V/Q SPECT in the diagnosis of pulmonary embolism.
نویسندگان
چکیده
Pulmonary embolism (PE) is a frequent and potentially lethal disease caused by the migration of a thrombus to the pulmonary circulation, typically from the venous system of the lower limbs. Unfortunately, there are no specific sets of symptoms which accurately predict or exclude the diagnosis. Therefore, in clinical practice, the diagnosis always strongly relies on imaging. On the other hand, clinical evaluation can predict the probability of embolism in a specific patient. This information can be used to select which patient can benefit most from imaging studies. Historically, pulmonary angiography and planar ventilation perfusion (V/Q) scintigraphy were the main techniques available for identification of PE. Although traditionally viewed as the gold standard, pulmonary angiography is an invasive technique that suffers from significant limitations. It is not considered anymore as a suitable gold standard(Baile, King et al. 2000). V/Q scintigraphy was used extensively as a non-invasive alternative. It has a high sensitivity and a high negative predictive value. Unfortunately, the technique suffers from a large number of indeterminate studies in which the diagnosis of PE cannot be reliably confirmed or excluded. Indeed, in the PIOPED study, as much as 72% of cases were in that category. Although later studies substantially improved those numbers, the level of indeterminate findings remains high. It is in that context that computed tomography pulmonary angiography (CTPA) emerged as an alternative non-invasive technique. CTPA carries the advantages of a much lower rate of indeterminate study and the ability to diagnose alternate conditions for the patient's symptoms. Also, the binary interpretation (“positive” vs “negative”) was much more acceptable to physicians than the rather complex probabilistic system of V/Q scintigraphy. As such, it has become the principal imaging technique worldwide for the diagnosis of PE. In most centers, conventional planar V/Q scintigraphy is now a secondary technique used mainly when there are contraindications to CTPA or when CTPA is non-diagnostic or not available. Nonetheless, CTPA also suffers from significant limitations. There are contraindications such as impaired renal function and allergies. The radiation dose is very high, especially to
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ورودعنوان ژورنال:
- BMJ
دوره 346 شماره
صفحات -
تاریخ انتشار 2013