conformal irradiator.

A novel small animal conformal radiation therapy system has been designed and prototyped: MicroRT. The microRT system integrates multimodality imaging, radiation treatment planning, and conformal radiation therapy that utilizes a clinical 192Ir isotope high dose rate source as the radiation source (teletherapy). A multiparameter dose calculation algorithm based on Monte Carlo dose distribution simulations is used to efficiently and accurately calculate doses for treatment planning purposes. A series of precisely machined tungsten collimators mounted onto a cylindrical collimator assembly is used to provide the radiation beam portals. The current design allows a source-to-target distance range of 1-8 cm at four beam angles: 0 degrees (beam oriented down), 90 degrees, 180 degrees, and 270 degrees. The animal is anesthetized and placed in an immobilization device with built-in fiducial markers and scanned using a computed tomography, magnetic resonance, or positron emission tomography scanner prior to irradiation. Treatment plans using up to four beam orientations are created utilizing a custom treatment planning system-microRTP. A three-axis computer-controlled stage that supports and accurately positions the animals is programmed to place the animal relative to the radiation beams according to the microRTP plan. The microRT system positioning accuracy was found to be submillimeter. The radiation source is guided through one of four catheter channels and placed in line with the tungsten collimators to deliver the conformal radiation treatment. The microRT hardware specifications, the accuracy of the treatment planning and positioning systems, and some typical procedures for radiobiological experiments that can be performed with the microRT device are presented.

Light-emitting-diode-based light source for calibration of an intensified charge-coupled device detection system intended for galvanoluminescence measurements.

A spectrally tunable light source utilizing three light-emitting diodes (LEDs) for calibration of a highly sensitive intensified charge-coupled device (ICCD) optical detection system intended for time-resolved galvanoluminescence (GL) measurements is described. The source has been conceived as a low-cost substitute for standard tungsten lamps usually used for relative and absolute calibration of optical detection systems. Three LEDs with different spectral characteristics in conjunction with a system of two integrating spheres as light mixers and light reducers are used. This construction provides control over the source spectrum by changing individual LED contributions. The use of integration spheres eliminated angular distribution of light intensities of LEDs as well as angular dependence of their spectral contributions. Moreover, by using the source we have avoided the problem of stray and diffuse light of higher wavelengths, as well as different light intensities for different wavelengths (up to three orders of magnitude in the range from 400 nm to 750 nm), which we have with standard tungsten lamps. A complete calibration procedure for the LED source and ICCD detection system is described. Finally, for the first time, we have performed time-resolved spectral GL measurements during aluminum anodization in porous film-forming electrolyte phosphoric acid in a transient regime. Two peaks at 425 nm and 595 nm are recognized, confirming the same mechanism of GL in both transient and steady-state regimes of anodization.

Critical behavior at the isotropic-to-nematic phase transition in a bent-core liquid crystal.

Magnetic birefringence and dynamic light scattering measurements of orientational order parameter fluctuations at the isotropic-nematic phase transition of a bent-core liquid crystal reveal a pretransitional temperature dependence consistent with the standard Landau-deGennes mean field theory. However, as follows: the transition in the bent-core compound is more weakly first order (TNI-T* approximately 0.4 degrees C), the leading Landau coefficient is approximately 30 times lower, the viscosity associated with nematic order fluctuations is approximately 10 times higher, and the density change is approximately 10 times lower, than typically observed in calamitic (rod-shaped) liquid crystals. One consistent explanation for these anomalies is an optically isotropic phase composed of microscopic complexes or "clusters" of bent-core molecules.

Optically isotropic liquid-crystal phase of bent-core molecules with polar nanostructure.

We found that the optically isotropic (I(M)) mesophase observed recently below the nematic phase of the bent-core liquid crystal 4-chlororesorcinol bis[4-(4-n-dodecyloxybenzoyloxy)benzoate] shows ferroelectric-type switching. Polarizing microscopic, electric current, dielectric, and dynamic light scattering studies lead us to propose that the I(M) phase is composed of interconnected orthoconic racemic smectic (Sm-Ca P(F)) nanodomains with random layer orientations. Near the nematic phase, where the polarization can be saturated by electric fields, the system responds in a fashion analogous to the granular structure of a magnetic spin glass--in particular, we observed that the relaxation back to the nonpoled structure follows a similar, inverse logarithmic rule.

Optical studies of the nematic phase of an oxazole-derived bent-core liquid crystal.

Various optical and dynamic light scattering studies have been conducted on the nematic phase of an oxazole-derived bent-core liquid crystal. At optical length scales and in the absence of applied fields, homogeneously aligned samples of this material, which has an oxazole heterocyclic ring in the central core, are found to behave more like a conventional straight-core nematic than a previously investigated ester-based class of bent-core molecules that have a benzene ring as the core linkage between the two arms of the bow-shaped molecule. In particular, the nematic refractive indices of the oxazole compound combine in the standard way [i.e., square root of ((2no2+ne2)/3)] to match the isotropic value throughout the nematic range, and the observed director fluctuation modes have relaxation rates comparable to those of the usual thermotropics. However, polarized light scattering data reveal evidence of weak biaxial fluctuations, and indications of electric-field-induced biaxiality are observed in the refractive index measurements.

Light scattering study of a twist grain boundary liquid crystal.

Dynamic light scattering is used to probe the fluctuation modes of a liquid crystal exhibiting twist grain boundary (TGB) structure. At the chiral nematic to proposed "chiral line liquid" phase transition, anomalous temperature dependence in the fluctuation spectrum and an instability in the helicoidal director structure signify developing TGB order. At lower temperatures, the behavior of the smectic layer-director fluctuations ("soft" mode) indicates that the previously identified commensurate TGB(A) phase may in fact be a TGB(C) phase with an unusually small tilt angle.

Carcinosarcoma of the mandibular mucosa: the first report.

A 67-year-old man was referred with a squamous cell carcinoma of the left mandibular alveolar ridge verified elsewhere by an exploratory excision. After extensive staging and preoperative irradiation, a radical surgical attempt was performed. Histopathological examination and immunohistochemical analysis revealed the first case of a carcinosarcoma of the mandibular alveolar ridge. Clinical and histopathological features are presented, and treatment and prognosis are discussed.

Dynamics of the nematic phase of a bent-core liquid crystal.

The dielectric fluctuations in the uniaxial nematic phase of a bent-core liquid crystal have been studied by dynamic light scattering. Polarization selection of the scattering cross-section reveals one mode due to ordinary director fluctuations and, in the lower part of the nematic phase, a second mode attributable to fluctuations of the biaxial order parameter. The director fluctuations are approximately 100 times slower than observed in typical nematics based on straight-core molecules, suggesting that the bent core nematogenic units may be microscopic smectic domains ("cybotactic" clusters).

Wooden foreign bodies in facial injury: a radiological pitfall.

Foreign bodies can present a diagnostic challenge to the maxillofacial surgeon. Three patients, who suffered from a penetrating injury with a wooden foreign body, were examined and treated. Their preoperative CT and MRI scans were evaluated. In an acute case, the penetrating wooden body mimicked air bubbles. In the other two patients, the wood was retained for several months and appeared with a much higher density on CT. In MRI the wooden foreign bodies gave a low signal intensity. In all injuries removal of the foreign body was delayed, because it was initially radiologically missed or misdiagnosed. In the appropriate trauma setting a penetrating wooden body must always be considered. Its attenuation value increases with time as water is absorbed from the surrounding tissues. Although the radiological appearance may show a great variety, CT imaging is the basic diagnostic technique. MRI is the method of second choice.

[Tracheobronchial perforations--a complication after mouth, maxillary and facial surgery]. / Tracheobronchiale Perforationen--eine Komplikation nach mund-, kiefer- und gesichtschirurgischen Eingriffen.

After difficult endotracheal intubation in oral and maxillofacial surgery, esophageal or tracheal injuries can cause mediastinal, pericardial or cervicofacial soft tissue emphysema. If a patient has of thoracic pain after general anesthesia, mediastinal emphysema should be taken into consideration because of the possibility of subsequent life-threatening complications. Diagnosis can be established with computed tomography and fiber-endoscopy. We present the diagnostic and therapeutic management of two patients.

One-step resection and reconstruction of the mandible using computer-aided techniques--experimental and clinical results.

In patients with advanced oral cancer, a resection of the mandible continuity is often indicated. This new method presented here uses computer-aided design and manufacturing (CAD/CAM) for preoperative fabrication of individual mandibular prostheses and their corresponding resection templates in a direct fashion without the need for additional physical models. In this experimental application, a segment of a dried mandible was resected and replaced by a titanium prosthesis prefabricated by CAD/CAM. It was the aim of this investigation to verify the processing chain and its precision, i.e., the fit of an individual implant, such as this. Although this new technique offers fascinating opportunities, possible clinical drawbacks have to be taken into account.

Destruction of the glenoid joint fossa by a tenosynovial giant-cell tumour of the skull base: a case report.

A 63-year-old man is presented in whom a tenosynovial giant-cell tumour had destroyed the temporomandibular joint fossa and expanded intracranially. The lesion was not diagnosed for a period of at least two years. Treatment included wide resection including the surrounding bone, dura and condyle.

[Problems in diagnosis and therapy of carcinoma in stroma-abundant pleomorphic adenoma of the parotid gland]. / Problematik der Diagnostik und Therapie des Karzinoms im stromareichen pleomorphen Adenom der Glandula parotis.

The case is reported of a 27-year-old patient who developed multiple recurrences of a carcinoma arising from richly stromal pleomorphic adenoma of the parotid gland over 13 years. Originally the tumor was classified as a benign pleomorphic adenoma because there were no cytological characteristics of malignancy. Later on the diagnosis had to be modified to that of a carcinoma arising from a pleomorphic adenoma because of the infiltrating growth pattern of the tumor. A multicentric local recurrence and metastases on the left side of the neck supported the correct diagnosis. This case demonstrates that, beside the classic cytological criteria of malignancy invasion and penetration of the capsule can be decisive for the diagnosis of malign transformed pleomorphic adenoma. Treatment and prognosis of salivary gland tumors assume a clear determination of their diguity. The unusual course in this case of a pleomorphic adenoma originally diagnosed as benign demonstrates the importance of regular follow-up.

[Pigmented villonodular synovitis of the temporomandibular joint with invasion of middle cranial fossa]. / Pigmentierte villonoduläre Synovitis des Kiefergelenks mit Einbruch in die mittlere Schädelgrube.

A 63-year-old man is presented in whom a tenosynovail giant-cell tumor destroyed the right temporomandibular joint and fossa and showed extensive intracranial growth. Because of uncharacteristic complaints, a symptomatic treatment was performed elsewhere. The lesion was finally resected under endotracheal anesthesia. After 20 months free of recurrence the patient's outcome is very satisfying. Differential diagnosis and therapy are discussed.