RADIOLOGICAL ANATOMY OF THE CHEST : RADIOLOGICAL ANATOMY OF THE CHEST PRESENTED BY DRS FANIMI .O
AND ALADESAWE. A.Y
DEPTARTMENT OF RADIOLOGY F.M.C OWO PREAMBLE : PREAMBLE The roentgenogram of the adult chest outlines the heart ,lungs, bony thorax which include : the ribs , thoracic vertebra ,clavicle and scapulae. The soft tissue markings are also included.
It is useful to develop a method of studying the film, to make certain that all areas are searched
It is essential that the viewer should first find any abnormality and thoroughly inspect the neck, thoracic and the sub diaphragmatic upper abdominal structures. cont’d : cont’d The viewer should be able to recognise variations and abnormalities having in mind normal chest radiological features.
Roentgen observations must be correlated with all the available clinical information before a decision is reached.
In addition , more clinical information can be sought from the referring doctor or even the patient. NORMAL CHEST RADIOGRAPH PA VIEW : NORMAL CHEST RADIOGRAPH PA VIEW A : NORMAL CHEST
LATERAL VIEW NORMAL CHEST RADIOGRAPHAP VIEW : NORMAL CHEST RADIOGRAPHAP VIEW C VIEWING CHEST RADIOGRAPH : VIEWING CHEST RADIOGRAPH A routine pattern of plain x-ray film reporting can be ensured for proper scrutiny. A suggested scheme is listed below.
Heart and mediastinum.
Diaphragm. Cont’d : Cont’d Pleura.
Hidden areas e.g. bones(#,destructive lesion)mediastinum, hila,apices and posterior sulcus.
Hila: density, shape and position.
Subdiaphragmatic areas e.g. calcification, gas shadow.
Soft tissue: mastectomy, gas densities SOFT TISSUE : SOFT TISSUE Soft ts cast shadow on plain radiographs which are less dense radio-opacity.
Breast shadow result in increased opacity over the lower thorax bilaterally.
Nipple shadow may appear as round opacities in the 4th ant. Interspace or lower.
Breast and nipple shadow are usually bilateral and symmetrical.
NOTE: in some intra-pulmonary lesions metallic nipple marker may be used to differentiate nipple from lesion. NIPPLE SHADOWS : NIPPLE SHADOWS D NIPPLE SHADOW : NIPPLE SHADOW E Cont’d : Cont’d Linear shadow may result from the skin fold of a wasted patient.
A faint soft- ts shadow parallel to the clavicle results from over-lining skin fold and subcut ts.(Clavicular companion shadow.)
If there is a doubt concerning any subcut nodule,CT may be required. Bony thorax : Bony thorax Chest x-ray primarily visualizes intrathoracic structure but also outline the shoulder girdle ,ribs, cervical and thoracic vert.
Sternum is often well outlined .
Shape of the thorax varies with age and body habitus.
Angulations of the ribs varies with body types. downward angulations: minimal in short hypersthenic indv. And maximal in asthenic patient. Cont’d : Cont’d Intercostal space are numbered according to the intercostal rib above them and the ribs and the interspaces are designated into 2 groups : anterior and posterior.
The costal cartilages are not visible except when calcified which then assumes characteristic mottled appearance (periphery in male but central in female).
Diaphragm in a normal adult is slightly higher on rt compared to the Lt. Cont’d : Cont’d The ribs below the diaphragm are not clearly seen as the other ribs.
Rhomboid fossa is an irregular rounded indentation on the inferior surface of the clavicle at the sternal end which houses the attachment of rhomboid ligament . it varies in depth, shape and has no clinical significance. MEDIASTINUM. : MEDIASTINUM. This is the space btw the rt. and lt. pleurae in and near the median sagittal plane of the chest.
It is bounded by posterior surface of the sternum and the anterior surface of the thoracic vertebrae.
It contains all the thoracic viscera except for the lungs.
It is divided into superior and inferior parts by an imaginary horizontal line passing through the sternal angle of Louis backwards to the lower border of T4 vertebrae.
The inferior is further divided into the ant, middle and post by the fibrous pericardium. ANTERIOR MEDIASTINUM : ANTERIOR MEDIASTINUM This is bounded above by thoracic inlet, laterally by the pleural , anteriorly by the sternum and posteriorly by the pericardium and the great vessels.
It contains loose areolar tissue , lymph nodes, lymphatic vessels , thyroid, thymus, parathyroid and internal mammary vessels.
It is seen as a triangular area of radiolucency btw the sternum and heart on lat view radiograph . MIDDLE MEDIASTINUM : MIDDLE MEDIASTINUM It is also referred to as vascular space.
It is bounded by anterior and posterior mediastinum.
It contains the heart ,pericardium ,ascending and transverse arch of the aorta, SVC and azygos veins that empties into it brachiocephalic vs , the phrenic nv , the upper vagus nerves, the trachea and it bifurcation, the main bronchi, the pulmonary veins and adjacent. POSTERIOR MEDIASTINUM : POSTERIOR MEDIASTINUM It is also known as post vascular space.
It lies btw the heart anteriorly and the thoracic vertebrae from the thoracic inlet to the T12.
It contains descending aorta ,oesophagus, thoracic duct ,azygos and hemiazygos vein, lymph nodes ,sympathetic chains and inferior vagus nerves. MEDIASTINAL PLEURAL REFLECTION : MEDIASTINAL PLEURAL REFLECTION Anterior junction line: this a vertical line ant. to the trachea,post.to the sternum and extends downward to the left .(appositions of the pleura of the upper lobes ant)
Posterior junction line: This is a thin vertical line posterior to the trachea and oesophagus, extends from the T.inlet to the level of the azygos and the aortic arches( represents the approximation of parietal and viseral pleura of the upper lobe posteriorly) Cont’d : Cont’d Azygoesophageal recess:-this recess outlines the medial aspect of the rt lower lobe & the lat. aspect of the oesophagus.
The rt paratracheal stripe:-This is a vertical stripe consisting of the rt lat. tracheal wall and the adj.parietal & viseral pleura of the rt upper lobe.(significances-altered by mediastinum and pleural dx)
Para spinal interface(pleural reflection):- this is the vertical line interface created on the rt side posteriorly, due to closely applied pleura to lat. aspect of the T.vertebra.while on the Lt a paraspinal interspace is created btw the descending aorta and lungs. MEDIASTINAL LYMPH NODES. : MEDIASTINAL LYMPH NODES. They are divided into 2 main groups:-Anterior mediastinal and para-tracheobronchial.
Anterior mediastinal node (pre-vascular nodes) lies anteriorly to SVC and the rt innominate vein on the right and anterior to the aorta and carotid on the left.
Ductus nodes are in the region of aorto-pulmonary window (a concave space btw the inferior aspect of the transverse aortic arch and pulmonary artery.) NB: when these nodes are enlarged the concavity is effaced. PARATRACHEOBRACHIAL NODES : PARATRACHEOBRACHIAL NODES These groups of lymph nodes are divided into:(1) Para-tracheal ( 2)Sub-cardinal nodes(tracheal bifurcation nodes) (3)Pulmonary root nodes( hilar ) (4)intrapulmonary nodes,(5)extra-pleural nodes( paravertebral, int. mammary and diaphragmatic nodes).
NB: normal nodes are small and cannot be evaluated on cx-ray Cont’d : Cont’d Rt main bronchus- upper lobe bronchus( epiarterial bronchus)-hyparterial bronchus(bronchus intermedius)-rt lower lobe bronchus.
Middle lobe bronchus takes origin from the lower end of intermedius bronchus.
On the Lt: main bronchus( forms the greater portion of the sub cardinal angle) divides into upper and lower lobe bronchus Roentgen important features. : Roentgen important features. The trachea spans downward from the C6 vert till it reaches the T5 where it bifurcates.
Trachea a mid-line structure except for very slight deviation to the rt at the level of aortic arch, moderate deviation to the rt is common in infant.
It represent a band of radiolucency in the mid-line that extends from the lower cervical to point of bifurcation. The two main bronchus appear the same but with smaller calibers.The rt main bronchus continues downward, vertical and shorter than the Lt. Cont’d : Cont’d The dense shadow observed in the frontal chest projection is formed by the mediastinum, sternum and the thoracic spine.
The superior border on the RT is occupied by BC vessel underneath them lie SVC while on the LT ;subclavian art occupies it.
Aortic arch is usually not border forming except in cardiac or aortic disease(represented by radiopaque convex bulge) cont’d : cont’d Hilum and the pulmonary art. lie immediately below the ascending aortic arch. A short segment of pulmonary outflow may sometimes be visible below the hilium.
Lower rt mediastinal border is formed by the convex border of the rt atrium while the Lt ventricle form most of the Lt mediastinal border. Cont’d : Cont’d Thymus is usually visible in infants and occupies the superior part of ant. mediastinum(causes widening of the mediastinum when present).There is need for a lateral view to confirm it.
Sail sign:-An acute angle formed on one or both side by the inferior aspect of an enlarged thymus . Cont’d : Cont’d The course of left superior intercostal vein around the aortic arch is somewhat variable but when it is lateral, superiolateral or inferiolateral to the aorta a small protuberance called aortic nipple is produced(4nd in 1.4% normal chest and deduced by Friedman and colleague).
Hilium: contains pulmonary vs,bronchus,bronchial vs and L.nodes.NB pulmonary vs produce most of the opacity outlined by plain radiograph and the Lt hilum is higher than the rt;(hilar height ratio is of impt) Cont’d : Cont’d Normal sized L.nodes in the region of the hilium do not contribute enough to the opacity of the hilium.
Causes of hilar enlargement:-(1)increased blood flow.(2) Lymphadenopathy(3)Normal variations.
When there is enough air in the oesophagus a tracheo- oesophageal stripe may be seen, however eso. may be outlined by barium meal to clearly define it’s relation to other mediastinal structures & detection of abnormality .