Airway Imaging Research Articles

Automated detection of circular marker particles in synchrotron phase contrast X-ray images of live mouse nasal airways for mucociliary transit assessment

Cystic Fibrosis is a genetic disease in which the production of thick sticky mucus compromises the mucociliary transit (MCT) system and causes obstruction of the conducting airways. This results in a cycle of inflammation and infection that dramatically reduces quality of life and causes an early death for most. To directly assess airway health and the effects of potential treatments, synchrotron X-ray imaging techniques have been developed to non-invasively quantify MCT, by visualizing the motion of micron-sized spherical particles deposited into the nasal airways of live mice. Since the level of contrast between the target particles and the background is quite low, and the particles often overlap, most existing methods show a low detection accuracy for the MCT tracking particles in these state-of-the-art PCXI images. This paper proposes a new way to automatically detect the circular shapes of micron-sized particles in these low-contrast X-ray images. The proposed algorithm uses a gradient-directional, sectored ring mask, combined with an edge projection into the ring boundary to identify circular shapes. This new algorithm achieves significantly improved marker particle detection rate, 92.1% precision, 93.9% recall and 92.7% F-measurement, compared to existing methods. It can detect a certain degree of overlapping particles that existing methods struggle to achieve. This algorithm provides automatic MCT particle counting, which significantly reduces the manual labelling process for MCT analysis of living animals.

Minimum Field Strength Simulator for Proton Density Weighted MRI.

ObjectiveTo develop and evaluate a framework for simulating low-field proton-density weighted MRI acquisitions based on high-field acquisitions, which could be used to predict the minimum B0 field strength requirements for MRI techniques. This framework would be particularly useful in the evaluation of de-noising and constrained reconstruction techniques.Materials and MethodsGiven MRI raw data, lower field MRI acquisitions can be simulated based on the signal and noise scaling with field strength. Certain assumptions are imposed for the simulation and their validity is discussed. A validation experiment was performed using a standard resolution phantom imaged at 0.35 T, 1.5 T, 3 T, and 7 T. This framework was then applied to two sample proton-density weighted MRI applications that demonstrated estimation of minimum field strength requirements: real-time upper airway imaging and liver proton-density fat fraction measurement.ResultsThe phantom experiment showed good agreement between simulated and measured images. The SNR difference between simulated and measured was ≤ 8% for the 1.5T, 3T, and 7T cases which utilized scanners with the same geometry and from the same vendor. The measured SNR at 0.35T was 1.8- to 2.5-fold less than predicted likely due to unaccounted differences in the RF receive chain. The predicted minimum field strength requirements for the two sample applications were 0.2 T and 0.3 T, respectively.ConclusionsUnder certain assumptions, low-field MRI acquisitions can be simulated from high-field MRI data. This enables prediction of the minimum field strength requirements for a broad range of MRI techniques.

Upper airway imaging and its role in preoperative airway evaluation

Ultrasonography (USG) is well-known as a fast, safe, and noninvasive technique. Its application for imaging of the airway is now gaining momentum. The upper airway has a complex anatomy, and its assessment forms a vital part of every preanesthetic evaluation. Ultrasound (US) imaging can help in upper airway assessment in the preoperative period. There are various approaches to upper airway USG. The technique has its own advantages, disadvantages, and limitations. This simple yet challenging imaging technique is all set to become an important part of routine preoperative airway evaluation. This article reviews the various approaches to upper airway US imaging, interpretation of the images, limitations, and disadvantages of the technique and its varied clinical applications in the preoperative period. The scientific material presented here was hand searched from textbooks and journals, electronically from PubMed, and Google scholar using text words.

Reformatted 3D airway imaging in patients with airway obstruction and micrognathia.

Mandibular distraction osteogenesis (MDO) is an effective treatment for patients with micrognathia and severe recurrent airway obstruction (Denny, 2004; Denny and Amm, 2005; Denny, 2009; Cicchetti etal., 2012; Flores etal., 2014). However the efficacy of the procedure is based on selecting the appropriate patient. Presence of central apnea or airway obstruction anywhere other than the tongue base will make MDO futile. The availability of three dimensional reformatting of the airway has greatly improved the accuracy of correct patient selection, providing a powerful tool to further characterize the pathology in these patients. We conducted a retrospective review of the last thirty patients with micrognathia and severe recurrent airway obstruction seen in consult by the senior author for potential role of surgery in their management. Twenty-one patients met our inclusion criteria, with fourteen treated appropriately with MDO. The remaining patients had findings on the 3D airway CT scans with other anatomic causes of obstruction making them inappropriate candidates for mandibular distraction osteogenesis. The use of three dimensional formatting of the airway from CT scans obtained using low dose protocols has improved the accuracy of evaluation and treatment of Pierre Robin patients. Most valuable is the non-invasive identification of airway abnormalities that would make mandibular distraction osteogenesis ineffective in correcting the airway obstruction.

X-ray specks: low dose in vivo imaging of lung structure and function

Respiratory health is directly linked to the structural and mechanical properties of the airways of the lungs. For studying respiratory development and pathology, the ability to quantitatively measure airway dimensions and changes in their size during respiration is highly desirable. Real-time imaging of the terminal airways with sufficient contrast and resolution during respiration is currently not possible. Herein we reveal a simple method for measuring lung airway dimensions in small animals during respiration from a single propagation-based phase contrast x-ray image, thereby requiring minimal radiation. This modality renders the lungs visible as a speckled intensity pattern. In the near-field regime, the size of the speckles is directly correlated with that of the dominant length scale of the airways. We demonstrate that Fourier space quantification of the speckle texture can be used to statistically measure regional airway dimensions at the alveolar scale, with measurement precision finer than the spatial resolution of the imaging system. Using this technique we discovered striking differences in developmental maturity in the lungs of rabbit kittens at birth.

Magnetic resonance imaging in children: common problems and possible solutions for lung and airways imaging.

Pediatric chest MRI is challenging. High-resolution scans of the lungs and airways are compromised by long imaging times, low lung proton density and motion. Low signal is a problem of normal lung. Lung abnormalities commonly cause increased signal intenstities. Among the most important factors for a successful MRI is patient cooperation, so the long acquisition times make patient preparation crucial. Children usually have problems with long breath-holds and with the concept of quiet breathing. Young children are even more challenging because of higher cardiac and respiratory rates giving motion blurring. For these reasons, CT has often been preferred over MRI for chest pediatric imaging. Despite its drawbacks, MRI also has advantages over CT, which justifies its further development and clinical use. The most important advantage is the absence of ionizing radiation, which allows frequent scanning for short- and long-term follow-up studies of chronic diseases. Moreover, MRI allows assessment of functional aspects of the chest, such as lung perfusion and ventilation, or airways and diaphragm mechanics. In this review, we describe the most common MRI acquisition techniques on the verge of clinical translation, their problems and the possible solutions to make chest MRI feasible in children.

A Genome-Wide Association Study of Emphysema and Airway Quantitative Imaging Phenotypes.

Chronic obstructive pulmonary disease (COPD) is defined by the presence of airflow limitation on spirometry, yet subjects with COPD can have marked differences in computed tomography imaging. These differences may be driven by genetic factors. We hypothesized that a genome-wide association study (GWAS) of quantitative imaging would identify loci not previously identified in analyses of COPD or spirometry. In addition, we sought to determine whether previously described genome-wide significant COPD and spirometric loci were associated with emphysema or airway phenotypes. To identify genetic determinants of quantitative imaging phenotypes. We performed a GWAS on two quantitative emphysema and two quantitative airway imaging phenotypes in the COPDGene (non-Hispanic white and African American), ECLIPSE (Evaluation of COPD Longitudinally to Identify Predictive Surrogate Endpoints), NETT (National Emphysema Treatment Trial), and GenKOLS (Genetics of COPD, Norway) studies and on percentage gas trapping in COPDGene. We also examined specific loci reported as genome-wide significant for spirometric phenotypes related to airflow limitation or COPD. The total sample size across all cohorts was 12,031, of whom 9,338 were from COPDGene. We identified five loci associated with emphysema-related phenotypes, one with airway-related phenotypes, and two with gas trapping. These loci included previously reported associations, including the HHIP, 15q25, and AGER loci, as well as novel associations near SERPINA10 and DLC1. All previously reported COPD and a significant number of spirometric GWAS loci were at least nominally (P < 0.05) associated with either emphysema or airway phenotypes. Genome-wide analysis may identify novel risk factors for quantitative imaging characteristics in COPD and also identify imaging features associated with previously identified lung function loci.

Influence of aberrations on the image quality in optical coherence microscopy

High resolution imaging of human airways holds promise to visualize pathologic morphology and function with subcellular resolution. We have shown that endoscopic optical coherence microscopy (eOCM) is able to provide cross-sectional images with micrometer resolution. Our eOCT device is based on a supercontinuum light source, a custom made 400nm spectrometer, and a custom made 0.5 NA gradiant index (GRIN) endoscope. The endoscope is connected via a novel compact handpiece to lightsource and spectrometer.

Improved endoscopic optical coherence microscopy for imaging of humans airways in patients

Improved endoscopic optical coherence microscopy for imaging of humans airways in patients

Optical coherence microscopy for fast intravital imaging of airways in mice and humans with subcellular resolution

The study of airway morphology and function with subcellular resolution in animals and humans in vivo has been hampered by the lack of suitable imaging techniques. To overcome this problem we developed optical coherence microscopy (OCM) to image the airways of mice and humans with high spatiotemporal resolution.

CFD simulation of airflow behavior and particle transport and deposition in different breathing conditions through the realistic model of human airways

In this work, the airflow behavior and particle transport and deposition in different breathing conditions such as light breathing condition (15L/min), normal breathing condition (30L/min) and heavy breathing condition (60L/min) are investigated. The realistic geometry data was reconstructed from CT-scan images of the human airways with 0.5mm thickness of slices. The CT-scan images (DICOM files) are imported in the 3D-DOCTOR software and all slices were segmented. Then, the output has been imported in CATIA-V5 software. Finally, face, volume, mesh and extension tubes at inlet and outlets were created and then imported into ANSYS FLUENT 15. The Lagrangian approach is used to evaluating the transport and deposition of inhaled micro-particles. The presented results showed that for dp=5μm and 10μm, when flow rate =30Lmin and for dp=1μm, when flow rate =15Lmin, the particle deposition fraction have maximum amount. For flow rate =15Lmin and =30Lmin, the maximum deposition occurs in the zone number 1 and for flow rate =60Lmin occurs in the zone number 4. Also, the maximum pressure distribution happens when flow rate =60Lmin which would be acceptable. According to the results, the particles tended to go to the right branch and the minimum number of particles crossed the zone numbers 6 and 11.

A robust and efficient curve skeletonization algorithm for tree-like objects using minimum cost paths

Conventional curve skeletonization algorithms using the principle of Blum's transform, often, produce unwanted spurious branches due to boundary irregularities, digital effects, and other artifacts. This paper presents a new robust and efficient curve skeletonization algorithm for three-dimensional (3-D) elongated fuzzy objects using a minimum cost path approach, which avoids spurious branches without requiring post-pruning. Starting from a root voxel, the method iteratively expands the skeleton by adding new branches in each iteration that connects the farthest quench voxel to the current skeleton using a minimum cost path. The path-cost function is formulated using a novel measure of local significance factor defined by the fuzzy distance transform field, which forces the path to stick to the centerline of an object. The algorithm terminates when dilated skeletal branches fill the entire object volume or the current farthest quench voxel fails to generate a meaningful skeletal branch. Accuracy of the algorithm has been evaluated using computer-generated phantoms with known skeletons. Performance of the method in terms of false and missing skeletal branches, as defined by human experts, has been examined using in vivo CT imaging of human intrathoracic airways. Results from both experiments have established the superiority of the new method as compared to the existing methods in terms of accuracy as well as robustness in detecting true and false skeletal branches. The new algorithm makes a significant reduction in computation complexity by enabling detection of multiple new skeletal branches in one iteration. Specifically, this algorithm reduces the number of iterations from the number of terminal tree branches to the worst case performance of tree depth. In fact, experimental results suggest that, on an average, the order of computation complexity is reduced to the logarithm of the number of terminal branches of a tree-like object.

Pharyngeal mucosal wall folds in subjects with obstructive sleep apnea.

Mechanical processes underlying pharyngeal closure have not been examined. We hypothesized that the pharyngeal mucosal surface would fold during closure, and lowering the upper airway lining liquid surface tension would unfold areas of mucosal apposition, i.e., folds. We compared baseline pharyngeal fold numbers and response to reduction in upper airway liquid surface tension in healthy and obstructive sleep apnea (OSA) subjects. Awake, gated magnetic resonance pharyngeal airway images of 10 healthy and 11 OSA subjects were acquired before and after exogenous surfactant administration (beractant). Upper airway liquid surface tension was measured at the beginning and end of image acquisition and averaged. Velopharyngeal and oropharyngeal images were segmented and analyzed separately for average cross-sectional area, circumference, and fold number. Compared with healthy subjects, at baseline, velopharynx for OSA subjects had a smaller cross-sectional area (98.3 ± 32.5 mm(2) healthy, 52.3 ± 23.6 mm(2) OSA) and circumference (46.5 ± 8.1 mm healthy, 30.8 ± 6.1 mm OSA; both P < 0.05, unpaired t-test), and fewer folds (4.9 ± 1.6 healthy, 3.1 ± 1.8 OSA, P < 0.03). There were no differences in oropharynx for cross-sectional area, circumference, or folds. Reduction in upper airway liquid surface tension from 61.3 ± 1.2 to 55.3 ± 1.5 mN/m (P < 0.0001) did not change cross-sectional area or circumference for velopharynx or oropharynx in either group; however, in OSA subjects, oropharyngeal folds fell from 6.8 ± 3.1 to 4.7 ± 1.2 (n = 8, P < 0.05), and velopharyngeal folds from 3.3 ± 1.9 to 2.3 ± 1.2 (P = 0.08), and were unchanged in healthy subjects. Subjects with OSA have fewer velopharyngeal wall folds, which decrease further when surface tension falls. We speculate that reduced pharyngeal wall folds contribute to an increase in pharyngeal collapsibility.

Diagnosis and management of primary ciliary dyskinesia

Primary ciliary dyskinesia (PCD) is a rare autosomal recessive disorder with defective structure and/or function of motile cilia/flagella, causing chronic upper and lower respiratory tract infections, fertility problems, and disorders of organ laterality. Diagnosing PCD requires a combined approach utilizing characteristic phenotypes and complementary methods for detection of defects of ciliary function and ultrastructure, measurement of nasal nitric oxide and genetic testing. Currently, biallelic mutations in 31 different genes have been linked to PCD allowing a genetic diagnosis in approximately ~ 60% of cases. Management includes surveillance of pulmonary function, imaging, and microbiology of upper and lower airways in addition to daily airway clearance and prompt antibiotic treatment of infections. Early referral to specialized centers that use a multidisciplinary approach is likely to improve outcomes. Currently, evidence-based knowledge on PCD care is missing let alone management guidelines. Research and clinical investigators, supported by European and North American patient support groups, have joined forces under the name of BESTCILIA, a European Commission funded consortium dedicated to improve PCD care and knowledge. Core programs of this network include the establishment of an international PCD registry, the generation of disease specific PCD quality of life questionnaires, and the first randomized controlled trial in PCD.

Functional respiratory imaging of airways in ventilated ARDS patients: revealing the regional relation between PEEP-induced airway opening and airway dilatation

ARDS has a wide variability of lung morphological characteristics. Both alveolar collapse and airway narrowing or closing are present, often heterogeneously. Despite advances in ARDS imaging, we have thus far been unable to distinguish regional airway opening from airway dilatation in PEEP-induced lung recruitment. We demonstrate the technique of functional respiratory imaging (FRI) to differentiate these two entities.

A surprise finding on laryngoscopy: large asymptomatic vallecular

SummaryWe present the unexpected discovery of a previously asymptomatic vallecular cyst that was found during laryngoscopy. We describe pre‐operative assessment of the patient, the immediate and subsequent management of the cyst, and follow up. This case report highlights the limitations of commonly used bedside airway assessments, the need for immediate access to a difficult intubation trolley and the potential benefits of airway imaging pre‐induction. We discuss the contemporaneous decisions made and review the literature related to vallecular cysts.

Subclinical infection and dosing in primary immunodeficiencies.

Subclinical infection and dosing in primary immunodeficiencies.

Living a healthier lifestyle.

The roles of diet, activity, and exercise have long been recognized as essential to a healthy lifestyle. As Plato stated, “Lack of activity destroys the good condition of every human being, while movement and methodical physical exercise save it and preserve it.” In his Physiology is Medicine

A high-efficiency fiber-based imaging system for co-registered autofluorescence and optical coherence tomography.

We present a power-efficient fiber-based imaging system capable of co-registered autofluorescence imaging and optical coherence tomography (AF/OCT). The system employs a custom fiber optic rotary joint (FORJ) with an embedded dichroic mirror to efficiently combine the OCT and AF pathways. This three-port wavelength multiplexing FORJ setup has a throughput of more than 83% for collected AF emission, significantly more efficient compared to previously reported fiber-based methods. A custom 900 µm diameter catheter ‒ consisting of a rotating lens assembly, double-clad fiber (DCF), and torque cable in a stationary plastic tube ‒ was fabricated to allow AF/OCT imaging of small airways in vivo. We demonstrate the performance of this system ex vivo in resected porcine airway specimens and in vivo in human on fingers, in the oral cavity, and in peripheral airways.

A New Approach of Arc Skeletonization for Tree-Like Objects Using Minimum Cost Path.

Traditional arc skeletonization algorithms using the principle of Blum's transform, often, produce unwanted spurious branches due to boundary irregularities and digital effects on objects and other artifacts. This paper presents a new robust approach of extracting arc skeletons for three-dimensional (3-D) elongated fuzzy objects, which avoids spurious branches without requiring post-pruning. Starting from a root voxel, the method iteratively expands the skeleton by adding a new branch in each iteration that connects the farthest voxel to the current skeleton using a minimum-cost geodesic path. The path-cost function is formulated using a novel measure of local significance factor defined by fuzzy distance transform field, which forces the path to stick to the centerline of the object. The algorithm terminates when dilated skeletal branches fill the entire object volume or the current farthest voxel fails to generate a meaningful branch. Accuracy of the algorithm has been evaluated using computer-generated blurred and noisy phantoms with known skeletons. Performance of the method in terms of false and missing skeletal branches, as defined by human expert, has been examined using in vivo CT imaging of human intrathoracic airways. Experimental results from both experiments have established the superiority of the new method as compared to a widely used conventional method in terms of accuracy of medialness as well as robustness of true and false skeletal branches.