RESUMEN
<p><b>OBJECTIVE</b>To evaluate the value of three-phase pulmonary helical CT in diagnosing peripheral pulmonary cancer (diameter </= 3 cm).</p><p><b>METHODS</b>Serial single-slice dynamic scans were obtained with helical CT before and after injection of 100 ml contrast material in 60 patients with solitary pulmonary nodules (SPNs, diameter <or= 3 cm). The three-phase pulmonary helical CT was established by analyzing enhancement feature of thoracic aorta and pulmonary artery, and then the enhancement feature of three-phase pulmonary helical CT was analyzed.</p><p><b>RESULTS</b>The delayed times of three-phase pulmonary helical CT were pulmonary artery phase (15 second), bronchial artery phase (36 second), equilibrium phase (90 second) respectively. The prevalence model of density change for three-phase pulmonary helical CT: no enhancement, marked enhancement, moderate-enhancement in pulmonary cancer; slight or moderate-enhancement, marked-enhancement, marked-enhancement in inflammatory nodules; no enhancement or light-enhancement in tuberculoma and metastatic nodules. The enhanced branch and small spot vessels were demonstrated by bronchial artery phase in 82.9% of pulmonary cancer nodules.</p><p><b>CONCLUSION</b>The three-phase pulmonary helical CT could reflect the enhancement feature, blood supply of bronchial artery in peripheral pulmonary cancer (diameter </= 3 cm), it is helpful in early diagnosis and differentiation.</p>