Value of amide proton transfer imaging in correlation with histopathological grades of adult diffuse gliomas : comparison and incremental value with dynamic susceptibility contrast-enhanced MRI and diffusion weighted imaging

Abstract

Purpose

Amide proton transfer (APT), a subtype of chemical exchange saturation transfer, is a novel technique to detect concentration of endogenous peptide or protein without exogenous contrast agent administration. We investigated the difference in APT values according to histopathological grades, and compared the diagnostic value of APT with relative cerebral blood volume (rCBV) from dynamic susceptibility contrast-enhanced (DSC) MRI and apparent diffusion coefficient (ADC) from diffusion weighted imaging (DWI) for histopathological grades in adult diffuse gliomas. We also investigated the incremental value of APT over ADC and rCBV for discriminating high grade and low grade gliomas.

Material and Methods

The study cohort consisted of 39 adult patients with histopathologically proven diffuse glioma who underwent preoperative APT imaging, with 34 patients available for preoperative DSC MRI and DWI. Regions of interest were obtained from circles manually placed at the area with high signal in APT and rCBV map, and low signal in ADC map. APT signal was compared according to WHO grade or low vs high grade of glioma. Diagnostic ability to discriminate high grade glioma from low grade glioma were compared between APT, ADC, and rCBV by using Receiver operative characteristic (ROC) analysis, and incremental diagnostic value of APT over ADC and rCBV were assessed by using integrated discrimination index. Also, the correlation between APT values and Ki-67 labeling index (LI) was assessed by linear regression.

Results

The APT SI values were 0.82 ± 0.36% in grade II gliomas, 1.73 ± 0.86% in grade III, and 2.62 ± 0.78% in grade IV gliomas, which showed significant difference between grade II and III (p=0.018), III and IV (p = 0.010), as well as II and IV (p < 0.001). The diagnostic value to discriminate between high and low grade glioma was not significantly different between APT, ADC and rCBV, with area under the ROC curve (AUC) of 0.890, 0.917, and 0.947, respectively. (p > 0.05 for each comparison) Incremental diagnostic value of APT was significant over ADC (p = 0.003), and not significant over rCBV (p=0.066). APT signals were significantly correlated with Ki-67 LI. (p=0.001, R2 = 0.26)

Conclusion

APT imaging can be useful, and have incremental value over ADC for predicting the histopathological grades of adult diffuse gliomas. APT SI can be correlated with Ki-67 LI.