医学pptmediastinummodadam.ppt
Imaging the Mediastinum,Adam Guttentag M.D.,All photos retain the copyrights of their original authors,2005 Adam Guttentag,MD,Mediastinum,Bounded laterally by parietal pleura of each lungSuperior margin is thoracic inletDefined by plane of 1st ribsInferior margin is diaphragmTissue planes extend superiorly into neck around great vessels,trachea and esophagusConnects to abdominal cavity via esophageal,caval and aortic hiatusesConnects to lungs along hilar vessels and bronchi,Mediastinum,Radiologic anatomyCXRCTNormal or not?Compartments and their pathologies:AnteriorMiddlePosterior,Radiologic Anatomy,Landmarks to look for on the chest radiograph:TracheaParatracheal stripeDescending aortic contourAzygo-esophageal contour,Pneumomediastinum with cervical emphysema,Tracheal air column,Should be straightSlight bend to right due to aortic arch on its left.,Trachea deviates to the left,Right Aortic Arch,Right paratracheal stripe,Extends from thoracic inlet to azygos veinWidens out at azygos veinNo more than 3-4 mm thick,Sarcoid,Old film,Aortic contour,Azygo-esophageal recess,Aortic contour and azygo-esophageal recess abnormal,Normal anatomy:CT/CXR correlation,Normal anatomy:CT/CXR correlation,Normal anatomy:CT/CXR correlation,Normal anatomy:CT/CXR correlation,Is the mediastinum wide?,First ask is it technical?Positioning:rotated:?AP?Lordotic?Supine?InspirationIf so,repeat the film before proceeding to CT.Then askIs it new?GET OLD FILMS before getting a CT unless time is critical.,30 year old man in motor vehicle accident,AP supine,AP upright,PA upright,Think about normal variants!,Vascular structuresAortic anomaliesTortuous vesselsAzygos veinLipomatosisFat pads,Severe asthma on long term steroids,Mediastinal lipomatosis,Pericardial Fat Pad,Tortuous brachiocephalic vessels,Azygos continuation of the IVC congenital variant,70 year old with dysphagia,Tracheal air column,Esophageal cancer,Abnormal right paratracheal stripe,Hodgkins disease,Abnormal right paratracheal stripe,Check the old film!,2 days earlier,Hematoma from line insertion,One year ago,Abnormal right paratracheal stripe and aortic arch obscured,Tumor obscuring the top of the aortic arch,Air fluid levels,Think bowel or abscess:Hiatal herniaZenker diverticulumEpiphrenic diverticulumAchalasia Mediastinal abscess,Achalasia,Zenker diverticulum,Hiatal hernia,Mediastinal abscess after CABG,Differential diagnosis of mediastinal masses,Traditionally,we divide the mediastinum into compartments.Likely diagnosis of mass depends on what is contained in each compartmentThese are not anatomic boundaries,and masses commonly cross over into compartments where they dont“belong”.,Posterior mediastinum,Paraspinal areaMasses usually visible on lateral film overlying spineMay obscure descending aorta contour,Posterior mediastinum,Neurogenic tumorsSchwannomaSympathetic nerve tumors e.g.ganglioneuromaNeurenteric cyst,lateral meningoceleLymph nodes(unusual as only area involved)Extramedullary hematopoesisVertebral tumors,spurs,Schwannoma,Extramedullary hematopoesis,Lateral meningocele in NF-1,Anterior mediastinum,Space anterior to great vessels and heart,behind the sternum,Anterior mediastinum,Most common:LymphomaThymic lesionsGerm cell origin tumorsThyroid massesAlso:Foregut cysts,nerve tumors,aortic aneurysm,etc.,Anterior mediastinal masses,Thymic hyperplasia,teratocarcinoma,teratoma,lymphoma,thymoma,hemorrhage,Middle mediastinum,Contains heart,great vessels,esophagus,trachea,lymph nodes,nerves.CXR abnormality in paratracheal area,azygo-esophageal recess,retrocardiac areaMay be difficult to see on lateral view,Middle Mediastinum,Lymph nodesForegut cystsVascular lesions e.g.aneurysmBronchogenic carcinomaHiatal hernia,other esophageal or GI lesions,Lymphoma,Cardiac evaluation,Remember:cardiothoracic ratio of about 0.5 applies only to good PA chest x-rays.Knowing which chambers form which cardiac contours can help identify what is enlarged.Look for accompanying signs:Pulmonary venous engorgement and isolated LA enlargement suggests mitral stenosis.Dilated aorta and LV enlargement suggests aortic valve insufficiency.,Normal heart contours,Left atrial enlargement-mitral stenosis,Mitral valve,Left atrial enlargement,“Double density”,Straightened left heart border,LA enlarged,LV normal,Enlarged ascending aorta in AS,Calcific Aortic Stenosis,Enlarged ascending aorta,normal arch,normal overall heart size,LVH,LV enlargement,Dilated cardiomyopathy multichanber enlargement,Review Questions,A mass that widens the paratracheal stripe is probably in the,1.Anterior mediastinum2.Middle mediastinum3.Posterior mediastinum4.Neck,Posterior mediastinal masses include all except:,1.Schwannoma2.Extramedullary hematopoesis3.Thymoma4.Lymphoma,Non-pathological causes of mediastinal widening on a chest radiograph include:,1.Supine positioning2.Exogenous steroid use3.Expiratory film4.Tortuous brachiocephalic vessels5.All of the above,Additional reading,Kawashima A et al CT of posterior mediastinal masses.Radiographics 1991;11:1045-1067.Laurent F et al Mediastinal masses:diagnostic approach.Eur Radiol.1998;8(7):1148-59.Sharma A et al Patterns of lymphadenopathy in thoracic malignancies.Radiographics.2004 24(2):419-34.Jeung M et al Imaging of Cystic Masses of the Mediastinum Radiographics 2002;22:79-93.,The End,Use the back button on the browser to exit the program,
