High-resolution Computed Tomography Signs Research Articles

Predicting invasiveness of ground-glass nodules in lung adenocarcinoma: based on preoperative 18 F-fluorodeoxyglucose PET/computed tomography and high-resolution computed tomography.

This study was conducted to explore the differential diagnostic value of PET/computed tomography (PET/CT) combined with high-resolution computed tomography (HRCT) in predicting the invasiveness of ground-glass nodules (GGNs). This retrospective analysis included 67 patients (mean age 62.5 ± 8.4, including 45 females and 22 males) with GGNs who underwent preoperative 18 F-fluorodeoxyglucose ( 18 F-FDG) PET/CT and HRCT examinations between January 2018 and October 2022. Based on the postoperative pathological results of lung adenocarcinoma, the patients were classified into two groups: invasive adenocarcinoma (IAC) and non-IAC. Besides, the clinical and imaging information of these patients was collected. HRCT signs include the existence of air bronchial signals, vascular convergence, pleural indentation, lobulation, and spiculation. Moreover, the diameter of solid components (D Solid ), diameter of ground-glass nodules (D GGN ), and computed tomography values of ground-glass nodules (CT GGN ) were measured concurrently. Furthermore, the mean standardized uptake value, maximal standardized uptake value (SUVmax), metabolic tumor volume, and total lesion glycolysis were assessed during PET/CT. Associations between invasiveness and these factors were evaluated using univariate and multivariate analyses. The results of logistic regression analysis demonstrated that D GGN , D Solid , consolidation tumor ratio (CTR), CT GGN , and SUVmax were independent predictors in the IAC group. The combined diagnosis based on these five predictors revealed that area under the curve was 0.825. The D GGN , D Solid , CTR, CT GGN , and SUVmax in GGNs were independent predictors of IAC, and combining 18 F-FDG PET/CT metabolic parameters with HRCT may improve the predictive value of pathological classification in lung adenocarcinoma.

Imaging in the diagnosis and management of fibrosing interstitial lung diseases.

High-resolution computed tomography (HRCT) plays a pivotal role in the diagnosis and management of interstitial lung diseases (ILDs), particularly given the approval of antifibrotic agents for conditions like idiopathic pulmonary fibrosis and progressive pulmonary fibrosis. Diagnosing fibrotic pulmonary disorders through HRCT involves a detailed and methodical examination. The identification of specific lung tissue changes, including ground-glass opacities and reticulation, along with signs of fibrosis like honeycombing, traction bronchiectasis and lung volume loss, establishes clear HRCT patterns indicative of various ILDs. The reliability of these patterns in predicting pathological conditions depends largely on the clinical context. For instance, when a usual interstitial pneumonia pattern is present, the predictive value of this diagnosis is so high that a lung biopsy is considered to be redundant. This review intends to delineate the HRCT signs of fibrosis, elucidate the specific radiological patterns of fibrotic lung diseases, and identify the clinical circumstances under which these patterns emerge. Additionally, we introduce and discuss novel imaging techniques that hold promise for the diagnosis, screening and early detection of ILDs.

Differential Diagnosis of Fibrotic Hypersensitivity Pneumonitis with Its Non-Fibrotic Phenotype and Usual Interstitial Pneumonia During High-Resolution Computed Tomography

Background. Diagnosis of hypersensitivity pneumonitis (HP) using high-resolution computed tomography (HRCT) is not an easy task. The most difficult aspects of the disease include differential diagnosis of its fibrotic (fHP) and non-fibrotic (nfHP) phenotypes, as well as their differentiation from usual interstitial pneumonia (UIP) in idiopathic pulmonary fibrosis. The determination of fibrous changes at an early stage of development can significantly accelerate the beginning of antifibrotic therapy and improve the prognosis.Objective: to identify key HRCT signs for reliable differentiation of fHP and nfHP, to carry out differential diagnostics between fHP and UIP.Material and methods. The data of 73 patients with morphologically verified HP, in whom HRCT had been performed, were retrospectively analysed. In 21 patients, nfHP was determined, and in 52 patients fHP was identified. The comparison group consisted of 24 patients with a typical radiological UIP pattern. The analysis of the changes detected during HRCT was carried out by qualitative and semi-quantitative methods. The significance of qualitative differences in a sign manifestation was assessed by Fisher’s exact test, semi-quantitative differences were evaluated using Mann–Whitney test.Results. The results of the study allow to assume, that the presence and degree of manifestation of certain HRCT signs significantly differ between the selected groups of patients in qualitative and/or semi-quantitative terms. In cases of НP, the distribution of changes was mostly uniform and diffuse, with no clear predominance in certain lobes. In UIP, diffuse craniocaudal distribution took place, and in the axial plane, the changes were mainly subpleural in nature.Conclusion. Based on the results of the study, it can be assumed that fHP significantly differs from nfHP in such features as the presence and degree of manifestation of ground glass and honeycombing symptoms, reticular changes and traction bronchiectases. When comparing the fHP and UIP groups, the distinctive signs of fHP were centrilobular nodules, mosaic pattern, as well as diffuse axial sign distribution.

Can a chest HRCT-based crash course on COVID-19 cases make inexperienced thoracic radiologists readily available to face the next pandemic?

ObjectiveTo test the inter-reader agreement in assessing lung disease extent, HRCT signs, and Radiological Society of North America (RSNA) categorization between a chest-devoted radiologist (CR) and two HRCT-naïve radiology residents (RR1 and RR2) after the latter attended a COVID-19-based chest high-resolution computed tomography (HRCT) “crash course”. MethodsThe course was built by retrospective inclusion of 150 patients who underwent HRCT for COVID-19 pneumonia between November 2020 and January 2021. During a first 10-days-long “training phase”, RR1 and RR2 read a pool of 100/150 HRCTs, receiving day-by-day access to CR reports as feedback. In the subsequent 2-days-long “test phase”, they were asked to report 50/150 HRCTs with no feedback. Test phase reports of RR1/RR2 were then compared with CR using unweighted or linearly-weighted Cohen's kappa (k) statistic and intraclass correlation coefficient (ICC). ResultsWe observed almost perfect agreement in assessing disease extent between RR1-CR (k = 0.83, p < 0.001) and RR2-CR (k = 0.88, p < 0.001). The agreement between RR1-CR and RR2-CR on consolidation, crazy paving pattern, organizing pneumonia (OP) pattern, and pulmonary artery (PA) diameter was substantial (k = 0.65 and k = 0.68), moderate (k = 0.42 and k = 0.51), slight (k = 0.10 and k = 0.20), and good-to-excellent (ICC = 0.87 and ICC = 0.91), respectively. The agreement in providing RSNA categorization was moderate for R1 versus CR (k = 0.56) and substantial for R2 versus CR (k = 0.67). ConclusionHRCT-naïve readers showed an acceptable overall agreement with CR, supporting the hypothesis that a crash course can be a tool to readily make non-subspecialty radiologists available to cooperate in reading high burden of HRCT examinations during a pandemic/epidemic.

The Importance of High-Resolution Computed Tomography in the Early Diagnosis of Fibrotic Hypersensitivity Pneumonitis

Objective: to determine the high-resolution computed tomography (HRCT) signs and their combinations, suggesting the presence of fibrotic hypersensitivity pneumonitis (FHP). Material and methods. The study included 52 patients with pathologically verified diagnosis of FHP who were examined according to the 2021 consensus criteria. All patients had lung HRCT no more than 4 months prior to lung biopsy. The analysis of the changes revealed during HRCT was carried out by qualitative and semi-quantitative methods. The presence of individual signs, the degree of their severity (as percentage relative to the volume of the entire lung tissue) and the features of distribution in the axial and longitudinal planes were taken into account. To search for significant combinations of HRCT signs, a correlation analysis was carried out. Results. The most common HRCT signs in the examined group of FHP patients were reticular changes (96 %) and ground glass opacity (88 %). Most of the patients had signs that did not correspond to the picture of “typical FHP”, such as ground glass and emphysema. Relatively rare cases were centrilobular lesions (46.2 %) and mosaic attenuation (52 %), which are traditionally part of the “typical FHP” picture. In 22 cases (42.3 %) there were signs of emphysema, the presence of which significantly complicated the interpretation of HRCT data even in the cases of characteristic signs of FHP. Correlations of almost all HRCT signs were weak. The most common combinations of features were ground glass + reticular changes, emphysema + honeycombing, reticular changes + bronchiectasis. The combination of ground glass and reticular changes had a moderate correlation, but it has low specificity. Conclusion. The HRCT picture of changes in the lungs among patients with a morphologically verified diagnosis of FHP has important features. A weak correlation between the signs does not allow to identify their combinations that can help in the early diagnosis of FHP with sufficient reliability.

High resolution computed tomography signs lead an early diagnosis of COVID-19

High resolution computed tomography signs lead an early diagnosis of COVID-19

High resolution computed tomography signs lead an early diagnosis of COVID-19

Introduction: The novel coronavirus disease 2019 (COVID-19) has huge impact on public health. RT-PCR of respiratory samples is generally accepted confirmatory test which can miss several cases due to various factors. Case description: A 32-years-old male without any co-morbidity presented with complaints of cough and fever was negative for Reverse Transcription Polymerase Chain Reaction (RT-PCR) on two separate occasions on two different centres died and the last sample sent on 30th day of admission tested positive for RT-PCR. Radiologist reported the CT Chest signs as highly likely case of COVID-19 on the day of admission. Clinical significance: Radiological signs on CT chest can contribute in the diagnostic workup of CIVID-19. Conclusion: Radiological signs reported in suspected COVID-19 should be noticed and given adequate weightage in conditions where the other laboratory tests are negative.

Spectrum of Diffuse Parenchymal Lung Diseases Other Than Idiopathic Pulmonary Fibrosis Based on Clinical, Radiological and Histopathological Correlation

Background: Multiple modalities are available for diagnosis of diffuse parenchymal lung diseases. High-resolution roles computed tomography of lung was well established in formulating initial cases diagnosis with diffuse parenchymal lung diseases. Major utilities of transbronchial lung biopsy rests in making possibilities specific diagnosis diffuse parenchymal lung diseases cases and avoiding a surgical lung biopsy. Objectives and Methods: The aim of this work was to study the spectrum of diffuse parenchymal lung diseases other than idiopathic pulmonary fibrosis based on clinical, radiological and histopathological correlation. This study included 120patients with chest high resolution computed tomography signs of diffuse parenchymal lung diseases not consistent with idiopathic pulmonary fibrosis. Flexible bronchoscopy was done with the bronchoalveolar lavage and transbronchial lung biopsy were obtained. The samples were processed for cyto-histopathology. Results: Nodular pattern (73.33%) was the most high-resolution computed tomography (HRCT) predominant pattern followed by ground glass pattern (45%) and reticular pattern (26.67%). The most frequent diagnosis was sarcoidosis(40.83%) followed by hypersensitivity pneumonitis (20%). The overall diagnostic yield of transbronchial lung biopsy was 79.1% (95/120). All differential diagnoses showed extreme matching between HRCT and histopathology. Conclusion: HRCT is a non-invasive method to evaluate and diagnose patients with diffuse parenchymal lung diseases. Transbronchial lung biopsy found to have reliable yields in with diffuse parenchymal lung diseases diagnosis.

Corona sign in the lungs in coronavirus disease 2019: Case report of a new diagnostic sign

The CoronaVirus Disease 2019 (COVID-19) pandemic continues raging across the world well into its second year. High Resolution Computed Tomography (HRCT) has become an extremely valuable tool in diagnosis of the disease, assessing disease severity and prognosis for patients and also as a valuable adjunct to RT-PCR. Many of the HRCT signs of COVID-19 are non-specific and overlapping with other viral pneumonias, however a few signs though uncommon, are being found to be relatively diagnostic for COVID-19. We present such a new diagnostic sign which we call as the ‘Corona sign’ after the disease causing it.

Transthoracic ultrasonographic features of typical high-resolution computed tomography signs of interstitial lung diseases

Objective: To investigate the accuracy of bedside transthoracic lung ultrasonography (TLU) in different typical high resolution computed tomography (HRCT) signs of interstitial lung diseases (ILDs). Methods: Fifty patients first diagnosed with ILDs were enrolled from January 2016 to December 2018. There were 21 males and 29 females. The mean age was (56±14) years(rang 42-73 years). TLU was performed in inspiration for the characters of A-lines and B-lines as well as pleural at anterior, lateral and dorsal chest walls, respectively. HRCT was selected at three levels according to the upper, middle, and lower lung fields. The range of each level needing to be evaluated corresponded to the TLU scanning field one by one, and recording the signs of HRCT. Early change of ILDs was definite as the HRCT score was no more than 1 and no honeycomb was present. The correlation between A-lines, B-lines, pleural abnormal and HRCT signs was evaluted. Spearman's correlation coefficient was used to evaluate the relationship between B-lines and HRCT score. Results: The sensitivity and specificity of A-lines for HRCT normality were 83.9% and 84.9%, respectively. Coincidence rate was 84.6%. The sensitivity and specificity of B-lines for HRCT abnormality were 84.9% and 83.9%, respectively. Coincidence rate was 84.6%. Interlobular septal thickening shadow had fewer B-lines and narrower interval than other HRCT signs, while the other HRCT signs had no differences in B-lines. And the sensitivity and specificity of B-lines for detection the early change of HRCT in ILDs were 89.5% and 89.2%, respectively. Coincidence rate was 89.3%. A positive correlation was found between the number of B-lines and HRCT scores (R=0.827, P<0.001), and the width of B-lines and HRCT score (R=0.951, P<0.001). Meanwhile, a negative correlation was found between the interval of B-lines and HRCT score (R=-0.831, P<0.001). The sensitivity and specificity of TLU for HRCT pleural abnormality were 100.0% and 90.0%, respectively. Coincidence rate was 93.6%. Conclusions: TLU showed high sensitivity and specificity in finding interstitial changes of the lung. It gives a new view on the diagnostic possibilities of ILDs and may be used to evaluate the severity and the therapeutic effect of treatment. However, TLU could not differentiate HRCT signs of ILDs.

Volume Assessment in Hemodialysis: A Comparison of Present Methods in Clinical Practice with Sonographic Lung Comets.

Dry weight assessment in dialysis patients remains a challenging endeavor owing to the limitations of the available methods for volume assessment. Lung ultrasound is emerging as an invaluable tool to assist in the appropriate assessment and assignment of dry weight. The objectives of this study are (1) to determine the reliability of clinical signs and symptoms for volume assessment, (2) to compare lung ultrasound with High Resolution Computed Tomography (HRCT) chest-A noninvasive gold standard tool for detecting pulmonary congestion and with inferior vena cava diameter (IVCD) – another time-tested volume assessment method, and (3) to analyze if lung ultrasound could detect dialysis induced fluid status variations. The cross-sectional study involves 50 patients on maintenance hemodialysis. Lung ultrasound for B line estimation and ultrasonographic measurement of IVCD performed before and after hemodialysis by a nephrologist trained in ultrasonography. Limited HRCT was obtained just before hemodialysis. Edema, crackles, and dyspnea had a poor sensitivity of 37.9%, 11.5%, and 52.6%, respectively, to detect clinically significant pulmonary congestion by lung ultrasound. A highly significant correlation was obtained between B-line score and HRCT signs of pulmonary congestion (P < 0.001) before dialysis. B lines showed statistically significant reduction with dialysis. The absolute reduction of B lines showed significant correlation with ultrafiltration volume and weight loss. Bedside lung ultrasound appears a sensitive tool for evaluating real-time changes in extravascular lung water and would serve to optimize volume status in dialysis patients.

Contrast analysis of the relationship between the HRCT sign and new pathologic classification in small ground glass nodule-like lung adenocarcinoma

To perform contrast analysis of the relationship between high-resolution computed tomography (HRCT) signs and new pathologic classification of small GGNs-like lung adenocarcinoma. The HRCT data from 145 pathologically confirmed cases of small GGNs of lung adenocarcinoma were analysed retrospectively. The 145 cases of GGNs were divided into pre-invasive (PI) group (n = 46), micro-invasive adenocarcinoma (MIA) group (n = 48), and invasive adenocarcinoma (IAC) group (n = 51). HRCT imaging sign of GGNs in each group was assessed and compared. Significant differences in GGN size were found among the three groups (P < 0.05). The presence of a tumour-lung interface in the MIA and IAC groups was significantly higher than that in the PI group (P < 0.05), but no significant difference was found between the MIA and IAC groups. The presence of a pleural indentation sign in the IAC group was significantly higher than that in the other two groups (P < 0.05), but no significant difference was noted between the latter two groups. Significant differences were found in the lobulated and spicule signs among the three groups (P < 0.05). The presence of a microvascular sign in the MIA and IAC groups was significantly higher than that in the PI group (P < 0.05). No significant difference was found in the GGN density, vacuole sign, air bronchus sign and notch sign among the three groups. The HRCT signs of GGNs could be used to differentiate among pre-invasive lesions, micro-invasive lesions and invasive lung adenocarcinoma.

Ultrasound signs of pulmonary fibrosis in systemic sclerosis as timely indicators for chest computed tomography

Objectives: Systemic sclerosis (SSc) patients in the early stages of pulmonary fibrosis (PF) often have few or no symptoms, normal to borderline pulmonary function tests, and negative chest X-ray (CXR); high-resolution computed tomography (HRCT) is the only reliable means of detecting the early signs of PF. However, thoracic ultrasound (TUS) enables detection of pleural thickening, pleural/subpleural nodules, and other subpleural lung abnormalities across 70% of the subpleural surface. We reassessed concordance between TUS abnormalities and HRCT findings in SSc patients, to see whether TUS pleural line thickness (normally < 3.0 mm) could be used to earmark those with asymptomatic PF for timely HRCT assessment.Method: In total, 175 SSc patients (nine males, 166 females), aged 46.46 ± 15.33 years, were given CXR, TUS, HRCT, echocardiography, and pulmonary function tests.Results: In the 26 patients without HRCT signs of PF, pleural line thickness was ≤ 3.0 mm. In diffuse SSc, 97/137 patients showed pleural line thickening (between 3.0 and 5 mm) and subpleural nodules in 32/97; and 35/137 showed major pleural line thickening (≥ 5.0 mm) with nodules, with good concordance with HRCT patterns indicating lung fibrosis severity. HRCT was normal in 5/137, with pleural line thickness ≤ 3.0 mm.Conclusions: TUS imaging of pleural/subpleural structures can detect ultrasonographic signs of initial PF prior to the onset of respiratory symptoms and function test abnormalities and, together with current criteria, could thereby enable exclusion of PF in SSc patients. Indicating some patients for selective referral to HRCT can thereby delay unwarranted procedures, provided that pulmonary function and TUS images are stable.

A Surgical Lung Biopsy Case of Pulmonary Veno-occlusive Disease Associated with Limited Cutaneous Systemic Sclerosis

Pulmonary veno-occlusive disease (PVOD), a rare form of pulmonary arterial hypertension (PAH) characterized by a progressive obstruction of small pulmonary veins, is both difficult to diagnose and treat effectively. We reported a case of limited cutaneous systemic sclerosis complicated with PAH in which early definitive diagnosis of PVOD was made by surgical lung biopsy. A 53-year-old Japanese woman, with no history of smoking, was admitted to our hospital because of dry cough and progressive dyspnea. She had Raynaud’s phenomenon, gastroesophageal reflux and skin sclerosis and she was positive for anticentromere antibody. Chest high-resolution computed tomography (HRCT) revealed diffuse centrilobular ground-glass opacities and septal lines in addition to mediastinal lymph node enlargement; radiographic triad of HRCT signs of PVOD. PAH was found by right heart catheterization. Although limited cutaneous systemic sclerosis-associated PAH was diagnosed, histological findings obtained by surgical lung biopsy showed not only wall thickening of muscular arteries and arterioles but diffuse occlusion of pulmonary venules, that is, PVOD. In addition, pleuritis and limited, mild cellular interstitial pneumonia was also observed. First-line corticosteroid therapy and careful combination therapy with sildenafil and ambrisentan initially stabilized her symptoms and pulmonary hemodynamics, but she died due to cardiac arrest approximately 2.5 years after initiating PAH therapy. The need to establish a correct and early diagnosis of PVOD is important because of the impaired prognosis of these patients and their risk of developing severe pulmonary edema with specific PAH therapy. HRCT is a useful noninvasive diagnostic modality in the evaluation of suspected PVOD.

Computed tomography findings of pulmonary venoocclusive disease in scleroderma patients presenting with precapillary pulmonary hypertension

Pulmonary venoocclusive disease (PVOD) is an uncommon form of pulmonary hypertension (PH) characterized by obstruction of small pulmonary veins. Pulmonary venous involvement has been reported in pathologic assessment of patients with systemic sclerosis (SSc) presenting with precapillary PH. High-resolution computed tomography (HRCT) of the chest is a noninvasive diagnostic tool used to screen for PVOD. No HRCT data are available on SSc patients with precapillary PH. We undertook this study to evaluate the frequency and effect on prognosis of HRCT signs of PVOD in SSc patients with precapillary PH. We reviewed chest HRCT data from 26 SSc patients with precapillary PH and 28 SSc patients without pulmonary arterial hypertension (PAH) or interstitial lung disease (ILD). The radiographic triad of HRCT signs of PVOD (lymph node enlargement [57.7% versus 3.6%], centrilobular ground-glass opacities [46.2% versus 10.7%], and septal lines [88.5% versus 7.1%]) was significantly more frequent in SSc patients with precapillary PH than in SSc patients without PAH or ILD (all P < 0.005). Indeed, 61.5% of SSc patients with precapillary PH had ≥ 2 of these signs. Cardiomegaly (P < 0.0001), pulmonary artery enlargement (P < 0.0001), and pericardial effusion (P < 0.0005) were also significantly more frequent in SSc patients with precapillary PH. Pulmonary venous involvement was histologically confirmed in 2 patients with radiographic signs of PVOD. The presence of ≥ 2 radiographic signs of PVOD was associated with the occurrence of pulmonary edema after initiation of PAH-specific therapy (in 8 of 16 patients) and with more rapid progression from diagnosis of PH to death. HRCT signs of PVOD are frequently observed in SSc patients with precapillary PH, correlated with histologic assessment, and were associated with a high risk of pulmonary edema.

Association of findings in flow‐volume spirometry with high‐resolution computed tomography signs in asbestos‐exposed male workers

Disorders of pulmonary tissue and pleura are visualized by findings in high-resolution computed tomography (HRCT), and the impairment caused by these findings is assessed by pulmonary function tests. Our aim was to determine how some commonly used spirometric variables are related to certain HRCT signs, in order to find out which HRCT signs are associated with restrictive and which with obstructive ventilatory impairment. Altogether 590 asbestos-exposed workers, 95% of whom were smokers or ex-smokers, were studied with HRCT; 19 pathological signs were scored. Forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), FEV1/FVC ratio, forced expiratory flow at 50% of FVC (MEF50) and total lung capacity (TLC) were measured, and their relationship with HRCT signs was examined with bivariate correlations and multiple regression analysis. FVC and TLC were negatively correlated with fibrosis score, parenchymal bands, extent of pleural thickenings and positively with widened retrosternal space. FEV1/FVC ratio was negatively correlated with emphysema types and widened retrosternal space and positively with parenchymal bands and subpleural nodules. Thickened bronchial walls did not separate between restrictive and obstructive ventilatory function. HRCT signs showed distinctive patterns in restrictive and obstructive ventilatory impairment. These results can be used to help to analyse the lung function of patients simultaneously exposed to asbestos and smoking, when this relationship requires elucidation. In addition, the results may be helpful in explaining some radiological findings.

High-resolution computed tomography of the lungs: the borderlands of normality

High-resolution computed tomography (HRCT) is now widely used in the assessment of airways and diffuse lung disease. Considerable literature on pathologic correlation has increased the understanding of the signs of disease seen on HRCT. However, neither the significance of subtle individual signs nor the spectrum of HRCT appearances in healthy lungs is well documented. HRCT signs that cause diagnostic uncertainty and the spectrum of findings that exist between definite normality and definite abnormality are discussed.

Smoking-Related Diffuse Parenchymal Lung Disease: HRCT-Pathologic Correlation

Response by the lung to inhaled cigarette smoke varies widely between individuals and ranges from subclinical respiratory bronchiolitis to end-stage Langerhans' cell histiocytosis. The variety of interstitial lung diseases associated with cigarette smoking is wider than generally appreciated, and these often coexist. An understanding of the pathological basis of smoking-related lung disease helps to explain the sometimes complex patterns encountered on high-resolution computed tomography (HRCT). The recent refinement of the classification of the idiopathic interstitial pneumonias and the longitudinal study of cigarette smokers with HRCT has furthered understanding of what should be regarded as an overlapping group of entities. In this article the individual interstitial diseases ascribable to cigarette smoking are discussed in terms of their pathology and corresponding HRCT signs. Emphasis is placed on the frequent coexistence of various forms of smoking-related interstitial lung disease.

Imaging of the Small Airways

Small airways disease (SAD) is defined as a pathologic condition in which the small conducting airways are affected either primarily or as part of other pulmonary changes. Diagnosis is often difficult because the many histopathologic subtypes that have been described often lack obvious clinical or imaging correlates and because widespread involvement is needed before clinical symptoms and abnormalities on pulmonary function testing occur. High-resolution computed tomography (HRCT) can be helpful to detect, characterize, and quantify small airways involvement. These airways may become visible directly when inflammation of the bronchiolar wall and accompanying exudates develop. Obstruction of the small airways may be detected indirectly by HRCT when it causes regional underventilation resulting in reduced perfusion. This article discusses the direct and indirect HRCT signs of small airways involvement and, based on the fundamental differences between these signs, gives a short review of the HRCT features of the most important diseases that can affect the small airways.