Elemental Composition Of Tissues Research Articles

Effects of tissue heterogeneity and comparisons of collapsed cone and Monte Carlo fast neutron patient dosimetry using the University of Washington clinical neutron therapy system (CNTS)

Fast neutron therapy is a high linear energy transfer (LET) radiation treatment modality offering advantages over low LET radiations. Multileaf collimator technology reduces normal-tissue dose (toxicity) and makes neutron therapy more comparable to MV x-ray treatments. Published clinical-trial and other experiences with fast neutron therapy are reported. Early comparative studies failed to consider differences in target-dose spatial conformality between x-ray and neutron treatments, which is especially important for organs-at-risk close to tumor targets. Treatments planning systems (TPS) for high-energy neutrons lag behind TPS tools for MV x-rays, creating challenges for comparative studies of clinical outcomes. A previously published Monte Carlo model of the University of Washington (UW) Clinical Neutron Therapy System (CNTS) is refined and integrated with the RayStation TPS as an external dose planning/verification tool. The collapsed cone (CC) dose calculations in the TPS are based on measured dose profiles and output factors in water, with the absolute dose determined using a tissue-equivalent ionization chamber. For comparison, independent (external) Monte Carlo simulation computes dose on a voxel-by-voxel basis using an atlas that maps Hounsfield Unit (HU) numbers to elemental composition and density. Although the CC algorithm in the TPS accurately computes neutron dose to water compared to Monte Carlo calculations, calculated dose to water differs from bone or tissue depending largely on hydrogen content. Therefore, the elemental composition of tissue and bone, rather than the material or electron density, affects fast neutron dose. While the CC algorithm suffices for reproducible patient dosimetry in fast neutron therapy, adopting methods that consider tissue heterogeneity would enhance patient-specific neutron dose accuracy relative to national standards for other types of ionizing radiation. Corrections for tissue composition have a significant impact on absolute dose and the relative biological effectiveness (RBE) of neutron treatments compared to other radiation types (MV x-rays, protons, and carbon ions).

X-RAY MICROANALYSIS IN PHYTOPATHOLOGY

X-ray microanalysis methods have significantly expanded the functionality of electron microscopy. X-ray microanalysis is widely applied in activities, which deal with plant physiology. The paper explores the functioning of the stomach apparatus of fodder beans (Vícia fába). The regulation of the stomatal function depends on the potassium concentration in the closing cells. The authors investigated the infestation of wheat leaves with mildew (Erysiphe graminis) (Triticum astivum) and obtained the data that reveal the changes in the elemental composition of tissues in the affected area. This has contributed to find out the role of various elements during the infectious process in case of wheat plants with powdery dew contamination. The paper summarizes the materials on the application of X-ray microanalysis in phytopathology. It stipulates the participation of calcium in the formation of the mechanism of nematode capture in different age colonies of predatory fungi Arthrobotrys oligospores Fres was revealed. The data on tissue barrier in wheat roots, where the transport of both sodium and chlorine salting elements and potassium and calcium macro elements is controlled, are obtained. The authors show that transporting of these elements is regulated by active mechanisms in the endoderm cells. The article demonstrates the results of X-ray microanalysis aimed at determining the content of elements of magnesium, phosphorus, sulfur, potassium and calcium in soybean leaves affected by various diseases. The authors observed the changes in potassium, calcium, magnesium and phosphorus concentration in leaves with bacterial burn, ascochytosis and alternative. They argue the participation of elements in formation of plant resistance to disease and the role of these elements in the physiology of the infectious process.

Application of X-Ray Fluorescence Analysis to Determine the Elemental Composition of Tissues from Different Ovarian Neoplasms

We present the results of x-ray fluorescence analysis of tissues from healthy ovaries and from ovaries with different pathologies: benign and borderline tumors, mucinous and endometrioid cancers, serous carcinomas. We determine the average copper, zinc, calcium, selenium, cadmium, lead, and mercury levels. We observed that in the benign ovarian tumors, we see a significant decrease in the cadmium, mercury, and lead levels compared with healthy tissues. In the borderline neoplasms, the copper level is reduced relative to zinc (Cu/Zn), cadmium, mercury, and lead, and also the zinc concentration is increased. In the ovarian carcinomas, we observed changes in the ratio of the chemical elements in the tumor tissues, depending on the histologic type. The results obtained can be used for differentiation, diagnosis, and adjustment of treatment for different ovarian neoplasms.

First step toward the “fingerprinting” of brain tumors based on synchrotron radiation X-ray fluorescence and multiple discriminant analysis

Synchrotron-radiation-based X-ray fluorescence was applied to the elemental microimaging of neoplastic tissues in cases of various types of brain tumors. The following cases were studied: glioblastoma multiforme, gemistocytic astrocytoma, oligodendroglioma, anaplastic oligodendroglioma, ganglioglioma, fibrillary astrocytoma, and atypical transitional meningioma. Apart from neoplastic tissue, the analysis included areas of tissue apparently without malignant infiltration. The masses per unit area of P, S, Cl, K, Ca, Fe, Cu, Zn, Br, and Rb were used to construct a diagnostic classifier for brain tumors using multiple discriminant analysis. It was found that S, Cl, Cu, Fe, K, Br, and Zn are the most significant elements in the general discrimination of tumor type. The highest similarity in elemental composition was between atypical transitional meningioma and fibrillary astrocytoma. The smallest differentiation was between glioblastoma multiforme and oligodendroglioma. The mean percentage of correct classifications, estimated according to the a posteriori probabilities procedure, was 99.9%, whereas the mean prediction ability of 87.6% was achieved for ten new cases excluded previously from the model construction. The results showed that multiple discriminant analysis based on elemental composition of tissue may be a potentially valuable method assisting differentiation and/or classification of brain tumors.

TH‐A‐220‐05: Evaluating the Impact of Dual Energy CT on LDR Brachytherapy Dose Calculations

Purpose: AAPM TG43, the low dose rate (LDR) brachytherapy dosimetry protocol, ignores the effects of tissue composition and densities. Given the photoelectric effectˈs dominance at the low photon energies in use, the dosimetry is dependent on the elemental composition of tissues. AAPM TG186 was mandated to investigate model based dose calculations (MBDC) such as Monte Carlo (MC) simulations as an alternative to TG43. In MBDC, tissue densities and composition are extracted from single energy CT (SECT) data, which can lead to tissue missassignment. The novel dual energy CT (DECT) technology which is now becoming available may improve tissue segmentation. The study aim is to assess the dose calculation accuracy improvement provided by DECT based tissue segmentation compared to SECT. Methods: A Siemens DECT scanner was modelled with ImaSim, a novel CT image simulation tool. Density and atomic number maps of a virtual phantom containing 23 human tissues were extracted from DECT images taken at 80 kVp and 140 kVp. SECT images taken at 120 kVp were also used for segmentation using 3 and 7 tissues. MC dose calculations were performed with 103‐Pd and 125‐I seeds inserted in the phantom for the three segmentation schemes and compared to a reference calculation. Results: SECT segmentation with 3 tissues performs better than the TG43 approach but does not provide adequate dose calculation accuracy. Increasing the number of tissues to 7 significantly improves accuracy, although errors of more than 10% are observed for certain missassigned tissues. Using DECT segmentation brings accuracy within ±5%. Conclusions: DECT provides superior tissue segmentation resulting in high dose calculation accuracy. While SECT segmentation is outperformed by DECT, dose calculation accuracy is found to be tolerable when using seven tissues, supporting the implementation of MBDC based on widely available SECT.

Proton radiography and fluoroscopy of lung tumors: a Monte Carlo study using patient-specific 4DCT phantoms.

Monte Carlo methods are used to simulate and optimize a time-resolved proton range telescope (TRRT) in localization of intrafractional and interfractional motions of lung tumor and in quantification of proton range variations. The Monte Carlo N-Particle eXtended (MCNPX) code with a particle tracking feature was employed to evaluate the TRRT performance, especially in visualizing and quantifying proton range variations during respiration. Protons of 230 MeV were tracked one by one as they pass through position detectors, patient 4DCT phantom, and finally scintillator detectors that measured residual ranges. The energy response of the scintillator telescope was investigated. Mass density and elemental composition of tissues were defined for 4DCT data. Proton water equivalent length (WEL) was deduced by a reconstruction algorithm that incorporates linear proton track and lateral spatial discrimination to improve the image quality. 4DCT data for three patients were used to visualize and measure tumor motion and WEL variations. The tumor trajectories extracted from the WEL map were found to be within 1 mm agreement with direct 4DCT measurement. Quantitative WEL variation studies showed that the proton radiograph is a good representation of WEL changes from entrance to distal of the target. MCNPX simulation results showed that TRRT can accurately track the motion of the tumor and detect the WEL variations. Image quality was optimized by choosing proton energy, testing parameters of image reconstruction algorithm, and comparing to ground truth 4DCT. The future study will demonstrate the feasibility of using the time resolved proton radiography as an imaging tool for proton treatments of lung tumors.

SU‐GG‐J‐148: Evaluation of Performance of a Conceptual Time‐Resolved Proton Range Telescope for In‐Room Respiration Monitoring Using Monte Carlo Simulations and 4DCT Patient Data

Purpose: To demonstrate the feasibility to perform and optimize a time‐resolved proton range telescope (TRRT) in localization of moving lung tumors and quantification of proton range variations. Method: A TRRT is designed to detect transmission protons and provide a fluoroscopic image showing tumor location and range perturbations prior to or during treatment. MCNPX code with a particle‐tracking feature was used to simulate and evaluate the TRRT performance, especially in visualizing and quantifying the proton range variations during respiration. Monoenergetic protons, 235 MeV in a 15cm × 15cm field, were tracked one by one as they pass through position detectors, 4DCT phantom, and finally scintillators that measured position and residual energies. Mass density and elemental composition of tissues were defined from a set of 4DCT of a lung patient. Radiological pathlength in the patient was determined by an energy‐range algorithm. Effects of multiple Coulomb scattering on image quality were determined by comparison with a pure ray‐tracing algorithm in Aqualyzer. Results: Interesting water equivalent length (WEL) maps for 10 respiratory phases were obtained to form fluoroscopic sequences. Appropriate color‐map windowing was used to visualize and measure tumor trajectories. The tumor trajectory extracted from the proton fluoroscopic simulation agreed with ground‐truth established by 4DCT to about 1mm. WEL difference maps were reconstructed to quantify respiration‐induced range changes. The maximum proton range pullback for the tumor target was measured to be 2.29 cm. Rejection of wide angle scatter events was found to effectively sharpen the image. Clinical applications to track the tumor during proton therapy using the range telescope are discussed. Conclusion: The performance of a TRRT is systematically studied and demonstrated by Monte Carlo simulations. When parameters are optimized, localization of a 2cm tumor is possible with an accuracy of about 1mm. Technical requirements for an operational device are discussed, including GPU acceleration.

Ecological stoichiometry in six species of Antarctic marine benthos

Elemental (C, N, P) composition was examined in 6 benthic marine invertebrates from Antarctica: 2 suspension feeders (the holothurian Heterocucumis steineni and the polychaete Thele- pus cincinnatus), 1 epifaunal grazer (the limpet Nacella concinna), 1 deposit feeder (the polychaete Flabelligera mundata), 1 predator (the nemertean Parborlasia corrugatus) and an omnivore (the asteroid Odontaster validus). Correction for inorganic carbon was necessary only for O. validus, where skeletal carbonate produces a high mineral ash content. Elemental composition of tissue was 49 to 60% C, 10 to 14% N and 0.7 to 1.3% P (all on an organic mass basis); these are all within the normal range of values for aquatic invertebrates. The most variable component was P, though vari- ability was much lower than in stream insects. Stoichiometric molar ratios (C:P, C:N, N:P) were all typical of consumers, with a strong inverse relationship across species between %C and %N in tis- sue. Stoichiometry varied strongly between phyla, with less variation between species within phyla. There were also indications of variations in elemental composition (C:N ratio and %P) with feeding mode, but the limited range of taxa studied constrains this conclusion. Despite differences in nutrient status, the elemental composition of marine and freshwater benthos were, with the exception of insects, closely similar. Despite the very slow growth rates that characterise polar marine benthos, P contents were relatively high, suggesting that the predictions of the growth rate hypothesis are not upheld at low temperatures.

Essential elements and contaminants in edible tissues of European and American lobsters

In several European countries clawed lobsters, such as the European ( Homarus gammarus) and American ( H. americanus) ones are widely consumed. Yet, information about essential elements and contaminants in both species is still scarce. Therefore, the aim of this work was to characterise the elemental content in the edible part (muscle, hepatopancreas, gonads and roe) of both homarids and to compare them with the daily intake recommendations and maximum allowed levels. Two techniques were employed: energy-dispersive X-ray fluorescence (EDXRF) to quantify Cl, S, K, Ca, Fe, Cu, Zn, As, Se, Br and Sr; and flame atomic-absorption spectrometry (FAAS) to analyse Na, Mg, Mn, Cd, Hg and Pb. Significant differences were found in the elemental composition of edible tissues of both species, likely reflecting the distinct physiological role of those tissues: muscle (higher: Na, Mg, Ca and Sr; lower: Fe, Se, Cd); hepatopancreas (higher: Fe, Cu, Br and Cd); gonads (lower: Cl, Ca, Zn and Hg); and roe (higher: Na and Br; lower: K and As). Statistical differences in the elemental composition of each tissue were found between both homarids: Muscle (Na, Se, As and Hg); Hepatopancreas (Na, Mg, Fe, Cu, Se, Br and Hg); and gonads (S and Zn). Since the geographical distribution of both species is different, the differences likely reflect distinct elemental composition in the aquatic environment and, consequently in the feed chain. Both lobster species were rich sources of Na, Cl, Cu, Zn and Se for human consumption. Regarding contaminants, only Cd was detected at high concentrations in the hepatopancreas of both homarids. Despite Cd values were well above the maximum allowed level set by the European Commission for crustaceans’ muscle, so far any limit value was set for crustaceans’ hepatopancreas. Nonetheless, the present study recommends avoiding or moderately consuming this tissue in homarids.

Estimation of Tissue Construction Cost from Heat of Combustion and Organic Nitrogen Content

Abstract. We present a method for estimating the construction costs of plant tissues from measurements of heat of combustion, ash content, and organic nitrogen content. The method predicts glucose equivalents, the amount of glucose required to provide carbon skeletons and reductant to synthesize a quantity of organic product. Glucose equivalents have previously been calculated from the elemental composition of tissue. We define construction cost as the amount of glucose required to provide carbon skeletons, reductant and ATP for synthesizing the organic compounds in a tissue via standard biochemical pathways. The fraction of the total construction cost of a compound or tissue (excluding costs of transporting compounds) that is reflected in its glucose equivalents is the biosynthetic efficiency (EB). This quantity varies between 0.84 and 0.95 for tissues with a wide range of compositions. Using the new method, total construction cost can be estimated to ± 6% of the value obtained from biochemical pathway analysis.Construction costs of leaves of three chaparral species were estimated using the proposed method and compared to previously published values, derived using different methods. Agreement among methods was generally good. Differences were probably due to a combination of inaccuracy in the estimated biosynthetic efficiency and technical difficulties with biochemical analysis, one of the older methods of determining construction cost.

Schistosoma mansoni: Electron probe X-ray microanalysis of the elemental composition of the tegument and subtegumental tissues of adult worms

The elementary composition [Na, Mg, P, S, Cl, K, Ca and Fe] of the tegument, tegumental spines, and subtegumental tissues of adult male and female Schistosoma mansoni have been determined by electron probe X-ray microanalysis of unfixed, freeze-dried cryosections. Statistical analysis of the results suggests that there are distinct differences in the elemental composition of the tissues both between and within individual male and female worms, and between male and female worms in general. In particular, there were significant variations in the elemental contents of the tissues between individual male and female worms, which may reflect differences in the physiology and/or metabolic state of the worms. Significant differences in the elemental composition of the various tissues examined within individual worms were also found. In general, in both male and female worms, there were significantly higher elemental levels in the tegument, as opposed to the subtegumental tissues. The elemental composition of the tegumental spines in both male and female worms differed from that of the tegumental cytoplasm, although the differences in the elemental composition between spines from male and female worms reflected the differences in the elemental content between the teguments themselves. Differences in the elemental composition of the tissues between male and female worms were also found, with the female tegument containing significantly higher elemental levels (with the exception of Cl) than the male tegument. In particular, the tegument of female worms contained higher levels of calcium and, in relatively small areas, isolated calcium-containing granules. This higher tegumental calcium level in female worms may reflect a higher calcium demand by sexually mature female worms due to the presence, within the mature vitelline cells, of calcium-containing corpuscles and the production of large numbers of eggs.