Criteria used for chest radiographs, which was applicable to any one of the views—anterior-posterior, posterior-anterior, or lateral
| Chest radiograph measures | Criteria | |
|---|---|---|
| Rotation | The medial ends of both clavicles should be equidistant from the spinous process of the vertebral body projected between the clavicles | |
| Degree of inspiration | Adequate inspiratory effort | Five to seven complete anterior or ten posterior ribs are visible |
| Poor inspiratory effort | Fewer than five anterior ribs | |
| Hyperinflated lung | More than seven anterior ribs | |
| Penetration of the film | Normal exposure | The first four vertebral bodies are visible |
| Underexposure | The vertebral bodies are not visible | |
| Overexposure | The film appears too ‘black’ and vertebral bodies are visible beyond the first four vertebral bodies | |
| Situs | Situs solitus | Liver and inferior vena cava on right side and fundus of stomach on left side Morphological right atrium lies on the right side and opposite the fundus of stomach Right-sided bronchus is shorter, wider, and more vertically oriented than left-sided bronchus |
| Situs inversus | Liver and inferior vena cava on left side and fundus of stomach on right side Left-sided bronchus is shorter, wider, and more vertically oriented than right-sided bronchus | |
| Isomerism | Right isomerism: liver with two right lobes, malrotation of bowel bilateral morphological right trilobed lungs Left isomerism: polysplenia bilateral morphological left bilobed lungs | |
| Position | Levocardia | Left-sided position of heart and cardiac apex directed leftward, anteriorly, and inferiorly |
| Dextrocardia | Right-sided position of heart and cardiac apex directed rightward | |
| Mesocardia | Midline position of heart with two apices directed anteriorly and inferiorly | |
| Thymic shadow | Assessed in frontal radiographs as widening of superior mediastinum. Thymic sail sign can be seen as a triangular extension of normal thymus laterally. The right lobe of thymus has a convex lateral margin and a straight inferior border gets demarcated by the minor fissure which gives the sail-like appearance. The anterior reflections of the ribs produce a wavy contour of the thymus known as the thymus wave sign. The inferior margin of the thymus merges with the margin of cardiac silhouette producing the notch sign | |
| Cardiomegaly | Presence and absence of cardiomegaly are determined by calculating the cardiothoracic ratio Cardiothoracic ratio = (A + B) – C, where A and B are maximal cardiac dimensions to right and left of midline respectively and C is the widest internal diameter of the chest Presence of cardiomegaly is suspected if the cardiothoracic ratio in neonates is > 60%, in infants is > 55% and in children is > 50% | |
| Right atrium enlargement | Increase in height (distance between the top of aortic arch and junction of superior vena cava and right atrium is less than right atrium and right cardio phrenic angle) Convexity of right cardiac border > 3 cm beyond right lateral vertebral border Right cardiac border > 4.5 cm from anatomic midline | |
| Left atrium enlargement | Lifting of left main bronchus Widening of carinal angle to right or obtuse angle and carinal angle > 90 degree Double density sign-chamber large enough to produce an oval-shaped, localized density on the right side and projecting outside the lower cardiac border | |
| Left ventricle enlargement | Left and downward apex Hypertrophy causes rounding of the cardiac apex Dilatation causes elongation either to left or left and downwards often combined with rounding of apex | |
| Right ventricle enlargement | Elevation of apex Pulmonary conus becomes prominent Aortic knuckle less prominent Filling of retrosternal space in the upper part in lateral view | |
| Position of aortic knuckle | Determined as indentation in bronchus either on left or right side | |
| Ascending aorta dilatation | Assessed by enlargement of the ascending aorta which is seen as an increase in low-density almost straight edge at right upper mediastinum | |
| Descending aorta dilatation | Assessed by enlargement of the descending aorta which is seen as an increase in low-density straight line at left side | |
| Main pulmonary artery dilatation | Determined by convex enlargement of pulmonary artery segment The other method is to draw a tangent line from apex of ventricle to the aortic knob and measure along a perpendicular to tangent line. The distance between tangent line and pulmonary artery should fall between 0–15 mm away from tangent line | |
| Right pulmonary artery dilatation | Assessed by enlargement of right pulmonary artery | |
| Left pulmonary artery dilatation | Assessed by enlargement of left pulmonary artery | |
| Pulmonary plethora | Presence of more than 5 vessels in the lungs or more than 3 in one lung Presence of end on vessels more than two times the diameter of accompanying bronchus En face vessels below the tenth posterior ribs Prominent upper and lower zone vessels Prominent hilar vessels on lateral view | |
| Pulmonary oligemia | Concave or absent main pulmonary artery Less than three vessels in the peripheral one-third of the lungs Small hilar, lobar, and segmental vessels | |
| Pulmonary arterial hypertension | Pruning of pulmonary arteries (> 50% loss of vessel diameter at any degree branching) RPDA diameter is more than that of trachea in children, RPDA > 16 mm in males, RPDA > 17 mm in females Calcification of main pulmonary artery and proximal branches | |
| Pulmonary venous congestion | Stage 1: redistribution or cephalization of blood flow (13–19 mmHg) | Constriction Blurring of lower zone vessels Effacement of hilar angle Dilatation of upper lobe vessel Cuffing of fluid around small bronchioles |
| Stage 2: interstitial oedema (20–24 mmHg) | Kerley lines Peribronchial cuffing Septal and interstitial oedema Pleural effusion | |
| Stage 3: alveolar oedema (> 25 mmHg) | Bat wings appearance Pleural effusion | |
RPDA: right posterior descending artery
