الفهرس 
Radiiollogiicall Anatomy of the Lung and Pullmonary ArteriiesOnly 14 pages are availabe for public view
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Abstract
PE is a common and potentially fatal disorder for which treatment is effective and improves the chance of survival. PE is the third most common acute cardiovascular disease, after myocardial infarction and stroke, and it leads to thousands of deaths each year because it often goes undetected. Post mortum studies have indicated that 65% of hospitalized patients have PE. It has been estimated that 7% of hospital patients die as a result of PE as the sole cause (Beharry et al ., 2005). However , the accurate diagnosis of acute pulmonary embolism can be difficult because of unreliable clinical and laboratory findings.
Diagnosis of pulmonary embolism depends on clinical suspicious. PE is often under diagnosed due to the non specific nature of its signs and symptoms, which frequently seen in other cardiac and pulmonary conditions (Colombet et al., 2006).
The presence of predisposing factors that increase the risk for DVT should raise the suspicion for the presence of pulmonary embolism, Unfortunately, these conditions are non sensitive and non specific and are frequently present in patients who did not have pulmonary embolism. So, Objective testing for pulmonary embolism is crucial, because clinical assessment alone is unreliable and the consequences of misdiagnosis are serious (Kearon., 2003).
Chest radiograph findings are non-specific. The chest x-ray is often normal. Findings such as focal oligemia (Westermark sign), a peripheral wedge shaped opacity (Hampton’s hump), or an enlarged right descending pulmonary artery (Pall’s sign) are rare (Piazza& Goldhaber., 2006).
Performing lower extremity ultrasonography (US) for assessment for deep venous thrombosis (DVT) has become an important step in the current noninvasive work-up for pulmonary embolism (PE). Although there has been agreement as to its value, its location in the algorithm for PE assessment is variable (Robert et al., 1999).
In new millennium there have been major advances in chest imaging. These include significant refinements in previously available techniques such as computed tomography (CT) and magnetic resonance (MR) imaging and the introduction of new techniques into the clinical practice, particularly nuclear medicine and CT applications. These advances have led to changes in the diagnostic approach to a number of conditions, particularly pulmonary embolism, They have also brought new insights into the pathophysiology of lung disease (Muller, 2001).
The aim of this essay was to assess and summarize the most important clinical applications of the recent advances in imaging of PE.
CTV provides direct imaging of the inferior vena cava, pelvic, and lower extremity veins immediately after CTPA (CT Pulmonary Angiography) without injection of additional contrast material. Multisection CT venography is simple and accurate, and when combined with lung imaging it allows fast and comprehensive evaluation for thromboembolic disease (Wittram et al., 2004).
MR technology has also moved forward. Techniques include MR angiography (MRA) and thrombus imaging for direct clot visualization, perfusion MR, and combined perfusion-ventilation MR. As will be demonstrated, some of these techniques are now entering the clinical arena, and it is anticipated that MR imaging (MRI) will have an increasing role in the initial diagnosis and follow-up of patients with acute PE.
Gadolinium enhanced MR angiography of the pulmonary arteries may be helpful in patients with contraindications to the use of iodinated contrast material. reports showing a sensitivity of 68–77% and a specificity of 95–100%.
MRV may be used to evaluate central venous pathology, anatomic variants, and DVT of the extremities. MRV and MR pulmonary angiography remain second-line diagnostic tools because of higher cost, technical limitations, limited availability
Multi-detector row CT allows substantial reduction in examination time for standard protocols, coverage of the extended anatomic volumes, and increased longitudinal resolution by means of reduced section width.
The introduction of multislice CT into clinical radiology significantly widens the scope of vascular CT imaging. a 128x2-slice scanner and a ”dynamic volume” scanner based on 320 slices currently remains in a development phase but has demonstrated the potential to significantly reduce radiation exposure by eliminating the requirement for a helical examination in CT angiography.
Single detector CT, , showed a sensitivity of 73% and multidetector CT, mostly 4-slice, showed a sensitivity of 83%. Respective specificities were 87% and 96% ( Stein et al., 2007)
The V/Q lung scan has been a noninvasive technique to evaluate regional pulmonary perfusion and ventilation. Despite imaging in multiple projections, the perfusion scan may underestimate perfusion abnormalities (Worsley & Alavi ., 2003).
SPECT is a well-established imaging technique that is widely used in modern nuclear medicine diagnostics. tomographic imaging could supersede the sensitivity of planar techniques, simply by avoiding the overlapping of small perfusion defects by normal tissue.
CT and V/Q scans are not a competitor for diagnosis of PE but they are complementary modalities as simply the physical and biological bases and subsequently the outcome of each is different. V/Q scan is a functional imaging which demonstrate lung regions that affected by the embolus (embolus effect) while CT demonstrate (embolus itself).
The diagnosis of acute PE requires the integration of a careful history and physical examination with laboratory testing and appropriate imaging modalities. The data from this essay suggest that chest CT is at least as accurate as invasive pulmonary angiography. Alternative imaging modalities include ventilation-perfusion (V/Q) lung scanning, magnetic resonance (MR) angiography, transthoracic and transesophageal echocardiography, and invasive pulmonary angiography. V/Q scans are generally reserved for patients with major renal impairment, anaphylaxis to intravenous contrast , non diagnostic CT cases. MR angiography is a promising modality for detecting PE in the proximal pulmonary arteries and avoids the risks of iodinated contrast and ionizing radiation. However, no fixed diagnostic approach is present and flexibility in usage of different imaging modalities should be present , taking in consideration availability and cost effectiveness.
Radiologist must be accounted about the use of recent imaging modalities, when and How to interpret . In order to achieve such goal more frequent usage for these tools is needed to be more familial with its interpretation.