Figure 5a: Low mean ADC representing metastasis from primary lesion outside the central nervous system in a 62-year-old man with large B-cell lymphoma. (a) Transverse contrast-enhanced T1-weighted MR image shows large right frontal lobe enhancing lesion with mass effect. (b) Transverse T2-weighted MR image shows signal intensity of central portion of mass is only slightly higher than that of gray matter, suggesting high cell density. Signal intensity is lower than that shown for glioblastoma in Figure 4. (c) Transverse ADC map shows mass has lower signal intensity than normal tissue. Mean ADC in the mass region of interest (1) was 65% of that of normal tissue, much lower than that for patient in Figure 4.