Elements In Biological Tissues Research Articles

Breast cancer detection using neutron stimulated emission computed tomography: Prominent elements and dose requirements

Neutron stimulated emission computed tomography (NSECT) is being developed to noninvasively determine concentrations of trace elements in biological tissue. Studies have shown prominent differences in the trace element concentration of normal and malignant breast tissue. NSECT has the potential to detect these differences and diagnose malignancy with high accuracy with dose comparable to that of a single mammogram. In this study, NSECT imaging was simulated for normal and malignant human breast tissue samples to determine the significance of individual elements in determining malignancy. The normal and malignant models were designed with different elemental compositions, and each was scanned spectroscopically using a simulated 2.5 MeV neutron beam. The number of incident neutrons was varied from 0.5 million to 10 million neutrons. The resulting gamma spectra were evaluated through receiver operating characteristic (ROC) analysis to determine which trace elements were prominent enough to be considered markers for breast cancer detection. Four elemental isotopes (133Cs, 81Br, 79Br, and 87Rb) at five energy levels were shown to be promising features for breast cancer detection with an area under the ROC curve (A(Z)) above 0.85. One of these elements--87Rb at 1338 keV--achieved perfect classification at 10 million incident neutrons and could be detected with as low as 3 million incident neutrons. Patient dose was calculated for each gamma spectrum obtained and was found to range from between 0.05 and 0.112 mSv depending on the number of neutrons. This simulation demonstrates that NSECT has the potential to noninvasively detect breast cancer through five prominent trace element energy levels, at dose levels comparable to other breast cancer screening techniques.

Proton induced X-ray analysis of Nd:YAG

Proton induced X-ray emission (PIXE) is famously effective for revealing trace elements in biological tissue in which the majority elements (H, C, N and O) have low Z. When the majority elements in a compound have high atomic numbers, the yield of K and L X-rays following proton bombardment often mask those of lighter trace elements, or dominate the counting rate to such an extent that the time required to detect a small signal with statistical significance becomes prohibitively long. We have confronted these difficulties with a PIXE analysis of YAG crystals and ceramics with neodymium doping up to nine atomic percent. The K X-rays of aluminum (1.74keV) and yttrium (15keV) dominate the PIXE spectrum. The L X-rays from neodymium group near 5keV provide determination of the neodymium content of Nd:YAG to 1:1000. Clear signals of traces of zinc, nickel and copper were recovered from the spectra of some of the samples by persistent experiments at low counting rates that avoided pile up of the signals from the majority elements. An appropriate polyethylene filter was used to prevent scattered protons from striking the detector and its supporting structure. Double proton beam collimation prevented spurious PIXE from the chamber walls, beam stop and the primary collimator. No material was near the sample except a polyethylene film strip that supported the sample.

X-ray Absorption Fine Structure (XAFS) Analysis of Titanium-implanted Soft Tissue

Tissues contacting Ti dental implants were subjected to X-ray absorption fine structure (XAFS) analysis to examine the chemical state of Ti transferred from the placed implant into the surrounding tissue. Nine tissues that contacted pure Ti cover screws for several months were excised in a second surgery whereby healing abutments were set. Six tissues that surrounded implants retrieved due to their failure were also excised. Ti distributions in the excised specimens were confirmed by X-ray scanning analytical microscopy (XSAM), and the specimens were subjected to fluorescence XAFS analysis to determine the chemical states of the low concentrations of Ti in the tissues surrounding Ti dental implants. Ti mostly existed in the metallic state and was considered to be debris derived from the abrasion of implant pieces during implant surgery. Oxidized forms of Ti, such as anatase and rutile, were also detected in a few specimens-and existed in either a pure state or mixed state with metallic Ti. It was concluded that the existence of Ti in the tissue did not cause implant failure. Moreover, the usefulness of XAFS for analysis of the chemical states of rarely contained elements in biological tissue was demonstrated.

Selenium Distribution in Human Soft Tissue Determined by Using X-ray Scanning Analytical Microscope and X-ray Absorption Fine Structure Analysis

Abstract Se localilzation in the human oral mucosae which contain dental amalgam or dental silver alloy particles was analyzed by X-ray scanning analytical microscopy (XSAM). Se distribution was visualized, and the localization in the neighbor of amalgam or silver particles was confirmed. The chemical state of Se was analyzed by X-ray absorption fine structure (XAFS) analysis. Se was estimated as the low valency state. The possibility of using XSAM and XAFS for the analysis of the distribution and chemical state of rarely contained elements in biological tissue was suggested.

Analysis of Titanium Dental Implants Surrounding Soft Tissue Using X-ray Absorption Fine Structure (XAFS) Analysis

Abstract X-ray absorption fine structure (XAFS) analysis was applied for the analysis of titanium (Ti) in the human oral mucosa in contact with Ti dental implants from two different patients. Metallic Ti and an oxide (anatase) were detected. The metallic Ti was distributed in particulate form, which would be debris formed by the abrasion during the operation of implantation. The possibility of using XAFS for the analysis of the chemical state of rarely contained elements in biological tissue was suggested.

Imaging of selenium in plants using tapered metal monocapillary optics.

Tapered metal monocapillary optics provide a potential alternative to conventional methods of producing small X-ray beams. This paper presents the initial results of chemically specific imaging using such devices. Cellular resolution of organic selenium is obtained in a longitudinal section of mature Astragalus bisulcatus, a selenium hyperaccumulating plant. This work demonstrates the utility of metal monocapillary optics for imaging dilute levels of target elements in biological tissues.

Positional distribution of elements in biological tissue

The multielement positional distributions obtained by the micro-scanning technique in a few different biological tissues were assayed by multivariate statistical analysis. The results showed that the elements in normal tissues could be classified in two groups: the first consisting of the minor elements and the other of the trace elements. On the other hand, in abnormal tissues this kind of classification was changed and might indirectly conform with the results published by other authors. This means that the experiments with high sensitivity using micro-beam combined with the advanced statistical analysis could make it possible to discriminate the element types and to clarify some metabolism processes in micro-size biological tissues. More combined studies are necessary to find out further evidences of these facts.

Optics for X-ray Microfluorescence to Be Used at the European Synchrotron Radiation Facility

Micro-SRXRF (Synchrotron Radiation induced X-ray Fluorescence) is ti microanalytical technique which, utilizes an intense, polarized X-ray micro beam originating from the storage ring to induce X-ray fluorescence in a microscopic volume of the sample under investigation. The emerging fluorescent and scattered radiation is normally detected by an energy-dispersive Si(Li) detector. The recorded fluorescent spectra provide qualitative and quantitative information on the examined material yielding minimum, detection limits in the ppm and in favourable cases in the sub-ppm range at current SRXRF-facilities. Possible applications of synchrotron X-ray microprobes are the mapping of chemical elements in biological tissues, investigation of element migration and partitioning in geological systems, the analysis of individual microscopic particles and a variety of topics in applied research.

A universal method for quantifying and comparing the residual variability of element concentrations in biological tissues using 25 elements in the mussel Mytilus edulis as a model

The concentrations of elements in biological tissue may be influenced by a large number of environmental and physiological factors. Even when all known sources of variability have been either eliminated or taken into account, a very high degree of unexplained residual variability may persist between individual organisms within the same population. In the present study, a simple statistical method is described which permits the calculation of the residual variabilities of element concentrations, even from complex multivariate data, and allows statistical comparison between elements to be made (either within a single tissue, between different tissues or between different species). The method is quite general and could also be used for studying residual variability in any other natural phenomena (e.g. enzyme concentrations, water temperature). The case of 25 element concentrations in the whole soft tissue of the mussel Mytilus edulis collected from Bellevue, Newfoundland, Canada in June 1988 was used as a model. It was clearly shown that some elements (e.g. the alkali earth elements and B, Mg and Cu) had extremely low residual variability while other elements (e.g. Ce, Zn, Ba, La, U, Pb, Ag, Y, Sr and Ca) showed unusually high degrees of residual variability. Al also showed very high variability but this appeared to be due to the presence of undigested sediment in the gut rather than to residual variability. Important sources of non-residual variability included sex, size and growth rate. The method described in this paper could be used as an initial screening test for pinpointing intrapopulation genetic differences in element metabolism between individual organisms.

Determination of trace elements in biological tissues by aluminum block digestion and spike-height flame atomic absorption spectrometry

A method for the determination of cadmium, copper, lead, and zinc in biological tissues using small volumes of digest is described. An aluminium heating block is used to digest samples and elements are determined by spike-height flame atomic absorption spectrometry. Interferences have been assessed and the sample decomposition procedure evaluated.

STANDARDS FOR QUANTITATIVE X-RAY MICROANALYSIS OF BIOLOGICAL SPECIMENS

The use of ion exchange beads is proposed as standards for the estimation of various elements in biological tissues.

Cryopreparation of mammalian tissue for X-ray microanalysis in STEM.

A cryopreparation technique for studies of ultrastructure and distribution of diffusible elements in biological tissue is described. Electron microscopical contrast and characteristic X-ray spectra are found to be poor in completely frozen-hydrated ultrathin cryosections of fresh chemically untreated tissue. Both STEM contrast and detection of characteristic X-rays are enhanced by careful freeze-drying in the microscope. Although the ultrastructure is affected by ice crystals, intracellular compartments can be identified by STEM without staining and studied by X-ray microanalysis.

Determination of trace elements in human serum by energy dispersive X-ray fluorescence

A system of energy dispersive X-ray fluorescence spectrometry (EDXRF) has been described to measure the concentrations of iron, copper, zinc, bromine, selenium and arsenic in human serum of healthy adults. Methods of sample preparations, standardization, and analysis have been presented. Data have been presented to show the accuracy, precision and sensitivity of the EDXRF system. The major advantages of using this system for the determination of trace elements in biological tissues are the relatively small sample size, ease of sample preparation, and the ability to perform rapid multi-element analysis on a single sample. The need for multi-element analysis has become apparent from the increased knowledge of trace element interactions in biological systems. The EDXRF system provides a solution for this need. Although the present system was applied only to the measurement of six elements, in principle the concentrations of V, Cr, Mn, Ni and Ti could also be routinely determined with improvements in technology and sensitivity.

Retention of metabolised trace elements in biological tissues following different drying procedures. Part II. Caesium, cerium, manganese, scandium, silver and tin in rat tissues.

Losses of silver, cerium, caesium, manganese, scandium and tin during freeze drying and oven drying at 80, 105 and 120 °C were studied in rat tissues and faces that contained radioactive isotopes. No loss was observed for any of these elements on freeze drying. A significant loss of tin was observed in muscle even at 80 °C, and in kidney and liver at 105 °C. Also, cerium and manganese were lost from heart and muscle at this temperature. An increase in the temperature to 120 °C was found to be safe only for silver and caesium in all of the tissues. For the remaining four elements the following losses were observed: up to 5% for cerium in brain and heart, for scandium in fur and heart and for manganese in liver and muscle; up to 10% for scandium in kidney and muscle and for tin in blood, fur, heart, liver, ovary and uterus; and over 10% for tin in brain, kidney, lung and muscle.

Localisation and quantification of elements in biological tissues by electron‐microprobe analysis

AbstractAn introduction is provided to the basic ideas and theory of electron‐microprobe analysis as applied to biological tissue. The nature of characteristic and continuous X‐rays is outlined. X‐ray detectors, specimen preparation and the relative advantages and disadvantages of thick and thin section techniques are discussed.

Analysis of human blood and liver tissue for copper, zinc and iron by the method of proton-induced X-ray emission analysis

The method of proton-induced X-ray emission (or PIXE) analysis has been investigated with reference to the study of minor and trace elements in biological tissue. Methods of specimen preparation have been investigated, and optimum instrumental conditions arrived at. The lower limits of detection for lead and zinc in blood have been investigated and have been found to be approximately 0.3 and 0.1 ppm for lead and zinc respectively, for a proton energy of 2.5 MeV. The concentrations of copper, zinc and iron have been studied in normal and diseased human liver tissue. In cirrhotic tissue the copper levels are substantially raised. We note also a diminution in liver iron in a case of alcoholic cirrhosis associated with clinical anaemia; and a blood zinc deficiency in primary biliary cirrhosis. The results are discussed in relation to existing work.

Retention of the metabolized trace elements in biological tissues following different drying procedures: I. Antimony, cobalt, iodine, mercury, selenium and zinc in rat tissues

Loss of Sb, Co, I, Hg, Se and Zn during freeze-drying and oven-drying at 80, 105 and 120 °C were studied in rat tissues that contained metabolized radioactive isotopes. No loss was observed for any of the 6 elements on freeze-drying. However, tissue-specific differences were observed in many cases for Hg, Se, I and Sb on oven-drying. A significant loss of Hg was observed in liver even at 80 °C, and for brain 105 °C. Se was lost from whole blood, brain, lung and muscle at 120 °C. Sb was lost from whole blood at 105 °C, but from brain, kidney, lung and spleen at 120 °C. Iodine was also lost from whole blood, kidney, blood serum, erythrocytes, brain, lung and muscle at 120 °C. Although the losses were statistically significant, they remained in most cases between 2 and 10%, with the exception of Hg at 120 °C, where the loss in some of the tissues were unpredictable. For urine, freeze-drying and oven-drying at 80 °C was found to be relatively safe for Hg and I. At 105 °C and above, serious loss of Hg was observed. In this experiment, the elements Zn, Co, Sb and Se were not studied for urine.

Radiochemical determination of chromium in biological tissues by ion-exchange

A simple ion exchange procedure has been developed for the separation of chromium from the other chemical elements in biological tissues. This procedure combined with neutron activation analysis has been applied successfully to the determination of chromium in a reference biological material. The precision was ±11%, the accuracy 3% and the sensitivity found was 10 ng with only 20 hrs irradiation at 2.8·1013 n·cm−2·sec−1 flux The main steps of the procedure are: wetdigestion of the irradiated tissue, oxidation to chromium (VI), fixation onto an anion resin in sulfate form, washing of the resin with 1N H2SO4, collection of chromium by reductive elution for counting and finally determination of the chemical yield by reactivation.

An ion-exchange group-separation scheme for rapid analysis of the components of neutron-activated biological tissues

A simple ion-exchange separation scheme has been developed for the separation of over 50 constituent chemical elements in biological tissues into 12 to 15 groups suitable for quantitative gamma-ray spectrometry. The scheme incorporates several important improvements and modifications of earlier radiochemical ion-exchange separation procedures, and allows rapid simultaneous quantitative analyses of a large number of constituent components in tissues. The procedures can easily be adapted for use with a variety of other materials and mixtures. The components of the various fractious are listed and their gamma-spectrometric analysis is discussed. The separation is comparatively quick, and yields clean and easily-identifiable components.