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First-pass scintigraphy with (99m)Tc macroaggregated albumin: a method for evaluating pulmonary arterial flow
Marcelo T Sapienza1, Carla R Ono, Tomoco Watanabe
1Department of Radiology, University of Sao Paulo Medical School, Brazil. mtsapienza@hotmail.com
Objectives:
The aim of this work was to develop and describe a non-invasive scintigraphic technique to detect flow pulsatility in peripheral pulmonary arteries.
Methods:
Ten normal volunteers were submitted to a first-pass scintigraphy using Tc macroaggregated albumin (Tc-MAA). A time-activity curve was generated for the right lung lateral third. Activity was shown to be restricted to the arterial compartment of the lungs, since there was no detectable progression of the radiopharmaceutical to the systemic circulation. Consequently, the rise in lung activity was attributed to the arterial inflow and the first derivative of the time-activity curve was assumed to represent pulmonary arterial flow.
Results:
Pulmonary flow curves showed two main positive peaks in six volunteers, followed by a third small peak in three others. Flow was predominant during systole, with an important reduction in magnitude before the diastolic peak, leading to a negative count variation in eight subjects. This pattern is comparable to that described in central pulmonary vessels by different methods.
Conclusions:
First-pass scintigraphy with Tc-MAA was able to detect flow pulsatility in pulmonary arteries. These results need to be confirmed in a larger number of individuals, and, if shown to be reproducible, may increase our understanding of lung flow physiology, and of its modifications in the presence of cardiopulmonary diseases.