Quantitative apparent diffusion coefficients and T2 relaxation times in characterizing contrast enhancing brain tumors and regions of peritumoral edema.

To investigate the potential value and relationship of in vivo quantification of apparent diffusion coefficients (ADCs) and T2 relaxation times for characterizing brain tumor cellularity and tumor-related edema. A total of 26 patients with newly diagnosed gliomas, meningiomas, or metastases underwent diffusion-weighted and six-echo multisection T2-preparation imaging. Regions of interest (ROIs) were drawn on conventional MR images to include tumor (as defined by contrast agent enhancement) and immediate and peripheral edema. Areas of necrosis were excluded. Median values of ADCs and T2 in the ROIs were calculated. ADCs for gliomas were similar to those for meningiomas or metastases in all regions. Tumor T2 values for gliomas (159.5+/-30.6 msec) were significantly higher than those for meningiomas or metastases (125.0+/-31.1 msec; P=0.005). Immediate-edema T2 values for meningiomas or metastases (226.0+/-44.1 msec) were significantly higher than those for gliomas (203.5+/-32.8 msec; P=0.033). Peripheral-edema T2 values for gliomas (219.5+/-41.9 msec) were similar to those for meningiomas or metastases (202.5+/-26.5 msec; P=0.377). Both immediate- and peritumoral-edema ADCs and T2 values were significantly higher than those in tumor for both tumor types. ADCs and T2 values from all regions correlated significantly for gliomas (r=0.95; P<0.0001) and for meningiomas or metastases (r=0.81; P<0.0001). The higher immediate-edema T2 values for nonglial tumors than for gliomas suggest tumor-related edema (vasogenic vs. infiltrated) can be further characterized by using T2 values. There were significant correlations between ADC and T2 values.