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Pathogen diseases are increasingly threatening forest trees under the current climate change, causing a remarkable decrease in the stability of forest ecosystems. Ash (Fraxinus excelsior L.) dieback due to Hymenoscyphus fraxineus has been noted in Poland since 1992 and has spread over many European countries. The aim of this study was to test the hypothesis that ash trees affected by dieback could exhibit a reduced vessel size and density along the trunk, as well as a lowered width of annual wood rings, leading to the weakening of water transport towards the crown. Dead and dying ash trees were sampled in a forest district severely affected by ash decline in southern Poland. Wood samples were collected at different height along the trunk and several wood anatomical characteristics of annual tree rings over the period 2002-2011 were examined. Dead trees showed a stronger reduction in radial growth than dying trees over the period considered. Moreover, the diameter of vessels increased from the crown to the base in both dead and dying trees, while the density decreased. Significant differences between dead and dying trees were detected in size and density of vessels in the period analyzed, as well as in the width of annual rings. DNA extracted from wood samples was analyzed using SSR markers and the main genetic parameters of dead and dying trees were estimated, finding similar levels of polymorphism and only slight non-significant differences between the two health groups. Our results are consistent with the hypothesis that pathogens could disrupt the hormonal control of wood formation by interfering with the polar auxin transport, progressively leading to the death of ash trees.

Background: A new, alternative option for patients with recurrent glioblastoma is targeted alpha therapy (TAT), in the form of a local administration of substance P (neurokinin type 1 receptor ligand, NK-1) labelled with 225 Ac. The purpose of the study was to confirm the feasibility of quantitative SPECT imaging of 225 Ac, in a model reproducing specific conditions of TAT. In particular, to present the SPECT calibration methodology used, as well as the results of validation measurements and their accuracy. Additionally, to discuss the specific problems related to high noise in the presented case., Materials and Methods: All SPECT/CT scans were conducted using the Symbia T6 equipped with HE collimators, and acquired with multiple energy windows (three main windows: 440 keV, 218 keV, and 78 keV, with three lower scatter energy windows). A Jaszczak phantom with fillable cylindrical sources of various sizes was used to investigate quantitative SPECT/CT imaging characteristics. The planar sensitivity of the camera, an imaging calibration factor, and recovery coefficients were determined. Additionally, the 3D printed model of the glioblastoma tumour was developed and imaged to evaluate the accuracy of the proposed protocol., Results: Using the imaging calibration factor and recovery coefficients obtained with the Jaszczak phantom, we were able to quantify the activity in a 3D-printed model of a glioblastoma tumour with uncertainty of no more than 10% and satisfying accuracy., Conclusions: It is feasible to perform quantitative 225 Ac SPECT/CT imaging. However, there are still many more challenges that should be considered for further research on this topic (among others: accurate determination of ICF in the case of high background noise, better method of background estimation for recovery coefficient calculations, other methods for scatter correction than the dual-energy window scatter-compensation method used in this study)., (© 2024. The European Atomic Energy Community.)

Background: The purpose was to assess the impact of irradiation technique type and beam energy on the mixed radiation field around the medical linear accelerator (linac) in terms of radiation quality and related radiation protection quantities., Materials and Methods: Seven radiotherapeutic plans with Alderson-Rando anthropomorphic phantom [different techniques: conventional three-dimensional conformal radiotherapy (3D-CRT), intensity-modulated radiotherapy (IMRT) and intensity modulated arc therapy (IMAT), different beams: 6 MV or 18 MV, and their arrangements) were prepared for the case of prostate malignancy. Recombination chambers REM-2 and GW2 were positioned on the treatment couch 100 cm from the beam axis at the height of the isocentre. Recombination chambers REM-2 and GW2 were used for recombination index of radiation quality Q 4 determination, measurement of total tissue dose D t and calculation of gamma and neutron components to D t . Estimation of D t and Q 4 allowed for the ambient dose equivalent H*(10) calculations for each plan., Results: For plans prepared with 6 MV beams, Q 4 values within the limits of uncertainty were equal to one, which confirms the correctness of the measurement method. For plans implemented with 18 MV beams, the value of Q 4 was in the range of 3.7-5.7. Comparison between treatment techniques indicates that the lowest exposure resulting from out-of-field doses comes from 6 MV IMAT (0.7 mSv), whereas the highest one is from 18 MV IMRT (55.1 mSv)., Conclusion: With the recombination chambers technique it was confirmed that the choice of beam energy directly affects the generation of photoneutrons. The treatment plan technique can have a significant impact on the out-of-field dose., Competing Interests: Conflicts of interest: Authors declare no conflict of interest., (© 2024 Greater Poland Cancer Centre.)

The evolution of the vascular system has led to the formation of conducting and supporting elements and those that are involved in the mechanisms of storage and defense against the influence of biotic and abiotic factors. In the case of the latter, the general evolutionary trend was probably related to a change in their arrangement, i.e. from cells scattered throughout the tissue to cells organized into ducts or cavities. These cells, regardless of whether they occur alone or in a cellular structure, are an important defense element of trees, having the ability to synthesize, among others, natural resins. In the tracheid-based secondary xylem of gymnosperms, the resin ducts, which consist of secretory cells, are of two types: axial, interspersed between the tracheids, and radial, carried in some rays. They are interconnected and form a continuous system. On the other hand, in the tracheid-based secondary xylem of monocotyledons, the resin-producing secretory cells do not form specialized structures. This review summarizes knowledge on the morpho-anatomical features of various types of resin-releasing secretory cells in relation to their: (i) location, (ii) origin, (iii) mechanism of formation, (iv) and ecological significance., Competing Interests: The authors declare that the study was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Tulik and Jura-Morawiec.)

Background: The gamma index and dose-volume histogram (DVH)-based patient-specific quality assurance (QA) measures commonly applied in radiotherapy planning are unable to simultaneously deliver detailed locations and magnitudes of discrepancy between isodoses of planned and delivered dose distributions. By exploiting statistical classification performance measures such as sensitivity or specificity, compliance between a planned and delivered isodose may be evaluated locally, both for organs-at-risk (OAR) and the planning target volume (PTV), at any specified isodose level. Thus, a patient-specific QA tool may be developed to supplement those presently available in clinical radiotherapy., Materials and Methods: A method was developed to locally establish and report dose delivery errors in three-dimensional (3D) isodoses of planned (reference) and delivered (evaluated) dose distributions simultaneously as a function the dose level and of spatial location. At any given isodose level, the total volume of delivered dose containing the reference and the evaluated isodoses is locally decomposed into four subregions: true positive-subregions within both reference and evaluated isodoses, true negative-outside of both of these isodoses, false positive-inside the evaluated isodose but not the reference isodose, and false negatives-inside the reference isodose but not the evaluated isodose. Such subregions may be established over the whole volume of delivered dose. This decomposition allows the construction of a confusion matrix and calculation of various indices to quantify the discrepancies between the selected planned and delivered isodose distributions, over the complete range of values of dose delivered. The 3D projection and visualization of the spatial distribution of these discrepancies facilitates the application of the developed method in clinical practice., Results: Several clinical photon radiotherapy plans were analyzed using the developed method. In some plans at certain isodose levels, dose delivery errors were found at anatomically significant locations. These errors were not otherwise highlighted-neither by gamma analysis nor by DVH-based QA measures. A specially developed 3D projection tool to visualize the spatial distribution of such errors against anatomical features of the patient aids in the proposed analysis of therapy plans., Conclusions: The proposed method is able to spatially locate delivery errors at selected isodose levels and may supplement the presently applied gamma analysis and DVH-based QA measures in patient-specific radiotherapy planning., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany.)

Main Conclusion: In Dracaena draco trunks, the primary and secondary xylem conduits co-function. Both are resistant to embolism; however, secondary conduits are mainly involved in mechanical support. Monocotyledonous dragon trees (Dracaena spp., Asparagaceae) possess in their trunks both primary and secondary xylem elements, organized into vascular bundles, that for dozens of years co-function and enable the plant to transport water efficiently as well as provide mechanical support. Here, based on the modified Hagen-Poiseuille's formula, we examined the functional anatomical xylem traits of the trunk in two young D. draco individuals to compare their function in both primary and secondary growth. We provided analyses of the: (i) conduits surface sculpture and their cell walls thickness, (ii) conduit diameter and frequency, (iii) hydraulically weighted diameter, (iv) theoretical hydraulic conductivity, (v) area-weighted mean conduit diameter, as well as (vi) vulnerability index. The conduits in primary growth, located in the central part of the trunk, were loosely arranged, had thinner cell walls, larger mean hydraulically weighted diameter, and significantly larger value of the theoretical hydraulic conductivity than conduits in secondary growth, which form a rigid cylinder near the trunk surface. Based on the vulnerability index, both primary and secondary conduits are resistant to embolism. Taking into account the distribution within a trunk, the secondary growth conduits seems to be mainly involved in mechanical support as they are twisted, form structures similar to sailing ropes and have thick cell walls, and a peripheral localization. D. draco has been adapted to an environment with water deficit by distinctive, spatial separation of the xylem elements fulfilling supportive and conductive functions., (© 2022. The Author(s).)

Purpose: The quality of a measured distribution of dose delivered against its corresponding radiotherapy plan is routinely assessed by gamma index (GI) and dose-volume histogram (DVH) metrics. Any correlation between error detection rates, as based on either of these approaches, while argued, has never been convincingly demonstrated. The dependence of the strength of correlation between the GI passing rate ( γ P ) and DVH quality assurance (QA) metrics on various elements of the therapy plan has not been systematically investigated., Methods: A formal analysis of the relation between γ P and DVH metrics has been undertaken, leading to a relationship which may partly approximate γ P with respect to the DVH. This relationship was further validated by studying examples of simulated clinical radiotherapy plans and by studying the correlation between γ P and the derived relationship using a simple two-dimensional representations of the planning target volume (PTV) and organs at risk (OAR), where penumbra regions, distance-to-agreement tolerances and dose delivery errors were systematically varied., Results: It is shown formally that there cannot be any correlation between γ P and other commonly applied DVH-derived QA measures. However, γ P may be partly approximated given the planned and measured DVH. The derived γ P approximation (the " γ -slope indicator") may be clinically useful in some practical cases of radiotherapy plan QA., Conclusions: In formal terms, there cannot be any correlation between γ P and any common DVH-calculated patient-specific measures, with respect to PTV or OAR. However, as demonstrated analytically and further confirmed in our simulation studies, the γ P approximation derived in this study (the " γ -slope indicator") may in some cases offer a degree of correlation between γ P and the PTV and OAR DVH QA metrics in measured and planned patient-specific dose distributions-which may be potentially useful in clinical practice., (© 2021 American Association of Physicists in Medicine.)

Introduction: The purpose of this study was to present the optimization process of CT parameters to reduce patient exposure during bone SPECT/CT without affecting the quality of SPECT images with attenuation correction (AC)., Material and Methods: A fillable phantom reflecting realistic bone scintigraphy conditions was developed and acquired on an AnyScan SC. SPECT/CT scans were carried out with different x-ray tube current values (10, 20, 30, 40, 50, 60, 70, 90, 110, 130, 150, and 200 mA) at three different high-voltage values (80, 100, and 120 kV). The contrast (C) and coefficients of variation (CV) in the SPECT images as well as the signal-to-noise ratio (SNR) and noise (SD CT ) in the CT images with CTDI vol were measured. An optimal acquisition protocol that obtained SPECT/CT images with no artifacts on both CT and SPECT images, acceptable C, SNR, CV, and SD CT values, and the largest reduction in patient exposure compared to the reference acquisition procedure was sought., Results: The optimal set of parameters for bone SPECT/CT was determined based on a phantom study. It has been implemented in clinical practice. Two groups of patients were examined according to the baseline and optimized protocols, respectively. The new SPECT/CT protocol substantially reduced patients' radiation exposure compared to the old protocol while maintaining the required diagnostic quality of SPECT and CT images., Conclusions: In the study, we present a methodology that finds a compromise between diagnostic information and patient exposure during bone SPECT/CT procedures., (© 2020 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals LLC on behalf of American Association of Physicists in Medicine.)

In the study, a local approach to setting reference tolerance values for the distance-to-agreement (DTA) component of the gamma index is proposed. The reference tolerance values are calculated in simulations, following a dose delivery model presented in a previous work. An analytical model for determining the quantiles of DTA distribution is also proposed and verified. It is shown that the distributions of DTA values normalized with either quantiles or standard deviation of DTA distributions are universal over analyzed plans and points within a single plan. This enables statistically sound inference about the quality of dose delivery. In particular, based on the normalized distributions the comparison of planned and delivered doses can be formulated within the framework of statistical inference as a problem of multiple statistical testing. For every evaluated point P of a plan, one may formulate and test a null hypothesis that there is no delivery error against an alternative hypothesis that there is a delivery error in P. It is also shown that the proposed approach is more sensitive than the current standard approach to shift errors in high dose gradient regions.

Purpose: Assessment of the accuracy of geometric tests of a linac used in external beam therapy is crucial for ensuring precise dose delivery. In this paper, a new simulation-based method for assessing accuracy of such geometric tests is proposed and evaluated on a set of testing procedures., Methods: Linac geometry testing methods used in this study are based on an established design of a two-module phantom. Electronic portal imaging device (EPID) images of fiducial balls contained in these modules can be used to automatically reconstruct linac geometry. The projection of the phantom modules fiducial balls onto the EPID detector plane is simulated for assumed nominal geometry of a linac. Then, random errors are added to the coordinates of the projections of the centers of the fiducial balls and the linac geometry is reconstructed from these data., Results: Reconstruction is performed for a set of geometric test designs and it is shown how the dispersion of the reconstructed values of geometric parameters depends on the design of a geometric test. Assuming realistic accuracy of EPID image analysis, it is shown that for selected testing plans the reconstruction accuracy of geometric parameters can be significantly better than commonly used action thresholds for these parameters., Conclusions: Proposed solution has the potential to improve geometric testing design and practice. It is an important part of a fully automated geometric testing solution., (© 2019 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.)

The gamma index is a measure used routinely for the quality control of dose delivery in radiotherapy, implemented in commercial systems for the verification of treatment plans. It involves comparison of the difference between planned and delivered doses to a single reference. The same reference value is selected for all points in the plan that can potentially hide dose delivery errors, especially in medium and low dose areas. In this study, a receiver operating characteristic analysis is used to demonstrate the limits of the performance of the global gamma index as a method for detecting dose delivery errors. The performance of a global gamma index is compared with two approaches based on statistical tests for outlier detection. Two statistical approaches are considered: according to the first, the distribution of the delivered doses is estimated based on an appropriate calibration procedure. According to the second, the distribution of the delivered doses is estimated based on the detection of relatively homogeneous regions of a plan and analyzing the distributions of planned doses within these regions. The performance of the three approaches is compared based on analytical considerations and in simulations in which errors are intentionally introduced to the plan delivery and noise related to dose delivery is modeled. We have shown that a statistics-based approach to gamma analysis generally leads to better detection of true delivery errors. The results of analytical consideration coincide with the simulations. In simulations, we observe that both statistical approaches are better detectors of true delivery errors than the global method for the gamma-index passing rate in the range from 0.9-1.0. It is shown that the global gamma index is a weak detector of dose delivery errors, which in some circumstances behaves only slightly better than a purely random classifier.

The aim of this study is to investigate secondary mixed radiation field around linac, as the first part of an overall assessment of out-of-field contribution of neutron dose for new advanced radiation dose delivery techniques. All measurements were performed around Varian Clinic 2300 C/D accelerator at Maria Sklodowska-Curie Memorial, Cancer Center and Institute of Oncology, Krakow Branch. Recombination chambers REM-2 and GW2 were used for recombination index of radiation quality Q4 determination (as an estimate of quality factor Q), measurement of total tissue dose Dt and calculation of gamma and neutron components to Dt. Estimation of Dt and Q4 allowed for the ambient dose equivalent H*(10) per monitor unit (MU) calculations. Measurements around linac were performed on the height of the middle of the linac's head (three positions) and on the height of the linac's isocentre (five positions). Estimation of secondary radiation level was carried out for seven different configurations of upper and lower jaws position and multileaf collimator set open or closed in each position. Study includes the use of two photon beam modes: 6 and 18 MV. Spatial distribution of ambient dose equivalent H*(10) per MU on the height of the linac's head and on the standard couch height for patients during the routine treatment, as well as relative contribution of gamma and neutron secondary radiation inside treatment room were evaluated.

Purpose: To develop an assumption-free methodology for testing geometry of linacs., Methods: The problem of projecting a fiducial positioned in a predefined point in a 3D space and attached rigidly to a treatment table of a radiotherapeutic device onto an imaging plane with unknown characteristics from a source with unknown coordinates is formulated. The problem of determining these unknowns is formulated as an optimization problem. The problem of determining the gantry/the collimator rotation axis and angle from projection of additional fiducials is also formulated and solved. Analytical methodology is developed for determining isocenter position and an error of estimating isocenter position. The developed methodology is tested in simulations., Results: Very good agreement between preset and calculated values of quantities of interest was found in the simulations. In all cases, the proposed schemes enabled determination of the geometric characteristics of a radiotherapeutic device with accuracy better than one hundredth of a millimeter and one hundredth of a degree., Conclusions: A concept of a multimodule multifiducial phantom has been introduced. Analytical framework has been developed to extract geometric characteristics of radiotherapy devices from projection images of a phantom. The phantom design and the methodology developed have been tested in simulations., (© 2017 American Association of Physicists in Medicine.)

Dragon's blood is the name given to a red exudate produced by some plant species belonging to the genera Daemonorops , Dracaena , Croton and Pterocarpus . These are endemic to various parts of the globe. It is classified as a resin or latex depending on its mode of secretion and its chemical composition, which is species specific. This red substance functions in defence and is produced (a) constitutively and stored in preformed anatomical structures, or (b) by induction in response to traumatic events, such as mechanical injury, pathogen attack or invasion by insects. Apart from its defensive role in plants, dragon's blood is also a valuable natural resource renowned since antiquity for its diverse medicinal properties and uses in art. Despite the great importance of dragon's blood, our knowledge of the biological basis for its secretion is still incomplete. This review summarizes recent advances in the study of the anatomical basis for its secretion, and discusses its classification and ecological function. Bringing some clarity to these issues may also help in the commercial sourcing of dragon's blood.

This review highlights key historical works and the recent research on the monocot lateral meristems. It discusses the terminological issues (elucidating the terminological inconsistency found in the literature concerned), origination of secondary meristems, their morphology and characteristic features of the derivative tissues. Also the monocot cambium response to hormonal and gravitational stimuli is discussed. The summarized inputs in the present note are believed to renew interest in this field, which is important for a more comprehensive understanding of the abnormal secondary growth in the monocotyledons.

The secondary cell wall structure of tracheids of Scots pine (Pinus sylvestris L.), especially the angle of microfibrils in the S(2) layer, was examined in wood deposited prior to and after the Chernobyl accident in 1986. Microscopic analysis was carried out on wood samples collected in October 1997 from breast height of three pine trees 16, 30 and 42 years old. The polluted site was located in a distance of 5 km south from the Chernobyl nuclear power plant where radioactive contamination in 1997 was 3.7 x 10(5) kBq m(-2). Anatomical analysis showed that the structure of the secondary cell wall in tracheids formed after the Chernobyl accident was changed. Changes occurred both in S(2) and S(3) layers. The angle of microfibrils in S(2) layer in wood deposited after the Chernobyl accident was different in comparison to this measured in wood formed prior to the disaster. The intensity of the changes, i.e. alteration of the microfibrils angle in S(2) layer and unusual pattern of the S(3) layer, depended on the age of the tree and was most intensive in a young tree.

Studies were carried out on wood samples collected in October 1997 from breast height of Scots pine trees (Pinus sylvestris) from site located 5 km south from the Chernobyl nuclear power plant. The radioactive contamination at the site was 3.7x10(5) kBq m(-2). These samples of secondary wood were used as an archive of information about the dynamics of a meristematic tissue cambium affected by ionising radiation from the Chernobyl reactor accident. The results show that frequency of the cambial cells events like anticlinal divisions, intrusive growth and cells elimination, was after the Chernobyl accident, about three times higher in comparison to preceding years. The most interesting finding was that after irradiation the length of tracheids increased. This increase is interpreted as an effect of intracambial competition among cells in the initial layer.