The Value Of Mr Perfusion Weighted Imaging And Mr Diffusion Weighted Imaging In Grading Astrocytoma

Objective To evaluate the grading effectiveness of MR perfusion weighted imaging (PWI) and MR diffusion-weighted imaging (DWI) in patients with astrocytoma.Materials and methods 40 patients who had undergone conventional MR imaging, dynamic contrast-enhanced T2*-weighted perfusion MR imaging and diffusion MR imaging on a SIEMENS 3.0T scanner were confirmed primary cerebral astrocytomas.14 cases were graded as low (I-II) and 26 cases were graded as high (III-IV).A retrospective blinded analysis of the imaging findings including the conventional MR imaging, the perfusion parameters and the diffusion parameters was done. The rCBV, rCBF, rMTT, ADC and rADC measurements were obtained from regions of the core and peritumoral of tumor and the corresponding opposite white matter respectively. Tumor grade determined with the three methods were then compared with the histopathologic grade. Mann–Whitney tests were performed to compare the DWI and PWI between tumor types. Receiver operating characteristic analyses were performed to determine optimum thresholds for tumor grading and also to calculate the sensitivity, specificity, positive predictive values (PPV) and negative predictive values (NPV). Sensitivity, specificity of the associating screening of PWI and DWI were obtained and then compared with the result of the conventional MR imaging.Results (1) Sensitivity, specificity, PPV, NPV and accuracy of conventional MR were 69.2, 64.3, 78.3, 52.9 and 67.5%, respectively, in determining high-grade astrocytoma. (2) Significant statistical differences were found in the rCBV,rCBF,ADC and rADC about the core and peritumoral of tumor between low and high grade astrocytoma , respectively(p<0.05), but the rMTT were not significant statistical differences(p>0.05). (3) The maximum youden index was chosen to determine the optimum thresholds of all the parameters in ROC analyses. Statistical analysis demonstrated a threshold value of 2.71 for rCBV of the core of tumor to provide sensitivity, specificity, PPV, and NPV of 85.0, 100, 100, and 78.0% and a threshold value of 0.670 for rCBV of the peritumoral of tumor to provide sensitivity, specificity, PPV, and NPV of 73.0, 71.0, 83.0, and 59.0%. In the same way, it demonstrated a threshold value of 1.45 for rCBF of the core of tumor to provide sensitivity, specificity, PPV, and NPV of 85.0, 71.0, 85.0, and 71.0% and a threshold value of 0.82 for rCBF of the peritumoral of tumor to provide sensitivity, specificity, PPV, and NPV of 69.0, 71.0, 82.0, and 56.0%. It demonstrated a threshold value of 0.82for ADC of the core of tumor to provide sensitivity and specificity of 82.0, and 86.0% and a threshold value of 1.11 for ADC of the peritumoral of tumor to provide sensitivity and specificity of 79.0, and 71.0%, respectively. (4) Sensitivity and specificity were 92.3% and 100% to combine the rCBV and rADC of the core of tumor with PWI and DWI, respectively.Conclusion Combining DSC PWI and DWI with conventional MR imaging increases the accuracy of pre-operative imaging grading of astrocytoma. The rCBV of the core of tumor is the most superior diagnostic performance. It apparently increases the sensitivity to combine the rCBV and rADC of the core of tumor with PWI and DWI in grading astrocytoma.