MRI- and PET-Guided Biopsy
In the management of brainstem lesions, the place of stereotactic biopsy sampling remains debatable. The authors compared the results of magnetic resonance (MR) imaging, positron emission tomography (PET), and histological findings obtained in 30 patients who underwent an MR image- and PET-guided stereotactic biopsy procedure for a brainstem mass lesion.
Between July 1991 and December 1998, 30 patients harboring a brainstem mass lesion underwent a stereotactic procedure in which combined MR imaging and PET guidance was used. Positron emission tomography scanning was performed using [F]-fluorodeoxyglucose in 16 patients, methionine in two patients, and with both tracers in 12 patients. Definite diagnosis was established on histological examination of the biopsy samples. Interpretation of MR imaging findings only or PET findings only were in agreement with the histological diagnosis in 63% and 73% of cases, respectively. Magnetic resonance imaging and PET findings were concordant in 19 of the 30 cases; in those cases, imaging data correlated with histological findings in 79%. In seven patients who underwent one PET-defined and one MR imaging-defined trajectory, at histological examination the PET-guided samples were more representative of the tumor's nature and grade than the MR imaging-guided samples in four cases (57%). In 18 patients PET scanning was used to define a biopsy target and provided a diagnostic yield in 100% of the cases.
Although the use of combined PET and MR imaging improves radiological interpretation of a mass lesion in the brainstem, it does not accurately replace histological diagnosis that is provided by a stereotactically obtained biopsy sample. Combined information provided by MR imaging and PET in stereotactic conditions improves the accuracy of targeting and the diagnostic yield of the stereotactically biopsy sample; an MR imaging- and PET-guided stereotactic biopsy procedure is a safe and efficient modality for the management of mass lesions of the brainstem.
The management of brainstem mass lesions remains controversial; particularly when the lesion cannot be removed and is of an infiltrating nature, the benefit of a stereotactic procedure is still debatable. One objection to performing a brainstem stereotactic biopsy procedure is that it may not be reliable because the tumor may be heterogeneous. Moreover, this heterogeneity often necessitates multiple sampling, which may be dangerous in the brainstem. Some authors also contend that obtaining histological diagnosis of brainstem tumors by a biopsy procedure is not necessary in most cases because of the effectiveness of modern cerebral imaging modalities, especially MR imaging. In that respect, PET scanning may also be of interest, as this imaging technique provides independent metabolic information that may be helpful in determining the nature and aggressiveness of brain tumors. However, for some authors, obtaining a stereotactic biopsy sample of brainstem mass lesions remains the best diagnostic procedure because a presumptive diagnosis based on MR imaging findings alone may lead to inaccurate diagnosis and, more importantly, erroneous treatment.
In several recent studies the authors have encouraged the use of PET scanning during stereotactic brain biopsy procedures to increase reliability of sampling by optimizing target selection. Since 1991, we have routinely incorporated PET in our planning of stereotactic biopsy sampling of cerebral tumors. To determine the additional value of PET we evaluated the use of combined PET/MR imaging in 30 patients in whom stereotactic biopsy samples of a brainstem lesions were obtained.
In the management of brainstem lesions, the place of stereotactic biopsy sampling remains debatable. The authors compared the results of magnetic resonance (MR) imaging, positron emission tomography (PET), and histological findings obtained in 30 patients who underwent an MR image- and PET-guided stereotactic biopsy procedure for a brainstem mass lesion.
Between July 1991 and December 1998, 30 patients harboring a brainstem mass lesion underwent a stereotactic procedure in which combined MR imaging and PET guidance was used. Positron emission tomography scanning was performed using [F]-fluorodeoxyglucose in 16 patients, methionine in two patients, and with both tracers in 12 patients. Definite diagnosis was established on histological examination of the biopsy samples. Interpretation of MR imaging findings only or PET findings only were in agreement with the histological diagnosis in 63% and 73% of cases, respectively. Magnetic resonance imaging and PET findings were concordant in 19 of the 30 cases; in those cases, imaging data correlated with histological findings in 79%. In seven patients who underwent one PET-defined and one MR imaging-defined trajectory, at histological examination the PET-guided samples were more representative of the tumor's nature and grade than the MR imaging-guided samples in four cases (57%). In 18 patients PET scanning was used to define a biopsy target and provided a diagnostic yield in 100% of the cases.
Although the use of combined PET and MR imaging improves radiological interpretation of a mass lesion in the brainstem, it does not accurately replace histological diagnosis that is provided by a stereotactically obtained biopsy sample. Combined information provided by MR imaging and PET in stereotactic conditions improves the accuracy of targeting and the diagnostic yield of the stereotactically biopsy sample; an MR imaging- and PET-guided stereotactic biopsy procedure is a safe and efficient modality for the management of mass lesions of the brainstem.
The management of brainstem mass lesions remains controversial; particularly when the lesion cannot be removed and is of an infiltrating nature, the benefit of a stereotactic procedure is still debatable. One objection to performing a brainstem stereotactic biopsy procedure is that it may not be reliable because the tumor may be heterogeneous. Moreover, this heterogeneity often necessitates multiple sampling, which may be dangerous in the brainstem. Some authors also contend that obtaining histological diagnosis of brainstem tumors by a biopsy procedure is not necessary in most cases because of the effectiveness of modern cerebral imaging modalities, especially MR imaging. In that respect, PET scanning may also be of interest, as this imaging technique provides independent metabolic information that may be helpful in determining the nature and aggressiveness of brain tumors. However, for some authors, obtaining a stereotactic biopsy sample of brainstem mass lesions remains the best diagnostic procedure because a presumptive diagnosis based on MR imaging findings alone may lead to inaccurate diagnosis and, more importantly, erroneous treatment.
In several recent studies the authors have encouraged the use of PET scanning during stereotactic brain biopsy procedures to increase reliability of sampling by optimizing target selection. Since 1991, we have routinely incorporated PET in our planning of stereotactic biopsy sampling of cerebral tumors. To determine the additional value of PET we evaluated the use of combined PET/MR imaging in 30 patients in whom stereotactic biopsy samples of a brainstem lesions were obtained.
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