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Chest radiography is the most commonly ordered imaging test in emergency department patients. It can provide considerable diagnostic information for a wide variety of thoracic disorders. Its diagnostic capabilities are based largely on the contrast between the air-filled lungs and pathological processes that cause fluid accumulation within lung tissue.

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Although chest CT provides greater anatomical detail of the pulmonary parenchyma and is often used in non-emergency patients with pulmonary disease, the use of chest CT in the ED is limited to certain critical conditions that do not produce distinctive findings on conventional radiography. These include pulmonary embolism and aortic dissection. CT is also used in ED patients with major chest trauma to detect an aortic injury, pneumothorax, hemothorax and pulmonary contusions that may not be evident on the supine portable chest radiographs.

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In general, a diagnostic test should be ordered when the disease under consideration produces characteristic findings which help confirm or exclude the suspected disorder. A number of approaches can be used in deciding to order a radiograph.

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With a simplistic “geographic” approach, radiographs are obtained of the region where the patient is having symptoms, e.g., a chest radiograph in a patient with chest pain. Such an approach is ill-advised because it can lead to diagnostic errors, as well as excessive and unnecessary testing.

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Using a symptom-based approach to radiograph ordering, the decision to obtain radiographs is based on characteristics of the patient’s symptoms, for example whether the chest pain is severe or mild, pleuritic or pressure-like (Rothrock 2002).

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However, a more rational diagnosis-based approach is to first consider the potential disorders that might be present and then to obtain radiography if the suspected disorder has characteristic radiographic findings, such as pneumonia and pneumothorax. This approach is the most likely to yield clinically useful information and to avoid unnecessary testing. Determining which disorders need investigation in an individual patient is ultimately based on the clinical judgment, knowledge and experience of the practitioner.

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Two perpendicular views should be obtained whenever possible. The preferred frontal view is a postero-anterior view (PA view). This view is obtained in the radiology suite with the patient standing and the imaging cassette placed against the patient’s anterior chest wall. The x-ray beam is directed horizontally and traverses the patient from posterior to anterior. The patient’s hands are positioned on the hips, which moves the scapulae laterally and away from the lungs. The patient is instructed to take a full inspiration. The PA view is preferred because the heart and mediastinum are closest to the x-ray imaging cassette and therefore less distorted by magnification.

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When the patient is too ill or debilitated to stand for a PA view, an antero-posterior view (AP view) is obtained. The patient is in either a lying or sitting position. The sitting position is preferred whenever possible. The x-ray beam is directed downward towards ...

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