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1、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 lung Superior margin is thoracic inlet Defined by plane of 1st ribs Inferior margin is diaphragm Tissue planes exte
2、nd superiorly into neck around great vessels, trachea and esophagus Connects to abdominal cavity via esophageal, caval and aortic hiatuses Connects to lungs along hilar vessels and bronchi,Mediastinum,Radiologic anatomy CXR CT Normal or not? Compartments and their pathologies: Anterior Middle Poster
3、ior,Radiologic Anatomy,Landmarks to look for on the chest radiograph: Trachea Paratracheal stripe Descending aortic contour Azygo-esophageal contour,Pneumomediastinum with cervical emphysema,Tracheal air column,Should be straight Slight bend to right due to aortic arch on its left.,Trachea deviates
4、to the left,Right Aortic Arch,Right paratracheal stripe,Extends from thoracic inlet to azygos vein Widens out at azygos vein No 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
5、 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? Inspiration If so, repeat the film before proceeding to CT. Then askIs it new? GET OLD FILMS before gett
6、ing 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 structures Aortic anomalies Tortuous vessels Azygos vein Lipomatosis Fat pads,Severe asthma on long term steroids,Mediastinal lipomatosis,Pericardial Fat
7、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 inserti
8、on,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 hernia Zenker diverticulum Epiphrenic diverticulum Achalasia Mediastinal abscess,Achalasia,Zenker diverticulum,Hiatal hernia,Mediasti
9、nal 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 compartment These are not anatomic boundaries, and masses commonly cross over into compartments where they don
10、t “belong”.,Posterior mediastinum,Paraspinal area Masses usually visible on lateral film overlying spine May obscure descending aorta contour,Posterior mediastinum,Neurogenic tumors Schwannoma Sympathetic nerve tumors e.g. ganglioneuroma Neurenteric cyst, lateral meningocele Lymph nodes (unusual as
11、only area involved) Extramedullary hematopoesis Vertebral 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: Lymphoma Thymic lesions Germ cell origin tum
12、ors Thyroid masses Also: 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 a
13、rea, azygo-esophageal recess, retrocardiac area May be difficult to see on lateral view,Middle Mediastinum,Lymph nodes Foregut cysts Vascular lesions e.g. aneurysm Bronchogenic carcinoma Hiatal hernia, other esophageal or GI lesions,Lymphoma,Cardiac evaluation,Remember: cardiothoracic ratio of about
14、 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 ins
15、ufficiency.,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 siz
16、e,LVH,LV enlargement,Dilated cardiomyopathy multichanber enlargement,Review Questions,A mass that widens the paratracheal stripe is probably in the,1.Anterior mediastinum 2.Middle mediastinum 3.Posterior mediastinum 4.Neck,Posterior mediastinal masses include all except:,1.Schwannoma 2.Extramedullar
17、y hematopoesis 3.Thymoma 4.Lymphoma,Non-pathological causes of mediastinal widening on a chest radiograph include:,1.Supine positioning 2.Exogenous steroid use 3.Expiratory film 4.Tortuous brachiocephalic vessels 5.All of the above,Additional reading,Kawashima A et al CT of posterior mediastinal mas
18、ses. 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,