Showing posts with label HRCT. Show all posts
Showing posts with label HRCT. Show all posts

Image Archives SVC obstruction- CT findings

By Dr Deepu

Sarcoidosis- CT findings

By Dr Deepu

conglomerated micronodules and centrilobular
 nodules in both lungs
Enlarged mediastinal  lymph nodes

 Bilateral hilar lymph nodes

Chest CT scans show conglomerated micronodules and centrilobular nodules in both lungs. We can see the enlarged mediastinal and bilateral hilar lymph nodes.
Sarcoidosis is a multi-system disease of unknown etiology, usually affecting the respiratory tract and other organs, and is characterized by the formation of nonnecrotizing epithelioid granulomas. The diagnosis depends on a combination of a typical clinicoradiological presentation, the finding of nonnecrotizing epithelioid granulomas in a tissue biopsy, and exclusion of other possible diseases, especially those of infectious etiology.

 Sarcoidosis results from an uncontrolled cell-mediated immune reaction. Interactions between chemokines and receptors that activate mitogen-activated protein kinase pathways play a major role in inflammation and T-cell responses. Tumor necrosis factor (TNF)-[alpha] is an important player in granuloma formation, and recent clinical trials have investigated the efficacy of TNF-[alpha] inhibitors in sarcoidosis.

HRCT view of cannonball secondaries

Ever wondered how cannon ball secondaries are seen on HRCT thorax??? Go through the video to find the cannon ball secondaries on HRCT thorax..
Unable to view the video watch it in youtube 
Want to Know more about cannon ball secondaries? Read this article

The HRCT findings of Bronchiectasis.

Pulmonary Medicine Blog By Dr Deepu

CT findings in bronchiectasis include the following:

·        Let me first describe the specific findings in the bronchiectasis
      Has parallel tram track lines, or
       It may have a signet-ring appearance
     Let me make it more clearer, it is composed of a dilated bronchus  cut in a horizontal section representing the golden ring; with an adjacent  pulmonary artery representing the stone of the Ring. Take a look at the signet ring to get the idea.

·         The diameter of the bronchus lumen is normally 1-1.5 times that of the adjacent vessel; a diameter greater than 1.5 times that of the adjacent vessel suggests bronchiectasis. Let us correlate it in the CT scan
Second Sign is lack of bronchial tapering, Normally as we move to the peripheral parts of the HRCT, the Bronchus should start tapering, as the diameter of the bronchus progressively decreases, whereas in the patients with bronchiectasis this tapering is not seen as the bronchial wall is destroyed and dilated , see the images below

 We can also see the abnormal bronchial contour due to the tractional forces applied by the fibrosed and diseased lungs
Visibility of peripheral airways within 1 cm of the pleura
Normally airways are not seen upto 1 cm from the pleura but with bronchiectasis we may be able to see the dilated peripheral airways

Its time to describe the non specific findings in the bronchiectasis
Peribronchial cuffing (thickened hazy bronchial wall).
Finger in glove opacities (mucus filled bronchi).
  •Multiple air fluid levels (fluid filled bronchi). 

Peripheral cuffing- here we have a thickened bronchial wall due to constant underlying inflammatory process in the bronchial wall
 Finger in glove opacities( Mucus filled bronchi)
mucus plugging of the bronchus causes bronchus to appear as a gloved hand 

let us see how it appears in the CT Scan

Does this look like a gloved finger???

Next sign is multiple air fluid levels
tThis occurs due to the dilated bronchus and the fluid collected in the dilated bronchus.

Along with these specific and non specific finding we will be able to see few ancillary findings associated with bronchiectasis
Mosaic perfusion.
Air trapping.
Tree in bud opacities.

Mosaic Perfusion
It occurs due to areas alternating areas of normal lung and trapped air in the lungs

Air Trapping, to see air trapping specifically ask for expiratory film, the air gets trapped in the blocked small airways causing dark areas,  whereas the air  is squeezed out from normal lung.

 Tree in Bud Appearance-
occurs due to active infection, study the image and find tree in bud, I have marked it in 2nd image
Image shows bronchiectasis and tree in Bud

tIf you liked the post please comment , comments activates the search engine, Thanks 
Suggested Reading

The Rings !!!The Trams!!!, Chest X Ray Findings in Bronchiectasis

My Next post will be on "SOLITARY PULMONARY NODULE"

The ‘Dark Bronchus’ Sign: For diagnosis of PCP

Pulmonary Medicine Blog By Dr Deepu

Today I will discuss the importance of the ‘dark bronchus’ sign in the diagnosis of uniform, diffuse ground glass opacification on high resolution computerized tomography (HRCT). This sign is useful to identify diffuse ground glass opacity on HRCT in cases of Pneumocystis carinii pneumonia who may present with a normal or equivocal chest radiograph in the early course of disease.

Chest radiograph is the initial investigation in HIV patients with chest symptoms. But even in patients with proven PCP, radiographic findings may be normal in up to 20-40%. Low incidence of PCP in patients with normal or equivocal findings on chest radiograph despite high clinical suspicion emphasizes the need for a noninvasive and widely available investigation in such cases.

Various modalities to investigate symptomatic HIV patients with normal, equivocal or nonspecific radiographic findings include carbon monoxide diffusion in lung (DLCO), gallium citrate lung scanning and HRCT. A DLCO of less than 80% of the predicted value has a sensitivity of up to 98% for PCP, but the specificity is less than 50% and the measurement is not always available. Although gallium scanning has a sensitivity of up to 100% for PCP in patients with abnormal radiographs, it has never been prospectively studied in patients with normal or equivocal radiographic findings. In addition, this investigation requires a 48- to 72-hour delay in imaging, is not readily available and has a high cost.

    On the other hand, HRCT is a widely available and noninvasive investigation for PCP. Patchy or diffuse ground glass opacity is the most frequent finding. Other findings include cystic changes (33%), centrilobular nodules (25%), lymphadenopathy (25%) and pleural effusion (17%). HRCT has been found to be especially important in the assessment of symptomatic patients with normal, equivocal or nonspecific radiographs. In such cases, it shows high sensitivity (100%), specificity (86%) and accuracy (90%) for PCP, using only the presence or absence of ground glass opacity as the criterion for positivity.
The Arrow Shows The Dark Bronchus Relative to The Surrounding Lungs

Patchy ground opacity or mosaic attenuation, which is observed in up to 92% of the patients, can be easily identified on HRCT. However, subtle ground glass opacification, especially when bilateral and diffuse, may be difficult to diagnose. This is because of bilateral uniform increase in lung attenuation with absence of normal lung parenchyma for comparison. In such cases, the ‘dark bronchus’ appearance is a useful sign to identify diffuse ground glass opacity. This finding refers to the presence of air-filled bronchi appearing ‘too black’ relative to the surrounding lung parenchyma, which is filled with inflammatory alveolar exudates. This subtle finding may help in identification of patients with ‘possible PCP’ despite a normal or equivocal chest radiograph. Subsequently direct test for PCP (i.e., broncho-alveolar lavage) may be initiated for definitive diagnosis and treatment.
Hence the importance of the ‘dark bronchus’ sign in the diagnosis of uniform, diffuse ground glass opacification on HRCT. This is especially useful in the presence of a normal chest radiograph and ‘near normal’ HRCT. HRCT offers an accurate and early diagnosis in patients with normal chest radiographs; it alters patient management and facilitates early therapy.

Also Read


This is the last post in the series of basics of HRCT. links to the previous posts are given at the end of this post.

Reticular pattern 

1.     Lymphangitic carcinomatosis: irregular septal thickening, usually focal or unilateral 50% adenopathy', known carcinoma.
2.     Cardiogenic pulmonary edema: incidental finding in HRCT, smooth septal thickening with basal predominance (Kerley B lines), ground-glass opacity with a gravitational and perihilar distribution, thickening of the peribronchovascular interstitium (peribronchial cuffing)
3.     Lymphangitic carcinomatosis.
4.     Lymphangitic carcinomatosis with hilar adenopathy.
5.     Alveolar proteinosis: ground glass attenuation with septal thickening (crazy paving).
6.     Cardiogenic pulmonary edema.

Nodular pattern

1.     Hypersensitivity pneumonitis: ill defined centrilobular nodules.
2.     Miliary TB: random nodules
3.     Sarcoidosis: nodules with perilymphatic distribution, along fissures, adenopathy.
4.     Hypersensitivity pneumonitis: centrilobular nodules, notice sparing of the area next to pleura and fissure.

Nodular pattern(2)

1.     Sarcoidosis: nodules with perilymphatic distribution, along fissures, adenopathy.
2.     TB: Tree-in-bud appearance in a patient with active TB.
3.     Langerhans cell histiocytosis: early nodular stage before the typical cysts appear.
4.     Respiratory bronchiolitis in infection.

High Attenuation pattern 

1.     Chronic eosinophilic pneumonia with peripheral areas of ground glass opacity.
2.     Sarcoid end-stage with massive fibrosis in upper lobes presenting as areas of consolidation. Notice lymphadenopathy.
3.     Chronic eosinophilic pneumonia with peripheral areas of consolidation.
4.     Broncho-alveolar cell carcinoma with both areas of ground glass opacity and consolidation

High Attenuation pattern (2) 

1.     Non specific interstitial pneumonitis (NSIP): ground glass with traction bronchiectasis, no honeycombing.
2.     Cryptogenic organizing pneumonia (COP).
3.     Sarcoidosis end-stage: consolidation as a result of massive fibrosis perihilar and in upper lobes.
4.     COP.

Low Attenuation pattern 

1.     Lymphangiomyomatosis (LAM): uniform cysts in woman of child-bearing age; no history of smoking; adenopathy and pleural effusion; sometimes pneumothorax.
2.     LCH: multiple round and bizarre shaped cysts; smoking history.
3.     Honeycombing
4.     Centrilobular emphysema: low attenuation areas without walls.

Low Attenuation pattern (2) 

1.     Centrilobular emphysema: low attenuation areas without walls. Notice the centrilobular artery in the center.
2.     Langerhans cell histiocytosis (LCH): multiple thick walled cysts; smoking history.
3.     Honeycombing.


Upper lung zone preference is seen in:
  • Inhaled particles: pneumoconiosis (silica or coal)
  • Smoking related diseases (centrilobular emphysema
  • Respiratory bronchiolitis (RB-ILD)
  • Langerhans cell histiocytosis
  • Hypersensitivity pneumonitis
  • Sarcoidosis
Lower zone preference is seen in:
  • UIP
  • Aspiration
  • Pulmonary edema
Central distribution is seen in sarcoidosis and cardiogenic pulmonary edema.

Peripheral distribution is mainly seen in cryptogenic organizing pneumonia (COP), chronic eosinophilic pneumonia and UIP.
Additional findings
Pleural effusion is seen in:

1.     Pulmonary edema
2.     Lymphangitic spread of carcinoma - often unilateral
3.     Tuberculosis
4.     Lymphangiomyomatosis (LAM)
5.     Asbestosis

Hilar and mediastinal lymphadenopathy

In sarcoidosis the common pattern is right paratracheal and bilateral hilar adenopathy ('1-2-3-sign').
In lung carcinoma and lymphangitic carcinomatosis adenopathy is usually unilateral.
'Eggshell calcification' in lymph nodes commonly occurs in patients with silicosis and coal-worker's pneumoconiosis and is sometimes seen in sarcoidosis, postirradiation Hodgkin disease, blastomycosis and scleroderma .

read other posts in this series

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The fourth pattern includes abnormalities that result in decreased lung attenuation or air-filled lesions.

These include:

  • Emphysema
  • Lung cysts (LAM, LIP, Langerhans cell histiocytosis)
  • Bronchiectasis
  • Honeycombing

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.
  • Centrilobular emphysema
    • Most common type
    • Irreversible destruction of alveolar walls in the centrilobular portion of the lobule
    • Upper lobe predominance and uneven distribution
    • Strongly associated with smoking.
  • Panlobular emphysema
    • Affects the whole secondary lobule
    • Lower lobe predominance
    • In alpha-1-antitrypsin deficiency, but also seen in smokers with advanced emphysema
  • Paraseptal emphysema
    • Adjacent to the pleura and interlobar fissures
    • Can be isolated phenomenon in young adults, or in older patients with centrilobular emphysema
    • In young adults often associated with spontaneous pneumothorax
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

Here is 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.

Cystic lung disease

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.

A case with multiple round and bizarre shaped cysts.
There was an upper lobe predominance.
The patient had a long history of smoking.
This combination of findings is typical for Langerhans cell histiocytosis.

Langerhans cell histiocytosis (LCH) is an idiopathic disease characterized in its early stages by granulomatous nodules containing Langerhans histiocytes and eosinophils. 
In its later stages, the granulomas are replaced by fibrosis and the formation of cysts.
It is an uncommon condition. 
The majority of patients are young or middle-aged adults presenting with nonspecific symptoms of cough and dyspnea. Up to 20% of patients present with pneumothorax and over 90% of patients are smokers.
Most cysts appear round, but can also have bizarre shapes (bilobed or clover-leaf shaped).
An upper lobe predominance in the size and number of cysts is common.

Above a case with multiple cysts that are evenly distributed througout the lung ( in contrast to LCH).
Notice the pneumothorax.
There was no history of smoking and this was a 40 year old female.
This combination of findings is typical for Lymphangiomyomatosis (LAM).

Lymphangiomyomatosis is a rare disease characterized by progressive proliferation of spindle cells, resembling smooth muscle.
Proliferation of these cells along the bronchioles leads to air trapping and the development of thin-walled lung cysts. 
Rupture of these cysts can result in pneumothorax.
Other features of LAM include adenopathy and pleural effusion.

Lymphangiomyomatosis occurs only in women, usually of child-bearing age, between 17 and 50 years. Identical clinical, radiologic, and pathologic pulmonary changes are seen in about 1% of patients with tuberous sclerosis.
Most patients die within 10 years of the onset of symptoms.


Bronchiectasis is defined as localized bronchial dilatation.
The diagnosis of bronchiectasis is usually based on a combination of the following findings:

  • bronchial dilatation (signet-ring sign)
  • bronchial wall thickening
  • lack of normal tapering with visibility of airways in the peripheral lung
  • mucus retention in the broncial lumen
  • associated atelectasis and sometimes air trapping
A signet-ring sign represents an axial cut of a dilated bronchus (ring) with its accompanying small artery (signet).
The most common cause of bronchiectasis is prior infection, usually viral, at an early age.
It also occurs in patients with chronic bronchitis, COPD and cystic fibrosis.
Bronchiectasis may mimic cystic lung disease and bullous emphysema.
Bronchiectasis caused by primary airway disease should be differentiated from tracion bronchiectasis as a result of fibrosis.
Here we see a chest film with a typical finger-in-glove shadow.
The HRCT shows focal bronchiectasis with extensive mucoid impaction, which is in the appropriate clinical setting (asthma and serum eosinophilia) typical for Allergic bronchopulmonary aspergillosis (ABPA).

Allergic bronchopulmonary aspergillosis is a lung disease occurring in patients with asthma or cystic fibrosis, triggered by a hypersensitivity reaction to the presence of Aspergillus fumigatus in the airways.
It characteristically presents with the findings of central bronchiectasis, mucoid impaction and atelectasis.


Honeycombing is defined by the presence of small cystic spaces with irregularly thickened walls composed of fibrous tissue.
Honeycomb cysts often predominate in the peripheral and subpleural lung regions regardless of their cause.
Subpleural honeycomb cysts typically occur in several contiguous layers.
This finding can allow honeycombing to be distinguished from paraseptal emphysema in which subpleural cysts usually occur in a single layer.

The case above shows subpleural honeycomb cysts in several contiguous layers.
There is also a lower lobe predominance and widespread traction bronchiectasis.
These findings are typical for Usual Interstitial Pneumonia (UIP).

UIP or 'end-stage lung' is a pathology diagnosis and usually shown at lungbiopsy, when honeycombing is visible.
Idiopathic pulmonary fibrosis (IPF), accounts for more than 60% of the cases of UIP.
UIP with lung fibrosis is also a common pattern of auto-immune disease and drug-related lung injury. 
A long list of drugs have been implicated, but this pattern is most commonly the result of cytotoxic chemotherapeutic agents such as bleomycin, busulfan, vincristine, methotrexate, adriamycin, and carmustine (BCNU)

Yet another case of UIP.

The lower zone predominance is demonstrated when you scroll through the images.
Notice the ground glass opacity in the left lower lobe as a result of fibrous tissue replacing the air in the alveoli.

Please the other posts on HRCT Thorax. To read click on the topics given below.