Accuracy of Intra-Axial Brain Tumor Characterization in the Emergency MRI Reports: A Retrospective Human Performance Benchmarking Pilot Study

Abstract

Demand for emergency neuroimaging is increasing. Even magnetic resonance imaging (MRI) is often performed outside office hours, sometimes revealing more uncommon entities like brain tumors. The scientific literature studying artificial intelligence (AI) methods for classifying brain tumors on imaging is growing, but knowledge about the radiologist's performance on this task is surprisingly scarce. Our study aimed to tentatively fill this knowledge gap. We hypothesized that the radiologist could classify intra-axial brain tumors at the emergency department with clinically acceptable accuracy. We retrospectively examined emergency brain MRI reports from 2013 to 2021, the inclusion criteria being (1) emergency brain MRI, (2) no previously known intra-axial brain tumor, and (3) suspicion of an intra-axial brain tumor on emergency MRI report. The tumor type suggestion and the final clinical diagnosis were pooled into groups: (1) glial tumors, (2) metastasis, (3) lymphoma, and (4) other tumors. The final study sample included 150 patients, of which 108 had histopathological tumor type confirmation. Among the patients with histopathological tumor type confirmation, the accuracy of the MRI reports in classifying the tumor type was 0.86 for gliomas against other tumor types, 0.89 for metastases, and 0.99 for lymphomas. We found the result encouraging, given the prolific need for emergency imaging.

Keywords: brain lymphoma; brain metastasis; brain tumor; diagnostic accuracy; emergency radiology; glioma; magnetic resonance imaging; neuroradiology.

Figure 1

Symptoms described in the emergency MRI referral. All the symptoms mentioned in the MRI referrals as an indication for brain MRI were extracted and pooled. The symptoms in the study population were non-specific, similar to those of most neurological patients in the emergency departments. The most common were problems with motor function and speech.

Figure 2

(a) Patient 1, axial T2-weighted MRI, (b) Patient 1, axial gadolinium-enhanced T1-weighted spin-echo MRI, (c) Patient 2, axial T2-weighted MRI, (d) Patient 2, axial gadolinium-enhanced T1-weighted spin-echo MRI. Two patients with a histopathologically confirmed glioblastoma. Patient 1 (upper row) was initially suggested to have a solitary cerebral metastasis (asterisks), primarily because of the rapid appearance of the tumor (the previous MRI six months earlier was unremarkable) and because of the extensive edema surrounding the tumor (black arrowheads). Patient 1 underwent a thoracoabdominal CT scan to detect the primary tumor and other metastases. Patient 2 (lower row) was initially suggested of having a glioblastoma (asterisks) and the patient was immediately directed to the neurosurgeon without unnecessary steps. The diagnosis of glioblastoma was later confirmed histopathologically. Both tumors demonstrate a homogenous, probably necrotic center (asterisks) surrounded by a gadolinium-enhancing rim (white arrows). The enhancing rim is surrounded by a T2-hyperintense zone consisting of poorly delineated tumor infiltration and vasogenic edema, sometimes inseparable from each other with conventional clinical imaging. Brain metastasis often represents very similar MRI findings compared to glioblastomas.