Lung Air Volume Research Articles

Regional Pulmonary Ventilation Assessment Method and System Based on Impedance Sensing Information from the Pentapulmonary Lobes

Regional lung ventilation assessment is a critical tool for the early detection of lung diseases and postoperative evaluation. Biosensor-based impedance measurements, known for their non-invasive nature, among other benefits, have garnered significant attention compared to traditional detection methods that utilize pressure sensors. However, solely utilizing overall thoracic impedance fails to accurately capture changes in regional lung air volume. This study introduces an assessment method for lung ventilation that utilizes impedance data from the five lobes, develops a nonlinear model correlating regional impedance with lung air volume, and formulates an approach to identify regional ventilation obstructions based on impedance variations in affected areas. The electrode configuration for the five lung lobes was established through numerical simulations, revealing a power–function nonlinear relationship between regional impedance and air volume changes. An analysis of 389 pulmonary function tests refined the equations for calculating pulmonary function parameters, taking into account individual differences. Validation tests on 30 cases indicated maximum relative errors of 0.82% for FVC and 0.98% for FEV1, all within the 95% confidence intervals. The index for assessing regional ventilation impairment was corroborated by CT scans in 50 critical care cases, with 10 validation trials showing agreement with CT lesion localization results.

A Novel Ultrasound Imaging Assistance UI: Using Marker‐Based Coordinate System for Real‐Time Breathing Monitoring and Probe Positioning

Ultrasound is widely employed in medical examinations due to its noninvasive, radiation‐free, and convenient features. However, the quality of acquired ultrasound images is highly dependent on the skill of the operator and experience, which significantly limits the use of ultrasound. In this study, we propose a new user interface (UI) designed to assist novices in independently acquiring accurate ultrasound images. The operator can complete image acquisition by adjusting the position and angle of the actual probe to align the projected probe on the UI screen to a specific position, while simultaneously observing the breath state of the subject to capture ultrasound images at the appropriate position and moment. We compare our UI with a previous UI in an experiment. The results demonstrate that novice operators can acquire more accurate ultrasound images using our UI compared to the previous UI, indicating that our UI offers improved guidance. Regarding breath state observation, the experiment reveals a strong association between changes in lung air volume of a subject and respiratory level changes measured by our system. © 2024 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Application-specific approaches to MicroCT for evaluation of mouse models of pulmonary disease.

The advent of micro-computed tomography (microCT) has provided significant advancement in our ability to generate clinically relevant assessments of lung health and disease in small animal models. As microCT use to generate outcomes analysis in pulmonary preclinical models has increased there have been substantial improvements in image quality and resolution, and data analysis software. However, there are limited published methods for standardized imaging and automated analysis available for investigators. Manual quantitative analysis of microCT images is complicated by the presence of inflammation and parenchymal disease. To improve the efficiency and limit user-associated bias, we have developed an automated pulmonary air and tissue segmentation (PATS) task list to segment lung air volume and lung tissue volume for quantitative analysis. We demonstrate the effective use of the PATS task list using four distinct methods for imaging, 1) in vivo respiration controlled scanning using a flexiVent, 2) longitudinal breath-gated in vivo scanning in resolving and non-resolving pulmonary disease initiated by lipopolysaccharide-, bleomycin-, and silica-exposure, 3) post-mortem imaging, and 4) ex vivo high-resolution scanning. The accuracy of the PATS task list was compared to manual segmentation. The use of these imaging techniques and automated quantification methodology across multiple models of lung injury and fibrosis demonstrates the broad applicability and adaptability of microCT to various lung diseases and small animal models and presents a significant advance in efficiency and standardization of preclinical microCT imaging and analysis for the field of pulmonary research.

Accurate measures of changes in regional lung air volumes from chest x-rays of small animals

Objective. To develop a robust technique for calculating regional volume changes within the lung from x-ray radiograph sequences captured during ventilation, without the use of computed tomography (CT). Approach. This technique is based on the change in transmitted x-ray intensity that occurs for each lung region as air displaces the attenuating lung tissue. Main results. Lung air volumes calculated from x-ray intensity changes showed a strong correlation (R 2 = 0.98) against the true volumes, measured from high-resolution CT. This correlation enables us to accurately convert projected intensity data into relative changes in lung air volume. We have applied this technique to measure changes in regional lung volumes from x-ray image sequences of mechanically ventilated, recently-deceased newborn rabbits, without the use of CT. Significance. This method is suitable for biomedical research studies,enabling quantitative regional measurement of relative lung air volumes at high temporal resolution, and shows great potential for future clinical application.

Quantifying lung aeration in neonatal lambs at birth using lung ultrasound.

BackgroundLung ultrasound (LUS) is a safe and non-invasive tool that can potentially assess regional lung aeration in newborn infants and reduce the need for X-ray imaging. LUS produces images with characteristic artifacts caused by the presence of air in the lung, but it is unknown if LUS can accurately detect changes in lung air volumes after birth. This study compared LUS images with lung volume measurements from high-resolution computed tomography (CT) scans to determine if LUS can accurately provide relative measures of lung aeration.MethodsDeceased near-term newborn lambs (139 days gestation, term ∼148 days) were intubated and the chest imaged using LUS (bilaterally) and phase contrast x-ray CT scans at increasing static airway pressures (0–50 cmH2O). CT scans were analyzed to calculate regional air volumes and correlated with measures from LUS images. These measures included (i) LUS grade; (ii) brightness (mean and coefficient of variation); and (iii) area under the Fourier power spectra within defined frequency ranges.ResultsAll LUS image analysis techniques correlated strongly with air volumes measured by CT (p < 0.01). When imaging statistics were combined in a multivariate linear regression model, LUS predicted the proportion of air in the underlying lung with moderate accuracy (95% prediction interval ± 22.15%, r2 = 0.71).ConclusionLUS can provide relative measures of lung aeration after birth in neonatal lambs. Future studies are needed to determine if LUS can also provide a simple means to assess air volumes and individualize aeration strategies for critically ill newborns in real time.

Artificial Bee Colony Algorithm-Based Ultrasound Image Features in the Analysis of the Influence of Different Anesthesia Methods on Lung Air Volume in Orthopedic Surgery Patients

This study aimed to provide a quantitative evaluation of the lung gas content in orthopedic surgery patients under different anesthesia using ultrasound images based on the artificial bee colony algorithm. The ultrasound image features based on an artificial bee colony algorithm were applied to analyze segmentation images to investigate the influence of different anesthesia methods on the lung air content of patients undergoing orthopedic surgery and the clinical features of such patients. They were also adopted for the anesthesia in orthopedic surgery to assist clinicians in the diagnosis of diseases. 160 orthopedic surgery patients who were hospitalized were treated with different anesthesia methods. The first group (traditional general anesthesia group) received general anesthesia and traditional ultrasound; the second group (ABC general anesthesia group) was used for ultrasound image analysis based on the artificial bee colony algorithm; the third group (traditional sclerosis group) was anesthetized with combined sclerosis block; ultrasound images of patients from the fourth group (ABC sclerosis group) were analyzed based on the artificial bee colony algorithm. Analysis was conducted at three time points. The LUS score of the traditional sclerosis group and ABC sclerosis group was hugely higher than the score of the traditional general anesthesia group and ABC general anesthesia group at T2 time, with statistical significance ( P &lt; 0.005 ). At time point T3, the score of the traditional sclerosis group rose greatly compared with the general anesthesia group, and that of the ABC group was generally higher than that of the traditional ultrasound group ( P &lt; 0.005 ). When the threshold value was 4, the fitness value of ABC algorithm was 2680.4461, and the fitness value of the control group was 1736.815. The difference between the two groups was 943.6311 ( P &lt; 0.05 ). The operation time of ABC algorithm was 1.83, while that of the control group was 1.05, and the difference between the two groups was 0.78 ( P &lt; 0.05 ). In conclusion, the feature analysis of ultrasonic images based on the artificial bee colony algorithm could effectively improve the accuracy of ultrasonic images and the accuracy of focus recognition. It can promote medical efficiency and accurately identify the lung air content of patients in future clinical case measurement and auxiliary treatment of fracture, which has great application potential in improving surgical anesthesia effect.

Abstract 264: Automatic Detection of Ventilations Using the Thoracic Impedance Signal During Lucas Chest Compressions

Introduction: Resuscitation from out-of-cardiac arrest (OHCA) requires control of both chest compressions and lung ventilation. There are few effective methods for detecting ventilations during cardiopulmonary resuscitation. Thoracic impedance (TI) is sensitive to changes in lung air volumes and may allow detection of ventilations but has not been tested with concurrent mechanical chest compressions. Hypothesis: It is possible to automatically detect and characterize ventilations from TI changes during mechanical chest compressions. Methods: A cohort of 420 OHCA cases (27 survivors to hospital discharge) were enrolled in the Dallas-Fort Worth Center for Resuscitation Research cardiac arrest registry. These patients were treated with the LUCAS-2 CPR device and had concurrent TI and capnogram recordings from MRx (Philips, Andover, MA) monitor-defibrillators. We developed a signal processing algorithm to suppress chest compression artifacts from the TI signal, allowing identification of ventilations. We used the capnogram as gold standard for delivered ventilations. We determined the accuracy of the algorithm for detecting capnogram-indicated ventilations, calculating sensitivity, the proportion of true ventilations detected in the TI, and positive predictive value (PPV), the proportion of true ventilations within the detections. We calculated per minute ventilation rate and mean TI amplitude, as surrogate for tidal volume. Statistical differences between survivors and non-survivors were assessed using the Mann-Whitney test. Results: We studied 4331 minutes of TI during CPR. There were a median of 10 (IQR 6-14) ventilations per min and 52 (30-81) ventilations per patient. Sensitivity of TI was 95.9% (95% CI, 74.5-100), and PPV was 95.8% (95% CI, 80.0-100). The median ventilation rates for survivors and non-survivors were 7.75 (5.37-9.91) min -1 and 5.64 (4.46-7.15) min -1 (p&lt;10 -3 ), and the median TI amplitudes were 1.33 (1.03-1.75) Ω and 1.14 (0.77-1.66) Ω (p=0.095). Conclusions: An accurate automatic TI ventilation detection algorithm was demonstrated during mechanical CPR. The relation between ventilation rate during mechanical CPR and survival was significant, but it was not for impedance amplitude.

Regional Lung Recruitability During Pneumoperitoneum Depends on Chest Wall Elastance - A Mechanical and Computed Tomography Analysis in Rats.

Background: Laparoscopic surgery with pneumoperitoneum increases respiratory system elastance due to the augmented intra-abdominal pressure. We aim to evaluate to which extent positive end-expiratory pressure (PEEP) is able to counteract abdominal hypertension preventing progressive lung collapse and how rib cage elastance influences PEEP effect.Methods: Forty-four Wistar rats were mechanically ventilated and randomly assigned into three groups: control (CTRL), pneumoperitoneum (PPT) and pneumoperitoneum with restricted rib cage (PPT-RC). A pressure-volume (PV) curve followed by a recruitment maneuver and a decremental PEEP trial were performed in all groups. Thereafter, animals were ventilated using PEEP of 3 and 8 cmH2O divided into two subgroups used to evaluate respiratory mechanics or computed tomography (CT) images. In 26 rats, we compared respiratory system elastance (Ers) at the two PEEP levels. In 18 animals, CT images were acquired to calculate total lung volume (TLV), total volume and air volume in six anatomically delimited regions of interest (three along the cephalo-caudal and three along the ventro-dorsal axes).Results: PEEP of minimal Ers was similar in CTRL and PPT groups (3.8 ± 0.45 and 3.5 ± 3.89 cmH2O, respectively) and differed from PPT-RC group (9.8 ± 0.63 cmH2O). Chest restriction determined a right- and downward shift of the PV curve, increased Ers and diminished TLV and lung aeration. Increasing PEEP augmented TLV in CTRL group (11.8 ± 1.3 to 13.6 ± 2 ml, p < 0.05), and relative air content in the apex of PPT group (3.5 ± 1.4 to 4.6 ± 1.4% TLV, p < 0.03) and in the middle zones in PPT-RC group (21.4 ± 1.9 to 25.3 ± 2.1% TLV cephalo-caudally and 18.1 ± 4.3 to 22.0 ± 3.3% TLV ventro-dorsally, p < 0.005).Conclusion: Regional lung recruitment potential during pneumoperitoneum depends on rib cage elastance, reinforcing the concept of PEEP individualization according to the patient’s condition.

The influence of a high fat diet on bone and soft tissue formation in Matrix Gla Protein knockout mice

Studies suggest bone growth and development are influenced by maternal nutrition, during intrauterine and early postnatal life. This study assessed the role of MGP and a maternal high fat diet on vitamin K-dependent proteins’ gene expression and their impact on bone formation. Knockout (KO) offspring were smaller than wild type (WT) littermates, yet possessed the same volume of intrascapular brown adipose tissue. The total proportion of body fat was reduced, but only in animals on a control diet. Lung air volume was observed to be comparable in both KO and WT animals on the same diet. The degree of aortic calcification was reduced in KO animals maintained on a HF diet. KO females on the high fat diet showed reduced cortical bone volume and thickness in the femur and tibia. Gene expression levels of GGCX and VKOR were reduced in control fed KO animals suggesting a potential link between gene expression levels of MGP, GGCX, and VKOR and total volumes of bone, calcified soft tissue, and iBAT; with implications for modulation of body length and mass. Our results confirm the important role for vitamin K in bone and calcified soft tissue, but now extend this role to include iBAT.

Limitations and challenges of EIT-based monitoring of stroke volume and pulmonary artery pressure

Objective: Electrical impedance tomography (EIT) shows potential for radiation-free and noninvasive hemodynamic monitoring. However, many factors degrade the accuracy and repeatability of these measurements. Our goal is to estimate the impact of this variability on the EIT-based monitoring of two important central hemodynamic parameters: stroke volume (SV) and pulmonary artery pressure (PAP). Approach: We performed simulations on a 4D () bioimpedance model of a human volunteer to study the influence of four potential confounding factors (electrode belt displacement, electrode detachment, changes in hematocrit and lung air volume) on the performance of EIT-based SV and PAP estimation. Results were used to estimate how these factors affect the EIT measures of either absolute values or relative changes (i.e. trending). Main results: Our findings reveal that the absolute measurement of SV via EIT is very sensitive to electrode belt displacements and lung conductivity changes. Nonetheless, the trending ability of SV EIT might be a promising alternative. The timing-based measurement of PAP is more robust to lung conductivity changes but sensitive to longitudinal belt displacements at severe hypertensive levels and to rotational displacements (independent of the PAP level). Significance: We identify and quantify the challenges of EIT-based SV and PAP monitoring. Absolute SV via EIT is challenging, but trending is feasible, while both the absolute and trending of PAP via EIT are mostly impaired by belt displacements.

Sports-related lung injury during breath-hold diving.

The number of people practising recreational breath-hold diving is constantly growing, thereby increasing the need for knowledge of the acute and chronic effects such a sport could have on the health of participants. Breath-hold diving is potentially dangerous, mainly because of associated extreme environmental factors such as increased hydrostatic pressure, hypoxia, hypercapnia, hypothermia and strenuous exercise.In this article we focus on the effects of breath-hold diving on pulmonary function. Respiratory symptoms have been reported in almost 25% of breath-hold divers after repetitive diving sessions. Acutely, repetitive breath-hold diving may result in increased transpulmonary capillary pressure, leading to noncardiogenic oedema and/or alveolar haemorrhage. Furthermore, during a breath-hold dive, the chest and lungs are compressed by the increasing pressure of water. Rapid changes in lung air volume during descent or ascent can result in a lung injury known as pulmonary barotrauma. Factors that may influence individual susceptibility to breath-hold diving-induced lung injury range from underlying pulmonary or cardiac dysfunction to genetic predisposition.According to the available data, breath-holding does not result in chronic lung injury. However, studies of large populations of breath-hold divers are necessary to firmly exclude long-term lung damage.

Towards computer based lung disease diagnosis using accurate lung air segmentation of CT images in exhalation and inhalation phases

Lung air estimation using non-invasive techniques can be used for assessment of the lung function and effective diagnosis of lung disease (e.g. chronic obstructive pulmonary disease). A novel technique is proposed to automatically estimate the lung air volume and its variations throughout respiration cycle using 4D thoracic CT images. The technique is based on an advanced thresholding method which benefits from parenchyma tissue mechanical properties in addition to the lung image data over the respiration cycle to determine the segmentation threshold values. This led to an optimization framework which was developed to find optimal values of the segmentation threshold. In general, image intensity of each voxel in a lung CT image is the intensity resultant of tissue and air within the voxel. This gives rise to the known partial volume effect. An important feature of the proposed technique is its treatment of this effect to improve the volume estimation accuracy. For this purpose, voxels’ Air Volume Portion Coefficients (AVPCs) are calculated then multiplied by corresponding voxel size and voxel number which is determined using the optimization algorithm. The technique was applied to CT scans of ex vivo porcine lung and to lung images of COPD patients. Results indicate that the air volume estimated using the proposed method is significantly more accurate when AVPCs are used in the air volume estimation as errors of only ∼ 1% and less than 6.7% were obtained in the ex vivo lung and patient studies, respectively. Moreover, the proposed method demonstrates a robust performance for low resolution CT images where accuracy of other methods is known to decrease. The performance characteristics of the proposed method, including being completely image based, fully automatic combined with its demonstrated high accuracy makes it a strong candidate to complement/replace pulmonary function diagnostic tests that involve experimental measurement of function parameters. Moreover, being fully computational without involving any manual steps indicates its adaptability to be utilized as a core component within an effective expert system framework for lung disease diagnosis.

Chronic Hypoxia Accentuates Dysanaptic Lung Growth.

Adults born and raised at high altitudes have larger lung volumes and greater pulmonary diffusion capacity compared with adults at low altitude; however, it remains unclear whether the air and tissue volumes have comparable increases and whether there is a difference in airway size. To assess the effect of chronic hypoxia on lung growth using in vivo high-resolution computed tomography measurements. Healthy adults born and raised at moderate altitude (2,000 m above sea level; n = 19) and at low altitude (400 m above sea level; n = 23) underwent high-resolution computed tomography. Differences in total lung, air, and tissue volume, mean lung density, as well as airway lumen and wall areas in anatomically matched airways were compared between groups. No significant differences for age, sex, weight, or height were found between the two groups (P > 0.05). In a multivariate regression model, altitude was a significant contributor for total lung volume (P = 0.02), air volume (P = 0.03), and tissue volume (P = 0.03), whereby the volumes were greater for the moderate- versus the low-altitude group. However, altitude was not a significant contributor for mean lung density (P = 0.35) or lumen and wall areas in anatomically matched segmental, subsegmental, and subsubsegmental airways. Our findings suggest that the adult lung did not increase lung volume later in life by expansion of an existing number of alveoli, but rather from increased alveolarization early in life. In addition, chronic hypoxia accentuates dysanaptic lung growth by increasing the lung parenchyma but not the airways.

Microcomputed tomography assessment of lipopolysaccharide-induced acute lung injury in rat

ABSTRACTPurpose: High-resolution microcomputed tomography (micro-CT) is an extremely flexible and accurate technique for three-dimensional examination of biological tissues. The aim was to evaluate the feasibility of micro-CT as a noninvasive tool for analyzing the lung structure during lipopolysaccharide (LPS)-induced acute lung injury (ALI) in rats. Materials and Methods: ALI was induced in rats by intratracheal instillation of LPS (2 mg/kg) in 0.3 ml saline, and the control treatment consisted of intratracheal instillation of an equal volume of normal saline. Morphological changes were assessed by using micro-CT and a light microscope at 24 and 48 hours after LPS instillation. Total volume is the sum of all pixels marked as the whole lung and total air volume (Air V) is the sum volume of all air in the lung. Results: The saline groups exhibited no major histological abnormalities, whereas the LPS groups exhibited patchy areas of haemorrhage and thickened alveolar walls with inflammatory cell infiltration at 24 and 48 hours. The LPS groups had significantly smaller Air V and percent total air volume (Air V/TV) compared with those of the saline groups at 24 and 48 hours. Air V/TV was strongly negatively correlated with the lung injury score (r = −0.641, P = .004). Conclusions: Micro-CT is a feasible tool for evaluating the lung structure and lung injury progression during LPS-induced ALI.

Wearable lung-health monitoring system with electrical impedance tomography.

The wearable lung-health monitoring system is proposed with an electrical impedance tomography (EIT). The proposed system has light belt-type form factor which is implemented with the EIT integrated circuit (IC) on the planar-fashionable circuit board (P-FCB) technology. The EIT IC provides programmable current stimulation which is optimally controlled by the results of contact impedance monitoring. The measured data is transmitted to the mobile device and the lung EIT images are reconstructed and displayed with up to 20 frames/s real-time. From the lung EIT image, the measured lung air volume ratio can be used as an indicator of the lung-health, and other various parameters can be extracted to monitor lung status. The proposed wearable system achieves the user convenience for lung-health monitoring which can be used personally at home. The proposed system is fully implemented and verified on both in-vitro and in-vivo tests.

SU‐E‐I‐90: Characterizing Small Animal Lung Properties Using Speckle Observed with An In‐Line X‐Ray Phase Contrast Benchtop System

Purpose:We demonstrate a novel X‐ray phase‐contrast (XPC) method for lung imaging representing a paradigm shift in the way small animal functional imaging is performed. In our method, information regarding airway microstructure that is encoded within speckle texture of a single XPC radiograph is decoded to produce 2D parametric images that will spatially resolve changes in lung properties such as microstructure sizes and air volumes. Such information cannot be derived from conventional lung radiography or any other 2D imaging modality. By computing these images at different points within a breathing cycle, dynamic functional imaging will be readily achieved without the need for tomography. Methods: XPC mouse lung radiographs acquired in situ with an in‐line X‐ray phase contrast benchtop system. The lung air volume is varied and controlled with a small animal ventilator. XPC radiographs will be acquired for various lung air volume levels representing different phases of the respiratory cycle. Similar data will be acquired of microsphere‐based lung phantoms containing hollow glass spheres with known distributions of diameters. Image texture analysis is applied to the data to investigate relationships between texture characteristics and airspace/microsphere physical properties.Results:Correlations between Fourier‐based texture descriptors (FBTDs) and regional lung air volume indicate that the texture features in 2D radiographs reveal information on 3D properties of the lungs. For example, we find for a 350 × 350 πm2 lung ROI a linear relationship between injected air volume and FBTD value with slope and intercept of 8.9×105 and 7.5, respectively.Conclusion:We demonstrate specific image texture measures related to lung speckle features are correlated with physical characteristics of refracting elements (i.e. lung air spaces). Furthermore, we present results indicating the feasibility of implementing the technique with a simple imaging system design, short exposures, and low dose which provides potential for widespread use in laboratory settings for in vivo studies.This research was supported in part by NSF Award CBET1263988.

Determination of regional lung air volume distribution at mid-tidal breathing from computed tomography: a retrospective study of normal variability and reproducibility.

BackgroundDetermination of regional lung air volume has several clinical applications. This study investigates the use of mid-tidal breathing CT scans to provide regional lung volume data.MethodsLow resolution CT scans of the thorax were obtained during tidal breathing in 11 healthy control male subjects, each on two separate occasions. A 3D map of air volume was derived, and total lung volume calculated. The regional distribution of air volume from centre to periphery of the lung was analysed using a radial transform and also using one dimensional profiles in three orthogonal directions.ResultsThe total air volumes for the right and left lungs were 1035 +/− 280 ml and 864 +/− 315 ml, respectively (mean and SD). The corresponding fractional air volume concentrations (FAVC) were 0.680 +/− 0.044 and 0.658 +/− 0.062. All differences between the right and left lung were highly significant (p < 0.0001). The coefficients of variation of repeated measurement of right and left lung air volumes and FAVC were 6.5% and 6.9% and 2.5% and 3.6%, respectively. FAVC correlated significantly with lung space volume (r = 0.78) (p < 0.005). FAVC increased from the centre towards the periphery of the lung. Central to peripheral ratios were significantly higher for the right (0.100 +/− 0.007 SD) than the left (0.089 +/− 0.013 SD) (p < 0.0001).ConclusionA technique for measuring the distribution of air volume in the lung at mid-tidal breathing is described. Mean values and reproducibility are described for healthy male control subjects. Fractional air volume concentration is shown to increase with lung size.

Controlled, Parametric, Individualized, 2D and 3D Imaging Measurements of Aerosol Deposition in the Respiratory Tract of Healthy Human Volunteers:In VivoData Analysis

To provide a validation dataset for aerosol deposition modeling, a clinical trial was performed in which the inhalation parameters and the inhaled aerosol were controlled or characterized. Eleven, healthy, never-smokers, male participants completed the study. Each participant performed two inhalations of (99m)Tc-labeled aerosol from a vibrating mesh nebulizer, which differed by a single controlled parameter (aerosol particle size: "small" or "large"; inhalation: "deep" or "shallow"; carrier gas: air or a helium-oxygen mix). The deposition measurements were made by planar imaging, and single photon emission computed tomography-computed tomography (SPECT-CT). The difference between the mean activity measured by two-dimensional imaging and that delivered from the nebulizer was 2.7%, which was not statistically significant. The total activity deposited was significantly lower in the left lung than in the right lung (p<0.0001) with a mean ratio (left/right) of 0.87±0.1 standard deviation (SD). However, when normalized to lung air volume, the left lung deposition was significantly higher (p=0.0085) with a mean ratio of 1.08±0.12 SD. A comparison of the three-dimensional central-to-peripheral (nC/P3D) ratio showed that it was significantly higher for the left lung (p<0.0001) with a mean ratio (left/right) of 1.36±0.20 SD. The effect of particle size was statistically significant on the nC/P3D ratio (p=0.0014), extrathoracic deposition (p=0.0037), and 24-hr clearance (p<0.0001), contrary to the inhalation parameters, which showed no effect. This article presents the results of an analysis of the in vivo deposition data, obtained in a clinical study designed to provide data for model validation. This study has demonstrated the value of SPECT imaging over planar, the influence of particle size on regional distribution within the lung, and differences in deposition between the left and right lungs.

GPU accelerated regional lung air volume measurements from phase contrast X-ray images

Phase contrast X-ray imaging can provide significantly enhanced visibility of soft tissues over absorption contrast imaging with spatial resolution on the micron scale. These characteristics have enabled the visualisation of lungs aerating at birth in real time. We have developed techniques to measure regional lung air volume from these images to help develop methods for safely ventilating the lungs of preterm infants. However, analyzing a large sequence of image data requires considerable computation time on traditional desktop computers. Real-time feedback of the regional ventilation would greatly benefit researches to optimize ventilation strategies. The present paper describes methods for improving the execution time of the lung volume measurements using graphics processing units (GPUs). We tested the performance of the GPU-accelerated lung volume computations using two different GPUs and compared the results with two CPUs. An overall speedup of 1.75---14.12× was achieved if an absorption contrast-based computation was used for volumetric computation, while a 2.43---15.78× speedup was attained in the case of a more compute bound phase retrieval technique. This speedup enabled us to perform lung air volume reconstruction on a local computer with the analysis taking only a few minutes, which is very helpful to guide our experiments in the laboratory. We also show that the accuracy of the GPU-based lung volume measurements was in excellent agreement with the CPU-based counterpart.

Measurement of absolute regional lung air volumes from near-field x-ray speckles

Propagation-based phase contrast x-ray (PBX) imaging yields high contrast images of the lung where airways that overlap in projection coherently scatter the x-rays, giving rise to a speckled intensity due to interference effects. Our previous works have shown that total and regional changes in lung air volumes can be accurately measured from two-dimensional (2D) absorption or phase contrast images when the subject is immersed in a water-filled container. In this paper we demonstrate how the phase contrast speckle patterns can be used to directly measure absolute regional lung air volumes from 2D PBX images without the need for a water-filled container. We justify this technique analytically and via simulation using the transport-of-intensity equation and calibrate the technique using our existing methods for measuring lung air volume. Finally, we show the full capabilities of this technique for measuring regional differences in lung aeration.