Analyzing 3-tesla magnetic resonance imaging units for implementation in radiosurgery

2005 ◽  
Vol 102 ◽  
pp. 158-164 ◽  
Author(s):  
Andreas Mack ◽  
Robert Wolff ◽  
Stefan Scheib ◽  
Marcus Rieker ◽  
Dirk Weltz ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Image Quality ◽  
Mr Imaging ◽  
Field Strength ◽  
3 Tesla ◽  
Maximum Deviation ◽  
Content Type ◽  
Stereotactic Frame ◽  
Susceptibility Effects ◽  
Fine Print

Object.The limiting factor affecting accuracy during gamma knife surgery is image quality. The new generation of magnetic resonance (MR) imaging units with field strength up to 3 teslas promise superior image quality for anatomical resolution and contrast. There are, however, questions about chemical shifts or susceptibility effects, which are the subject of this paper.Methods.The 3-tesla MR imaging unit (Siemens Trio) was analyzed and compared with a 1-tesla unit (Siemens Magnetom Expert) and to a 1.5-tesla unit (Philips Gyroscan). Evaluation of the magnitude of error was performed within transverse slices in two orientations (axial/coronal) by using a cylindrical phantom with an embedded grid. Deviations were determined for 21 targets in a slab phantom with known geometrical positions within the stereotactic frame. Distortions caused by chemical shift and/or susceptibility effects were analyzed in a head phantom. Inhouse software was used for data analyses.The mean deviation was less than 0.3 mm in axial and less than 0.4 mm in coronal orientations. For the known targets the maximum deviation was 1.16 mm. By optimizing these parameters in the protocol these inaccuracies could be reduced to less than 1.1 mm. Due to inhomogeneities a shift in the z direction of up to 1.5 mm was observed for a dataset, which was shown to be compressed by 1.2 mm.Conclusions.The 3-tesla imaging unit showed superior anatomical contrast and resolution in comparison with the established 1-tesla and 1.5-tesla units; however, due to the high field strength the field within the head coil is very sensitive to inhomogeneities and therefore 3-tesla imaging data will have be handled with care.

Analyzing 3-tesla magnetic resonance imaging units for implementation in radiosurgery

2005 ◽  
Vol 102 (Special_Supplement) ◽  
pp. 158-164 ◽  
Author(s):  
Andreas Mack ◽  
Robert Wolff ◽  
Stefan Scheib ◽  
Marcus Rieker ◽  
Dirk Weltz ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Image Quality ◽  
Mr Imaging ◽  
Field Strength ◽  
3 Tesla ◽  
Maximum Deviation ◽  
Content Type ◽  
Stereotactic Frame ◽  
Susceptibility Effects ◽  
Fine Print

Object. The limiting factor affecting accuracy during gamma knife surgery is image quality. The new generation of magnetic resonance (MR) imaging units with field strength up to 3 teslas promise superior image quality for anatomical resolution and contrast. There are, however, questions about chemical shifts or susceptibility effects, which are the subject of this paper. Methods. The 3-tesla MR imaging unit (Siemens Trio) was analyzed and compared with a 1-tesla unit (Siemens Magnetom Expert) and to a 1.5-tesla unit (Philips Gyroscan). Evaluation of the magnitude of error was performed within transverse slices in two orientations (axial/coronal) by using a cylindrical phantom with an embedded grid. Deviations were determined for 21 targets in a slab phantom with known geometrical positions within the stereotactic frame. Distortions caused by chemical shift and/or susceptibility effects were analyzed in a head phantom. Inhouse software was used for data analyses. The mean deviation was less than 0.3 mm in axial and less than 0.4 mm in coronal orientations. For the known targets the maximum deviation was 1.16 mm. By optimizing these parameters in the protocol these inaccuracies could be reduced to less than 1.1 mm. Due to inhomogeneities a shift in the z direction of up to 1.5 mm was observed for a dataset, which was shown to be compressed by 1.2 mm. Conclusions. The 3-tesla imaging unit showed superior anatomical contrast and resolution in comparison with the established 1-tesla and 1.5-tesla units; however, due to the high field strength the field within the head coil is very sensitive to inhomogeneities and therefore 3-tesla imaging data will have be handled with care.

Asymptomatic microbleeds in moyamoya disease: T2*-weighted gradient-echo magnetic resonance imaging study

2005 ◽  
Vol 102 (3) ◽  
pp. 470-475 ◽  
Author(s):  
Ken-Ichiro Kikuta ◽  
Yasushi Takagi ◽  
Kazuhiko Nozaki ◽  
Takashi Hanakawa ◽  
Tsutomu Okada ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Mr Imaging ◽  
Moyamoya Disease ◽  
Imaging Study ◽  
Mr Studies ◽  
3 Tesla ◽  
Healthy Individuals ◽  
Gradient Echo ◽  
Content Type ◽  
Fine Print

Object. The aim of this study was to investigate the incidence of asymptomatic microbleeds (MBs) in patients with moyamoya disease (MMD) by using a 3-tesla magnetic resonance (MR) imaging unit. Methods. Data on 63 patients hospitalized with MMD between 1999 and 2004 were retrospectively examined to determine the incidence of asymptomatic MBs. Gradient-echo T2*-weighted MR imaging studies obtained using 3- and 1.5-tesla units were available in 25 patients. These patients consisted of five men and 20 women, ranging in age from 17 to 66 years (mean age 41 ± 14 years). Ischemic MMD was diagnosed in 18 patients, and hemorrhagic MMD in seven. The incidence of MBs was also evaluated using the same 3-tesla MR imaging unit in 34 healthy volunteers including seven men and 27 women, ranging in age from 18 to 71 years (mean age 33 ± 12 years). Using the 3-tesla MR unit, asymptomatic MBs were demonstrated in 11 patients (44%); they were detected in seven patients (28%) by using the 1.5-tesla unit. In the 3-tesla MR studies in healthy individuals, MBs were found in two patients (5.8%). Based on 3-tesla MR studies, the incidence of MBs was significantly higher in patients with MMD compared with that in healthy individuals. Asymptomatic MBs were demonstrated in eight (44%) of 18 patients with ischemic MMD and three (43%) of seven patients with hemorrhagic MMD. Conclusions. Microbleeds are significantly more common in patients with MMD than in healthy individuals regardless of the disease type. The evaluation of MBs with T2*-weighted 3-tesla MR imaging might contribute to the treatment of MMD.

Early changes measured by magnetic resonance imaging in cerebral blood flow, blood volume, and blood-brain barrier permeability following dexamethasone treatment in patients with brain tumors

1999 ◽  
Vol 90 (2) ◽  
pp. 300-305 ◽  
Author(s):  
Leif Østergaard ◽  
Fred H. Hochberg ◽  
James D. Rabinov ◽  
A. Gregory Sorensen ◽  
Michael Lev ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Magnetic Resonance ◽  
Brain Tumors ◽  
Mr Imaging ◽  
Blood Volume ◽  
Cerebral Blood Volume ◽  
Clinical Effects ◽  
Content Type ◽  
Fine Print

Object. In this study the authors assessed the early changes in brain tumor physiology associated with glucocorticoid administration. Glucocorticoids have a dramatic effect on symptoms in patients with brain tumors over a time scale ranging from minutes to a few hours. Previous studies have indicated that glucocorticoids may act either by decreasing cerebral blood volume (CBV) or blood-tumor barrier (BTB) permeability and thereby the degree of vasogenic edema.Methods. Using magnetic resonance (MR) imaging, the authors examined the acute changes in CBV, cerebral blood flow (CBF), and BTB permeability to gadolinium-diethylenetriamine pentaacetic acid after administration of dexamethasone in six patients with brain tumors. In patients with acute decreases in BTB permeability after dexamethasone administration, changes in the degree of edema were assessed using the apparent diffusion coefficient of water.Conclusions. Dexamethasone was found to cause a dramatic decrease in BTB permeability and regional CBV but no significant changes in CBF or the degree of edema. The authors found that MR imaging provides a powerful tool for investigating the pathophysiological changes associated with the clinical effects of glucocorticoids.

Accelerated spondylotic changes adjacent to the fused segment following central cervical corpectomy: magnetic resonance imaging study evidence

2004 ◽  
Vol 100 (1) ◽  
pp. 2-6 ◽  
Author(s):  
Vaijayantee Kulkarni ◽  
Vedantam Rajshekhar ◽  
Lakshminarayan Raghuram
Keyword(s):  
Magnetic Resonance ◽  
Mr Imaging ◽  
Imaging Study ◽  
Degenerative Changes ◽  
Adjacent Segment ◽  
Mr Images ◽  
Short Term ◽  
Content Type ◽  
Fine Print

Object. The authors studied whether cervical spine motion segments adjacent to a fused segment exhibit accelerated degenerative changes on short-term follow-up magnetic resonance (MR) imaging. Methods. Preoperative and short-term follow-up (mean duration 17.5 months, range 10–48 months) cervical MR images obtained in 44 patients who had undergone one- or two-level corpectomy for cervical spondylotic myelopathy were evaluated qualitatively and quantitatively. The motion segment adjacent to the fused segment and a segment remote from the fused segment were evaluated for indentation of the thecal sac, disc height, and sagittal functional diameter of the spinal canal on midsagittal T2-weighted MR images. Thecal sac indentations were classifed as mild, moderate, and severe. New indentations of the thecal sac of varying severity (mild in 17 patients [38.6%], moderate in 10 [22.7%], and severe in six [13.6%]) had developed at the adjacent segments in 33 (75%) of 44 patients. The degenerative changes were seen at the superior level in 11 patients, inferior level in 10 patients, and at both levels in 12 patients and resulted from both anterior and posterior element degeneration in the majority (23 [69.6%]) of patients. The remote segments showed mild thecal sac indentations in seven patients and moderate indentations in two patients (nine [20.5%] of 44). Compared with the changes at the remote segment, the canal size was significantly decreased at the superior adjacent segment by 0.9 mm (p = 0.007). No patient sustained a new neurological deficit due to adjacent-segment changes. Conclusions. On short-term follow-up MR imaging, levels adjacent to the fused segment exhibited more pronounced degenerative changes (compared with remote levels) in 75% of patients who had undergone one- or two-level central corpectomy.

Lack of agreement between direct magnetic resonance imaging and statistical determination of a subthalamic target: the role of electrophysiological guidance

2002 ◽  
Vol 97 (3) ◽  
pp. 591-597 ◽  
Author(s):  
Emmanuel Cuny ◽  
Dominique Guehl ◽  
Pierre Burbaud ◽  
Christian Gross ◽  
Vincent Dousset ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Mr Imaging ◽  
Functional Response ◽  
Anterior Commissure ◽  
Surgical Techniques ◽  
High Frequency Stimulation ◽  
Mr Images ◽  
Posterior Commissure ◽  
Content Type ◽  
Fine Print

Object. The goal of this study was to determine the most suitable procedure(s) to localize the optimal site for high-frequency stimulation of the subthalamic nucleus (STN) for the treatment of advanced Parkinson disease. Methods. Stereotactic coordinates of the STN were determined in 14 patients by using three different methods: direct identification of the STN on coronal and axial T2-weighted magnetic resonance (MR) images and indirect targeting in which the STN coordinates are referred to the anterior commissure—posterior commissure (AC—PC) line, which, itself, is determined either by using stereotactic ventriculography or reconstruction from three-dimensional (3D) MR images. During the surgical procedure, electrode implantation was guided by single-unit microrecordings on multiple parallel trajectories and by clinical assessment of stimulations. The site where the optimal functional response was obtained was considered to be the best target. Computerized tomography scanning was performed 3 days later and the scans were combined with preoperative 3D MR images to transfer the position of the best target to the same system of stereotactic coordinates. An algorithm was designed to convert individual stereotactic coordinates into an all-purpose PC-referenced system for comparing the respective accuracy of each method of targeting, according to the position of the best target. Conclusions. The target that is directly identified by MR imaging is more remote (mainly in the lateral axis) from the site of the optimal functional response than targets obtained using other procedures, and the variability of this method in the lateral and superoinferior axes is greater. In contrast, the target defined by 3D MR imaging is closest to the target of optimal functional response and the variability of this method is the least great. Thus, 3D reconstruction adjusted to the AC—PC line is the most accurate technique for STN targeting, whereas direct visualization of the STN on MR images is the least effective. Electrophysiological guidance makes it possible to correct the inherent inaccuracy of the imaging and surgical techniques and is not designed to modify the initial targeting.

Physiological support and monitoring of critically ill patients during magnetic resonance imaging

1988 ◽  
Vol 68 (2) ◽  
pp. 246-250 ◽  
Author(s):  
Gene H. Barnett ◽  
Allan H. Ropper ◽  
Keith A. Johnson
Keyword(s):  
Magnetic Resonance ◽  
Mr Imaging ◽  
Critically Ill ◽  
Resonance Imaging ◽  
Monitoring Equipment ◽  
Mr Image ◽  
Content Type ◽  
Neurological Patients ◽  
Fine Print ◽  
Electrical Interference

✓ Magnetic resonance (MR) imaging has been largely restricted to patients who are neurologically and hemodynamically stable. The strong magnetic field and radiofrequency transmissions involved in acquiring images are potential sources of interference with monitoring equipment. A method of support and physiological monitoring of critically ill neurosurgical and neurological patients during MR imaging using a 0.6-tesla MR system is reported. This technique has not caused degradation of the MR image due to electrical interference. Adequate preparation and precautions allow many critically ill neurosurgical and neurological patients to safely undergo MR imaging.

Correlation of the relationships of brain—tumor interfaces, magnetic resonance imaging, and angiographic findings to predict cleavage of meningiomas

1999 ◽  
Vol 91 (3) ◽  
pp. 384-390 ◽  
Author(s):  
Faruk İldan ◽  
Metin Tuna ◽  
Alp İskender Göcer ◽  
Bülent Boyar ◽  
Hüseyin Bağdatoğlu ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Brain Tumor ◽  
Magnetic Resonance ◽  
Mr Imaging ◽  
Vascular Supply ◽  
Peritumoral Edema ◽  
Resonance Imaging ◽  
Content Type ◽  
Angiographic Findings ◽  
Fine Print

Object. The authors examined the relationships of brain—tumor interfaces, specific magnetic resonance (MR) imaging features, and angiographic findings in meningiomas to predict tumor cleavage and difficulty of resection.Methods. Magnetic resonance imaging studies, angiographic data, operative reports, clinical data, and histopathological findings were examined retrospectively in this series, which included 126 patients with intracranial meningiomas who underwent operations in which microsurgical techniques were used. The authors have identified three kinds of brain—tumor interfaces characterized by various difficulties in microsurgical dissection: smooth type, intermediate type, and invasive type. The signal intensity on T1-weighted MR images was very similar regardless of the type of brain—tumor interface (p > 0.1). However, on T2-weighted images the different interfaces seemed to correlate very precisely with the signal intensity and the amount of peritumoral edema (p < 0.01), allowing the prediction of microsurgical effort required during surgery. On angiographic studies, the pial—cortical arterial supply was seen to participate almost equally with the meningeal—dural arterial supply in vascularizing the tumor in 57.9% of patients. Meningiomas demonstrating hypervascularization on angiography, particularly those fed by the pial—cortical arteries, exhibited significantly more severe edema compared with those supplied only from meningeal arteries (p < 0.01). Indeed, a positive correlation was found between the vascular supply from pial—cortical arteries and the type of cleavage (p < 0.05).Conclusions. In this analysis the authors proved that there is a strong correlation between the amount of peritumoral edema, hyperintensity of the tumor on T2-weighted images, cortical penetration, vascular supply from pial—cortical arteries, and cleavage of the meningioma. Therefore, the consequent difficulty of microsurgical dissection can be predicted preoperatively by analyzing MR imaging and angiographic studies.

Analysis of aqueductal cerebrospinal fluid flow after endoscopic aqueductoplasty by using cine phase-contrast magnetic resonance imaging

2000 ◽  
Vol 93 (2) ◽  
pp. 237-244 ◽  
Author(s):  
Henry W. S. Schroeder ◽  
Christiane Schweim ◽  
Klaus H. Schweim ◽  
Michael R. Gaab
Keyword(s):  
Cerebrospinal Fluid ◽  
Magnetic Resonance ◽  
Mr Imaging ◽  
Healthy Volunteers ◽  
Phase Contrast ◽  
Aqueductal Stenosis ◽  
Csf Flow ◽  
Content Type ◽  
Endoscopic Aqueductoplasty ◽  
Fine Print

Object. The purpose of this prospective study was to evaluate aqueductal cerebrospinal fluid (CSF) flow after endoscopic aqueductoplasty. In all patients, preoperative magnetic resonance (MR) imaging revealed hydrocephalus caused by aqueductal stenosis and lack of aqueductal CSF flow.Methods. In 14 healthy volunteers and in eight patients with aqueductal stenosis who had undergone endoscopic aqueductoplasty, aqueductal CSF flow was investigated using cine cardiac-gated phase-contrast MR imaging. For qualitative evaluation of CSF flow, the authors used an in-plane phase-contrast sequence in the midsagittal plane. The MR images were displayed in a closed-loop cine format. Quantitative through-plane measurements were performed in the axial plane perpendicular to the aqueduct. Evaluation revealed no significant difference in aqueductal CSF flow between healthy volunteers and patients with regard to temporal parameters, CSF peak and mean velocities, mean flow, and stroke volume. All restored aqueducts have remained patent 7 to 31 months after surgery.Conclusions. Aqueductal CSF flow after endoscopic aqueductoplasty is similar to aqueductal CSF flow in healthy volunteers. The data indicate that endoscopic aqueductoplasty seems to restore physiological aqueductal CSF flow.

Magnetic resonance imaging evaluation of adjacent segments after disc arthroplasty

2005 ◽  
Vol 3 (5) ◽  
pp. 342-347 ◽  
Author(s):  
Chris J. Neal ◽  
Michael K. Rosner ◽  
Timothy R. Kuklo
Keyword(s):  
Magnetic Resonance ◽  
Mr Imaging ◽  
Disc Replacement ◽  
Disc Space ◽  
Disc Arthroplasty ◽  
Content Type ◽  
Motion Segment ◽  
Adjacent Segments ◽  
Weighted Sequences ◽  
Fine Print

Object. Disc arthroplasty in the lumbar spine is an alternative to fusion when treating discogenic pain. Its theoretical benefits include preservation of the motion segment and the potential prevention of adjacent-segment degeneration. Despite the need to evaluate the benefit of preserving the adjacent segments after disc replacement, no study has been conducted to assess the ability of magnetic resonance (MR) imaging to depict the adjacent segments in patients who have undergone disc replacement surgery. Methods. Postoperative lumbar MR images were obtained in the first 10 patients in whom a metal-on-metal disc arthroplasty system was used to treat the L4–5 or L5—S1 levels. At the superior adjacent level, the superior endplate and disc space were demonstrated on 90% of the images on both T1-weighted fluid-attenuated inversion-recovery (FLAIR) and T2-weighted sequences despite the presence of artifacts. The inferior endplate at this level was documented on 70% of both T1-weighted FLAIR and T2-weighted sequences. At the level below the disc replacement in patients who underwent L4–5 surgery, the superior endplate was demonstrated on 66.7% of the T1-weighted FLAIR sequences but only 33.3% of the T2-weighted images. The disc space and inferior endplate were depicted on 66.7% of both T1-weighted FLAIR and T2-weighted sequences. Axial images revealed an artifact in every adjacent space except at the L5—S1 level. Conclusions. Based on the results of this pilot study, it appears that sagittal MR imaging can be undertaken to evaluate the adjacent motion segment for degenerative changes following total disc arthroplasty in most patients. This imaging modality will provide an additional measure to assess the long-term efficacy of this intervention compared with other treatment modalities and the natural history of lumbar disc degeneration.

Magnetic resonance imaging—documented extravasation as an indicator of acute hypertensive intracerebral hemorrhage

1998 ◽  
Vol 88 (4) ◽  
pp. 650-655 ◽  
Author(s):  
Yasuo Murai ◽  
Yukio Ikeda ◽  
Akira Teramoto ◽  
Yukihide Tsuji
Keyword(s):  
Magnetic Resonance ◽  
Mr Imaging ◽  
Intracerebral Hemorrhage ◽  
Cerebral Angiography ◽  
Ct Scanning ◽  
Content Type ◽  
Hematoma Enlargement ◽  
Hypertensive Intracerebral Hemorrhage ◽  
Fine Print

Object. The aim of this study was to determine the usefulness of magnetic resonance (MR) imaging—documented extravasation as an indicator of continued hemorrhage in patients with acute hypertensive intracerebral hemorrhage (ICH). Methods. The authors studied 108 patients with acute hyperintensive ICH. Imaging modalities included noncontrast-enhanced computerized tomography (CT) scanning, gadolinium-enhanced MR imaging, and conventional cerebral angiography obtained within 6 hours after the onset of hemorrhage. A repeated CT scan was obtained within 48 hours to evaluate enlargement of the hematoma. Findings on MR imaging indicating extravasation, including any high-intensity signals on T1-weighted postcontrast images, were observed in 39 patients, and 17 of these also showed evidence of extravasation on cerebral angiography. The presence of extravasation on MR imaging was closely correlated with evidence of hematoma enlargement on follow-up CT scans (p < 0.001). Conclusions. Evidence of extravasation documented on MR imaging indicates persistent hemorrhage and correlates with enlargement of the hematoma.

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