<正>Objective: To investigate the enhancement basis and the mechanisms of solitary pulmonary nodules （SPNs） by comparing the differences in microvascular structure between benign and malignant lesions. Methods: Dynamic contrast-enhanced CT scan was performed on 53 patients with SPNs （diameter<3 cm. 38 peripheral lung cancers

5 hamartomas

10 inflammatory lesions） using a Siemens Plus S or a Marconi MX8000 multi-slices spiral CT scanner. The time-attenuation curves were interpreted. The microvascular density （MVD） and the continuity of the microvessels’ basemental membrane in the dissected specimens were observed with the ABC （avidin-biotin-complex） immuno-histochemical method in all patients. ResultS:The CT enhancement values of lung cancer （49. 05±16. 08 HU） and inflammatory lesions （49. 59±21. 30 HU） were significantly higher than those of hamartoma （8. 98±4. 56 HU） （t = 7. 48. P<0. 05; t = 8. 35

P<0. 05）. But the enhancement of lung cancer was similar to that of inflammatory lesions （t = 0. 76. P>0. 05）. The time-attenuation curve of inflammatory lesions tended to increase faster and reached a higher peak compared to the lung cancer

and both of them maintained a high plateau after crossing. The hamartoma showed a slight increase in the time-attenuation curve and demonstrated a low-plateau curve. The MVD of SPNs was positively correlated with CT enhancement （r=0. 8051）. The microvascular counts of peripheral lung cancer （48. 45±10. 09） and inflammatory lesions （19. 60±19. 94） were significantly higher than those of hamartoma （8.70±7.30） （t = 11.64

P<0.001;t = 6. 09. P< 0. 001）. but no significant difference was found between lung cancer and inflammatory lesions （t= -0. 26

P = （）. 799）. There was no difference in the continuity of basement membrane between nodules with an enhancement less than 30 HU and those with an enhancement higher than 30HU （x2 = 3. 13

P>0. 05 ）. Conclusion: The microvascular counts mainly contribute to the enhancement value of SPNs. The basement membrane is not related to nodule enhancement

but it might influence the pattern of the time-attenuation curve.