Multi-pool model-based amide proton transfer imaging in grading of gliomas and evaluating tumor proliferation: Comparison to apparent diffusion coefficient and magnetization transfer ratio asymmetry.

BACKGROUND

Magnetization transfer ratio asymmetry (MTRasym) is a semiquantitative analysis used for chemical exchange saturation transfer (CEST). Recently, we developed new parameters for CEST imaging using a multi-pool model (MPM) to produce quantitative results. This study evaluated the clinical significance of new parameters on MPM-based amide proton transfer (APT) imaging, the most common type of CEST, by assessing glioma grading and tumor proliferation compared with conventional apparent diffusion coefficient (ADC) and MTRasym.

METHODS

25 patients with gliomas underwent MRI. Two-dimensional axial APT imaging was conducted using a single-shot fast-spin echo acquisition at 3 T. Apparent diffusion coefficient (ADC), MTRasym (3.5 ppm), and MPM-based APT imaging parameters were calculated using a region-of-interest analysis. The Ki-67 index was obtained from tumor specimens. The parameters were compared among three glioma grades using one-way ANOVA. Pearson's correlation coefficient was used to assess correlations between the parameters. Receiver operating characteristic analysis determined the optimal cutoff values and assessed diagnostic performances for tumor grades.

RESULTS

Ki-67 index was significantly correlated with APT_T1, MTRasym, and ADC. APT_T1 significantly differed between grades II and III, grades III and IV, and grades II and IV. MTRasym and ADC significantly differed between grades II and III and grades II and IV. APT_T1 showed the largest area under the curve (0.94), followed by MTRasym, ADC, and APT_T2 in differentiating grade IV from other-grade gliomas.

CONCLUSION

APT_T1 showed the highest potential for differentiating grade IV glioma from other grades. Moreover, APT_T1 may be useful in assessing tumor proliferation and predicting tumor grade.