Hyperspectral imaging and FLAIR signal intensity: a step toward improved detection of nonenhancing glioma tissue.

Objective: Hyperspectral imaging (HSI) is an emerging new intraoperative, noninvasive, contrast agent-free, easy, and quick-to-use imaging modality. The present study aimed to correlate intraoperative HSI in glioma surgery with fluid attenuated inversion recovery (FLAIR) signal intensity.

Methods: The present prospective study performed intraoperative in vivo HSI with the TIVITA Tissue system to measure spectral signatures ranging from 500 to 1000 nm. The following tissue parameters were measured: oxygen saturation, perfusion, and hemoglobin, water, and fat content. The signal intensity of noncontrast-enhancing FLAIR regions was measured using ImageJ. The datasets were analyzed for correlations between HSI parameters and FLAIR signal intensity.

Results: Measurements were included from 15 patients. Histopathological analysis identified 10 cases of glioblastoma and 5 cases of astrocytoma, which were classified as WHO grade 2 (1 patient), WHO grade 3 (3 patients), and WHO grade 4 (1 patient). The area under the curve of the tissue water index (TWI) based on HSI for predicting increased FLAIR signal intensity was 0.70 (95% CI 0.40-0.99). TWI ≥ 0.416 had sensitivity and specificity of 75.0% and 85.7%, respectively. Six of 7 patients (85.7%) with TWI ≥ 0.416 had high FLAIR signal intensity, whereas 6 of 8 patients (75.0%) with TWI < 0.416 had low FLAIR signal intensity (p = 0.04).

Conclusions: The present investigation shows that the use of HSI to measure tissue water content correlates with the FLAIR signal intensity of nonenhancing glioma areas. Future studies evaluating the sensitivity and specificity of HSI to detect histopathologically confirmed nonenhancing glioma areas are needed.