Comparison of 133Xe single-breath and washout imaging in the scintigraphic diagnosis of pulmonary embolism.

Abstract

To compare the utility of 133Xe single-breath (SB) and prolonged washout (WO) imaging in the scintigraphic diagnosis of pulmonary embolism, ventilation and perfusion studies of 66 patients who had pulmonary angiography within 48 h were reviewed. The single-breath-perfusion (SB-P) and washout-perfusion (WO-P) studies agreed in 59 of 66 patients (89%). Each of the 7 patients with disparate interpretations had an SB-P interpretation with a high probability for pulmonary embolism and a WO-P reading of low probability, with 133Xe retention in areas which appeared normal on the SB image. SB images with 133Xe are not suitable as the sole determinant of ventilation-perfusion (V-P) match or mismatch, especially when subsegmental perfusion defects are present. Prolonged washout imaging improves the specificity of V-P imaging in patients with suspected pulmonary embolism.