Drivers, challenges and opportunities of forage technology adoption by smallholder cattle households in Cambodia.

Forage technology has been successfully introduced into smallholder cattle systems in Cambodia as an alternative feed source to the traditional rice straw and native pastures, improving animal nutrition and reducing labour requirements of feeding cattle. Previous research has highlighted the positive impacts of forage technology including improved growth rates of cattle and household time savings. However, further research is required to understand the drivers, challenges and opportunities of forage technology for smallholder cattle households in Cambodia to facilitate widespread adoption and identify areas for further improvement. A survey of forage-growing households (n = 40) in July-September 2016 examined forage technology adoption experiences, including reasons for forage establishment, use of inputs and labour requirements of forage plot maintenance and use of forages (feeding, fattening, sale of grass or seedlings and silage). Time savings was reported as the main driver of forage adoption with household members spending approximately 1 h per day maintaining forages and feeding it to cattle. Water availability was reported as the main challenge to this activity. A small number of households also reported lack of labour, lack of fencing, competition from natural grasses, cost of irrigation and lack of experience as challenges to forage growing. Cattle fattening and sale of cut forage grass and seedlings was not found to be a widespread activity by interviewed households, with 25 and 10% of households reporting use of forages for these activities, respectively. Currently, opportunities exist for these households to better utilise forages through expansion of forage plots and cattle activities, although assistance is required to support these households in addressing current constraints, particularly availability of water, if the sustainability of this feed technology for smallholder cattle household is to be established in Cambodia.

Aromatase inhibitor-induced modulation of breast density: clinical and genetic effects.

BACKGROUND: Change in breast density may predict outcome of women receiving adjuvant hormone therapy for breast cancer. We performed a prospective clinical trial to evaluate the impact of inherited variants in genes involved in oestrogen metabolism and signalling on change in mammographic percent density (MPD) with aromatase inhibitor (AI) therapy. METHODS: Postmenopausal women with breast cancer who were initiating adjuvant AI therapy were enrolled onto a multicentre, randomised clinical trial of exemestane vs letrozole, designed to identify associations between AI-induced change in MPD and single-nucleotide polymorphisms in candidate genes. Subjects underwent unilateral craniocaudal mammography before and following 24 months of treatment. RESULTS: Of the 503 enrolled subjects, 259 had both paired mammograms at baseline and following 24 months of treatment and evaluable DNA. We observed a statistically significant decrease in mean MPD from 17.1 to 15.1% (P<0.001), more pronounced in women with baseline MPD ≥20%. No AI-specific difference in change in MPD was identified. No significant associations between change in MPD and inherited genetic variants were observed. CONCLUSION: Subjects with higher baseline MPD had a greater average decrease in MPD with AI therapy. There does not appear to be a substantial effect of inherited variants in biologically selected candidate genes.

Standardization in Quantitative Imaging: A Multicenter Comparison of Radiomic Features from Different Software Packages on Digital Reference Objects and Patient Data Sets.

Radiomic features are being increasingly studied for clinical applications. We aimed to assess the agreement among radiomic features when computed by several groups by using different software packages under very tightly controlled conditions, which included standardized feature definitions and common image data sets. Ten sites (9 from the NCI's Quantitative Imaging Network] positron emission tomography-computed tomography working group plus one site from outside that group) participated in this project. Nine common quantitative imaging features were selected for comparison including features that describe morphology, intensity, shape, and texture. The common image data sets were: three 3D digital reference objects (DROs) and 10 patient image scans from the Lung Image Database Consortium data set using a specific lesion in each scan. Each object (DRO or lesion) was accompanied by an already-defined volume of interest, from which the features were calculated. Feature values for each object (DRO or lesion) were reported. The coefficient of variation (CV), expressed as a percentage, was calculated across software packages for each feature on each object. Thirteen sets of results were obtained for the DROs and patient data sets. Five of the 9 features showed excellent agreement with CV < 1%; 1 feature had moderate agreement (CV < 10%), and 3 features had larger variations (CV ≥ 10%) even after attempts at harmonization of feature calculations. This work highlights the value of feature definition standardization as well as the need to further clarify definitions for some features.

Polymer planar waveguide device using inverted channel structure with upper liquid crystal cladding.

We propose a composite waveguide configuration based on an inverted polymer channel structure with upper nematic liquid crystal cladding. This configuration can achieve a more homogenous liquid crystal molecular alignment between the core and the liquid crystal material by minimizing the rubbing damage during preparation of the alignment layer. We demonstrated our idea with a variable optical attenuator which exhibited a 24 dB of attenuation range over a tuning peak voltage of 10 V at 1550 nm.

Chondrodermatitis nodularis chronica helicis in monozygotic twins.

Chondrodermatitis nodularis chronica helicis (CNCH) is a benign inflammatory nodule of the helix. Patients report severe tenderness upon pressure. Commonly seen in middle-aged men, there are no reports of this disease in twins. We report middle-aged male monozygotic twins who simultaneously developed CNCH. This suggests, but does not prove, the possibility of a hereditary factor in the pathogenesis of CNCH.

Skin decontamination of glyphosate from human skin in vitro.

This study compared three model decontaminant solutions (tap water, isotonic saline, and hypertonic saline) for their ability to remove a model herbicide (glyphosate) from an in vitro human skin model. Human cadaver skin was dosed (approximately 375microg) of [14C]-glyphosate on 3cm2 per skin. After each exposure time (1, 3, and 30min post-dosing, respectively), the surface skin was washed three times (4ml per time) with each solution. After washing, the skin was stripped twice with tape discs. Lastly, the wash solutions, strippings, receptor fluid, and remainder of skin were liquid scintillation analyzer counted to determine the amount of glyphosate. There were no statistical differences among these groups at any time points. The total mass balance recovery at three time exposure points was between 94.8% and 102.4%. The wash off rates (glyphosate in wash solutions) at three different exposure times is 79-101.2%. Thus the three tested decontaminants possess similar effectiveness in removing glyphosate from skin. This in vitro model is not only economic and rapid, but also provides quantitative data that may aid screening for optimal decontaminants.

Evaluation of a parallel hole grid for bedside chest imaging.

RATIONALE AND OBJECTIVES: The application of a new parallel hole grid designed for bedside radiography is investigated. This grid is constructed of sheets of holes and is designed to have more tolerance to positioning errors than conventional grids. METHODS: The parallel hole grid is compared to conventional 6:1 and 12:1 grids using phantoms. The contrast improvement, scatter fractions, exposure, and tolerance to positioning errors are measured. RESULTS: The parallel hole grid has much more tolerance to positioning errors than conventional grids. The contrast improvement and scatter rejection are significantly less than those obtained with a conventional 6:1 ratio grid. Compared with nongrid techniques, the parallel hole grid provides 13% to 20% higher lung contrast. CONCLUSIONS: The parallel hole grid may be used for bedside imaging without the need for accurate alignment. The parallel hole grid requires approximately 2.7 times the entrance exposure of a nongrid technique. Lung contrast improvement is approximately half of that from an accurately aligned 6:1 conventional grid. For grid angulation greater than 8 degrees, the parallel hole grid provides higher contrast than the 6:1 grid.

Automated tracking and computer reproduction of vessels in DSA images.

We are developing an automated vessel-tracking method based on the double-square-box region-of-search technique, for efficient tracking of the connected vascular tree in a digital subtraction angiography (DSA) image. Tracking points and branch vessels are located by searching of the perimeter of boxes, which are centered on previously determined tracking points. The most accurate results (90% true-positive rate with six false-positives per image) are obtained by tracking using the double-square-box method. In relatively straight regions of vessels, a large box is employed for efficient tracking; in curved regions of vessels, a small box is employed to ensure accurate tracking. When tracking is completed, accurate vessel information, ie, the vessel position, size, and contrast determined at each tracking point, is available for further quantitative analysis. Computer reproductions of tracked vessel trees appear to correspond well to those in DSA images.

Digital mammography. ROC studies of the effects of pixel size and unsharp-mask filtering on the detection of subtle microcalcifications.

We investigated the spatial resolution requirement and the effect of unsharp-mask filtering on the detectability of subtle microcalcifications in digital mammography. Digital images were obtained by digitizing conventional screen-film mammograms with a 0.1 X 0.1 mm2 pixel size, processed with unsharp masking, and then reconstituted on film with a Fuji image processing/simulation system (Fuji Photo Film Co., Tokyo, Japan). Twenty normal cases and 12 cases with subtle microcalcifications were included. Observer performance experiments were conducted to assess the detectability of subtle microcalcifications in the conventional, the unprocessed digital, and the unsharp-masked mammograms. The observer response data were evaluated using receiver operating characteristic (ROC) and LROC (ROC with localization) analyses. Our results indicate that digital mammograms obtained with 0.1 X 0.1 mm2 pixels provide lower detectability than the conventional screen-film mammograms. The detectability of microcalcifications in the digital mammograms is improved by unsharp-mask filtering; the processed mammograms still provide lower accuracy than the conventional mammograms, however, chiefly because of increased false-positive detection rates for the processed images at each subjective confidence level. Viewing unprocessed digital and unsharp-masked images in pairs resulted in approximately the same detectability as that obtained with the unsharp-masked images alone. However, this result may be influenced by the fact that the same limited viewing time was necessarily divided between the two images.

Computer-aided detection of microcalcifications in mammograms. Methodology and preliminary clinical study.

The authors investigated the feasibility of using computer methods for automated detection of clustered microcalcifications on clinical mammograms. A new difference-image approach using a matched filter/box-rim filter combination effectively removed the structured background from the image. A locally adaptive gray-level thresholding technique was then used for extraction of the signals from the resulting difference image. Signal-extraction criteria based on the size, contrast, number, and clustering properties of microcalcifications were next imposed on the detected signals to distinguish true signals from noise or artifacts. The detection accuracy of the computer scheme was evaluated by means of a free response receiver operating characteristic (FROC) analysis. It was found that, for simulated subtle microcalcifications superimposed on normal mammograms, the difference-image approach with a matched filter/box-rim filter combination could yield a true-positive cluster detection rate of 80% at a false-positive detection rate of one cluster per image. In a study of 20 clinical images containing moderately subtle microcalcifications, the automated computer scheme obtained an 82% true-positive cluster detection rate at a false-positive detection rate of one cluster per image. These results indicate that the automated method has the potential to aid radiologists in screening mammograms for clustered microcalcifications.

Dynamic digital subtraction evaluation of regional pulmonary ventilation with nonradioactive xenon.

A method of evaluating pulmonary ventilation with a 57-cm image intensifier/television (II/TV) digital chest system is reported. With this method, the patient inhales a mixture of xenon and oxygen gases while dynamic imaging of the chest is done. Images of the airways and ventilated portions of the lungs are obtained by subtraction of images acquired before and after the xenon-oxygen mixture is administered. The feasibility of the method was evaluated by studies with xenon-filled tubes, an airway phantom, and a ventilation phantom. The results indicate that tubes larger than 3.2 mm in diameter are detectable at a xenon concentration of 41%, and that gas flow and flow distribution can be examined after image subtraction. If background subtraction is incomplete because of motion, the visibility of small airways is reduced greatly, although unventilated regions can still be delineated. The initial evaluation of this technique included imaging a healthy volunteer during xenon inhalation.

Basic imaging properties of a large image intensifier-TV digital chest radiographic system.

The basic imaging properties of a large (57 cm) image intensifier (I.I.)-TV digital imaging system were examined to determine the effects of various physical parameters on the quality of the digital chest images obtained, and also to explore the clinical usefulness of the system. The characteristic curve of the digital system, which relates the output pixel value to the input relative x-ray intensity, was measured with an aluminum stepwedge. MTFs were determined using slit images, and the veiling-glare fraction was measured with a lead-disk technique. Noise Wiener spectra were obtained from uniformly exposed images. The current limitations of the large II-TV digital chest system are its low spatial resolution, and the presence of large amounts of veiling glare and structure mottle. Advantages of this system over other digital chest imaging systems include the high speed of image data acquisition and the capability of "real-time" dynamic imaging of the chest at a radiation dose comparable to that in conventional radiography of the chest.

Improvement in radiologists' detection of clustered microcalcifications on mammograms. The potential of computer-aided diagnosis.

Relatively simple, but important, detection tasks in radiology are nearing accessibility to computer-aided diagnostic (CAD) methods. The authors have studied one such task, the detection of clustered microcalcifications on mammograms, to determine whether CAD can improve radiologists' performance under controlled but generally realistic circumstances. The results of their receiver operating characteristic (ROC) study show that CAD, as implemented by their computer code in its present state of development, does significantly improve radiologists' accuracy in detecting clustered microcalcifications under conditions that simulate the rapid interpretation of screening mammograms. The results suggest also that a reduction in the computer's false-positive rate will further improve radiologists' diagnostic accuracy, although the improvement falls short of statistical significance in this study.

Investigation of energy responses of germanium detectors and correction of measured spectra by means of Monte Carlo simulation.

A Monte Carlo program was developed which determines the energy response of X-ray detectors of various "nested" sizes simultaneously. Twenty-one planar germanium detectors with cylindrical crystals were chosen, which are commercially available for X-ray spectrometry. The photopeak efficiency, K alpha and K beta escape fractions. Compton fraction, elastic fraction, penetration fraction, and the Compton continuum were tabulated as a function of incident X-ray energies from 12 to 300 keV in 2-keV increments. Coefficients of polynomials fitted to the Compton continua were also calculated to facilitate computer implementation of spectrum corrections. Spectrum correction methods which use the Compton continua determined by Monte Carlo calculation were compared with those approximated by rectangles. Comparison of the residual root-mean-square (RRMS) values between the incident and corrected spectra showed that the former method yielded lower RRMS values. However, the differences in these values are small, indicating that the simple rectangular approximation may be adequate for most spectral measurements.

Some properties of photon scattering in water phantoms in diagnostic radiology.

Monte Carlo simulation was applied to study the histories of photon interactions in a soft-tissue-equivalent medium under diagnostic imaging conditions. We examined the dependence on incident x-ray energy and phantom thickness of the basic properties of photon scattering, including the probabilities of occurrence of the various interaction processes, and the frequency distributions of scattering events. We investigated the properties of scattered radiation for monoenergetic incident x rays, which provide a basis for deriving the physical properties of scattered radiation for any polyenergetic incident beam. We also included four incident x-ray beams with broad spectra; these represented the incident x rays typically used for diagnostic imaging.

Determination of radiographic screen-film system characteristic curve and its gradient by use of a curve-smoothing technique.

One of the important factors affecting radiographic image quality is the film contrast of the recording system, which may be expressed by the gradient of its H & D curve. Experimental determinations of H & D curves are subject to relatively small error, which can nevertheless cause large fluctuations and uncertainties in the calculated gradient. To reduce this fluctuation, we wrote a computer program for orthogonal-polynomial (discrete Legendre polynomials) curve fitting by means of least-squares estimation of parameters. This procedure facilitates curve smoothing and gradient computation following sensitometric measurements. The program was tested against a large number of measured characteristic curves. A brief description of the program is given, with examples which illustrate its applications.

Studies of x-ray energy absorption and quantum noise properties of x-ray screens by use of Monte Carlo simulation.

The imaging properties of the phosphor layer in fluorescent screens or image intensifiers are related to its x-ray absorption characteristics. In this study, we applied Monte Carlo methods for the simulation of x-ray photon diffusion in a phosphor layer. The K-reabsorption factor, absorbed x-ray energy, quantum absorption efficiency, statistical factor, and noise-equivalent absorption were determined as a function of the incident energy and angle of the x rays for eight commonly used phosphor layers. These basic physical quantities will be useful for the prediction of the information transfer properties of a phosphor layer.

Radiation dose in diagnostic radiology: Monte Carlo simulation studies.

We applied Monte Carlo calculations to determine the radiation dose absorbed in water phantoms. Monoenergetic incident x-ray beams with energies from 15 to 100 keV and phantom thicknesses from 5 to 20 cm were considered in this study. We calculated the spatial distributions of energy absorption in the phantom, the rad/R conversion factors, the average rad/R conversion factors, and the scatter-to-primary ratios of absorbed dose. We also compared the relative absorbed doses under various imaging conditions when the transmitted radiation produced a given optical density on radiographic film. The information provided will be useful for the estimation of radiation doses in various radiographic procedures.

Effects of x-ray beam equalization on mammographic imaging.

We employed an elastic reservoir filled with tissue-equivalent fluid as an x-ray beam filter for exposure equalization. The filter is designed to be placed between the upper compression plate and the breast. During compression, it will conform to the shape of the peripheral region of the breast and fill the space between the upper and lower compression plates, thereby reducing the variation in x-ray penetration between the thick and thin regions of the breast and compressing the dynamic range of the breast image. Results of a phantom study showed that the visibility of low-contrast features was improved in the peripheral region of the equalized breast phantom image. Experimental measurements indicated that the filter reduced scattered radiation in the peripheral region. This result was confirmed by a Monte Carlo simulation study. The radiation contrast, with the effect of beam hardening included, was also improved when equalization was employed.

Physical characteristics of scattered radiation in diagnostic radiology: Monte Carlo simulation studies.

We applied Monte Carlo methods for the simulation of x-ray scattering in water phantoms. The phantom thickness was varied from 5 to 20 cm, and the monoenergetic incident x rays were varied from 15 to 100 keV. Eight screen pairs and a total absorption system were used as x-ray receptors. We determined the angular, spectral, and spatial distributions of the scattered radiation and the scatter fractions recorded in the image plane. The dependence of these properties on the incident x-ray energy, the phantom thickness, and the energy response of the recording system was examined. The results of this study provide useful information for the development of antiscatter techniques and for the evaluation of radiographic procedures.