On the use of EBT3 film for relative dosimetry of kilovoltage X ray beams

EBT3 films were evaluated for relative dosimetry in water, in the energy range of therapeutic kV X ray beams. A film batch was calibrated in air for all nine beam qualities of a clinical unit (XStrahl 200). Monte Carlo (MC) simulations using MCNP v.6 facilitated the calculation of the film absorbed dose (f), and beam quality (k_bq) energy dependences in air. Results were found in agreement with corresponding data in the literature. Film samples from the same batch were irradiated in water along the central beam axis for each beam quality. Experimental percentage depth dose (PDD) results obtained using calibration data in air showed quality and depth dependent differences from corresponding MC simulations. These differences increased beyond film dosimetry uncertainty (<3.3%), reaching up to 8% at increased depth. The observed differences reduced only slightly when spectral variation as a function of measurement point was accounted for, using photon effective energy. PDD measurements and corresponding MC results facilitated the determination of f and k_bq in water. Results showed that the origin of the observed differences between experimental and MC PDD results is the difference between film response in air and water, as a result of radiation field perturbation from the film oriented along the central beam axis. This implies a directional dependence of film response which necessitates that the angular distribution of photons impinging on the film is the same in the calibration and measurement geometries.     

An update on the validation of whole slide imaging systems following FDA approval of a system for a routine pathology diagnostic service in the United States

Pathologists have used light microscopes and glass slides to interpret the histologic appearance of normal and diseased tissues for more than 150 years. The quality of both microtomes used to cut tissue sections and microscopes has improved significantly during the past few decades, but the process of rendering diagnoses has changed little. By contrast, major advances in digital technology have occurred since the introduction of hand held electronic devices, including the development of whole slide imaging (WSI) systems with software packages that can convert microscope images into virtual (digital) slides that can be viewed on computer monitors and via the internet. To date, however, these technological developments have had minimal impact on the way pathologists perform their daily work, with the exception of using computers to access electronic medical records and scholarly web sites for pertinent information to assist interpretation of cases. Traditional practice is likely to change significantly during the next decade, especially since the Federal Drug Administration in the USA has approved the first WSI system for routine diagnostic practice. I review here the development and slow acceptance of WSI by pathology departments. I focus on recent advances in validation of WSI systems that is required for routine diagnostic reporting of pathology cases using this technology.     

AGFA Drystar 5500干式相机图像质量控制

在医院集中式DICOM医用打印系统中,一台高速DICOM打印机往往连接着多台DICOM主机。由于各主机对输出图像的质量要求不同,如何在打印机端适应主机的要求,控制打印图像质量,是得到令人满意的胶片输出的医用图像的关键。本文以AGFADrystar5500干式相机为例探讨该DICOM医用打印机的图像控制原理和方法,以及在临床上的实际应用。     

Genetic diversity of Fusarium oxysporum strains from common bean fields in Spain.

Fusarium wilt is an endemic disease in El Barco de Avila (Castilla y León, west-central Spain), where high-quality common bean cultivars have been cultured for the last century. We used intergenic spacer (IGS) region polymorphism of ribosomal DNA, electrophoretic karyotype patterns, and vegetative compatibility and pathogenicity analyses to assess the genetic diversity within Fusarium oxysporum isolates recovered from common bean plants growing in fields around El Barco de Avila. Ninety-six vegetative compatibility groups (VCGs) were found among 128 isolates analyzed; most of these VCGs contained only a single isolate. The strains belonging to pathogenic VCGs and the most abundant nonpathogenic VCGs were further examined for polymorphisms in the IGS region and electrophoretic karyotype patterns. Isolates belonging to the same VCG exhibited the same IGS haplotype and very similar electrophoretic karyotype patterns. These findings are consistent with the hypothesis that VCGs represent clonal lineages that rarely, if ever, reproduce sexually. The F. oxysporum f. sp. phaseoli strains recovered had the same IGS haplotype and similar electrophoretic karyotype patterns, different from those found for F. oxysporum f. sp. phaseoli from the Americas, and were assigned to three new VCGs (VCGs 0166, 0167, and 0168). Based on our results, we do not consider the strains belonging to F. oxysporum f. sp. phaseoli to be a monophyletic group within F. oxysporum, as there is no correlation between pathogenicity and VCG, IGS restriction fragment length polymorphism, or electrophoretic karyotype.     

Genetic Diversity of Fusarium oxysporum Strains from Common Bean Fields in Spain

Fusarium wilt is an endemic disease in El Barco de Avila (Castilla y León, west-central Spain), where high-quality common bean cultivars have been cultured for the last century. We used intergenic spacer (IGS) region polymorphism of ribosomal DNA, electrophoretic karyotype patterns, and vegetative compatibility and pathogenicity analyses to assess the genetic diversity within Fusarium oxysporum isolates recovered from common bean plants growing in fields around El Barco de Avila. Ninety-six vegetative compatibility groups (VCGs) were found among 128 isolates analyzed; most of these VCGs contained only a single isolate. The strains belonging to pathogenic VCGs and the most abundant nonpathogenic VCGs were further examined for polymorphisms in the IGS region and electrophoretic karyotype patterns. Isolates belonging to the same VCG exhibited the same IGS haplotype and very similar electrophoretic karyotype patterns. These findings are consistent with the hypothesis that VCGs represent clonal lineages that rarely, if ever, reproduce sexually. The F. oxysporum f. sp. phaseoli strains recovered had the same IGS haplotype and similar electrophoretic karyotype patterns, different from those found for F. oxysporum f. sp. phaseoli from the Americas, and were assigned to three new VCGs (VCGs 0166, 0167, and 0168). Based on our results, we do not consider the strains belonging to F. oxysporum f. sp. phaseoli to be a monophyletic group within F. oxysporum, as there is no correlation between pathogenicity and VCG, IGS restriction fragment length polymorphism, or electrophoretic karyotype.     

Urea potentiometric enzymatic biosensor based on charged biopolymers and electrodeposited polyaniline

A potentiometric biosensor based on urease was developed for the quantitative determination of urea concentration in aqueous solutions for biomedical applications. The urease was either physisorbed onto an electrodeposited polyaniline film (PANI), or immobilized on a layer-by-layer film (LbL) assembled over the PANI film, that was obtained by the alternate deposition of charged polysaccharides (carboxymethylpullulan (CMP) and chitosan (CHI)). In the latter case, the urease (Urs) enzyme was either physically adsorbed or covalently grafted to the LbL film using carbodiimide coupling reaction. Potentiometric responses of the enzymatic biosensors were measured as a function of the urea concentration in aqueous solutions (from 10(-6) to 10(-1) mol L(-1) urea). Very high sensitivity and short response time were observed for the present biosensor. Moreover, a stability study showed a higher stability over time for the potentiometric response of the sensor with the enzyme-grafted LbL film, testifying for the protective nature of the polysaccharide coating and the interest of covalent grafting.     

The use of Pantherpix pixel detector in radiotherapy QA

There are various different detectors, which can be used for radiotherapy measurements, and more are about to be adopted. Hybrid pixel detectors (HPD) have been originally developed for the high energy physics. However, over the last few years they also expanded in the medical physics. Novel 2D detector Pantherpix is a HPD designed specifically for the radiotherapy. In this article, its properties are characterised and an assessment of its use in radiotherapy photon beams is provided. Properties such as response stability, response linearity, angular dependence and energy dependence were studied. In order to prove sufficient clinical quality for relative dosimetry, further measurements were undertaken (i.e. dose profiles and collimator scatter factors). Acquired results were compared with ion chamber and gafchromic film results. Namely the applicability of PhPix for cobalt beam therapy, which is still widely used (and will be used in near future) in economically less developed countries, is considered.     

Interactive touch-screen monitors facilitate collaborative learning of microscopy skills in an introductory-level plant biology lab

Microscopy skills are critical for many aspects of biology, yet they are notoriously difficult to teach, especially to large classes. We trialled the use of widescreen monitors with touch-screen capability connected to compound microscopes in an introductory-level plant biology lab. Working in teams, students used the screens to interpret, annotate and measure images of their sections taken through fresh leaf material. The lab progressed more rapidly than in previous years in which it was run as a traditional microscopy exercise; it was also far noisier and more congested. Students reported that they valued the size and quality of the images, and the opportunity to work collaboratively to identify the leaf’s structural features. All teams expressed a strong appreciation for the group discussions facilitated by the monitors, which presented a safe environment to bounce ideas off one another, and assisted their comprehension. The monitors were seen as an effective and time-efficient tool for collaborative learning of fundamental microscopy skills.     

Medical images and automated interpretation

The application of automated interpretation to medical images is discussed and the main methods of medical imaging are briefly described. The factors behind the process of human clinical interpretation are also considered. Because human interpretation can be aided by processing of the raw image, the standard methods of image processing are mentioned. Automated interpretation of images in other fields is relevant, and segmentation of images is an important initial part of the process. There are already some applications of automated interpretation of medical images. Some are more complete than others. This will undoubtedly be an important developing field of work which will draw on experience from other areas, and be spurred on by the increasing complexity of medical imaging methods and shortage of expertise for human interpretation.     

Application of Gafchromic EBT2 film for intraoperative radiation therapy quality assurance

PurposeIntraoperative radiation therapy (IORT) using electron beam is commonly done by mobile dedicated linacs that have a variable range of electron energies. This paper focuses on the evaluation of the EBT2 film response in the green and red colour channels for IORT quality assurance (QA).MethodsThe calibration of the EBT2 films was done in two ranges; 0–8 Gy for machine QA by red channel and 8–24 Gy for patient-specific QA by green channel analysis. Irradiation of calibration films and relative dosimetries were performed in a water phantom. To evaluate the accuracy of the film response in relative dosimetry, gamma analysis was used to compare the results of the Monte Carlo simulation and ionometric dosimetry. Ten patients with early stage breast cancer were selected for in-vivo dosimetry using the green channel of the EBT2 film.ResultsThe calibration curves were obtained by linear fitting of the green channel and a third-order polynomial function in the red channel (R2 = 0.99). The total dose uncertainty was up to 4.2% and 4.7% for the red and green channels, respectively. There was a good agreement between the relative dosimetries of films by the red channel, Monte Carlo simulations and ionometric values. The mean dose difference of the in-vivo dosimetry by green channel of this film and the expected values was about 1.98% ± 0.75.ConclusionThe results of this study showed that EBT2 film can be considered as an appropriate tool for machine and patient-specific QA in IORT.     

Intact individual heart cells isolated from human ventricular tissue.

The intricate architecture of heart muscle, comprising irregularly shaped cells which interdigitate in a complex three-dimensional array, has often compromised clear interpretation of experimental data obtained from the whole organ. One approach to minimise some of the difficulties is to use individual muscle cells in suspension, and data have already been reported using myocytes isolated from mammalian ventricles. It is difficult, however, to extrapolate results obtained from animal tissues to situations of medical relevance in man. Intact isolated muscle cells were obtained from human ventricular tissue by modifications of methods used for isolating smooth muscle, atrial, and ventricular tissue from animals. Electrical studies showed that these myocytes had functional characteristics similar to those observed in the whole heart. Such cells will prove a useful preparation for studies on both the mechanisms underlying myocardial performance in normal and diseased states and the response of heart tissue at the cellular level to conditions found during cardiac surgery.     

Preclinical Data on Efficacy of 10 Drug-Radiation Combinations: Evaluations,Concerns, and Recommendations

BACKGROUND: Clinical testing of new therapeutic interventions requires comprehensive, high-quality preclinical data. Concerns regarding quality of preclinical data have been raised in recent reports. This report examines the data on the interaction of 10 drugs with radiation and provides recommendations for improving the quality, reproducibility, and utility of future studies. The drugs were AZD6244, bortezomib, 17-DMAG, erlotinib, gefitinib, lapatinib, oxaliplatin/Lipoxal, sunitinib (Pfizer, Corporate headquarters, New York, NY), thalidomide, and vorinostat. METHODS: In vitro and in vivo data were tabulated from 125 published papers, including methods, radiation and drug doses, schedules of administration, assays, measures of interaction, presentation and interpretation of data, dosimetry, and conclusions. RESULTS: In many instances, the studies contained inadequate or unclear information that would hamper efforts to replicate or intercompare the studies, and that weakened the evidence for designing and conducting clinical trials. The published reports on these drugs showed mixed results on enhancement of radiation response, except for sunitinib, which was ineffective. CONCLUSIONS: There is a need for improved experimental design, execution, and reporting of preclinical testing of agents that are candidates for clinical use in combination with radiation. A checklist is provided for authors and reviewers to ensure that preclinical studies of drug-radiation combinations meet standards of design, execution, and interpretation, and report necessary information to ensure high quality and reproducibility of studies. Improved design, execution, common measures of enhancement, and consistent interpretation of preclinical studies of drug-radiation interactions will provide rational guidance for prioritizing drugs for clinical radiotherapy trials and for the design of such trials.     

Triple channel analysis of Gafchromic EBT3 irradiated with clinical carbon-ion beams

Self-developing radiochromic film is widely used in radiotherapy QA procedures. To compensate for typical film inhomogeneities, the triple channel analysis method is commonly used for photon-irradiated film. We investigated the applicability of this method for Gafchromic^TMEBT3 (Ashland) film irradiated with a clinically used carbon-ion beam. Calibration curves were taken from EBT3 film specimens irradiated with monoenergetic carbon-ion beams of different doses. Measurements of the lateral field shape and homogeneity were performed in the middle of a passively modulated spread-out Bragg peak and compared to simultaneous characterization by means of a 2D ionization chamber array. Additional measurements to investigate the applicability of EBT3 for quality assurance (QA) measurement in carbon-ion beams were performed. The triple-channel analysis reduced the relative standard deviation of the doses in a uniform carbon ion field by 30% (from 1.9% to 1.3%) and reduced the maximum deviation by almost a factor of 3 (from 28.6% to 9.8%), demonstrating the elimination of film artifacts. The corrected film signal showed considerably improved image quality and quantitative agreement with the ionization chamber data, thus providing a clear rationale for the usage of the triple channel analysis in carbon-beam QA.     

Using a CCD camera imaging system as a recording device to quantify human DNA by slot blot hybridization

Slot blot hybridization of membrane-immobilized, single-stranded human DNA with the higher primate-specific alphoid probe D17Z1 is routinely used in forensic science to estimate the amount of DNA in biological samples. Typically, a chemiluminescent signal captured on film records the hybridization, and the quantity of the signal is related to the amount of immobilized DNA. Digital imaging using a cooled CCD camera offers an alternate non-film-based method for image acquisition with comparable sensitivity of detection, a greater dynamic range, enhanced capability of data interpretation, and often faster results than film. In addition, the data support the premise that more accurate and precise human DNA quantification should be obtained by not assuming a linear response of signal to known standards. Instead, quantity should be estimated using a second-order standard curve (R2 = 0.999). Finally, a CCD camera imaging system offers versatility for image capture of different signal sources and analysis of samples on a variety of support media.     

Structurally colored thiol chitosan thin films as a platform for aqueous heavy metal ion detection

Thin films of the polysaccharide chitosan and several chitosan derivatives, including conjugates of l-cysteine, thioglycolic acid, and 2-iminothiolane, were produced from dilute acidic solutions. Attempts to produce a fourth conjugate using lipoic acid resulted in the synthesis of partially N-acetylated chitosan ethanoate. These biopolymer films were exposed to solutions containing 50 ppm concentrations of various metal ion and counterion analytes. Analyte-induced changes in film thicknesses and refractive indices were measured using a spectroscopic ellipsometer, and shifts in film color were quantified using a reflectance spectrometer. The modified chitosans were generally more sensitive to change in response to pure water but also showed varied response to several ions of interest, including Cr(III) and Cr(VI), Hg(II), Ni(II), and others. The potential for tuning film response was demonstrated by varying the concentration of sulfur groups in the thioglycolic acid conjugate, leading to increased specificity for Hg(II).     

Culturing neuron cells on electrode with self-assembly monolayer

The success of neuronal implantable microsystems relies on the quality of the interface with neuronal cells. Depending on the application, specifically engineered surfaces may either prevent or enhance cell/tissue growth with an appropriate host response. The surface chemistry and topography have major effects on the cell adherence and the interaction between the tissue and devices. We report on a simple technique to precisely explant cortical neurons in a serum-free medium on 2D electrode arrays and investigated the pad size effect on neuron cell culture and immobilization. We produced gold patterns on glass substrates using microfabrication processes. 11-Amino-1-undecanethiol self-assembled monolayer was coated only on the gold surface. Cortical neurons were cultured on the arrays to examine the dependence of neuron growth and cells distribution on pad size. We found that the terminal functional groups of the highly oriented 11-amino-1-undecanethiol thin film are essential for generating cell-adhesive areas for the rat cortical neurons. A 50 microm x 50 microm SAM pad size was found to be suitable for single cortical neuron immobilization, while the larger pads provide excellent neuron coverage. This technology may enable precise and localized neuron stimulation and surveillance for both biological research and medical applications.     

不同光质对烟草叶片组织结构及Rubisco羧化酶活性和rbc、rca基因表达的影响

通过对烟草植株覆盖白、红、黄、蓝、紫色滤膜获得不同光质,研究了烟草叶片在7～70d的生长发育期内,不同光质处理对烟叶组织结构特征、核酮糖1,5-二磷酸羧化酶/加氧酶（Rubisco）羧化酶活性、Rubisco基因（rbc）表达及其活化酶（Rca）基因（rca）表达的影响。结果表明,与黄膜处理下生长的烟叶相比,红、蓝、紫膜处理下生长的烟叶有较高的叶片厚度、栅栏组织厚度、海绵组织厚度、栅栏细胞密度和较小的组织空隙率。此外,红、蓝、紫膜处理的叶片有较高的Rubis-co羧化酶活性和净光合速率及较强的rbc和rca基因表达。实验结果表明不同光质对烟草叶片的组织结构特征有显著影响,光质可能通过影响Rubisco羧化酶活性进而影响叶片光合效率,而光质、叶片组织结构和光合效率之间存在某种程度的相互联系。     

PACS辅助教学在医学影像学实习教学中的应用探讨

尝试应用影像存储及传输系统(Picture Archiving and Communication System,PACS),对我院临床本科生进行影像学实习教学。首先应用PACS建立电子影像学图片库,学生在PACS联网的计算机上学习教学内容,通过定期随堂测验、期末考试和课后问卷调查评估PACS辅助教学的教学效果,对PACS辅助教学在医学影像学实习教学中的应用价值进行探讨。与以往传统医学影像学实习教学方法相比,PACS辅助教学在医学影像学实习教学中具有激发学生学习主动性、提高学习效率和学生读片能力的优越性,显著提高教学效果和教学质量,对促进医学影像学教学改革具有重要意义。     

Automated biomonitors — first line of defense

Automated biomonitors operate on a real-time basis and utilize living organisms as the sensors. Traditionally, chemical monitors have been used to assess water quality. However, biological monitors respond to a greater number of toxic conditions. An overview of the various automated biomonitors, assessed by the types of biological sensors employed, is presented. The sensors used include bacteria, algae, invertebrates, and fish. Of all the systems, those monitoring the ventilatory behavior of fish have evolved the furthest with respect to their research, development, commercial availability, and field testing.     

不同光质对烟草叶片生长及光合作用的影响

通过对烟草植株覆盖白、红、黄、蓝、紫色滤膜获得不同光质,研究了光质对烟叶生长及光合作用的影响。结果表明,与白膜处理相比,红膜与蓝膜处理下的烟草叶片较厚,比叶面积较小,叶绿素a/b比值、净光合速率、可变荧光强度（Fv）和最大荧光强度（Fm）的比值Fv/Fm（PSⅡ最大光化学量子效率）、PSⅡ实际光化学量子效率（ΦPSⅡ）、光饱和点和CO2饱和点均较高。黄膜处理下的叶片较白膜处理的更薄,净光合速率、Fv/Fm、ΦPSⅡ、光饱和点、CO2饱和点均较低。紫膜处理的叶片比叶面积比白膜处理的小,净光合速率和Fv/Fm比白膜的大。实验结果表明红光、蓝光和紫光促进了烟叶的生长,这种促进作用是与其高光合效率紧密相连的;而黄光对烟叶的生长有一定程度的抑制作用。