In vivo EBT radiochromic film dosimetry of electron beam for Total Skin Electron Therapy (TSET)

EBT radiochromic films were used to determine skin-dose maps for patients undergone Total Skin Electron Therapy (TSET). Gafchromic EBT radiochromic film is one of the newest radiation-induced auto-developing photon and electron-beam analysis films available for therapeutic radiation dosimetry in radiotherapy applications. EBT films can be particularly useful in TSET; due to patient morphology, underdosed regions typically occur, and the radiochromic film represents a suitable candidate for monitoring them.In this study, TSET was applied to treat cutaneous T-cell lymphoma. The technique for TSET was implemented by using an electron beam with a nominal energy of 6 MeV. The patient was treated in a standing position using dual angled fields in order to obtain the greatest dose uniformity along the patient's longitudinal axis. The electron beam energy was degraded by a PMMA filter. The in vivo dose distribution was determined through the use of EBT films, as well as of thermoluminescent dosimeters for comparison (TLDs). EBT results showed a reasonable agreement with TLDs data.     

Energy dependence of radiochromic dosimetry films for use in radiotherapy verification

Aim

The purpose of the study was to examine the energy dependence of Gafchromic EBT radiochromic dosimetry films, in order to assess their potential use in intensity-modulated radiotherapy (IMRT) verifications.

Materials and methods

The film samples were irradiated with doses from 0.1 to 12 Gy using photon beams from the energy range 1.25 MeV to 25 MV and the film response was measured using a flat-bed scanner. The samples were scanned and the film responses for different beam energies were compared.

Results

A high uncertainty in readout of the film response was observed for samples irradiated with doses lower than 1 Gy. The relative difference exceeds 20% for doses lower than 1 Gy while for doses over 1 Gy the measured film response differs by less than 5% for the whole examined energy range. The achieved uncertainty of the experimental procedure does not reveal any energy dependence of Gafchromic EBT film response in the investigated energy range.

Conclusions

Gafchromic EBT film does not show any energy dependence in the conditions typical for IMRT but the doses measured for pre-treatment plan verifications should exceed 1 Gy.     

Scanning orientation and polarization effects for XRQA radiochromic film

Gafchromic XRQA radiochromic film, is an effective tool for quality assurance and dose assessment in kilovoltage radiotherapy and diagnostic applications. Like other Gafchromic film products, XRQA film exhibits a variation in dose to reflected optical density response with angle of rotation when analysed with a light source that is partially or fully polarised such as a desktop scanner. Although warnings are not given on manufacturers specifications, this can affect dosimetry accuracy and we recommend that it is essential to scan all XRQA films in the same orientation. The effect is not as pronounced as EBT Gafchromic film. The magnitude of this variation has been measured and shown to be up to 16 ± 2% (1SD) using a fully linear polarised light source was seen with a 90° angle rotation. This would be the maximum variation seen on a desktop scanner with a fully polarised light source. For our standard desktop scanner (Epson v700) a mean variation of 2 ± 1% from 0 cGy to 20 cGy applied dose was measured as compared to 8 ± 2% for EBT Gafchromic. We recommend that to decrease uncertainty in dose measurement, accurate alignment of the calibration films to experimental films be performed on a regular basis. This is especially important if your desktop scanner has a high degree of polarization of its light source.     

Functional markers in wheat: technical and economic aspects

Speed and cost–effective techniques for evaluation of plant materials to provide information before entering the next cycle of selection are critical for success in plant breeding. Whether or not a ‘new’ technique realizes its potential depends on technical and economic considerations. Biotechnology-based research tools such as doubled haploid technology and molecular markers have already demonstrated their value for application in plant breeding. In the area of genomics, implementation of functional markers (FMs) is currently of particular interest. The pipeline from plant materials to FM data points for any application includes maceration of plant material, DNA isolation and sample preparation. For each step of this pipeline, a number of techniques are available, and no single method is ideally suited for all applications. The challenge is to meet the needs of many different scenarios which are present in a modern breeding programme such as the use of (1) few markers for genotyping hundreds of samples (e.g., marker assisted backcrossing (MAB)), (2) few markers in thousands of samples (e.g., screening for GMO), (3) hundreds to thousands of markers for hundreds to thousands of samples (e.g., genetic characterization of breeding materials (fingerprinting)). This paper compares different techniques for each of the steps from plant material to FM data point, with the main emphasis on SNP detection platforms, assuming that multiple FMs will become available in the near future. We focus on technical and economic aspects and discuss which techniques are most suitable for each of the scenarios using wheat as a model.     

Ultrastructural in situ hybridization: A review of technical aspects

Detection of nucleic acid sequence at the ultrastructural level has allowed us to better understand the expression of genes in some fields of application in cell biology. In situ hybridization at the ultrastructural level can be carried out using three different methods: on vibratome sections before embedding in epoxy resin, on ultrathin frozen section, or on ultrathin section of tissue embedded in hydrophilic resin such as Lowicryl. Before starting the detection of nucleic acid sequences at the electron microscope level, the experimenter has to choose various parameters: the type of tissue fixation, the probe and its label, and the in situ hybridization method, depending on the sensitivity, the resolution and the ultrastructural preservation required. This review of technical aspects, by describing the different methods of ultrastructural in situ hybridization, will help the experimenter to optimize each step of the hybridization procedure.     

Cryo-electron microscopy of an extremely halophilic microbe: technical aspects

Most halophilic Archaea of the class Halobacteriaceae depend on the presence of several molar sodium chloride for growth and cell integrity. This poses problems for structural studies, particularly for electron microscopy, where the high salt concentration results in diminished contrast. Since cryo-electron microscopy of intact cells provides new insights into the cellular and molecular organization under close-to-live conditions, we evaluated strategies and conditions to make halophilic microbes available for investigations in situ. Halobacterium salinarum, the test organism for this study, usually grows at 4.3 M NaCl. Adaptation to lower concentrations and subsequent NaCl reduction via dialysis led to still vital cells at 3 M salt. A comprehensive evaluation of vitrification parameters, thinning of frozen cells by focused-ion-beam micromachining, and cryo-electron microscopy revealed that structural studies under high salt conditions are possible in situ.

     

Control of the Asian tiger mosquito: technical and administrative aspects

The Community legislator, through Directives 2004/17/CE and 2004/18/CE, wanted dictate to the Member States some "guidelines" to be used in the field of public procurement of services, in order to promote, through an inner market growth, developing appropriate operational protocols to document in the race; that, has the aim at testify the consolidated technical capacity of Company which conferred the health reclamation provided by the "Plans to put public health emergencies". By its nature, the legislative regulatory act which is capable of directing the gradual harmonization of national laws, giving also each state full autonomy on the form and means to be taken. Therefore, the objectives of the Community directives must be properly incorporated and interpreted, including the legislative adaptation about the regulation of the disinfestations Enterprises.     

Legislative and technical aspects of mutagenicity testing.

A brief account is given of the history of the legislative acts that give responsibility to the U.S. Food and Drug Administration (FDA) for ensuring the safety of foods, drugs, and cosmetics. Within the present legislative framework the FDA has the authority to impose regulations which are designed to ensure the safety of all foods, drugs, and cosmetics. The existing legislative authority is adequate for this purpose; however, the difficulty lies instead with technology and the inadequacy of scientific perspective in the emerging area of mutagenicity testing. Earlier efforts in development of mutagenicity screening systems culminated only a few years ago in the proposal to use the host-mediated assay, somatic cell cytogenetics, and dominant lethal tests collectively. Subsequent research efforts indicated that there were serious practical and scientific deficiencies in using this approach. More recently a new proposal, the tier system, has been suggested as an alternative measure. The proposed tier system at FDA consists of three testing levels of increasing complexity. The first tier is an initial screening effort using techniques having maximum sensitivity that are also useful for large-scale, rapid testing. The second tier is designed to identify and confirm that the presumptive mutagens detected in the first tier are truly mutagenic for higher organisms, most especially, for mammals. The third tier would be devoted to explicit genetic tests in mammals designed to ascertain the imposed risk to man by the introduction of a mutagen in our environment. The FDA is currently involved in a number of research activities in the area of mutagenicity safety screening which will explore the adequacies and possible deficiencies of the tier system approach. These efforts are described for our in-house activities, our contract activities, and our cooperative and collaborative activities with other government agencies and institutions.     

Stereotactic systems and procedures for depth electrode placement: technical aspects

The authors describe the conversion of the Leksell spherical system to that of the orthogonal approach for depth electrode placement, by the addition of relatively simple devices to the main frame. These modifications have created the need for new instrumentation such as teleradiology with laser beam centering and the use of an all-purpose stereotactic chair. The main device used for the orthogonal approach is an instrument and electrode carrier moving on sliding side bars. This system can also take advantage of the newer imaging techniques, such as CT scanning, digital angiography and NMR, by the addition of computer markers which are interchangeable with the frame side bars.     

Gafchromic film dosimetry: Four years experience using FilmQA Pro software and Epson flatbed scanners

Purposes: To assess performance of FilmQA Pro software for pre-treatment patient-specific quality assurance (QA), using radiochromic films and two commercial flatbed scanners. To evaluate a novel multichannel approach compared to the classical red channel evaluation.Material and methodsPatient films (mostly EBT2 films, one box of EBT3) were digitalized using successively two flatbed scanners: the A4-size Epson V750 and the A3-size Epson 10000XL. Prior to patient dose verification, basic characteristics of films and scanners were investigated. Patient films were analyzed using FilmQA Pro software, which enables to use the signal from all three colour channels (Red, Green, Blue).ResultsCompared to the red channel evaluation, multichannel evaluation presents better passing rates with regard to local gamma index. As expected, we obtained better results using A3-size scanner compared to A4-size scanner, especially when considering large region of interest. An observation of great interest was made for both scanners: after intensive use, a tilting in the blue transmittance profiles appeared in the lamp direction, making multichannel analysis unsuitable for accurate dose evaluation.     

With Reference to Reference Genes: A Systematic Review of Endogenous Controls in Gene Expression Studies

The choice of reference genes that are stably expressed amongst treatment groups is a crucial step in real-time quantitative PCR gene expression studies. Recent guidelines have specified that a minimum of two validated reference genes should be used for normalisation. However, a quantitative review of the literature showed that the average number of reference genes used across all studies was 1.2. Thus, the vast majority of studies continue to use a single gene, with β-actin (ACTB) and/or glyceraldehyde 3-phosphate dehydrogenase (GAPDH) being commonly selected in studies of vertebrate gene expression. Few studies (15%) tested a panel of potential reference genes for stability of expression before using them to normalise data. Amongst studies specifically testing reference gene stability, few found ACTB or GAPDH to be optimal, whereby these genes were significantly less likely to be chosen when larger panels of potential reference genes were screened. Fewer reference genes were tested for stability in non-model organisms, presumably owing to a dearth of available primers in less well characterised species. Furthermore, the experimental conditions under which real-time quantitative PCR analyses were conducted had a large influence on the choice of reference genes, whereby different studies of rat brain tissue showed different reference genes to be the most stable. These results highlight the importance of validating the choice of normalising reference genes before conducting gene expression studies.     

Perception underground:Review of physical aspects and measurements

A summary is given of the types of signal which might be perceived by the mole in itsunderground life, viz. sound, seismic earth movement or vibration, light, infrared radiation and other electromagnetic disturbances, and odours. Some guidance is provided regarding suitable physical receptors to use in the investigation of these various signals. Satisfactory receptors are available for light, infrared radiation and the other classes of electromagnetic disturbance. For sound, the presently available receptors are of inadequate sensitivity. Seismic earth movements and odours are almost unexplored and their detection at an appropriate level of sensitivity is a suitable subject for future research.     

Extraneous agent detection in vaccines--a review of technical aspects

The quality and safety of commercial vaccines have a profound importance. Contrary to all precautions and efforts the use of biological material in vaccine development and production may lead to potential contamination of the vaccines with known and unknown extraneous agents (EAs). In veterinary field official lists of EAs have been compiled as legal framework to describe the potential agents, which must be tested during manufacture of vaccines. Nevertheless, detection of known and unknown contaminants in vaccines is a common duty for manufacturers and authorities of both veterinary and human field sharing similar needs of special technical approaches. State-of-art molecular methods such as randomly primed PCR combined with massive parallel sequencing (MPS) or microarrays may open new perspectives in extraneous agent testing. The robustness and efficacy of this technical approach in vaccine control was clearly demonstrated on a human vaccine example when porcine circovirus type 1 (PCV1) contamination was revealed in Rotarix, a human rotavirus vaccine. The consequences and implications are reviewed hereby from a veterinary regulatory point of view.     

Metachronous medulloblastoma and glioblastoma: Implications for clinical and technical aspects of re-irradiation

A seven-year-old male underwent surgical resection and chemoradiation for average risk medulloblastoma; twelve years later, the presence of a necrotic and infiltrative mass in the same area and invading the brainstem prompted a subtotal resection. Pathology was indicative of glioblastoma. He was then treated with concurrent temozolomide and using biologically effective dose calculations for gross residual tumor tissue in the brainstem as well as brainstem tolerance, a radiotherapy dose of 3750 cGy was chosen, fractionated in twice-daily fractions of 125 cGy each. The gross tumor volume was expanded with a 5 mm margin to the planning target volume, which was also judiciously subtracted from the normal brainstem. He completed his radiotherapy course with subsequent imaging free of residual tumor and continued adjuvant temozolomide and remains under follow-up surveillance. This case underscores the rarity of metachronous medulloblastoma and glioblastoma, of which only five known cases heretofore have been described. We discuss the technicalities of radiotherapy planning in this patient, including common hurdles for radiation oncologists in similar patients.     

Wax boluses and accuracy of EBT and RTQA radiochromic film detectors in radiotherapy with the JINR Phasotron proton beam

Aim

To present the results obtained using radiochromic films EBT and RTQA 1010P for the reconstruction the dose distributions for targets irradiated by proton beam and modified by wax boluses.

Background

In Medico-Technical Complex at the Joint Institute for Nuclear Research in Dubna implemented technology of wax boluses.

Materials and methods

Wax boluses are easier to make and they give better dose distributions than boluses made from modeling clay previously used at our center. We irradiated two imaginary targets, one shaped as a cylinder and the other one as two cuboids. The evaluated calibration curve was used for calculation of the dose distributions measured by the EBT and RTQA radiochromic film. In both cases, the measured dose distributions were compared to the dose distributions calculated by the treatment planning system (TPS). We also compared dose distributions using three different conformity indices at a 95% isodose.

Results

Better target coverage and better compliance of measurements (semiconductor detectors and radiochromic films) with calculated doses was obtained for cylindrical target than for cuboidal target. The 95% isodose covered well the tumor for both target shapes, while for cuboidal target larger volume around the target received therapeutic dose, due to the complicated target shape. The use wax boluses provided to be effective tool in modifying proton beam to achieve appropriate shape of isodose distribution.

Conclusion

EBT film yielded the best visual matching. Both EBT and RTQA films confirmed good conformity between calculated and measured doses, thus confirming that wax boluses used to modify the proton beam resulted in good dose distributions.     

Development of antibodies to interferon beta in patients: technical and biological aspects.

There are now several papers describing the development of antibodies to interferons (IFN) in patients undergoing IFN therapy. Moreover, there is increasing evidence to indicate that the development of antibodies to IFN may be associated with a failure of the beneficial effects of the therapy. This paper will review and discuss what is currently known about the technical, and biological aspects of antibodies to IFN, with particular reference to antibodies to IFN beta that develop during therapy. Three main considerations arise from the data. Firstly, a standardized quantitative assay to detect antibody to IFN must be agreed upon. Only when results can be compared, both qualitatively and quantitatively, will it be possible to monitor fully the ability of antibodies to cause a relapse during treatment. Secondly, sufficient data are now available to provide a rationale for monitoring the presence of anti-IFN antibodies in patients treated with IFN. This approach may allow a better understanding of the disease reactivation state observed in numerous patients treated with IFN. Finally, approaches aimed at limiting the immunogenicity of IFN preparations and/or strategies designed to circumvent antibody-mediated resistance to IFN treatment are required.