Brain metastasis of small cell lung carcinoma: comparison of Gd-DTPA enhanced magnetic resonance imaging and enhanced computerized tomography.

Small cell carcinoma of the lung (SCLC) frequently metastasizes into the brain, resulting in serious influences upon prognosis. Delayed brain damage caused by prophylactic cranial irradiation (PCI) is also problematic. Gadrinium diethylene triamine pentaacetic acid (Gd-DTPA) enhanced magnetic resonance imaging (MRI) was performed to detect early brain metastasis from SCLC, and its usefulness was compared with contrast computerized tomography (CT). Among 25 SCLC patients, brain metastasis was detected in 11 by MRI and in 10 by CT, although six of them were completely asymptomatic. In the 11 patients, 6.3 and 2.4 lesions were respectively detected on average by MRI and CT. The ability of MRI to detect metastatic lesions of > or = 15 mm diameter did not differ from that of CT, but became different as lesions became smaller (P < 0.002), and MRI had a decided advantage over CT because as many as 30 lesions of < or = 5 mm diameter were detected by MRI, whereas such lesions visualized on CT numbered only one (P < 0.0001). MRI was incomparably superior to CT (P < 0.0004) for subtentorial lesions since 18 lesions were detected on MRI, but only three, measuring > or = 25 mm in diameter, were demonstrated on CT. Gd-DTPA enhanced MRI was determined to be extremely useful in the early diagnosis of SCLC brain metastasis. MRI was thought to reduce delayed brain damage caused by PCI if performed according to an adequate schedule.