N2 - HRCT is a very powerful tool in the assessment of patients with diffuse lung disease. High-resolution CT of the lung Patterns of disease and differential diagnoses. Abstract HRCT is a very powerful tool in the assessment of patients with diffuse lung disease. Fingerprint Lung Diseases.
High-resolution CT of the lungs: Indications and diagnosis.
Differential Diagnosis. High-resolution CT of the lung: Patterns of disease and differential diagnoses. Radiologic Clinics of North America , 43 3 , Radiologic Clinics of North America. Gotway, Michael ; Reddy, Gautham P. Richard ; Elicker, Brett M. In: Radiologic Clinics of North America. AU - Webb, W.
On the left we see consolidation and ground-glass opacity in a patient with persistent chest abnormalities and weight loss without signs of infection. This suggested a chronic disease. There is no honeycombing or traction bronchiectasis, so we can rule out fibrosis. The weight loss is suggestive of a malignant disease. Histology revealed broncho-alveolar cell carcinoma.
Treatable or not treatable? In those cases there are usually associated HRCT findings of fibrosis, such as traction bronchiectasis and honeycombing. The images show two cases with GGO, one without fibrosis and potentially treatable and the other with traction bronchiectasis indicating fibrosis. Here two images af a patient with GGO as the dominant pattern. In addition there is traction bronchiectasis indicating the presence of fibrosis.
This case is one of the possible patterns of nonspecific interstitial pneumonia NSIP. NSIP is characterized histologically by a relatively uniform pattern of cellular interstitial inflammation associated with variable degrees of fibrosis.
High Resolution Computed Tomography and Chronic Obstructive Pulmonary Disease
As in UIP usual interstitial pneumonia it mainly involves the dependent regions of the lower lobes, but NSIP lacks the extensive fibrosis with honeycombing. NSIP may be idiopathic or associated with collagen vascular diseases or exposure to drugs or chemicals. NSIP has a relative good prognosis and the majority of patients respond to treatment with corticosteroids. This outcome is quite different from that seen in UIP, which has a poor prognosis. The term mosaic attenuation is used to describe density differences between affected and non-affected lung areas.
There are patchy areas of black and white lung. The role of the radiologist is to determine which part is abnormal: the black or the white lung. When ground glass opacity presents as mosaic attenuation consider:.
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If the vesses are difficult to see in the 'black' lung as compared to the 'white' lung, than it is likely that the 'black' lung is abnormal. Then there are two possibilities: obstructive bronchiolitis or chronic pulmonary embolism. Sometimes these can be differentiated with an expiratory scan. If the vessels are the same in the 'black' lung and 'white' lung, then you are looking at a patient with infiltrative lung disease, like the one on the right with the pulmonary hemmorrhage.
On the left a patient with ground glass pattern in a mosaic distribution. Some lobules are involved and others are not. The differential diagnosis is hypersensitivity pneumonitis, bronchiolitis or thromboembolic disease. The history was typical for hypersensitivity pneumonitis. Hypersensitivity pneumonitis usually presents with centrilobular nodules of ground glass density acinar nodules. When they are confluent, HRCT shows diffuse ground glass. Hypersensitivity pneumonitis HP is an allergic lung disease caused by the inhalation of antigens contained in a variety of organic dusts.
Farmer's lung is the best-known HP syndrome and results from the inhalation of fungal organisms that grow in moist hay or exposure to birds as pets 1. HP usually presents in two forms either as ground glass in a mosaic distribution as in this case or as centrilobular nodules of ground glass density acinar nodules. The clue here is the enlargement of pulmonary arteries arrow in the areas of ground glass. The ground glass appearance is the result of hyperperfused lung adjacent to oligemic lung with reduced vessel caliber due to chronic thromboembolic disease.
On the left another patient with ground glass pattern in a mosaic distribution. Again the ground glass appearance is the result of hyperperfused lung with large vessels adjacent to oligemic lung with small vessels due to chronic thromboembolic disease. Emboli adherent to the wall and intravascular septa are typical for chronic thromboemboli in which partial recanalization took place.
enter Crazy Paving is a combination of ground glass opacity with superimposed septal thickening 5. It was first thought to be specific for alveolar proteinosis, but later was also seen in other diseases. Consolidation is synonymous with airspace disease. When you think of the causes of consolidation, think of ' what is replacing the air in the alveoli'? Is it pus, edema, blood or tumor cells Table on the left. Most patients who are evaluated with HRCT, will have chronic consolidation, which limits the differential diagnosis. On the left two cases with chronic consolidation. There are patchy non-segmental consolidations in a subpleural and peripheral distribution.
The differential diagnosis is the same as the list above. The final diagnosis was cryptogenic organizing pneumonia COP. In chronic eosinophilic pneumonia the HRCT findings will be the same, but there will be eosinophilia. In fibrosis there will be other signs of fibrosis like honeycombing or traction bronchiectasis.
Bronchoalveolar carcinoma can also look like this. Organizing pneumonia OP Organizing pneumonia represents an inflammatory process in which the healing process is characterized by organization and cicatrization of the exudate rather than by resolution and resorption.
It is also described as 'unresolved pneumonia'. If no cause can be identified it is called cryptogenic organizing pneumonia COP. Patients with COP typically present with a several-month history of nonproductive cough. Many cases are idiopathic, but OP may also be seen in patients with pulmonary infection, drug reactions, collagen vascular disease, Wegener's granulomatosis and after toxic-fume inhalation.
On the left a case of chronic eosinophilic pneumonia. It was a patient with low-grade fever, progressive shortness of breath and an abnormal chest radiograph. There was a marked eosinophilia in the peripheral blood. Like in COP we see patchy non-segmental consolidations in a subpleural distribution.
Chronic eosinophilic pneumonia is an idiopathic condition characterized by extensive filling of alveoli by an infiltrate consisting primarily of eosinophils. Chronic eosinophilic pneumonia is usually associated with an increased number of eosinophils in the peripheral blood and patients respond promptly to treatment with steroids. The fourth pattern includes abnormalities that result in decreased lung attenuation or air-filled lesions. These include:. Most diseases with a low attenuation pattern can be readily distinguished on the basis of HRCT findings.
Emphysema typically presents as areas of low attenuation without visible walls as a result of parenchymal destruction. Paraseptal emphysema Paraseptal emphysema is localized near fissures and pleura and is frequently associated with bullae formation area of emphysema larger than 1 cm in diameter.
Apical bullae may lead to spontaneous pneumothorax. Giant bullae occasionally cause severe compression of adjacent lung tissue.
Panlobular emphysema On the left a typical case of panlobular emphysema. There is uniform destruction of the underlying architecture of the secondary pulmonary lobules, leading to widespread areas of abnormally low attenuation. Pulmonary vessels in the affected lung appear fewer and smaller than normal.
Panlobular emphysema is diffuse and is most severe in the lower lobes. In severe panlobular emphysema, the characteristic appearance of extensive lung destruction and the associated paucity of vascular markings are easily distinguishable from normal lung parenchyma. On the other hand, mild and even moderately severe panlobular emphysema can be very subtle and difficult to detect on HRCT 1.
Lung cysts are defined as radiolucent areas with a wall thickness of less than 4mm. Cystic lung diseases as listed in the table on the left. Cavities are defined as radiolucent areas with a wall thickness of more than 4mm and are seen in infection TB, Staph, fungal, hydatid , septic emboli, squamous cell carcinoma and Wegener's disease. On the left a case with multiple round and bizarre shaped cysts.