Applying protein-based amide proton transfer MR imaging to distinguish solitary brain metastases from glioblastoma

Abstract

Objectives: To determine the utility of amide proton transfer-weighted (APTw) MR imaging in distinguishing solitary brain metastases (SBMs) from glioblastomas (GBMs).

Methods: Forty-five patients with SBMs and 43 patients with GBMs underwent conventional and APT-weighted sequences before clinical intervention. The APTw parameters and relative APTw (rAPTw) parameters in the tumour core and the peritumoral brain zone (PBZ) were obtained and compared between SBMs and GBMs. The receiver-operating characteristic (ROC) curve was used to assess the best parameter for distinguishing between the two groups.

Results: The APTw_max, APTw_min, APTw_mean, rAPTw_max, rAPTw_min or rAPTw_mean values in the tumour core were not significantly different between the SBM and GBM groups (P = 0.141, 0.361, 0.221, 0.305, 0.578 and 0.448, respectively). However, the APTw_max, APTw_min, APTw_mean, rAPTw_max, rAPTw_min or rAPTw_mean values in the PBZ were significantly lower in the SBM group than in the GBM group (P < 0.001). The APTw_min values had the highest area under the ROC curve 0.905 and accuracy 85.2% in discriminating between the two neoplasms.

Conclusion: As a noninvasive imaging method, APT-weighted MR imaging can be used to distinguish SBMs from GBMs.

Key points: • APTw values in the tumour core were not different between SBMs and GBMs. • APTw values in peritumoral brain zone were lower in SBMs than in GBMs. • The APTw _min was the best parameter to distinguish SBMs from GBMs.

Keywords: APT imaging; Brain; Glioblastoma; Magnetic resonance imaging; Solitary brain metastases.

Fig. 1

Example of the placement of ROIs. Five ROIs were placed in the Gd-enhancing tumor part (Black Circle), five ROIs were placed in the peritumoral T₂ hyper-intensity area (White Circle), and one ROI was placed in the contralateral normal-appearing white matter (Red Circle) based on the co-registered traditional images. The necrosis-related image artefact (white arrow) can also be seen.

Fig. 2

Results for a 54-year-old woman with solitary brain metastasis (white arrows). The primary tumor was lung adenocarcinoma. A–C, the tumor was located in the right parietal-occipital lobe with moderate peritumoral edema. It appears hypointense on T₁WI, hyperintense on T₂WI, and ring-like contrast-enhanced on Gd-T₁WI. D, an APTw image shows a relatively homogeneous hyperintense mass (tumor core, APT_Wmax=3.55%, APT_Wmin=2.87%, APT_Wmean=3.34%; peritumoral edema, APT_Wmax=1.72%, APT_Wmin=1.57%, APT_Wmean=1.63%; APT_WCNAWM= 0.74%). E, H&E-stained sections (×200) of the tumor core show many dense, aggregated cells with atypical nuclei arranged in glandular, nest and cord patterns. F, H&E-stained sections (×100) of the peritumoral edema show the degeneration of nerve cells and the proliferation of glial cells, but no tumor cells are found.

Fig. 3

Results for a 67-year-old man with glioblastoma. A–C, the tumor is located in the right occipital lobe with mild peritumoral edema. The tumor appears hypointense on the T₁WI, hyperintense on the T₂WI, and ring-like contrast-enhanced on the Gd-T₁WI. D, an APT_W image shows a heterogeneously hyperintense mass (tumor core: APT_Wmax=3.87%, APT_Wmin=2.96%, APT_Wmean=3.61%; peritumoral edema: APT_Wmax=2.09%, APT_Wmin=1.63%, APT_Wmean=1.89%; APT_WCNAWM =0.57%). E, H&E-stained sections (×200) of the tumor core show many multinucleated atypical tumor cells with relatively abundant cytoplasm. F, H&E-stained sections (×100) of the peritumoral edema show proliferating glial cells and a number of cells with atypical nuclei.

Fig. 4

Box-and-whisker plots. Thick horizontal line=mean, whiskers=±SD. APTw values in the SBM group are significantly lower than those in the GBM group (all P<0.001).