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Page 1Introduction : The chest x-ray is the most commonly performed radiographic exam. A chest x-ray is usually done for the evaluation of lungs, heart and chest wall. Pneumonia, heart failure, emphysema, lung cancer and other medical conditions can be diagnosed or suspected on a chest x-ray. The benefits vs. risks? Benefits · A physician may recommend a chest x-ray for a patient with shortness of breath, a bad or persistent cough, chest pain or a chest injury. In the instances of pneumonia, the site of pneumonia will appear white on the image. · A chest x-ray may also show advanced emphysema as well as other diffuse lung conditions, such as pulmonary fibrosis. · Lung cancers and tumors that spread to the lung may be visible on chest x-ray. However, lesions that are small or superimposed on normal structures may not always be visible. · Heart irregularities, such as fluid around the heart (pericardial effusion), an enlarged heart, or abnormal heart anatomy or congestive heart failure may also be visible on a chest x-ray. · Pleural effusions (fluid around the lungs) on one or both sides can be detected. Usually the cause of such fluid may be deduced from clinical data or other findings on the chest x-ray but it may be necessary to sample the fluid to determine its cause. Risks · X-rays are a type of electromagnetic radiation, are invisible and create no sensation when they pass through the body. The chest x-ray is one of the lowest radiation exposure medical examinations performed today. · Special care is taken during chest x-ray examinations to ensure maximum safety for the patient by paying attention to correct x-ray beam energies. Shielding the abdomen and pelvis with a lead apron helps reduce unnecessary radiation to the abdomen and pelvis. Women should always inform their doctor or x-ray technologist if there is any possibility that they are pregnant. · The effective radiation dose from this procedure is about 0.1 mSv, which is about the same as the average person receives from background radiation in 10 days. · Radiation risks are further minimized by: o Technique standards established by national and international guidelines that have been designed and are continually reviewed by national and international radiology protection councils. o Modern, state-of-the-art x-ray systems that have tightly controlled x-ray beams with significant x-ray beam filtration and dose control methods. Thus, stray or scatter radiation is minimized and those parts of a patient's body not being imaged receive minimal exposure.
Limitations of Chest Radiography? · Normal chest x-ray does not necessarily rule out all problems in the chest. · Patients with asthma exacerbations can have a normal chest x-ray · Some cancers are too small or are difficult to visualize and may not be identified. · Blood clots to the lungs (pulmonary embolism) cannot be seen on chest x-rays and require additional study. · A chest CT may be requested to further clarify a finding seen on the chest x-ray or to look for an abnormality not visible on a chest x-ray in order to answer the clinical problem. Objectives of chest X-ray · Identify cardiothoracic anatomical structures demonstrable on a chest film. · Recognize a normal chest radiograph. · Recognize and name the radiographic signs of atelectasis, consolidation, pneumothorax, pleural and pericardial effusions, and hyperinflation frequently seen in patients with cardiopulmonary disease. · Correlate physical signs and symptoms of cardiopulmonary disease with chest radiographic findings.
Different views of chest film · Standard Views · Standing (Upright Chest X-Ray) o Posteroanterior (PA) Film
Left Lateral X-Ray · Request right lateral film if right-sided finding · More sensitive than PA for abdominal free air
Supine (Portable Chest X-Ray) · Anteroposterior (AP) Film · Magnifies heart and anterior mediastinum · Emphasizes rib and calcium contrast · Lung parenchyma may appear washed out
Page 2Special Views · Inspiration and Expiration Film Indications o Pneumothorax accentuated on expiration o Unilateral diaphragmatic paralysis o Unilateral obstruction of major bronchus · Lordotic View Indications o Posterior Apical Disease o Middle Lobe disease § Reverse Lordotic View Indications o Anterior apical disease · Oblique Film o Peripheral small lesions o Separated from overlying chest shadows o Lesions poorly seen on lateral chest X-Ray o Rib fractures (at axillary lines) · Lateral decubitus Film o Detect small areas of air at uppermost pleural space o Detect small areas of dependent pleural fluid o Measure size and mobility of fluid collection o Accessible with sampling needle (>1 cm size) o Uncover Lung tissue obscured by pleural fluid o Place side of interest up o Mobility of mediastinal or pleural masses o Assess mobility of solids and fluids within cavities o Assist with maximizing inspiration of uppermost lung
Barium Swallow · Enlarged retro-mediastinal nodes · Define Posterior intrathoracic mass · Confirm ruptured diaphragm or Diaphragmatic Hernia · Impaired swallowing with aspiration · Diagnostic Pneumothorax (instill air in pleural space) · Distinguish peripheral lung mass from pleural lesion · Define mesothelioma · Parenchymal disease extending towards chest wall Circumstances that decrease Chest X-Ray quality · Semi-upright position (neither standing nor supine) o May enlarge normal structures o Changes air-fluid levels · Lordosis or vertical axis rotation o Widens heart and mediastinum · Inadequate sustained inspiration o Breathing film --lung structures and diaphragm blurred o Expiration film --basilar infiltrates & interstitial structures accentuated , increased heart size
· Decreases Lung Volume --highlights infiltrates and interstitium · Increases venous return to heart --distends azygous vein and pulmonary vein · Diaphragm rises and intracardiac pressure increases--heart and mediastinal structures enlarge · Fluid and air migrate o Pleural Effusions disappear o Small Pneumothorax disappears o Air-Fluid levels (e.g. Lung Abscess) disappear Pneumothorax signs on supine film · Deep Sulcus sign o Costophrenic angle sharply outlined by air o Diaphragm-mediastinal junction sharply outlined · Hyperlucency superimposed over liver shadow
Page 3Interpretation The key to successfully interpreting any radiograph is to be systematic. Examine all parts of the film in an orderly manner, and do this consistently. Examine the easily overlooked items first and proceed to the areas where pathology is more likely to be found. Identification · Correct patient · Correct date and time · Correct examination Technique · Complete examination · Are all the requested views included? · Is the entire anatomical area included on the films? o Projection o Position o Penetration o Rotation
Inspiration Systematic Review · General o Compare findings from side to side · Alignment o Note if patient is lordotic or kyphotic o Note patient rotation o Spinous processes midway between clavicle heads · Specific points of exam o Lines and Tubes o Bones o Soft tissues o Pleural spaces o Mediastinum o Cardiovascular structures o Lung parenchyma o Infradiaphragmatic areas · Standard Checks o Hilum is higher on the left o Hemidiaphragm is lower on the left o May be variable in older patients o Right hemidiaphragm sharply outlined o Left hemidiaphragm sharply outlined lateral to apex
· Localize any lesion on both lateral and AP o Endotracheal Tube should be above carina --usually overlies 5-6th vertebrae o Trace intravenous lines along entire course o Trace Nasogastric Tubes along entire course Findings Mass vs. Infiltrate
The basic diagnostic instance is to detect an abnormality. In both of the cases above, there is an abnormal opacity. It is most useful to state the diagnostic findings as specifically as possible, then try to put these together and construct a useful differential diagnosis using the clinical information to order it. In each of the cases above, there is an abnormal opacity in the left upper lobe. In case 1, the opacity would best be described as a like a cancer because it is well-defined. Case 2 has an opacity that is poorly defined. This is airspace disease such as pneumonia. Pneumomediastinum · Findings for pneumomediastinum include; streaky lucencies over the mediastinum that extend into the neck, and elevation of the parietal pleura along the mediastinal borders. · Causes of pneumomediastinum include; asthma, surgery (post-op complication), traumatic tracheobronchial rupture, abrupt changes in intrathoracic pressure (vomiting, coughing, exercise, and parturition), ruptured esophagus, barotrauma, and smoking crack cocaine. · Pneumomediastinum should be distinguished from pneumopericardium and pneumothorax. In pneumopericardium, air can be present underneath the heart, but does not enter the neck.
Silhouette Sign One of the most useful signs in chest radiology is the silhouette sign. This was described by Dr. Ben Felson. The silhouette sign is in essence elimination of the silhouette or loss of lung/soft tissue interface caused by a mass or fluid in the normally air filled lung. In other words, if an intrathoracic opacity is in anatomic contact with, for example, the heart border, then the opacity will obscure that border. The sign is commonly applied to the heart, aorta, chest wall, and diaphragm. The location of this abnormality can help to determine the location anatomically. Take a moment to review the makeup of the mediastinal margins and the lobes of the lungs that interface with the mediastinum. Use the back button on your browser to return here. For the heart, the silhouette sign can be caused by an opacity in the RML, lingula, anterior segment of the upper lobe, lower aspect of the oblique fissure, anterior mediastinum, and anterior portion of the pleural cavity. This contrasts with an opacity in the posterior pleural cavity, posterior mediastinum, of lower lobes which cause an overlap and not an obliteration of the heart border. Therefore both the presence and absence of this sign is useful in the localization of pathology.
Air Bronchogram An air bronchogram is a tubular outline of an airway made visible by filling of the surrounding alveoli by fluid or inflammatory exudates. Six causes of air bronchograms are; lung consolidation, pulmonary edema, nonobstructive pulmonary atelectasis, severe interstitial disease, neoplasm, and normal expiration
This patient has bilateral lower lobe pulmonary edema. The alveoli are filled with fluid making the bronchi visible as an air bronchogram. Figure 2 is a close-up of the right side of the film with arrows outlining a prominent air bronchogram. Figure 3 is a CT scan demonstrating an air bronchogram clearly. Lobar Collapse (Atelectasis) - Atelectasis is collapse or incomplete expansion of the lung or part of the lung. This is one of the most common findings on a chest x-ray. It is most often caused by an endobronchial lesion, such as mucus plug or tumor. It can also be caused by extrinsic compression centrally by a mass such as lymph nodes or peripheral compression by pleural effusion. An unusual type of atelectasis is cicatricial and is secondary to scarring, TB, or status post radiation. Atelectasis is almost always associated with a linear increased density on chest x-ray. The apex tends to be at the hilum. The density is associated with volume loss. Some indirect signs of volume loss include vascular crowding or fissural, tracheal, or mediastinal shift, towards the collapse. There may be compensatory hyperinflation of adjacent lobes, or hilar elevation (upper lobe collapse) or depression (lower lobe collapse). Segmental and subsegmental collapse may show linear, curvilinear, wedge shaped opacities. This is most often associated with post-op patients and those with massive hepatosplenomegaly or ascites.
Pulmonary Infiltrates--pulmonary Edema · There are two basic types of pulmonary edema. One is cardiogenic edema caused by increased hydrostatic pulmonary capillary pressure. The other is termed non-cardiogenic pulmonary edema, and is caused by either altered capillary membrane permeability or decreased plasma oncotic pressure. · A helpful mnemonic for non-cardiogenic pulmonary edema is NOT CARDIAC (near-drowning, oxygen therapy, transfusion or trauma, CNS disorder, ARDS, aspiration, or altitude sickness, renal disorder or resuscitation, drugs, inhaled toxins, allergic alveolitis, contrast or contusion. · On a CXR, cardiogenic pulmonary edema can show; cephalization of the pulmonary vessels, Kerley B lines or septal lines, peribronchial cuffing, "bat wing" pattern, patchy shadowing with air bronchograms, and increased cardiac size. Unilateral, miliary and lobar or lower zone edema are considered atypical patterns of cardiac pulmonary edema. A unilateral pattern may be caused by lying preferentially on one side. Unusual patterns of edema may be found in patients with COPD who have predominant upper lobe emphysema.
Pleural Effusion · On an upright film, an effusion will cause blunting on the lateral and if large enough, the posterior costophrenic sulci. Sometimes a depression of the involved diaphragm will occur. A large effusion can lead to a mediastinal shift away from the effusion and opacify the hemothorax. Approximately 200 ml of fluid are needed to detect an effusion in the frontal film vs. approximately 75ml for the lateral. Larger effusions, especially if unilateral, are more likely to be caused by malignancy than smaller ones. · In the supine film, an effusion will appear as a graded haze that is denser at the base. The vascular shadows can usually be seen through the effusion. An effusion in the supine view can veil the lung tissue, thicken fissure lines, and if large, cause a fluid cap over the apex. There may be no apparent blunting of the lateral costophrenic sulci. · A lateral decubitus film is helpful in confirming an effusion in a bedridden patient as the fluid will layer out on the affected side (unless the fluid is loculated). Today, ultrasound is also a key component in the diagnosis. Ultrasound is also used to guide diagnostic aspiration of small effusions.
Tuberculosis · Primary tuberculosis (TB) is the initial infection with Mycobacterium tuberculosis. Post-primary TB is reactivation of a primary focus, or continuation of the initial infection. Radiographically, TB is represented by consolidation, adenopathy, and pleural effusion. A Ghon focus is an area of consolidation that most commonly occurs in the mid and lower lung zones. A Ghon complex is the addition of hilar adenopathy to a Ghon focus. · Radiographic features of post-primary TB are; focal patchy airspace disease "cotton wool" shadows, cavitation, fibrosis, nodal calcification, and flecks of caseous material. These occur most commonly in the posterior segments of the upper lobes, and superior segments of the lower lobes. · Endobronchial TB involves the wall of a major bronchus. Complications of endobronchial TB are cicatrical stenosis and obstruction.
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