Evaluating Volatile Plant Compounds of Psidium galapageium (Myrtales: Myrtaceae) as Repellents Against Invasive Parasitic Diptera in the Galapagos Islands.

Plant-based repellents represent a safe, economic, and viable alternative to managing invasive insects that threaten native fauna. Observations of self-medication in animals can provide important cues to the medicinal properties of plants. A recent study in the Galapagos Islands found that Darwin's finches apply the leaves of Psidium galapageium (Hooker 1847) to their feathers, extracts of which were repellent to mosquitoes and the parasitic fly Philornis downsi (Dodge & Aitkens 1968; Diptera: Muscidae). Introduced mosquitoes are suspected vectors of avian pathogens in the Galapagos Islands, whereas the larvae of P. downsi are blood-feeders, causing significant declines of the endemic avifauna. In this study, we investigated the volatile compounds found in P. galapageium, testing each against a model organism, the mosquito Anopheles arabiensis (Patton 1905; Diptera: Culicidae), with the aim of singling out the most effective compound for repelling dipterans. Examinations of an ethanolic extract of P. galapageium, its essential oil and each of their respective fractions, revealed a mixture of monoterpenes and sesquiterpenes, the latter consisting mainly of guaiol, trans-nerolidol, and ß-eudesmol. Of these, trans-nerolidol was identified as the most effective repellent to mosquitoes. This was subsequently tested at four different concentrations against P. downsi, but we did not find a repellence response. A tendency to avoid the compound was observed, albeit significance was not achieved in any case. The lack of repellence suggests that flies may respond to a combination of the volatile compounds found in P. galapageium, rather than to a single compound.

Micropropagation and Cryoconservation of the Endangered Plant Species Artemisia laciniata (Asteraceae).

BACKGROUND: Artemisia laciniata, mainly distributed in Siberia and Central Asia, is classified as critically endangered in Europe. OBJECTIVES: This study developed a protocol for its micropropagation and cryopreservation. MATERIALS AND METHODS: In vitro cultures from fresh seed and in vivo shoots were initiated. Micropropagation and cryopreservation protocols were developed. Bacteria detected after cryopreservation were investigated using 16S rRNA analysis. Genome size measurements of regenerated plants after cryopreservation using flow cytometry and carbon isotope measurements to evaluate stress status were also carried out. RESULTS: A. laciniata from both starting materials could be successfully propagated on MS medium with 0.5 uM BAP. Material initiated from in vivo shoots yielded lower regeneration percentages (16%) after cryopreservation than material generated from seed (57 and 63%) using the droplet-vitrification method and PVS3. Bacteria occurring after cryopreservation belonged to the genera Sphingomonas, Staphylococcus, Curtobacterium and Gordonia. There was no significant difference in the genome size and stress status between non-cryopreserved and cryopreserved plants. CONCLUSION: A. laciniata could be readily micropropagated and cryopreserved. No negative effects of cryopreservation on plant water use efficiency or on genetic stability were found.

A method for the production of composite scintillators for dosimetry in diagnostic radiology.

Plastic scintillators are used in the dosimetry of photons in radiotherapy. Their use in diagnostic radiology is affected by the drop in response at lower photon energies due to inadequate composition (effective atomic number) and chemical quenching. To compensate for this deficiency, a method for the production of composite polystyrene-based plastic scintillators was devised allowing the incorporation of inorganic scintillation powder. Disks of 10 mm diameter and 1 mm thickness optimized for a flat energy response referred to kerma in air were produced using CaWO(4), ZnS:Ag and CaF(2):Eu as additives. In an HVL range of 2.26-13.69 mmAl, the response was within an interval of +/-2.8% for CaF(2):Eu as additive, +/-3.2% for CaWO(4) and +/-10.9% for ZnS:Ag, respectively. The response of a commercial plastic scintillator (BC470) stays within +/-13.6%. The temperature dependence of the composite scintillator using CaF(2):Eu is lowest with a variation of +3.7% to -3.6% in an interval from 5 degrees C to 45 degrees C. The deficiency in photon absorption at lower energies due to the effective atomic number is reduced but not fully compensated by the additive scintillators. The optimized concentrations were established for the scintillator dimensions used.

A pilot study exploring the possibility of establishing guidance levels in x-ray directed interventional procedures.

This article summarizes the dosimetric results of an International Atomic Energy Agency coordinated research program to investigate the feasibility of adopting guidance levels for invasive coronary artery procedures. The main study collected clinical data from hospitals located in five countries. A total of 2265 coronary angiograms (CA) and 1844 percutaneous coronary interventions (PCI) were analyzed. Substudies evaluated the dosimetric performance of 14 fluoroscopes, skin dose maps obtained using film, the quality of CA procedures, and the complexity of PCI procedures. Kerma-area product (PKA) guidance levels of 50 and 125 Gy cm2 are suggested for CA and PCI procedures. These levels should be adjusted for the complexity of the procedures performed in a given institution.

Radioluminescence of some optical fibres.

Measurement of radiation fields with small scintillators as detectors for radiation dose is an attractive method provided that the scintillator luminescence can be discriminated against other unwanted signals. In diagnostic radiology radioluminescence of the optical fibres required for a transmission of the luminescence to an optical detector is the only source for such an impairment of the signal. To find fibres with low radioluminosity a survey of ten commercial fibres including polystyrene (PS), polystyrene wavelength shifting fibres, poly-methylmetacrylate (PMMA) and silica as fibre core material was made. Measurements were made with two photomultipliers of different spectral response and a clinical x-ray unit. Lowest radioluminosity was obtained with PMMA fibres. Depending on spectral sensitivity of the multiplier clear PS fibres give five to ten times the luminescence of PMMA. From the silica fibres only one high-OH fibre gave comparable results for wavelength up to 520 nm. Wavelength shifting fibres and silica fibres with low OH-content show strong fluorescence and are not suitable fibre materials.

Bosentan therapy for pulmonary arterial hypertension associated with hereditary haemorrhagic telangiectasia.

Hereditary haemorrhagic telangiectasia (HHT) is a disorder of arteriovenous malformations and telangiectases. In rare cases affected individuals may develop typical pulmonary arterial hypertension (PAH). Vasodilator therapy has not been recommended because of a potential increase in arteriovenous shunt volume. This report is on two patients with severe HHT-associated PAH who were treated with bosentan, an oral endothelin ET(A)/ET(B) receptor antagonist. After 1 year, symptomatic and functional improvements were confirmed by haemodynamic evaluation demonstrating a significant decrease of mean pulmonary artery pressures and an increase in cardiac index, without evidence for an increase in effective shunt volume.

A fit method for the determination of inherent filtration with diagnostic x-ray units.

A method for the determination of total inherent filtration for clinical x-ray units using attenuation curves was devised. A model for the calculation of x-ray spectra is used to calculate kerma values which are then adjusted to the experimental data in minimizing the sum of the squared relative differences in kerma using a modified simplex fit process. The model considers tube voltage, voltage ripple, anode angle and additional filters. Fit parameters are the thickness of an additional inherent Al filter and a general normalization factor. Nineteen sets of measurements including attenuation data for three tube voltages and five Al-filter settings each were obtained. Relative differences of experimental and calculated kerma using the data for the additional filter thickness are within a range of -7.6% to 6.4%. Quality curves, i.e. the relationship of additional filtration to HVL, are often used to determine filtration but the results show that standard quality curves do not reflect the variety of conditions encountered in practice. To relate the thickness of the additional filter to the condition of the anode surface, the data fits were also made using tungsten as the filter material. These fits gave an identical fit quality compared to aluminium with a tungsten filter thickness of 2.12-8.21 microm which is within the range of the additional absorbing layers determined for rough anodes.

LiF:W as a scintillator for dosimetry in diagnostic radiology.

The use of ionization chambers in diagnostic radiology is not feasible in measurement situations requiring small and robust dose sensors. The composition of LiF:W developed as a scintillator for the measurement of thermal neutrons seems profitable for an application in dosimetry of low-energy photons. Properties of a small LiF:W scintillator were determined with DV- and DH-standard radiation qualities. For a tube voltage range of 40 to 150 kV (corresponding to a HVL of 1.56 to 13.69 mm Al) a maximum variation in sensitivity of +/-13% was determined for a scintillator thickness of 3.7 mm. The scintillator signal was linear in a range from 6.6 mGy min(-1) to at least 13.7 Gy min(-1). Higher dose rates could not be obtained in the measurement setup. The temperature dependence of the luminescence response was found to decrease from +3.7% (at +2.5 degrees C) to -7.0% (at +45 degrees C) with respect to the luminescence response at 20 degrees C. LiF:W appears to be an interesting choice as a dosimetric scintillator in diagnostic radiology making immediate measurements of dose and dose rate with high spatial resolution feasible.

Spiral CT and radiation dose.

Recent studies in the USA and Europe state that computed tomography (CT) scans compromise only 3-5% of all radiological exams, but they contribute 35-45% of total radiation dose to the patient population. These studies lead to concern by several public authorities. Basis of CT-dose measurements is the computed tomography dose index (CTDI), which was established 1981. Nowadays there are several modifications of the CTDI values, which may lead to confusion. It is suggested to use the standardized CTDI-100 w. value together with the dose length product in all CT-examinations. These values should be printed on all CT-images and allows an evaluation of the individualized patient dose. Nowadays, radiologist's aim must be to work at the lowest maximal diagnostic acceptable signal to noise ratio. To decrease radiation dose radiologist should use low kV and mA, but high pitches. Newly developed CT-dose-reduction soft-wares and filters should be installed in all CT-machines. We should critically compare the average dose used for a specific examination with the reference dose used in this country and/or Europe. Greater differences should caution the radiologist. Finally, we as radiologists must check very carefully all indications and recommend alternative imaging methods. But we have also to teach our customers-patients and medical doctors who are non-radiologists-that a 'good' image is not that which show all possible information, but that which visualize 'only' the diagnostic necessary information.

Simulation of the effect of anode surface roughness on diagnostic x-ray spectra.

To simulate the effect of the condition of the anode surface on x-ray output the surface roughness of anode fragments of replaced clinical x-ray tubes was determined. A mean roughness of 1.32-5.22 microm giving effective tungsten absorption layers of up to 18 microm thickness in the direction of the x-ray beam was determined. X-ray spectra were then simulated using the measured surface profiles. The most prominent effect was the reduction of the kerma output of the tube with increasing roughness (-33% at 50 kV tube voltage and 5 microm roughness). The effects of beam hardening are less pronounced. The corresponding changes in the spectral parameters are generally small but largest for tube voltages up to 70 kV. For higher voltages the increased photon attenuation above the K-edge of tungsten reduces the effects of roughness on spectral parameters. The maximum shifts in mean photon energy of about 1 keV and in HVL of about 0.2 mm Al were obtained for an anode roughness of 5 microm.

Optimization of the composition of phantom materials for computed tomography.

Using available data for photon attenuation and tissue composition, a computer code was developed for the optimization of the composition of phantom materials for diagnostic radiology. The code allows selection of attenuation data in a photon energy range from 1 to 150 keV and the choice of a suitable weight function in the energy interval chosen. For applications in CT imaging a weight function is available reflecting the contribution of the x-ray spectrum to the CT-signal. Several phantom materials for CT were optimized (body fat, trabecular bone, an average bone composition for C4 vertebrae and water) by varying the mineral components in a polymer base in order to adjust x-ray attenuation properties. Measurements with the water equivalent material (PSPP1) showed good agreement of calculated and measured HU values (AHU = 7.3 +/- 5.3 at 80 kVp and 4.0 +/- 2.7 at 140 kVp) and little variation of HU for tube voltages from 80 to 140 kVp. The method provides a fast and flexible means for obtaining optimized phantom materials for a large variety of tissue compositions and energy ranges.

Temperature dependence of HU values for various water equivalent phantom materials.

The temperature dependence of water equivalent phantom materials used in radiotherapy and diagnostic imaging has been investigated. Samples of phantom materials based on epoxy resin, polyethylene, a polystyrene-polypropylene mixture and commercially available phantom materials (Solid Water, Gammex RMI and Plastic Water, Nuclear Associates) were scanned at temperatures from 15 to 40 degrees C and HU values determined. At a reference temperature of 20 degrees C materials optimized for CT applications give HU values close to zero while the commercial materials show an offset of 119.77 HU (Plastic Water) and 27.69 HU (Solid Water). Temperature dependence was lowest for epoxy-based materials (EPX-W: -0.23 HU degrees C(-1); Solid Water: -0.25 HU degrees C(-1)) and highest for a polyethylene-based material (X0: -0.72 HU degrees C(-1)). A material based on a mixture of polystyrene and polypropylene (PSPPI: -0.27 HU degrees C(-1)) is comparable to epoxy-based materials and water (-0.29 HU degrees C(-1)).

Production of phantom materials using polymer powder sintering under vacuum.

A technique is presented for the production of polymer-based phantom materials from solid polymer powders and various compounds added to adjust x-ray attenuation. After mixing of the finely grained components, the samples are solidified by a sintering process under vacuum. The method described allows a flexible and inexpensive production of phantom materials. Photon attenuation and density can be adjusted by suitable choice of base polymers and additives to mimic a large range of soft tissues and water.

[Dose classification in digital roentgen diagnosis: clinical applications]. / Dosisklassifikation bei digitalen Verfahren in der Röntgendiagnostik: klinische Applikationen.

Technological improvements in digital radiography and computed tomography have led to a substantial increase of radiation dose that subjectively cannot be detected. In order to reduce dose in a form that may be used in clinical practise, the quality of digital radiograms and computed tomography images should be classified in three classes. Low-dose investigations are indicated in children, in case of therapy control and for imaging organs with high differences in tissue contrast. High-dose investigations are scarcely indicated and middle-dose investigations should be performed in all other remaining clinical situations. Dose recommendations given by vendors in radiology should be viewed critically.

[A simple method for estimating effective dose in dental CT. Conversion factors and calculation examples for a clinical low dose protocol]. / Eine einfache Methode zur Abschätzung der effektiven Dosis bei Dental-CT. Konversionsfaktoren und exemplarische Berechnung für ein klinisches Low-Dose-Protokoll.

PURPOSE: An easily applicable method to estimate effective dose including in its definition the high radiosensitivity of the salivary glands from dental computed tomography is presented. Effective doses were calculated for a markedly dose reduced dental CT protocol as well as for standard settings. Data are compared with effective doses from the literature obtained with other modalities frequently used in dental care. METHODS: Conversion factors based on the weighted Computed Tomography Dose Index were derived from published data to calculate effective dose values for various CT exposure settings. RESULTS: Conversion factors determined can be used for clinically used kVp settings and prefiltrations. With reduced tube current an effective dose for a CT examination of the maxilla of 22 microSv can be achieved, which compares to values typically obtained with panoramic radiography (26 microSv). A CT scan of the mandible, respectively, gives 123 microSv comparable to a full mouth survey with intraoral films (150 microSv). CONCLUSION: For standard CT scan protocols of the mandible, effective doses exceed 600 microSv. Hence, low dose protocols for dental CT should be considered whenever feasable, especially for paediatric patients. If hard tissue diagnoses is performed, the potential of dose reduction is significant despite the higher image noise levels as readability is still adequate.

[Quality assurance of mammographic devices]. / Technische Qualitätssicherung in der Mammographie.

An account of the technical features of mammographic devices as a consequence of the radiological requirements for imaging the breast is given. For quality assurance of these features specific test procedures have been established which at least since the introduction of the MED-directive 97/43 of CEC have to be applied. A concise summary of these protocols is given.

Local calibrated bone mineral density in the mandible presented using a color coding scheme.

Calibrated information on bone mineral density (BMD) may be used in dental implantology to measure "bone quality". It can be used to estimate the expected primary implant stability preoperatively and to guide the surgeon in selecting optimum implant types and operation techniques. Using a preoperative dental computed tomography (Dental-CT) scan, all of this information can be obtained without additional examinations and thus without additional X-ray exposure of the patient. In contrast to bone mineral determination in other body regions, local BMD values are important in the jaw bone. Therefore, a regimen where color-coded information on local bone mineralization is superimposed on Dental-CT images is proposed using the original CT volumes as well as reformatted views.

Helical and conventional CT in the imaging of metallic foreign bodies in the orbit.

PURPOSE: To compare helical CT to conventional CT imaging in the assessment of orbital metallic foreign bodies with regard to image quality, scanning time, and radiation exposure. METHODS: Twenty-four standardized metallic foreign bodies, placed into the orbit (anterior, epibulbar, posterior) of cadaver heads were studied. Helical CT scanning in the axial plane with multiplanar reconstruction of coronal and sagittal images was performed as well as conventional CT imaging with direct scanning in the axial and the coronal planes (Tomoscan SR 7000, Philips, The Netherlands). Two masked observers consensually graded the studies using 5 predetermined criteria. Radiation dose delivered to the lens and scanning time were measured for the helical and the conventional CT imaging workup. RESULTS: Helical CT imaging scored statistically significantly better with regard to overall accuracy of foreign body localization and presence of beam-hardening streak artifacts from dental fillings. Conventional CT scored significantly better with regard to stair-step artifacts. The radiation dose delivered to the lens was 35.4 mGy for helical CT imaging and 73.9 mGy for conventional CT workup (axial and coronal scanning). Total scanning time was 18 seconds for helical CT axial scanning and 104 seconds for conventional CT axial and coronal scanning. CONCLUSION: Helical CT is superior to conventional CT imaging, because it can provide adequate information about orbital metallic foreign bodies with a single acquisition, thus reducing both the number of examinations and the radiation exposure for the patient.

Dry versus conventional laser imagers: film properties and image quality.

The authors compared image quality and stability with a dry laser imager versus a conventional wet laser imager. Hard copies of 56 magnetic resonance imaging and computed tomographic studies were analyzed for gray-scale distribution and temperature stability. Results with the dry laser imager did not reach the quality of results with a wet laser imager, but the performance and ecologic criteria were sufficient to make use of this technique advantageous.