BullaDefinition•Thin-walled–less than 1 mm•Air-filled space•In the lung> 1 cm in size and up to 75% of lung•Walls may be formed by pleura, septa,or compressed lung tissue.•Results from destruction, dilatation andconfluence of airspaces distal to terminalbronchioles.
•Bullous disease may be primary or associatedwith emphysema or interstitial lung disease.• Primary bullous lung disease may be familialand has been associated with Marfans, EhlersDanlos, IV drug users, HIV infection, andvanishing lung syndrome.•Bullae may occasionally become very largeand compromise respiratory function. Thushas been referred as vanishing lung syndrome,and may be seen in young men.
Pneumatocele is a benign air containing cyst of lung, withthin wall < 1mm as bulla but with different mechanism Infection with staph aureus is the commonest cause ( lesscommon causes are, trauma, barotrauma) lead to necrosisand liquefaction followed by air leak and subpleuraldissection forming a thin walled cyst.
•Honeycombing is defined as multiple cysts < 1cm in diameter,withwell defined walls, in a background of fibrosis, tend to formclusters and is considered as end stage lung .•It is formed by extensive interstitial fibrosis of lung with residualcystic areas.
A cyst is a ringshadow > 1 cm indiameter and up to10 cm with wallthickness from 1-3mm.
Radiation PneumoniaPost Mediastinal RadiationAir space disease (air bronchogram)Over radiation port (vertical and paramediastinal)BilateralProgression to fibrosis
Round PneumoniaRound densityShorter doubling timeAir bronchogramThe most common causes for round pneumonia are:FungalTuberculosis
Consolidation / LingulaDensity in left lower lung fieldLoss of left heart silhouetteDiaphragmatic silhouette intactNo shift of mediastinumBlunting of costophrenic angleLateralLobar densityOblique fissure notsignificantly shiftedAir bronchogram
Consolidation Left Lower LobeDensity in left lower lung fieldLeft heart silhouette intactLoss of diaphragmatic silhouetteNo shift of mediastinumPneumatoceleOne diaphragm only visibleLobar densityOblique fissure not significantlyshifted
Left Upper Lobe ConsolidationDensity in the left upper lung fieldLoss of silhouette of left heart marginDensity in the projection of LUL in lateral viewAir bronchogram in PA viewNo significant loss of lung volume
Vague density right lower lung fieldIndistinct right cardiac silhouetteIntact diaphragmatic silhouetteDensity corresponding to RMLNo loss of lung volumeRML pneumonia
Consolidation Right Upper Lobe /Air BronchogramDensity in right upper lung fieldLobar densityLoss of ascending aorta silhouetteNo shift of mediastinumTransverse fissure not significantly shiftedAir bronchogram
Achalasia ofesophagus• Inhomogeneouscardiac density:Right half moredense than left• Density crossingmidline (right blackarrow)• Right sided inlet tooutlet shadow• Right para spinal line(left black arrow)• Barium swallowbelow: Dilatedesophagus
Aortic Aneurysms• Location– Ascending / Anterior mediastinum– Arch / Middle mediastinum– Descending / Posterior mediastinum• Characteristics– Mediastinal "mass" density– Extrapleural– Calcification of wall• Dissecting– Inward displacement of calcified intima– Wavy margin– Inlet to outlet shadow– Left pleural effusion
Dissecting AneurysmMediastinal wideningInlet to outlet shadowon left sideRetrocardiac: Intactsilhouette of left heartmarginPulmonary arteryoverlay sign: Densitybehind left lower lobeWavy margin
of PE Diagnostic Algorithm1. Patients with normal chest radiographic findingsare evaluated with a perfusion scan and, ifnecessary, an aerosol ventilation scan. Patientswith normal or very low probability scintigraphicfindings are presumed not to have pulmonaryemboli .2-Patients with a high-probability scan usuallyundergo anticoagulation therapy. All other patientsshould be evaluated with helical CT pulmonaryangiography, conventional pulmonaryangiography, or lower-extremity US, depending onthe clinical situation
of PE Diagnostic Algorithm3-Patients with abnormal chest radiographic findings, areunlikely to have definitive scintigraphic findings. Thesepatients undergo helical CT pulmonary angiography as wellas axial CT of the inferior vena cava and the iliac, femoral,and popliteal veins. If the findings at helical CT pulmonaryangiography are equivocal or technically inadequate (5%–10% of cases) or clinical suspicion remains high despitenegative findings, additional imaging is required.4-Patients who have symptoms of deep venous thrombosisbut not of pulmonary embolism initially undergo US, whichis a less expensive alternative. If the findings are negative,imaging is usually discontinued; if they are positive, thepatient is evaluated for pulmonary embolism at thediscretion of the referring physician.
Potential Sources of Mediastinal AirIntrathoracicTrachea and major bronchiEsophagusLungPleural spaceExtrathoracicHead and neckIntraperitoneum and retroperitoneum
Radiographic Signs of PneumomediastinumSubcutaneous emphysemaThymic sail signPneumoprecardiumRing around the artery signTubular artery signDouble bronchial wall signContinuous diaphragm signExtrapleural signAir in the pulmonary ligament
The CT features of benignmediastinal cyst are(a) a smooth, oval or tubular mass with a well-defined thin wall that usually enhances afterintravascular administration of contrastmaterial,(b) homogeneous attenuation, usually in therange of water attenuation (0–20 HU),(c) no enhancement of cyst contents, and(d) no infiltration of adjacent mediastinalstructures.
Cysts that contain serous fluid typically havelong T1 and T2 relaxation values, whichproduce low signal intensity on T1-weightedMR images and high signal intensity on T2-weighted images.
Because cysts containing nonserousfluid can have high attenuation at CT,they may be mistaken for solidlesions. MR imaging can be useful inshowing the cystic nature of thesemasses because these cysts continueto have characteristically high signalintensity when imaged with T2-weighted sequences regardless of thenature of the cyst contents
Radionuclide imaging can be helpful indetecting functioning thyroid tissue(iodine-123 or I-131) or parathyroidtissue (technetium-99m sestamibi) inthe mediastinal cystic mass . gallium-67 scintigraphy may show increasedradiotracer uptake in the cysticmalignancy owing to necrosis such aslymphoma or metastatic carcinoma.
Ultrasonography (US) can be useful inevaluating a mass adjacent to thepleural surface or cardiophrenic angle.At US, the benign cysts typicallyappear as anechoic thin-walledmasses with increased throughtransmission