ABSTRACT Advantages of MR imaging for guidance of minimally invasive procedures include exception... more ABSTRACT Advantages of MR imaging for guidance of minimally invasive procedures include exceptional soft tissue contrast, intrinsic multiplanar imaging capability, and absence of exposure to ionizing radiation. Specialized imaging sequences are available and under development which can further enhance diagnosis and therapy. Flow-sensitive imaging techniques can be used to identify vascular structures. Temperature-sensitive imaging is possible which can provide interactive feedback prior to, during, and following the delivery of thermal energy. Functional MR imaging and dynamic contrast-enhanced MRI sequences can provide additional information for guidance in neurosurgical applications. Functional MR allows mapping of eloquent areas in the brain, so that these areas may be avoided during therapy. Dynamic contrast enhancement techniques can be useful for distinguishing active tumor from tumor necrosis caused by previous radiation therapy. An open-configuration 0.5T MRI system (GE Signa SP) developed at Brigham and Women's Hospital in collaboration with General Electric Medical Systems is described. Interactive navigation systems have been integrated into the MRI system. The imaging system is sited in an operating room environment, and used for image guided neurosurgical procedures (biopsies and tumor excision), as well as minimally invasive thermal therapies. Examples of MR imaging guidance, navigational techniques, and clinical applications are presented.
OBJECTIVE: Several novel sealing materials have been proposed as an adjunct to sutured dural clos... more OBJECTIVE: Several novel sealing materials have been proposed as an adjunct to sutured dural closure to help insure watertight closure, thus diminishing the risk of pseudomeningocele formation. This evaluation was undertaken to clarify the in vivo magnetic resonance imaging (MRI) and computed tomographic (CT) scan characteristics of one such sealant, which has a high water content, permitting similar imaging characteristics to pseudomeningoceles and inflammatory collections. METHODS: After a craniotomy in two canine subjects, we sprayed a novel, watersoluble, self-polymerizing, absorbable, hydrogel sealant onto the dura and the bone flap was replaced. After recovery, both animals underwent MRI and CT scans after 3 days and again at 2, 4, 6, 8, and 10 weeks after the craniotomy. The appearance of the gel at each timepoint was characterized and compared with the macroscopic and microscopic findings obtained 14 weeks after implantation. RESULTS: Both animals remained neurologically intact. Hydrogel sealant was readily apparent with all imaging techniques through Week 6. Diagnostic distinction from inflammatory collections and pseudomeningoceles was possible with MRI, using inversion recovery and contrast-enhanced sequences; such distinctions were occasionally challenging with a contrast-enhanced CT scan. Temporal absorption of the gel and subsequent closure of the remaining void was documented. Histopathology showed minimal changes, and excellent tissue compatibility of the gel was noted. CONCLUSION: The hydrogel sealant can be observed with cross sectional imaging and can be distinguished from cerebrospinal fluid using a CT scan, complemented by an occasional MRI scan. In addition, complete absorption of the hydrogel, with closure of the remaining void was noted. Histological examination found an unremarkable response with no neurotoxicity or space-filling defect.
To review preliminary experience with an open-bore magnetic resonance (MR) imaging system for gui... more To review preliminary experience with an open-bore magnetic resonance (MR) imaging system for guidance in intracranial surgical procedures. A vertically oriented, open-configuration 0.5-T MR imager was housed in a sterile procedure room. Receive and transmit surface coils were wrapped around the patient's head, and images were displayed on monitors mounted in the gap of the magnet and visible to surgeons. During 2 years, 200 intracranial procedures were performed. There were 111 craniotomies, 68 biopsies, 12 intracranial cyst evaluations, four subdural drainages, and five transsphenoidal pituitary resections performed with the intraoperative MR unit. In each case, the intraoperative MR system yielded satisfactory results by allowing the radiologist to guide surgeons toward lesions and to assist in treatment. In two patients, hyperacute hemorrhage was noted and removed. The duration of the procedure and the complication rate were similar to those of conventional surgery. Intraoperative MR imaging was successfully implemented for a variety of intracranial procedures and provided continuous visual feedback, which can be helpful in all stages of neurosurgical intervention without affecting the duration of the procedure or the incidence of complications. This system has potential advantages over conventional frame-based and frameless stereotactic procedures with respect to the safety and effectiveness of neurosurgical interventions.
With the introduction of higher field magnets, we are now able to achieve spatial resolutions of ... more With the introduction of higher field magnets, we are now able to achieve spatial resolutions of such superb quality that even the most exquisite details of the brain anatomy can be visualized in magnetic resonance imaging (MRI). With intraoperative image updates, brain deformations throughout the course of surgery are detected in near-real time and the resection progress is readily monitored. This enables accurate neuronavigation. Intraoperative MRI is approaching the point at which it will be used not only to localize, target, and guide resection of brain tumors and other intracranial lesions, but also to provide a comprehensive picture of the surrounding functional anatomy.
In many clinical procedures involving needle insertion, such as cryoablation, accurate navigation... more In many clinical procedures involving needle insertion, such as cryoablation, accurate navigation of the needle to the desired target is of paramount importance to optimize the treatment and minimize the damage to the neighboring anatomy. However, the force interaction between the needle and tissue may lead to needle deflection, resulting in considerable error in the intraoperative tracking of the needle tip. In this paper, we have proposed a Kalman filter-based formulation to fuse two sensor dataoptical sensor at the base and magnetic resonance (MR) gradient-field driven electromagnetic (EM) sensor placed 10 cm from the needle tipto estimate the needle deflection online. Angular springs model based tip estimations and EM based estimation without model are used to form the measurement vector in the Kalman filter. Static tip bending experiments show that the fusion method can reduce the error of the tip estimation by from 29.23 mm to 3.15 mm and from 39.96 mm to 6.90 mm at the MRI isocenter and 650 mm from the isocenter respectively.
Medical Imaging 2017: Image-Guided Procedures, Robotic Interventions, and Modeling, 2017
MRI-guided needle intervention for cryoablation is a promising way to relieve the pain and treat ... more MRI-guided needle intervention for cryoablation is a promising way to relieve the pain and treat the cancer. However, the limited size of MRI bore makes it impossible for clinicians to perform the operation in the bore. The patients had to be moved into the bore for scanning to verify the position of the needle’s tip and out for adjusting the needle’s trajectory. Real-time needle tracking and shown in MR images is of importance for clinicians to perform the operation more efficiently. In this paper, we have instrumented the cryotherapy needle with a MRI-safe electromagnetic (EM) sensor and optical sensor to measure the needle’s position and orientation. To overcome the limitation of line-of-sight for optical sensor and the poor dynamic performance of the EM sensor, Kalman filter based data fusion is developed. Further, we developed a navigation system in open-source software, 3D Slicer, to provide accurate visualization of the needle and the surrounding anatomy. Experiment of simulation the needle intervention at the entrance was performed with a realistic spine phantom to quantify the accuracy of the navigation using the retrospective analysis method. Eleven trials of needle insertion were performed independently. The target accuracy with the navigation using only EM sensor, only optical sensor and data fusion are 2.27 ±1.60 mm, 4.11 ± 1.77 mm and 1.91 − 1.10 mm, respectively.
D. F. Kacher, S. P. DiMaio, E. Samset, B. Fetics, E. Nevo, F. A. Jolesz Radiology, Brigham and Wo... more D. F. Kacher, S. P. DiMaio, E. Samset, B. Fetics, E. Nevo, F. A. Jolesz Radiology, Brigham and Women's Hospital, Boston, MA, United States, Radiology, Brigham and Women's Hospital, Boston, M, United States, Radiology, Brigham and Women's Hospital, Boston, MA, United Arab Emirates, Robin Medical, Baltimore, MD, United States MRI-guidance has increasing potential to augment or replace conventional X-ray fluoroscopy in cardiac, peripheral-, and neurovascular interventions [1]. Catheter tracking with MRI, using frequency encoding, to localize the NMR signal near small RF coils has been proven feasible [2]. Recently, an electromagnetic (EM) tracking system that utilizes the scanners gradients has emerged [3]. Coupling such tracking systems with near real-time imaging [4] and 3D visualization of previously acquired data sets [5] yields a powerful tool for the interventionalist. EM tracking has long been used in the cath lab setting for catheter tracking. The advantage of EM t...
Objective-The usefulness of neurosurgical navigation with current visualizations is seriously com... more Objective-The usefulness of neurosurgical navigation with current visualizations is seriously compromised by brain shift, which inevitably occurs during the course of the operation, significantly degrading the precise alignment between the preoperative MR data and the intraoperative shape of the brain. Our objectives were (i) to evaluate the feasibility of non-rigid registration that compensates for the brain deformations within the time constraints imposed by neurosurgery, and (ii) create augmented reality visualizations of critical structural and functional brain regions during neurosurgery using pre-operatively acquired fMRI and DT-MRI. Materials and Methods-Eleven consecutive patients with supratentorial gliomas were included in our study. All underwent surgery at our intra-operative MR imaging-guided therapy facility and have tumors in eloquent brain areas (e.g. precentral gyrus and cortico-spinal tract). Functional MRI and DT-MRI, together with MPRAGE and T2w structural MRI were acquired at 3T prior to surgery. SPGR and T2w images were acquired with a 0.5T magnet during each procedure. Quantitative assessment of the alignment accuracy was carried out and compared with current state-of the-art systems based only on rigid-registration. Results-Alignment between preoperative and intra-operative datasets was successfully carried out during surgery for all patients. Overall, the mean residual displacement remaining after nonrigid registration was 1.82 mm. There is a statistically significant improvement in alignment accuracy utilizing our non-rigid registration in comparison to the currently used technology (p<0.001). Conclusions-We were able to achieve intra-operative rigid and non-rigid registration of (1) pre-operative structural MRI with intra-operative T1w MRI; (2) pre-operative FMRI with intraoperative T1w MRI, and (3) pre-operative DT-MRI with intra-operative T1w MRI. The registration algorithms as implemented were sufficiently robust and rapid to meet the hard realtime constraints of intra-operative surgical decision making. The validation experiments demonstrate that we can accurately compensate for the deformation of the brain and thus can construct an augmented reality visualization to aid the surgeon.
Iwu (Magnetic Resonance Imagining) is a powerful medical diagnostic tool. Its value would be grea... more Iwu (Magnetic Resonance Imagining) is a powerful medical diagnostic tool. Its value would be greatly increased if it was possible to physically manipulate objects within the MRI during imaging. However, the extraordinarily strong magnetic fields used by the MRI make conventional-electromagnetic components, such as actuators and sensors, unusable. Io this paper, it is shown that devices constructed using binary polymer based actuators, called Electrostrictive Polymer Actuators (EPAM) are able to function effectively within the MRI without degrading its imaging performance. These actuators eliminate the need for conventional electromagnetic actuators and their associated electronics. The binary nature of the actuators eliminates the need for feedback sensors to control the devices motion. The basic concept called Digital Mechatronics is briefly summarized in this paper. Its application to a reconfigurable MRI surface- imaging coil (RMIC) is also presented. Experimental results are presented that show the EPAM RMIC is completely compatible in the MRI and can be used to enhance the diagnostic capabilities of MFU. The paper also suggests other applications of binary EPAM based actuators for use in MRI systems.
increased brain size results from an increase in brain growth or failure of the post-natal proces... more increased brain size results from an increase in brain growth or failure of the post-natal processes of axonal and/or synaptic pruning. In attempt to shed light on the pathophysiology of this finding the present study was designed to reexamine the brain size in a sample of high functioning autistics (HFA). We hypothesized that HFA would show an increase in cerebral volume (CV) when adjusting for intra-cranial volume (ICV) in comparison with age and IQ matched controls. A deficit in postnatal pruning would predict a larger brain relative to ICV. On the other hand, a normal pruning would predict that relative to ICV, the brain size would not differ from healthy controls. MRI scans from 16 HFA and 19 male volunteer comparison subjects were obtained and the volumes of the following structures were measured using NIH-IMAGE: gray and white matter, third, fourth, and lateral ventricles, in addition to the ICV and CV. Mean CV and third ventricle volumes in the autistic subjects were significantly greater than the control group when adjusted for ICV. No other significant results were found. Our finding of increased brain size in autism is consistent with previous reports in the literature. However, additional neuro-imaging and more importantly neuropathologic studies are needed to examine whether or not abnormalities in the pruning process underlie this finding.
INTRODUCTION: Functional MRI is increasingly used as an adjunct to neurosurgical planning. Our la... more INTRODUCTION: Functional MRI is increasingly used as an adjunct to neurosurgical planning. Our laboratory has developed techniques for 3-D reconstruction of morphologic and angiographic MR images. The 3-0 model may be registered with functional information derived from multiple modalities (fMRI. SPEeT. and intraoperative cortical mapping). We present two illustrative cases in which preoperative fMRI data were integrated with real-time intraoperative imagingtechniques for surgicalguidance.
BACKGROUND AND PURPOSE: The cause of posterior reversible encephalopathy syndrome (PRES) is unkno... more BACKGROUND AND PURPOSE: The cause of posterior reversible encephalopathy syndrome (PRES) is unknown. Two primary hypotheses exist: 1) hypertension exceeding auto-regulatory limits leading to forced hyper-perfusion and 2) vasoconstriction and hypo-perfusion leading to ischemia with resultant edema. The purpose of this study was to evaluate the catheter angiography (CA), MR angiography (MRA), and MR perfusion (MRP) features in PRES in order to render further insight into its mechanism of origin. MATERIALS AND METHODS: In 47 patients with PRES, 9 CAs and 43 MRAs were evaluated for evidence of vasculopathy (vasoconstriction and vasodilation), and 15 MRP studies were evaluated for altered relative cerebral blood volume (rCBV) in PRES lesions and regions. Visualization of vessels on MRA and toxicity blood pressures were compared with the extent of hemispheric vasogenic edema. RESULTS: Vasculopathy was present in 8 of 9 patients on CA (direct correlation to MRA in 3/6 patients). At MRA, moderate to severe vessel irregularity consistent with vasoconstriction and vasodilation was present in 30 of 43 patients and vessel pruning or irregularity in 7 patients, with follow-up MRA demonstrating reversal of vasoconstriction or vasodilation in 9 of 11 patients. Vasogenic edema was less in patients with hypertension compared with patients who were normotensive. Preserved normal length of the posterior cerebral artery (PCA) was commonly seen in patients with severe hypertension despite diffuse or focal vasoconstriction or vasodilation. In these patients, lengthier visualization of the distal PCA correlated with a lower grade of hemispheric edema (P ϭ .002). Cortical rCBV was significantly reduced in 51 of 59 PRES lesions and regions compared with a healthy reference cortex (average 61% of reference cortex) with mild decrease in the remainder. CONCLUSION: Vasculopathy was a common finding on CA and MRA in our patients with PRES, and MRP demonstrated reduced cortical rCBV in PRES lesions. Vasogenic edema was reduced in patients with hypertension, and superior distal PCA visualization correlated with reduced hemispheric edema in patients with PRES and severe hypertension.
Electrocardiographic (ECG) criteria for determining left ventricular mass in young healthy men; d... more Electrocardiographic (ECG) criteria for determining left ventricular mass in young healthy men; data from the LARGE Heart study
... MA) with a 128 element linear array transducer was connected to an interface box within the m... more ... MA) with a 128 element linear array transducer was connected to an interface box within the magnet room and the box was connected to a laptop computer outside the room ... MR images of a spherical phantom in a standard head coil were acquired with US probe inside the coil. ...
▪ The goal of the Image Guided Therapy Program, as the name implies, is to develop the use of i... more ▪ The goal of the Image Guided Therapy Program, as the name implies, is to develop the use of imaging to guide minimally invasive therapy. The program combines interventional and intraoperative magnetic resonance imaging (MRI) with high-performance computing and novel therapeutic devices. In clinical practice the multidisciplinary program provides for the investigation of a wide range of interventional and surgical procedures. The Signa SP 0.5 T superconducting MRI system (GE Medical Systems, Milwaukee, WI) has a 56-cm-wide vertical gap, allowing access to the patient and permitting the execution of interactive MRI-guided procedures. This system is integrated with an optical tracking system and utilizes flexible surface coils and MRI-compatible displays to facilitate procedures. Images are obtained with routine pulse sequences. Nearly real-time imaging, with fast gradient-recalled echo sequences, may be acquired at a rate of one image every 1.5 s with interactive image plane selec...
ABSTRACT Advantages of MR imaging for guidance of minimally invasive procedures include exception... more ABSTRACT Advantages of MR imaging for guidance of minimally invasive procedures include exceptional soft tissue contrast, intrinsic multiplanar imaging capability, and absence of exposure to ionizing radiation. Specialized imaging sequences are available and under development which can further enhance diagnosis and therapy. Flow-sensitive imaging techniques can be used to identify vascular structures. Temperature-sensitive imaging is possible which can provide interactive feedback prior to, during, and following the delivery of thermal energy. Functional MR imaging and dynamic contrast-enhanced MRI sequences can provide additional information for guidance in neurosurgical applications. Functional MR allows mapping of eloquent areas in the brain, so that these areas may be avoided during therapy. Dynamic contrast enhancement techniques can be useful for distinguishing active tumor from tumor necrosis caused by previous radiation therapy. An open-configuration 0.5T MRI system (GE Signa SP) developed at Brigham and Women&#39;s Hospital in collaboration with General Electric Medical Systems is described. Interactive navigation systems have been integrated into the MRI system. The imaging system is sited in an operating room environment, and used for image guided neurosurgical procedures (biopsies and tumor excision), as well as minimally invasive thermal therapies. Examples of MR imaging guidance, navigational techniques, and clinical applications are presented.
OBJECTIVE: Several novel sealing materials have been proposed as an adjunct to sutured dural clos... more OBJECTIVE: Several novel sealing materials have been proposed as an adjunct to sutured dural closure to help insure watertight closure, thus diminishing the risk of pseudomeningocele formation. This evaluation was undertaken to clarify the in vivo magnetic resonance imaging (MRI) and computed tomographic (CT) scan characteristics of one such sealant, which has a high water content, permitting similar imaging characteristics to pseudomeningoceles and inflammatory collections. METHODS: After a craniotomy in two canine subjects, we sprayed a novel, watersoluble, self-polymerizing, absorbable, hydrogel sealant onto the dura and the bone flap was replaced. After recovery, both animals underwent MRI and CT scans after 3 days and again at 2, 4, 6, 8, and 10 weeks after the craniotomy. The appearance of the gel at each timepoint was characterized and compared with the macroscopic and microscopic findings obtained 14 weeks after implantation. RESULTS: Both animals remained neurologically intact. Hydrogel sealant was readily apparent with all imaging techniques through Week 6. Diagnostic distinction from inflammatory collections and pseudomeningoceles was possible with MRI, using inversion recovery and contrast-enhanced sequences; such distinctions were occasionally challenging with a contrast-enhanced CT scan. Temporal absorption of the gel and subsequent closure of the remaining void was documented. Histopathology showed minimal changes, and excellent tissue compatibility of the gel was noted. CONCLUSION: The hydrogel sealant can be observed with cross sectional imaging and can be distinguished from cerebrospinal fluid using a CT scan, complemented by an occasional MRI scan. In addition, complete absorption of the hydrogel, with closure of the remaining void was noted. Histological examination found an unremarkable response with no neurotoxicity or space-filling defect.
To review preliminary experience with an open-bore magnetic resonance (MR) imaging system for gui... more To review preliminary experience with an open-bore magnetic resonance (MR) imaging system for guidance in intracranial surgical procedures. A vertically oriented, open-configuration 0.5-T MR imager was housed in a sterile procedure room. Receive and transmit surface coils were wrapped around the patient&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s head, and images were displayed on monitors mounted in the gap of the magnet and visible to surgeons. During 2 years, 200 intracranial procedures were performed. There were 111 craniotomies, 68 biopsies, 12 intracranial cyst evaluations, four subdural drainages, and five transsphenoidal pituitary resections performed with the intraoperative MR unit. In each case, the intraoperative MR system yielded satisfactory results by allowing the radiologist to guide surgeons toward lesions and to assist in treatment. In two patients, hyperacute hemorrhage was noted and removed. The duration of the procedure and the complication rate were similar to those of conventional surgery. Intraoperative MR imaging was successfully implemented for a variety of intracranial procedures and provided continuous visual feedback, which can be helpful in all stages of neurosurgical intervention without affecting the duration of the procedure or the incidence of complications. This system has potential advantages over conventional frame-based and frameless stereotactic procedures with respect to the safety and effectiveness of neurosurgical interventions.
With the introduction of higher field magnets, we are now able to achieve spatial resolutions of ... more With the introduction of higher field magnets, we are now able to achieve spatial resolutions of such superb quality that even the most exquisite details of the brain anatomy can be visualized in magnetic resonance imaging (MRI). With intraoperative image updates, brain deformations throughout the course of surgery are detected in near-real time and the resection progress is readily monitored. This enables accurate neuronavigation. Intraoperative MRI is approaching the point at which it will be used not only to localize, target, and guide resection of brain tumors and other intracranial lesions, but also to provide a comprehensive picture of the surrounding functional anatomy.
In many clinical procedures involving needle insertion, such as cryoablation, accurate navigation... more In many clinical procedures involving needle insertion, such as cryoablation, accurate navigation of the needle to the desired target is of paramount importance to optimize the treatment and minimize the damage to the neighboring anatomy. However, the force interaction between the needle and tissue may lead to needle deflection, resulting in considerable error in the intraoperative tracking of the needle tip. In this paper, we have proposed a Kalman filter-based formulation to fuse two sensor dataoptical sensor at the base and magnetic resonance (MR) gradient-field driven electromagnetic (EM) sensor placed 10 cm from the needle tipto estimate the needle deflection online. Angular springs model based tip estimations and EM based estimation without model are used to form the measurement vector in the Kalman filter. Static tip bending experiments show that the fusion method can reduce the error of the tip estimation by from 29.23 mm to 3.15 mm and from 39.96 mm to 6.90 mm at the MRI isocenter and 650 mm from the isocenter respectively.
Medical Imaging 2017: Image-Guided Procedures, Robotic Interventions, and Modeling, 2017
MRI-guided needle intervention for cryoablation is a promising way to relieve the pain and treat ... more MRI-guided needle intervention for cryoablation is a promising way to relieve the pain and treat the cancer. However, the limited size of MRI bore makes it impossible for clinicians to perform the operation in the bore. The patients had to be moved into the bore for scanning to verify the position of the needle’s tip and out for adjusting the needle’s trajectory. Real-time needle tracking and shown in MR images is of importance for clinicians to perform the operation more efficiently. In this paper, we have instrumented the cryotherapy needle with a MRI-safe electromagnetic (EM) sensor and optical sensor to measure the needle’s position and orientation. To overcome the limitation of line-of-sight for optical sensor and the poor dynamic performance of the EM sensor, Kalman filter based data fusion is developed. Further, we developed a navigation system in open-source software, 3D Slicer, to provide accurate visualization of the needle and the surrounding anatomy. Experiment of simulation the needle intervention at the entrance was performed with a realistic spine phantom to quantify the accuracy of the navigation using the retrospective analysis method. Eleven trials of needle insertion were performed independently. The target accuracy with the navigation using only EM sensor, only optical sensor and data fusion are 2.27 ±1.60 mm, 4.11 ± 1.77 mm and 1.91 − 1.10 mm, respectively.
D. F. Kacher, S. P. DiMaio, E. Samset, B. Fetics, E. Nevo, F. A. Jolesz Radiology, Brigham and Wo... more D. F. Kacher, S. P. DiMaio, E. Samset, B. Fetics, E. Nevo, F. A. Jolesz Radiology, Brigham and Women's Hospital, Boston, MA, United States, Radiology, Brigham and Women's Hospital, Boston, M, United States, Radiology, Brigham and Women's Hospital, Boston, MA, United Arab Emirates, Robin Medical, Baltimore, MD, United States MRI-guidance has increasing potential to augment or replace conventional X-ray fluoroscopy in cardiac, peripheral-, and neurovascular interventions [1]. Catheter tracking with MRI, using frequency encoding, to localize the NMR signal near small RF coils has been proven feasible [2]. Recently, an electromagnetic (EM) tracking system that utilizes the scanners gradients has emerged [3]. Coupling such tracking systems with near real-time imaging [4] and 3D visualization of previously acquired data sets [5] yields a powerful tool for the interventionalist. EM tracking has long been used in the cath lab setting for catheter tracking. The advantage of EM t...
Objective-The usefulness of neurosurgical navigation with current visualizations is seriously com... more Objective-The usefulness of neurosurgical navigation with current visualizations is seriously compromised by brain shift, which inevitably occurs during the course of the operation, significantly degrading the precise alignment between the preoperative MR data and the intraoperative shape of the brain. Our objectives were (i) to evaluate the feasibility of non-rigid registration that compensates for the brain deformations within the time constraints imposed by neurosurgery, and (ii) create augmented reality visualizations of critical structural and functional brain regions during neurosurgery using pre-operatively acquired fMRI and DT-MRI. Materials and Methods-Eleven consecutive patients with supratentorial gliomas were included in our study. All underwent surgery at our intra-operative MR imaging-guided therapy facility and have tumors in eloquent brain areas (e.g. precentral gyrus and cortico-spinal tract). Functional MRI and DT-MRI, together with MPRAGE and T2w structural MRI were acquired at 3T prior to surgery. SPGR and T2w images were acquired with a 0.5T magnet during each procedure. Quantitative assessment of the alignment accuracy was carried out and compared with current state-of the-art systems based only on rigid-registration. Results-Alignment between preoperative and intra-operative datasets was successfully carried out during surgery for all patients. Overall, the mean residual displacement remaining after nonrigid registration was 1.82 mm. There is a statistically significant improvement in alignment accuracy utilizing our non-rigid registration in comparison to the currently used technology (p<0.001). Conclusions-We were able to achieve intra-operative rigid and non-rigid registration of (1) pre-operative structural MRI with intra-operative T1w MRI; (2) pre-operative FMRI with intraoperative T1w MRI, and (3) pre-operative DT-MRI with intra-operative T1w MRI. The registration algorithms as implemented were sufficiently robust and rapid to meet the hard realtime constraints of intra-operative surgical decision making. The validation experiments demonstrate that we can accurately compensate for the deformation of the brain and thus can construct an augmented reality visualization to aid the surgeon.
Iwu (Magnetic Resonance Imagining) is a powerful medical diagnostic tool. Its value would be grea... more Iwu (Magnetic Resonance Imagining) is a powerful medical diagnostic tool. Its value would be greatly increased if it was possible to physically manipulate objects within the MRI during imaging. However, the extraordinarily strong magnetic fields used by the MRI make conventional-electromagnetic components, such as actuators and sensors, unusable. Io this paper, it is shown that devices constructed using binary polymer based actuators, called Electrostrictive Polymer Actuators (EPAM) are able to function effectively within the MRI without degrading its imaging performance. These actuators eliminate the need for conventional electromagnetic actuators and their associated electronics. The binary nature of the actuators eliminates the need for feedback sensors to control the devices motion. The basic concept called Digital Mechatronics is briefly summarized in this paper. Its application to a reconfigurable MRI surface- imaging coil (RMIC) is also presented. Experimental results are presented that show the EPAM RMIC is completely compatible in the MRI and can be used to enhance the diagnostic capabilities of MFU. The paper also suggests other applications of binary EPAM based actuators for use in MRI systems.
increased brain size results from an increase in brain growth or failure of the post-natal proces... more increased brain size results from an increase in brain growth or failure of the post-natal processes of axonal and/or synaptic pruning. In attempt to shed light on the pathophysiology of this finding the present study was designed to reexamine the brain size in a sample of high functioning autistics (HFA). We hypothesized that HFA would show an increase in cerebral volume (CV) when adjusting for intra-cranial volume (ICV) in comparison with age and IQ matched controls. A deficit in postnatal pruning would predict a larger brain relative to ICV. On the other hand, a normal pruning would predict that relative to ICV, the brain size would not differ from healthy controls. MRI scans from 16 HFA and 19 male volunteer comparison subjects were obtained and the volumes of the following structures were measured using NIH-IMAGE: gray and white matter, third, fourth, and lateral ventricles, in addition to the ICV and CV. Mean CV and third ventricle volumes in the autistic subjects were significantly greater than the control group when adjusted for ICV. No other significant results were found. Our finding of increased brain size in autism is consistent with previous reports in the literature. However, additional neuro-imaging and more importantly neuropathologic studies are needed to examine whether or not abnormalities in the pruning process underlie this finding.
INTRODUCTION: Functional MRI is increasingly used as an adjunct to neurosurgical planning. Our la... more INTRODUCTION: Functional MRI is increasingly used as an adjunct to neurosurgical planning. Our laboratory has developed techniques for 3-D reconstruction of morphologic and angiographic MR images. The 3-0 model may be registered with functional information derived from multiple modalities (fMRI. SPEeT. and intraoperative cortical mapping). We present two illustrative cases in which preoperative fMRI data were integrated with real-time intraoperative imagingtechniques for surgicalguidance.
BACKGROUND AND PURPOSE: The cause of posterior reversible encephalopathy syndrome (PRES) is unkno... more BACKGROUND AND PURPOSE: The cause of posterior reversible encephalopathy syndrome (PRES) is unknown. Two primary hypotheses exist: 1) hypertension exceeding auto-regulatory limits leading to forced hyper-perfusion and 2) vasoconstriction and hypo-perfusion leading to ischemia with resultant edema. The purpose of this study was to evaluate the catheter angiography (CA), MR angiography (MRA), and MR perfusion (MRP) features in PRES in order to render further insight into its mechanism of origin. MATERIALS AND METHODS: In 47 patients with PRES, 9 CAs and 43 MRAs were evaluated for evidence of vasculopathy (vasoconstriction and vasodilation), and 15 MRP studies were evaluated for altered relative cerebral blood volume (rCBV) in PRES lesions and regions. Visualization of vessels on MRA and toxicity blood pressures were compared with the extent of hemispheric vasogenic edema. RESULTS: Vasculopathy was present in 8 of 9 patients on CA (direct correlation to MRA in 3/6 patients). At MRA, moderate to severe vessel irregularity consistent with vasoconstriction and vasodilation was present in 30 of 43 patients and vessel pruning or irregularity in 7 patients, with follow-up MRA demonstrating reversal of vasoconstriction or vasodilation in 9 of 11 patients. Vasogenic edema was less in patients with hypertension compared with patients who were normotensive. Preserved normal length of the posterior cerebral artery (PCA) was commonly seen in patients with severe hypertension despite diffuse or focal vasoconstriction or vasodilation. In these patients, lengthier visualization of the distal PCA correlated with a lower grade of hemispheric edema (P ϭ .002). Cortical rCBV was significantly reduced in 51 of 59 PRES lesions and regions compared with a healthy reference cortex (average 61% of reference cortex) with mild decrease in the remainder. CONCLUSION: Vasculopathy was a common finding on CA and MRA in our patients with PRES, and MRP demonstrated reduced cortical rCBV in PRES lesions. Vasogenic edema was reduced in patients with hypertension, and superior distal PCA visualization correlated with reduced hemispheric edema in patients with PRES and severe hypertension.
Electrocardiographic (ECG) criteria for determining left ventricular mass in young healthy men; d... more Electrocardiographic (ECG) criteria for determining left ventricular mass in young healthy men; data from the LARGE Heart study
... MA) with a 128 element linear array transducer was connected to an interface box within the m... more ... MA) with a 128 element linear array transducer was connected to an interface box within the magnet room and the box was connected to a laptop computer outside the room ... MR images of a spherical phantom in a standard head coil were acquired with US probe inside the coil. ...
▪ The goal of the Image Guided Therapy Program, as the name implies, is to develop the use of i... more ▪ The goal of the Image Guided Therapy Program, as the name implies, is to develop the use of imaging to guide minimally invasive therapy. The program combines interventional and intraoperative magnetic resonance imaging (MRI) with high-performance computing and novel therapeutic devices. In clinical practice the multidisciplinary program provides for the investigation of a wide range of interventional and surgical procedures. The Signa SP 0.5 T superconducting MRI system (GE Medical Systems, Milwaukee, WI) has a 56-cm-wide vertical gap, allowing access to the patient and permitting the execution of interactive MRI-guided procedures. This system is integrated with an optical tracking system and utilizes flexible surface coils and MRI-compatible displays to facilitate procedures. Images are obtained with routine pulse sequences. Nearly real-time imaging, with fast gradient-recalled echo sequences, may be acquired at a rate of one image every 1.5 s with interactive image plane selec...
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Papers by Daniel Kacher