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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
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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 .
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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 .
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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
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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 .
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