[Audio] Imaging serves a key role in the diagnosis of patients suspected of having idiopathic pulmonary fibrosis (IPF). Accurate pattern classification at thin-section chest CT is a key step in multidisciplinary discussions, guiding the need for surgical lung biopsy and determining
available pharmacologic therapies. The recent approval of new treatments for fibrosing lung disease has made it more critical than ever
for radiologists to facilitate accurate and early diagnosis of IPF. This document was developed by the Radiology Working Group of the
Pulmonary Fibrosis Foundation with the goal of providing a practical guide for radiologists. In this review, the critical imaging patterns
of IPF, pitfalls in imaging classifications, confounding imaging findings with other fibrotic lung diseases, and reporting standards for
cases of lung fibrosis will be discussed.. 

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Practical Imaging Interpretation in Patients Suspected of Having Idiopathic Pulmonary Fibrosis

Recommendations from the Radiology Working Group of the Pulmonary Fibrosis Foundation

ILD. Interstitial lung disease (ILD) comprises numerous distinct diseases with overlapping lung injury patterns on CT scans. This article focuses on key imaging findings for evaluating idiopathic pulmonary fibrosis (IPF), a progressive chronic lung disease of unknown cause. PFT : Restrictive and reduced diffusion capacity. 

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Interstitial lung disease (ILD) comprises numerous distinct diseases with overlapping lung injury patterns on CT scans. This article focuses on key imaging findings for evaluating idiopathic pulmonary fibrosis (IPF), a progressive chronic lung disease of unknown cause. PFT : Restrictive and reduced diffusion capacity

[Audio] The Pulmonary Fibrosis Foundation has created a network of care centers to ensure excellent management of idiopathic pulmonary fibrosis (IPF) and other fibrotic lung conditions. To stay at the forefront of advancements in the field, the foundation has established working groups. These groups offer insights and perspectives on important topics related to the diagnosis and treatment of pulmonary fibrosis, relying on published data and expert opinions. Specifically, the foundation has formed a Radiology Working Group, which aims to provide a practical guide for the radiologic diagnosis of fibrotic lung disease, incorporating recent evidence-based recommendations.. 

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Chest radiograph. initial screening test wide availability and low radiation exposure. normal radiographs were observed in approximately 10%-15% of ILD patients, alone are insufficient for fully characterizing ILD and guiding diagnosis and management. False-positive interpretations can occur in obese or underinflated patients due to the perceived increase in interstitial markings. to assess patients with pulmonary fibrosis for alternative diagnoses like pneumonia or pneumothorax.. 

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initial screening test wide availability and low radiation exposure.  normal radiographs were observed in approximately  10%-15% of ILD  patients,  alone are insufficient for fully characterizing ILD and guiding diagnosis and management.  False-positive interpretations can occur in obese or underinflated patients due to the perceived increase in interstitial markings. to assess patients with pulmonary fibrosis for  alternative diagnoses like pneumonia or pneumothorax.

CT. Technical factors used for the thin-section CT scanning protocol are important and can help prevent diagnostic errors when properly set. Excessive edge enhancement can lead to image noise that interferes with interpretation. A moderate edge-enhancing reconstruction algorithm is preferred(Siemens B45f, GE Bone, Philips D or YB, and Toshiba Lung Std Section thickness affects partial volume averaging. A thickness of 1.5 mm or less is recommended to maintain definition of small structures Noncontiguous thin-section CT imaging is no longer necessary due to the availability of multidetector CT, which provides contiguous visualization of the entire lung and improves diagnostic yield.. 

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Technical factors used for the thin-section CT scanning protocol are important and can help prevent diagnostic errors when properly set. Excessive edge enhancement can lead to image noise that interferes with interpretation. A moderate edge-enhancing reconstruction algorithm is preferred(Siemens B45f, GE Bone, Philips D or YB, and Toshiba Lung Std  Section thickness affects partial volume averaging. A  thickness of 1.5 mm or less  is recommended to maintain definition of small structures Noncontiguous thin-section CT imaging is no longer necessary due to the availability of multidetector CT, which provides contiguous visualization of the entire lung and improves diagnostic yield.

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Review and repeat if necessary Respiratory motion: pulsation or star artifact, particularly in the lingula. thin streaks mimicking reticular abnormality or doubling artifacts mimicking bronchiectasis. Proper patient coaching on inspiratory and expiratory effort. 

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Review and repeat if necessary  Respiratory motion: pulsation or star artifact, particularly in the lingula. thin streaks mimicking reticular abnormality or doubling artifacts mimicking bronchiectasis. Proper patient coaching on inspiratory and expiratory effort

[Audio] Evaluate small airways disease. Air trapping at expiratory thin-section CT -correlate with obstructive deficits at pulmonary function testing-substantially change the differential diagnosis.. 

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Increased lung attenuation Decreased lung volume Anterior bowing of non cartilaginous portion of trachea  If no change ? Expiration. Anterior bowing of the tracheal wall is greater than  50%–70%,  then this could reflect underlying tracheomalacia or excessive dynamic airways collapse.

Prone imaging. Detect early or mild interstitial lung disease (ILD) Dependent lung atelectasis, commonly present in supine inspiratory scanning. Omitted if supine imaging does not show any potential subpleural abnormality or fibrosis is convincingly evident on supine imaging alone.. 

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Detect early or mild interstitial lung disease (ILD) Dependent lung atelectasis, commonly present in supine inspiratory scanning. Omitted if supine imaging does not show any potential subpleural abnormality or fibrosis is convincingly evident on supine imaging alone.

Thin-Section CT Search Pattern. Each of the following should be evaluated: (a) the airways (including the trachea ,main bronchi, and smaller bronchioles) (b) lung parenchyma(generally lobe by lobe) (c) pleura (d) mediastinum (e) upper abdomen (e) musculoskeletal system. 

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Each of the following should be evaluated:  (a) the airways (including the trachea ,main bronchi, and smaller bronchioles) (b) lung parenchyma(generally lobe by lobe)  (c) pleura (d) mediastinum (e) upper abdomen (e) musculoskeletal system

Lung parenchyma. Interstitium and secondary pulmonary nodule. Clinical diseases can present with diverse imaging and histologic patterns, and occasionally, multiple patterns can coexist within the same patient. It is essential to consider both the imaging/histologic pattern and the clinical context when diagnosing and categorizing interstitial lung diseases. UIP pattern + rheumatological condition: CTD-ILD instead of IPF. 

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Interstitium and secondary pulmonary nodule. Clinical diseases can present with diverse imaging and histologic patterns, and occasionally, multiple patterns can coexist within the same patient. It is essential to consider both the imaging/histologic pattern and the clinical context when diagnosing and categorizing interstitial lung diseases. UIP pattern + rheumatological condition: CTD-ILD instead of IPF

Thin-Section CT Finding Reticular opacities Common Clinical Disease Idiopathic pulmonary fibrosis Nonspecific interstitial pneumonia Asbestosis Drug-related fibrosis Fibrotic hypersensitivity pneumonitis Connective tissue disease, interstitial lung disease. 

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Thin-Section CT Finding
Reticular opacities
Common Clinical Disease
Idiopathic pulmonary fibrosis
Nonspecific interstitial pneumonia
Asbestosis
Drug-related fibrosis
Fibrotic hypersensitivity pneumonitis
Connective tissue disease, interstitial lung disease

Ground-glass opacities
Nonspecific interstitial pneumonia
Acute interstitial pneumonia
Respiratory bronchiolitis, interstitial lung disease
Desquamative interstitial pneumonia
Lymphoid interstitial pneumonia
Organizing pneumonia
Hypersensitivity pneumonitis

Reticular pattern. The reticular pattern, also known as reticulation, is characterized by a fine network or mesh of overlapping linear lines within the secondary pulmonary lobule. The presence of a reticular pattern indicates interstitial injury and is often associated with fibrotic interstitial lung disease (ILD). This pattern is commonly observed alongside other signs of fibrosis, such as architectural distortion and bronchiectasis.. 

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The reticular pattern, also known as reticulation, is characterized by a fine network or mesh of overlapping linear lines within the secondary pulmonary lobule. The presence of a reticular pattern indicates interstitial injury and is often associated with fibrotic interstitial lung disease (ILD). This pattern is commonly observed alongside other signs of fibrosis, such as architectural distortion and bronchiectasis.

Architectural Distortion. Any distortion of the normal lung parenchymal anatomy In the setting of ILD, this generally refers to an abnormal appearance of the secondary pulmonary lobule shape or size with evidence of volume loss. 

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Any distortion of the normal lung parenchymal anatomy  In the setting of ILD, this generally refers to an abnormal appearance of the secondary pulmonary lobule shape or size with evidence of volume loss

Traction Bronchiectasis and Bronchiolectasis. Traction bronchiectasis and bronchiolectasis both refer to irreversible dilatation of an airway related to surrounding or adjacent lung fibrosis. The dilated airway is often irregular and tortuous. Traction bronchiectasis differs from nontraction bronchiectasis, which is not associated with fibrosis and is usually associated with other signs of airways disease. 

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Traction Bronchiectasis and  Bronchiolectasis

Traction bronchiectasis and bronchiolectasis both refer to irreversible dilatation of an airway related to surrounding or adjacent lung fibrosis. The dilated airway is often irregular and tortuous.  Traction bronchiectasis differs from  nontraction  bronchiectasis, which is not associated with fibrosis and is usually associated with other signs of airways disease

Honeycomb Cysts. Subpleural clustered cystic air spaces( 3-5mm). Contiguous and must touch pleural surface. Despite honeycombing being seemingly identifiable at first glance, its accurate identification can pose challenges in clinical practice. However, in the categorization of usual interstitial pneumonia (UIP) patterns, the significance of honeycombing as a required feature most times of idiopathic pulmonary fibrosis (IPF) has been reconsidered within the appropriate clinical context. This revision helps address the reliability concerns associated with the consistent identification of honeycombing in routine clinical practice.. 

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Subpleural clustered cystic air spaces( 3-5mm).  Contiguous and must touch pleural surface. Despite honeycombing being seemingly identifiable at first glance, its accurate identification can pose challenges in clinical practice. However, in the categorization of usual interstitial pneumonia (UIP) patterns, the  significance of honeycombing as a required feature most times of idiopathic pulmonary fibrosis (IPF) has been reconsidered within the appropriate clinical context.  This revision helps address the reliability concerns associated with the consistent identification of honeycombing in routine clinical practice.

Honeycomb Cysts versus Paraseptal Emphysema. 5 mm or less in diameter Thick walls Usually multilayered a/w reticular abnormality and architectural deformity. 

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Honeycomb Cysts versus  Paraseptal  Emphysema

5 mm or less in diameter Thick walls Usually multilayered a/w reticular abnormality and architectural deformity

1cm > Thin wall Single layered Lacks both

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Honeycomb Cysts versus Traction Bronchiectasis and Bronchiolectasis. 

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Honeycomb Cysts versus Traction Bronchiectasis and Bronchiolectasis

contiguous thin-section CT sections and observing continuity and branching of bronchi and bronchioles rather than discrete honeycomb cysts. Coronal and sagittal images

Traction bronchiectasis is distinguished from bronchiectasis caused by chronic inflammation and intrinsic airways disease by its association with underlying fibrotic lung abnormalities and the absence of significant airway-related changes like wall thickening or mucoid impaction. 

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Traction bronchiectasis is distinguished from bronchiectasis caused by chronic inflammation and intrinsic airways disease by its association with underlying fibrotic lung abnormalities and the absence of significant airway-related changes like wall thickening or mucoid impaction

[Audio] Comparison of traction bronchiectasis with bronchiectasis from chronic airway inflammation. (a) Axial CT scan demonstrates
traction bronchiectasis in a patient with fibrotic nonspecific interstitial pneumonia. Note the substantial reticular abnormality and architectural
distortion adjacent to the irregular dilated airways. (b) Axial CT scan demonstrates cylindrical bronchiectasis in the right lower lobe of a patient with underlying immunodeficiency. In contrast to traction bronchiectasis, this postinflammatory bronchiectasis lacks adjacent fibrosis and"tethering" of the airways. There are also associated findings of bronchial wall thickening and mucoid impaction.. 

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Key Definitions Seen in Patients without IPF. The following features may suggest an alternative diagnosis Ground glass opacity Consolidation Micronodules Mosaic attenuation Air trapping Cysts:. 

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Key Definitions Seen in Patients without IPF

The following features may suggest an alternative diagnosis Ground glass opacity Consolidation Micronodules Mosaic attenuation  Air trapping  Cysts:

GGO. Homogeneous areas of increased lung attenuation in which the increased opacity does not obscure the underlying bronchial and vascular structures. Not a feature typical of UIP/IPF but can be seen in the setting of overlapping or superimposed disease.. 

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Homogeneous areas of increased lung attenuation in which the increased opacity does not obscure the underlying bronchial and vascular structures.  Not a feature typical of UIP/IPF but can be seen in the setting of overlapping or superimposed disease.

[Audio] Axial inspiratory CT scan demonstrates mosaic attenuation due to small airways disease in a case of constrictive bronchiolitis. (c) Axial expiratory CT imaging (same patient as b) demonstrates accentuation of the areas of hyperlucency from the adjacent lung, confirming small airways disease as the cause of mosaic attenuation. Air trapping in the setting of ILD is most commonly seen associated with HP, constrictive bronchiolitis, and sarcoidosis.. 

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[Audio] Nevertheless, there is a growing acknowledgment that the presentation of UIP may not be typical, and the diagnostic criteria have been broadened to acknowledge characteristics that allow for the identification of IPF in atypical scenarios.. 

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Imaging Findings of IPF and the UIP Pattern

Many cases of UIP have typical CT appearances, strongly supporting the diagnosis. However, there is increasing recognition that the appearance of UIP may be nontypical, and diagnostic guidelines have been expanded to recognize features that permit the diagnosis of IPF in less typical cases

[Audio] classic pattern and has a predictive value of greater than 90% for histologic UIP. 

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Diagnostic Category
Typical UIP
Fleischner Society Statement
ATS/ERS/JRS/ALAT Guidelines
Distribution
Subpleural and basal-
predominant abnor-
mality
Often heterogeneous,
can be diffuse
Features
Honeycomb cyst formation
Reticulation with traction bron-
chiectasis or bronchiolectasis
Absence of features to suggest an
alternative diagnosis
Distribution
Subpleural and basal
predominant
Often heterogeneous,
can be diffuse
Features
Honeycomb cyst formation
Reticulation with or without
peripheral traction bronchi-
ectasis or bronchiolectasis

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[Audio] This pattern was previously known as possible UIP pattern.
Probable UIP pattern is similar to the typical UIP pattern, except that honeycombing is not present. About 80% of patientswith this pattern have UIP. 

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Probable UIP
Subpleural and basal
predominant
Often heterogeneous
Reticulation with traction bron-
chiectasis or bronchiolectasis
Absence of honeycombing*
Absence of features to suggest an
alternative diagnosis
Subpleural and basal
predominant
Often heterogeneous
Reticulation with peripheral
traction bronchiectasis or
bronchiolectasis
May have mild GGO*

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[Audio] In this pattern, the CT features are not sufficient for a firm diagnosis of UIP. About 50% of cases with this pattern have UIP. 

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Indeterminate for
UIP
Variable or diffuse; not
predominantly sub-
pleural or basal*
Reticulation with some incon-
spicuous or minor findings
that suggest an alternative,
non-IPF diagnosis
Subpleural and basal
predominant*
Subtle reticulation
Possible mild GGO or architec-
tural distortion
Distribution/features that are
not indicative of a particular
fibrotic pattern

“Fibrosing interstitial pneumonia with CT features indeterminate for UIP. Differential diagnosis might include fibrotic HP, NSIP, or UIP”

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CT Features Most Consistent with a Non-IPF Diagnosis. 

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CT Features Most Consistent with a Non-IPF Diagnosis

Upper- or mid-lung-predominant disease distribution (suggests HP). Areas of subpleural sparing with a peribronchovascular distribution (suggests NSIP, may be better seen on prone imaging). Significant findings typically found with non-IPF diagnosis (predominant consolidation, extensive pure ground-glass opacity without acute exacerbation], extensive mosaic attenuation with extensive sharply defined lobular expiratory air trapping [suggests HP], diffuse nodules or cysts

Alternative diagnosis. NSIP Fibrotic Hypersensitivity Pneumonitis Sarcoidosis Idiopathic Pleuroparenchymal Fibroelastosis Acute Exacerbation of UIP Combined Pulmonary Fibrosis and Emphysema Interstitial Pneumonia with Autoimmune Features. 

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NSIP Fibrotic Hypersensitivity Pneumonitis Sarcoidosis Idiopathic  Pleuroparenchymal  Fibroelastosis Acute Exacerbation of UIP Combined Pulmonary Fibrosis and Emphysema Interstitial Pneumonia with Autoimmune Features

NSIP. Overlapping but visually distinct features: Predominant abnormalities in NSIP: GGO with reticulation Honeycombing can be seen with NSIP but is usually mild and should not be the predominant finding. Lower lung predominance with subpleural sparing Patchier and peribronchovascular distribution of traction bronchiectasis. Gradual progression of fibrosis. Importance of prior imaging: Having access to prior imaging is crucial for properly categorizing patients with NSIP, as the progression of fibrosis can lead to misdiagnosis. 

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Overlapping but visually distinct features: Predominant abnormalities in NSIP: GGO with reticulation Honeycombing can be seen with NSIP but is usually mild and should not be the predominant finding. Lower lung predominance with subpleural sparing Patchier and peribronchovascular distribution of traction bronchiectasis. Gradual progression of fibrosis. Importance of prior imaging: Having access to prior imaging is crucial for properly categorizing patients with NSIP, as the progression of fibrosis can lead to misdiagnosis

[Audio] Nonspecific interstitial pneumonia. (a) Axial CT scan demonstrates fibrotic nonspecific interstitial pneumonia early in the disease course with lower lung fibrosis and ground-glass opacity with some subpleural sparing. (b) Axial CT scan 10 years later demonstrate substantial progression of the pulmonary fibrosis, which now demonstrates increased reticular abnormality, less ground-glass abnormality, and
more traction bronchiectasis. Understanding the evolution of the disease by reviewing the prior imaging is critical in these cases.. 

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Fibrotic Hypersensitivity Pneumonitis. Similarity to Usual Interstitial Pneumonia (UIP): Fibrotic HP can mimic UIP on thin-section CT scans in approximately 50% of cases. Lower Lung Predominance: Fibrotic HP can involve the lower lungs , contrary to the classical notion that it primarily affects the upper lungs. Differentiating HP from UIP: The presence of air trapping (especially lobular air trapping) and centrilobular ground-glass nodules on CT scans should raise suspicion of fibrotic HP rather than UIP.. 

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Similarity to Usual Interstitial Pneumonia (UIP): Fibrotic HP can mimic UIP on thin-section CT scans in  approximately 50% of cases. Lower Lung Predominance: Fibrotic HP can  involve the lower lungs , contrary to the classical notion that it primarily affects the upper lungs.  Differentiating HP from UIP: The presence of  air trapping (especially lobular air trapping) and centrilobular ground-glass nodules  on CT scans should raise suspicion of fibrotic HP rather than UIP.

[Audio] CT pattern most consistent with a nonidiopathic pulmonary
fibrosis diagnosis. Coronal CT scan demonstrates pulmonary fibrosis but
with substantial upper lung reticular opacities and architectural distortion in
addition to ground-glass abnormality and mosaic attenuation. This combination points to chronic hypersensitivity pneumonitis as the likely diagnosis
rather than idiopathic pulmonary fibrosis. 

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Sarcoidosis. All stages of sarcoidosis typically show a greater involvement of the upper lungs. Fibrosis associated with sarcoidosis tends to have a distribution that is more central or around the bronchovascular structures It radiates outward from the superiorly retracted hila Small airways disease, characterized by air trapping commonly seen with sarcoidosis and not just HP. 

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All stages of sarcoidosis typically show a greater involvement of the upper lungs. Fibrosis associated with sarcoidosis tends to have a distribution that is more central or around the bronchovascular structures It radiates outward from the superiorly retracted hila Small airways disease, characterized by air trapping commonly seen with sarcoidosis and not just HP

[Audio] Advanced fibrotic sarcoidosis. (a–c) Axial inspiratory CT and (d) coronal inspiratory CT images demonstrate mid to upper
lung–predominant pulmonary fibrosis with marked architectural distortion, associated lung nodularity, and some mosaic attenuation. Note also
the calcified mediastinal lymph nodes. This case would be categorized as most consistent with a nonidiopathic pulmonary fibrosis diagnosis
based on these features.. 

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Idiopathic Pleuroparenchymal Fibroelastosis. rare condition characterized by fibrosis and elastosis predominantly affecting the upper lungs. upper lung-predominant fibrosis and significant apical pleural thickening. While IPPFE is generally characterized by a distribution that points away from IPF, it can also be seen in conjunction with a concomitant usual interstitial pneumonia (UIP) pattern. This means that in some cases, the features of IPPFE and UIP may coexist.. 

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Idiopathic  Pleuroparenchymal  Fibroelastosis

rare condition characterized by fibrosis and elastosis predominantly affecting the upper lungs. upper lung-predominant fibrosis and significant apical pleural thickening. While IPPFE is generally characterized by a distribution that points away from IPF, it can also be seen in conjunction with a concomitant usual interstitial pneumonia (UIP) pattern. This means that in some cases, the features of IPPFE and UIP may coexist.

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Combined Pulmonary Fibrosis and Emphysema. upper lobe–predominant emphysema and lower lobe–predominant pulmonary fibrosis. different clinical, physiologic, and radiologic outcome when compared with patients with either pulmonary fibrosis or emphysema alone,. 

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Combined Pulmonary Fibrosis and Emphysema

upper lobe–predominant emphysema and lower lobe–predominant pulmonary fibrosis. different clinical, physiologic, and radiologic outcome when compared with patients with either pulmonary fibrosis or emphysema alone,

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Interstitial Pneumonia with Autoimmune Features. can be associated with ILD. In some cases, ILD may present as the initial or sole manifestation of a CTD, without fulfilling the diagnostic criteria for a specific autoimmune disease = the term "interstitial pneumonia with autoimmune features“= ERS (European Respiratory Society) and ATS (American Thoracic Society) task force. 

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Interstitial Pneumonia with Autoimmune Features

can be associated with ILD. In some cases, ILD may present as the  initial or sole manifestation of a CTD, without fulfilling the diagnostic criteria for a specific autoimmune disease = the term "interstitial pneumonia with autoimmune features“= ERS (European Respiratory Society) and ATS (American Thoracic Society) task force

Nonspecific interstitial pneumonia (NSIP): NSIP is characterized by a uniform appearance of ground-glass opacities or reticular patterns. Organizing pneumonia, also known as bronchiolitis obliterans organizing pneumonia (BOOP), presents as patchy areas of consolidation and ground-glass opacities. Lymphoid interstitial pneumonia: Lymphoid interstitial pneumonia (LIP) manifests as diffuse infiltrates and nodules The diagnosis requires integration of clinical, serologic, and morphologic findings .. 

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Nonspecific interstitial pneumonia (NSIP): NSIP is characterized by a uniform appearance of ground-glass opacities or reticular patterns.  Organizing pneumonia, also known as bronchiolitis obliterans organizing pneumonia (BOOP), presents as patchy areas of consolidation and ground-glass opacities.  Lymphoid interstitial pneumonia: Lymphoid interstitial pneumonia (LIP) manifests as diffuse infiltrates and nodules The diagnosis requires integration of clinical, serologic, and morphologic findings .

Acute Exacerbation of UIP. short prodrome of 1 to 2 months with progressive dyspnea or cough. diffuse alveolar damage and/or organizing pneumonia superimposed on UIP. 

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short prodrome of 1 to 2 months with progressive dyspnea or cough. diffuse alveolar damage and/or organizing pneumonia superimposed on UIP

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Final Diagnosis of IPF for a Given Thin-Section CT Pattern. 

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Final Diagnosis of IPF for a Given Thin-Section CT Pattern

CT pattern of typical UIP or probable UIP.—If clinical scenario is consistent with IPF,  biopsy is unnecessary. If clinical scenario is not typical for IPF (eg, patient aged < 60, relevant inhalational exposures),  biopsy is necessary CT pattern indeterminate for UIP or CT features most consistent with an alternative diagnosis.— Biopsy should be considered regardless of clinical scenario

[Audio] When contemplating the need for a biopsy, it is essential to bear in mind that open lung biopsy carries potential risks for the patient. While some patients may require a biopsy to establish a definitive diagnosis with certainty, it may not be suitable due to their individual risk factors. Furthermore, a biopsy may not provide significant benefits unless there are specific treatment alterations that would be influenced by confirming the diagnosis.. 

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A working diagnosis of IPF can be established if  (a) there is a progressive fibrosing interstitial pneumonia. (b) there is no viable alternative diagnosis.  Any such working diagnosis of IPF should be reviewed regularly.

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Imaging serves a key role in the diagnosis of patients suspected of having idiopathic pulmonary fibrosis (IPF)

Accurate pattern classification at thin-section chest CT is a key step in multidisciplinary discussions, guiding the need for surgical lung biopsy and determining

The recent approval of new treatments for fibrosing lung disease has made it more critical than ever

for radiologists to facilitate accurate and early diagnosis of IPF

This document was developed by the Radiology Working Group of the

Pulmonary Fibrosis Foundation with the goal of providing a practical guide for radiologists

In this review, the critical imaging patterns

of IPF, pitfalls in imaging classifications, confounding imaging findings with other fibrotic lung diseases, and reporting standards for

cases of lung fibrosis will be discussed.

avatar

The Pulmonary Fibrosis Foundation has created a network of care centers to ensure excellent management of idiopathic pulmonary fibrosis (IPF) and other fibrotic lung conditions

To stay at the forefront of advancements in the field, the foundation has established working groups

These groups offer insights and perspectives on important topics related to the diagnosis and treatment of pulmonary fibrosis, relying on published data and expert opinions

Specifically, the foundation has formed a Radiology Working Group, which aims to provide a practical guide for the radiologic diagnosis of fibrotic lung disease, incorporating recent evidence-based recommendations.

Air trapping at expiratory thin-section CT -correlate with obstructive deficits at pulmonary function testing-substantially change the differential diagnosis.

Comparison of traction bronchiectasis with bronchiectasis from chronic airway inflammation

traction bronchiectasis in a patient with fibrotic nonspecific interstitial pneumonia

Note the substantial reticular abnormality and architectural

distortion adjacent to the irregular dilated airways

(b) Axial CT scan demonstrates cylindrical bronchiectasis in the right lower lobe of a patient with underlying immunodeficiency

In contrast to traction bronchiectasis, this postinflammatory bronchiectasis lacks adjacent fibrosis and"tethering" of the airways

There are also associated findings of bronchial wall thickening and mucoid impaction.

Axial inspiratory CT scan demonstrates mosaic attenuation due to small airways disease in a case of constrictive bronchiolitis

(c) Axial expiratory CT imaging (same patient as b) demonstrates accentuation of the areas of hyperlucency from the adjacent lung, confirming small airways disease as the cause of mosaic attenuation.

Air trapping in the setting of ILD is most commonly seen associated with HP, constrictive bronchiolitis, and sarcoidosis.

Nevertheless, there is a growing acknowledgment that the presentation of UIP may not be typical, and the diagnostic criteria have been broadened to acknowledge characteristics that allow for the identification of IPF in atypical scenarios.

classic pattern and has a predictive value of greater than 90% for histologic UIP

This pattern was previously known as possible UIP pattern.

Probable UIP pattern is similar to the typical UIP pattern, except that honeycombing is not present

About 80% of patientswith this pattern have UIP

In this pattern, the CT features are not sufficient for a firm diagnosis of UIP

About 50% of cases with this pattern have UIP

(a) Axial CT scan demonstrates fibrotic nonspecific interstitial pneumonia early in the disease course with lower lung fibrosis and ground-glass opacity with some subpleural sparing

(b) Axial CT scan 10 years later demonstrate substantial progression of the pulmonary fibrosis, which now demonstrates increased reticular abnormality, less ground-glass abnormality, and

Understanding the evolution of the disease by reviewing the prior imaging is critical in these cases.

CT pattern most consistent with a nonidiopathic pulmonary

Coronal CT scan demonstrates pulmonary fibrosis but

with substantial upper lung reticular opacities and architectural distortion in

addition to ground-glass abnormality and mosaic attenuation

This combination points to chronic hypersensitivity pneumonitis as the likely diagnosis

rather than idiopathic pulmonary fibrosis

(a–c) Axial inspiratory CT and (d) coronal inspiratory CT images demonstrate mid to upper

lung–predominant pulmonary fibrosis with marked architectural distortion, associated lung nodularity, and some mosaic attenuation

This case would be categorized as most consistent with a nonidiopathic pulmonary fibrosis diagnosis

When contemplating the need for a biopsy, it is essential to bear in mind that open lung biopsy carries potential risks for the patient

While some patients may require a biopsy to establish a definitive diagnosis with certainty, it may not be suitable due to their individual risk factors

Furthermore, a biopsy may not provide significant benefits unless there are specific treatment alterations that would be influenced by confirming the diagnosis.