الفهرس 
ANATOMICAL CONSIDERATIONS:Only 14 pages are availabe for public view
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Abstract
Pulmonary embolism (PE) is a common condition with considerable morbidity and mortality; it is more often diagnosed postmortem by pathologists than in vivo by clinicians. Prompt and accurate diagnosis is difficult because PE may be clinically silent, the symptoms are vague and non-specific, and in addition there is no definitive, non invasive diagnostic test to establish its diagnosis.
The advent of chest CT scanning for the diagnosis of pulmonary embolism was hailed as an improvement, even before recent studies were undertaken. By 2001, CT scanning was being used more often than lung scanning to investigate suspected pulmonary embolism.
There are now multiple generations of CT scanners, but even first generation machines delivered images that were dramatic in clarity, rapidly acquired, and accurate in delineating the proximal pulmonary arterial tree. This noninvasive technology has evolved rapidly. A 16-slice multidetector-row CT scanner can image the entire chest with sub millimeter resolution and requires a breath-hold of less than 10 seconds.
The most important advantage of CT over other imaging modalities is that both mediastinal and parenchymal structures are evaluated, and thrombus is directly visualized. Studies have shown that up to two thirds of patients with an initial suspicion of PE receive another diagnosis, some with potentially life-threatening diseases, such as aortic dissection, pneumonia, lung cancer, and pneumothorax.
Most of these diagnoses are amenable to CT visualization, so that in many cases a specific etiology for the patients’ symptoms and important additional diagnoses can be established.
Use of high resolution multidetector-CT protocols was shown to improve visualization of pulmonary arteries and the detection of small subsegmental emboli and such small peripheral clots that might have gone unnoticed in the past are now frequently detected, often in patients with minor symptoms.
In suspected PE, establishing an unequivocal diagnosis as to the presence or absence of emboli or other disease based on a high-quality multidetector-row CT examination may reduce the overall radiation burden of patients, since further work-up with other tests that involve ionizing radiation may be less frequently required.
As compared with single–detector row scanning, pulmonary angiography with multi–detector row CT significantly improves vessel visualization in the middle and peripheral lung zones.
Multiplanar reconstructions improve the ability to identify the origin of middle and peripheral vessels and connect them with their central arteries of origin. Narrower 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 may improve detection of peripheral pulmonary emboli.