Technique Of Microradiography Research Articles

Effect of fluoride, chlorhexidine or Nd:YAG on the progression of root dentin demineralization after removal of the demineralized organic matrix.

Quantification of collagen degradation is an important parameter to evaluate dentin caries for preventive aid.Objectives:Evaluate preventive methods against root collagen degradation by the hydroxyproline assay (HYP) and microradiography technique (MRT).Methodology:Five bovine root dentin blocks were obtained and subjected to an artificial demineralization process by acetate buffer (pH 5) to induce carious lesion formation. Samples were subjected to the following therapeutic treatments: 1) 0.12% chlorhexidine for 1 min, 2) 2% fluoride for 1 min, 3) Nd:YAG Laser (400 μm diameter optical fiber, 10 Hz frequency, 60 mJ/pulse energy, 48 J/cm2 energy density, in noncontact mode for 10 s), 4) deionized water (control) for 1 min, 5) MRT control group (without treatment and removal of collagen). Samples were exposed to degradation by a collagenase enzyme for five days. The enzyme solution was collected, by colorimetry in a spectrophotometer, from the collagen matrix for the hydroxyproline release analysis. The same samples were subjected to an additional two days of demineralization to induce the progression of mineral loss. Samples were analyzed by MRT for the visualization of their degraded areas (estimation of lesion depth and mineral loss). ANOVA was applied to compare hydroxyproline release rates. MRT data were subjected to the Kruskal-Wallis test, followed by the Dunn’s test. Comparisons between the initial five-day and the subsequent two-day demineralization processes were performed by repeated t-test or Wilcoxon (p<0.05) measurements.Results:The amount of HYP released from the dentin samples failed to show significant differences among the groups (p=0.09). Fluoride and chlorhexidine were able to interact with the samples, reducing the progression of dentin caries after removal of the demineralized organic matrix. CHX was the only treatment able to show significant lower lesion depth than the negative control.Conclusion:Chlorhexidine and fluoride were effective in reducing root caries progression.

Real time investigation of the grain refinement dynamics in zinc alloy by synchrotron microradiography

The grain refining performance of titanium diboride particles in zinc alloy was investigated by adding in␣situ formed Al–TiB2 master alloy into ZA27 alloy. The results showed that TiB2 particles could significantly refine the structure of ZA27. After adding 1.1% TiB2, the average grain size decreased markedly from 205.4μm to 65.8μm. To characterize the mechanism by which TiB2 refines the grain size, synchrotron microradiography technique was used for the first time to investigate the effect of TiB2 on the grain nucleation and growth kinetics. Real-time observations revealed that TiB2 particles refine ZA27 by facilitating heterogeneous nucleation, enhancing dendrite fragmentation and constraining the dendrite growth.

In situ study on solidification controlled by electric current pulse in Al-Bi immiscible alloy via synchrotron radiation imaging technology

The Bi-rich droplets motion in a solidifying Al-Bi immiscible alloy was in situ investigated using a synchrotron microradiography technique. The electric current pulse (ECP) was applied to control the droplets motion and distribution in the Al-matrix during solidification. Without ECP treatment, it was found that the second phase presented spherical droplets and distributed in the Al-matrix without obvious aggregation and segregation. With ECP treatment, the second phase seriously aggregated and formed lots of big clusters in the matrix. The electromagnetic pinch force induced by ECP was used to explain this phenomenon.

Real-Time Observation on Evolution of Droplets Morphology Affected by Electric Current Pulse in Al-Bi Immiscible Alloy

The evolution of Bi-rich droplets morphology in a solidifying Al-Bi immiscible alloy was directly observed using a synchrotron microradiography technique. The electric current pulse (ECP) was applied to control the solidification process of Al-Bi immiscible alloy. It was found that the electromagnetic pinch force and Marangoni force induced by ECP and temperature gradient, respectively, can significantly affect the distribution of Bi-rich droplets. The electromagnetic pinch force drove the droplets from the center to side; meanwhile, the Marangoni force lifted the droplets from the bottom to the top. As a result, the droplets finally distributed with a manner of “inverted triangle.”

In situ study on secondary dendrite arm coarsening of Sn–Bi alloy by synchrotron microradiography

Synchrotron microradiography technique was applied in situ to observe the evolution of dendrite morphology of Sn–Bi alloy during solidification at controlled cooling rates. It is shown by in situ observations that different coarsening mechanisms of secondary dendrite arm might operate under different cooling conditions or solidification stages. Coarsening mainly occurred in the early solidification stage due to the competition of secondary dendrite arms, and therefore, secondary dendrite arm spacing is mainly determined in this stage. Coalescence was the dominant coarsening mechanism in the late solidification stage. In particular, at lower cooling rate, e.g. 1·5 K min−1, dendrite fragmentation frequently occurred, and played an important role in dendrite coarsening. The real time observations in real alloy provide verification of the dendrite arm coarsening models.

Detection of lead in Zea mays by dual‐energy X‐ray microtomography at the SYRMEP beamline of the ELETTRA synchrotron and by atomic absorption spectroscopy

This study is related to the application of the X-ray dual-energy microradiography technique together with the atomic absorption spectroscopy (AAS) for the detection of lead on Zea mays stem, ear, root, and leaf samples. To highlight the places with lead intake, the planar radiographs taken with monochromatic X-ray radiation in absorption regime with photon energy below and above the absorption edge of a given chemical element, respectively, are analyzed and processed. To recognize the biological structures involved in the intake, the dual-energy images with the lead signal have been compared with the optical images of the same Z. mays stem. The ear, stem, root, and leaf samples have also been analyzed with the AAS technique to measure the exact amount of the hyperaccumulated lead. The AAS measurement revealed that the highest intake occurred in the roots while the lowest in the maize ears and in the leaf. It seems there is a particular mechanism that protects the seeds and the leaves in the intake process.

X‐ray microscopy of plant cells by using LiF crystal as a detector

A lithium fluoride (LiF) crystal has been utilized as a new soft X-ray detector to image different biological samples at a high spatial resolution. This new type of image detector for X-ray microscopy has many interesting properties: high resolution (nanometer scale), permanent storage of images, the ability to clear the image and reuse the LiF crystal, and high contrast with greater dynamic range. Cells of the unicellular green algae Chlamydomonas dysosmos and Chlorella sorokiniana, and pollen grains of Olea europea have been used as biological materials for imaging. The biological samples were imaged on LiF crystals by using the soft X-ray contact microscopy and contact micro-radiography techniques. The laser plasma soft X-ray source was generated using a Nd:YAG/Glass laser focused on a solid target. The X-ray energy range for image acquisition was in the water-window spectral range for single shot contact microscopy of very thin biological samples (single cells) and around 1 keV for multishots microradiography. The main aim of this article is to highlight the possibility of using a LiF crystal as a detector for the biological imaging using soft X-ray radiation and to demonstrate its ability to visualize the microstructure within living cells.

Real-time observation of dendrite coarsening in Sn-13%Bi alloy by synchrotron microradiography

An improved synchrotron microradiography technique is being used to study dendrite growth and coarsening in Sn-13%Bi alloy in real time. The morphology of growing dendrites can be well resolved with reasonable image contrast. Dendrite arm remelting, coalescence, and fragmentation have been observed in a real alloy and in real time during solidification under controlled thermal gradients and cooling rates. This research opens a different window to the study of alloy solidification and enables unambiguous understanding of solidification processes in optically opaque, metallic alloys.

Assessment of bone mineral content from 3-D synchrotron radiation microtomography images

Synchrotron radiation /spl mu/CT (SR /spl mu/CT) may provide three-dimensional (3-D) images with spatial resolution as high as 1 /spl mu/m. The SR /spl mu/CT system developed at the European Synchrotron Radiation Facility was already used to quantify trabecular bone architecture in bone samples. Here, the authors propose for the first time to use SR /spl mu/CT to assess the mineral content in bones. This quantification is possible thanks to the monochromaticity and high photon flux of the X-ray beam extracted from synchrotron radiation. For this purpose, the authors relate the reconstructed gray levels of the images to a degree of mineralization in bone. They propose a calibration method to estimate the 3-D distribution of hydroxyapatite concentrations within the sample. This method is compared to a reference microradiography technique. Finally, the authors illustrate the possibilities of the method on 3-D images of human biopsies from osteoporotic patients before and after a treatment with bisphosphonates.

Structure and Per‐rectal Ultrasonography of Prostatic Disease using Cadaver Specimens

One hundred cadaver prostates were examined by per-rectal ultrasound and the findings correlated with the microradiographic and histopathological features of whole sections taken at the levels of scanning. The normal gland consists of both periurethral muscle and glands. The periurethral muscle has little structure on microradiography and is therefore hypoechoic (low amplitude echoes) on ultrasound scanning. The gland itself, both central and peripheral zones, has a lattice appearance on microradiography (reticular structure) and therefore produces mid-range amplitude echoes on ultrasound. Benign hypertrophy develops at the edge of the periurethral muscle and is microadenomatous in structure. This produces mid-range amplitude echoes which are coarser than in the normal gland. Associated calcification has a characteristic distribution around the adenomas. Cancer produces an amorphous structure resulting in loss of ultrasonic echoes (hypoechoic). In a few cancers irregular calcification is present, resulting in high echoes in the ultrasound scan (hyperechoic) which are not in the typical benign distribution. The internal structure of the prostate was therefore demonstrated in its histopathological states by the technique of microradiography and seen to relate to its representation by ultrasound.

THE FEASIBILITY OF HEAVY CHARGED‐PARTICLE MICROSCOPY*

The idea of applying accelerated heavy ions to microscopy was developed and proposed about ten years ago. The advancement of heavy-ion accelerator technology has promoted development of a new imaging system for diagnostic radiology. The plastic nuclear track-etch detector technique has recently been used for microradiography with low-energy heavy ions, and images of various biological specimens, including living plant cells, have been obtained. A simple and straightforward theoretical analysis indicates that a resolution of a few hundred angstroms may be reached in imaging a living cell with heavy particles of 10-..mu..m range. At present, however, such a high resolution is not expected, since the radiation damages to the specimen can be very severe at high doses. With certain improvement the present heavy-ion microradiography technique, nevertheless, can be used for gaining information on the density of organelles in a living cell and for obtaining a three-dimensional image of a living cell. A preliminary study on contrast mechanisms suggests that the heavy-ion microscope may give an equal or better contrast than the electron microscope. Other possible means of getting information with heavy-ion microscopes should be explored also. An energy or range analysis of heavy particles that passed through the biological specimen withmore » a proper detector, for example can provide additional information of interest.« less

Correlations of microradiographic and histological findings in the pulmonary vascular bed. Technique and application in pulmonary hypertension.

Obstruction within pulmonary arteries is a well-known cause of pulmonary hypertension in patients with congenital heart disease, but dilatation of the pulmonary vessels is less well understood. The present report has shown that the technique of microradiography is well suited to the study of dilation of the pulmonary microcirculation because (1) vessels as small as capillaries are resolved, (2) whole capillary networks are seen in relation to the arteries feeding them and to the alveoli, and (3) the radiographed tissue may [See Figure in the PDF File] then be sectioned and stained for direct comparison of the histological and microradiographic aspects. The present study demonstrated the technique in a case of normal lungs, one of pulmonary hypertension and a high pulmonary blood flow, and in one of pulmonary hypertension and high pulmonary vascular resistance. Dilated capillaries were demonstrated in both patients with pulmonary hypertension. Greater distortion of the microvascular pattern was seen in the patient with high vascular resistance. Correlation of radiographic and histological examination provides an additional tool for study of the normal and abnormal pulmonary circulation.

A new theory on the formation of renal calculi.

SUMMARY 1. This paper presents a new theory on the formation and growth of urinary calculi based on the lymphatic drainage of the kidney which is described. 2. The material and methods which have been used in studying the formation of renal calculi have been described in detail. These include the technique of microradiography. 3. The current theories of stone formation from the smallest crystalline deposits are reviewed. 4. Observations have been made which are not explained by Randall's theory. 5. By the new theory all the observed facts, including the formation of Randall's plaques, can be explained. 6. Diffraction X-ray analysis has been used to support this new theory. 7. Facts of importance in partial nephrectomy in the treatment of renal lithiasis are emphasised and explained.

The Technique of Microradiography

Investigations have been made of the various factors considered to influence the sensitivity of the microradiographic method for the examination of alloys. Both target element and applied voltage influenced the results. Radiographs are shown to demonstrate the effect; an explanation is given in terms of the x-ray emission curves and the absorption differential curves for the phases of the radiographed alloy. Target-specimen distance was an important factor for uncollimated rays, particularly for distances of less than 6 in. with minute inhomogeneities or with low values for the absorption differential. The size of inhomogeneity, lower limit of absorption differential, and upper limit of magnification were also studied. For investigation of the distribution of elements in inhomogeneities, it was concluded that, contrary to previous reports, both target element and applied voltage must be carefully chosen after a study of the absorption differential curves. The optimum voltage range is usually 2.5 to 3.5 times the excitation potential.