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Key Points: The mechanisms for the age-related increase in fatigability during dynamic exercise remain elusive. We tested whether age-related impairments in muscle oxidative capacity would result in a greater accumulation of fatigue causing metabolites, inorganic phosphate (P i ), hydrogen (H + ) and diprotonated phosphate (H 2 PO 4 - ), in the muscle of old compared to young adults during a dynamic knee extension exercise. The age-related increase in fatigability (reduction in mechanical power) of the knee extensors was closely associated with a greater accumulation of metabolites within the working muscle but could not be explained by age-related differences in muscle oxidative capacity. These data suggest that the increased fatigability in old adults during dynamic exercise is primarily determined by age-related impairments in skeletal muscle bioenergetics that result in a greater accumulation of metabolites., Abstract: The present study aimed to determine whether the increased fatigability in old adults during dynamic exercise is associated with age-related differences in skeletal muscle bioenergetics. Phosphorus nuclear magnetic resonance spectroscopy was used to quantify concentrations of high-energy phosphates and pH in the knee extensors of seven young (22.7 ± 1.2 years; six women) and eight old adults (76.4 ± 6.0 years; seven women). Muscle oxidative capacity was measured from the phosphocreatine (PCr) recovery kinetics following a 24 s maximal voluntary isometric contraction. The fatiguing exercise consisted of 120 maximal velocity contractions (one contraction per 2 s) against a load equivalent to 20% of the maximal voluntary isometric contraction. The PCr recovery kinetics did not differ between young and old adults (0.023 ± 0.007 s -1  vs. 0.019 ± 0.004 s -1 , respectively). Fatigability (reductions in mechanical power) of the knee extensors was ∼1.8-fold greater with age and was accompanied by a greater decrease in pH (young = 6.73 ± 0.09, old = 6.61 ± 0.04) and increases in concentrations of inorganic phosphate, [P i ], (young = 22.7 ± 4.8 mm, old = 32.3 ± 3.6 mm) and diprotonated phosphate, [H 2 PO 4 - ], (young = 11.7 ± 3.6 mm, old = 18.6 ± 2.1 mm) at the end of the exercise in old compared to young adults. The age-related increase in power loss during the fatiguing exercise was strongly associated with intracellular pH (r = -0.837), [P i ] (r = 0.917) and [H 2 PO 4 - ] (r = 0.930) at the end of the exercise. These data suggest that the age-related increase in fatigability during dynamic exercise has a bioenergetic basis and is explained by an increased accumulation of metabolites within the muscle., (© 2019 The Authors. The Journal of Physiology © 2019 The Physiological Society.)

Purpose: Diffusion tensor imaging (DTI) plays a vital role in identifying white matter fiber bundles. Achievable imaging resolution and imaging time demands remain the major challenges in detecting small fiber bundles with current clinical DTI sequences., Methods: A novel reduced field of view ultra-high-resolution DTI technique named eZOOM (elliptically refocused zonally oblique multislice) was developed. A small circular disk was imaged using spatially selective radiofrequency (RF) pulses, reducing the imaging matrix size. The frequency profile of the spectral-spatial refocusing RF pulse provided intrinsic fat suppression, eliminating the need for fat saturation pulses., Results: Multislice DTI at a resolution of 0.35 × 0.35 mm in a celery fiber phantom was successfully performed by scanning an 8-cm field of view at 3T. An adequate diffusion-to-noise ratio (DNR >20) was achieved for a 25-min acquisition using a direct-sampling RF receiver. Human subjects (n = 7) were scanned at resolutions of 0.47 × 0.47 mm having a DNR <20 within a 75-min scanning time, requiring further enhancements to increase the signal-to-noise ratio., Conclusions: The new eZOOM-DTI method offers multislice DTI at ultra-high imaging resolutions substantially exceeding those available with current echo-planar DTI techniques. Parallel and fast spin echo methods can be combined with eZOOM to improve SNR and DNR in humans., (© 2014 Wiley Periodicals, Inc.)

A key challenge in upper extremity neuroprosthetics is variable levels of skill and inconsistent functional recovery. We examine the feasibility and benefits of using natural neuromotor strategies through the design and development of a proof-of-concept model for a feed-forward upper extremity neuroprosthetic controller. Developed using Artificial Neural Networks, the model is able to extract and classify neural correlates of movement intention from multiple brain regions that correspond to functional movements. This is unique compared to contemporary controllers that record from limited physiological sources or require learning of new strategies. Functional MRI (fMRI) data from healthy subjects (N = 13) were used to develop the model, and a separate group (N = 4) of subjects were used for validation. Results indicate that the model is able to accurately (81%) predict hand movement strictly from the neural correlates of movement intention. Information from this study is applicable to the development of upper extremity technology aided interventions.

Objective: To understand neural correlates of upper extremity task performance (functional vs. non-functional) and to understand their influence on neuromotor control strategies., Design: Cross-sectional descriptive study, with repeated measures., Setting: Medical center 1.5T MRI clinical imaging facility., Participants: Neurologically intact individuals, (M=14 F=5 mean age=22.94 ± 3.1 years) all right hand dominant as determined by the Edinburgh handedness survey. Subjects performed upper extremity motor tasks of reaching and grasping in a block paradigm. Whole brain fMRI data was acquired using a 1.5T MRI scanner., Main Outcome Measures: Differences in fMRI area of activation and maximum activation intensity for the whole brain were evaluated among the different upper extremity motor tasks., Results: Our results indicate (a) Activations in brain regions are task specific. (b) ANOVA results indicate functional goal oriented movements of reaching and grasping produce higher activation intensity (p < 0.0001) in more regions of the cortex (Somatosensory motor area, primary motor cortex, and parietal region) and cerebellum (p < 0.001) as compared to nonfunctional rhythmic movements of reaching only and grasping only. (c) There is some overlap in cerebellar activations, however areas of activation in the medial cerebellum were observed for reaching-and-grasping, while the grasping-only task produced activation more laterally in the cerebellum., Conclusions: Our findings suggest that (a) neuromotor strategy for functional goal-oriented movements is different from rhythmic movements such as finger tapping or non-functional movements, (b) This difference can be quantified and mapped using fMRI. (c) There are some overlap with activation of movement execution however the cognitive component that mediates the specific movement is not just the linear combination of simple movements rather it is task and context specific. (d) The results support the concept of using goal-oriented tasks in the applications of rehabilitation and therapy for restoration of function.

The ability to model and quantify brain activation patterns that pertain to natural neuromotor strategy of the upper extremities during functional task performance is critical to the development of therapeutic interventions such as neuroprosthetic devices. The mechanisms of information flow, activation sequence and patterns, and the interaction between anatomical regions of the brain that are specific to movement planning, intention and execution of voluntary upper extremity motor tasks were investigated here. This paper presents a novel method using symbolic dynamics (orbital decomposition) and nonlinear dynamic tools of entropy, self-organization and chaos to describe the underlying structure of activation shifts in regions of the brain that are involved with the cognitive aspects of functional upper extremity task performance. Several questions were addressed: (a) How is it possible to distinguish deterministic or causal patterns of activity in brain fMRI from those that are really random or non-contributory to the neuromotor control process? (b) Can the complexity of activation patterns over time be quantified? (c) What are the optimal ways of organizing fMRI data to preserve patterns of activation, activation levels, and extract meaningful temporal patterns as they evolve over time? Analysis was performed using data from a custom developed time resolved fMRI paradigm involving human subjects (N=18) who performed functional upper extremity motor tasks with varying time delays between the onset of intention and onset of actual movements. The results indicate that there is structure in the data that can be quantified through entropy and dimensional complexity metrics and statistical inference, and furthermore, orbital decomposition is sensitive in capturing the transition of states that correlate with the cognitive aspects of functional task performance.

The purpose of this study was to develop a voxel-wise analytical solution to a glioma growth model using serial diffusion MRI. These cell invasion, motility, and proliferation level estimates (CIMPLE maps) provide quantitative estimates of microscopic tumor growth dynamics. After an analytical solution was found, noise simulations were performed to predict the effects that perturbations in apparent diffusion coefficient values and the time between apparent diffusion coefficient map acquisitions would have on the accuracy of CIMPLE maps. CIMPLE maps were then created for 53 patients with gliomas with WHO grades of II-IV. MR spectroscopy estimates of the choline-to-N-acetylaspartate ratio were compared to cell proliferation estimates in CIMPLE maps using Pearson's correlation analysis. Median differences in cell proliferation and diffusion rates between WHO grades were compared. A strong correlation (R(2) = 0.9714) and good spatial correspondence were observed between MR spectroscopy measurements of the choline-to-N-acetylaspartate ratio and CIMPLE map cell proliferation rate estimates. Estimates of cell proliferation and diffusion rates appear to be significantly different between low- (WHO II) and high-grade (WHO III-IV) gliomas. Cell diffusion rate (motility) estimates are highly dependent on the time interval between apparent diffusion coefficient map acquisitions, whereas cell proliferation rate estimates are additionally influenced by the level of noise present in apparent diffusion coefficient maps., (Copyright © 2010 Wiley-Liss, Inc.)

Purpose: To determine the concurrence of activation in the primary motor cortex, induced by paradigms of active and passive movement of extremities, by using blood oxygen level-dependent functional magnetic resonance (MR) imaging., Materials and Methods: The HIPAA-compliant study was approved by the institutional review board, and written informed consent was obtained from the participating volunteers. Functional MR imaging data were collected from 11 healthy volunteers (four women, seven men; age range, 24-42 years) during active and passive movements of hand, elbow, shoulder, ankle, knee, and hip. These data were then mapped onto three-dimensional anatomic images. Volumes of activation were determined by using cross-correlation analysis at a coefficient threshold of 0.4 (P < .01). Regions of interest were drawn in pre- and postcentral gyri based on anatomic criteria. The mean number of activated voxels in the pre- and postcentral gyri induced by active and passive movements was compared by using Wilcoxon analysis. Concurrence ratios and proportional ratios of activation between active and passive movements were calculated for each somatotopic location., Results: Primary motor cortex activation tended to increase with active compared with passive movements, although in the precentral gyrus, hand, elbow, and shoulder movements showed no statistically significant difference in mean number of activated voxels. In the postcentral gyrus, only the shoulder revealed a significant difference (P < .05). Concurrence ratios (activation volume overlap of two tasks/combined activation area of both tasks) ranged from 0.44 to 0.57. Proportional ratios (activation volume overlap of passive task with active task/total activation volume of passive task) ranged from 0.64 to 0.82., Conclusion: Passive movement paradigms may be an alternative to or complement to active movement tasks in patient populations.

Seven HD gene positive individuals under the age of 21 years are described with clinical examination and proton-MR-spectroscopy ((1)H-MRS) profiles of the putamen. Despite clinical variability, the predominate (1)H-MRS abnormality is elevated glutamate, expressed well beyond the confines of the basal ganglia, and low striatal creatine., ((c) 2008 Movement Disorder Society.)

The nuclear magnetic resonance phenomenon has given rise to both magnetic resonance imaging, which yields morphologic data, and magnetic resonance spectroscopy (MRS), which yields chemical data. In humans these data are derived principally from the resonances of the hydrogen nucleus in the low molecular weight compounds in the body. Hydrogen MRS has become a routinely used clinical tool in the brain, prostate, and breast. Other nuclei also demonstrate this phenomenon but each of these comes with additional difficulties, including low abundance, low sensitivity, and/or low chemical concentrations. The future of MRS includes a drive to higher main magnetic field strengths and new methods to create 4-5 orders of magnitude greater signal. The future of MRS is bright, but in the United States it is endangered by overuse and misuse driven by the advent of reimbursement.

Objective: To assess the brain metabolites in the hippocampus of patients with mild cognitive impairment (MCI) using proton magnetic resonance spectroscopy at 0.5 T., Methods: Absolute concentrations and ratios to creatine of N-acetyl aspartate, myoinositol, glutamate + glutamine, and choline were measured in the right and left hippocampus of 5 MCI patients and 5 control subjects., Results: In MCI subjects, reduced N-acetyl aspartate was found in the right hippocampus (P = 0.01), and increased myoinositol was found in the left hippocampus (P = 0.02). Myoinositol/N-acetyl aspartate ratios were higher in the right (P = 0.03) and left (P = 0.01) hippocampus of MCI subjects. No significant difference in the concentration of glutamate + glutamine was observed between the control and MCI groups., Conclusions: An increase in myoinositol and a decrease in N-acetyl aspartate may be observed in the preclinical stages of dementia. Ratio measurements of these metabolites may serve as a biomarker for MCI.

A 43-year-old man presented with a grade II astrocytoma in the left postcentral gyrus and superior parietal lobule. Preoperative functional MR imaging and diffusion tensor imaging mapped distal upper-extremity primary motor cortex and white matter, respectively, adjacent to the tumor, within a congenitally truncated precentral gyrus. Because of the congenital anomaly, this region of primary motor cortex was inaccessible to direct visualization or intraoperative electrocortical stimulation. The integration of preoperative and intraoperative mapping data facilitated resection of the tumor while avoiding a postoperative motor deficit.

Objective: The purpose of this study was to determine whether a saline bolus during CT urography improves urinary collecting system opacification and whether the addition of enhanced CT digital radiography (CTDR) improves urinary collecting system visualization with or without a saline bolus., Materials and Methods: One hundred eight CT urography and enhanced CTDR examinations were reviewed. Fifty-four patients were given a saline bolus during CT urography, and 54 patients underwent CT urography without a saline bolus. Urinary collecting system opacification was evaluated by group (saline vs nonsaline), imaging technique (CT urography alone vs CT urography plus enhanced CTDR), number of enhanced CTDR images, and site of nonopacified urinary segments. Using a multivariate logistic regression model, we determined significance of variables and odds of complete opacification., Results: In the saline group, 248 nonopacified sites were identified on CT urography alone and 95 sites with CT urography plus enhanced CTDR. In the nonsaline group, 185 nonopacified sites were identified on CT urography alone and 59 sites with CT urography plus enhanced CTDR. Combining both groups, 433 nonopacified sites were identified with CT urography alone and 154 sites with CT urography plus enhanced CTDR. Multivariate logistic regression showed significance for group (p = 0.010), imaging method (p < 0.0001), number of enhanced CTDR images (p = 0.048), and site of segment opacification (p < 0.0001). The renal pelvis shows the greatest odds and the distal ureter the lowest odds for complete opacification by group or imaging method., Conclusion: The addition of a saline bolus offers no improvement, whereas the addition of enhanced CTDR offers significant improvement in collecting system opacification during CT urography.

Diffusion tensor imaging (DTI) using a combination of direct anisotropy measurements provided a more anatomically accurate morphological representation of the human spinal cord than traditional anisotropy indices. Furthermore, the use of a fuzzy logic algorithm to segment regions of gray and white matter within the spinal cord based on these anisotropy measurements allowed for morphometric analyses. Results indicated a significant decrease in overall spinal cord cross-sectional area, dorsal funiculus cross-sectional area, and lateral funiculi cross-sectional area in subjects with injury compared to the neurologically intact control subjects. Results also showed individuals with caudal injuries had a morphology and morphometry that was more similar to that of the control subjects, which is consistent with the process of Wallerian degeneration and has been illustrated by previous investigations involving animal surrogates.

Background: The present study evaluated volumetric changes in the aging midface. Both young and old living subjects were studied using high-resolution magnetic resonance imaging (MRI) to investigate the distribution and volume of the muscle and subcutaneous components of the midface., Methods: MRI with a customized radiofrequency coil was performed in 20 healthy Caucasian female volunteers equally divided between young (16 to 30 years) and old (>59 years) age groups. Sagittal oblique images were obtained at 1-mm intervals through the midface, perpendicular to the nasolabial fold. Quantitative analyses of the cheek fat pad overlying the levator labii superioris and zygomaticus major muscles were performed separately., Results: For both mimetic muscles, there were no significant differences between young and old subjects in muscle length, thickness, or volume from muscle origin to nasolabial fold. In addition, there were no significant differences between age groups in fatty infiltration of the muscles. The volumes of the medial and lateral aspects of the cheek fat pad were significantly greater in old than in young subjects (p < 0.05). In young subjects the greatest distribution of fat pad volume was found in the middle third of the cheek mass. There was a significant reduction in that portion of the fat pad distributed in the upper third and a further reduction in the lower third (p < 0.01). In old subjects, because of the increased distribution of fat in the upper third of the cheek fat pad, there was no significant difference in volume between the upper and middle thirds of the cheek fat pad. The percentage increase in fat in the upper third relative to the remainder of the midface was significantly greater in old compared with young subjects (p < 0.01). In contrast, the volume of the lower third of the midface was not significantly different between young and old subjects., Conclusions: The present study indicates that ptosis alone does not account for the changes observed in the aging midface. Selective hypertrophy of the upper portion of the cheek fat pad was also observed. The mimetic muscles, on the other hand, showed no significant differences with aging. To attain maximum precision in facial rejuvenation, these data suggest that after suspension of the ptotic cheek fat pad, each patient should be evaluated for excess bulk in the upper portion of the cheek fat pad. If excess bulk is present, patients may benefit further from selective reduction directed to the upper portion of the cheek fat pad, remaining superficial to the mimetic muscles of the face.

Objective: To evaluate (1)H-MRS profiles of the putamen in presymptomatic and manifest Huntington's disease (HD) patients for spectroscopic markers that are reliable, consistent signs of early pathology and to look for hemispheric differences as signs of use activation in an accelerated degradative process of the dominant hemisphere., Methods: A short echo time Point RESolved Spectroscopy (PRESS) spectroscopic imaging study was performed at low field (0.5 Tesla, T) on 27 right-handed patients (17 presymptomatic gene carriers and 10 manifest patients of less than 3 years from clinical onset) and 10 right-handed normal volunteers. Spectra from individual voxels (0.56 cm(3)) in the putamen were selected for analysis. Resonance areas of peaks were normalized to water as a concentration standard. Interhemispheric comparisons were made in individuals in all three groups to look for hemispheric differences., Results: Two presymptomatic patients showed normal spectra but all other HD patients displayed some combination of reduced N-acetylaspartate (NAA), enhanced glutamate/glutamine (Glx) activity, and lactate (Lac) elevations or reduced creatine (Cr). Rather than showing any one metabolite as pathognomonic of early change, spectroscopic profiles showed heterogeneity between HD patients. Low creatine was common in the presymptomatic but not in the manifest group. Hemispheric ratios of abnormal metabolites showed lower values of NAA and Glx in the dominant hemisphere in all three groups but values of creatine were selectively lower in the dominant hemisphere of only the presymptomatic patients. Lac was elevated in both hemispheres but less so in the dominant hemisphere in all HD patients., Conclusions: (1)H-MRS profiles from the putamen of presymptomatic and manifest patients reflect heterogeneity in pathophysiology. With the possible exception of low creatine in presymptomatic patients (1)H-MRS spectra are not suggestive of hemispheric differences supportive of an overall accelerated degradative process in the dominant hemisphere.

Sensitivity-encoded spectroscopic imaging (SENSE-SI) reduces scanning time by using multiple coils for parallel signal acquisition. Significant artifacts could be induced by SENSE-SI, mainly due to the low-resolution nature of spectroscopic imaging. The present study introduces a novel method to reduce the artifacts. High-resolution sensitivity maps are used in low-resolution SENSE reconstruction. An intermediate unaliased image is obtained after SENSE reconstruction. Based on the intermediate image, the sensitivity maps are optimized and then the SENSE reconstruction is performed again. The final unaliased image has significantly reduced artifacts., (Copyright 2004 Wiley-Liss, Inc.)

Diffusion Tensor Imaging (DTI) is a new MRI imaging technique sensitive to directional movements of water molecules, induced by tissue barriers. This provides a new form of contrast that allows the identification of functional white matter tracts within the brain, and has been proposed as a technique suitable for presurgical planning in brain tumor patients. Resection of primary brain tumors improves survival, functional performance, and the effectiveness of adjuvant therapies, provided that surgically-induced neurological deficits can be avoided. Diffusion Tensor Imaging (DTI) has the potential to establish spatial relationships between eloquent white matter and tumor borders, provide information essential to preoperative planning, and improve the accuracy of surgical risk assessments preoperatively. We present our experience in a series of 28 brain tumor patients where the integration of functional magnetic resonance imaging (fMRI) and DTI data was used to determine key anatomic spatial relationships preoperatively. Twice as many functional systems were localized to within 5 mm of tumor borders when DTI and fMRI were utilized for preoperative planning, compared to that afforded by fMRI alone. Our results show that the combined use of fMRI and DTI can provide a better estimation of the proximity of tumor borders to eloquent brain systems sub-serving language, speech, vision, motor and premotor functions. Additionally, a low regional complication rate (4%) observed in our series suggests that preoperative planning with these combined techniques may improve surgical outcomes compared to that previously reported in the literature. Larger studies specifically designed to establish the accuracy and predictive value of DTI in brain tumor patients are warranted to substantiate our preliminary observations.

Objective: To illustrate how lesion-induced neurovascular uncoupling at functional magnetic resonance imaging (fMRI) can mimic hemispheric dominance opposite the side of a lesion preoperatively., Methods: We retrospectively reviewed preoperative fMRI mapping data from 50 patients with focal brain abnormalities to establish patterns of hemispheric dominance of language, speech, visual, or motor system functions. Abnormalities included gliomas (31 patients), arteriovenous malformations (AVMs) (11 patients), other congenital lesions (4 patients), encephalomalacia (3 patients), and tumefactive encephalitis (1 patient). A laterality ratio of fMRI hemispheric dominance was compared with actual hemispheric dominance as verified by electrocortical stimulation, Wada testing, postoperative and posttreatment deficits, and/or lesion-induced deficits. fMRI activation maps were generated with cross-correlation (P < 0.001) or t test (P < 0.001) analysis., Results: In 50 patients, a total of 85 functional areas were within 5 mm of the edge of a potentially resectable lesion. In 23 of these areas (27%), reduced fMRI signal in perilesional eloquent cortex in conjunction with preserved or increased signal in homologous contralateral brain areas revealed functional dominance opposite the side of the lesion. This suggested possible lesion-induced transhemispheric cortical reorganization to homologous brain regions (homotopic reorganization). In seven patients, however, the fMRI data were inconsistent with other methods of functional localization. In two patients with left inferior frontal gyrus gliomas and in one patient with focal tumefactive meningoencephalitis, fMRI incorrectly suggested strong right hemispheric speech dominance. In two patients with lateral precentral gyrus region gliomas and one patient with a left central sulcus AVM, the fMRI pattern incorrectly suggested primary corticobulbar motor dominance contralateral to the side of the lesion. In a patient with a right superior frontal gyrus AVM, fMRI revealed pronounced left dominant supplementary motor area activity in response to a bilateral complex motor task, but right superior frontal gyrus perilesional hemorrhage and edema subsequently caused left upper-extremity plegia. Pathophysiological factors that might have caused neurovascular uncoupling and facilitated pseudo-dominance at fMRI in these patients included direct tumor infiltration, neovascularity, cerebrovascular inflammation, and AVM-induced hemodynamic effects. Sixteen patients had proven (1 patient), probable (2 patients), or possible (13 patients) but unproven lesion-induced homotopic cortical reorganization., Conclusion: Lesion-induced neurovascular uncoupling causing reduced fMRI signal in perilesional eloquent cortex, in conjunction with normal or increased activity in homologous brain regions, may simulate hemispheric dominance and lesion-induced homotopic cortical reorganization.

Objective: Magnetic resonance imaging (MRI) has been contraindicated when cochlear implants containing an internal magnet are in place because of concerns regarding torque, force, demagnetization, artifacts, induced voltages, and heating. The objective was to determine the magnetic field strength of Med-El Combi 40+ cochlear implant internal magnets after MRI studies., Study Design/methods: Two fresh cadavers were used to study demagnetization using a repeated measures design and a magnetometer. Pre- and postMRI measurement of magnetic field strength was completed. Five sets of sagittal T1-weighted, axial T1-weighted, and axial T2-weighted sequences were performed on a cadaver at 0.2 Tesla in the device-up and device-down positions. In the other cadaver, 15 sets of sagittal T1-weighted, axial T1-weighted, and axial T2-weighted sequences were performed on a cadaver at 1.5 Tesla were conducted, 5 each with the head oriented at 80, 90, and 100 degrees rotated around the yaw plane (rotated around the z-axis). Subsequently, three cochlear implant patients completed 0.2 Tesla MRIs. For these patients, subjective and objective assessment of cochlear implant performance was performed., Setting: Academic medical center., Results: In the cadaver studies, analysis of variance showed no significant difference in the magnetic field strength after the 0.2 or 1.5 Tesla scans. There was no significant difference in the magnetic field strength for the three patients undergoing 0.2 Tesla MRIs and no adverse consequences, including no changes in telemetry, auditory sensations, nonauditory sensations, and sound quality., Conclusions: No significant demagnetization of the internal magnet occurred during repeated 1.5 Tesla MRI scans with the head orientations used in this study. In the cochlear implant patients, no significant demagnetization of the internal magnet occurred after a 0.2 Tesla MRI.

We present a case of a 64-year-old, right-handed female with a metastatic breast cancer lesion involving the left posterior inferior temporal lobe causing complete loss of the ability to recognize visually common objects and words. After her symptoms resolved on corticosteroid therapy, functional magnetic resonance imaging (fMRI) mapping demonstrated strong left-hemispheric dominance for word recognition and right-hemispheric dominance for object recognition. The case illustrates the relationships among ventral occipito-temporal cortical activation, lesion localization, and lesion-induced deficits of higher visual function. The relationship between hemispheric dominance determined by fMRI and risk of postoperative deficit depends on the specific visual function of interest.

Detection of short T2 metabolites such as glutamate and glutamine (glx) in the brain can be improved by minimizing the echo time (TE) of the pulse sequence. By combining two dimensions of localization during a single radiofrequency (RF) pulse, an elliptic excitation chemical shift imaging sequence (EECSI) that further reduces TE by a factor of 2 relative to a TE-optimized point resolved spectroscopy sequence chemical shift imaging sequence was developed. An additional set of outer volume saturation pulses is included to minimize the contamination from scalp and marrow space lipids. The sequence runs with conventional gradient hardware (1 G/cm, 17 T/m/s slew rate) at 0.5 T. The increase in the fitted areas of beta,gamma multiplet of glutamate and glx in a brain-mimicking phantom was by a factor of 1.66. In the thalamus of healthy volunteers, glx was increased by 1.44. Combined with the field strength-related improvements in glutamate and glx detection previously demonstrated at 0.5 T, EECSI offers further improvements for imaging glutamate and glx in vivo.

Purpose: The purpose of this study was to investigate the activation patterns of the primary auditory cortex in response to varying intensities of pure tone stimuli., Method: A 1,000-Hz pure tone stimulus was delivered monaurally to the right ear of 12 normal-hearing right-handed volunteers in 20-second on-off cycles. Stimuli were applied at 20 and 50 dB hearing level (HL) above threshold in 12 subjects and at 0, 20, 40, and 50 dB HL above threshold in 6 subjects. Functional magnetic resonance imaging (fMRI) data were obtained using a 1.5-T scanner and echoplanar imaging. Activated pixels were identified in the transverse temporal gyrus (TTG) of both hemispheres in response to pure tone stimuli at each intensity level using cross-correlation analysis (0.6; P < 0.0001)., Results: Of the 24 right and left TTGs imaged (n = 12), activation to pure tone stimuli at 20 and 50 dB HL above threshold was seen in 46% and 79% of TTGs, respectively, with bilateral hemispheric activation in 27% and 64% of subjects, respectively. The mean numbers of activated voxels were 4.0 and 13.0, respectively. Of the 12 right and left TTGs imaged at 0, 20, 40, and 50 dB HL above threshold, activation was seen in 33%, 42%, 58%, and 75% of TTGs, respectively. The mean numbers of activated voxels were 5.8, 3.2, 9.8, and 15.3, respectively. There was a nonsignificant trend toward contralateral (left) dominant TTG activation with increased tone intensity., Conclusion: Our results show an increased likelihood of TTG activation, increased TTG activation volume, and increased bilateral hemisphere TTG activation with increasing pure tone intensity. Our results suggest that the primary auditory cortex reflects or is directly involved in the central processing of sound intensity and that varying the intensity of even simple stimuli can alter the patterns of fMRI activation in auditory cortex.

Objective/hypothesis: The forces exerted during a 1.5-Tesla MRI evaluation on the internal magnet of a cochlear implant (CI) raise concern about the safety for CI recipients. This study determines the magnitude of force required to fracture the floor of a CI receiver bed., Method: Recessed CI beds were drilled to maximum uniform thinness into formalin-fixed and fresh-frozen human calvaria specimens. A Med-El stainless steel CI template mounted to the piston of an electrohydraulic testing device was used to fracture the floor of the implant beds. Force and displacement were measured as a function of time using a digital data acquisition system., Results: Mean force to first failure, displacement to first failure, and minimum thickness, respectively, were: group 1 (formalin-fixed, 0.3-0.4-mm thick [n = 22]), 34.08 N (8.21-59.64 N, standard deviation [SD] 15.41 N), 1.09 mm (0.40-2.16 mm, SD 0.51 mm), 0.36 mm (0.3-0.4 mm, SD 0.05 mm); group 2 (formalin-fixed, 0.5-0.9 mm thick [n = 21]), 52.82 N (20.28-135.53 N, SD 25.29 N), 1.08 mm (0.50-2.28 mm, SD 0.47 mm), 0.58 mm (0.5-0.9 mm, SD 0.12 mm); group 3 (fresh-frozen [n = 9]), 134.13 N (86.44-190.70 N, SD 34.92 N), 1.96 mm (1.47-2.46 mm, SD 0.35 mm), 0.42 mm (0.3-0.6 mm, SD 0.11 mm)., Conclusions: The mean magnitude of force required to fracture the floor of a CI bed is significantly greater than those that are generated when a Med-El Combi 40+, CII Bionic Ear CI, or Nucleus Contour CI is placed into a 1.5-Tesla MRI unit.

Single photon emission computerized tomography (SPECT) studies were performed on 34 manifest Huntington's disease (HD) patients at various stages of clinical pathology ranging from early chorea to late dystonia with or without signs of dementia and 12 pre-symptomatic patients with abnormal terminal CAG expansions. Thirty HD patients with obvious clinical signs and seven pre-symptomatic patients without signs or symptoms of HD displayed selective caudate hypoperfusion by direct visual inspection. Such qualitative, selective striatal hypoperfusion patterns can be indicative of early and persistent metabolic changes in striatal neuropathology. SPECT studies can be useful in documenting early pre-clinical changes in patients with abnormal terminal CAG expansions and in confirming the presence of caudate pathology in patients with clinical signs of HD.

Proton magnetic resonance spectroscopy (MRS) may be a useful tool in both the initial diagnosis of cervical carcinoma and the subsequent surveillance after radiation therapy, particularly when other standard diagnostic methods are inconclusive. Single voxel magnetic resonance (MR) spectral data were acquired from 8 normal volunteers, 16 patients with cervical cancer before radiation therapy, and 18 patients with cervical cancer after radiation therapy using an external pelvic coil at a 1.5-T on a Signa system. The presence or absence of various resonances within each spectrum was evaluated for similarities within each patient group and for spectral differences between groups. Resonances corresponding to lipid and creatine dominated the spectrum for the eight normal volunteers without detection of a choline resonance. Spectra from 16 pretreatment patients with biopsy-proven cervical cancer revealed strong resonances at a chemical shift of 3.25 ppm corresponding to choline. Data acquired from the 18 posttreatment setting studies was variable, but often correlated well with the clinical findings. Biopsy confirmation was obtained in seven patients. H1 MRS of the cervix using a noninvasive pelvic coil consistently demonstrates reproducible spectral differences between normal and neoplastic cervical tissue in vivo. However, signal is still poor for minimal disease recurrence. Further study is needed at intervals before, during, and after definitive irradiation with biopsy confirmation to validate the accuracy of MRS in distinguishing persistence or recurrence of disease from necrosis and fibrosis.

An interleaved gradient-echo (GE) / spin-echo (SE) EPI sequence was used to acquire images during the first pass of a susceptibility contrast agent, in patients with brain tumors. Maps of 1) GE (total) rCBV (relative cerebral blood volume), 2) SE (microvascular) rCBV, both corrected for T(1) leakage effects, and 3) (DeltaR(2)*/DeltaR(2)), a potential marker of averaged vessel diameter, were determined. Both GE rCBV and DeltaR(2)*/DeltaR(2) correlated strongly with tumor grade (P = 0.01, P = 0.01, n = 15), while SE rCBV did not (P = 0.24, n = 15). When the GE rCBV data were not corrected for leakage effects, the correlation with tumor grade was no longer significant (P = 0.09, n = 15). These findings suggest that MRI measurements of total blood volume fraction (corrected for agent extravasation) and DeltaR(2)*/DeltaR(2), as opposed to maps of microvascular volume, may prove to be the most appropriate markers for the evaluation of tumor angiogenesis (the induction of new blood vessels) and antiangiogenic therapies. Magn Reson Med 43:845-853, 2000., (Copyright 2000 Wiley-Liss, Inc.)

Spin-lock imaging is a new magnetic resonance imaging (MRI) technique used to reflect the microstructural integrity of muscle. The purpose of this study was to characterize spin-lock contrast (SLC) of calf muscles in limb girdle muscular dystrophy (LGMD). The calf muscles of 5 patients with LGMD and 10 healthy volunteers were imaged with an off-resonance magnetic resonance (MR) spin-lock suppression pulse. Spin-lock suppression ratios were calculated for anterior tibialis, posterior tibialis, soleus, and gastrocnemius muscles. Clinical assessments of muscle strength were compared to the spin-lock suppression ratios in the LGMD group. Strong SLC was observed in healthy muscles, with mean (+/- SD) suppression ratios ranging from 51.2% (+/- 3.6%) to 56.3% (+/- 1.3%). In diseased muscle, spin-lock signal suppression was reduced by 8%-70%, demonstrating an inverse correlation between symptom duration and suppression ratios. Spin-lock contrast in the patients with LGMD, as a reflection of tissue integrity, was best preserved in posterior tibialis, anterior tibialis, soleus, and gastrocnemius muscles in descending order. Clinical assessments did a poorer job of differentiating than SLC did and were in poor agreement with spin-lock suppression ratios. Spin-lock MRI can quantify microstructural changes in LGMD and appears to provide information not obtainable from clinical evaluations. This suggests that this noninvasive technique may be useful in evaluating the extent, progression, and response to therapy of LGMD.

Purpose: The purpose of this work was to characterize magnetization transfer (MT) contrast of skeletal muscles in limb girdle muscular dystrophy (LGMD)., Method: The calf muscles of five LGMD patients and 10 normal volunteers were imaged with an off-resonance MT suppression pulse applied to T1-weighted images. MT suppression ratios were calculated for anterior tibialis, posterior tibialis, soleus, and gastrocnemius muscles in the LGMD and control groups. The relationship between MT of individual muscles and the duration of LGMD symptoms was determined., Results: Strong MT contrast was observed in normal calf muscles, with mean (+/-SD) suppression ratios ranging from 37.9% (+/-3.0) to 41.1% (+/-2.1). In diseased muscle, MT signal suppression ranged from 11 to 38%, demonstrating an inverse relationship between symptom duration and suppression ratios. MT contrast in the LGMD patients, as a reflection of muscle tissue integrity, was preserved in posterior or anterior tibialis, soleus, and gastrocnemius muscles, respectively. Suppression ratios were dramatically reduced in muscles with gross fatty infiltration but also were reduced in muscle tissues without visual evidence of fatty infiltration., Conclusion: MT imaging provides a quantitative measure of pathologic changes occurring within the skeletal muscles of patients with LGMD relative to normal and may be useful in evaluating disease extent, progression, and response to new therapies as they become available.

Purpose: To determine the influence of single-voxel proton magnetic resonance (MR) spectroscopic findings on the treatment of patients suspected of having a brain tumor., Materials and Methods: Medical records were reviewed in 78 patients who underwent MR spectroscopy for evaluation of a focal brain mass suspected of being neoplastic. MR spectroscopic findings were positive for neoplasm in 49 patients and negative in 29. Treatment with or without performance of biopsy was noted. In patients with positive findings who underwent irradiation or chemotherapy without biopsy and in patients with negative findings who were treated medically or followed up for interval changes, MR spectroscopy was classified as having a potential positive influence on treatment. In patients with positive findings with subsequently proved nonneoplastic lesions and in patients with negative findings with subsequently proved tumors, MR spectroscopy was classified as having a potential negative influence., Results: MR spectroscopy in eight (16%) patients with positive findings and in 15 (52%) patients with negative findings had a potential positive influence on treatment. In two (3%) patients, MR spectroscopy had a potential negative influence., Conclusion: MR spectroscopy may play a beneficial role in the management of suspected brain tumors. Prospective studies are needed to test the effect of MR spectroscopy on clinical practice and to measure costs and benefits.

Background and Purpose: MR spectroscopy is used to characterize biochemical components of normal and abnormal brain tissue. We sought to evaluate common histologic findings in a diverse group of nonneoplastic diseases in patients with in vivo MR spectroscopic profiles suggestive of a CNS neoplasm., Methods: During a 2-year period, 241 patients with suspected neoplastic CNS lesions detected on MR images were studied with MR spectroscopy. Of these, five patients with a nonneoplastic diagnosis were identified retrospectively; a sixth patient without tissue diagnosis was added. MR spectroscopic findings consistent with a neoplasm included elevated choline and decreased N-acetylaspartate and creatine, with or without detectable mobile lipid and lactate peaks., Results: The histologic specimens in all five patients for whom tissue diagnoses were available showed significant WBC infiltrates, with both interstitial and perivascular accumulations of lymphocytes, macrophages, histiocytes, and (in one case) plasma cells. Reactive astrogliosis was also prominent in most tissue samples. This cellular immune response was an integral component of the underlying disorder in these patients, including fulminant demyelination in two patients, human herpesvirus 6 encephalitis in one patient, organizing hematoma from a small arteriovenous malformation in one patient, and inflammatory pseudotumor in one patient. Although no histologic data were available in the sixth patient, neoplasm was considered unlikely on the basis of ongoing clinical and neuroradiologic improvement without specific therapy., Conclusion: Nonneoplastic disease processes in the CNS may elicit a reactive proliferation of cellular elements of the immune system and of glial tissue that is associated with MR spectroscopic profiles indistinguishable from CNS neoplasms with current in vivo MR spectroscopic techniques. Such false-positive findings substantiate the need for histologic examination of tissue as the standard of reference for the diagnosis of intracranial mass lesions.

Purpose: We examined the utility of near-resonance saturation pulse imaging (magnetization transfer [MT] and spin lock) in characterizing microstructural changes occurring in the extraocular muscles of patients with thyroid-related ophthalmopathy (TRO)., Methods: Eight healthy volunteers and 10 patients with TRO were imaged using an off-resonance saturation pulse in conjunction with conventional spin-echo T1-weighted imaging at frequency offsets of 500, 1000, 1500, and 2000 Hz from water resonance. The relative contributions of MT and spin-lock excitation to image contrast at each frequency offset were estimated using a computer simulation model. Suppression ratios were calculated for the control and TRO groups from measurements obtained on two successive coronal sections in the widest portion of the inferior and medial rectus muscles bilaterally. A repeated measures analysis of variance and a parametric correlation analysis were performed to evaluate maximum cross-sectional area, MR-generated signal, and suppression ratios for the extraocular muscles examined., Results: Our computer model suggested that saturation of extraocular muscles was due to pure MT effects with our off-resonance pulse at 2000 and 1500 Hz, to a combination of MT and spin lock at 1000 Hz frequency offset, and, primarily, to spin-lock excitation at 500 Hz frequency offset. Suppression ratios for the extraocular muscles of the TRO patients were significantly lower than that observed for the control subjects at 1500, 1000, and 500 Hz frequency offset. This differential saturation effect was maximal at 500 Hz frequency offset, with mean suppression ratios for the inferior and medial rectus muscles of 27% for the healthy subjects and 20% for the TRO group., Conclusion: Both MT and spin-lock contrast of the extraocular muscles in patients with TRO differ significantly from that observed in control subjects. Near-resonance saturation pulse imaging may enhance our understanding of the microstructural changes occurring in the extraocular muscles of these patients.

Purpose: Our goal was to determine the effects of acoustic echoplanar scanner noise on pure tone hearing thresholds in normal volunteers and to determine the influence of echoplanar sequence repetition time on threshold effects., Method: With use of a calibrated audiometer, pure tones ranging from 125 to 8,000 Hz were delivered monaurally to 10 normal-hearing volunteers in a quiet MR scanner suite and in the presence of acoustic scanner noise produced by three separate single shot blipped echoplanar pulse sequences varying only in repetition time (TR = 1,000, 2,000, or 3,000 ms), with all other parameters including the number of slices held constant. The magnitude of noise-induced threshold changes and the slopes of the threshold curves produced by each of the three echoplanar pulse sequences were then analyzed using multiple comparisons and a least significant difference method. The shapes of the threshold curves produced in each background state were best fit using a quadratic effect for frequency in a mixed effects linear model and compared using F test statistics., Results: All of the volunteers demonstrated entirely normal hearing thresholds throughout the full range of tonal frequencies tested (< 25 dB) when no acoustic scanner noise was present in the scanner suite. Pure tone hearing thresholds significantly increased (p < 0.01) in the presence of acoustic scanner noise, with the magnitude of change inversely proportional to the repetition time and therefore the rate of periodic noise production by the echoplanar sequence used. The shape of the threshold curve in the presence of noise produced by the 1,000 ms TR sequence was not equivalent across the frequency spectrum tested but had a quadratic distribution with peak effects at 750-2,000 Hz. As the repetition time was increased and the periodic noise rate decreased, the magnitude of the noise-induced threshold changes significantly lessened (p < 0.01) and the quadratic distributions of the threshold curves changed significantly (p < 0.01), tending toward a more planar configuration., Conclusion: Background acoustic echoplanar scanner noise can significantly increase pure tone thresholds in the optimal frequency hearing range (125-8,000 Hz). However, the threshold effects are not equivalent across the frequency spectrum, and the magnitude of threshold changes is dependent on the rate at which periodic acoustic scanner noises are produced for a given sequence repetition time.

Purpose: Our goal was to determine the distribution of auditory and language cortex activation in response to acoustic echo planar scanner noise with functional MRI (fMRI)., Method: Acoustic scanner noise and spoken text, reproduced on high output cassette tape, were separately delivered at equivalent intensities to six normal hearing adult volunteers through earphones during fMRI data acquisition. In nine other subjects, taped scanner noise was delivered in five successive iterations of the task to assess the consistency of cortical activation to the noise stimulus. Gyri of the auditory and language system were divided into 10 different subregions for analysis of cortical activation. The number of activated pixels and proportion of volunteers activating each cortical subregion were determined using a cross-correlation analysis., Results: Cortical activation to taped acoustic scanner noise was present within the transverse temporal gyrus (primary auditory cortex) in all subjects, but activation was highly variable between subjects in auditory association and language relevant cortex. Auditory association cortex activation was seen in the planum polari, planum temporali, and middle temporal gyrus/superior temporal sulcus regions in one-half to two-thirds of the volunteers. There was no significant difference in the distribution of cortical activation within individual subjects across five successive iterations of the scanner noise task. Listening to spoken text consistently activated primary and association auditory cortex bilaterally as well as language relevant cortex in some cases. The mean number of activated pixels was significantly greater for text listening than acoustic scanner noise in auditory association and language relevant cortical subregions (p < 0.01), although the distribution of activity was similar between the two tasks., Conclusion: This preliminary investigation suggests that the complex sounds produced by the echo planar pulse sequence can activate relatively large regions of auditory and language cortex bilaterally, with the extent of activation outside the primary auditory cortex being variable between subjects. However, the distribution of activation within individual subjects was relatively constant across several iterations of the scanner noise stimulus.

MRS extends the diagnostic power of MRI by displaying the biochemical composition of a selected tissue or region. When MR imaging shows a lesion, the evaluation of the chemical composition by MRS can help determine whether biopsy, observation or medical treatment is indicated. It can save some patients from biopsy prior to radiation or chemotherapy. In the future, both the image information and the spatial distribution of chemical constituents throughout the brain will be displayed with techniques such as chemical shift imaging (CSI). MRS improves the accuracy of MRI diagnosis and prognosis. MRS is performed at many sites in the country and is reimbursed by many insurers. MRS has been approved by the AMA for a CPT-4 code for reimbursement.

Midfield proton magnetic resonance spectroscopy (MRS) provides a noninvasive method to monitor glutamate and glutamine (Glx) levels in vivo. Experiments to detect the gamma and beta resonances of Glx have been performed by using commercial 0.5 T and 1.5 T MR scanners on seven patients with elevated blood ammonia and eight normal volunteers. Compared with the spectral sensitivity obtained on an otherwise identical system operating at 1.5 T, the singlet resonance of N-acetyl aspartate (NAA) was decreased by a factor of 1.48, which is significantly less than expected using the ratio of Boltzman populations at the two field strengths. However, the resonances of Glx at 0.5 T increased in signal-to-noise ratio (SNR) by a factor of 2. The increased SNR of Glx is principally due to improved B0 main-field homogeneity and collapse of the strongly J-coupled Glx resonances. Our preliminary results suggest that midfield proton MRS will provide significant clinical utility in the detection of Glx levels in human brain.

To determine the ability of fast gradient-recalled echo (GRE), breath-hold magnetic resonance imaging (MRI) to depict all regions of the diaphragm, 13 volunteers were scanned in coronal and sagittal planes. The central to anterior left hemidiaphragm and the posterior lumbar portions were each demonstrated in 12 subjects (92%). The crura were visible crossing anterior to the aorta in the sagittal plane in eight subjects (62%) and in the coronal plane in six subjects (46%). In the sagittal plane, the right crus was evident in eight subjects (62%). Muscular portions of the diaphragm in contact with the liver or body wall were less frequently discernible, and the central tendon could not be confidently resolved. Several artifacts occurred that interfered with visualization of the diaphragm. These observations indicate that many regions of the diaphragm can be seen with fast GRE, breath-hold MRI, but there are some limitations in depicting the diaphragm in its entirety.

Purpose: To investigate the cause of the trilaminar appearance within hyaline cartilage observed on magnetic resonance (MR) images obtained with a fat-suppressed three-dimensional spoiled gradient-recalled sequence., Materials and Methods: The knees of three asymptomatic volunteers were imaged with a fat-suppressed, three-dimensional, spoiled gradient-recalled sequence. The field of view, number of phase-encoding steps, and phase-encoding direction were varied. On each image, the thickness of the patellar and trochlear cartilage was measured in millimeters and divided by the pixel dimension, which effectively expressed the thickness as the number of pixels. Finally, the number of pixels was compared with the number of alternating hyperintense and hypointense lines depicted., Results: The number of truncation lines increased as pixel dimension was reduced by either decreasing the field of view or increasing the number of phase-encoding steps. The accuracy for predicting more than three lines with use of an anteroposterior phase-encoding direction varied between 83% and 92%. The appearance of the cartilage was altered when phase- and frequency-encoding directions were exchanged, but truncation lines were still evident., Conclusion: The trilaminar appearance depicted within hyaline cartilage on MR images obtained with this sequence is predominantly attributable to truncation artifact rather than to histologic zonal anatomy.

Purpose: To investigate the feasibility of imaging diaphragmatic motion with a fast gradient-recalled-echo (GRE) magnetic resonance (MR) pulse sequence., Materials and Methods: Fast GRE pulse sequences in sagittal and coronal planes were used to acquire repeated, single-level, 1.2-second scans in 10 healthy volunteers during deliberately slowed, approximate-vital-capacity breathing. Motion was analyzed subjectively by viewing the image sequences as cine loops and quantitatively by measuring the displacement of different points on the diaphragm at a workstation., Results: Temporal and spatial resolutions were adequate in all subjects. Absolute excursion of the domes was 4.4 cm on the right and 4.2 cm on the left. Analysis of diaphragmatic displacement at different locations revealed a gradient of excursion that increased from anterior to middle to posterior (P < .05-.001; paired t test). Excursion of the lateral aspects was greater than that of the medial aspect (P < .001)., Conclusion: Fast GRE MR imaging can be reliably used to demonstrate diaphragmatic motion and may prove useful in the investigation of normal and abnormal respiratory mechanics.

Pulsed magnetization transfer and continuous wave irradiation techniques are analyzed and compared for saturation efficiency and radio-frequency (RF) power requirements at 1.5 and 0.5 T. Binomial RF pulses transmitted on resonance are a more power-efficient method of exciting saturation transfer and are easily implemented with any pulse sequence. Binomial pulses selectively excite all short T2 species and behave as 0 degrees pulses for on-resonance, long T2 species.