Lymphomas: MR imaging contrast characteristics with clinical-pathologic correlations.

Mean pixel intensity ratios, contrast parameters, and T1-T2 cross products relative to fat and muscle were derived from T1-weighted and T2-weighted images obtained at 1.5 T in 32 patients with non-Hodgkin lymphomas and 20 with Hodgkin disease. Lymphomas were relatively homogeneous: Only 6% of the lesions had broad, bimodal, or skewed distributions of pixel intensities that could be attributed to intrinsic heterogeneity. On average, lymphomas were hypointense to fat and slightly hyperintense to muscle in T1-weighted images but isointense to fat and hyperintense to muscle in T2-weighted images. Low-, intermediate-, and high-grade non-Hodgkin lymphomas had identical imaging characteristics. The most striking and significant result was the greater brightness of lymphomas with dense fibrosis in T2-weighted images, which explains the trend toward greater brightness of Hodgkin disease than that of non-Hodgkin lymphomas and greater brightness of lymphomas in the mediastinum than of lymphomas in other locations. Neither a contrast parameter nor the T1-T2 cross product added information not evident with the use of simple mean pixel intensity ratios.