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PubMed1996

[Cognitive function and MRI findings in very low birth weight infants].

Twenty-two very low birth weight infants at preschool ages of 5-6 years were studied to clarify the correlation between cognitive function and MRI findings. Cognitive function was evaluated by the Wechsler Intelligence Scale for Children-Revised (WISC-R) and the Frostig developmental test of visual perception. Ventricular enlargement, assessed by the bioccipital index (B. I.) measured on MRI, was correlated to cognitive disorders. Children with periventricular high intensity areas (T2-weighted images) extending from the posterior periventricular region to the parietal lobe tend to highly suffer from cerebral palsy and visuo-perceptual impairment. These results indicate that the disorders of cognitive function in very low birth weight infants were caused by a damage of association fibers in periventricular areas which was detectable by MRI.

Brain↗

PubMed2003

k-Space based summary motion detection for functional magnetic resonance imaging.

Functional MRI studies are very sensitive to motion; head movements of as little as 1-mm translations or 1 degrees rotations may cause spurious signals. An algorithm was developed that uses k-space MRI data to monitor subject motion during functional MRI time series. A k-space weighted average of squared difference between the initial scan and subsequent scans is calculated, which summarizes subject motion in a single quality parameter; however, the quality parameter cannot be used for motion correction. The evolution of this quality parameter throughout a time series indicates whether head motion is within a predetermined limit. Fifty functional MRI studies were used to calibrate the sensitivity of the algorithm, using the six rigid-body registration parameters (three translations and three rotations) from the statistical parametric mapping (SPM99) package as a reference. The average correlation coefficient between the new quality parameter and the reference value from SPM was 0.84. The simple algorithm correctly classified acceptable or excessive motion with 90% accuracy, with the remaining 10% being borderline cases. This method makes it possible to evaluate brain motion within seconds after a scan and to decide whether a study needs to be repeated.

Algorithms↗

PubMed2001

FMRI mapping of the somatosensory cortex with vibratory stimuli. Is there a dependency on stimulus frequency?

Vibratory stimuli on the skin are mediated by two major receptors: Meissner corpuscles and Pacinian corpuscles. These receptors differ in properties such as density distribution, receptive field size, frequency sensitivity and depth of location. The cortical response to stimulation of these corpuscles can be tested by taking advantage of the differences in frequency discrimination of the receptors. Meissner corpuscles are most sensitive to frequencies around 10-50 Hz (flutter), while Pacinian corpuscles are most sensitive to high frequency (100-300 Hz) vibration. This study compared the neuronal responses (hemodynamic response) generated from vibratory stimuli of 35 Hz and 150 Hz with functional MRI. Group functional activation maps showed differences in the activation pattern for the two stimulus frequencies.

Adult↗

PubMed2004

A review of structural magnetic resonance neuroimaging.

Magnetic resonance imaging (MRI) is often divided into structural MRI and functional MRI (fMRI). The former is a widely used imaging technique in research as well as in clinical practice. This review describes the more important developments in structural MRI in recent years, including high resolution imaging, T2 relaxation measurement, T2*-weighted imaging, T1 relaxation measurement, magnetisation transfer imaging, and diffusion imaging. The principles underlying these techniques, as well as their use in research and in clinical practice, will be discussed.

Brain↗

PubMed2004

Neurobiological findings in bipolar II disorder compared with findings in bipolar I disorder.

OBJECTIVE: To determine whether there are consistent neurobiological differences between patients with bipolar I disorder (BD I) and those with bipolar II disorder (BD II). METHOD: We reviewed the literature in areas where the most consistent neurobiological findings have been reported for bipolar disorder, specifically, neuroimaging and brain metabolism. The imaging studies reviewed examined structure, using magnetic resonance imaging (MRI), and function, using functional MRI, positron emission tomography, and single photon emission computed tomography. We used magnetic resonance spectroscopy to examine brain chemistry. We reviewed those metabolic studies that examined cell calcium, 3-methoxy-4-hydroxyphenylglycol, and protein kinase C. RESULTS: Some genetic studies suggest that there may be differences between BD II and BD I patients. However, our review of the imaging and metabolic studies identified few studies directly comparing these 2 groups. In those studies, there were few differences, if any, and these were not consistent. CONCLUSIONS: While genetic data suggest there may be differences between BD II patients and BD I patients, the neurobiological findings to date do not provide support. However, this may be owing to the small number of studies directly comparing the 2 groups and also to the fact that those carried out have not been adequately powered to detect possible small true differences. This is an important issue because, if there are no neurobiological differences, it would be anticipated that similar treatments would be similarly effective in both groups. Given the importance of understanding whether there are neurochemical differences between these groups, further research in this area is clearly needed.

Bipolar Disorder↗

PubMed2002

Clinical applications of proton MR spectroscopy in oncology.

Proton magnetic resonance spectroscopy (H1-MRS) has been increasingly receiving more attention from radiologists, neurosurgeons, radiation and medical oncologists in the "in situ" clinical evaluation of human tumors. The utilization of H1-MRS, especially in human brain tumors, coupled to both routine magnetic resonance imaging (MRI) and functional MRI techniques provides greater information concerning tumor grading and extension and characterization of the normal surrounding tissue than what is possible with any other imaging technique alone. In this paper, we will review the current status of proton MR spectroscopy with emphasis on its clinical utility to diagnose tumors, its utility in planning surgical and radiation therapy interventions, and in its use in monitoring tumor treatment.

Brain Neoplasms↗

PubMed1998

Proton magnetic resonance spectroscopy: an emerging technology in pediatric neurology research.

Proton magnetic resonance spectroscopy (MRS) is an emerging technology that allows for the quantitative noninvasive assessment of regional brain biochemistry. The capacity to carry out MRS studies requires existing magnetic resonance imaging (MRI) technology platforms and the purchase of commercially available software modifications. In this review, the physical basis for MRS will be presented leading to an understanding of its potential applications and limitations within the clinical research milieu. Thus far, within pediatric neurology, proton MRS studies have been used to assist in the prediction of outcome in a variety of settings of acquired brain injuries (perinatal asphyxia, near drowning). In addition, proton MRS has been used to document disturbances in oxidative metabolism in neurometabolic disorders, assisting in defining phenotype and the response to therapeutic interventions. In epilepsy, spectroscopic studies have been useful in localizing the epileptogenic zone in intractable focal epilepsies. Future applications of proton MRS will also be highlighted. These include its use as a means of observing the transport and metabolism of various compounds in the brain, its concurrent application with other nuclear magnetic resonance techniques such as MRI and functional MRI, and finally its potential as a means of assessing the short-term effects of any CNS targeted pharmacologic interventions.

Brain↗

PubMed2001

[Diagnostic criteria of multiple sclerosis in neuroimaging].

To date, there is no biological test available with enough confidence to make alone a diagnosis of Multiple Sclerosis (MS). MS diagnosis criteria are then an association of clinical and para clinical criteria that allow an objective demonstration of dissemination of lesions in both time and space. Adapted MRI criteria from Barkhof have a good sensitivity and the best specificity to evaluate MS. 3 of 4 criteria are necessary: 1 gadolinium enhancing lesion or 9 T2 hyper intense lesions; at least 1 infratentorial lesion; at least 1 juxtacortical lesion; at least four periventricular lesions; NB: 1 spinal cord lesion can substitute for 1 brain lesion. News methods as spectroscopy, magnetization transfer, diffusion MRI and functional MRI complete results of conventional MRI and give new informations about physiopathology of MS demyelinating lesions.

Brain↗

PubMed2003

MR imaging of epilepsy: state of the art at 1.5 T and potential of 3 T.

Shortly after being introduced in the nineteen eighties, magnetic resonance imaging (MRI) became a key tool for the investigation of patients with epilepsy, due to its ability to acquire high quality images. The strength of the magnetic field of a scanner is measured in tesla (T). This review addresses the clinical and research potential in epilepsy of MR imaging at 1.5 T and 3 T. A typical clinical scanning protocol at 1.5 T for a patient with refractory epilepsy may include T1- and T2-weighted imaging, fluid-attenuated inversion recovery (FLAIR) imaging, and a 3D volume acquisition sequence. A research protocol may add quantification of structural imaging, such as volumetric assessment and T2-relaxometry, together with functional measures, such as MR-spectroscopy, functional MRI and diffusion weighted sequences. MR-spectroscopy assesses the metabolites of the seizure focus and other brain areas. Functional MRI allows localisation of cognitive and sensori-motor function and the ability to assess the spatial relationship of these functions to the seizure focus. Whereas these techniques can be performed at 1.5 T, particularly MR-spectroscopy and functional MRI benefit from increased magnetic field-strength. Higher magnetic field-strength is associated with a higher signal-to-noise ratio (SNR). The increased SNR can allow shorter imaging times for a given resolution, higher resolution for a given imaging time, or combination of both. The use of higher magnetic field-strengths is therefore indicated for the (fast) imaging of ill subjects, for long protocols, including structural, metabolic and functional imaging, and for novel applications, such as continuous EEG recording and functional MRI for the detection of the seizure focus. Disadvantages of MR imaging in epilepsy at a high field-strength of 3 T and above are, apart from engineering and technical challenges, the greater energy deposition into tissue and increased susceptibility to artefacts. So far, magnets of 3 T and above have been used mainly for research applications, however the benefits of high field-strength for MR spectroscopy and functional MRI, and the usefulness of these techniques for the investigation of epilepsy patients are obvious incentives for the use of 3 T systems in routine clinical investigations.

Electroencephalography↗

PubMed2006

Principles of magnetic resonance assessment of brain function.

MRI has advanced to being one of the major tools for the assessment of brain function. This review article examines the basic principles that underpin these measurements. The main emphasis is on the characteristics and detection of blood oxygen level dependent (BOLD) contrast. In the first part of the article the relationship between BOLD, blood flow, blood oxygen, and the rate of metabolic consumption of oxygen is described. The four contrast mechanisms that contribute to the BOLD signal change, namely extravascular static and dynamic dephasing, intravascular T2-like changes, and the intravascular frequency offset effect are described in terms of their spatial localization and relative contributions to the BOLD signal. The current model of changes in blood flow being an indirect consequence of synaptic input to a region is presented. The second section of the article deals with the imaging characteristics of BOLD in terms of the attainable spatial resolution and linear system characteristics. In the third section, practical BOLD imaging is examined for choice of pulse sequence, resolution, echo time (TE), repetition time (TR), and flip angle. The final section touches on other MRI approaches that are relevant to cognitive neuroimaging, in particular the measurement of blood flow, blood volume, resting state fluctuations in the BOLD signal, and measures of connectivity using diffusion tensor imaging and fiber-tracking.

Algorithms↗

PubMed2004

Accentuation of high susceptibility of hypertrophied myocardium to ischemia: complementary assessment of Gadophrin-enhancement and left ventricular function with MRI.

The aim of the study was to compare infarction size and left ventricular (LV) function in normal and hypertrophied hearts after brief ischemia using Gadophrin-enhancement and functional assessment by MRI. Rats (n = 20) were assigned to aortic banding to induce LV hypertrophy or control. Eight weeks later, rats were subjected to 25 min of regional myocardial ischemia followed by 3 hr of reperfusion. The necrosis-specific agent Gadophrin-3 was injected to delineate infarcted myocardium on MRI. Effects of aortic banding and ischemia on LV mass and function were determined. At postmortem, areas at risk and infarction were measured. Close correlation was found between LV mass measured with MRI and at postmortem (r = 0.98). LV mass measured with MRI was significantly greater (0.81 +/- 0.02 g) in animals with aortic banding compared to control (0.62 +/- 0.02 g; P < 0.001). Infarction size was larger in hypertrophied hearts (19.0 +/- 1.4% / 18.3 +/- 1.5%) than in control (9.8 +/- 1.7% / 9.2 +/- 2.0%) on Gadophrin-enhanced MRI and at postmortem, respectively. Similarly, greater impairment in ejection fraction was observed in hypertrophied hearts with MRI (39 +/- 4% vs. 49 +/- 2%; P = 0.02). Gadophrin-3 provides accurate estimation of infarct size in hypertrophied hearts. Hypertrophied hearts are more sensitive to ischemia than nonhypertrophied hearts. The complementary assessment of Gadophrin-enhancement and LV function with MRI provides unique information about myocardium sensitivity to ischemia.

Animals↗

PubMed1996

Magnetic resonance imaging of human brain function.

BACKGROUND: Previously the exclusive domain of the technology of positron emission tomography, functional MRI is now proving capable of mapping functional regions of the human cortex in near real time during specific task activations or in response to any hemodynamic stress. Of particular interest is the opportunity to observe secondary cortical responses, activation due to imagined tasks, memory function, time-resolved pathways through cortical regions, and activation in sub-cortical structures. METHODS AND RESULTS: One method of functional MRI uses blood oxygenation changes, which can be imaged continuously while functional centers are being stimulated. Image intensity can become darker if there is more deoxygenated blood and brighter if more oxygenated blood enters the brain. This concepts works in all perfused tissues in the body, and allows use of the blood oxygenation mechanism to image neuronal activation. A second method takes advantage of the fact that the protons within the MRI slice are always partially saturated by the rapid rate of imaging. As blood flow delivers unsaturated blood water protons into an imaged slice, these arterially-delivered protons will appear very bright in the image. Visualization of this effect is accomplished by simple image subtraction or by comparison of intensity changes as a function of the paradigm application frequency. Using either approach leads directly to a functional map. CONCLUSIONS: At present, clinical applications are rapidly moving toward routine non-invasive mapping of distortions of the functional motor and somatosensory cortex and other cortical regions as a result of brain tumors. Other clinical applications include the observation of the effect of degenerative diseases such as multiple sclerosis. Alzheimer's disease, stroke, migraine, epilepsy, and other diseases causing neuronal loss and Parkinsonism. Functional MRI and its applications will continue to grow exponentially throughout the decade.

Brain↗

PubMed1988

[The MRI sites functioning in 1987 in France. Results of a survey].

A study of the 23 MRI sites functioning in France at the end of 1987 provides an overall view of the organizational and economic aspects of these sites as well as an initial assessment of their activity in terms of the types of equipment used and the institutions, private or public, within which they have been set up.

Costs and Cost Analysis↗

PubMed2026

Phase-resolved functional lung MRI detects single-dose and sustained bronchodilator responses in COPD in a randomized crossover trial.

OBJECTIVES: To evaluate the effects of tiotropium/olodaterol (T/O) on phase-resolved functional lung (PREFUL) MRI parameters in hyperinflated chronic obstructive pulmonary disease (COPD) patients and examine correlations with conventional cardiopulmonary and hyperpolarized 129Xe MRI measures. MATERIALS AND METHODS: Retrospective subanalysis of a prospective, randomized, placebo-controlled, crossover trial with open-label extension. Thirty-two patients with moderate-to-severe COPD (61.5 ± 7.7 years; 17 men); 30 completed the MRI extension at 1.5 T. PREFUL analysis yielded regional ventilation (RVent), flow-volume loop correlation metric (FVL-CM), normalized perfusion (QN), ventilation defect percentage (VDP), perfusion defect percentage (QDP), V/Q match metrics (VQM), and pulmonary pulse wave velocity (PWV; post-hoc parameter). Linear mixed-effects models tested treatment effects; correlations were evaluated with Spearman's rank and bootstrap 95% confidence intervals (95% CIs). RESULTS: PREFUL parameters improved after T/O single dose (SD) versus placebo, including improvements in FVL-CM by 4.1 percentage points (pp; 95% CI: 1.0 to 7.3 pp) and QN by 0.4 pp (95% CI: 0.2 to 0.6 pp) and reductions in VDP and QDP, with parallel gains in VQM(Non-Defect) (p < 0.05). PWV decreased after multiple doses (-0.87 m/s, 95% CI: -1.26 to -0.48 m/s). PREFUL MRI baseline values showed significant correlations with pulmonary function tests, cardiac, dynamic contrast-enhanced and 129Xe MRI. SD treatment-induced absolute changes in VDP(FVL-CM) correlated with reductions in residual volume (ρ = 0.41, 95% CI: 0.02 to 0.64). Further correlations were observed between PREFUL MRI and ¹²⁹Xe-derived VDP, apparent diffusion coefficient, and compartment ratios. CONCLUSION: PREFUL MRI sensitively captured immediate SD T/O-induced improvements in V/Q parameters and dose-dependent PWV responses after sustained bronchodilation. KEY POINTS: Question Can phase-resolved functional lung (PREFUL) MRI sensitively capture immediate single-dose and sustain multi-dose effects of tiotropium/olodaterol on ventilation-perfusion and vascular function in COPD patients? Findings Tiotropium/olodaterol improved PREFUL MRI-derived ventilation, perfusion, and V/Q matching parameters after a single dose, with sustained pulmonary vascular improvements after repeated dosing. Clinical relevance PREFUL MRI detected immediate and sustained functional improvements after tiotropium/olodaterol and showed significant correlations with cardiopulmonary tests and hyperpolarized ¹²⁹Xe MRI, supporting its role as a sensitive, radiation-free tool for monitoring COPD treatment response.

Humans↗

PubMed2001

[The right hemisphere language].

A large number of observations since the mid-nineteenth century have shown that damage to the left but not the right hemisphere destroys language function. These observations lead to the formation of the "classic" view that the left hemisphere has language function but not the right hemisphere. It thus came as a considerable surprise in the early 1960's when tests on commissurotomy or split-brain patients suggested the presence of a considerable capacity for reading comprehension in the right hemisphere. It has been suggested that the spared regions in the left hemisphere normally act to prevent the expression of latent language functions within the undamaged right hemisphere. Thus, only after the intact right hemisphere has been released from the disruptive and suppressive influences of the damaged left hemisphere by section of the corpus callosum, can its own residual function become effective. Some investigators have argued, however, that the split-brain evidence is misleading because the language of the split-brain patients is presented in both hemispheres even pre-operatively. Our investigation with functional MRI is in progress to decide which hypothesis is appropriate. In addition to the functional MRI study of split-brain patient, the functional MRI study of aphasia recovery will also provide opportunities to clarify the right hemisphere language function since the right hemisphere is generally intact in the right-handed aphasic.

Aphasia↗

PubMed2000

Congenital heart disease. Evaluation of anatomy and function by MRI.

With the increasing number of patients surviving after therapeutic intervention for congenital heart disease (CHD), accurate and frequent follow-up of their morphologic and functional cardiovascular status is required, preferably with a noninvasive imaging technique. Echocardiography, either transthoracic or transesophageal, has been the first choice for this purpose, and will probably keep that status, at least in a large segment of the CHD spectrum. Magnetic resonance imaging (MRI) is an established method for high-resolution visualization of cardiovascular morphology. In the past decade, newer MRI techniques have been developed that allow functional evaluation of CHD patients. Particularly the introduction of breath-hold imaging, contrast-enhanced MRA and user-friendly computer software for image analysis may move functional MRI of CHD from the science laboratory to clinical use. It is already evident that MRI is superior to echocardiography in certain areas of limited echocardiographic access, such as the pulmonary artery branches and the aortic arch in adult patients. But MRI has also a unique potential for accurate volumetric analysis of ventricular function and cardiovascular blood flow, without any geometric assumptions. If supported by increased cooperation between cardiologists and radiologists, MRI will grow into a useful noninvasive imaging tool that, together with echocardiography, will obviate the need for invasive catheter studies for diagnostic purposes.

Adult↗

PubMed1996

Ultrafast perfusion-weighted MRI of functional brain activation in rats during forepaw stimulation: comparison with T2 -weighted MRI.

A fast version of the arterial spin tagging technique for the detection of cerebral perfusion is presented. Based on adiabatic spin inversion in combination with snapshot FLASH imaging, our technique allows the recording of perfusion changes with a temporal resolution of about 3 s. Differences of cerebral perfusion dependent on the choice of anesthesia were observed in rat brain. Furthermore, with this arterial spin tagging method we demonstrated perfusion increases in the somatosensory cortex of anaesthetized rats during forepaw stimulation. Comparison of the activated areas in the T2 -weighted BOLD images and the perfusion-weighted images showed good spatial correspondence, but the sensitivity to the functional activation was more than ten times higher in the perfusion technique.

Anesthesia↗

PubMedDate not supplied

Improved target volume characterization in stereotactic treatment planning of brain lesions by using high-resolution BOLD MR-venography.

In this methodological paper I report the stereotactic correlation of different magnetic resonance imaging (MRI) techniques [MR angiography (MRA), MRI, blood bolus tagging (STAR), functional MRI, and high-resolution BOLD venography (HRBV)] in patients with cerebral arterio-venous malformations (AVM) and brain tumors. The patient's head was fixed in a stereotactic localization system which is usable in both MR-systems and linear accelerator installations. Using phantom measurements global geometric MR image distortions can be 'corrected' (reducing displacements to the size of a pixel) by calculations based on modeling the distortion as a fourth-order two-dimensional polynomial. Further object-induced local distortions can be corrected by additionally measured field maps. Using this method multimodality matching could be performed automatically as long as all images are acquired in the same examination and the patient is sufficiently immobilized to allow precise definition of the target volume. Information about the hemodynamics of the AVM was provided by a dynamic MRA with the STAR technique, leading to an improved definition of the size of the nidus, the origin of the feeding arteries, whereas HRBV imaging yielded detailed and improved information about the venous pattern and drainage. In addition, functional MRI was performed in patients with lesions close to the primary motor cortex area, leading to an improved definition of structures at risk for the high-dose application in radiosurgery. In patients with brain tumors the potential of HRBV to probe tumor angiogenesis and its use in intensity-modulated treatment planning is still hampered by the open question of how to translate a BOLD signal pattern measured in the tumor to a dose distribution, which should be addressed in future studies.

Brain Neoplasms↗