Images are usually displayed using "lung windows," in which air appears black, aerated lung dark grey, and other structures white
This image of normal left lung shows central, branching pulmonary arteries and bronchi. The bronchovascular bundles are made up of these paired structures and their surrounding interstitium (connective tissue). In cross section, the bronchus is a thin-walled, white circle with central air (black), and the adjacent artery appears as a solid, white circle. More peripherally, numerous small "dots" and a few branching lines represent small pulmonary arteries and veins. Throughout, arteries branch at acute angles, and veins branch at 90° angles. The pleura of the major interlobar fissure is a thin, horizontal line traversing the lung. The peripheral pleural surface, which cannot be seen, is smooth.
This image shows complete opacification of most of the left upper lobe. Vessels are not visible in this area. When the bronchi remain aerated, they are seen as branching lucencies called air-bronchograms, which are present in this image. This image represents infectious pneumonia, which is limited by the major fissure, resulting in a sharp border. The advancing anteromedial margin shows ground-glass opacity
This image shows patchy ground-glass opacities throughout both lungs. Note that in the regions of ground-glass, one can see the vessels.
MEDIASTINUM DEFINITION BOUNDRIES DIVISIONS NORMAL LINES & STRIPES
TECHNIQUE HIGH KVP TECH [120 ]--above 120 coefficient of x ray absorption of bone & soft tissue approach each other at high kvp & so lungs are not obscured by bones.--better penetration of mediastnum--short exposure-less scatter radiation ,sharp detail outline of structure is obtained. WEDGE FILTER
Normal mediastinum on plain radiograph* Rt mediastinum above azygous vein is formed by right brachiocephalic vein &s v c.*In case of aortic or brachiocephalic artery ectasia or unfolding either these veins will be pushed laterally or mediastinal border is formed by aorta or bracheocephalic artery.*Right paratrcheal stripe-between tracheal air column & lung . < 5 mm .*azygous vein-outlined by air in lung at the lower end of paratracheal stipe.
* Oesophageal-pleural stripe -lung posterior to trachea contact rt wall of oesophagus.if oesophagus at this level contain air ,rt wall of oesophagus is seen as this stripe.*Azygo-oesophageal recess—on rt side below azygous arch the rt lower lobe make contact with rt wall of esophagus & azygous vein .and the interface is known as azygo esophageal stripe.---concave to rt side-normal----convex to rt side—abnormal.subcarinal mass, left atrial enlargement
Normal mediastinum Paraspinal lines –lymph nodes and intercostal veins occupy this space between spine lung, Normal paraspinal stripe—1 to 2 mm wide. Aortico pulmonary window—pleura covering the angle between mid portion of aortic arch & main pulm artery & left pulm artery is---- Aorticopulmonary mediastinal stripe. Aorticopulmonary window is sensitive place to look for lymph node enlargement.
The junctional lines Anteror junctional line –when small amount of fat anterior to ascending aorta,two lungs may be seperated by more than four layers of pleura. Never extend lower than where it envelopes rt outflow tract. Posterior junctional line—lungs are close together behind the oesophagus forms this line.line seperates to envelope the aortic arch. When the lines are seen ,excludes mass or space occupying process at junctional areas
Silhouette sign I If an intrathoracic opacity is situated in anatomic contact with a border of heart or aorta ,will obscure that border. A radioopacity causes obliteration of rt border of heart , is anterior in location ,Anterior mediastinum. If it overlaps but does not obliterates , it lies in posterior or middle mediastinum.
Hilum overlay sign Differentiates cardic enlargement from mediastinal mass In mediastinal mass if Hilar vessels are seen through the mass indicates that the mass does not arise from hilum For accuracy the film should be true frontal ,slight obliquity may project normal pulmonary artery medialy
Cervicothoracic signWell defined mass seen above the clavicle isalways situated in posterior compartment ,theanterior compartment mass being in contactwith soft tissue rather than aerated lung is illdefined
More than one compartment Since no tissue plane in diff compartments in some conditions multiple comp are involved Enlarged lymph nodes. Mediastinitis Hematomas Vascular entities Bronchogenic cancer Metastates lymphangiomas
Characterization of mass on C T Does it contain fat Does it contain fluid? Does it enhance following the administration of i v contrast
Cystic hygroma TECHNIQUE Transverse images of thin slices of lung (1 to 1.5 mm thick) are obtained at non- contiguous intervals, In routine CT, slices 3 to 10 mm thickcm apart, usually 1 to 2 are obtained throughout. contiguously, imaging 100% of the lung
NODULES Smallest diameter detected 1-2 mm Classification Appearance - well-defined (likely interstitial) ill-defined (likely air-space) Distribution - centrilobular perilymphatic, or random
CENTRILOBAR MICRONODULES Centrilobular nodules can be identified in close association to pulmonary artery branches Centrilobular nodules are often centered 5-10 mm from the pleural surface Centrilobular nodules are usually of similar size and spaced at regular distances from each other.
CENTRILOBAR MICRONODULES Endobronchial tuberculosis Any bronchopneumonia Endobronchial spread of timor Silicosis or Coal workers’ pneumoconiosis
PERILYMPHATIC NODULES Perilymphatic nodules are usually well-defined and occur in relation to the lymphatics. They often affect the pleural surfaces and the peribronchovascular, interlobular septa, and centrilobular interstitial components.
TREE-IN-BUD "Tree-in-bud" appearance represents dilated and fluid-filled (i.e. pus, mucus, or inflammatory exudate) centrilobular bronchioles. Abnormal "tree-in-bud" bronchioles appear more irregular , lack of tapering or knobby/bulbous appearance at the tip of their branches.
Ground-glass Opacity Ground-glass , increased hazy opacity within the lungs that is not associated with obscured underlying vessels . Minimal thickening of the septal or alveolar interstitium, thickening of alveolar walls, or the presense of cells or fluid filling the alveolar spaces.
MOSAIC ATTENUATION Decreased attenuation which results from regional differences in lung perfusion secondary to airway disease or pulmonary vascular disease. Distribution is often patch, hence the designation "mosaic." Pulmonary arteries will be reduced in size in the lucent lung fields thus allowing mosaic perfusion to be distinguished from ground-glass opacities.
MOSAIC ATTENUATION Bronchiolitis Obliterans Cystic fibrosis Chronic PE
AIR TRAPPING Abnormal retention of gas within the lung following expiration. On HRCT, the lung parencyhma remains lucent on expiration, while normal lung areas show increased attenuation. Inspiration scans can be completely normal in air trapping.
AIR TRAPPING Obliterative bronchiolitis Asthma Hypersensitivity pneumonitis Normal variant (seen in superior segement of left lobe, middle lobe or lingula)
HONEYCOMBING Honeycombing extensive lung fibrosis alveolar destruction cystic appearance on gross pathology. Honeycombing presence of thich-walled, air-filled cysts, usually between the size of 3mm to 1cm in diameter.
HONEYCOMBING Interstitial fibrosis (IPF, RA, scleroderma, drug reaction, asbestosis, end stage hypersensitivity pneumonitis) End stage sarcoidosis
APPROACH TO DIAGNOSISAn acute appearance suggests pulmonary edema or pneumonia
APPROACH TO DIAGNOSISReticulonodular lower lung predominant distribution with decreased lung volumes suggests: (APC)1. Asbestosis2. Aspiration (chronic)3. Pulmonary fibrosis (idiopathic)4. Collagen vascular disease
APPROACH TO DIAGNOSIS A middle or upper lung predominant distribution suggests:1. Mycobacterial or fungal disease2. Silicosis3. Sarcoidosis4. Langerhans Cell Histiocytosis
APPROACH TO DIAGNOSISAssociated lymphadenopathy suggests :1. Sarcoidosis2. Neoplasm (lymphangitic carcinomatosis, lymphoma, metastases)3. Infection (viral, mycobacterial, or fungal)4. Silicosis