2Introduction Routinely obtained Pulmonary specialist consultation Inherent physical exam limitationsChest x-ray limitationsPhysical exam and chest x-ray provide complimentIn the United States, chest x-rays are routinely obtained for hospitalized adults. Pulmonary specialists will almost never provide a consultation without having seen a chest x-ray. In under developed countries chest x-rays are obtained very selectively and physicians rely mostly on physical exam and history for diagnosis. Physical examination of the chest has inherent limitations. Lesions located in the mediastinum, interstitium, and in the center of the lung are rarely picked up by physical exam. Ease of availability of chest x-ray has made many physicians avoid time consuming physical exam which in most cases fails to reveal all of the problems. As a result, physicians have lost the skill of physical exam. Just as physical examination has limitations, chest x-ray also has limitations, and it should be recognized that a normal chest x-ray does not rule out pulmonary problems. Interstitial, airway and pulmonary vascular disease in certain cases cannot be recognized by chest x-ray while it is easily evident on physical exam, e.g. asthmatics can have normal chest x-rays. Physical exam and chest x-ray provide a compliment of any information and they are not mutually exclusive. Physical exam in general is good for acute illness, while chest x-ray is better for chronic illness.
3Essentials Before Getting Started ExposureOverexposureUnderexposureSex of PatientMaleFemaleOverexposure causes a film to be too dark. Under these circumstances, the thoracic spine, mediastinal structures, and retrocardiac areas are well seen, but small nodules and the fine structures in the lung cannot be seen.Underexposure causes the film to be quite white. This is a major problem for adequate interpretation. It will make small pulmonary blood vessels appear prominent and may lead you to think that there are generalized infiltrates when none is really present.The major difference between male and female chest x-rays is caused by differences in the amount of breast tissue. Breast tissue absorbs some of the x-ray beam, essentially causing underexposure of the tissues in the path. This is not a problem if the inferior aspect of the breasts is above the hemidiaphragms.
4Essentials Before Getting Started Path of x-ray beamPAAPPatient PositionUprightSupineChest x-rays on ambulatory patients are usually done with the patient’s chest up against the film holder. The x-ray tube is behind the patient, and the beam passes from the back and exits in front of the chest. This is referred to as a PA (posterior to anterior) projection. If the patient is lying down, it is standard practice to take an AP (anterior to posterior) chest x-ray.For interpretive purposes, the main difference is that the heart will be magnified on an AP projection. This is because in the AP projection the heart is farther from the film and the x-ray beam diverges as it goes farther from the tube.The amount of inspiration is greater in an upright film, which allows for spreading of the pulmonary vessels and allowing clearer visualization. Another reason for preferring upright films is that small pleural effusions tend to run down into the normally deep costophrenic angles.A patient lying down is unable to take a full inspiration; the liver and abdominal contents are pushing up on the lungs and heart, and the result is that the pulmonary vessels are crowded. On a supine film, the standard AP projection combined with the cephalic push of the abdominal contents will make a normal heart appear large.
5Essentials Before Getting Started BreathInspirationExpirationThe degree of inspiration is important not only for assessing the quality and limitations of the examination but also for diagnosing different diseases.When standing, most adults can easily take an inspiration that brings the domes of the hemidiaphragms down to the kevel of the tenth posterior ribs.When sitting down, often the level is between the eighth and tenth ribs.If the radiograph has the domes of the diaphragms at the seventh posterior ribs, the chest should be considered hypoinflated, and you need to be very careful before diagnosing basilar pneumonia or cardiomegaly.
6Systematic Approach Bony Framework Soft Tissues Lung Fields and Hila Diaphragm and Pleural SpacesMediastinum and HeartAbdomen and Neck
7Systematic Approach Bony Fragments Ribs Sternum Spine Shoulder girdle ClaviclesFirst, inspect the BONY FRAMEWORK of the chest You should be able to count and number the ribs, inspect the capulae, humeri and shoulders, and clavicles, and seethe diaphragms overlying the posterior aspects of the 10th or 11th ribs (in a normal adult)> The spine and sternum are generally difficult to visualize in detail on standard PA films due to overlying shadows.
8Systematic Approach Soft Tissues Breast shadows Supraclavicular areas AxillaeTissues along side of breastsNext, inspect the soft the SOFT TISSUES that overlie the thoracic cage Note the breast shadows,supraclavicular areas, axillae, and tissues along the sides of the chest.
9Systematic Approach Lung Fields and Hila Hilum Lungs Blood vessels Pulmonary arteriesPulmonary veinsLungsLinear and fine nodular shadows of pulmonary vesselsBlood vessels40% obscured by other tissueExamine the LUNG FIELDS and HILA The hilum ("lung root") is the shadow of pulmonary artery and vein adjacent the heart shadow. Normal lung markings are the linear and fine nodular shadows of pulmonary vessels. Abnormalities in the lung fields are marked by excessive radiolucency, excessive radiopacity, or opacified areas.
10Systematic Approach Diaphragm and Pleural Surfaces Diaphragm Dome-shapedCostophrenic anglesNormal pleural is not visibleInterlobar fissuresNext, examine the DIAPHRAGM and PLEURAL SURFACES Diaphragmatic images in the lung bases are dense, radiopaque shadows made principally by the liver on the left and the spleen on the right. The normal pleura is not visible on the chest x-ray, except where two layers come together to form the interlobar fissures.
11Systematic Approach Mediastinum and Heart Heart size on PA Right side Inferior vena cavaRight atriumAscending aortaSuperior vena cavaFinally, examine the MEDIASTINUM and and HEART Displacement of the mediastinum is an important clue to disease in on or the other hemithorax. On the PA chest film, the normal right heart and mediastinal border is made up (from bottom to top) of the 1) inferior vena cava; 2) the right atrium; 3)ascending aorta; and 4) superior vena cava. The normal left heart and mediastinal border consists (from bottom to top) of the 1) left ventricle; 2) left atrium; 3)pulmonary artery; 4) aortic arch; and 5) subclavian artery and vein
12Systematic Approach Mediastinum and Heart Left side Left ventricle Left atriumPulmonary arteryAortic archSubclavian artery and veinThe normal left heart and mediastinal border consists (from bottom to top) of the 1) left ventricle; 2) left atrium; 3)pulmonary artery; 4) aortic arch; and 5) subclavian artery and vein
13Systematic Approach Abdomen and Neck Abdomen Neck Gastric bubble Air under diaphragmNeckSoft tissue massAir bronchogram
15Pitfalls to Chest X-ray Interpretation Poor inspirationOver or under penetrationRotationForgetting the path of the x-ray beamPoor inspiration results in high diaphragms and crowding of normal lung markings.Over- or under-penetration of the x-ray beam can obliterat or exaggerate important findings. On a properly-penetrated PA chest rafiograph, one can just make out the thoracic vertebrae overlying the image of the heart.Rotation from the true perpendicular on the PA chest film distorts normal structures. Check proper orientation by noting equal distances from the vertebral spines to the medial ends of the clavicles.
16Lung Anatomy Trachea Carina Right and Left Pulmonary Bronchi Secondary BronchiTertiary BronchiBronchiolesAlveolar DuctAlveoli
17Lung Anatomy Right Lung Left Lung Superior lobe Middle lobe Inferior lobeLeft Lung
18Lung Anatomy on Chest X-ray PA View:Extensive overlapLower lobes extend highLateral View:Extent of lower lobes
19Lung Anatomy on Chest X-ray The right upper lobe (RUL) occupies the upper 1/3 of the right lung.Posteriorly, the RUL is adjacent to the first three to five ribs.Anteriorly, the RUL extends inferiorly as far as the 4th right anterior ribThe right upper lobe (RUL) occupies the upper 1/3 of the right lung. Posteriorly, the RUL is adjacent to the first three to five ribs. Anteriorly, the RUL extends inferiorly as far as the 4th right anterior rib.
20Lung Anatomy on Chest X-ray The right middle lobe is typically the smallest of the three, and appears triangular in shape, being narrowest near the hilumThe right middle lobe is typically the smallest of the three, and appears triangular in shape, being narrowest near the hilum.
21Lung Anatomy on Chest X-ray The right lower lobe is the largest of all three lobes, separated from the others by the major fissure.Posteriorly, the RLL extend as far superiorly as the 6th thoracic vertebral body, and extends inferiorly to the diaphragm.Review of the lateral plain film surprisingly shows the superior extent of the RLL.Posteriorly, the RLL extend as far superiorly as the 6th thoracic vertebral body, and extends inferiorly to the diaphragm. Review of the lateral plain film surprisingly shows the superior extent of the RLL; there is considerable overlap between the more anterosuperiorly located RUL and the RLL. Similarly, the deep posterior gutters extend considerably inferiorly; with full inspiration, the lower lobe can extend may as low as L2, becoming superimposed over the upper poles of the kidneys.
22Lung Anatomy on Chest X-ray These lobes can be separated from one another by two fissures.The minor fissure separates the RUL from the RML, and thus represents the visceral pleural surfaces of both of these lobes.Oriented obliquely, the major fissure extends posteriorly and superiorly approximately to the level of the fourth vertebral body.Grossly, these lobes can be separated from one another by two fissures which anatomically correspond to the visceral pleural surfaces of those lobes from which they are formed. The minor fissure separates the RUL from the RML, and thus represents the visceral pleural surfaces of both of these lobes. The minor fissure is oriented horizontally, extending ventrally from the chest wall, and extending posteriorly to meet the major fissure. Generally, the location of the minor fissure is approximately at the level of the fourth vertebral body and crosses the right sixth rib in the midaxillary line. The right major fissure is more expansive in size than the minor fissure, separating the right upper and middle lobes from the larger right lower lobe. Oriented obliquely, the major fissure extends posteriorly and superiorly approximately to the level of the fourth vertebral body. The major fissure extends anteroinferiorly, intersecting the diaphragm at the anterior cardiophrenic angle
23Lung Anatomy on Chest X-ray The lobar architecture of the left lung is slightly different than the right.Because there is no defined left minor fissure, there are only two lobes on the left; the left upperThe lobar architecture of the left lung is slightly different than the right. Because there is no defined left minor fissure, there are only two lobes on the left; left upper
24Lung Anatomy on Chest X-ray Left lower lobesand left lower lobes
25Lung Anatomy on Chest X-ray These two lobes are separated by a major fissure, identical to that seen on the right side, although often slightly more inferior in location.The portion of the left lung that corresponds anatomically to the right middle lobe is incorporated into the left upper lobe.These two lobes are separated by a major fissure, identical to that seen on the right side, although often slightly more inferior in location. The portion of the left lung that corresponds anatomically to the right middle lobe is incorporated into the left upper lobe.It is important to understand that in most individuals, interlobar fissures are usually not completely formed; in some individuals there may be complete absence of a fissure thus losing the demarcation between lobes on gross examination.In general, fissures are not readily identifiable on plain films, with only small portions typically visualized at best. This is because fissures which are composed of only two layers of visceral pleura, may not present a significant radiographic interface and will not produce a shadow. However, if there is fluid within the pleural space or if the visceral pleura is thickened, fissures may be seen in their entirety.
26The Normal Chest X-ray PA View: Aortic arch Pulmonary trunk Left atrial appendageLeft ventricleRight ventricleSuperior vena cavaRight hemidiaphragmLeft hemidiaphragmHorizontal fissure
27The Normal Chest X-ray Lateral View: Oblique fissure Horizontal fissureThoracic spine and retrocardiac spaceRetrosternal space
28The Silhouette SignAn intra-thoracic radio-opacity, if in anatomic contact with a border of heart or aorta, will obscure that border. An intra-thoracic lesion not anatomically contiguous with a border or a normal structure will not obliterate that border.
31Understanding Pathological Changes Most disease states replace air with a pathological processEach tissue reacts to injury in a predictable fashionLung injury or pathological states can be either a generalized or localized processEach tissue reacts to injury in a predictable fashion. Multiple etiology can evoke a similar pathological reaction. Let us just exam the pathological process that can occur in the lung. Lung injury or pathological states can be either a generalized or localized process.
32Liquid Density Liquid density Increased air density Generalized LocalizedDiffuse alveolarDiffuse interstitialMixedVascularInfiltrateConsolidationCavitationMassCongestionAtelectasisLocalized airway obstructionDiffuse airway obstructionEmphysemaBulla
33Consolidation Lobar consolidation: Alveolar space filled with inflammatory exudateInterstitium and architecture remain intactThe airway is patentRadiologically:A density corresponding to a segment or lobeAirbronchogram, andNo significant loss of lung volumeConsolidation: In the lobar consolidation, a lobe is involved. The alveolar space is filled with inflammatory exudate made up of WBC, bacteria, plasma, and debris. In Pneumococcal pneumonia, the most common cause for lobar consolidation, the lobe goes through red hepatization and gray hepatization stage. In the stage of resolution, some secretions can be in the airway. The interstitium and architecture of the lung remain intact and complete recovery occurs. The lobe swells up initially and may shrink slightly later if there is significant secretions in the airway causing some obstruction. The airway is patent.Radiologically this transcribes to:1. a density corresponding to a segment or lobe2. airbronchogram, and3. no significant loss of lung volume.
34Atelectasis Loss of air Obstructive atelectasis: No ventilation to the lobe beyond obstructionRadiologically:Density corresponding to a segment or lobeSignificant loss of volumeCompensatory hyperinflation of normal lungsAtelectasis: Atelectasis means loss of air. In absorptive Atelectasis there is an obstructive lesion on the bronchus. There is no ventilation to the lobe beyond the obstruction. Gradually the air gets absorbed by pulmonary circulation. The involved lobe eventually is devoid of air and becomes atelectatic.Radiologic criteria for absorptive Atelectasis is1. a density corresponding to a segment or lobe,2. significant signs of loss of volume, and3. compensatory hyperinflation of normal lungs.
35Stages of Evaluating an Abnormality 1. Identification of abnormal shadows2. Localization of lesion3. Identification of pathological process4. Identification of etiology5. Confirmation of clinical suspensionComplex problemsIntroduction of contrast mediumCT chestMRI scanSTAGES OF EVALUATING AN ABNORMALITY:In reading chest x-rays, I recommend that you do it in 4 steps:Step: 1. Identify the abnormal shadows2. Anatomically localize the lesion3. Identify pathological process4. Identify the etiologyStep 1: Identification of abnormal shadowsYou have to know what is normal before you recognize abnormalities. Let us identify the normal structures in the thorax (heart, aorta, pulmonary artery, lung fields, costophrenic angles, diaphragm, trachea, etc.).Which lung is larger?Which diaphragm is higher and why?What is the normal size of the heart?What is the normal size and shape of the aorta?You need to know normal and variations before you can detect and recognize abnormal shadows on chest x-ray.
55COPD: increase in heart diameter, flattening of the diaphragm, and increase in the size of the retrosternal air space. In addition the upper lobes will become hyperlucent due to destruction of the lung tissue.
59Pseudotumor: fluid has filled the minor fissure creating a density that resembles a tumor (arrow). Recall that fluid and soft tissue are indistinguishable on plain film. Further analysis, however, reveals a classic pleural effusion in the right pleura. Note the right lateral gutter is blunted and the right diaphram is obscurred.
62Pneumonia:a large pneumonia consolidation in the right lower lobe Pneumonia:a large pneumonia consolidation in the right lower lobe. Knowledge of lobar and segmental anatomy is important in identifying the location of the infection