OBJECTIVETo compare quantitatively the enhanced thin CT section with pathologic findings in pulmonary carcinoma, pulmonary inflammatory pseudotumor (IPT) and pulmonary tuberculoma so as to demonstrate the relation of degree of enhancement and the vascular structure within the lesion with special emphasis on pulmonary carcinoma.

METHODSEnhanced thin CT sections were obtained in 35 cases with nodular or patchy lesions in the peripheral lung field which are difficult to differentiate clinically. There were pulmonary carcinoma 21, inflammatory pseudotumor 7 and tuberculoma 7. The number of small vessels (inner diameter 0.02 approximately 0.1 mm), relatively large vessels (inner diameter > 0.1 mm) and their vascular bed areas were analyzed by computed image analyzing system. The relation between CT average attenuation and the number of vessels or the vascular bed areas were statistically evaluated.

RESULTS1. The differences of average attenuation in carcinoma, inflammatory pseudotumor and tuberculoma were statistically significant (P < 0.05). 2. The differences in number of small vessels, relatively large vessels and vascular bed areas among these three types of lesion were also significant (P < 0.05). 3. A positive correlation was found in the average CT affenuation of lung carcinoma and its number of small vessels and relatively large vessels and 4. A positive correlation was found between the average CT attenuation in these three lesions and the relatively large vessels, total vascular amount and vascular bed areas.

CONCLUSIONS1. The average degree of attenuation, being divided into four degrees, is of practical value in the differentiation of lung carcinoma, inflammatory pseudotumor and tuberculoma. 2. The average CT attenuation of lung carcinoma, inflammatory pseudotumor and tuberculoma is in direct proportion to the number of vessels and vessel bed areas and 3. The characteristic CT enhancement in lung carcinoma reflexes the condition of vessels and blood supply within the tumor.