الفهرس 
AnatomyOnly 14 pages are availabe for public view
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Abstract
Pulmonary embolism (PE) is a common diagnostic problem, particularly in hospitalized patients, with significant morbidity and mortality; the later reaching 30% in untreated cases. Objective testing for PE is crucial, because clinical assessment alone is unreliable and the consequences of misdiagnosis are serious. Failure to diagnose PE is associated with high mortality and incorrect diagnosis of the condition unnecessarily exposes the patient to the risks of anticoagulant therapy. There are several diagnostic modalities available to aid the diagnosis of PE, each with its own advantages and disadvantages. Chest X-ray may identify mimics of PE, such as pneumonia, pneumothorax or congestive heart failure. However, it may be normal despite PE and patients may have concomitant PE and pneumonia or PE and congestive heart failure. Pulmonary angiography was classically considered the gold standard technique for diagnosis of PE. On the other hand, it is invasive, labor intensive, costly and there is high interobserver variability in detection of subsegmental emboli. CT is readily available at most institutions and is rabidly becoming the first-line imaging test for assessment of patients suspected for pulmonary embolism. However, conventional single-slice CT has insufficient sensitivity for isolated peripheral PE. With CTPA, thrombus is directly visualized, mediastinal and parenchymal structures are evaluated, which may provide important alternative or additional diagnosises. The use of Multidetector row CTA significantly improves pulmonary arterial visualization in the middle and peripheral lung zones. Narrow collimation improves the quality of the transverse and multiplanar images, and faster acquisition times make the examination better tolerated and improve contrast and spatial resolution, which improves detection of peripheral pulmonary emboli. The most recent generations of Multislice CT scanners appears to outperform competing imaging modalities for accurate detection of central and peripheral PE. The clinical validity of using a CTPA to rule out PE is similar to that reported for conventional pulmonary angiography. Results suggest that withholding anticoagulant therapy after negative CT scan appears to be safe. Additional imaging for ruling out PE is not warranted. This strategy may minimize radiation exposure, invasive procedures and health care costs. But the major draw backs of CT pulmonary angiography are the use of intravenous contrast material and radiation exposure. CT pulmonary angiography has become an attractive mean for safe, highly accurate, cost effective diagnosis of PE and may provide alternative diagnosis and explanations for symptoms in the absence of PE. Multislice CTPA has overcome the past limitations of spiral CT and has become the first-line modality for imaging patients with suspected pulmonary embolism.