Search

New Findings: What is the central question of this study?How does the interaction between posture and gravity affect the stresses on the lung, particularly in highly inflated gravitationally non‐dependent regions, which are potentially vulnerable to increased mechanical stress and injury?What is the main finding and its importance?Changes in stress attributable to gravity are not well characterized between postures. Using a new metric of gravitational stress, we show that regions of the lung near maximal inflation have the greatest gravitational stresses while supine, but not while prone. In simulations of increased lung weight consistent with severe pulmonary oedema, the prone lung has lower gravitational stress in vulnerable, non‐dependent regions, potentially protecting them from overinflation and injury. Prone posture changes the gravitational vector, and potentially the stress induced by tissue deformation, because a larger lung volume is gravitationally dependent when supine, but non‐dependent when prone. To evaluate this, 10 normal subjects (six male and four female; age, means ± SD = 27 ± 6 years; height, 171 ± 9 cm; weight, 69 ± 13 kg; forced expiratory volume in the first second/forced expiratory volume as a percentage of predicted, 93 ± 6%) were imaged at functional residual capacity, supine and prone, using magnetic resonance imaging, to quantify regional lung density. We defined regional gravitational stress as the cumulative weight, per unit area, of the column of lung tissue below each point. Gravitational stress was compared between regions of differing inflation to evaluate differences between highly stretched, and thus potentially vulnerable, regions and less stretched lung. Using reference density values for normal lungs at total lung capacity (0.10 ± 0.03 g/ml), regions were classified as highly inflated (density < 0.13 g/ml, i.e., close to total lung capacity), intermediate (0.13 ≤ density < 0.16 g/ml) or normally inflated (density ≥ 0.16 g/ml). Gravitational stress differed between inflation categories while supine (−1.6 ± 0.3 cmH2O highly inflated; −1.4 ± 0.3 cmH2O intermediate; −1.1 ± 0.1 cmH2O normally inflated; P = 0.05) but not while prone (−1.4 ± 0.2 cmH2O highly inflated; −1.3 ± 0.2 cmH2O intermediate; −1.3 ± 0.1 cmH2O normally inflated; P = 0.39), and increased more with height from dependent lung while supine (−0.24 ± 0.02 cmH2O/cm supine; −0.18 ± 0.04 cmH2O/cm prone; P = 0.05). In simulated severe pulmonary oedema, the gradient in gravitational stress increased in both postures (all P < 0.0001), was greater in the supine posture than when prone (−0.57 ± 0.21 cmH2O/cm supine; −0.34 ± 0.16 cmH2O/cm prone; P = 0.0004) and was similar to the gradient calculated from supine computed tomography images in a patient with acute respiratory distress syndrome (−0.51 cmH2O/cm). The non‐dependent lung has greater gravitational stress while supine and might be protected while prone, particularly in the presence of oedema. [ABSTRACT FROM AUTHOR]

Introduction: We previously introduced the inverse solution guidance algorithm (ISGA) methodology using a Single Equivalent Moving Dipole model of cardiac electrical activity to localize both the exit site of a re‐entrant circuit and the tip of a radiofrequency (RF) ablation catheter. The purpose of this study was to investigate the use of ISGA for ablation catheter guidance in an animal model. Methods: Ventricular tachycardia (VT) was simulated by rapid ventricular pacing at a target site in eleven Yorkshire swine. The ablation target was established using three different techniques: a pacing lead placed into the ventricular wall at the mid‐myocardial level (Type‐1), an intracardiac mapping catheter (Type‐2), and an RF ablation catheter placed at a random position on the endocardial surface (Type‐3). In each experiment, one operator placed the catheter/pacing lead at the target location, while another used the ISGA system to manipulate the RF ablation catheter starting from a random ventricular location to locate the target. Results: The average localization error of the RF ablation catheter tip was 0.31 ± 0.08 cm. After analyzing approximately 35 cardiac cycles of simulated VT, the ISGA system's accuracy in locating the target was 0.4 cm after four catheter movements in the Type‐1 experiment, 0.48 cm after six movements in the Type‐2 experiment, and 0.67 cm after seven movements in the Type‐3 experiment. Conclusion: We demonstrated the feasibility of using the ISGA method to guide an ablation catheter to the origin of a VT focus by analyzing a few beats of body surface potentials without electro‐anatomic mapping. [ABSTRACT FROM AUTHOR]

In recent years, several studies have been performed on methods of investigating the periphery of power lines using remote sensing. Among the survey methods using unmanned aerial vehicles (UAVs), those methods are being studied wherein the environment around power lines is photographed by a UAV, and separation measurements are performed by reconstructing the three‐dimensional (3D) point cloud between power lines and the vegetation. Such methods currently rely on reconstructing the power line, making it necessary to acquire images from a position close to the power line. However, by using information available from the power company on the position and structure of pylons and the sag of power lines, it is possible to calculate the position of the power line without 3D reconstruction. In this study, time series management of vegetation around power lines was enabled using the data obtained by UAVs at different times and information on the transmission equipment. © 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Mycoplasma pneumonia with mild CNS involvements should be considered of MERS, even in adult. From the case series, splenial single lesions by MRI and prodromal fever with varied neurological manifestations recovered completely by antibiotics were seen. [ABSTRACT FROM AUTHOR]

Oxygen‐sensitive MRI has been extensively used to investigate tumor oxygenation based on the response (R2* and/or R1) to a gas breathing challenge. Most studies have reported response to hyperoxic gas indicating potential biomarkers of hypoxia. Few studies have examined hypoxic gas breathing and we have now evaluated acute dynamic changes in rat breast tumors. Rats bearing syngeneic subcutaneous (n = 15) or orthotopic (n = 7) 13762NF breast tumors were exposed to a 16% O2 gas breathing challenge and monitored using blood oxygen level dependent (BOLD) R2* and tissue oxygen level dependent (TOLD) T1‐weighted measurements at 4.7 T. As a control, we used a traditional hyperoxic gas breathing challenge with 100% O2 on a subset of the subcutaneous tumor bearing rats (n = 6). Tumor subregions identified as responsive on the basis of R2* dynamics coincided with the viable tumor area as judged by subsequent H&E staining. As expected, R2* decreased and T1‐weighted signal increased in response to 100% O2 breathing challenge. Meanwhile, 16% O2 breathing elicited an increase in R2*, but divergent response (increase or decrease) in T1‐weighted signal. The T1‐weighted signal increase may signify a dominating BOLD effect triggered by 16% O2 in the relatively more hypoxic tumors, whereby the influence of increased paramagnetic deoxyhemoglobin outweighs decreased pO2. The results emphasize the importance of combined BOLD and TOLD measurements for the correct interpretation of tumor oxygenation properties. [ABSTRACT FROM AUTHOR]

Various microbes, including fungi and bacteria, that live in cold environments produce ice‐binding proteins (IBPs) that protect them from freezing. Ascomycota and Basidiomycota are two major phyla of fungi, and Antarctomyces psychrotrophicus is currently designated as the sole ascomycete that produces IBP (AnpIBP). However, its complete amino acid sequence, ice‐binding property, and evolutionary history have not yet been clarified. Here, we determined the peptide sequences of three new AnpIBP isoforms by total cDNA analysis and compared them with those of other microbial IBPs. The AnpIBP isoforms and ascomycete‐putative IBPs were found to be phylogenetically close to the bacterial ones but far from the basidiomycete ones, which is supported by the higher sequence identities to bacterial IBPs than basidiomycete IBPs, although ascomycetes are phylogenetically distant from bacteria. In addition, two of the isoforms of AnpIBP share low sequence identity and are not close in the phylogenetic tree. It is hence presumable that these two AnpIBP isoforms were independently acquired from different bacteria through horizontal gene transfer (HGT), which implies that ascomycetes and bacteria frequently exchange their IBP genes. The non‐colligative freezing‐point depression ability of AnpIBP was not very high, whereas it exhibited significant abilities of ice recrystallization inhibition, ice shaping, and cryo‐protection against freeze–thaw cycles even at submicromolar concentrations. These results suggest that HGT is crucial for the cold‐adaptive evolution of ascomycetes, and their IBPs offer freeze resistance to organisms to enable them to inhabit the icy environments of Antarctica. Databases: Nucleotide sequence data are available in the DDBJ database under the accession numbers LC378707, LC378707, LC378707 for AnpIBP1a, AnpIBP1b, AnpIBP2, respectively. Ice‐binding proteins (IBPs) are cryoprotective polypeptides produced by various cold‐adapted microbes, such as bacteria and fungi. We identified two IBP genes from an Antarctic fungus, Antarctomyces psychrotrophicus. Phylogenetic analysis revealed that these two genes were possibly acquired from two different bacteria through horizontal gene transfer, which suggests that IBP genes are frequently exchanged between different microbes in Antarctica. [ABSTRACT FROM AUTHOR]

Key points Pulmonary perfusion measurement using magnetic resonance imaging combined with deformable image registration enabled us to quantify the change in the spatial distribution of pulmonary perfusion at different lung volumes., The current study elucidated the effects of tidal volume lung inflation [functional residual capacity (FRC) + 500 ml and FRC + 1 litre] on the change in pulmonary perfusion distribution., Changes in hydrostatic pressure distribution as well as transmural pressure distribution due to the change in lung height with tidal volume inflation are probably bigger contributors to the redistribution of pulmonary perfusion than the changes in pulmonary vasculature resistance caused by lung tissue stretch., Abstract Tidal volume lung inflation results in structural changes in the pulmonary circulation, potentially affecting pulmonary perfusion. We hypothesized that perfusion is recruited to regions receiving the greatest deformation from a tidal breath, thus ensuring ventilation-perfusion matching. Density-normalized perfusion (DNP) magnetic resonance imaging data were obtained in healthy subjects ( n = 7) in the right lung at functional residual capacity (FRC), FRC+500 ml, and FRC+1.0 l. Using deformable image registration, the displacement of a sagittal lung slice acquired at FRC to the larger volumes was calculated. Registered DNP images were normalized by the mean to estimate perfusion redistribution (nDNP). Data were evaluated across gravitational regions (dependent, middle, non-dependent) and by lobes (upper, RUL; middle, RML; lower, RLL). Lung inflation did not alter mean DNP within the slice ( P = 0.10). The greatest expansion was seen in the dependent region ( P < 0.0001: dependent vs non-dependent, P < 0.0001: dependent vs middle) and RLL ( P = 0.0015: RLL vs RUL, P < 0.0001: RLL vs RML). Neither nDNP recruitment to RLL [+500 ml = −0.047(0.145), +1 litre = 0.018(0.096)] nor to dependent lung [+500 ml = −0.058(0.126), +1 litre = −0.023(0.106)] were found. Instead, redistribution was seen in decreased nDNP in the non-dependent [+500 ml = −0.075(0.152), +1 litre = −0.137(0.167)) and increased nDNP in the gravitational middle lung [+500 ml = 0.098(0.058), +1 litre = 0.093(0.081)] ( P = 0.01). However, there was no significant lobar redistribution ( P < 0.89). Contrary to our hypothesis, based on the comparison between gravitational and lobar perfusion data, perfusion was not redistributed to the regions of the most inflation. This suggests that either changes in hydrostatic pressure or transmural pressure distribution in the gravitational direction are implicated in the redistribution of perfusion away from the non-dependent lung. [ABSTRACT FROM AUTHOR]

Purpose: Sparse-sampling and reconstruction techniques represent an attractive strategy to achieve faster image acquisition speeds, while maintaining adequate spatial resolution and signal-to-noise ratio in rapid magnetic resonance imaging (MRI). The authors investigate the use of one such sequence, broad-use linear acquisition speed-up technique (k-t BLAST) in monitoring tumor motion for thoracic and abdominal radiotherapy and examine the potential trade-off between increased sparsification (to increase imaging speed) and the potential loss of "true" information due to greater reliance on a priori information. Methods: Lung tumor motion trajectories in the superior–inferior direction, previously recorded from ten lung cancer patients, were replayed using a motion phantom module driven by an MRI-compatible motion platform. Eppendorf test tubes filled with water which serve as fiducial markers were placed in the phantom. The modeled rigid and deformable motions were collected in a coronal image slice using balanced fast field echo in conjunction with k-t BLAST. Root mean square (RMS) error was used as a metric of spatial accuracy as measured trajectories were compared to input data. The loss of spatial information was characterized for progressively increasing acceleration factor from 1 to 16; the resultant sampling frequency was increased approximately from 2.5 to 19 Hz when the principal direction of the motion was set along frequency encoding direction. In addition to the phantom study, respiration-induced tumor motions were captured from two patients (kidney tumor and lung tumor) at 13 Hz over 49 s to demonstrate the impact of high speed motion monitoring over multiple breathing cycles. For each subject, the authors compared the tumor centroid trajectory as well as the deformable motion during free breathing. Results: In the rigid and deformable phantom studies, the RMS error of target tracking at the acquisition speed of 19 Hz was approximately 0.3–0.4 mm, which was smaller than the reconstructed pixel resolution of 0.67 mm. In the patient study, the dynamic 2D MRI enabled the monitoring of cycle-to-cycle respiratory variability present in the tumor position. It was seen that the range of centroid motion as well as the area covered due to target motion during each individual respiratory cycle was underestimated compared to the entire motion range observed over multiple breathing cycles. Conclusions: The authors' initial results demonstrate that sparse-sampling- and reconstructionbased dynamic MRI can be used to achieve adequate image acquisition speeds without significant information loss for the task of radiotherapy guidance. Such monitoring can yield spatial and temporal information superior to conventional offline and online motion capture methods used in thoracic and abdominal radiotherapy. [ABSTRACT FROM AUTHOR]

Purpose: To accurately and efficiently reconstruct a continuous surface from noisy point clouds captured by a surface photogrammetry system (VisionRT). Methods: The authors have developed a level-set based surface reconstruction method on point clouds captured by a surface photogrammetry system (VisionRT). The proposed method reconstructs an implicit and continuous representation of the underlying patient surface by optimizing a regularized fitting energy, offering extra robustness to noise and missing measurements. By contrast to explicit/discrete meshing-type schemes, their continuous representation is particularly advantageous for subsequent surface registration and motion tracking by eliminating the need for maintaining explicit point correspondences as in discrete models. The authors solve the proposed method with an efficient narrowband evolving scheme. The authors evaluated the proposed method on both phantom and human subject data with two sets of complementary experiments. In the first set of experiment, the authors generated a series of surfaces each with different black patches placed on one chest phantom. The resulting VisionRT measurements from the patched area had different degree of noise and missing levels, since VisionRT has difficulties in detecting dark surfaces. The authors applied the proposed method to point clouds acquired under these different configurations, and quantitatively evaluated reconstructed surfaces by comparing against a high-quality reference surface with respect to root mean squared error (RMSE). In the second set of experiment, the authors applied their method to 100 clinical point clouds acquired from one human subject. In the absence of ground-truth, the authors qualitatively validated reconstructed surfaces by comparing the local geometry, specifically mean curvature distributions, against that of the surface extracted from a high-quality CT obtained from the same patient. Results: On phantom point clouds, their method achieved submillimeter reconstruction RMSE under different configurations, demonstrating quantitatively the faith of the proposed method in preserving local structural properties of the underlying surface in the presence of noise and missing measurements, and its robustness toward variations of such characteristics. On point clouds from the human subject, the proposed method successfully reconstructed all patient surfaces, filling regions where raw point coordinate readings were missing. Within two comparable regions of interest in the chest area, similar mean curvature distributions were acquired from both their reconstructed surface and CT surface, with mean and standard deviation of (μrecon = -2.7×10-3 mm-1,σrecon = 7.0×10-3 mm-1) and (μCT = -2.5×10-3 mm-1,σCT = 5.3×10-3 mm-1), respectively. The agreement of local geometry properties between the reconstructed surfaces and the CT surface demonstrated the ability of the proposed method in faithfully representing the underlying patient surface. Conclusions: The authors have integrated and developed an accurate level-set based continuous surface reconstruction method on point clouds acquired by a 3D surface photogrammetry system. The proposed method has generated a continuous representation of the underlying phantom and patient surfaces with good robustness against noise and missing measurements. It serves as an important first step for further development of motion tracking methods during radiotherapy. [ABSTRACT FROM AUTHOR]

Purpose: To validate a fast gradient echo sequence for rapid (9 s) quantitative imaging of lung water. Materials and Methods: Eleven excised pig lungs were imaged with a fast GRE sequence in triplicate, in the sagittal plane at 2 levels of inflation pressure (5 and 15 cm H [ABSTRACT FROM AUTHOR]

There is a gravitational influence on pulmonary perfusion, including in the most dependent lung, where perfusion is reduced, termed Zone 4. Studies using xenon-133 show Zone 4 behaviour, present in the dependent 4 cm at total lung capacity (TLC), affects the dependent 11 cm at functional residual capacity (FRC) and almost all the lung at residual volume (RV). These differences were ascribed to increased resistance in extra-alveolar vessels at low lung volumes although other mechanisms have been proposed. To further evaluate the behaviour of perfusion in dependent lung using a technique that directly measures pulmonary perfusion and corrects for tissue distribution by measuring regional proton density, seven healthy subjects (age = 38 ± 6 years, FEV= 104 ± 7% predicted) underwent magnetic resonance imaging in supine posture. Data were acquired in the right lung during breath-holds at RV, FRC and TLC. Arterial spin labelling quantified regional pulmonary perfusion, which was normalized for regional proton density measured using a fast low-angle shot technique. The height of the onset of Zone 4 behaviour was not different between lung volumes ( P= 0.23). There were no significant differences in perfusion (expressed as ml min g) between lung volumes in the gravitationally intermediate (RV = 8.9 ± 3.1, FRC = 8.1 ± 2.9, TLC = 7.4 ± 3.6; P= 0.26) and dependent lung (RV = 6.6 ± 2.4, FRC = 6.1 ± 2.1, TLC = 6.4 ± 2.6; P= 0.51). However, at TLC perfusion was significantly lower in non-dependent lung than at FRC or RV (3.6 ± 3.3, 7.7 ± 1.5, 7.9 ± 2.0, respectively; P < 0.001). These data suggest that the mechanism of the reduction in perfusion in dependent lung is unlikely to be a result of lung volume related increases in resistance in extra-alveolar vessels. In supine posture, the gravitational influence on perfusion is remarkably similar over most of the lung, irrespective of lung volume. The lung is subject to multiple influences that affect its function. In particular the effect of gravity has attracted considerable interest, especially as it relates to the distribution of blood flow. In the most gravitationally dependent part of the lung, blood flow is reduced, and this region is known as Zone 4. Zone 4 has been suggested to result from increased resistance in some of the blood vessels, and this effect is thought to be the smallest when the lung is at a high volume as the elastic structures of the lung hold the vessels open minimizing resistance. Using novel magnetic resonance imaging techniques to measure blood flow, this study shows that the distribution of blood flow in the dependent lung is unchanged when the lung volume is changed and suggests that the intrinsic structure of the vessels is a more likely explanation for this behaviour. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate lung water density at three different levels of lung inflation in normal lungs using a fast gradient echo sequence developed for rapid imaging.Materials and Methods: Ten healthy volunteers were imaged with a fast gradient echo sequence that collects 12 images alternating between two closely spaced echoes in a single 9-s breathhold. Data were fit to a single exponential to determine lung water density and T(2) (*). Data were evaluated in a single imaging slice at total lung capacity (TLC), functional residual capacity (FRC), and residual volume (RV). Analysis of variance for repeated measures was used to statistically evaluate changes in T(2) (*) and lung water density across lung volumes, imaging plane, and spatial locations in the lung.Results: In normal subjects (n = 10), T(2) (*) (and [lung density/water density]) was 1.2 +/- 0.1 msec (0.10 +/- 0.02), 1.8 +/- 0.2 ms (0.25 +/- 0.04), and 2.0 +/- 0.2 msec (0.27 +/- 0.03) at TLC, FRC, and RV, respectively. Results also show that there is a considerable intersubject variability in the values of T(2) (*).Conclusion: Data show that T(2) (*) in the lung is very short, and varies considerably with lung volume. Thus, if quantitative assessment of lung density within a breathhold is to be measured accurately, then it is necessary to also determine T(2) (*). [ABSTRACT FROM AUTHOR]

Acetazolamide (ACZ) is used to prevent acute mountain sickness at altitude. Because it could affect O2 transport in several different and potentially conflicting ways, we examined its effects on pulmonary and muscle gas exchange and acid–base status during cycle exercise at ∼30, 50 and 90% in normoxia and acute hypoxia . In a double-blind, order-balanced, crossover design, six healthy, trained men (normoxic = 59 ml kg−1 min−1) exercised at both values after ACZ (3 doses of 250 mg, 8 h apart) and placebo. One week later this protocol was repeated using the other drug (placebo or ACZ). We measured cardiac output , leg blood flow (LBF), and muscle and pulmonary gas exchange, the latter using the multiple inert gas elimination technique. ACZ did not significantly affect , , LBF or muscle gas exchange. As expected, ACZ led to lower arterial and venous blood [HCO3−], pH and lactate levels ( P < 0.05), and increased ventilation ( P < 0.05). In both normoxia and hypoxia, ACZ resulted in higher arterial PO2 and saturation and a lower alveolar–arterial PO2 difference (Aa DO2) due to both less mismatch and less diffusion limitation ( P < 0.05). In summary, ACZ improved arterial oxygenation during exercise, due to both greater ventilation and more efficient pulmonary gas exchange. However, muscle gas exchange was unaffected. [ABSTRACT FROM AUTHOR]