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LECTURE 2 Respiratory system Radiological investigation in respiratory system : Dr.Amjaad 1.Plain chest radiography 2. Computed tomography 3.MRI 4.Radionuclide lung scanning . 5. US . 6.flouroscopy 7. pulmonary angiography 1. plain chest radiography though chest films are the comments x-ray examination , they are also one of the most difficult plain films to interpret Routine chest radiography comprises PA & lateral view , ideally , both should be examined in full inspiration because in expiration the lung bases appear hazy & the heart shadow increase in size Interpretation : .Center .inspiration .mediastimun . heart shadow .diaphragm .hilar shadow . lung field apices A. centre: medial end of the clavicle must be equidistance from the spinous process of dorsal vertebra on both sides otherwise it is rotated film B. inspiration : On good inspiratory film , the level of the Rt. Hemidiaphragm is near the anterior end of the 6th rib C: check the mediastinum : Normally , the trachea lies midway, or slightly to the right of the midpoint , between the medial ends of the clavicles .in young children the thymus may be normaly so large that it may reach the thoracic wall , it should not be mistaken for a disease D: Heart shadow : C/T ratio =greater cardiac diameter /internal thoracic diameter =50%in adult while in children reach to 60% One 3rd of the heart lie to the Rt.side & two third located in the Lt. side 1 D:check the diaphragm : The upper surface of the diaphragm should be clearly visible from one costophrenic angle to the other , except where the heart is in contact with the diaphragm . , the Rt. Hemidiaphragm being up to 2.5cm higher than the Lt.(affect of heart ) E:check the hilar shadows. The size , sit & density should be examine carefully The Lt. hilum is usually higher in position than the Rt. Up to 2.5cm above this consider abnormal D: Check the lungs : Lung field for descriptive purpose (not anatomical )divided into upper , middle & lower zones Upper zone :1st & 2nd ribs. Middle zone :2nd & 3rd ribs Lower zone :5th & 6th ribs The only structures that can be identified within normal lungs are the blood vessels, interlobar fissures & the wall of certain larger bronchi . Usually only the horizontal fissure (minor fissures ) is visible in the frontal projection running from the Rt. Hilum to the 6th rib in the axilla , there is no horizontal fissure in the Lt. side The oblique fissures (major fissures ) are only visible on the lateral view E. costophrenic angle : Should be acute , its obliteration is early sign of pleural effusion F:Check the bone(rib clavicle & spine ) & soft tissue : In female , check that both beast shadow are present , following mastectomy breast shadow can not be defined causing reduction in the bulk of soft tissue lead to increase in translucency of that side of the chest . 2 Note : Female breast normally radio-opaque , homogenous Absence of breast shadow (mastectomy ) result in increase translucency on that side . Interpretation of lateral film used to define lesion obscured on the PA view there are two clear spaces (retrosternal & retrocardiac spaces ) both of them have the same lucency . the vertebrae are more lucent as eye travel down the spine until the diaphragm . CT scan Indication of CT 1.evaluation nabnormalities on CXR 2.Investigation causes of breathless Acute in pulmonary oedoma Chronic e.g. interstitial lung disease 3.staging of cancer 4.evaluationn of vascular anatomy aortic aneurysm or dissection 5. Performing CT guided biopsy of lung /pleural /mediastinal mass A routine chest CT consist of contiguous sections . IV contrast media is given in many cases , partically when the purpose of examination is to visualized the mediastinum , the hila or pulmonary blood vessels. The images are usually viewed at both lung , mediastinal & bone widow To examine the entire chest the examination should be begin from posterior costophrenic recess to the lung apices , the time of single section should done within seconds to avoid motion artifact . 3 MRI : Limited use in pulmonary disease , but important in cardiac & aortic disease. US : Also limited use only useful in peripherally located lesion in contact with chest wall also used in guidance procedure . US can detect very little amount of free pleural effusion which is not detected in plain film. Radio-isotop lung scanning : The major indication is to diagnosis or excluded pulmonary embolism . There are two major types Fluorodeoxyglucose positron emission tomography b(FDGPET/CT) is taken by number of tumors ,primary lung cancer , metastasis & active lymphomatous tissue it used for staging lung cancer or lymphoma or for recurency unfortunately ,inflammatory conditions also concentrate FDG so the appearance is not entirely specific . Chest disease with normal CXR 1- obstructive air ways disease : asthma , emphysema , acute bronchiolitis , acute and chronic bronchitis . 2 – small lesions in the lung ( less than 1cmin diameter ) .even 1-2cm lung cancer may be difficult to identify . 3- pulmonary embolism without infarction . 4- certain infections e.g. viral infections and viral pneumonia . 5 – pleural abnormalities e.g. dry pleurisy . 6- mediastinal mass plain film is very insensitive for medistinal masses 4 The silhouette sign : the information on chest film largely egally depend on the contrast between the radilucent air in the lung compared with the opacity of diaphragm , mediastinum & diaphragm its invaluable sign for localizing disease from the plain chest radiography . an intrathoracic lesion touching a border of the heart , aorta or diaphragm will obliterate that border on the chest radiography. e.g. loss of the heart border must mean that the shadow lies in the anterior half of the chest . lesion in contact with the mediastinum or diaphragm cause loss their normally sharp boundaries Fluoroscopy : It used to observed 1. the movement of the diaphragm 2. demonstrate air trapping in cases of suspected inhalation of foreign body . Pulmonary angiography : 1. diagnosis of pulmonary emboli 2. diagnose congenital vascular disease . . 5