Clinical anatomy of pulmonary connections in young people.

OBJECTIVE: Aim: To study the clinical anatomy of the pulmonary ligaments of young people. PATIENTS AND METHODS: Materials and Methods: The study was carried out when performing 28 autopsies of young people aged 25 to 44 years. Methods of dissection of chest organocomplexes, macro-microscopy, morphometry and planimetry, and statistical processing were used. The shape and topography of the pulmonary ligaments was assessed, their area, the localization of lymph nodes was examined. RESULTS: Results: The pulmonary ligament is an anatomical formation, which is formed as a result of a combination of leaves of the mediastinal pleura, which, covering the surfaces of the roots of the lungs, descend towards the diaphragm and are located between the mediastinal organs and the lungs. Pulmonary connections on both sides have a few edges: the inner, outer and lower free. The pulmonary ligaments with lower free edges do not pass to the diaphragmatic surface of the pleura, but only with inner ones, which are located on the right along the esophagus, and on the left along the aorta. Pulmonary ligaments on both sides pass into the mediastinal part of the pleura, covering the pericardium. CONCLUSION: Conclusions: There are individual differences between the shape and size of the right and left pulmonary ligaments in males and females. There is no significant difference between the sizes of the right and left pulmonary ligaments, but such dimensions as: the width, the angle of inclination and the ratio of their lower free edge to the lower edge of the lungs are not found in all cases.

Characterization of transient and progressive pulmonary fibrosis by spatially correlated phase contrast microCT, classical histopathology and atomic force microscopy.

Pulmonary fibrosis (PF) is a severe and progressive condition in which the lung becomes scarred over time resulting in pulmonary function impairment. Classical histopathology remains an important tool for micro-structural tissue assessment in the diagnosis of PF. A novel workflow based on spatial correlated propagation-based phase-contrast micro computed tomography (PBI-microCT), atomic force microscopy (AFM) and histopathology was developed and applied to two different preclinical mouse models of PF - the commonly used and well characterized Bleomycin-induced PF and a novel mouse model for progressive PF caused by conditional Nedd4-2 KO. The aim was to integrate structural and mechanical features from hallmarks of fibrotic lung tissue remodeling. PBI-microCT was used to assess structural alteration in whole fixed and paraffin embedded lungs, allowing for identification of fibrotic foci within the 3D context of the entire organ and facilitating targeted microtome sectioning of planes of interest for subsequent histopathology. Subsequently, these sections of interest were subjected to AFM to assess changes in the local tissue stiffness of previously identified structures of interest. 3D whole organ analysis showed clear morphological differences in 3D tissue porosity between transient and progressive PF and control lungs. By integrating the results obtained from targeted AFM analysis, it was possible to discriminate between the Bleomycin model and the novel conditional Nedd4-2 KO model using agglomerative cluster analysis. As our workflow for 3D spatial correlation of PBI, targeted histopathology and subsequent AFM is tailored around the standard procedure of formalin-fixed paraffin-embedded (FFPE) tissue specimens, it may be a powerful tool for the comprehensive tissue assessment beyond the scope of PF and preclinical research.

Bronchial tree of the human embryo: Examination based on a mammalian model.

The symmetry of the right and left bronchi, proposed in a previous comparative anatomical study as the basic model of the mammalian bronchial tree, was examined to determine if it applied to the embryonic human bronchial tree. Imaging data of 41 human embryo specimens at Carnegie stages (CS) 16-23 (equivalent to 6-8 weeks after fertilization) belonging to the Kyoto collection were obtained using phase-contrast X-ray computed tomography. Three-dimensional bronchial trees were then reconstructed from these images. Bronchi branching from both main bronchi were labeled as dorsal, ventral, medial, or lateral systems based on the branching position with numbering starting cranially. The length from the tracheal bifurcation to the branching point of the labeled bronchus was measured, and the right-to-left ratio of the same labeled bronchus in both lungs was calculated. In both lungs, the human embryonic bronchial tree showed symmetry with an alternating pattern of dorsal and lateral systems up to segmental bronchus B9 as the basic shape, with a more peripheral variation. This pattern is similar to that described in adult human lungs. Bronchial length increased with the CS in all labeled bronchi, whereas the right-to-left ratio was constant at approximately 1.0. The data demonstrated that the prototype of the human adult bronchial branching structure is formed and maintained in the embryonic stage. The morphology and branching position of all lobar bronchi and B6, B8, B9, and the subsegmental bronchus of B10 may be genetically determined. On the other hand, no common structures between individual embryos were found in the peripheral branches after the subsegmental bronchus of B10, suggesting that branch formation in this region is influenced more by environmental factors than by genetic factors.

Morphological variations of the lung: Accessory fissures and lobes.

Anatomical variability in the human body is not as rare as was previously hypothesised. Indeed, as recently reviewed, the term 'norm' in anatomy can be considered an approximation. Thus, anatomical variations occur quite often, as largely demonstrated during non-invasive diagnosis, surgical intervention, or post mortem investigations. In the present study, we describe different anatomical variations in both the right and left lungs derived from cadavers of different ethnicities. The analysed organs were collected during dissection, and accessory lobes and fissures were observed in both the right and left lungs. Moreover, a horizontal fissure was missing from the right lung, resulting in only two lobes. Since lung anatomical variability is common in clinical practice and preclinical imaging studies can miss different morphologies, a deep and accurate knowledge of the anatomical variations of the lung is of extreme importance to avoid difficulties or changes during the surgical procedure.

Asymmetric lung increases particle filtration by deposition.

Human lung is known to be an asymmetric dichotomously branched network of bronchioles. Existing literature on the relation between anatomy and air-flow physics in the tracheobronchial trees has discussed the results of asymmetry. We discuss a secondary (but an important) lung function to seek asymmetry: to protect the acinus from a high pathogen load. We build morphometric parameter-based mathematical models of realistic bronchial trees to explore the structure-function relationship. We observe that maximum surface area for gas exchange, minimum resistance and minimum volume are obtained near the symmetry condition. In contrast, we show that deposition of inhaled foreign particles in the non-terminal airways is enhanced by asymmetry. We show from our model, that the optimal value of asymmetry for maximum particle filtration is within 10% of the experimentally measured value in human lungs. This structural trait of the lung aids in self-defence of the host against pathogen laden aerosols. We explain how natural asymmetric design of typical human lungs makes a sacrifice away from gas exchange optimality to gain this protection. In a typical human lung, when compared to most optimal condition (which is associated with symmetric branching), the fluidic resistance is 14% greater, the gas exchange surface area is about 11% lower, the lung volume is about 13% greater to gain an increase of 4.4% protection against foreign particles. This afforded protection is also robust to minor variations in branching ratio or variation in ventilation, which are both crucial to survival.

Association of age with computed tomography airway tree morphology in male and female never smokers without lung disease history.

BACKGROUND: Sex and aging may affect the airway tree structure in patients with airway diseases and even healthy subjects. Using chest computed tomography (CT), this study sought to determine whether age is associated with airway morphological features differently in healthy males and females. METHODS: This retrospective cross-sectional study consecutively incorporated lung cancer screening CT data of asymptomatic never smokers (n = 431) without lung disease history. Luminal areas were measured at the trachea, main bronchi, bronchus intermedius, segmental and subsegmental bronchus, and the ratio of their geometric mean to total lung volume (airway-to-lung size ratio, ALR) was determined. Airway fractal dimension (AFD) and total airway count (TAC) were calculated for the segmented airway tree resolved on CT. RESULTS: The lumen areas of the trachea, main bronchi, segmental and subsegmental airways, AFD and TAC visible on CT were smaller in females (n = 220) than in males (n = 211) after adjusting for age, height, and body mass index, while ALR or count of the 1st to 5th generation airways did not differ. Furthermore, in males but not in females, older age was associated with larger lumen sizes of the main bronchi, segmental and subsegmental airways, and ALR. In contrast, neither male nor female had any associations between age and AFD or TAC on CT. CONCLUSION: Older age was associated with larger lumen size of the relatively central airways and ALR exclusively in males. Aging may have a more profound effect on airway lumen tree caliber in males than in females.

Spherical alveolar shapes in live mouse lungs.

Understanding how the alveolar mechanics work in live lungs is essential for comprehending how the lung behaves during breathing. Due to the lack of appropriate imaging tools, previous research has suggested that alveolar morphologies are polyhedral rather than spherical based on a 2D examination of alveoli in fixed lungs. Here, we directly observe high-resolution 3D alveoli in live mice lungs utilizing synchrotron x-ray microtomography to show spherical alveolar morphologies from the live lungs. Our measurements from x-ray microtomography show high sphericity, low packing density, big alveolar size, and low osmotic pressure, indicating that spherical alveolar morphologies are natural in living lungs. The alveolar packing fraction is quite low in live lungs, where the spherical alveoli would behave like free bubbles, while the confinement of alveolar clusters in fixed lungs would lead to significant morphological deformations of the alveoli appearing polyhedral. Direct observations of the spherical alveolar shapes will help understand and treat lung disease and ventilation.

Morphological characteristics and pulmonary function of naval saboteurs and ground special forces of the armed forces of Montenegro / Características morfológicas y función pulmonar de saboteadores navales y fuerzas especiales terrestres de las fuerzas armadas de Montenegro

SUMMARY: The results of numerous medical and kinesiological studies indicate the existence of differences in pulmonary function in relation to age, body height, and the relationship between certain parameters of body composition. The aim of this study was to determine the state of morphological characteristics and pulmonary function of naval saboteurs and ground Special Forces of the Armed Forces of Montenegro. The sample of participants included 30 naval saboteurs aged 30.3±6 years and 30 members of the ground special forces aged 25.6±5 years. The sample of measuring instruments included 4 indicators each for the evaluation of longitudinal dimensionality, transversal dimensionality, mass and body volume, subcutaneous fat, body composition, and pulmonary function. The central and dispersion parameters of the variables were calculated. The specificities of body composition of the naval saboteurs and members of the ground Special Forces of the AF of Montenegro were determined, while the parameters of lung volume and capacity and the parameters of airway flow indicated an excellent state of their respiratory function. Furthermore, it was determined that the studied members of the armed forces had no individual health risks in the sense of the onset of obesity or obstructive ventilatory defects. The results obtained indicate the need for further studies which would predominantly focus on the impact of individual morphological measurements and parameters of body composition on pulmonary function. This would provide important data both for the armed forces in the sense of improving the training system and the realization of specific tasks, as well as for kinesiology as a science from the aspect of determining certain regularities in the functioning of the human body in specific living and working conditions in the armed forces.

Los resultados de numerosos estudios médicos y kinesiológicos indican la existencia de diferencias en la función pulmonar en relación con la edad, la altura corporal y la relación entre determinados parámetros de la composición corporal. El objetivo de este estudio fue determinar el estado de las características morfológicas y la función pulmonar de los saboteadores navales y de las Fuerzas Especiales terrestres de las Fuerzas Armadas de Montenegro. La muestra de participantes incluyó a 30 saboteadores navales de 30,3±6 años de edad y 30 miembros de las fuerzas especiales terrestres de 25,6±5 años. La muestra de instrumentos de medición incluyó 4 indicadores cada uno para la evaluación de dimensionalidad longitudinal, dimensionalidad transversal, masa y volumen corporal, grasa subcutánea, composición corporal y función pulmonar. Se calcularon los parámetros centrales y de dispersión de las variables. Se determinaron las especificidades de la composición corporal de los saboteadores navales y miembros de las Fuerzas Especiales terrestres de la FA de Montenegro, mientras que los parámetros de volumen y capacidad pulmonar y los parámetros de flujo de las vías respiratorias indicaron un excelente estado de su función respiratoria. Además, se determinó que los miembros de las fuerzas armadas estudiados no tenían riesgos individuales de salud en el sentido de la obesidad o defectos ventilatorios obstructivos. Los resultados obtenidos indican la necesidad de más estudios que se centren predominantemente en el impacto de las medidas morfológicas individuales y los parámetros de composición corporal en la función pulmonar. Esto proporcionaría datos importantes tanto para las fuerzas armadas en el sentido de mejorar el sistema de entrenamiento y la realización de tareas específicas, como para la kinesiología como ciencia desde el aspecto de determinar ciertas regularidades en el funcionamiento del cuerpo humano en situaciones específicas de vida. y condiciones de trabajo en las fuerzas armadas.

Structure and function adaption of lung in Phrynocephalus vlangalii by multiple mechanisms / Estructura y adaptación funcional del pulmón en Phrynocephalus vlangalii por múltiples mecanismos

SUMMARY: Respiration and water-liquid transportation are controlled by many factors in the lung. The aim of this study was to explore the structure and proteins expression in lungs of Phrynocephalus vlangalii by means of gross anatomy, light microscope observation, scanning electron microscope and immunohistochemistry. Results show that there were many alveoli in the lung and the walls of alveoli and capillaries were very thin. The inner surface of the lung was divided into many cystic chambers by reticular diaphragm, and the network of pulmonary capillaries was dense. Immunohistochemistry showed that AQP1 was mainly expressed in the epithelium of interstitial bronchi, parabronchiole endothelium, capillary endothelium and alveolar epithelial cells. VIP positive nerve fibers are mainly distributed in trachea, bronchial smooth muscle layer, the walls of pulmonary vessels and bronchial vessels and around submucosal glands. CECR2 is distributed in peripheral capillaries and small. Investigations of structure and proteins biology could be relevant with the adaptive strategy to drought and hypoxia environment in Phrynocephalus vlangalii.

La respiración y el transporte de agua y líquido están controlados en el pulmón por muchos factores. El objetivo de este estudio fue explorar la estructura y la expresión de proteínas en los pulmones de Phrynocephalus vlangalii por medio de la anatomía macroscópica, observación con microscopio óptico, microscopio electrónico de barrido e inmunohistoquímica. Los resultados muestran que había muchos alvéolos en el pulmón y que las paredes de los alvéolos y de los capilares eran muy delgadas. La superficie interna del pulmón estaba dividida en cámaras quísticas por el diafragma reticular y se observó una densa red de capilares pulmonares. La inmunohistoquímica mostró que AQP1 se expresaba principalmente en el epitelio de los bronquios intersticiales, el endotelio parabronquial, el endotelio capilar y las células epiteliales alveolares. Las fibras nerviosas VIP positivas se distribuyen principalmente en la tráquea, la capa de músculo liso bronquial, las paredes de los vasos pulmonares y los vasos bronquiales y alrededor de las glándulas submucosas. CECR2 se distribuye en pequeño capilares periféricos. Las investigaciones de la biología de la estructura y las proteínas podrían ser relevantes con la estrategia de adaptación al entorno de sequía e hipoxia en Phrynocephalus vlangalii.

[Modern imaging of the pulmonary hilum : Anatomy, pathologies, pitfalls]. / Moderne Bildgebung des Lungenhilus : Anatomie, Pathologien, Pitfalls.

BACKGROUND: Modern medical imaging is a key component of efficient in- and out-patient precision medicine. Conventional radiography and computer tomography scans (CT) are among the most frequent radiologic exams. Medical imaging plays a key role in target-oriented medicine. OBJECTIVES: The purpose of this article is to review the anatomy of the hilum of the lung and its most frequent associated pathologies since it is an important gateway of elementary structures of the thorax. Important signs and patterns for image interpretation in different modalities are also reviewed. RESULTS: Thorough knowledge of anatomy, signs, and patterns of pathologies especially in conventional radiography and pitfalls of the more sensitive cross-sectional imaging is essential to support target-oriented patient care. CONCLUSION: Conventional radiography is affordable and readily available. It is very suitable for pathology screening, i.e., at the hilum of the lung. Cross-sectional imaging specifies diagnostics due to superior anatomic discrimination.

Topography of pleural epithelial structure enabled by en face isolation and machine learning.

Pleural epithelial adaptations to mechanical stress are relevant to both normal lung function and parenchymal lung diseases. Assessing regional differences in mechanical stress, however, has been complicated by the nonlinear stress-strain properties of the lung and the large displacements with ventilation. Moreover, there is no reliable method of isolating pleural epithelium for structural studies. To define the topographic variation in pleural structure, we developed a method of en face harvest of murine pleural epithelium. Silver-stain was used to highlight cell borders and facilitate imaging with light microscopy. Machine learning and watershed segmentation were used to define the cell area and cell perimeter of the isolated pleural epithelial cells. In the deflated lung at residual volume, the pleural epithelial cells were significantly larger in the apex (624 ± 247 µm2 ) than in basilar regions of the lung (471 ± 119 µm2 ) (p < 0.001). The distortion of apical epithelial cells was consistent with a vertical gradient of pleural pressures. To assess epithelial changes with inflation, the pleura was studied at total lung capacity. The average epithelial cell area increased 57% and the average perimeter increased 27% between residual volume and total lung capacity. The increase in lung volume was less than half the percent change predicted by uniform or isotropic expansion of the lung. We conclude that the structured analysis of pleural epithelial cells complements studies of pulmonary microstructure and provides useful insights into the regional distribution of mechanical stresses in the lung.

Pulmonary vessels and bronchus anatomy of the left upper lobe.

PURPOSES: The bronchopulmonary vascular bifurcation patterns in the upper lobe of the left lung are diverse. Therefore, it is important for general thoracic surgeons to understand the detailed anatomy of the pulmonary segments when performing thoracoscopic anatomical pulmonary resection. This study aimed to analyze the bronchovascular patterns of the left upper lobe and summarize the anatomical information associated with pulmonary anatomical pulmonary resection. METHODS: We reviewed the anatomical patterns of pulmonary vessels and the left lung bronchus of 539 patients using computed tomography imaging data including those obtained using three-dimensional computed tomography. We herein report the anatomic structure in the left upper lobe. RESULTS: Regarding the superior division bronchi, a pattern of trifurcation into B1+2, B3, lingular division bronchus was observed in nine patients (1.7%). A pattern of proximal bifurcation of B4 was found in eight patients (1.5%). Regarding the lingular veins (LV), patterns of LV drainage into the left lower pulmonary vein were observed in 22 patients (4.1%). Regarding the pulmonary artery, mediastinal lingular arteries (MLA) were found in 161 patients (29.9%). CONCLUSION: The bifurcation patterns of the bronchovascular region in the upper lobe of the left lung were clarified. These results should be carefully noted when performing anatomical pulmonary resection.

Concepts of advanced therapeutic delivery systems for the management of remodeling and inflammation in airway diseases.

Chronic respiratory disorders affect millions of people worldwide. Pathophysiological changes to the normal airway wall structure, including changes in the composition and organization of its cellular and molecular constituents, are referred to as airway remodeling. The inadequacy of effective treatment strategies and scarcity of novel therapies available for the treatment and management of chronic respiratory diseases have given rise to a serious impediment in the clinical management of such diseases. The progress made in advanced drug delivery, has offered additional advantages to fight against the emerging complications of airway remodeling. This review aims to address the gaps in current knowledge about airway remodeling, the relationships between remodeling, inflammation, clinical phenotypes and the significance of using novel drug delivery methods.

Impact of lung structure on airway opening index during mechanical versus manual chest compressions in a porcine model of cardiac arrest.

OBJECTIVES: The exhaled CO2 signal provides guidance during cardiopulmonary resuscitation. The Airway opening index (AOI) has been recently used to quantify chest-compression (CC) induced expired CO2 oscillations. We aimed to determine whether levels of intrathoracic pressures developed during CC or parameters related to lung structure may affect AOI. METHODS: Secondary analysis of a randomized animal study (n = 12) in a porcine model of cardiac arrest (CA) and cardiopulmonary resuscitation (CPR) during ambulance transport. Animals were randomized to 18-min of manual or mechanical CCs. Changes in AOI and right atrial pressure (ΔRAP) were recorded during CCs in animals undergoing manual (n = 6) or mechanical (n = 6) CCs. Lung CT scan and measurement of the respiratory system compliance (Cpl,rs) were performed immediately after return of spontaneous circulation. RESULTS: Animals undergoing mechanical CCs had a lower AOI compared to animals treated with manual CCs (p < 0.001). AOI negatively correlated with the swings of intrathoracic pressure, as measured by the change in ΔRAP (ρ=-0.727, p = 0.007). AOI correlated with the lung density (ρ=-0.818, p = 0.001) and with the Cpl,rs (ρ = 0.676, p = 0.016). Animals with cardiopulmonary resuscitation associated lung edema (CRALE) (i.e. mean CT≥-500 HU) showed lower levels of AOI compared to animals without it (29 ± 12 % versus 50 ± 16 %, p = 0.025). CONCLUSIONS: Animals undergoing mechanical CCs had lower levels of AOI compared to animals undergoing manual CCs. A higher swing of intrathoracic pressure during CC, a denser and a stiffer lung were associated with an impaired CO2 exhalation during CC as observed by a lower AOI.

Anatomy of the left subsuperior segment for segmentectomy.

PURPOSE: The subsuperior segmental bronchi (B*) forms the subsuperior segment (S*) between the superior (S6) and basal segment (S7, S8, S9, S10) of the lung. However, the anatomical planes of S* remains undefined. The present study clarified the anatomical features of S*. METHODS: We reviewed the anatomical patterns of pulmonary vessels and the left lung bronchus in 539 patients using three-dimensional computed tomography. We report the anatomic structure in S*. RESULTS: A total of 537 patients were analyzed. B* was observed in 129 (24.0%) patients. The intersegmental vein between S6 and S* was complete in all cases. The absence of intersegmental veins of S* was observed in 77 (14.3%) patients, reaching 59.7% of B* cases. Twenty-two (4.1%) cases of B* diverged from the trunk of the basal bronchus, and about half of the B* branched to the dorsolateral (n = 77, 14.3%) or dorsal (n = 2, 0.37%) direction. CONCLUSION: Our study revealed the branching patterns of B* and anatomical intersegmental veins of S*. Our results provide useful information regarding anatomical segmentectomy including or adjusting to the left S*.

Clinical and surgical implications of the pulmonary azygos lobe: a systematic review / Implicaciones clínicas y quirúrgicas del lóbulo ácigos pulmonar: una revisión sistemática

SUMMARY: Azygos lobe is one of the most common pulmonary variations. Although numerous studies discuss to the clinical and surgical implications of anatomical variations, there are few investigations about this topic. The aim of this study was to discuss the anatomy of the pulmonary azygos lobe and its possible clinical and surgical correlations. In this systematic review, a total of 48 results were found between 1968 and 2020. After application of eligibility criteria, 16 articles were included to analysis. Our results showed there were no reports of surgery complications in azygos lobe presence. In all articles that described the anatomical variation, the pulmonary azygos lobe received tertiary segmental branches. Among the surgical implications in the presence of the azygos lobe, complications are of low complexity. It is necessary to teach about this anatomical variation in medical schools in cadavers. Emphasizing the obvious morphological modifications in the superior mediastinum.

RESUMEN: El lóbulo ácigos es una de las variaciones pulmonares más comunes. Aunque numerosos estudios discuten las implicaciones clínicas y quirúrgicas de las variaciones anatómicas, existen pocas investigaciones sobre este tema. El objetivo de este estudio fue discutir la anatomía del lóbulo ácigos pulmonar y sus posibles correlaciones clínicas y quirúrgicas. En esta revisión sistemática se encontraron un total de 48 resultados entre los años 1968 y 2020. Después de la aplicación de los criterios de elegibilidad, 16 artículos fueron incluidos para análisis. Nuestros resultados mostraron que no hubo informes de complicaciones quirúrgicas en presencia del lóbulo ácigos. En todos los artículos que describieron la variación anatómica, el lóbulo ácigos pulmonar recibió ramas segmentarias terciarias. Dentro de las implicaciones quirúrgicas en presencia del lóbulo ácigos, las complicaciones son de baja complejidad. En las escuelas de medicina es necesaria la enseñanza en cadáveres de esta variación anatómica, destacando las evidentes modificaciones morfológicas en el mediastino superior.

Modeling Respiratory Signals by Deformable Image Registration on 4DCT Lung Images.

The lung organ of human anatomy captured by a medical device reveals inhalation and exhalation information for treatment and monitoring. Given a large number of slices covering an area of the lung, we have a set of three-dimensional lung data. And then, by combining additionally with breath-hold measurements, we have a dataset of multigroup CT images (called 4DCT image set) that could show the lung motion and deformation over time. Up to now, it has still been a challenging problem to model a respiratory signal representing patients' breathing motion as well as simulating inhalation and exhalation process from 4DCT lung images because of its complexity. In this paper, we propose a promising hybrid approach incorporating the local binary pattern (LBP) histogram with entropy comparison to register the lung images. The segmentation process of the left and right lung is completely overcome by the minimum variance quantization and within class variance techniques which help the registration stage. The experiments are conducted on the 4DCT deformable image registration (DIR) public database giving us the overall evaluation on each stage: segmentation, registration, and modeling, to validate the effectiveness of the approach.

Physical density estimations of single- and dual-energy CT using material-based forward projection algorithm: a simulation study.

OBJECTIVES: This study aims to evaluate the accuracy of physical density prediction in single-energy CT (SECT) and dual-energy CT (DECT) by adapting a fully simulation-based method using a material-based forward projection algorithm (MBFPA). METHODS: We used biological tissues referenced in ICRU Report 44 and tissue substitutes to prepare three different types of phantoms for calibrating the Hounsfield unit (HU)-to-density curves. Sinograms were first virtually generated by the MBFPA with four representative energy spectra (i.e. 80 kVp, 100 kVp, 120 kVp, and 6 MVp) and then reconstructed to form realistic CT images by adding statistical noise. The HU-to-density curves in each spectrum and their pairwise combinations were derived from the CT images. The accuracy of these curves was validated using the ICRP110 human phantoms. RESULTS: The relative mean square errors (RMSEs) of the physical density by the HU-to-density curves calibrated with kV SECT nearly presented no phantom size dependence. The kV-kV DECT calibrated curves were also comparable with those from the kV SECT. The phantom size effect became notable when the MV X-ray beams were employed for both SECT and DECT due to beam-hardening effects. The RMSEs were decreased using the biological tissue phantom. CONCLUSION: Simulation-based density prediction can be useful in the theoretical analysis of SECT and DECT calibrations. The results of this study indicated that the accuracy of SECT calibration is comparable with that of DECT using biological tissues. The size and shape of the calibration phantom could affect the accuracy, especially for MV CT calibrations. ADVANCES IN KNOWLEDGE: The present study is based on a full simulation environment, which accommodates various situations such as SECT, kV-kV DECT, and even kV-MV DECT. In this paper, we presented the advances pertaining to the accuracy of the physical density prediction when applied to SECT and DECT in the MV X-ray energy range. To the best of our knowledge, this study is the first to validate the physical density estimation both in SECT and DECT using human-type phantoms.

Characteristics of pulmonary microvascular structure in postnatal yaks.

Yaks are typical plateau-adapted animals, however the microvascular changes and characteristics in their lungs after birth are still unclear. Pulmonary microvasculature characteristics and changes across age groups were analysed using morphological observation and molecular biology detection in yaks aged 1, 30 and 180 days old in addition to adults. Results: Our experiments demonstrated that yaks have fully developed pulmonary alveolar at birth but that interalveolar thickness increased with age. Immunofluorescence observations showed that microvessel density within the interalveolar septum in the yak gradually increased with age. In addition, transmission electron microscopy (TEM) results showed that the blood-air barrier of 1-day old and 30-days old yaks was significantly thicker than that observed at 180-days old and in adults (P < 0.05), which was caused by the thinning of the membrane of alveolar epithelial cells. Furthermore, Vegfa and Epas1 expression levels in 30-day old yaks were the highest in comparison to the other age groups (P < 0.05), whilst levels in adult yaks were the lowest (P < 0.05). The gradual increase in lung microvessel density can effectively satisfy the oxygen requirements of ageing yaks. In addition, these results suggest that the key period of yak lung development is from 30 to 180 days.

X-ray Dark-Field Chest Imaging: Qualitative and Quantitative Results in Healthy Humans.

Background X-ray dark-field radiography takes advantage of the wave properties of x-rays, with a relatively high signal in the lungs due to the many air-tissue interfaces in the alveoli. Purpose To describe the qualitative and quantitative characteristics of x-ray dark-field images in healthy human subjects. Materials and Methods Between October 2018 and January 2020, patients of legal age who underwent chest CT as part of their diagnostic work-up were screened for study participation. Inclusion criteria were a normal chest CT scan, the ability to consent, and the ability to stand upright without help. Exclusion criteria were pregnancy, serious medical conditions, and changes in the lung tissue, such as those due to cancer, pleural effusion, atelectasis, emphysema, infiltrates, ground-glass opacities, or pneumothorax. Images of study participants were obtained by using a clinical x-ray dark-field prototype, recently constructed and commissioned at the authors' institution, to simultaneously acquire both attenuation-based and dark-field thorax radiographs. Each subject's total dark-field signal was correlated with his or her lung volume, and the dark-field coefficient was correlated with age, sex, weight, and height. Results Overall, 40 subjects were included in this study (average age, 62 years ± 13 [standard deviation]; 26 men, 14 women). Normal human lungs have high signal, while the surrounding osseous structures and soft tissue have very low and no signal, respectively. The average dark-field signal was 2.5 m-1 ± 0.4 of examined lung tissue. There was a correlation between the total dark-field signal and the lung volume (r = 0.61, P < .001). No difference was found between men and women (P = .78). Also, age (r = -0.18, P = .26), weight (r = 0.24, P = .13), and height (r = 0.01, P = .96) did not influence dark-field signal. Conclusion This study introduces qualitative and quantitative values for x-ray dark-field imaging in healthy human subjects. The quantitative x-ray dark-field coefficient is independent from demographic subject parameters, emphasizing its potential in diagnostic assessment of the lung. ©RSNA, 2021 See also the editorial by Hatabu and Madore in this issue.