Pulmonary embolism: Comprehensive diagnosis by using electron-beam CT for detection of emboli and assessment of pulmonary blood flow

PURPOSE: To comprehensively assess thoracic anatomy and pulmonary microcirc ulation in pulmonary embolism by using computed tomographic (CT) angiograph y of the pulmonary arteries combined with functional CT imaging of blood fl ow. MATERIALS AND METHODS: Twenty-two patients suspected of having acute pulmon ary embolism underwent contrast material-enhanced thin-section electron-bea m CT angiography of the pulmonary arteries. In addition, in each patient, a dynamic multisection blood flow CT study was performed on a 7.6-cm lung vo lume with electrocardiographic gating. Pulmonary blood flow was calculated, and perfusion parameters were visualized on color-coded maps. The color-co ded maps and CT angiograms were independently evaluated, segment by segment , by two readers for perfusion deficits and the presence of clots, respecti vely. The results were compared. RESULTS: Mean pulmonary blood flow was 0.63 mL/min/mL in the occluded segme nts versus 2.27 mL/min/mL in the nonoccluded segments (P = .001). The sensi tivity and specificity of perfusion maps for the presence of segmental pulm onary embolism compared with those of CT angiography were 75.4% and 82.3%, respectively, with positive and negative predictive values of 79.6% and 84. 7%, respectively. The false-negative findings were caused mainly by partial occlusion of vessels. In eight patients, a substantial alternative or addi tional pathologic entity was diagnosed. CONCLUSION: By combining CT angiography and dynamic CT imaging, a comprehen sive and noninvasive diagnosis of thoracic structure and function is feasib le with a single modality.