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Method of construction of a MRI-based tabular database of 3D stereotaxic co-ordinates for individual structures in the basal ganglia of Macaca mulatta.

Primate models are commonly used in Parkinson's disease research to study stereotaxic strategies that demand accurate localization of the structures in basal ganglia. We demonstrate a method to construct an extensive tabular database of 3D stereotaxic co-ordinates of various basal ganglia structures from high-quality magnetic resonance (MR) images of 47 adult female 3-5 kg rhesus monkeys. For each animal, the structures in the basal ganglia were traced as they appeared on the axial MR images. Their maximal outlines were projected in the axial plane to create a stack of images and X, Y, Z co-ordinates were calculated for margins of each structure. These co-ordinates and the outlines of the individual nuclei help delineate a "common area," which was further narrowed down to a point that represents the 'most reliable target point' (MRTP) in subthalamic nucleus, globus pallidum, caudate and putamen on both sides. Common area and MRTP represent the region that can most definitely be associated with a structure and hence the most definite target for a given structure. The goal of this study is to demonstrate the method of construction, discuss the feasibility and usefulness of such a tabular database that could potentially add to accuracy of localization while using atlas-based stereotaxy. Though use of MRI remains a standard practice and advances in imaging have made targeting for functional surgery more accurate, in developing countries that implies prohibitive costs per procedure. Population based human databases similar to the monkey database described here, when used along with less expensive imaging modalities can reduce the costs considerably as well as add to the accuracy of targeting.

Animals↗

Frameless stereotaxy in the nonhuman primate.

With the advent of magnetic resonance imaging (MRI), it is possible to obtain high-resolution anatomical images of the monkey brain. Accuracy, however, is lost in the laboratory or surgical setting when the localization of brain structures depends on nonstereotaxic tracking methods. Here we present an image-guided stereotaxic system that is able to localize and access anatomical brain structures using the monkey's MRI. This system, which is also known as frameless stereotaxy, is capable of computing the relation of the physical "real space" of the monkey's head to the corresponding image space, while a position sensor enables the tracking of the animal's head and the localization of brain areas and favorable paths to targets within the brain using real time display software. Surgical procedures make use of an adjustable upright chair and a surgical headclamp instead of the traditional restrictive head holder with ear bars. This novel system allows for the flexible positioning of the animal and the ability to reach areas of the brain that were difficult to access in the past. The headclamp also serves as a tool holder, which in the present application guided a cannula of retrograde tracer to the desired location in the frontal lobe. Histological examination of the brain showed that the injection reached the target site, and tests using an MRI compatible phantom demonstrated that the precision of the system in bringing an injection to target is less than 1.2 mm. This system can be used to inject accurately tracers for anatomical tract-tracing, to make precise lesions, and to position electrodes for electrophysiological studies.

Animals↗

Dynamic analysis of articulatory movement using magnetic resonance imaging movies: methods and implications in cleft lip and palate.

OBJECTIVES: To visualize articulatory movement using a magnetic resonance imaging (MRI) movie of a subject with cleft lip and palate (clp) and to demonstrate the usefulness of this method for studying oropharyngeal function. MATERIAL AND METHODS: Dynamic changes in oropharyngeal structures were assessed with an MRI movie of a man with cleft lip and palate and in a normal adult male volunteer during the articulation of /pa/, /ta/, and /ka/. RESULTS AND CONCLUSIONS: Different movement patterns were observed during articulation in the subject with CLP compared with the normal volunteer. Posterosuperior movement of the tongue and the anterior movement of the posterior pharyngeal wall were clearly visualized in the subject with CLP. Thus, MRI movies appear to be a promising tool for evaluating speech function in patients with CLP because of their noninvasive and nonradiation nature.

Adult↗

[Radiologic diagnosis of Perthes disease].

In Legg-Calvé-Perthes disease (LCPD), magnetic resonance imaging (MRI) and conventional radiography in two planes are considered the most important methods of investigation for early diagnosis and for assessment of the course of the disease. MRI can reveal the early marrow oedema, thus allowing early differential diagnosis against diseases that are similar in clinical appearance (coxitis fugax, epiphyseal dysplasia). The extent of the necrotic area within the epiphysis, the most important indicator of the prognosis of the disease and thus for the therapeutic management, can be assessed earlier and more reliably with MRI than with other techniques. The loss of containment can be visualized by MRI, because depiction of the cartilaginous structures is possible earlier than with conventional radiography. Staging of LCPD is also possible with MRI, especially in stages I and II. Radiography shows the reossification and the osseous remodelling of the epiphysis better. A disadvantage of MRI seems to be the occasional need for sedation or anaesthesia of the child to avoid motion artefacts.

Diagnosis, Differential↗

High-resolution magnetic resonance imaging of the wrist: normal anatomy.

Magnetic resonance imaging (MRI) provided adequate depiction of carpal soft tissue structures in normal volunteers, as well as accurate anatomic correlation with cadaveric specimens. Using a high field strength system and surface coil techniques, the intricate anatomy of the wrist was best defined on long TR short TE images. However, from a practical view, T1 weighted images (TR 600 ms, TE 25 ms) were most useful because of short imaging times, satisfactory image quality, and the absence of motion artifacts. The coronal plane provided the clearest definition of important structures. Potential diagnostic limitations exist due to the inability of MRI to clearly delineate articular cartilage, joint capsules, and small interosseous ligaments. The presence of intra-articular fluid in both living subjects and cadaveric specimens, however, allowed for fine depiction of these structures on T2 weighted images.

Humans↗

Mindboggle: a scatterbrained approach to automate brain labeling.

Mindboggle (http://www.binarybottle.com/mindboggle.html) is a fully automated, feature matching approach to label cortical structures and activity anatomically in human brain MRI data. This approach does not assume that the existence of component structures and their relative spatial relationship is preserved from brain to brain, but instead disassembles a labeled atlas and reassembles its pieces to match corresponding pieces in an unlabeled subject brain before labeling. Mindboggle: (1) converts linearly coregistered subject and atlas MRI data into sulcus pieces, (2) matches each atlas piece with a combination of subject pieces by minimizing a cost function, (3) transforms atlas label boundaries to the matching subject pieces, (4) warps atlas labels to their transformed boundaries, and (5) propagates labels to fill remaining gaps in a mask derived from the subject brain. We compared Mindboggle with four registration methods: linear registration, and nonlinear registration using SPM2, AIR, and ANIMAL. Automated labeling by all of the nonlinear methods was found to be at least comparable with linear registration. Mindboggle outperformed every other method, as measured by the agreement between overlapping atlas labels and manually assigned subject labels, with respect to the union or the intersection of voxels. After applying the same procedure that Mindboggle uses to fill a subject's segmented gray matter mask with labels (step 5), the results of the other methods improved. However, after performing a one-way ANOVA (and Tukey's honestly significant difference criterion) in a multiple comparison between the results obtained by the different methods, Mindboggle was still found to be the only nonlinear method whose labeling performance was significantly better than that of linear registration or SPM2. Further advantages to Mindboggle include a high degree of robustness against image artifacts, poor image quality, and incomplete brain data. We tested the latter hypothesis by conducting all of the tests again, this time registering the atlas to an artificially lesioned version of itself, and found that Mindboggle was the only method whose performance did not degrade significantly as the lesion size increased.

Animals↗

[Follow-up monitoring with magnetic resonance tomography after decompressive trephining in experimental "malignant" hemispheric infarct].

Acute ischemia in the complete territory of the carotid or the middle cerebral artery may lead to cerebral edema with raised intracranial pressure and progression to coma and death. Although clinical data suggest benefit for patients undergoing decompressive surgery for massive space occupying hemispheric stroke, little data about the effects of this procedure on morbidity and outcome is available. The experimental data support an early surgical approach. For early and probably most effective treatment of severe, space-occupying cerebral ischemia, the "malignant" character of the brain edema has to be recognized early after onset of vessel occlusion. Hereby magnetic resonance imaging (MRI) may allow to determine the clinical significance of brain edema early after onset, simultaneously allowing to monitor the evolution of ischemia. We performed serial SE-MRI in rats with acute hemispheric infarctions treated by decompressive craniectomy. Focal cerebral ischemia was induced in 36 rats using an endovascular occlusion technique. Decompressive craniectomy was performed 4 and 24 hours after vessel occlusion in groups of 12 animals each. Twelve animals were not treated by decompressive craniectomy (control group). Four, 24, 48, 72 and 168 hours after MCAO all animals were examined with conventional T1- and T2-weighted SE-MRI. Shift of the midline structures and compression of the ventricles were scored. Changes in weight and neurological performance were measured daily. The infarction volume was calculated by triphenyltetrazolium chloride staining 168 hours after MCAO. While mortality in the untreated group was 33.3%, none of the animals treated by a decompressive craniectomy died (mortality 0%). Neurological behaviour, weight loss and infarction volume were significantly better in the animals treated by early decompressive craniectomy (p < 0.05). Four hours after MCAO all untreated animals showed a massive shift of the midline structures and a massive compression of the ventricles; only 7 of 12 animals treated early by craniectomy showed mild mass effects. Correlation of the histological brain damage with T2-weighted MRI 4 hours after MCAO was poor (r = 0.41); later than 24 hours there was a good correlation (r > 0.7). Our results suggest that decompressive craniectomy in malignant cerebral ischemia reduces mortality and significantly improves outcome. If performed early after vessel occlusion, it also significantly reduces infarction size. In the acute phase of hemispheric infarction conventional SE-MRI is not sensitive in estimation of infarction size. Later than 24 hours, conventinal SE-MRI proved to be useful in monitoring brain edema and infarction size in this rat model of malignant hemispheric stroke.

Animals↗

Update of tests of colon and rectal structure and function.

This review deals with the indications, methods, strengths, and limitations of anorectal testing in clinical practice. In chronic constipation, anal manometry and a rectal balloon expulsion test, occasionally supplemented by defecography, are useful to identify a functional defecatory disorder, because symptoms may respond to pelvic floor retraining. In patients with fecal incontinence, diagnostic testing complements the clinical assessment for evaluating the pathophysiology and guiding management. Manometry measures anal resting and squeeze pressures, which predominantly reflect internal and external anal sphincter function, respectively. Defecation may be indirectly assessed by measuring the recto-anal pressure gradient during straining and by the rectal balloon expulsion test. Endoanal ultrasound and magnetic resonance imaging (MRI) can identify anal sphincter structural pathology, which may be clinically occult, and/or amenable to surgical repair. Only MRI can identify external sphincter atrophy, whereas ultrasound is more sensitive for internal sphincter imaging. By characterizing rectal evacuation and puborectalis contraction, barium defecography may demonstrate an evacuation disorder, excessive perineal descent or a rectocele. Dynamic MRI can provide similar information and also image the bladder and genital organs without radiation exposure. Because the measurement of pudendal nerve latencies suffers from several limitations, anal sphincter electromyography is recommended when neurogenic sphincter weakness is suspected.

Anal Canal↗

[Diagnosis of atrial septal defect using magnetic resonance imaging].

We studied the morphological features of defects of the interatrial septum using magnetic resonance imaging (MRI) to determine the sizes of defects and other abnormalities. MR images were obtained in 28 patients with atrial septal defect, including five cases with complicated anomalies (two with Ebstein's anomaly, one pentalogy of Fallot, and one anomalous pulmonary vein connection and azygos continuation). Images were also obtained in the control subjects including seven normal volunteers and 142 patients with various acquired heart diseases. The diagnosis of atrial septal defect was established by cardiac catheterization, angiography and two-dimensional echocardiography prior to the MRI studies, and in 14 patients, the diagnosis was confirmed by surgery. The MRI unit had a superconducting magnet and operated at 0.25 or 0.50 Tesla. A spin echo pulse sequence was used with an echo time of 40 or 60 msec. At the beginning of this study, non-gated MRI images were obtained in the 28 controls and in three patients with atrial septal defect. Nongated MRI could not image the anatomical structure of the interatrial septa of 12 of the 28 controls, or any of the three patients with atrial septal defect. Nongated MRI was, therefore, inadequate for visualizing cardiac anatomy. Gated MRI images were obtained in 141 controls and in 25 patients with atrial septal defect. Gated MRI revealed the interatrial septum, interventricular septum, atrioventricular septum, mitral valve, tricuspid valve and other intracardiac structures in most subjects. In 17 control subjects (12%), however, there was a very faint signal from the central portion of the interatrial septum. In these instances, there was a gradual fading of the signal of the interatrial septum, so that they could be distinguished from the atrial septal defect. The sudden disappearance of the signal from the interatrial septum was observed by gated MRI in all 25 patients with atrial septal defect. The sizes of the defects by MRI coincided with the findings at surgery in all 14 patients. MRI showed right atrial dilatation, right ventricular hypertrophy and dilatation, and pulmonary artery dilatation in most of the patients having atrial septal defect. Complex anomalies associated with atrial septal defect were also clearly shown by MRI, such as displacement of the tricuspid leaflets in two patients with Ebstein's anomaly, and anomalous pulmonary venous connection and persistent left superior vena cava in one patient. These results indicated that gated MRI is a valuable noninvasive method of diagnosing atrial septal defect and complicating anomalies.

Adolescent↗

Sequelae of acute myocardial infarction regarding cardiac structure and function and their prognostic significance as assessed by magnetic resonance imaging.

AIMS: Because of its high spatial resolution and tissue contrast, magnetic resonance imaging (MRI) was used to assess cardiac structure and function in a large population of patients with acute myocardial infarction (AMI). METHODS AND RESULTS: One hundred and ten patients were studied by MRI 6.1 +/- 2.2 days after AMI. Infarct size (IS), persistent microvascular obstruction (PMO), left and right ventricular (LV/RV) volumes, and functions were measured. The same MRI measurements were repeated in 89 patients after a mean follow-up period of 225 +/- 92 days. IS was 11.9 +/- 7.3% of total LV muscle mass. PMO was detected in 51/110 (46.4%) patients and comprised 15.6 +/- 8.5% of IS and 2.8 +/- 2.3% of LV muscle mass. Papillary muscle infarct was seen in 26%, RV infarction in 16%, pericarditis in 40%, and pericardial effusion in 66% of the patients. During follow-up, there were 16 major adverse cardiac events (MACE) including seven deaths. IS, PMO, and amount of transmural infarction were predictive for LV adverse remodelling defined as > 20% increase in LV end-diastolic volume. Multivariable analysis revealed LV end-diastolic volume, LV ejection fraction, and PMO as significant predictors for the occurrence of MACE. CONCLUSION: MRI is a highly sensitive and reliable tool to detect morphologic and functional sequelae of AMI providing baseline MRI parameters with relevant predictive power for LV adverse remodelling and occurrence of MACE.

Aged↗

[Shoulder imaging: what is the best modality?].

Specific pathologies of the shoulder include instabilities in young patients and tendinopathies in older patients. The choice of imaging modality depends on the information expected from each technique. In case of instability, plain films demonstrate bone abnormalities such as Hill Sachs and/or Bankart lesions. Arthro-CT or arthro-MRI need not be in all cases but can provide additional information performed about the intraarticular structures and the glenoid labrum. The rotator cuff is initially evaluated by plain films which demonstrate anatomical conditions resulting in impingement syndrome as well as indirect signs of tendinopathy. Direct visualization of tendons may be achieved by US, arthro-CT, arthro-MRI. US is a dynamic, non invasive and accurate technique for evaluation of rotator cuff tear but is very operator-dependent. Arthro-CT is more reproductive and reveals accurately partial tear as well as anterior tears involving biceps or subscapularis tendons. MRI is very useful to visualize the rotator cuff and adjacent bony structures. Nevertheless, MRI is still limited by its cost, accessibility and variable quality.

Arthrography↗

[Cine-MR in the assessment of the cardiovascular structures in extensive mediastinal pathology].

The authors report their experience with cine-MRI in evaluating the infiltration of the main cardiovascular structures by expansive mediastinal masses. Twenty-four patients with proven lung (12 cases) and mediastinal (12 cases) cancers, previously selected with CT, underwent MRI examination of the chest. A superconductive 1.0 T unit was employed. Cytohistologic confirmation was obtained in all cases (6 thymomas, 6 lymphomas, 12 lung cancers). Ten normal subjects were also studied as a control group. Axial, coronal, and sagittal SE T1 images were obtained as the basis for MRI investigation of the chest. Subsequently, gradient-echo pulse-sequences images were obtained during the whole cardiac cycle, and later displayed on cine-Mode, on the section plane where vessel wall was closest to the tumor. The results prove cine-MRI to allow a correct diagnosis to be made in all cases, especially in those patients where CT and conventional SE MRI yielded questionable results. This preliminary experience suggests that cine-MRI could be used as a complementary method to CT and conventional SE MRI in evaluating mediastinal vessel involvement.

Adolescent↗

Titanium wire internal fixation for stabilization of injury of the cervical spine: clinical results and postoperative magnetic resonance imaging of the spinal cord.

Nine patients with dislocation of the cervical spinal with posterior ligamentous damage were treated with posterior internal fixation using a twisted pair of 22-gauge titanium wires and iliac crest bone fusion. Fixation using the titanium wire was compared with fixation using stainless steel wire for differences in surgical insertion, long term stability of bony fusion, and postoperative magnetic resonance imaging (MRI) artifacts near the implanted wire. MRI of the cervical spine is valuable for diagnosing the acute and chronic consequences of traumatic cervical spinal injury by providing anatomic evaluation of both the spinal cord and the supporting bony/ligamentous structures in the neck. Because MRI is an accurate and sensitive noninvasive test, it is especially useful for the long-term serial assessment of the region near the cervical dislocation site to detect the sequelae of spinal cord injury, including syrinx, arachnoid cyst, cord tethering, and persistent mechanical impingement on the spinal cord or spinal roots. Previous attempts at our institution to obtain useful MRI scans of the cervical region adjacent to stainless steel wires after posterior wire fixation have failed due to marked imaging artifacts from the ferromagnetic properties of these wires. Our substitution of biocompatible titanium wire (Titanium 6 A1-4V ELI alloy, Specialty Steel and Forge, Leonia, New Jersey) for stainless steel wire produced identical immediate stabilization and ultimate bony fusion of the fracture and yielded minimal MRI artifacts overlying the immediately adjacent spinal cord and neural canal; however, the installation was technically more difficult, because of the titanium wire's greater stiffness.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

Ventricular enlargement in multiple sclerosis: a comparison of three-dimensional and linear MRI estimates.

Atrophy of central white matter is related to irreversible clinical disability in multiple sclerosis (MS) and ventricular enlargement may be a sensitive marker of this tissue loss. Therapeutic trials in MS have provided MRI data for investigation of cerebral atrophy in MS. These studies use almost exclusively two-dimensional (2-D) images, which may be limited in the assessment of three-dimensional (3-D) structures. We used 3-D MRI data to estimate ventricular volumes in 40 patients with MS and 10 healthy controls, to look at associations with clinical disability and the stage of the disease. We then compared simple linear measures of ventricular size from conventional 2-D images, with 3-D volume estimates to establish the best available linear indices of ventricular volume. Mean ventricular volumes were increased in the patients and significantly larger in the more disabled patients. The estimated volume of the third ventricle obtained from 3-D MRI showed the strongest association with the clinical stage of the disease, duration of symptoms and levels of disability. Finally, we confirmed that in patients with MS accurate data on ventricular size can be obtained from 2-D images by two simple and convenient linear measures, the width of the third ventricle and of the anterior horn of the lateral ventricle.

Adult↗

[Abdominal tumors in children. A comparison between magnetic resonance tomography (MRT) and ultrasonography (US)].

Twenty-one children with predominantly solid tumours detected by US were also examined by MRI (7 neuroblastomas, 2 Wilms tumours, 3 hepatoblastomas, 2 germinal cell tumours, 1 ganglioneuroblastoma, 1 gangliocytoma, 1 Cushing's adenoma, 1 phaeochromocytoma, 1 retroperitoneal rhabdomyosarcoma, 1 diffuse lymphangiectasia of a kidney, 1 splenunculus). The findings from both methods were compared with respect to the identification of the organ involved, extent of the tumour, effect on neighbouring structures and tissue characteristics. US and MRI were of equal value in defining the origin of the lesion and in demonstrating pathological enlargement of lymph nodes. Exact tumour extent could be better demonstrated with MRI because of the ability to perform multiplanar sections and to demonstrate intrathoracic and intraspinal spread. MRI was superior in 9 cases in demonstrating tumour structure and in 6 cases in the evaluation of vascular involvement and vascular anatomy. MRI is therefore recommended as an additional method to US for diagnosis and for treatment planning.

Abdomen↗

[3D FSPGR (fast spoiled gradient echo) magnetic resonance imaging in the diagnosis of focal cortical dysplasia in children].

Small dysplastic lesions of the cerebral cortex are often missed by conventional MRI methods. The identification of subtle structural abnormalities by traditional multiplanar rectilinear slices is often limited by the complex convolutional pattern of the brain. We used a method of FSPGR (fast spoiled gradient-echo) of three-dimensional MRI data that improves the anatomical display of the sulcal structure of the hemispheric convexities. It also reduces the asymmetric sampling of gray-white matter that may lead to false-positive results. We present 5 from 12 patients with dysplastic cortical lesions in whom conventional two-dimensional and three-dimensional MRI with multiplanar reformatting was initially considered normal. Subsequent studies using 3D FSPGR identified various types of focal cortical dysplasia in all. These results indicate that an increase in the detection of subtle focal dysplastic lesions may be accomplished when one improves the anatomical display of the brain sulcal structure by performing 3D FSPGR.

Adolescent↗

Optic nerve diffusion tensor imaging in optic neuritis.

Diffusion tensor magnetic resonance imaging (DT-MRI) provides in vivo information about the pathology of multiple sclerosis lesions. Increases in mean diffusivity (MD) and reductions in fractional anisotropy (FA) have been found and may represent axonal disruption. The optic nerve is an ideal structure for study by DT-MRI but previous clinical studies did not obtain the full diffusion tensor necessary to calculate MD and FA. In this study, a technique that was specifically developed to achieve full diffusion tensor measurements from the optic nerve (zonal oblique multislice (ZOOM) echoplanar imaging) was applied to 25 patients with a single unilateral episode of optic neuritis at least one year previously, and 15 controls. The intraorbital nerves were segmented on non-diffusion-weighted images and the regions of interest transferred to MD, FA, and eigenvalue maps to obtain quantitative data. Quantitative visual testing and electrophysiology were also performed. In affected nerves, mean MD and mean orthogonal eigenvalue lambda( perpendicular) were elevated, and mean FA reduced compared with clinically unaffected contralateral nerves (P < 0.001) and control nerves (P < 0.001). The mean principal eigenvalue lambda\\ was significantly increased in affected nerves compared to contralateral unaffected nerves (P = 0.04) but not compared to control nerves (P = 0.13). There was no association of clinical measures of visual function in affected eyes with the DT-MRI parameters but there was a significant correlation of the whole field visual evoked potential (VEP) amplitude with MD (r = -0.57, P = 0.006) and lambda( perpendicular) (r = -0.56, P = 0.007). These findings suggest that optic nerve DT-MRI measures provide an indication of the structural integrity of axons.

Adult↗

Hippocampal or neocortical lesions on magnetic resonance imaging do not necessarily indicate site of ictal onsets in partial epilepsy.

Advances in neuroimaging techniques, particularly high-resolution magnetic resonance imaging (MRI), have proved invaluable in identifying structural brain lesions in patients with epilepsy. The assumption that such focal lesions invariably predict the site of seizure origin may not be correct, however. We report a series of 20 adults with medically intractable partial epilepsy, where high-resolution brain MRI disclosed a unilateral, focal, hippocampal, or neocortical lesion as the only abnormality in each case; nevertheless, based on electroencephalographic (EEG) recordings, ictal onsets arose from a completely different location than that of the MRI lesion. All patients underwent epilepsy surgery, with the operations based on ictal EEG findings, and all were followed at least 2 years after the resection. After the most recent follow-up examination, 50% (10/20) of the patients were completely seizure-free, 35% (7/20) had at least a 75% reduction in the number of seizures, and 15% (3/20) had less than a 75% reduction in the number of seizures. We conclude that the identification of a focal, structural, hippocampal, or neocortical lesion on brain MRI is not always indicative of the site of seizure origin in partial epilepsy. Furthermore, in cases of discordance between MRI and EEG data, a good outcome after epilepsy surgery is possible if EEG ictal onsets are definitive.

Adolescent↗