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Functional MRI for presurgical planning: Correlation between BOLD signal intensity and distance to the pathology
NemoImage
11, Number
5, 2000, Part 2 of 2 Parts ID
f hi@
DISORDERS
- NEUROLOGY
Functional MRI for presurgical planning: Correlation between BOLD signal intensity and distance to the pathology. Kirsten Mueschen*?$, Timo Krings*& Marcus H.T. Reingest, Michael Hoeller*$, Stephan G. Erberich*$, Veit Rohdet, Joachim M. Gilshachtf, Armin Thron*$ *Department of Neuroradiology *Department $Interdisciplinary
of Neuro.w;:ery
Center for Clinical Research - CNS, University Hospital, Technical University Aachen
Introduction: Functional MRI is an accurate method for the localization of sensorimotor cortex before resection of neoplastic tissue in this region. However, it has been shown in a single case that adjacent to a brain tumor, the BOLD functional MR activation during motor activation can be decreased (I). This could lead to false interpretation of fMR1 for presurgical planning. Our aim was to find out if the distance between a mass lesion and the site of functional activation affects the signal intensity observed by BOLD fMR1 in a large series of patients. Methods: 96 consecutive patients who were scheduled for neurosurgery were included in this study. In 53 patients 68 functional runs during alternating periods of rest and repetitive self-paced clenching of the hand to a fist were performed, in 43 patients 45 functional runs during repetitive finger to thumb pad opposition were acquired. Functional imaging was performed on a 1.5T Philips Gyroscan ACS NT using BOLD-contrast T2* weighted multislice multiecho EPI gradient echo sequences. Statistical analyses of task related hemodynamic changes were performed on a voxel by voxel basis using the non-parametric Kolmogorov Smirnov test. The percent increase in MR signal intensity was calculated for the parenchymal voxel within the primary motor cortex (Ml) that demonstrated highest statistical significance. The closest distance between the lesion border (including cerebral vasogenic edema) and the parenchymal activation was measured on hiah resolution 3D MRI. I 57 I Results: In 8 hand clenching and in 2 finger opposition runs severe motion artifacts prevented from interpretation of the data. These runs were excluded. There were no significant differences between finger opposition and hand clenching conceming the percent MR signal increase. In our population of patients, the distance (between lesion margin and point of activation) and percent MR signal intensity within the parenchymal activation was significantly positively correlated (Pearson Correlation coefficient r=0.65) (See Figure). Discussion: In normal subjects, there is a close correlation between neuronal activity and hemodynamic response observed by functional MRI (2). Therefore, there are two possible explanations for the decreased BOLD signal adjacent to brain tumors as observed in our study: One is still assuming intact correlation between neuronal activity and hemodynamic response (local pressure - injury or loss of adjacent neurons - lesser degree of neuronal activity - smaller increase in blood flow less T2* effect). The other hypothesis posits a mismatch between neuronal activity and observed hemodynamic changes. This mismatch might be explained by a reduced capability for autoregulation of pathological vasculature near the sensorimotor cortex with a subsequent diminished increase in cerebral blood flow following neuronal activation. Another explanation for the mismatch-hypothesis might be narrowing of draining vessels by tumor induced prersurc that leads to an increased egress of oxyhemoglobin (oxyHBi from the capillary bed and a subsequent relative decrease in the oxyHb concentration in the visualized venules and veins. This, in turn, would also lead to a diminished percent signal increase between rest and activation periods. Since fMR1 can demonstrate brain activity only indirectly via a hemodynamic filter, it can not further be differentiated which of these hypotheses are true. However, the lesser degree of activation near brain tumors has become obvious by this study and should be considered during presurgical planning. References (1) Holodny AI, et al., Decreased BOLD functional MR activation of the motor and sensory cortices adjacent to a glioblastoma multiforme: Implications for image-guided neurosurgery. AJNR Am J Neuroradiol 1999. 20: 609-612. (2) Krings T, et al. , Functional magnetic resonance imaging and transcranial magnetic stimulation: Complementary approaches in the evaluation of cortical motor function. Neurology 1997, 48: 1406-1416.
s151
11, Number
5, 2000, Part 2 of 2 Parts ID
f hi@
DISORDERS
- NEUROLOGY
Functional MRI for presurgical planning: Correlation between BOLD signal intensity and distance to the pathology. Kirsten Mueschen*?$, Timo Krings*& Marcus H.T. Reingest, Michael Hoeller*$, Stephan G. Erberich*$, Veit Rohdet, Joachim M. Gilshachtf, Armin Thron*$ *Department of Neuroradiology *Department $Interdisciplinary
of Neuro.w;:ery
Center for Clinical Research - CNS, University Hospital, Technical University Aachen
Introduction: Functional MRI is an accurate method for the localization of sensorimotor cortex before resection of neoplastic tissue in this region. However, it has been shown in a single case that adjacent to a brain tumor, the BOLD functional MR activation during motor activation can be decreased (I). This could lead to false interpretation of fMR1 for presurgical planning. Our aim was to find out if the distance between a mass lesion and the site of functional activation affects the signal intensity observed by BOLD fMR1 in a large series of patients. Methods: 96 consecutive patients who were scheduled for neurosurgery were included in this study. In 53 patients 68 functional runs during alternating periods of rest and repetitive self-paced clenching of the hand to a fist were performed, in 43 patients 45 functional runs during repetitive finger to thumb pad opposition were acquired. Functional imaging was performed on a 1.5T Philips Gyroscan ACS NT using BOLD-contrast T2* weighted multislice multiecho EPI gradient echo sequences. Statistical analyses of task related hemodynamic changes were performed on a voxel by voxel basis using the non-parametric Kolmogorov Smirnov test. The percent increase in MR signal intensity was calculated for the parenchymal voxel within the primary motor cortex (Ml) that demonstrated highest statistical significance. The closest distance between the lesion border (including cerebral vasogenic edema) and the parenchymal activation was measured on hiah resolution 3D MRI. I 57 I Results: In 8 hand clenching and in 2 finger opposition runs severe motion artifacts prevented from interpretation of the data. These runs were excluded. There were no significant differences between finger opposition and hand clenching conceming the percent MR signal increase. In our population of patients, the distance (between lesion margin and point of activation) and percent MR signal intensity within the parenchymal activation was significantly positively correlated (Pearson Correlation coefficient r=0.65) (See Figure). Discussion: In normal subjects, there is a close correlation between neuronal activity and hemodynamic response observed by functional MRI (2). Therefore, there are two possible explanations for the decreased BOLD signal adjacent to brain tumors as observed in our study: One is still assuming intact correlation between neuronal activity and hemodynamic response (local pressure - injury or loss of adjacent neurons - lesser degree of neuronal activity - smaller increase in blood flow less T2* effect). The other hypothesis posits a mismatch between neuronal activity and observed hemodynamic changes. This mismatch might be explained by a reduced capability for autoregulation of pathological vasculature near the sensorimotor cortex with a subsequent diminished increase in cerebral blood flow following neuronal activation. Another explanation for the mismatch-hypothesis might be narrowing of draining vessels by tumor induced prersurc that leads to an increased egress of oxyhemoglobin (oxyHBi from the capillary bed and a subsequent relative decrease in the oxyHb concentration in the visualized venules and veins. This, in turn, would also lead to a diminished percent signal increase between rest and activation periods. Since fMR1 can demonstrate brain activity only indirectly via a hemodynamic filter, it can not further be differentiated which of these hypotheses are true. However, the lesser degree of activation near brain tumors has become obvious by this study and should be considered during presurgical planning. References (1) Holodny AI, et al., Decreased BOLD functional MR activation of the motor and sensory cortices adjacent to a glioblastoma multiforme: Implications for image-guided neurosurgery. AJNR Am J Neuroradiol 1999. 20: 609-612. (2) Krings T, et al. , Functional magnetic resonance imaging and transcranial magnetic stimulation: Complementary approaches in the evaluation of cortical motor function. Neurology 1997, 48: 1406-1416.
s151