Figures
- FIGURE 1
a-d) Typical changes over time in different diffuse lung diseases. a) Subacute hypersensitivity pneumonitis: baseline (left) and 6-month follow-up (right) high-resolution computed tomography (HRCT). Ground glass opacity and centrilobular nodules demonstrate significant interval decrease after antigen removal with mild persistent abnormality remaining including reticulation. b) Desquamative interstitial pneumonia: baseline (left) and 3-year follow-up (right) HRCT. Subpleural ground glass opacity seen on the baseline HRCT has evolved into cystic lucencies in a patient who continued to smoke. The cystic lucencies may represent emphysema surrounded by fibrosis. c) Sarcoidosis: baseline (left) and 4-year follow-up (right) HRCT. Perilymphatic nodules on the initial HRCT evolve into fibrosis as evidenced by reticulation, architectural distortion, and mild bronchiectasis. d) Organising pneumonia: baseline (left) and 2-year follow-up (right) HRCT. Ground glass opacity, consolidation, and the reversed halo sign on the initial HRCT evolves to fibrosis after treatment with corticosteroids.
- FIGURE 2
Changes in high-resolution computed tomography (HRCT) pattern over time. a) Idiopathic pulmonary fibrosis (IPF), increased specificity over time. Initial HRCT in a patient with early IPF (left) shows mild subpleural reticulation without honeycombing. 3 years later (right) honeycombing has developed. While the initial study is nonspecific, the follow-up HRCT would be considered a “definite usual interstitial pneumonia” pattern and diagnostic of IPF in the appropriate clinical setting. b) Nonspecific interstitial pneumonia (NSIP), change in pattern over time. Baseline prone HRCT image (left) in a patient with rheumatoid arthritis demonstrates reticulation and traction bronchiectasis with subpleural sparing compatible with NSIP. 8 years later (right) there is diffuse honeycombing that would be compatible with a usual interstitial pneumonia pattern.
- FIGURE 3
Longitudinal imaging after initial diagnosis. a) Nonspecific interstitial pneumonia (NSIP), early changes not detected by pulmonary function tests. In a patient with scleroderma and normal pulmonary function tests, prone high-resolution computed tomography (HRCT) (left) demonstrates early ground glass opacity and reticulation. 1 year later, a repeat HRCT (right) shows worsening of the lung disease; however, this was not accompanied by a significant change in pulmonary function tests. b) NSIP, microscopic fibrosis. Baseline HRCT (left) in a patient with scleroderma shows subpleural ground glass opacity suggestive of cellular NSIP. A repeat HRCT (right) 1 year later after immunosupression shows no significant change. In this case, the ground glass opacity represented microscopic fibrosis that was irreversible.
- FIGURE 4
Evaluation of acute symptoms. a) Infection in the setting of idiopathic pulmonary fibrosis (IPF). Baseline high-resolution computed tomography (HRCT) (left) and follow-up HRCT after the development of acute symptoms (right) shows both worsening diffuse lung disease and a new cavitary lesion. Sputum cytology revealed atypical mycobacterial infection. b) Acute exacerbation of IPF. Baseline study (left) shows a usual interstitial pneumonia pattern of fibrosis with subpleural honeycombing and mild reticulation. 1 month later, the patient presented with acute respiratory distress and a new HRCT (right) shows both worsening fibrosis and diffuse ground glass opacity compatible with an acute exacerbation.
- FIGURE 5
Evaluation of complications. Lung cancer in the setting of idiopathic pulmonary fibrosis. Baseline high-resolution computed tomography (left) shows a usual interstitial pneumonia pattern of fibrosis. A follow-up scan performed 9 months later (centre) shows a new, subtle band of ground glass and consolidation in the left upper lobe. A short-term follow up was performed 3 months later (right), which showed slight enlargement of the abnormality, and this was subsequently proven to represent lung adenocarcinoma.
Tables
- TABLE 1
Expected course of common diffuse lung diseases, including a list of high-resolution computed tomography (HRCT) findings for each disease that are typically reversible versus irreversible
Disease or pattern Expected course HRCT findings Typically reversible Typically irreversible Idiopathic pulmonary fibrosis Progression is typical None
GGO may evolve into reticulationReticulation
Honeycombing
Traction bronchiectasis
Architectural distortionHypersensitivity pneumonitis Depends on antigen removal and the presence of fibrosis on HRCT Findings of acute or subacute hypersensitivity pneumonitis (GGO, consolidation and centrilobular nodules) Findings of chronic hypersensitivity pneumonitis (reticulation, honeycombing, traction bronchiectasis, emphysema) Respiratory bronchiolitis ILD Almost always improves with smoking cessation GGO
Centrilobular nodulesReticulation (rare as a significant finding)
GGO that remains after smoking cessation/treatment may represent microscopic fibrosisDesquamative interstitial pneumonia Majority of patients improve with smoking cessation and/or corticosteroids GGO (if the patient doesn't stop smoking this may evolve into fibrosis or cystic lucencies) Cystic lucencies
Reticulation
Honeycombing
GGO that remains after smoking cessation/treatment may represent microscopic fibrosisLangerhans cell histiocytosis Findings may improve or resolve with smoking cessation Nodules (if patient doesn't stop smoking these may cavitate and evolve into cysts)
Thick-walled cavitiesThin-walled cavities
CystsNSIP Evolution depends on subtype (cellular versus fibrotic) and is hard to predict on imaging Findings of cellular NSIP, namely GGO (however this finding is not specific for reversible disease in NSIP) Findings of fibrotic NSIP (reticulation and traction bronchiectasis) Sarcoidosis Progression from nodules to fibrosis is rare Nodules
Interlobular septal thickening
GGO and consolidation more commonly evolve to fibrosisReticulation
Honeycombing
Cystic airspacesOrganising pneumonia Highly responsive to steroids; relapse may occur Consolidation
GGOFindings may progress to fibrosis, commonly in an NSIP pattern ILD: interstitial lung disease; NSIP: nonspecific interstitial pneumonia; GGO: ground glass opacity.
- TABLE 2
The most common roles of longitudinal high-resolution computed tomography (HRCT) data in the evaluation of patients with diffuse lung disease (DLD)
HRCT role Notes Initial diagnosis Pattern may become more diagnostic over time
Resolved or improved findings suggest an inflammatory or infiltrative component (e.g. not IPF)Prognosis Worsening abnormalities or rapid progression suggest a worse prognosis Routine follow-up Particularly helpful when PFTs may be inaccurate: patient unable to cooperate with PFTs; multifactorial restrictive disease (e.g. both fibrosis and pleural disease); mixed interstitial and airways disease; or early disease (below threshold of PFTs)
Distinguish inflammation/infiltration from fibrosis on baseline HRCTDetection of disease progression Particularly helpful in patients with worsening symptoms and/or PFTs
HRCT may be used as endpoint in clinical drug trials
Quantitative analysis may provide a more objective analysis of findings and extent of lung involvedEvaluation of patients with acute lung symptoms Distinguish progression of DLD versus a superimposed process (e.g. infection)
Detection of acute exacerbationDetection of complications Detection of lung cancer, pulmonary hypertension and other abnormalities associated with DLD IPF: idiopathic pulmonary fibrosis; PFT: pulmonary function test.
Supplementary Material
T.S. Henry ERR-0008-2017_Henry
