HOW TO READ CXR
Post on 13-Apr-2017
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HOW TO READ CXRDR R KR PRADHAN, MDLOWER ASSAM HOSPITAL
IntroductionCXR Routinely obtained, most commonInherent physical exam limitationsChest x-ray limitationsCXR finding not always diagnosticPhysical exam and chest x-ray provide compliment
*In 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.
Essentials Before Getting StartedExposure
OverexposureUnderexposureSex of Patient
*Overexposure 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.
Essentials Before Getting StartedPath of x-ray beam
*Chest x-rays on ambulatory patients are usually done with the patients 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.
Essentials Before Getting StartedBreath
*The 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.
Systematic ApproachBony Fragments
*First, inspect the BONY FRAMEWORK of the chestYou 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.
Systematic ApproachSoft Tissues
Breast shadowsSupraclavicular areasAxillaeTissues along side of breasts
*Next, inspect the soft the SOFT TISSUES that overlie the thoracic cageNote the breast shadows,supraclavicular areas, axillae, and tissues along the sides of the chest.
Systematic ApproachLung Fields and Hila
HilumPulmonary arteriesPulmonary veinsLungsLinear and fine nodular shadows of pulmonary vesselsBlood vessels40% obscured by other tissue
*Examine the LUNG FIELDS and HILAThe 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.
Systematic ApproachDiaphragm and Pleural Surfaces
DiaphragmDome-shapedCostophrenic anglesNormal pleural is not visibleInterlobar fissures
*Next, examine the DIAPHRAGM and PLEURAL SURFACESDiaphragmatic 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.
Systematic ApproachMediastinum and Heart
Heart size on PARight sideInferior vena cavaRight atriumAscending aortaSuperior vena cava
*Finally, examine the MEDIASTINUM and and HEARTDisplacement 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
Systematic ApproachMediastinum and Heart
Left sideLeft ventricleLeft atriumPulmonary arteryAortic archSubclavian artery and vein
*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
Systematic ApproachAbdomen and Neck
AbdomenGastric bubbleAir under diaphragmNeckSoft tissue massAir bronchogram
Summary of Density AirFat (Grey)WaterTissueBone
Lung AnatomyTracheaCarinaRight and Left Pulmonary BronchiSecondary BronchiTertiary BronchiBronchiolesAlveolar DuctAlveoli
Lung AnatomyRight Lung
Superior lobeMiddle lobeInferior lobeLeft Lung
Superior lobeInferior lobe
Lung Anatomy on Chest X-rayPA View:
Extensive overlapLower lobes extend highLateral View:
Extent of lower lobes
Lung Anatomy on Chest X-rayThe right upper lobe (RUL) occupies the upper 1/3 of the right lung. Posteriorly, the RUL is adjacent to the first 3 to 5 ribs. Anteriorly, the RUL extends inferiorly as far as the 4th right anterior rib
*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 rib.
Lung Anatomy on CXRThe right middle lobe is typically the smallest of the three, and appears triangular in shape, being narrowest near the hilum
*The right middle lobe is typically the smallest of the three, and appears triangular in shape, being narrowest near the hilum.
Lung Anatomy on CXRThe 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.
Lung Anatomy on Chest X-rayThese lobes can be separated from one another by two fissures.The minor fissure separates the RUL from the RML, and thus represen