Figure 5.

Sample cases showing leakage-correction error using Method I owing to significant deviations in MTT between reference tissue and tumor. The top row shows results in a patient with grade III anaplastic astrocytoma (male, age 53 years). The tumor exhibits significantly elevated MTT values, resulting in large T₂^*-dominant leakage effects in the tumor in spite of the absence of contrast enhancement on the postcontrast T₁-weighted image. The incorrect K₂(T₂^*) estimation results in underestimation of nCBV using Method I (nCBV(I)) compared with the results of Method II (CBV(II)). The bottom row shows results in a patient glioblastoma (female, age 56 years). A similar overestimation of K₂ is observed in areas of elevated MTT, with corresponding underestimation of nCBV in the same regions as compared with the CBV values obtained with Method II. nCBV, normalized cerebral blood volume; MTT, mean transit time.