Aerosol Ventilation Research Articles

Measuring Anatomical Distributions of Ventilation and Aerosol Deposition with PET-CT.

In disease, lung function and structure are heterogeneous, and aerosol transport and local deposition vary significantly among parts of the lung. Understanding such heterogeneity is relevant to aerosol medicine and for quantifying mucociliary clearance from different parts of the lung. In this chapter, we describe positron emission tomography (PET) imaging methods to quantitatively assess the deposition of aerosol and ventilation distribution within the lung. The anatomical information from computed tomography (CT) combined with the PET-deposition data allows estimates of airway surface concentration and peripheral tissue dosing in bronchoconstricted asthmatic subjects. A theoretical framework is formulated to quantify the effects of heterogeneous ventilation, uneven aerosol ventilation distribution in bifurcations, and varying escape from individual airways along a path of the airway tree. The framework is applied to imaging data from bronchoconstricted asthmatics to assess the contributions of these factors to the unevenness in lobar deposition. Results from this analysis show that the heterogeneity of ventilation contributes on average to more than one-third of the variability in interlobar deposition. Actual contribution of ventilation in individual lungs was variable and dependent on the breathing rate used by the subject during aerosol inhalation; the highest contribution was in patients breathing slowly. In subjects breathing faster, contribution of ventilation was reduced, with more expanded lobes showing lower deposition per unit ventilation than less expanded ones in these subjects. The lobar change in expansion measured from two static CT scans, which is commonly used as a surrogate for ventilation, did not correlate with aerosol deposition or with PET-measured ventilation. This suggests that dynamic information is needed to provide proper estimates of ventilation for asthmatic subjects. We hope that the enhanced understanding of the causes of heterogeneity in airway and tissue dosing using the tools presented here will help to optimize therapeutic effectiveness of inhalation therapy while minimizing toxicity.

Development of a method for measuring and visualizing the concentration of aerosol particles using flame photometry

It has been pointed out that SARS-CoV-2, the cause of COVID-19, can cause droplet or droplet nucleus infection by aerosol particles. Therefore, there is a growing need for a method to investigate the behavior of aerosol particles. Currently, it is impossible to visualize aerosol particles and measure their concentration simultaneously. In this study, a method for measuring and visualizing the concentration of aerosol particles by flame photometry was developed. In this method, aerosol consisting of a sodium chloride solution is used as tracers for human-droplet and droplet nuclei, and the amount of sodium in the aerosol particles is determined by the flame color reaction of a burner. Experiments using the developed method showed that the aerosol can be visualized by the flame color reaction and showed the same trend as that of a particle counter, indicating that the amount of aerosol can be measured using this method. This study suggests that this method may be applied to evaluate the effectiveness of aerosol ventilation, propose appropriate ventilation methods, and improve the accuracy of CFD simulations.

Nondestructive Compression and Fluidization of Phospholipid Monolayers by Gaseous and Aerolized Perfluorocarbons: Promising Substances for Lung Surfactant Treatment.

We present a surface-sensitive X-ray scattering study on the influence of gaseous and aerolized perfluorocarbons (FCs) on zwitterionic and anionic phospholipid Langmuir films, which serve as a simplified model system of lung surfactants. It was found that small gaseous FC molecules like F-propane and F-butane penetrate phospholipid monolayers and accumulate between the alkyl chains and form islands. This clustering process can trigger the formation of lipid crystallites at low initial surface pressures. In contrast, the large linear FC F-octyl bromide fluidizes membranes, causing a dissolution of crystalline domains. The bicyclic FC F-decalin accumulates between the alkyl chains of 1,2-dipalmitoyl phosphatidylcholine but cannot penetrate the more densely packed 1,2-dipalmitoyl phosphatidic acid films because of its size. The effects of FCs on lung surfactants are discussed in the framework of currently proposed therapeutic methods for acute respiratory distress syndrome using FC gases, vapor, or aerosol ventilation causing monolayer fluidization effects. This study implies that the highly biocompatible and nontoxic FCs could be beneficial in the treatment of lung diseases with injured nonfunctional lung surfactants in a novel approach for ventilation.

Refinement and testing of the drift-flux model for indoor aerosol dispersion and deposition modelling

The drift-flux approach for predicting aerosol deposition within enclosed spaces has been refined and implemented within a commercial computational fluid dynamics (CFD) solver. The drift-flux model is tested against a previously reported study of aerosol deposition within a ventilated chamber to illustrate the performance of the approach for unsteady particle concentrations. The model has been made more general by accounting for deposition to surfaces at any angle to the gravitational vector. The algorithms for the calculation of the deposition velocity have been revised to offer improved precision. The model shows good performance when compared with the measured particle concentration decay rates. Comparison with well-mixed models shows obvious differences from the measured and drift-flux CFD approach. The dependence of point concentration measurements of decay rates on sampling time is explored and the limitations for estimating steady-state deposition behaviour are highlighted. An important aspect of aerosol ventilation of incompletely mixed enclosed spaces is illustrated. The drift-flux approach is shown to perform very well at reproducing the unsteady particle concentration decay observed.

Evaluation of Residual Functional Lung Volume on Tc-99m DTPA Aerosol Ventilation and Tc-99m MAA Perfusion Scintigraphy in Primary Ciliary Dyskinesia (Kartagener Syndrome)

Kartagener syndrome is diagnosed as sinusitis, bronchitis (bronchiectasis), and situs inversus by the clinical features. It is a subclass of primary ciliary dyskinesia (PCD) disease. A 12-year-old girl who had frequent upper and lower airway infections since birth, which was confirmed as Kartagener syndrome by HRCT imaging. We present the residual functional lung volume and mucociliary clearance findings seen on Tc-99m DTPA aerosol ventilation and Tc-99m MAA perfusion scintigraphy.

Facilitation of Aerosol Ventilation Scanning for Diagnosis of Pulmonary Emboli in Uncooperative Dyspneic Patients

Acute pulmonary thromboembolism (PE) is a common cause of death in hospital patients. Quick and accurate diagnosis significantly decreases mortality. Many medical facilities still have ventilation/perfusion lung scans as the only available and preferred screening test for suspected PE. Although testing requires the patient's cooperation, many patients with PE are dyspneic and uncooperative.This case report illustrates a novel method of obtaining high-quality radionuclide aerosol ventilation scintigraphs in uncooperative patients by means of an easy to use hood (BabyAir; BabyBreath, Or Akiva, Israel). There is no need for patients to neither undertake difficult breathing maneuvers nor to use a mouth-piece or mask.

P31 Comparison of the practicability and image quality of the SmartVent and Swirler aerosol ventilation systems

P31 Comparison of the practicability and image quality of the SmartVent and Swirler aerosol ventilation systems

Post-Test Probability for Pulmonary Embolism after Ventilation-Perfusion Scan Assessed by Nuclear Medicine Physicians

Objective: The objective of this prospective study was to compare assessments of pre- and post-ventilation-perfusion (V/Q) scan probabilities for pulmonary embolism (PE) by the nuclear medicine physician and the referring physician. Materials and Methods: Seventy-nine patients (41 females, 38 males, mean age 49 years) referred for V/Q scans over a period of 6 months and suspected of PE were included in the study. The pre-test likelihood was determined independently by a consultant nuclear physician and a referring physician prior to the V/Q scan. The scan was performed according to a standard protocol using 8 view technetium-99m diethylenetriamine pentaacetic acid aerosol ventilation study followed by a technetium-99m macroaggregated albumin perfusion study. The scan was interpreted according to prospective investigation of pulmonary embolism diagnosis criteria. The post-scan probability was calculated. The probability of PE was quoted as low, intermediate and high. Agreement or disagreement in assessing the pre- and post-scan probability was classified according to the degree of difference (no difference: 0; minor difference: 1, and major difference: 2 grades). Results: The agreement between the nuclear medicine and referring physicians on clinical probability of PE was moderate (63%) before the scan and good (90%) after the scan. The disagreement in assessing the clinical probability between the referring physician and the nuclear medicine physician was predominantly minor. Only 5 and 1% of the disagreement was major in pre-scan and post-scan probabilities, respectively. Conclusion: The data show that nuclear medicine physicians can use the assessment of pre-scan clinical likelihood to determine the post-scan probability of PE.

Regional lung functional impairment in acute airway obstruction and pulmonary embolic dog models assessed with gadolinium-based aerosol ventilation and perfusion magnetic resonance imaging.

Gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA)-based aerosol ventilation and perfusion magnetic resonance (MR) images were used to define regional functional impairment in acute airway obstruction (AO) and pulmonary embolic (PE) dog models. The aerosol study was performed in 10 anesthetized normal dogs in a supine position during 20-minute spontaneous inhalation of an aerosol of 100- or 200-mmol-Gd/L Gd-DTPA solute produced by an ultrasonic nebulizer in an open-circuit delivery system, combined with a dynamic perfusion study after a 3-second intravenous bolus injection of a 0.1 mmol/kg dose of Gd-DTPA. These MR studies were also performed in the same 10 dogs approximately 30 minutes after obstructing the segmental (n = 6) or lobar (n = 4) bronchus with a balloon catheter, and in another six dogs after segmental (n = 6) and lobar (n = 4) pulmonary arterial embolization with enbucrilate. Regional lung enhancement was assessed on time-signal intensity (SI)-curves and ventilation- and perfusion-weighted images produced by a subtraction technique. The normal lungs were gradually and gravity-dependently enhanced with time after Gd-DTPA aerosol inhalation regardless of the respiratory SI changes, except for three animals with the fastest breathing rate. The averaged maximal relative lung SI increase against the baseline in the successful animals was significantly greater in the slowly and deeply breathing animals than in the fast and shallow breathing animals, regardless of the difference in Gd-concentration (100 mmol Gd/L: 153.3% +/- 69.7% vs. 54.2% +/- 23%; P < 0.001; and 200 mmol Gd/L: 189.7% +/- 68.0% vs. 75.6% +/- 42.2%; P < 0.0001, respectively). There was an additional enhancement of 382% +/- 101 in the ventral lung and 722% +/- 160 in the dorsal lung on the pulmonary arterial phase perfusion image even in the slowly and deeply breathing animals who inhaled 200-mmol-Gd/L aerosol, and the enhancement effect was significantly greater compared with that with the aerosol (P < 0.0001). The ventilation- and perfusion-weighted images clearly defined the regionally matched perfusion-ventilation deficits in all the AO models, and the regionally mismatched perfusion-ventilation in all the PE models. Gd-based aerosol can provide efficient lung enhancement in spontaneously and adequately breathing animals, using a relatively noninvasive aerosol delivery system. The combined use of Gd-based perfusion MR imaging may be acceptable for defining regionally impaired function associated with acute AO and PE.

Assessment of regional lung ventilation in dog lungs with Gd-DTPA aerosol ventilation MR imaging

Gd-DTPA aerosol ventilation MR imaging was obtained using a modified aerosol delivery system with an aerosol reservoir to non-invasively assess regional lung ventilation in dogs.Seven anesthetized, spontaneously breathing normal dogs inhaled 200 mmol Gd/l Gd-DTPA aerosol produced by an ultrasonic nebulizer, using an open-circuit aerosol delivery system with or without an aerosol reservoir. Fast gradient-echo MR images were sequentially acquired with an interval time of 1 min for 25 min before and after aerosol inhalation. The aerosol study was also performed using the aerosol delivery system with an aerosol reservoir in the same 7 dogs after airway obstruction with a balloon catheter, and in another 7 dogs after pulmonary arterial embolization with enbucrilate. An i.v. Gd-DTPA-enhanced dynamic MR study after i.v. bolus injection of a 0.1 mmol/kg dose of Gd-DTPA was combined to assess regional lung perfusion. Lung enhancement effect was evaluated by time-signal intensity curves and the subtracted ventilation- and perfusion-weighted images.With or without the aerosol reservoir, the normal dog lungs were gradually and gravity-dependently enhanced with time after aerosol inhalation. The use of the aerosol reservoir, however, showed significantly greater lung enhancement without a significant increase in breathing rate and with minimal reduction in PaO2 of less than 5 mm Hg in these animals. The enhancement effect of i.v. injection of Gd-DTPA at pulmonary arterial perfusion phase was significantly greater compared to that of Gd-DTPA aerosol throughout the normal lungs, and the subtracted ventilation-weighted and perfusion-weighted images showed homogeneous but gravity-dependent aerosol deposition and perfusion. These images clearly defined the regionally matched perfusion-ventilation deficits in the lung regions distal to bronchial obstruction in all the airway obstruction dogs, and the regionally mismatched perfusion-ventilation in the embolized regions of all the pulmonary arterial embolization animals.Gd-based aerosol can non-invasively image regional lung ventilation in spontaneously breathing animals, using an adequate aerosol delivery system. The combined use of Gd-DTPA perfusion MR imaging may be acceptable for defining regionally impaired lung function associated with acute airway obstruction and pulmonary arterial embolization.

Secretion of radioactivity in breast milk after Tc-99m DTPA aerosol and Tc-99m MAA lung imaging.

Fifteen days after giving birth, a 30-year-old woman had the sudden onset of shortness of breath, cough, and paroxysmal nocturnal dyspnea. She underwent Tc-99m DTPA aerosol ventilation and Tc-99m MAA perfusion lung studies within a 24-hour interval. The patient had bilateral venous enlargement of the lower extremities, a history of recurrent pulmonary embolism, and had smoked cigarettes for 12 years until 1 year earlier. Despite its rare occurrence during pregnancy and the post-partum period, deep vein thrombosis complicated with pulmonary embolism remains the leading source of maternal death and complications. Both perfusion and ventilation scans revealed considerable activity in the breasts as a result of radioactivity in breast milk after the administration of Tc-99m-labeled radiopharmaceuticals. The total effective dose to the infant was less than 1 mSv because breast-feeding had been interrupted for 24 hours and 4 hours after the administration of Tc-99m MAA and DTPA, respectively.

Mechanical delivery of aerosolized gadolinium-DTPA for pulmonary ventilation assessment in MR imaging.

To evaluate a new technique with mechanical administration of aerosolized gadolinium (Gd)-DTPA for MR visualization of lung ventilation. Ten experimental procedures were performed in six domestic pigs. Gd-DTPA was aerosolized by a small-particle generator. The intubated animals were mechanically aerosolized with the nebulized contrast agent and studied on a 1.5-T MR imager. Respiratory gated T1-weighted turbo spin-echo images were obtained before, during, and after contrast administration. Pulmonary signal intensity (SI) changes were calculated for corresponding regions of both lungs. Homogeneity of aerosol distribution was graded independently by two radiologists. To achieve a comparable SI increase as attained in previous trials that used manual aerosol ventilation, a ventilation period of 20 minutes (formerly 30 minutes) was sufficient. Mean SI changes of 116% were observed after that duration. Contrast delivery was rated evenly distributed in all cases by the reviewers. The feasibility of applying Gd-DTPA as a contrast agent to demonstrate pulmonary ventilation in large animals has been described before. The results of this refined technique substantiate the potential of Gd-based ventilation MR imaging by improving aerosol distribution and shortening the nebulization duration in the healthy lung.

Evaluating the SwirlerTM nebulizer

The change from multi-use to single-use nebulizer systems could potentially result in greatly increased expense for aerosol ventilation imaging and a larger waste disposal problem. We have therefore investigated a new compact single-use nebulizer system, the Swirler (Amici), for ventilation lung imaging using 99Tcm-DTPA aerosol. Seventy-five patients requiring lung ventilation/perfusion imaging were studied. The ventilation imaging was assessed using three different fills: Group 1, 1000 MBq in 2 ml; Group 2, 1000 MBq in 4 ml; and Group 3, 2000 MBq in 4 ml. The nebulization times to give 1200 counts s-1 on the posterior ventilation image were similar for Groups 1 and 3 (mean 4 min) but slower for Group 2 (mean 6 min). Room contamination was very low when performed in a room with an extractor device. The mean room air contamination was 117.0 Bq l-1 min-1 for Group 1 amd 27.6 Bq l-1 min-1 for Group 2, comparable to previous nebulizers we have used. Dose rates measured at the surface of the lead shielded nebulizer were 6.8 microSv h-1 for 1000 MBq in 2 ml and 10.9 microSv h-1 for 2000 MBq in 4 ml. The mass median diameter (span) without the extension tubing was 1.39 microns (1.85) and with a small extension tube reduced to 1.11 microns (1.70). Qualitative and quantitative assessment of image quality showed good peripheral airways penetration of particles with no uninterpretable scans, comparable with other systems we have used. In practical terms, the device is much more compact than other systems and therefore generates a much smaller volume of waste. It is an easy device to use. However, when ventilating patients supine or erect, we found that it was necessary to use the small extension tube.

Airborne contamination and the use of aerosol ventilation systems.

Airborne contamination and the use of aerosol ventilation systems.

Air contamination following aerosol ventilation in the gamma camera room

Air contamination levels arising from lung aerosol ventilation studies have previously been monitored [1]. Residence time in the room used for ventilation was perceived to be an important factor in dose received. This study was designed to assess air contamination levels when ventilation and imaging are carried out in the same room. Air samples were taken before, during and after aerosol administration, over 24 studies where a mouthpiece was used. The mean airborne contamination during administration was 4.39 kBq m-3, implying an effective dose equivalent (EDE) to the operator from inhaled activity of 0.004 microSv. Measurements made during studies on three patients where a mask was used gave a mean EDE of 0.065 microSv (the highest EDE was 0.08 microSv). Ten minutes after nebulizing had stopped, the contamination had reduced to background levels in all but two cases; in these cases, the levels were less than 1.1 kBq m-3. Aerosol ventilation in the gamma camera room does not constitute a significant radiation hazard to staff. Patient compliance is an important factor in minimizing doses. Clear instructions and practice are a vital part of the procedure.

Question of the month How should airborne contamination from aerosol ventilation imaging be minimized?

Question of the month How should airborne contamination from aerosol ventilation imaging be minimized?

Air contamination following aerosol ventilation in the gamma camera room

Air contamination following aerosol ventilation in the gamma camera room

Use of aerosol ventilation images to assess drug delivery to the lungs of children with cystic fibrosis

Parkin, A.; Reeves, J.; Burniston, M.; Smye, S. W.; Connolly, S.; Garside, F.; Robinson, P. J.; Littlewood, J. Author Information

Mismatch on Tc-99m DTPA Aerosol Ventilation-Perfusion Lung Scan Caused by Achalasia

Tc-99m DTPA aerosol ventilation in conjunction with Tc99m MAA perfusion scintigraphy is widely used in the evaluation of pulmonary embolism. The authors describe a case that demonstrates the importance of comparing any ventilation-perfusion study to the chest radiograph and clinical history to accurately evaluate the probability of pulmonary emboli

Airborne radioactive contamination following aerosol ventilation studies.

Lung aerosol ventilation studies may be accompanied by airborne contamination, with subsequent surface contamination. Airborne contamination has been measured prior to, during and following 59 consecutive 99Tcm-diethylenetriamine pentaacetate (DTPA) aerosol studies using a personal air sampler. Airborne contamination ranging between 0 and 20 330 kBq m-3 has been measured. Airborne contamination increases with degree of patient breathing difficulty. The effective dose equivalent (EDE) to staff from ingested activity has been calculated to be 0.3 microSv per study. This figure is supported by data from gamma camera images of a contaminated staff member. However, surface contamination measurements reveal that 60% of studies exceed maximum permissible contamination limits for the hands; 16% of studies exceed limits for controlled area surfaces. The EDE from ingestion is low, but protective clothing is essential to prevent body and clothing contamination. Ingested activity and surface contamination results from this study have been compared with results from a Technegas study.