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mediastinal imaging
RPM II
46
Medical
Graduate
05/25/2010

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Term
what is the mediastinum?
Definition
the mass of tissues and organs separating the 2 lungs, between the sternum in front and vertebral column in the back and from the thoracic inlet above and diaphragm below
Term
when is a film technically adequate?
Definition
if the pt has a good inspiratory effort, if it is a PA view, the pt is erect and positioned symmetrically - no rotation, there is no motion on the film and there is adequate beam penetration
Term
the appearance of what ensures a good portion of the lung is visible in an x-ray (the pt has a good inspiratory effort)?
Definition
visibility of 9-11 rib/rib interspaces means the pt was inspiring when the film was taken
Term
what are identifiable structures on a CXR?
Definition
lung fields, mediastinum/hilum, trachea, cardiac silhouette, costophrenic and cardiophrenic angles, diaphragm, ossesous structures, and soft tissues
Term
what should be considered with mediastinal widening?
Definition
vascular abnormality, though if bilateral - lymphadenopathy
Term
what is the 1/3 - 2/3s rule?
Definition
1/3 of the heart should be on the R side of the mediastinum and 2/3 should be on the L side
Term
what are the costo- and cardio- phrenic angles?
Definition
the cardiophrenic angle is where the heart meets the diaphragm on both sides, and the costophrenic angle is where the lateral border of the lung meets the diaphragm
Term
how much of a difference should there be between the heights of the L and R diaphragms?
Definition
1-1.5 cm (the R side may be a little higher due to the liver)
Term
why is it important for the retro-sternal area to be clear?
Definition
to ensure that there is air in the lung tissue
Term
which is more anterior, the trachea or esophagus?
Definition
trachea
Term
how can you tell the difference between the R and L hemi diaphragms on a lateral view?
Definition
the diaphragm closest to the lateral view you are looking at will have a clearer anterior margin
Term
what is one benefit of the oblique view?
Definition
it helps get the mediastinum off the vertebral bodies
Term
how will the lungs of a pt w/COPD or emphysema appear?
Definition
elongated, with the mediastinum smushed in and the diaphragms flattened
Term
what should be visible on the R mediastinal border in an AP/PA CXR?
Definition
the SVC and R atrium
Term
what should be visible on the L mediastinal border in an AP/PA CXR?
Definition
the aortic arch, the L atrial appendage, and the L ventricle
Term
what composes the mediastinal contents?
Definition
the heart, great vessels, esophagus, trachea, R/L mainstem bronchi, and lymph nodes
Term
what generally composes the R and L borders of the heart as seen on CXR/thoracic CT?
Definition
the R border of the heart is generally composed of the R atrium and the L border of the heart is generally composed of the L ventricle
Term
where is the L atrium usually on CT scans?
Definition
in the back of the heart, nearest to the vertebral column
Term
what does a straight line where the diaphragm should be make you think of?
Definition
fluid, such as a hemothorax
Term
if there is a high level of radio-lucency where a lung should be and no indication of vascular markings or lobular markings, combined with an abnormal mediastinal "bump", what might you consider?
Definition
pneumothorax
Term
what is a "sail" sign?
Definition
the appearance of the triangular thymus on an infant's CXR
Term
what are causes of permanent mediastinal shift?
Definition
pneumononectomy (structures will move in toward where lung was), post radiation, scarring, and unilateral bulbous emphysema
Term
what are causes of temporary mediastinal shift?
Definition
atelectasis, tension pneumothorax, and foreign body
Term
what is apical capping?
Definition
significant opacification of a lung apex, often secondary to radiation therapy
Term
what are causes of tracheal deviation?
Definition
scarring, atelectasis, aortic knob prominences, mass affect, and pleural effusion
Term
what are causes of cardiomegaly?
Definition
CHF, cardiomyopathy, pericardial effusion, and technical problems with the film (poor inspiration, AP film, or pt is supine)
Term
what are causes of pneumomediastinum?
Definition
tracheal rupture, esophageal rupture/tick, gas producing organisms (rare), erosion from an adjacent tumor, trauma, iatrogenic, diabetic ketoacidosis, and asthma
Term
how can a lateral view help determine the cause of pneumomediastinum?
Definition
it can tell you if the air is in front of or behind what you are looking at in the PA view
Term
what can the mediastinum be sectioned into?
Definition
anterior, middle and posterior mediastinum
Term
what are the borders of the anterior mediastinum? contents?
Definition
borders: the sternum anteriorly and the heart+great vessels posteriorly. contents: internal mammary vessels, lymph nodes, thymus tissue, thyroid tissue and germ cells
Term
what are the four T's for anterior mediastinal masses?
Definition
thyroid, thymoma, teratoma, terrible lymphoma
Term
what characterizes a substernal goiter (thyroid of the terrible T's)?
Definition
substernal goiters are located at thoracic inlets, cause tracheal deviation, are often calcified, and most pts are asymptomatic (though they may present w/dysphagia or dyspnea). they are often IDed incidentally on CXR and if a nuclear medicine thyroid scan is indicated, consider a non-contrast CT (nuclear medicine will interfere with iodine uptake)
Term
what characterizes teratomas?
Definition
they are malignant germ cell tumors that occur almost always in men, usually <40. they contain endo, ecto, and mesoderm and often fat, Ca++ and teeth. if there is also a choriocarcinoma, the increase in HCG can lead to gynecomastia
Term
what characterizes the "terrible" lymphoma?
Definition
hodgkins (90% cure rate w/radiation, spreads to contiguous nodal groups, and 75% occur in mediastinal nodes) and non-hodgkins (20% occur in mediastinal nodes, nodal groups are skipped, and there is a poorer prognosis)
Term
what characterizes a thymomoa?
Definition
these are mostly found at the junction of the heart and the great vessels, 70% are benign, 25% are calcified, there is a 15% correlation w/myasthenia gravis, and they are seen mainly in pts 40-50 yrs old
Term
what are the normal contents of the middle mediastinum?
Definition
the heart, pericardium, aorta, pulmonary arteries/veins, trachea, mainstem bronchi, lymph nodes, and nerves (vagus, recurrent laryngeal)
Term
what are common causes of middle mediastinal masses?
Definition
pericardial fat pad, bronchogenic cyst/carcinoma, diaphragmatic hernia (hiatal), dilated vessels (aneurysm), and lymphadenopathy (*most common*)
Term
how would an aortic laceration, hematoma or aneurysm appear on a CXR?
Definition
widened mediastinum, indistinct aortic arch, fullness in region of aortic knob extending to the L lung apex (apical capping), and tracheal deviation to the R (ET tube)
Term
what are typical causes of lymphadenopathy - the most common middle mediastinal mass?
Definition
bronchogenic carcinomas (unilateral/bilateral), lymphoma (bilateral), leukemia, mets, sarcoid (bilateral), infection (TB, histo, coccidio)
Term
how does metastatic cancer spreading through the lymph system appear in the lungs?
Definition
as a starburst shape
Term
what are possibilities causes of calcified lymph nodes?
Definition
granulomatous disease (TB, histo), pneumoconioses (silicosis, anthracosis), and treated malignancies (hodgkin's)
Term
what are the contents of the posterior mediastinum?
Definition
the esophagus, the descending aorta, azygous/hemiazygous, intercostal and paraspinal nerves, and the pleura
Term
what are common causes of posterior mediastinal masses?
Definition
neurogenic tumors, duplication cysts, lymphadenopathy, esophageal pathology, and hernia
Term
what are common causes of posterior mediastinal masses?
Definition
neurogenic tumors (most common), duplication cysts, lymphadenopathy, esophageal pathology (hiatal hernia), and hernia
Term
what are the common kinds of neurogenic masses (all found in the posterior mediastinum)?
Definition
peripheral nerves, neurofibromas, schwannomas, sympathetic ganglion, and gangliomas
Term
what are common paravertebral masses seen on a CXR?
Definition
abscess (S. aureus, salmonella), extramedullary hematopoesis (chronic anemia), TB (pott's disease), neurogenic tumors, and meningoceles
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