Technique, pitfalls, quality, radiation dose and findings of dynamic 4-dimensional computed tomography for airway imaging in infants and children

Advancements in imaging in ChILD

Interstitial and diffuse lung diseases in children constitute a range of congenital and acquired disorders. These disorders present with signs and symptoms of respiratory disease accompanied by diffuse radiographic changes. In many cases, radiographic findings are nonspecific, while in other disorders, chest computed tomography (CT) is diagnostic in the appropriate context. Regardless, chest imaging remains central in the evaluation of the patient with suspected childhood interstitial lung disease (chILD). Several newly described chILD entities, spanning both genetic and acquired etiologies, have imaging that aid in their diagnoses. Advances in CT scanning technology and CT analysis techniques continue to improve scan quality as well as expand use of chest CT as a research tool. Finally, ongoing research is expanding use of imaging modalities without ionizing radiation. Magnetic resonance imaging is being applied to investigate pulmonary structure and function, and ultrasound of the lung and pleura is a novel technique with an emerging role in chILD disorders. This review describes the current state of imaging in chILD including recently described diagnoses, advances in conventional imaging techniques and applications, and evolving new imaging modalities that expand the clinical and research roles for imaging in these disorders.

Improving the Feasibility of Mitigating Phase Errors in 4DCT caused by a Random Reference Breathing Pattern in the Quasar Phantom and the Role of Slice Thickness

PURPOSE

The study aimed to validate a method for minimizing phase errors by combining full-length lung 4DCT (f4DCT) scans with shorter tumor-restricted 4DCT (s4DCT) scans. It assessed the feasibility of integrating two scans one covering the entire phantom length and the other focused on the tumor area. The study also evaluated the impact of Maximum Intensity Projection (MIP) volume and imaging dose for different slice thicknesses (2.5mm and 1.25mm) in both full-length and short target-restricted 4DCT scans.

METHODS

The study utilized the Quasar Programmable Respiratory Motion Phantom, simulating tumor motion with a variable lung insert. The setup included a tumor replica and a six-dot IR reflector marker on the breathing platform. The objective was to analyze volume differences in fMIP_2.5mm compared to sMIP_1.25mm within their respective 4D_MIP CT series. This involved varying breathing periods (2.5s, 3.0s, 4.0s, and 5.0s) and longitudinal tumor sizes (6mm, 8mm, and 10mm). The study also assessed exposure time and expected CTDIvol of s4D_2.5mm and s4D_1.25mm for different breathing periods (5.0s to 2.0s) in the sinusoidal wave motion of the six-dot marker on the breathing platform.

RESULTS

Conducting two consecutive 4DCT scans is viable for patients with challenging breathing patterns or when the initial lung tumor scan is in close proximity to the tumor location, eliminating the need for an additional full-length 4DCT. The analysis involves assessing MIP volume, imaging dose (CTDIvol), and exposure time. Longitudinal tumor shifts for 6mm are [16.6-17.2] in fMIP_2.5mm and [16.8-17.5] in sMIP_1.25mm, for 8mm [17.2-18.3] in fMIP_2.5mm and [17.8-18.4] in sMIP_1.25mm, and for 10mm [19-19.9] in fMIP_2.5mm and [19.4-20] in sMIP_1.25mm (p≥ 0.005), respectively.

CONCLUSION

The Quasar Programmable Respiratory Motion Phantom accurately replicated varied breathing patterns and tumor motions. Comprehensive analysis was facilitated through detailed manual segmentation of Internal Target Volumes and Internal Gross Target Volumes.

Dynamic airway computed tomography and flexible bronchoscopy for diagnosis of tracheomalacia in children: A comparison study

INTRODUCTION

Tracheomalacia (TM) is an important cause of respiratory morbidity. Dynamic flexible bronchoscopy is considered the gold standard for diagnosis. Dynamic airway computed tomography (DACT) is a low radiation, noninvasive diagnostic tool utilizing images obtained continuously over several respiratory cycles. We aimed to assess the accuracy of DACT in TM diagnosis.

METHODS

Retrospective analysis of all patients who underwent both DACT and flexible bronchoscopy within 6 months. Airway anterior-posterior (AP) diameter was measured on multiplanar reconstructions CT in both the inspiratory and expiratory phases. Using still images from the bronchoscopy videos, the AP diameter of the trachea was measured at points of maximal and minimal diameter during tidal breathing. Degree of TM on both DACT and flexible bronchoscopy were graded using a scaling system of 50%-74%, 75%-89%, and 90%-100% as described by the European Respiratory Society.

RESULTS

Twenty-four patients met inclusion criteria with an average time of 19.5 days between CT and bronchoscopy. The specificity and sensitivity of DACT for the overall diagnosis of TM was 100% and 68%, respectively, with a positive predictive value of 100% and a negative predictive value of 62%. There was a strong positive correlation between DACT and flexible bronchoscopy in the measurement of tracheal AP diameter changes (ρ = 0.773, R2 0.597, p = 0.00001). Mean effective radiation dose for DACT was 0.1 mSv.

CONCLUSION

Ultralow dose DACT has excellent specificity and positive predictive value for both detection of TM and categorizing severity of tracheal collapse but is not sufficiently sensitive to rule it out.

Dynamic computed tomography for evaluation of tracheobronchomalacia in premature infants with bronchopulmonary dysplasia

INTRODUCTION

Dynamic computed tomography (dCT) gives real-time physiological information and objective descriptions of airway narrowing in tracheobronchomalacia (TBM). There is a paucity of literature in the evaluation of TBM by dCT in premature infants with bronchopulmonary dysplasia (BPD). The aim of this study is to describe the findings of dCT and resultant changes in management in premature infants with TBM.

METHODS

A retrospective study of 70 infants was performed. Infants included were <32 weeks gestation without major anomalies. TBM was defined as ≥50% expiratory reduction in cross-sectional area with severity defined as mild (50%-75%), moderate (≥75%-90%), or severe (≥90%).

RESULTS

Dynamic CT diagnosed malacia in 53% of infants. Tracheomalacia was identified in 49% of infants with severity as 76% mild, 18% moderate, and 6% severe. Bronchomalacia was identified in 43% of infants with varying severity (53% mild, 40% moderate, 7% severe). Resultant management changes included PEEP titration (44%), initiation of bethanechol (23%), planned tracheostomy (20%), extubation trial (13%), and inhaled ipratropium bromide (7%).

CONCLUSION

Dynamic CT is a useful noninvasive diagnostic tool for airway evaluation of premature infants. Presence and severity of TBM can provide actionable information to guide more precise clinical decision making.

Computed tomography of the airways and lungs in congenital heart disease

The presence of airway and lung disease in children with congenital heart disease is commonly observed with both cardiac CT angiography and routine chest CT. In this review we discuss abnormalities encountered on CT imaging of the chest beyond the heart and central vasculature, focusing on the airways, lung parenchyma and peripheral vasculature. Preoperative and postoperative findings are reviewed as well.

Transthoracic mediastinal ultrasound in childhood tuberculosis: A review

Diagnosing childhood tuberculosis (TB) is challenging, and novel diagnostic tools are urgently needed. Mediastinal lymphadenopathy is a hallmark of primary pulmonary TB (PTB) in children. We aimed to summarise available methodological and diagnostic data of transthoracic mediastinal ultrasound for childhood TB. Literature review identified two prospective and three retrospective studies, a case report, and a technical report including cases. All reported on suprasternal scanning of the mediastinum; additional parasternal scanning was reported by five studies. The proportion of children with lymphadenopathy detected by mediastinal ultrasound ranged between 15% and 85%, with studies including both supra- and parasternal scanning achieving higher detection ratios. Three retrospective studies reported mediastinal lymphadenopathy on ultrasound for most cases presenting with a normal or inconclusive CXR. Data on ultrasound for mediastinal lymphadenopathy in children are limited but indicate that mediastinal ultrasound can successfully detect mediastinal lymphadenopathy in children with TB.

Chest Imaging for Pulmonary TB—An Update

The diagnosis of pulmonary tuberculosis (PTB) in children is challenging. Difficulties in acquiring suitable specimens, pauci-bacillary load, and limitations of current diagnostic methods often make microbiological confirmation difficult. Chest imaging provides an additional diagnostic modality that is frequently used in clinical practice. Chest imaging can also provide insight into treatment response and identify development of disease complications. Despite widespread use, chest radiographs are usually non-specific and have high inter- and intra-observer variability. Other diagnostic imaging modalities such as ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI) can provide additional information to substantiate diagnosis. In this review, we discuss the radiological features of PTB in each modality, highlighting the advantages and limitations of each. We also address newer imaging technologies and potential use.

A Delayed Anatomic Diagnosis and Management Challenge in an Initially Asymptomatic Infant With Type II Pulmonary Artery Sling: A Case Report

Pulmonary artery sling (PAS) is a rare but fatal malformation. Patients with PAS tend to develop obstructive symptoms in few weeks of life. Conversely, some patients may be otherwise mild or asymptomatic in their early life. Currently, no consensus on the intervention timing and treatment strategy for asymptomatic and mild cases has been reached. Moreover, the extent of tracheal stenosis is another determining factor for the choice of intervention timing since clinical symptoms might not correspond well with the degree of stenosis. Lack of comprehensive assessment of entire airways confer underestimation of disease severity and in turn improper choice of treatment regimens and poor outcomes. Herein, we described an infantile case of PAS, who was scheduled initially for periodic outpatient follow-up on account of the absence of symptoms and inadequate imaging assessment at diagnosis. The patient developed recurrent wheezing and progressive respiratory distress at 7 months of age. After left pulmonary artery (LPA) reimplantation without tracheal intervention, bronchoscopy was performed due to failure to wean from mechanical ventilation, which demonstrated complete tracheal cartilage rings, a long segment tracheal stenosis, a low tracheal bifurcation at T6, and the absence of a separate right middle lobe bronchus. The patient was finally diagnosed with type IIb PAS and extubated successfully following conservative treatment. Miserably, neurological sequelae were devastating, leading to poor outcomes. Comprehensive airway evaluation using bronchoscopy is substantial to early identification of all components responsible for airway compromise in PAS anatomic subtypes. Considering severe concomitant maldevelopment of the bronchial tree in children with type IIb PAS, early and complete correction by surgery might decrease perioperative morbidities and mortalities of these patients.

Fluorographic findings of diaphragmatic paralysis with spontaneous recovery

BACKGROUND

Postoperative diaphragmatic paralysis is an unavoidable complication of cardiovascular surgery. Although diaphragmatic plication, as a surgical treatment, can be performed, spontaneous recovery is possible. We aimed to identify differences in fluorographic findings of diaphragmatic paralysis between pediatric patients with and without spontaneous recovery within 1 year of intrathoracic surgery.

METHODS

Ten children, who had been followed-up for at least 1 year post-surgery and who had not received diaphragmatic plication were included and classified into those with or without spontaneous recovery. The presence or absence of the paradoxical movement of the diaphragm and mediastinum was evaluated based on fluorographic findings. Fisher's exact test was used to compare the presence or absence of paradoxical movement between the groups.

RESULTS

Eight patients experienced spontaneous recovery. The mean ± standard deviation time to spontaneous recovery was 150 ± 114 days (range, 18-338 days). In the spontaneous recovery group, no patient had paradoxical movement of the mediastinum, and a significant between-group difference was observed in the presence of the paradoxical movement of the mediastinum (present/absent in patients with vs. without spontaneous recovery: 0/8 vs. 2/0, P = 0.02). There was no significant between-group difference in paradoxical movement of the diaphragm (present/absent in patients with vs. without spontaneous recovery: 1/7 vs. 2/0, P = 0.07). Pediatric patients without paradoxical movement of the mediastinum spontaneously recovered within 1 year of intrathoracic surgery.

CONCLUSIONS

Pediatric patients without paradoxical movement of the mediastinum, based on fluorography findings, spontaneously recovered within 1 year of surgery. The timing of spontaneous recovery varied between cases.

Three-dimensional printed realistic pediatric static and dynamic airway models for bronchoscopy and foreign body removal training

For mastering bronchoscope handling, positioning, and directing of the bronchoscope in response to the intraluminal view provided by the bronchoscope camera, sufficient training is necessary, especially in infants and toddlers who have smaller airways, faster respiratory rates, and higher airway collapsibility. With the use of three-dimensional printing, we aimed to develop a set of anatomically accurate and low-cost airway models for teaching and training of bronchoscopy technique and foreign body removal: a translucent airway box model, a static airway model, and a dynamic airway model consisting of a flexible tree model connected to a pump that allows simulation of airway collapsibility during breathing. Computed tomography (CT) patient data of three different ages (1, 5, and 18 years of age) was imported into Materialise Mimics, segmented, and printed using VisoClear and soft Tango+ material. The models were evaluated by three pediatric pulmonology attendings for anatomical accuracy and usefulness for teaching and training. The translucent airway box model was preferred for the initial presentation of bronchoscope handling and learning anatomy in three dimensions. The static and flexible tree models were used to train bronchoscope handling and foreign body removal. The dynamic model provided the most realistic representation of a pediatric airway throughout the respiratory cycle with increased patency during inspiration and relative collapse during exhalation. Objective verification of anatomical accuracy and physiology of breathing motion was obtained by comparing CT scans of the model with original images and by application of 4D dynamic CT airway imaging protocols, respectively.

Accuracy and Reliability of 4D-CT and Flexible Laryngoscopy in Upper Airway Evaluation in Robin Sequence

OBJECTIVES

To evaluate the performance of 4-dimensional computed tomography (4D-CT) in assessing upper airway obstruction (UAO) in patients with Robin sequence (RS) and compare the accuracy and reliability of 4D-CT and flexible fiber-optic laryngoscopy (FFL).

STUDY DESIGN

Prospective survey of retrospective clinical data.

SETTING

Single, tertiary care pediatric hospital.

METHODS

At initial and 30-day time points, a multidisciplinary group of 11 clinicians who treat RS rated UAO severity in 32 sets of 4D-CT visualizations and FFL videos (dynamic modalities) and static CT images. Raters assessed UAO at the velopharynx and oropharynx (1 = none to 5 = complete) and noted confidence levels of each rating. Intraclass correlation and Krippendorff alpha were used to assess intra- and interrater reliability, respectively. Accuracy was assessed by comparing clinician ratings with quantitative percentage constriction (QPC) ratings, calculated based on 4D-CT airway cross-sectional area. Results were compared using Wilcoxon rank-sum and signed-rank tests.

RESULTS

There was similar intrarater agreement (moderate to substantial) with 4D-CT and FFL, and both demonstrated fair interrater agreement. Both modalities underestimated UAO severity, although 4D-CT ratings were significantly more accurate, as determined by QPC similarity, than FFL (-1.06 and -1.46 vs QPC ratings, P = .004). Overall confidence levels were similar for 4D-CT and FFL, but other specialists were significantly less confident in FFL ratings than were otolaryngologists (2.25 and 3.92, P < .0001).

CONCLUSION

Although 4D-CT may be more accurate in assessing the degree of UAO in patients with RS, 4D-CT and FFL assessments demonstrate similar reliability. Additionally, 4D-CT may be interpreted with greater confidence by nonotolaryngologists who care for these patients.

Resorbable airway splint, stents, and 3D reconstruction and printing of the airway in tracheobronchomalacia

Tracheobronchomalacia (TBM) is the most common tracheobronchial obstruction. Most cases are mild to moderate; therefore, they do not need surgical treatment. Severe tracheomalacia, however, represents a diagnostic and therapeutic challenge since they are very heterogeneous. In the armamentarium of resources for the treatment of dynamic airway collapse, splints and stents are two underused strategies and yet, they may represent the best alternative in selected cases. Lately, computed tomography 3D reconstruction of the airway has been used for the design of virtual models that can be 3D-printed for the creation of novel devices to address training, simulation, and biotechnological implants for refractory and severe airway malformations. This manuscript examines the role of resorbable stents, splints, and the 3D reconstruction and printing of the pediatric airway in tracheobronchomalacia.

Visualizing the dynamics of tuberculosis pathology using molecular imaging

Nearly 140 years after Robert Koch discovered Mycobacterium tuberculosis, tuberculosis (TB) remains a global threat and a deadly human pathogen. M. tuberculosis is notable for complex host-pathogen interactions that lead to poorly understood disease states ranging from latent infection to active disease. Additionally, multiple pathologies with a distinct local milieu (bacterial burden, antibiotic exposure, and host response) can coexist simultaneously within the same subject and change independently over time. Current tools cannot optimally measure these distinct pathologies or the spatiotemporal changes. Next-generation molecular imaging affords unparalleled opportunities to visualize infection by providing holistic, 3D spatial characterization and noninvasive, temporal monitoring within the same subject. This rapidly evolving technology could powerfully augment TB research by advancing fundamental knowledge and accelerating the development of novel diagnostics, biomarkers, and therapeutics.

Clinical Applications of Wide-Detector CT Scanners for Cardiothoracic Imaging: An Update

Technical developments in multidetector computed tomography (CT) have increased the number of detector rows on the z-axis, and 16-cm wide-area-coverage CT scanners have enabled volumetric scanning of the entire heart. Beyond coronary arterial imaging, such innovations offer several advantages during clinical imaging in the cardiothoracic area. The wide-detector CT scanner markedly reduces the image acquisition time to less than 1 second for coronary CT angiography, thereby decreasing the volume of contrast material and radiation dose required for the examination. It also eliminates stair-step artifacts, allowing robust improvements in myocardial function and perfusion imaging. Additionally, new imaging techniques for the cardiothoracic area, including subtraction imaging and free-breathing scans, have been developed and further improved by using the wide-detector CT scanner. This article investigates the technical developments in wide-detector CT scanners, summarizes their clinical applications in the cardiothoracic area, and provides a review of the recent literature.

Advanced imaging tools for childhood tuberculosis: potential applications and research needs

Tuberculosis is the leading cause of death globally that is due to a single pathogen, and up to a fifth of patients with tuberculosis in high-incidence countries are children younger than 16 years. Unfortunately, the diagnosis of childhood tuberculosis is challenging because the disease is often paucibacillary and it is difficult to obtain suitable specimens, causing poor sensitivity of currently available pathogen-based tests. Chest radiography is important for diagnostic evaluations because it detects abnormalities consistent with childhood tuberculosis, but several limitations exist in the interpretation of such results. Therefore, other imaging methods need to be systematically evaluated in children with tuberculosis, although current data suggest that when available, cross-sectional imaging, such as CT, should be considered in the diagnostic evaluation for tuberculosis in a symptomatic child. Additionally, much of the understanding of childhood tuberculosis stems from clinical specimens that might not accurately represent the lesional biology at infection sites. By providing non-invasive measures of lesional biology, advanced imaging tools could enhance the understanding of basic biology and improve on the poor sensitivity of current pathogen detection systems. Finally, there are key knowledge gaps regarding the use of imaging tools for childhood tuberculosis that we outlined in this Personal View, in conjunction with a proposed roadmap for future research.

Imaging of Acute Pulmonary and Airway Diseases in Children

소아의 다양한 응급질환 중 급성 폐질환 또는 급성 기도질환은 영상의학과 의사가 자주 대하게 되는 임상 상황이며, 일차적으로 시행되는 영상검사는 흉부 방사선사진이다. 따라서 다양한 임상 상황에서의 감별진단과 영상 소견을 숙지하는 것이 중요하다. 본 종설에서는 급성 폐질환의 다양한 원인과 폐렴을 알아보고, 폐렴과 감별해야 하는 급성 폐질환을 생각해보았다. 급성 기도질환으로는 크룹, 급성 후두염, 기관연화증, 천식, 감염 후 폐쇄세기관지염, 그리고 이물 흡인을 검토하였다. 이렇게 소아에서 고려해야 할 질환들의 영상 소견을 검토하여 진단과 치료에 도움을 줄 수 있길 바란다.