[Preliminary study of astrocytic tumors by diffusion tensor imaging].

BACKGROUND & OBJECTIVE: Diffusion tensor imaging (DTI) is an advanced quantitative form of diffusion-weighted imaging. It could be used to calculate not only the apparent diffusion coefficient (ADC) of average water diffusion for each vowel, but also the diffusion anisotropic index of diffusion. Diffusion-weighted imaging is used in most of the studies of the brain tumors abroad. We used DTI method to measure the ADC, fractional anisotropy (FA) and relative anisotropy (RA), values of different tumor tissues and to evaluate the usefulness of ADC, FA, and RA in differentiating solid tumor, necrotic region, edema region, normal brain tissue, and in grading the malignancy of cerebral astrocytomas.

METHODS

Fourteen cases of astrocytomas diagnosed (10 cases of grade 1-2 astrocytomas and 4 cases of grade 3-4 astrocytomas) were studied by DTI. ADC, FA, and RA values of different tumor tissue were measured.

RESULTS

When all cases were analyzed as a group, significant differences of ADC were found in enhancing solid tumor (1.14+/-0.13x10(-3) mm(2)/s), necrotic region (2.04+/-0.50x10(-3) mm(2)/s), edema region (1.55+/-0.19x10(-3) mm(2)/s) compared with normal brain tissue (0.74+/-0.08x10(-3) mm(2)/s)(P< 0.05). Significant differences of ADC were also found in solid tumor (enhancing tissue:1.14+/-0.13x10(-3) mm(2)/s, non-enhancing tissue:1.01+/-0.25x10(-3) mm(2)/s) compared with necrotic region and edema region, respectively (P< 0.05). Significant differences of FA and RA were found in solid enhancing region (FA:0.21+/-0.08; RA:0.23+/-0.07), necrotic region (FA: 0.14+/-0.06, RA: 0.16+/-0.07), edema region (FA:0.16+/-0.04, RA:0.16+/-0.02) compared with normal brain tissue (FA: 0.37+/-0.06, RA: 0.38+/-0.07) (P< 0.05). No difference of FA and RA was found in solid tumor (including enhancing and non-enhancing tissue). Significant differences of ADC (P< 0.05), not FA and RA, were found between grade 1-2 astrocytomas (1.07+/-0.04x10(-3) mm(2)/s) and grade 3-4 astrocytomas (1.32+/-0.08x10(-3) mm(2)/s).

CONCLUSION

Determination of ADC can be used to differentiate normal brain tissue from enhancing solid tumor, necrotic region, and edema region. Determination of FA and RA can be used to differentiate solid enhancing tumor, necrotic region, and edema region from normal brain tissue, but can not be used to differentiate solid tumor, necrotic region, and edema region. The ADC values, not FA and RA, may predict the degree of malignancy of astrocytic tumors.