Abstract: ObjectiveTo study the application of magnetic resonance imaging (MRI) diffusion-weighted imaging (DWI) in brain metastases, and the relationship between DWI results and the primary tumor pathology. Methods76 cases with brain metastases were grouped according to the primary cancer pathology. The apparent diffusion coefficient (ADC) of tumor parenchyma, capsule area, edema around tumors and normal parenchyma were determined; the ratio of high signal on the DWI were calculated (namely diffusion limited) in different tumor. ResultsThe ADC was (1.1364±0.310)×10^-3 mm²/s in tumor parenchyma, (2.167±0.472)×10^-3 mm²/s in capsule, (1.597±0.238)×10^-3 mm²/s in edema and (0.812±0.158)×10^-3 mm²/s in normal parenchyma (P<0.05). 15 cases appeared diffusion limited (19.7%), in which the primary tumors were lung cancer in 10 patients (66.6%) (including 5 cases with small cell lung cancer, 5 cases with none small cell lung cancer), breast cancer in 3 cases, and the other 2 cases were colon cancer and teratocarcinoma of testis (P>0.05). The minimum ADC were (0.72±0.16)×10^-3 mm²/s in tumor parenchyma with diffuse limited metastases and (0.78±0.21)×10^-3 mm²/s without diffuse limited (P=0.325). ConclusionDWI can respond to brain metastases to the microstructure change, but diffusion limited may not be related with the primary histopathology.

Key words: brain metastases, magnetic resonance imaging, diffusion-weighted imaging, apparent diffusion coefficient