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Abstract
Pulmonary embolism (PE) is a frequent disease which requires an accurate diagnosis in order to establish an effective treatment considering that anticoagulant therapy may lead to complications. Lung ventilation / perfusion scintigraphy (LS V/Q) has been employed as the imaging meted of choice in patients with suspicion of PE. Pulmonary angiography is considered invasive, hence its utilization is usually reserved for otherwise unresolved cases. Other methods like venous Doppler ultrasound and echocardiography have a complementary role or are not widely indicated. The introduction of spiral CT (SCT), specially with multislice capabilities has made available a fast, relatively economic and efficient method for non-invasive diagnosis of PE. Availability of the technique is increasing and it has been included in some diagnostic algorithms for PE as the initial method of evaluation (and sometimes the only one). However, most research has been performed comparing this state-of-the-art technology with classical radionuclide protocols instead of using updated techniques such as SPECT and ultrafine radioaerosols. Moreover, SCT delivers much higher dose rates to the patient which must be taken into account specially in young individuals. In general, available evidence shows superior sensitivity of LS V/Q with higher specificity of SCT, within a context of similar overall accuracy provided optimized protocols are employed. Interpretation criteria for LS V/Q should be revised in an attempt to minimize indeterminate results, and together with the routine utilization of SPECT and novel ventilation systems should improve the performance of LS V/Q. The choice of the initial diagnostic modality should be guided by a correct determination of pre-test probability, clinical characteristics of the patient potentially influencing the efficacy and safety of the method, availability of the different techniques, relative costs and operator's experience. Such a selective and pragmatic approach will lead to a reasonably accurate diagnosis through a minimal number of steps.
Key words: pulmonary embolism, scintigraphy, perfusion, ventilation, spiral computed tomography.
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