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Factors related to the magnitude of T2* MR signal changes during functional imaging
T Krings1, M H T Reinges, K Willmes
1Department of Neuroradiology and Interdisciplinary Centre for Clinical Research - Central Nervous System, University Hospital of the Technical University Aachen, Pauwelsstrasse 30, 52057 Aachen, Germany. tkrings@izkf.rwth-aachen.de
Abstract:
Our aim was to determine whether age, sex, the degree of weakness, anticonvulsants, the histology of the underlying lesion(s), the presence of oedema or the distance of the lesion from the motor region have an impact on the blood oxygenation level-dependent (BOLD) signal strength and therefore on the validity of functional MRI (fMRI). We studied 98 patients with masses near the central region imaged for surgical planning at 1.5 tesla, employing a BOLD sequence during a motor task. We calculated percentage signal change in the primary motor cortex between rest and activation and carried out multiple linear regression to examine the impact of the above factors on signal strength. Using a stepwise analysis strategy, the distance of the lesion from the motor region had the strongest influence (r=0.653, P<0.001). The factor with largest uncorrelated additional impact on signal change was the presence of oedema. Both predictors together formed a highly significant multiple r=0.739 ( P<0.001). No other predictive factor was identified (all P>0.20). Disturbances of cerebral blood flow and metabolism induced by the tumour were presumed to be the causes of a decrease in signal in the adjacent cortex.
Insights
Lesion proximity and edema significantly impact functional MRI (fMRI) blood oxygenation level-dependent (BOLD) signal strength, affecting surgical planning validity. These factors are crucial for interpreting fMRI results in patients with brain tumors.
Area of Science:
- Neuroimaging
- Neurosurgery
- Radiology
Background:
- Functional MRI (fMRI) is vital for surgical planning near eloquent brain regions.
- Blood oxygenation level-dependent (BOLD) signal strength can be affected by various patient and lesion characteristics.
- Understanding factors influencing BOLD signal is critical for accurate fMRI interpretation.
Purpose of the Study:
- To investigate the impact of patient and lesion factors on BOLD signal strength in fMRI.
- To determine which factors influence the reliability of fMRI for surgical planning in patients with brain masses.
Main Methods:
- Studied 98 patients with central region masses undergoing fMRI for surgical planning.
- Utilized a 1.5 tesla BOLD sequence during a motor task.
- Employed multiple linear regression and stepwise analysis to assess signal change predictors.
Main Results:
- Lesion distance from the motor region was the strongest predictor of BOLD signal strength (r=0.653, P<0.001).
- Presence of edema had the largest uncorrelated additional impact on signal change.
- Distance and edema combined significantly predicted signal change (r=0.739, P<0.001); no other factors were significant.
Conclusions:
- Tumor-induced disturbances in cerebral blood flow and metabolism likely decrease BOLD signal in adjacent cortex.
- Lesion proximity and edema are key determinants of fMRI BOLD signal validity for surgical planning.
- These findings highlight the importance of considering lesion characteristics when interpreting fMRI data.