Mosaic Attenuation Pattern: A Guide to Analysis with HRCT.

Mosaic attenuation pattern is commonly encountered on high-resolution computed tomography and has myriad causes. These diseases may involve small airways, vessels, alveoli, or interstitium, with some involving compartmental combinations. Small airways disease is caused by cellular bronchiolitis, infiltrated by inflammatory cells or constrictive bronchiolitis, resulting in fibrosis of the small airways. Any acute or chronic cause of ground-glass opacity can result in a mosaic pattern. Vascular causes of mosaic attenuation include chronic thromboembolic pulmonary hypertension and rarely other causes of pulmonary arterial hypertension. Ancillary CT findings along with the clinical history help narrow the differential diangosis. Biopsy is uncommonly required for definitiive diagnosis.

An 80-year-old woman with myelofibrosis and diffuse mosaic attenuation on chest computed tomography.

An 80-year-old woman with myelofibrosis sought evaluation for progressive dyspnea. Her past medical history included essential thrombocytosis, which transformed to myelofibrosis. Inspiratory computed tomography of chest showed diffuse mosaic attenuation with lymphadenopathy. Flexible bronchoscopy with lymph node and pulmonary parenchymal cryo biopsy revealed nodular deposits of extramedullary hematopoiesis in lung parenchyma and moderate to severe vascular medial and intimal thickening of pulmonary vasculature consistent with pulmonary parenchymal extramedullary hematopoiesis associated with pulmonary hypertension (a rare compensatory mechanism in myeloproliferative disorders). In this report, we explore the manifestations, pathogenesis, treatment, and prognosis of pulmonary extramedullary hematopoiesis reported in the literature.

Is the combination of bilateral pulmonary nodules and mosaic attenuation on chest CT specific for DIPNECH?

BACKGROUND: Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) is characterized by multifocal proliferation of pulmonary neuroendocrine cells. On chest CT, DIPNECH exhibits bilateral pulmonary nodules and mosaic attenuation in most patients. We sought to: (1) assess the specificity of this pattern (i.e., bilateral pulmonary nodules together with mosaic attenuation) for DIPNECH; (2) describe its differential diagnosis; and (3) identify the clinico-radiologic features that may help prioritize DIPNECH over other diagnostic considerations. METHODS: We searched the Mayo Clinic records from 2015 to 2019 for patients with bilateral pulmonary nodules and mosaic attenuation on CT who had a diagnostic lung biopsy. A thoracic radiologist reviewed all CT scans. Chi-square test was used for categorical variables, and odds ratios were utilized to measure the association between certain variables and DIPNECH. RESULTS: Fifty-one patients met our inclusion criteria; 40 (78%) were females and 34 (67%) were never-smokers. Median age was 65 (interquartile range 55-73) years. Lung biopsy was surgical in 21 patients (41%), transbronchial in 17 (33%), and transthoracic in 12 (24%); explanted lungs were examined in 1 (2%). Metastatic/multifocal cancer was the most common diagnosis, and was found in 17 (33%) cases. Bronchiolitis was diagnosed in 12 patients (24%), interstitial lung disease in 10 (20%), and DIPNECH in 5 (10%). Previous diagnosis of an obstructive lung disease (odds ratio 15.8; P = 0.002), and peribronchial nodular distribution on CT (odds ratio 14.4; P = 0.006) were significantly correlated with DIPNECH. Although statistical significance was not reached, DIPNECH nodules were more likely to display solid attenuations (80% vs. 67%, P = 0.45), and were more numerous; > 10 nodules were seen in 80% of DIPNECH cases vs. 52% in others (P = 0.23). Because DIPNECH primarily affects women, we analyzed the women-only cohort and found similar results. CONCLUSIONS: Various disorders can manifest the CT pattern of bilateral pulmonary nodules together with mosaic attenuation, and this combination is nonspecific for DIPNECH, which was found in only 10% of our cohort. Previous diagnosis of an obstructive lung disease, and peribronchial distribution of the nodules on CT increased the likelihood of DIPNECH vs. other diagnoses.

Hypersensitivity pneumonitis: Airway-centered pulmonary fibrosis on chest CT.

BACKGROUND: To evaluate the chest CT appearance of patients with a clinicopathologic diagnosis of hypersensitivity pneumonia. METHODS: IRB approval was obtained for a retrospective review of patients with a preoperative CT scan, a surgical pathology report from a transbronchial biopsy or wedge resection consistent with hypersensitivity pneumonitis, and a pulmonary consultation, which also supported the diagnosis. The pathology report was evaluated for granulomas, airway-centered fibrosis, microscopic honeycombing, and fibroblast foci. The medical records were reviewed for any known antigen exposure. Patients were separated into two groups; those with and without a known antigen exposure. The CT scans were assessed for distribution of fibrosis: upper lobe or lower lobe predominance, airway-centered versus peripheral distribution, three-density pattern, and honeycombing. RESULTS: 264 pathology reports included the term chronic hypersensitivity pneumonitis (CHP). Thirty-eight of the patients had a pulmonologist who gave the patient a working diagnosis of CHP. The average age of these patients was 64 years, and 21/38 were women. Seventeen of the 38 patients had at least one antigen exposure described in the medical records. All the patients had fibrosis along the airways on chest CT. Both known antigen exposure and no known antigen patients had upper and lower lung-predominant fibrosis. There were more patients with hiatal hernias in the unknown antigen group. Honeycombing was an uncommon finding. CONCLUSION: Airway-centered fibrosis was present on chest CT in all 38 patients with CHP (100%), with or without known antigen exposure.

A 68-year-old woman with a diagnosis of asthma and multiple fleeting pulmonary nodules- a case report.

Diffuse idiopathic pulmonary neuroendocrine cell (DIPNECH syndrome) remains unfamiliar to most clinicians even though it was first described almost 30 years ago. Diagnosis is usually confirmed histopathologically after lung biopsy, but often, a diagnosis or suspected diagnosis can be made radiographically. In this paper, we present a case report of a 68-year-old female with shortness of breath and fleeting pulmonary nodules observed on chest CT scan. She was initially misdiagnosed with asthma based on an abnormal pulmonary function test which revealed an obstructive ventilatory defect. The classic radiographic findings of DIPNECH syndrome and the typical patient demographics that should arouse suspicion of a DIPNECH diagnosis were also illustrated. DIPNECH syndrome is a clinicopathological syndrome whereas focal NECH is a pathological diagnosis that is often made incidentally on histological examination and is encountered in a variety of settings, including in resected carcinoid tumors, in the context of reactive changes concomitant with infection, in metastatic cancer, radiation pneumonitis, intra-lobar sequestration, smokers, interstitial lung disease, and lung adenocarcinoma. There are no proven treatments for DIPNECH syndrome. In patients with obstructive ventilatory symptoms, bronchodilators with inhaled steroids are usually prescribed. Some severe cases may require parenteral steroids. Somatostatin analogs (SSA) have also been used in some cases with mixed results. Rapamycin has been used in several cases based on the purported activation of the mammalian target of rapamycin (mTOR) in DIPNECH. Some patients with large carcinoid tumors may benefit from resection.

[A case of diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) syndrome]. / Un cas clinique de syndrome d'hyperplasie neuroendocrine pulmonaire diffuse idiopathique (DIPNECH).

INTRODUCTION: DIPNECH is a strictly histological entity according to the WHO 2015 classification and is considered to be at pre-neoplastic risk. It has been proposed that DIPNECH syndrome should be used to describe patients have clinical symptoms, an obstructive ventilatory disorder and compatible radiological abnormalities. The diagnosis is histological and usually based on a surgical lung biopsy. CASE REPORT: We report the case of a 58-year-old woman with a chronic cough for over 20years who had an obstructive airway pattern on spirometry. Diagnoses of asthma and COPD had been discussed. After 7years of follow-up, the DIPNECH hypothesis was evoked on the scanning aspect of mosaic attenuation, expiratory trapping and micronodules, which was subsequently confirmed by surgical pulmonary biopsy. CONCLUSION: It is necessary to consider the possibility of this rare disease in order to avoid inappropriate treatments and in the hope that future therapeutic advances (somatostatin analogs, mTOR inhibitors) improve patients' experience and the progression of respiratory function.

Clinical profile and course of children with postinfectious bronchiolitis obliterans from a tertiary care hospital.

BACKGROUND: Postinfectious bronchiolitis obliterans (PIBO) is a chronic obstructive lung disease with scanty information in literature on etiology, clinical profile, treatment, and outcome. OBJECTIVE: The objective of the study is to describe the clinical profile and course of children diagnosed with PIBO. METHODS: A chart review of children below 18 years of age diagnosed as PIBO over the past 9 years was carried out. Details of clinical profile, laboratory investigations, imaging, treatment received, and outcome were recorded. RESULTS: Eight children (boys 4) with PIBO were identified. Median (interquartile range [IQR]) age at the first episode of acute severe bronchiolitis such as illness and diagnosis of PIBO was 15 (6, 23.5) and 30 (16.5, 60) months, respectively, indicating a delay in diagnosis. The most common symptoms were recurrent episodes of cough (100%), fast breathing (100%), wheezing (87.5%), and fever (62.5%). Median (IQR) number of hospitalizations and episodes of antibiotic use prior to diagnosis were 2.5 (2, 5.5) and 2 (2, 4), respectively. Three (37.5%) children received mechanical ventilation during previous hospitalizations. Chest computed tomography revealed mosaic attenuation in 8 (100%), ground-glass opacities in 2 (25%), and bronchial wall thickening in 2 (25%). After diagnosis, 7 received oral steroids, 7 received hydroxychloroquine, 5 received azithromycin, and 2 received azathioprine. The median (IQR) duration of follow-up (n = 6) was 6 (1.5, 9.5) months. Median (IQR) number of pulmonary exacerbations in follow-up was 2 (1, 5). CONCLUSION: PIBO is still an under-recognized entity with substantial delay in diagnosis and unnecessary use of antibiotics. Clinical course with imaging findings may help to diagnose and manage this entity.

An Algorithmic Approach to the Interpretation of Diffuse Lung Disease on Chest CT Imaging: A Theory of Almost Everything.

We propose an algorithmic approach to the interpretation of diffuse lung disease on high-resolution CT. Following an initial review of pertinent lung anatomy, the following steps are included. Step 1: a preliminary review of available chest radiographs, including the "scanogram" obtained at the time of the CT examination. Step 2: a review of optimal methods of data acquisition and reconstruction, emphasizing the need for contiguous high-resolution images throughout the entire thorax. Step 3: initial uninterrupted scrolling of contiguous high-resolution images throughout the chest to establish the quality of examination as well as an overview of the presence and extent of disease. Step 4: determination of one of three predominant categories - primarily reticular disease, nodular disease, or diseases associated with diffuse alteration in lung density. Based on this determination, one of the three following Steps are followed: Step 5: evaluation of cases primarily involving diffuse lung reticulation; Step 6: evaluation of cases primarily resulting in diffuse lung nodules; and Step 7: evaluation of cases with diffuse alterations in lung density including those with diffusely diminished lung density vs those with heterogenous or diffusely increased lung density, respectively. It is anticipated that this algorithmic approach will substantially enhance initial interpretations of a wide range of pulmonary disease.

The clinico-radiological profile of obliterative bronchiolitis in a tertiary care center.

BACKGROUND: Obliterative bronchiolitis (OB) forms a major proportion of chronic airway diseases (CADs). OB is often misdiagnosed and included under the umbrella term 'chronic obstructive pulmonary disease'. We set out to identify the proportion of OB cases among the CADs and study the clinical profile of OB. MATERIALS AND METHODS: This prospective, observational study noted all patients with Chronic airway obstruction (CAO), of which patients with OB were included and the clinical profile was studied. Data were subjected to statistical analysis. RESULTS: Five hundred patients with CAO were noted in the study period, of which 115 patients were found to be OB amounting to a prevalence of 23%. The mean age of presentation was 51.8 years (standard deviation 12.1) with a male-female ratio of 1:1. The most common etiology for OB was as sequelae to past treated pulmonary tuberculosis (PTB) seen in 82 patients (71%) of cases. Dyspnea in 114 patients (99%) and productive cough in 110 patients (95%) were the predominant symptoms. Postexercise desaturation was seen in all 115 patients (100%). Forty-six patients (43%) presented with either Type 1 or Type 2 respiratory failure. Spirometry showed obstructive pattern in 68 patients (59%) with forced expiratory volume in 1 s/forced vital capacity (FEV1/FVC) ratio of <70% and FEV1 <70% postbronchodilator and mixed pattern in 47 patients (41%) with a reduction in both FEV1 and FVC and normal FEV1/FVC ratio. There was the presence of mosaic attenuation on high-resolution computerized tomography (HRCT) of the chest with expiratory scans in all 115 patients (100%). Pulmonary hypertension was documented in 109 patients (95%). CONCLUSION: OB is one of the major causes of CAO. HRCT of the chest with expiratory scans plays a important role in the diagnosis. Early diagnosis can prevent irrevocable complications.

Mosaic attenuation pattern in non-contrast computed tomography for the assessment of pulmonary perfusion in chronic thromboembolic pulmonary hypertension.

BACKGROUND: Chronic thromboembolic pulmonary hypertension (CTEPH) is difficult to diagnose as patients rarely present with specific symptoms. However, a mosaic attenuation pattern (MAP) in chest computed tomography (CT) suggests CTEPH. Areas of increased attenuation are not always visible using default CT settings for the lung. Thus, we examined the utility of non-contrast CT imaging with new settings focusing on MAP (CTMosaic) for the assessment of pulmonary perfusion in patients with CTEPH. The regional perfusion defects visualized using CTMosaic and single-photon-emission CT with fusion of CT images (SPECT/CT) were compared. METHODS: Twenty-seven patients with CTEPH (20 women; aged 62.8±7.9 years) underwent imaging with non-contrast CT and SPECT/CT. We converted non-contrast mediastinal CT images into various CT window settings to identify the MAP, and the CT window setting that could most easily identify the MAP was defined as CTMosaic. We then scored and compared lung segments depending on the degree of perfusion on CTMosaic and SPECT/CT. RESULTS: CTMosaic was identified as the CT window setting in which the window level was -800 Hounsfield units (HU), and the window width was 200 HU. Using CTMosaic, MAP was detected in 366 of 486 segments (75.3%). The agreement between CTMosaic and perfusion defects on SPECT/CT was 84.9%. Weighted kappa statistics demonstrated a good agreement between the two examinations (κ=0.605, 95% confidence interval, 0.502-0.707). CONCLUSIONS: The CTMosaic setting can easily identify an MAP in CTEPH patients. Therefore, this may be useful as a simple and cost-effective evaluation method for blood distribution in patients with CTEPH.

Recognition of Small Airways Obstruction in Asthma and COPD - The Road Less Travelled.

The small airways, once regarded as the silent zone in the air conducting system of the lungs are now known to be one of the initial sites of involvement in diseases like asthma and Chronic Obstructive Pulmonary Disease (COPD). Identification of the involvement of distal airways in these diseases is often difficult to assess, clinically as well as by conventional pulmonary function tests and therefore, usually remains undiscovered in early stages. Early recognition of their involvement in asthma and COPD and timely management may reduce long term morbidity in these conditions. This article aims to highlight the relatively lesser recognized facts about small airways involvement in asthma and COPD and role of imaging and newer modalities for detection.

COMPARISON BETWEEN SEDATION AND GENERAL ANESTHESIA FOR HIGH RESOLUTION COMPUTED TOMOGRAPHIC CHARACTERIZATION OF CANINE IDIOPATHIC PULMONARY FIBROSIS IN WEST HIGHLAND WHITE TERRIERS.

Canine idiopathic pulmonary fibrosis is a progressive interstitial lung disease mainly affecting West Highland white terriers. Thoracic high-resolution computed tomographic (T-HRCT) findings for Canine idiopathic pulmonary fibrosis acquired under general anesthesia have been described previously. However, the use of general anesthesia may be contraindicated for some affected dogs. Sedation may allow improved speed and safety, but it is unknown whether sedation would yield similar results in identification and grading of Canine idiopathic pulmonary fibrosis lesions. The aim of this prospective, observational, method-comparison, case-control study was to compare findings from T-HRCT images acquired under sedation versus general anesthesia for West Highland white terriers affected with Canine idiopathic pulmonary fibrosis (n = 11) and age-matched controls (n = 9), using the glossary of terms of the Fleischner Society and a scoring system. Ground-glass opacity was identified in all affected West Highland white terriers for both sedation and general anesthesia acquisitions, although the Ground-glass opacity extent varied significantly between the two acquisitions (P < 0.001). Ground-glass opacity was the sole lesion observed in control dogs (n = 6), but was less extensive compared with affected West Highland white terriers. Identification and grading of a mosaic attenuation pattern differed significantly between acquisitions (P < 0.001). Identification of lesions such as consolidations, nodules, parenchymal and subpleural bands, bronchial wall thickening, and bronchiectasis did not differ between acquisitions. The present study demonstrated that T-HRCT obtained under sedation may provide different information than T-HRCT obtained under general anesthesia for identification and grading of some Canine idiopathic pulmonary fibrosis lesions, but not all of them. These differences should be taken into consideration when general anesthesia is contraindicated and sedation is necessary for evaluating West Highland white terriers with Canine idiopathic pulmonary fibrosis.

A systematic approach to interpretation of heterogeneous lung attenuation on computed tomography of the chest.

Computed tomography (CT) chest is widely used as an adjunct to clinical examination and pulmonary function tests in the evaluation of unexplained dyspnoea. In such patients, heterogeneous lung attenuation is a common finding on CT. Heterogeneous lungs can be caused by varying regional aeration, varying regional perfusion, and ground glass opacities (GGO) representing airspace or interstitial pathology. It does not serve the referring clinicians or the patients well if the radiology report simply mentions the heterogeneity of the lungs without due analysis of the cause of heterogeneity and a meaningful differential diagnosis. Therefore, it is imperative for the radiologist and the treating pulmonologist to have an in-depth understanding of the pathogenesis of pulmonary heterogeneity. This, in conjunction with clinical data, can narrow the differential diagnosis or, at times, lead to specific diagnoses. The purpose of this review is to familiarize readers with the CT representation of heterogeneities in aeration and perfusion of the lung, relate patterns of GGO to underlying pathology, and provide illustrative case studies highlighting the radiological approach to heterogeneous lungs.