FIG 1. A 61-year-old woman with PCNSL (patient 12 in Table 1). Demonstration of zones I and II. (See also serial image for this patient in Figure 4.)

A, Baseline axial T1-weighted image, after left frontal craniotomy. There is heterogeneous increased T1 signal intensity, consistent with subacute blood due to biopsy, in the center of the left frontal parasagittal hypointense lesion (arrow).

B, Baseline axial gadolinium-enhanced T1-weighted image. There is an intense enhancing mass (i.e., zone I) in the left frontal parasagittal region (arrow).

C, Baseline axial T2-weighted image. The mass (arrowhead) is of relative low signal intensity, characteristic of PCNSL due to the high cellularity of the tumor. The central portion has high T2 signal intensity, which is consistent with subacute blood secondary to prior biopsy. The surrounding larger area of increased T2 signal intensity represents edema or infiltrating tumor and is referred to as zone II (arrows).