Ventilation-perfusion scans

Because contrast studies are expensive, invasive, and technically difficult to perform and evaluate, noninvasive tests (e.g., ultrasonography, computed tomography scans, and the ventilation-perfusion scan) are used frequently for the initial evaluation of patients with suspected VTE. 

Clinically, functional imaging (by, e.g., echocardiography or ventilation-perfusion scanning) provides useful information distinct from that obtained with... 

Cardiovascular In a study of the risk of pulmonary embolism in 64 patients aged 3 months to 22 years, receiving parenteral nutrition, 25 (39%) had an abnormal ventilation-perfusion scan and 29 episodes of pulmonary embolism were diagnosed. The median age at time of diagnosis was 4.6 years [54 "]. Pulmonary embolism was bilateral in 56% and unilateral in 44% and was the main cause of two of 15 recorded deaths. 

Ventilation/perfusion scan especially for single LuTX... 

Right and left heart catheterizations, quantitative ventilation-perfusion scanning as well as multiplegated acquisition radionuclide ventriculography are also obtained if clinically relevant (Kazerooni et al. 1995). 

Electrocardiograph normal sinus rhythm Chest x-ray slightly enlarged heart Ventilation/perfusion (V/Q) scan high probability of PE... 

Ventilation-perfusion (V/Q) and computed tomographic (CT) scans are the most commonly used tests to diagnosis PE. A V/Q scan measures the distribution of blood and airflow in the lungs. When there is a large mismatch between blood and airflow in one area of the lung, there is a high probability that the patient has a PE. Spiral CT scans can detect emboli in the pulmonary arteries. 

The main diagnostic practices with radiopharmaceuticals are the procedures for bone, cardiovascular, lung perfusion, lung ventilation, thyroid scan, thyroid uptake, renal, liver/ spleen, and brain examinations. The effective doses per procedure are considerably higher and are 4.5 mSv, 8 mSv, 1.5 mSv, 1 mSv, 3.4 mSv, 15 mSv, 1.9 mSv, 1.7 mSv, and 6 mSv, respectively, and the number of procedures per 1,000 population are 4.5, 2.7, 1.8, 0.34, 4.1, 0.92, 0.89, 2.1, and 1.3, respectively for countries at health-care level I. But patients near to the end of their lives receive many of these exposures, and thus the doses are not distributed evenly among the population. Therefore, these doses should not be used for the assessment of detrimental effects of radiation exposure. 

Ventilation-peifiision scans may be helpful since a markedly abnormal pattern of patchy, matched ventilation and perfusion defects is often seen. Magnetic resonance imaging with hyperpolarized 3He, 99mTc-Technegas, and 133Xe dynamic SPECT have made possible the noninvasive reproducible measurement of structure-function relationship in small airways (10). 

Fig. 2. Right posterior obHque lung or V/Q scan of a 65-year-old man presented with acute onset of shortness of breath and pleuritic chest pain (pain with breathing), (a) The perfusion lung scan showing defects in both the right upper lobe (arrow) and in the right lower lobe (arrowheads), (b) The ventilation...

Low Risk. CTA has a lower rate of patient discomfort, is less expensive, and has considerably lower risk of stroke and other vascular complications compared to conventional catheter angiography. It is also advantageous in situations when MR is contraindicated or cannot be performed. CTA is typically more readily available than MR, especially in emergency settings. CTA, unlike MRA, lends itself to the imaging of acutely ill patients, as there are no restrictions on the type and quantity of associated support equipment, such as intravenous pumps, ventilators, or monitoring hardware. Because CT scan acquisition is more rapid than that of MRA, CTA is less prone to motion artifact. When CTA is combined with CT perfusion (CTP) for the evaluation of acute stroke, quantitative perfusion data can also be obtained, which is not typically possible with MR perfusion imaging. 

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