Intraoperative MR Imaging and 3D-Navigated Ultrasonography
Intraoperative MR Imaging and 3D-Navigated Ultrasonography
Object. The authors undertook a study to compare two intraoperative imaging modalities, low-field magnetic resonance (MR) imaging and a prototype of a three-dimensional (3D)-navigated ultrasonography in terms of imaging quality in lesion detection and intraoperative resection control.
Methods. Low-field MR imaging was used for intraoperative resection control and update of navigational data in 101 patients with supratentorial gliomas. Thirty-five patients with different lesions underwent surgery in which the prototype of a 3D-navigated ultrasonography system was used. A prospective comparative study of both intraoperative imaging modalities was initiated with the first seven cases presented here.
In 35 patients (70%) in whom ultrasonography was performed, accurate tumor delineation was demonstrated prior to tumor resection. In the remaining 30% comparison of preoperative MR imaging data and ultrasonography data allowed sufficient anatomical localization to be achieved. Detection of metastases and high-grade gliomas and intra-operative delineation of tumor remnants were comparable between both imaging modalities. In one case of a low-grade glioma better visibility was achieved with ultrasonography. However, intraoperative findings after resection were still difficult to interpret with ultrasonography alone most likely due to the beginning of a learning curve.
Conclusions. Based on these preliminary results, intraoperative MR imaging remains superior to intraoperative ultrasonography in terms of resection control in glioma surgery. Nevertheless, the different features (different planes of slices, any-plane slicing, and creation of a 3D volume and matching of images) of this new ultrasonography system make this tool a very attractive alternative. The intended study of both imaging modalities will hopefully allow a comparison regarding sensitivity and specificity of intraoperative tumor remnant detection, as well as cost effectiveness.
Modern imaging technologies have a major impact on spinal and intracranial neurosurgery. Better visualization by the operating microscope has markedly enhanced intra-operative handling and patient safety. Endoscopic-assisted neurosurgery enables the surgeon to look "around the corner" into an internal meatus or around a brain vessel to ensure that a clip is correctly placed in aneurysm surgery. In the past decade, computer-assisted image-guided surgery (neuronavigation) has been developed to assist neurosurgeons in performing surgery more safely, efficaciously, and cost effectively. Neuronavigation allows the neurosurgeon to localize the lesion more accurately, to determine the lesion size, and to choose a safe surgical corridor by which to approach the lesion. Currently available systems include frame-based or frameless systems that are based on different localizing techniques as passive pointers, LED-integrated optical pointers, or electromagnetic systems. All these image-guided systems, however, require imaging data (CT and MR imaging as well as, more recently, integrated functional MR imaging, positron emission tomography, and magnetoencephalography) acquired preoperatively. None of these systems can provide surgeons with information about intraoperative dynamic changes such as brain shift due to loss of cerebrospinal fluid, tumor debulking, or brain deformation caused by patient positioning. Knowledge of these changes is crucial in determining the amount of brain tumor to be resected, which is one of the key factors of post-operative progression-free interval and survival. Recently, intraoperative MR imaging was introduced by our group and others to solve some of the aforementioned problems. Although excellent in discriminating a lesion from the surrounding brain by the presence of tissue contrast, MR imaging is a bulky device, interfering with many surgical instruments, including the operating microscope and many electronic systems in the operating room. Therefore, other groups prefer to use intraoperative ultrasonography as a real-time monitoring device, which is easier to handle and less costly. However, many problems, such as correlating preoperative MR images with intraoperative ultrasonography images (that is, different data formats) and the evaluation of tumor remnants with high sensitivity and specificity, have not been solved yet. Based on our experience with 320 cases in which surgery was performed with the assistance of intraoperative MR imaging, we decided to undertake a prospective study to compare intraoperative MR imaging and high-end 3D ultrasonography. The first preliminary results are presented in this report.
Object. The authors undertook a study to compare two intraoperative imaging modalities, low-field magnetic resonance (MR) imaging and a prototype of a three-dimensional (3D)-navigated ultrasonography in terms of imaging quality in lesion detection and intraoperative resection control.
Methods. Low-field MR imaging was used for intraoperative resection control and update of navigational data in 101 patients with supratentorial gliomas. Thirty-five patients with different lesions underwent surgery in which the prototype of a 3D-navigated ultrasonography system was used. A prospective comparative study of both intraoperative imaging modalities was initiated with the first seven cases presented here.
In 35 patients (70%) in whom ultrasonography was performed, accurate tumor delineation was demonstrated prior to tumor resection. In the remaining 30% comparison of preoperative MR imaging data and ultrasonography data allowed sufficient anatomical localization to be achieved. Detection of metastases and high-grade gliomas and intra-operative delineation of tumor remnants were comparable between both imaging modalities. In one case of a low-grade glioma better visibility was achieved with ultrasonography. However, intraoperative findings after resection were still difficult to interpret with ultrasonography alone most likely due to the beginning of a learning curve.
Conclusions. Based on these preliminary results, intraoperative MR imaging remains superior to intraoperative ultrasonography in terms of resection control in glioma surgery. Nevertheless, the different features (different planes of slices, any-plane slicing, and creation of a 3D volume and matching of images) of this new ultrasonography system make this tool a very attractive alternative. The intended study of both imaging modalities will hopefully allow a comparison regarding sensitivity and specificity of intraoperative tumor remnant detection, as well as cost effectiveness.
Modern imaging technologies have a major impact on spinal and intracranial neurosurgery. Better visualization by the operating microscope has markedly enhanced intra-operative handling and patient safety. Endoscopic-assisted neurosurgery enables the surgeon to look "around the corner" into an internal meatus or around a brain vessel to ensure that a clip is correctly placed in aneurysm surgery. In the past decade, computer-assisted image-guided surgery (neuronavigation) has been developed to assist neurosurgeons in performing surgery more safely, efficaciously, and cost effectively. Neuronavigation allows the neurosurgeon to localize the lesion more accurately, to determine the lesion size, and to choose a safe surgical corridor by which to approach the lesion. Currently available systems include frame-based or frameless systems that are based on different localizing techniques as passive pointers, LED-integrated optical pointers, or electromagnetic systems. All these image-guided systems, however, require imaging data (CT and MR imaging as well as, more recently, integrated functional MR imaging, positron emission tomography, and magnetoencephalography) acquired preoperatively. None of these systems can provide surgeons with information about intraoperative dynamic changes such as brain shift due to loss of cerebrospinal fluid, tumor debulking, or brain deformation caused by patient positioning. Knowledge of these changes is crucial in determining the amount of brain tumor to be resected, which is one of the key factors of post-operative progression-free interval and survival. Recently, intraoperative MR imaging was introduced by our group and others to solve some of the aforementioned problems. Although excellent in discriminating a lesion from the surrounding brain by the presence of tissue contrast, MR imaging is a bulky device, interfering with many surgical instruments, including the operating microscope and many electronic systems in the operating room. Therefore, other groups prefer to use intraoperative ultrasonography as a real-time monitoring device, which is easier to handle and less costly. However, many problems, such as correlating preoperative MR images with intraoperative ultrasonography images (that is, different data formats) and the evaluation of tumor remnants with high sensitivity and specificity, have not been solved yet. Based on our experience with 320 cases in which surgery was performed with the assistance of intraoperative MR imaging, we decided to undertake a prospective study to compare intraoperative MR imaging and high-end 3D ultrasonography. The first preliminary results are presented in this report.
