Artikel
Intraoperative optical and thermal imaging for visualisation of alterations in cortical hemodynamics and metabolism following somatosensory cortex activation
Intraoperative optische und thermische Bildgebung zur Visualisierung von Änderungen der kortikalen Hämodynamik und des Metabolismus bei der Aktivierung des somatosensorischen Kortex
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Veröffentlicht: | 25. Mai 2022 |
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Gliederung
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Objective: Intraoperative imaging techniques should support the surgeon in an effective tumor treatment strategy while preserving functional brain tissue. Previous studies proved that optical approaches such as Intraoperative Optical Imaging (IOI) and Intraoperative Thermal Imaging (ITI) could visualize functional brain areas by monitoring cortical hemodynamics or metabolism changes. This study provides a comparison of IOI and ITI and investigates the effect of different measuring principles.
Methods: Measurements were performed on 9 patients with cortical lesions undergoing craniotomy for tumor resection near the somatosensory cortex. Median nerve stimulation was performed for 9 minutes with alternating rest and stimulation periods. Meanwhile, IOI and ITI were acquired synchronously, and the localization of the somatosensory cortex was validated with phase reversal measurements. The results of both imaging techniques were compared for localization, extent, reliability, and thermal behavior of activation areas to assess detection performance.
Results: In all cases, both IOI and ITI were able to identify the primary sensory cortex (S1) in correspondence to the electrophysiological measurements. The percentage of true (TP) and false positive (FP) pixel results for IOI (TP: 25.0, FP: 9.9) and ITI (TP: 23.5, FP: 9.2) regarding the S1 area indicates a reliable performance for both. Detailed analysis revealed variations in position and size of the detected activation areas on the somatosensory cortex. The similarity was quantified using the dice coefficient resulting in 0.29 (IOI and S1), 0.26 (ITI and S1), and 0.28 (IOI and ITI). Differences in activation area localization are most likely due to the different physiological origin of the signal acquired with each measurement principle. Furthermore, we observed that pixel intensity values for IOI in rest periods are lower than for stimulation. The temperature behaves vice versa. That implies that temperature, as well as blood volume, decreases under electrical median nerve stimulation.
Conclusion: Both intraoperative imaging techniques reveal various advantages for detecting functional areas within the postcentral region. IOI can easily be integrated into a clinical routine due to its standard hardware setup, whereas the application of ITI is illumination-independent and suitable for further perfusion analysis. The combination of both principles in future analyses is well suited for investigating essential physiological processes of brain function.