Synopsis

The purpose of this study is to evaluate the contribution of DWI and DSC-PWI in the peri-enhancing region for discriminating glioblastomas IDH genotypes. Further, the diagnostic value of this two MR techniques were compared with those in the enhancing portion. Features of conventional MRI, rADCmin-t, rADCmin-p, rCBVmax-t and rCBVmax-p were compared between IDH-m and IDH-w glioblastomas. IDH-mutated glioblastomas tended to present in frontal lobes and younger patients. Both rCBVmax-t and rCBVmax-p show significant difference between two subgroups, while rADCmin-t and rADCmin-p do not. The results showed that the accuracy of rCBVmax-p is higher than that of rCBVmax-t in the diagnosis of IDH-m glioblastomas. rCBVmax-p may have a better diagnostic value than rCBVmax-t in predicting IDH glioblastomas genotypes.

Introduction

Method

Based on the inclusion criteria (a. histopathologic diagnosis of GBMs, b. a known IDH status, c. pre-operative conventional MRI, DWI and DSC-PWI), 75 cases (10 cases of IDH-m GBMs and 65 cases of IDH-w GBMs) were enrolled. MR imaging examinations were performed on a 3T MR scanner (MAGNETOM Verio and Skyra, Siemens Healthcare, Erlangen, Germany). DWI was performed with a spin-echo echo-planar imaging sequence. The imaging parameters were as follows: TR/TE = 8200/102 ms, NEX = 2, FOV = 220 ×220, matrix = 192×192, b-values = 0 and 1000 s/mm2. ADC map was inline calculated by the MR imaging system. DSC-PWI was conducted with a gradient-recalled T2*-weighted echo-planar imaging sequence. The imaging parameters were as follows: TR/TE = 1000–1250/54 ms, flip angle = 35°, NEX = 1, FOV = 220×220, matrix = 128×128. Gadobenate dimeglumine (0.1 mmol/kg) was injected intravenously at a rate of 5 mL/s.

Tumors were assessed in terms of location, tumor size, single or multiple/satellite, contrast enhancement pattern, necrosis, cyst degeneration, hemorrhage, tumor border, edema, and mid-line shift.

For the evaluation of DWI data, ADC values were measured by placing regions of interests (ROIs) on the ADC maps. First, at least five non-overlapping ROIs (size > 10 mm2) were placed inside the tumor, and the minimum ADC values (ADCmin-t) were taken into consideration. The locations of selected ROIs were determined from the enhancing solid portion of the lesion (identified on the contrast-enhanced T1W image), avoiding hemorrhagic, cystic, necrotic parts, and large vessels. Second, 5 ROIs were placed inside the peri-enhancing region (defined as peritumoral non-enhancing region with FLAIR hyperintensity, <1cm), and the minimum ADC (ADCmin-p) was also recorded. Third, relative ADC (rADC) was determined as the ratio of the minimum ADC divided by the reference ADC in the contralateral normal-appearing white matter (CNWM). Both the relative ADCmin-t (rADCmin-t) and the relative ADCmin-p (rADCmin-p) were calculated.

Maps of CBV were obtained by applying a single-compartment model and an automated arterial input function. Measurement of rCBV was performed with the same method used for ADC measurement. The relative maximum rCBV in the enhancing portion (rCBVmax-t) and peri-enhancing area (rCBVmax-p) were recorded.

Results

The mean age of the IDH-w patients was significantly higher than that of the IDH-m patients (P = 0.008). Patients with IDH-m GBMs tended to present in the frontal lobes in this study. However, IDH mutational status did not correlate with other conventional MRI features.

The rADCmin-t, rADCmin-p, rCBVmax-t and rCBVmax-p ratios with respect to different IDH mutational status are given in Table 1, Figures 1 and 2. Both rCBVmax-t and rCBVmax-p were significantly higher in patients with IDH-w GBMs than those with IDH-m GBMs. However, neither rADCmin-t nor rADCmin-p showed a significant difference between IDH-m and IDH-w GBMs.

The results of ROC analysis are shown in Table 2. Both rCBVmax-t and rCBVmax-p ratios yielded good predictive power (AUC >0.80). In addition, the accuracy of rCBVmax-p ratios (94.67%) in the diagnosis of IDH-m GBMs was higher than that of rCBVmax-t ratios (74.67%).

Discussion and Conclusion

Acknowledgements

References

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