CT virtual bronchoscopy of the central airways in patients with Wegener's granulomatosis

Lung involvement in ANCA-associated vasculitis

Lung involvement is one of the most common clinical features in ANCA-associated vasculitides (AAV), including granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA). In this review, we detail the five main presentations of pulmonary involvement in AAV: necrotizing granulomatous inflammation, tracheobronchial inflammation, pulmonary capillaritis, interstitial lung disease (ILD) and asthma with their clinical, radiological and therapeutic characteristics. The prevalence of these manifestations is variable according to the subtype of AAV, necrotizing granulomatous inflammation and tracheobronchial inflammation being defining features of GPA whereas ILD is primarily seen in patients with MPA, especially in association with ANCA directed against myeloperoxydase (MPO-ANCA), and asthma is characteristic of EGPA. Despite recent progresses in the diagnosis and management of these conditions, several questions remain and are discussed here, including local treatments for subglottic stenosis, the uncertain efficacy of plasma exchanges for alveolar hemorrhage, the potential role of antifibrotic agents in ILD associated with MPA, and the use of novel anti-IL-5 strategies in EGPA.

Update on the Management of Respiratory Manifestations of the Antineutrophil Cytoplasmic Antibodies-Associated Vasculitides

Antibody-associated vasculitis comprises 3 small vessel vasculitis syndromes: granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic polyangiitis (EGPA). This article outlines the major tracheobronchial and pulmonary parenchymal disease manifestations of GPA and MPA and their management, as well as relevant recent advances in the treatment of EGPA. Shared trends in the management of all 3 syndromes are: (1) a focus on glucocorticoid avoidance and (2) an increasing reliance on biologic agents. Evidence from randomized controlled trials and large cohort studies in support of these trends as well as ongoing research efforts are summarized.

Accuracy of Magnetic Resonance Imaging for Grading of Subglottic Stenosis in Patients With Granulomatosis With Polyangiitis: Correlation With Pulmonary Function Tests and Laryngoscopy

OBJECTIVE

To compare magnetic resonance imaging (MRI)-based and laryngoscopy-based subglottic stenosis (SGS) grading with pulmonary function testing (PFT) in patients with granulomatosis with polyangiitis (GPA).

METHODS

In this retrospective study, we included 118 examinations of 44 patients with GPA and suspected SGS. All patients underwent MRI, laryngoscopy, and PFT. Stenosis was graded on a 4-point scale by endoscopy and MRI using the Meyer-Cotton (MC) score (score 1: ≤50%, 2: 51-70%, 3: 71-99%, and 4: 100%) and as percentage by MRI. Results were compared with peak expiratory flow (PEF) and maximum inspiratory flow (MIF) from PFT, serving as objective functional reference.

RESULTS

In MRI, 112 of 118 examinations (95%) were rated positive for SGS (grade 1 [n = 82], grade 2 [n = 26], and grade 3 [n = 4]), whereas in laryngoscopy 105 of 118 examinations (89%) were rated positive for SGS (grade 1 [n = 73], grade 2 [n = 24], and grade 3 [n = 8]). MRI and laryngoscopy agreed in 75 of 118 examinations (64%). MRI determined higher scores in 20 examinations (17%) and lower scores in 23 examinations (19%) compared to laryngoscopy. MC scores as determined by both MRI and laryngoscopy showed comparable correlations with PEF (r = -0.363, P = 0.016, and r = -0.376, P = 0.012, respectively) and MIF (r = -0.340, P = 0.024, and r = -0.320, P = 0.034, respectively). The highest correlation was found between MRI-based stenosis grading in percentage with PEF (r = -0.441, P = 0.003) and MIF (r = -0.413, P = 0.005).

CONCLUSION

MRI and laryngoscopy provide comparable results for grading of SGS in GPA and correlate well with PFT. MRI is an attractive noninvasive and radiation-free alternative for monitoring the severity of SGS in patients with GPA.

Added value of double reading in diagnostic radiology,a systematic review

Objectives

Double reading in diagnostic radiology can find discrepancies in the original report, but a systematic program of double reading is resource consuming. There are conflicting opinions on the value of double reading. The purpose of the current study was to perform a systematic review on the value of double reading.

Methods

A systematic review was performed to find studies calculating the rate of misses and overcalls with the aim of establishing the added value of double reading by human observers.

Results

The literature search resulted in 1610 hits. After abstract and full-text reading, 46 articles were selected for analysis. The rate of discrepancy varied from 0.4 to 22% depending on study setting. Double reading by a sub-specialist, in general, led to high rates of changed reports.

Conclusions

The systematic review found rather low discrepancy rates. The benefit of double reading must be balanced by the considerable number of working hours a systematic double-reading scheme requires. A more profitable scheme might be to use systematic double reading for selected, high-risk examination types. A second conclusion is that there seems to be a value of sub-specialisation for increased report quality. A consequent implementation of this would have far-reaching organisational effects.

Key Points

• In double reading, two or more radiologists read the same images.

• A systematic literature review was performed.

• The discrepancy rates varied from 0.4 to 22% in various studies.

• Double reading by sub-specialists found high discrepancy rates.

Electronic supplementary material

The online version of this article (10.1007/s13244-018-0599-0) contains supplementary material, which is available to authorised users.

The effect of virtual endoscopy on diagnostic accuracy and airway management strategies in patients with head and neck pathology: a prospective cohort study

PURPOSE

There is growing evidence to suggest a deficiency in anesthesiologists' diagnosis of airway pathology and subsequent airway management planning, and conventional instruments have not shown increases in safety. Virtual endoscopy (VE) is a tool that can detail intraluminal anatomical "fly-through" information in a format visually similar to the flexible endoscopic views familiar to anesthesiologists. We aimed to determine the effect of VE on diagnostic accuracy and airway management strategies when compared with conventional tools.

METHODS

Clinical scenarios, along with computerized tomography (CT) imaging, were presented to 20 anesthesiologists, and structured questions were asked regarding diagnosis of airway pathology and airway management strategy. Virtual endoscopy videos were then provided and the questions were repeated. Following the CT and VE presentations, the anesthesiologists' responses involving diagnostic accuracy and airway management strategy were compared between the CT and VE techniques. Answers relating to the utility of VE were also sought.

RESULTS

Diagnostic accuracy was 54.1% with CT alone and increased to 67.7% when VE was added (P = 0.007). In 48% of cases, the addition of VE to clinical history and CT led to changes in airway management strategy (P < 0.001), and 90.6% of these changes were deemed more cautious (P < 0.001).

CONCLUSION

Virtual endoscopy improves the accuracy in diagnosis of airway pathology when compared with CT alone. Furthermore, it leads to more conservative and potentially safer airway management strategies in patients with head and neck pathology.

Tracheobronchial Stenoses in Granulomatosis With Polyangiitis (Wegener's): A Report on 26 Cases

Tracheobronchial stenoses (TBSs) are potentially severe manifestations of granulomatosis with polyangiitis (Wegener's) (GPA) that usually respond poorly to corticosteroids and immunosuppressive agents. We describe 26 GPA patients with ≥1 tracheal (mainly subglottic, SGS) and/or bronchial stenosis(ses) (BS(s)).Sixteen patients had solitary SGS and 10 had ≥1 BS(s). The male/female sex ratio was 9:17, and the median age at GPA diagnosis was 32 years (3:13 and 28 years, respectively, for SGS patients). Antineutrophil cytoplasm antibodies were proteinase 3-positive in 65.5% of the patients (50% of those with SGS).Despite conventional GPA therapy, 62% patients experienced ≥1 stenosis relapse(s) (81% of SGS patients, for a total of 1-8 relapses per patient). None of the several systemic or endoscopic treatments prevented future relapses. Cyclophosphamide induction therapy was effective in 4/6 patients with BS(s) and in 1 patient with SGS among the 7 treated. After many relapses, rituximab achieved remission in 3/4 SGS patients. Endoscopic treatments (dilation, laser, corticosteroid injection, etc.) had only transient efficacy. Other GPA manifestations relapsed independently of TBSs. One SGS patient died of acute respiratory distress syndrome.Our findings confirmed that TBSs are severe GPA manifestations that evolve independently of other organ involvements and do not respond to conventional systemic regimens. As previously described, our population was younger and comprised more females than usual GPA patients, especially those with SGS.The small number of patients and the wide variety of local and systemic treatments prevent us from drawing definitive conclusions about the contribution of each procedure. However, cyclophosphamide seemed to effectively treat BSs, but not SGS, and rituximab may be of interest for SGS management.

Imaging of systemic vasculitis in childhood

The term "systemic vasculitis" encompasses a diverse set of diseases linked by the presence of blood-vessel inflammation that are often associated with critical complications. These diseases are uncommon in childhood and are frequently subjected to a delayed diagnosis. Although the diagnosis and treatment may be similar for adult and childhood systemic vasculitides, the prevalence and classification vary according to the age group under investigation. For example, Kawasaki disease affects children while it is rarely encountered in adults. In 2006, the European League Against Rheumatism (EULAR) and the Pediatric Rheumatology European Society (PReS) proposed a classification system for childhood vasculitis adopting the system devised in the Chapel Hill Consensus Conference in 1993, which categorizes vasculitides according to the predominant size of the involved blood vessels into small, medium and large vessel diseases. Currently, medical imaging has a pivotal role in the diagnosis of vasculitis given recent developments in the imaging of blood vessels. For example, early diagnosis of coronary artery aneurysms, a serious complication of Kawasaki disease, is now possible by magnetic resonance imaging (MRI) of the heart and multidetector computed tomography (MDCT); positron emission tomography/CT (PET/CT) helps to assess active vascular inflammation in Takayasu arteritis. Our review offers a unique approach using the integration of the proposed classification criteria for common systemic childhood vasculitides with their most frequent imaging findings, along with differential diagnoses and an algorithm for diagnosis based on common findings. It should help radiologists and clinicians reach an early diagnosis, therefore facilitating the ultimate goal of proper management of affected children.

Non-malignant central airway obstruction

The most common causes of non-malignant central airway obstruction are post-intubation and post-tracheostomytracheal stenosis, followed by the presence of foreign bodies, benign endobronchial tumours and tracheobronchomalacia. Other causes, such as infectious processes or systemic diseases, are less frequent. Despite the existence of numerous classification systems, a consensus has not been reached on the use of any one of them in particular. A better understanding of the pathophysiology of this entity has allowed us to improve diagnosis and treatment. For the correct diagnosis of nonspecific clinical symptoms, pulmonary function tests, radiological studies and, more importantly, bronchoscopy must be performed. Treatment must be multidisciplinary and tailored to each patient, and will require surgery or endoscopic intervention using thermoablative and mechanical techniques.

Current modalities in the diagnosis of pulmonary vasculitis

INTRODUCTION

This review addresses the pulmonary manifestations of the vasculitides, with a focus on diagnostic modalities. Haemorrhagic presentations (usually associated with nephritis: the pulmonary-renal syndrome) are the most common vasculitic cause of early death.

AREAS COVERED

The diagnostic modalities in the pulmonary vasculitides are reviewed, with a focus on primary systemic vasculitis. A literature search of original research and review articles on pulmonary vasculitides was undertaken using the PubMed database.

EXPERT OPINION

Small-vessel anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis, especially granulomatosis with polyangiitis (Wegener's granulomatosis) are the most frequent causes of pulmonary vasculitis and typically present as nodules, alveolar infiltrates (haemorrhagic or not), cavities or tracheobronchial stenosis. Lung involvement is less common in large-vessel vasculitis when pulmonary vascular abnormalities can be seen. No single test is pathogonomonic and diagnosis requires integration of clinical, laboratory, imaging and histological findings. Treatment follows similar regimens to other vasculitic presentations, with glucocorticoids in conjunction with immunosuppressive agents, and management of intercurrent sepsis and the increased risk of cardiovascular and thromboembolic events. Prompt diagnosis and intensive treatment of pulmonary vasculitis is essential to improve early mortality and long-term outcomes.

Modern imaging of the tracheo-bronchial tree

Recent state-of-the-art computed tomography and improved three-dimensional (3-D) postprocessing techniques have revolutionized the capability of visualizing airway pathology, offering physicians an advanced view of pathology and allowing for appropriate management planning. This article is a comprehensive review of trachea and main bronchi imaging, with emphasis on the dynamic airway anatomy, and a discussion of a wide variety of diseases including, but not limited to, congenital large airway abnormalities, tracheobronchial stenoses, benign and malignant neoplasms and tracheobronchomalacia. The importance of multiplanar reconstruction, 3-D reconstruction and incorporation of dynamic imaging for non-invasive evaluation of the large airways is stressed.

Surgical interventions and local therapy for Wegener's granulomatosis

PURPOSE OF REVIEW

This review discusses the use of interventional procedures to treat manifestations of Wegener's granulomatosis caused by tissue damage and scarring. These manifestations include nasal and paranasal sinus disease, middle ear inflammation, nasolacrimal duct obstruction, orbital inflammatory masses, subglottic stenosis, tracheobronchial disease, and end-stage renal disease.

RECENT FINDINGS

Tissue damage caused by inflammation or a cicatricial process represents one of the major sources of morbidity for patients with Wegener's granulomatosis. Some of these manifestations require special interventions used alone or in combination with conventional medical treatment. These interventional procedures may include surgical or endoscopic repair of altered tissue, replacement of damaged organs, or the delivery of topical or injectable medications directly to the site of disease. Distinguishing symptoms caused by active disease from symptoms caused by tissue scarring is challenging and may play a critical role regarding the use of systemic immunosuppressive medications in combination with interventional therapy.

SUMMARY

Interventional procedures are indicated in certain manifestations of Wegener's granulomatosis. Distinguishing active Wegener's granulomatosis from inactive Wegener's granulomatosis and recognizing disease manifestations that may be amenable to local interventions can greatly improve the quality of life of patients. However, the evidence supporting the use of many of these interventions is based on small case series or individual reports.

Wegener's granulomatosis in the chest: high-resolution CT findings

OBJECTIVE

Wegener's granulomatosis is an uncommon necrotizing vasculitis having variable presentations in the chest that are best depicted on high-resolution CT. Imaging findings may include nodules, which may cavitate; ground-glass opacity secondary to pulmonary hemorrhage; and airway stenoses and ulcerations. Active Wegener's granulomatosis can mimic pneumonia, septic emboli, and metastases.

CONCLUSION

This article will illustrate the high-resolution CT findings of Wegener's granulomatosis in the chest.

Alterações difusas da traquéia: aspectos na tomografia computadorizada

O objetivo deste ensaio pictórico foi apresentar as principais alterações tomográficas observadas em doenças que acometem a traquéia de forma difusa. As doenças estudadas foram amiloidose, traqueobroncopatia osteocondroplástica, traqueobroncomegalia, papilomatose laringo-traqueo-brônquica, linfoma, neurofibromatose, policondrite recidivante, granulomatose de Wegener, tuberculose, paracoccidioidomicose e traqueobroncomalácia. O principal aspecto observado na tomografia computadorizada foi o espessamento das paredes traqueais, com ou sem nodulações, calcificações parietais ou comprometimento da parede posterior. Embora a tomografia computadorizada permita a detecção e a caracterização das doenças das vias aéreas centrais, e a correlação com os dados clínicos reduza as possibilidades diagnósticas, a broncoscopia com biópsia continua sendo o procedimento mais importante no diagnóstico das lesões difusas da traquéia.

Computer-based System for the Virtual-Endoscopic Guidance of Bronchoscopy

The standard procedure for diagnosing lung cancer involves two stages: three-dimensional (3D) computed-tomography (CT) image assessment, followed by interventional bronchoscopy. In general, the physician has no link between the 3D CT image assessment results and the follow-on bronchoscopy. Thus, the physician essentially performs bronchoscopic biopsy of suspect cancer sites blindly. We have devised a computer-based system that greatly augments the physician's vision during bronchoscopy. The system uses techniques from computer graphics and computer vision to enable detailed 3D CT procedure planning and follow-on image-guided bronchoscopy. The procedure plan is directly linked to the bronchoscope procedure, through a live registration and fusion of the 3D CT data and bronchoscopic video. During a procedure, the system provides many visual tools, fused CT-video data, and quantitative distance measures; this gives the physician considerable visual feedback on how to maneuver the bronchoscope and where to insert the biopsy needle. Central to the system is a CT-video registration technique, based on normalized mutual information. Several sets of results verify the efficacy of the registration technique. In addition, we present a series of test results for the complete system for phantoms, animals, and human lung-cancer patients. The results indicate that not only is the variation in skill level between different physicians greatly reduced by the system over the standard procedure, but that biopsy effectiveness increases.

Outpatient assessment of systemic vasculitis

The vasculitides are complex, multisystem diseases, the natural history of which has been transformed by the use of immunosuppressive therapy. In many cases, survival is characterized by the presence of ongoing low-grade disease activity and, now that patients can survive acute, life-threatening manifestations of vasculitis, the new challenge is to provide accurate descriptions of these problems so as to plan appropriate changes in therapy to ensure optimal control of disease, with minimal toxicity, damage, and impairment of function. To achieve these aims, it is necessary to undertake structured evaluation of patients, with a significant dependence on careful clinical observation, supported by appropriate laboratory investigation at all stages from diagnosis to long-term care of these patients. This chapter reviews the important aspects of disease assessment and recommends a strategy for managing these complex patients. We can make use of standardized disease assessment instruments, such as the Birmingham Vasculitis Assessment Score and the Vasculitis Damage Index, to serve as an aide memoire in documenting the clinical features of disease. Routine monitoring for drug toxicity in the short-term and long-term is essential. Above all, however, it is very important to review these patients regularly and see them urgently in case of flares or complications, which are a common problem in most forms of vasculitis.

Tracheobronchial Anomalies and Stenoses: Detection with Low-Dose Multidetector CT with Virtual Tracheobronchoscopy—Comparison with Flexible Tracheobronchoscopy

PURPOSE

To prospectively assess the sensitivity and specificity of low-dose multidetector computed tomography (CT) with virtual tracheobronchoscopy (VT) for evaluation of suspected airway stenoses and/or abnormalities by using flexible tracheobronchoscopy (FT) as the reference standard.

MATERIALS AND METHODS

The study was approved by the local ethics committee; parental consent was obtained. Forty-five patients with clinically and/or radiographically suspected tracheobronchial stenosis and/or anomaly underwent FT and contrast material-enhanced single-phase multidetector CT with VT. CT was performed with an age- and weight-adjusted low-dose protocol: 120 or 80 kV; 120 or 60 mA; collimation, 1.5 or 0.75 mm; gantry rotation, 0.5 second. Mean effective dose was calculated for all examinations. Postprocessing was performed with surface rendering of VT images and multiplanar reformations. CT images were analyzed in consensus by two radiologists who were blinded to FT results. Statistical analysis was performed with 2 x 2 contingency tables; 95% confidence intervals (CIs) were calculated with the Blyth-Still-Casella procedure.

RESULTS

Mean patient age was 4.4 years (range, 2 months to 16 years; 53% male patients). Tracheobronchial narrowing and/or abnormality were depicted at FT in 38 of 45 patients. In 33 of 38 patients, multidetector CT with VT depicted a tracheobronchial narrowing and/or anomaly. In 10 of 38 patients, tracheobronchial stenosis was induced by vascular anomalies. Five patients with normal findings at multidetector CT with VT had tracheobronchomalacia with inspiratory airway stenosis at FT. Sensitivity and specificity of CT with VT were 86.8% (95% CI: 73.3%, 94.7%) and 85.7% (95% CI: 44.6%, 99.3%), respectively. Positive and negative predictive values were 97.1% (95% CI: 84.9%, 99.9%) and 54.5% (95% CI: 25.0%, 80.0%), respectively. Overall accuracy was 86.7% (95% CI: 74.3%, 94.0%). Mean effective dose was 1.1 mSv (range, 0.5-1.8 mSv).

CONCLUSION

Multidetector CT with VT with a low-dose protocol had high sensitivity and specificity for depiction of tracheobronchial narrowings and/or anomalies. However, tracheal narrowing due to tracheobronchomalacia was difficult to diagnose at single-phase multidetector CT with VT.

Sténoses endobronchiques au cours de la granulomatose de Wegener

INTRODUCTION

Endobronchial stenoses are rare in the course of Wegener's granulomatosis, and they occur even more rarely than subglottic stenoses.

EXEGESIS

We report seven cases of endobronchial stenoses in the setting of Wegener granulomatosis. Neither the pulmonary symptoms nor the systemic manifestations of vasculitis were specific. However 6/7 patients presented a wheezing or an hemoptysis. Bronchial endoscopy has permitted the diagnosis in all cases. Local evolution was cicatricial and symptomatic stenosis in 3 cases (42,8%).

CONCLUSION

Thus these lesions must be research in any case of pulmonary abnormality in the course of Wegener's granulomatosis, because they may lead to a pejorative prognosis. Moreover general and local treatment must be given early (at the inflammatory stage). After this stage, the local treatments are difficult and not efficient.

Is Virtual Bronchoscopy an Efficient Diagnostic Tool for the Thoracic Surgeon?

Virtual bronchoscopy has emerged over the past decade as a potentially complementary investigation to conventional bronchoscopy in the diagnosis, grading, and monitoring of pulmonary disease. A meta-analysis reporting on the use of virtual bronchoscopy has not yet been performed. The primary aim of this study is to evaluate its diagnostic accuracy compared to the gold standard investigation of conventional bronchoscopy (fiberoptic or rigid). Quantitative data synthesis included the calculation of independent sensitivity and specificity, construction of summary receiver operating characteristic curves, pooled analysis, and sensitivity analysis. Seventeen studies were identified comprising 459 patients. The calculated pooled sensitivity was 84% (95% CI, 78% to 89%), specificity 75% (95% CI, 62% to 85%) and area under the curve was 0.92, which shows good diagnostic performance. Meta-analysis confirms virtual bronchoscopy is very discriminating in the evaluation of patients with significant airway stenosis that is due to a wide spectrum of pathologic conditions. It can potentially have a beneficial role in selected thoracic patients (with bronchoesophageal fistulas, postlung transplantation, anastomoses, and suspected foreign body aspiration).

Three-dimensional path planning for virtual bronchoscopy

Multidetector computed-tomography (MDCT) scanners provide large high-resolution three-dimensional (3-D) images of the chest. MDCT scanning, when used in tandem with bronchoscopy, provides a state-of-the-art approach for lung-cancer assessment. We have been building and validating a lung-cancer assessment system, which enables virtual-bronchoscopic 3-D MDCT image analysis and follow-on image-guided bronchoscopy. A suitable path planning method is needed, however, for using this system. We describe a rapid, robust method for computing a set of 3-D airway-tree paths from MDCT images. The method first defines the skeleton of a given segmented 3-D chest image and then performs a multistage refinement of the skeleton to arrive at a final tree structure. The tree consists of a series of paths and branch structural data, suitable for quantitative airway analysis and smooth virtual navigation. A comparison of the method to a previously devised path-planning approach, using a set of human MDCT images, illustrates the efficacy of the method. Results are also presented for human lung-cancer assessment and the guidance of bronchoscopy.

Virtual bronchoscopy for evaluation of airway disease

The data presented above indicate that VB is a novel and extremely useful modality for airway evaluation in patients who have benign and malignant disease. VB is noninvasive, with no additional radiation exposure relative to standard CT scans of the chest. Commercial software allows for the interactivity of 2D and 3D images. The ability to examine 2D and 3D anatomic detail from multiple directions enables precise assessment of intraluminal and extraluminal pathology. The authors' experience indicates that VB is a superb modality for assessing the length of airway stenoses and ascertaining airway patency distal to these lesions (Fig. 6). As such, VB has proven to be extremely useful for determining the feasibility of endobronchial procedures such as dilations, stent placements, and laser ablation of endobronchial tumors. Ferretti et al [27] observed that VB is an excellent noninvasive means for long-term monitoring of tracheobronchial stents. Furthermore, the authors have found VB useful for guiding the bronchoscopic evaluation of patients who have intermittent hemoptysis secondary to lesions in peripheral airways. The 3D anatomic detail provided by VB has proven useful for assessing the feasibility of lung-sparing procedures in patients who have limited pulmonary reserve and for sequentially evaluating treatment response in patients who have inoperable disease. Currently, the main limitation of VB pertains to its inability to evaluate the mucosal surface of the respiratory tract reliably. Although form can be detected, mucosal color, irregularity, or friability cannot be assessed. As such, VB cannot be used for routine surveillance of patients at high risk of developing airway malignancies. The development of novel aerosolized contrast agents or spectroscopic techniques that can discriminate benign versus malignant mucosal tissues might enhance the sensitivity and specificity of VB for the detection of preinvasive cancers within the respiratory tract.

3D airway segmentation via hyperpolarized 3He gas MRI by using scale-based fuzzy connectedness

Computerized segmentation of 3D tracheobronchial tree is a necessary first step for subsequent registration and analysis of pulmonary airway and vascular magnetic resonance (MR) images obtained by using hyperpolarized 3Helium gas and Gadolinium. The scientific and clinical implications of acquiring these data on the tracheobronchial tree (for studying ventilation, V) and on the coinciding pulmonary arterioles (for studying perfusion, Q), is the next frontier for static and dynamic pulmonary MRI. In this paper, we report an airway segmentation method from 3He MR images based on the scale-based fuzzy connectedness approach. Incorporated in this method are the pre-processing steps of inhomogeneity correction and intensity standardization. The basic sequential steps in the proposed airway segmentation method are: (1) image acquisition, (2) radio frequency field inhomogeneity correction, (3) standardization of MR image intensity scale, (4) seed specification, (5) scale-based fuzzy connected segmentation of airways, and (6) thresholding and binarization. The majority of these steps are automatically executed; others allow interaction through a graphical interface provided in the 3DVIEWNIX software system, in which the algorithms are implemented. The method achieves an overall precision of about 98% in terms of the extent of overlap in repeated segmentations. Its level of accuracy can be described by a true positive volume fraction of about 98% (considering manual delineation as the surrogate of true delineation), and a false negative and positive volume fraction of about 1%. The total operator and computational time required per study are on the average 2 and 20 min.

Automated lung segmentation in X-ray computed tomography: development and evaluation of a heuristic threshold-based scheme

RATIONALE AND OBJECTIVES

To develop and evaluate a reliable, fully-automated lung segmentation scheme for application in X-ray computed tomography.

MATERIALS AND METHODS

The automated scheme was heuristically developed using a slice-based, pixel-value threshold and two sets of classification rules. Features used in the rules include size, circularity, and location. The segmentation scheme operates slice-by-slice and performs three key operations: (1) image preprocessing to remove background pixels, (2) computation and application of a pixel-value threshold to identify lung tissue, and (3) refinement of the initial segmented regions to prune incorrectly detected airways and separate fused right and left lungs.

RESULTS

The performance of the automated segmentation scheme was evaluated using 101 computed tomography cases (91 thick slice, 10 thin slice scans). The 91 thick cases were pre- and post-surgery from 50 patients and were not independent. The automated scheme successfully segmented 94.0% of the 2,969 thick slice images and 97.6% of the 1,161 thin slice images. The mean difference of the total lung volumes calculated by the automated scheme and functional residual capacity plus 60% inspiratory capacity was -24.7 +/- 508.1 mL. The mean differences of the total lung volumes calculated by the automated scheme and an established, commonly used semi-automated scheme were 95.2 +/- 52.5 mL and -27.7 +/- 66.9 mL for the thick and thin slice cases, respectively.

CONCLUSION

This simple, fully-automated lung segmentation scheme provides an objective tool to facilitate lung segmentation from computed tomography scans.

Grading Airway Stenosis Down to the Segmental Level Using Virtual Bronchoscopy

OBJECTIVE

To assess the sensitivity of noninvasive virtual bronchoscopy based on multirow detector CT scanning in detecting and grading central and segmental airway stenosis using flexible bronchoscopic findings as the reference standard.

MATERIALS AND METHODS

In a blinded controlled trial, multirow detector CT virtual bronchoscopy and flexible bronchoscopy were used to search for and grade airway stenosis in 20 patients. CT scan data were obtained with a multirow detector CT scanner using 4 x 1 mm collimation. Flexible bronchoscopy findings were graded by a pulmonologist and served as the reference standard for 176 central airway regions (ie, trachea, main bronchi, and lobar bronchi) and 302 segmental airway regions. The extent of airway narrowing was categorized as grade 0 (no narrowing), grade 1 (< 50%), or grade 2 (> or =50%).

RESULTS

Flexible bronchoscopy revealed 30 stenoses in the central airways and 10 in the segmental airways. Virtual bronchoscopy detected 32 stenoses in the central airways (sensitivity, 90.0%; specificity, 96.6%; accuracy, 95.5%) and 22 in the segmental airways (sensitivity, 90.0%; specificity, 95.6%; accuracy, 95.5%). The number of false-positive findings was higher in the segmental airways (13 false-positive findings) than in the central airways (5 false-positive findings), which caused a lower positive predictive value for the segmental airways (40.9%) than for the central airways (84.4%). Flexible and virtual bronchoscopic gradings correlated better for central airway stenosis (r = 0.87) than for segmental airway stenosis (r = 0.61).

CONCLUSION

Although a high sensitivity was found for the detection of both central and segmental airway stenosis, the number of false-positive findings was higher for segmental airways. However, noninvasive multirow detector CT virtual bronchoscopy enables high-resolution endoluminal imaging of the airways down to the segmental bronchi.

Clinical epidemiology: diagnostic and prognostic tests

Recent studies of diagnostic and prognostic tests have commonly examined serological tests and new imaging techniques. Antifilaggrin antibodies have been found to be highly specific for the diagnosis of rheumatoid arthritis (RA), but uncertainty remains about the sensitivity of this test, particularly in early RA. Magnetic resonance imaging and ultrasound continue to be explored as methods to detect synovitis and erosions in RA. Several recent studies have confirmed the association between the human leukocyte antigen DRB1 shared epitope and worse radiographic outcomes in patients with RA. Interlaboratory variation in detecting autoantibodies remains a concern, as does overuse of tests for antineutrophil cytoplasmic autoantibodies.