A novel, reproducible, and objective method for volumetric magnetic resonance imaging assessment of enhancing glioblastoma

Abstract

Object: Robust methodology that allows objective, automated, and observer-independent measurements of brain tumor volume, especially after resection, is lacking. Thus, determination of tumor response and progression in neurooncology is unreliable. The objective of this study was to determine if a semi-automated volumetric method for quantifying enhancing tissue would perform with high reproducibility and low interobserver variability.

Methods: Fifty-seven MR images from 13 patients with glioblastoma were assessed using our method, by 2 neuroradiologists, 1 neurosurgeon, 1 neurosurgical resident, 1 nurse practitioner, and 1 medical student. The 2 neuroradiologists also performed traditional 1-dimensional (1D) and 2-dimensional (2D) measurements. Intraclass correlation coefficients (ICCs) assessed interobserver variability between measurements. Radiological response was determined using Response Evaluation Criteria In Solid Tumors (RECIST) guidelines and Macdonald criteria. Kappa statistics described interobserver variability of volumetric radiological response determinations.

Results: There was strong agreement for 1D (RECIST) and 2D (Macdonald) measurements between neuroradiologists (ICC = 0.42 and 0.61, respectively), but the agreement using the authors' novel automated approach was significantly stronger (ICC = 0.97). The volumetric method had the strongest agreement with regard to radiological response (κ = 0.96) when compared with 2D (κ = 0.54) or 1D (κ = 0.46) methods. Despite diverse levels of experience of the users of the volumetric method, measurements using the volumetric program remained remarkably consistent in all users (0.94).

Conclusions: Interobserver variability using this new semi-automated method is less than the variability with traditional methods of tumor measurement. This new method is objective, quick, and highly reproducible among operators with varying levels of expertise. This approach should be further evaluated as a potential standard for response assessment based on contrast enhancement in brain tumors.

Keywords: ICC = intraclass correlation coefficient; RANO = Response Assessment in Neuro-Oncology Working Group; RECIST = Response Evaluation Criteria In Solid Tumors; brain neoplasm; disease progression; glioma; magnetic resonance imaging; oncology; recurrence.

Figures

Figure 1

A) Demonstrates a T1 with contrast image on the left and on the right with our software the blue in the cavity demonstrates the enhancing tumor volume. The enhancing tumor is limited to the region of interest. B) The tumor enhancement is picked up from the T1 with contrast to our velocity method without including the non-enhancing mass. C) A cystic mass with a rim of enhancement is picked up by our method as a rim.

Figure 2

A) T1-weighted post-contrast axial image demonstrate the 1-D RECIST measurement would be “A” and 2-D Macdonald measurement would be “A * B” B). Our volumetric analysis demonstrates the tumor tissue (shown in green).