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Purpose: Late juvenile neuronal ceroid lipofuscinosis (NCL) is a lysosomal neurodegenerative disorder caused by the accumulation of lipopigment in neurons. Our purpose was to characterize the MR imaging and spectroscopic findings in three children with late infantile NCL., Methods: Three children with late infantile NCL and three age-matched control subjects were examined by MR imaging and by localized MR spectroscopy using echo times of 135 and 5. Normalized peak integral values were calculated for N-acetylaspartate (NAA), choline, creatine, myo-inositol, and glutamate/glutamine., Results: MR imaging revealed volume loss of the CNS, most prominently in the cerebellum. The T2-weighted images showed a hypointense thalamus and hyperintense periventricular white matter. Proton MR spectra revealed progressive changes, with a reduction of NAA and an increase of myo-inositol and glutamate/glutamine. In long-standing late infantile NCL, myo-inositol became the most prominent resonance. Lactate was not detectable., Conclusion: MR imaging in combination with proton MR spectroscopy can facilitate the diagnosis of late infantile NCL and help to differentiate NCL from other neurometabolic disorders, such as mitochondrial or peroxisomal encephalopathies.

In localized proton magnetic resonance spectroscopy very short echo times (TE) are achieved to diminish signal loss due to T2 relaxation and to avoid phase distortions due to J-coupling. A sequence for single volume spectroscopy in human brain is described with a TE as low as 5 ms. Examinations were performed on a 1.5 T whole-body imager with actively shielded gradients. A self-designed stimulated echo acquisition mode (STEAM) sequence with very high amplitude spoiling gradients of 24 mT/m was used to take advantage of the whole potential of the gradient system. Optimization of TE was carried out by controlling spectral quality and localization in both phantom and volunteer measurements. Proton spectra of human brain were acquired in 21 healthy volunteers. Spectra of occipital white matter, parieto-occipital grey/white matter, and cerebellum revealed none or only small eddy current distortions at a TE of 5 ms. The volume of interest was 8-12 ml, repetition time was 1.5 s, and mixing time was 5 ms. Peak ratios of major metabolites referring to creatine were estimated and the relative standard deviations were calculated to determine interindividual reproducibility. The relative standard deviation of myo-inositol ranged from 6% to 11% within these brain regions whereas for glutamine and glutamate 7% to 16% were found.

The potential of functional magnetic resonance imaging (fMRI) for experimental studies of the brain and behavior considerable given its superior time and spatial resolution, but few studies have attempted to validate them against established methods for measuring cerebral activation. In a previous study absolute regional cerebral blood flow was measured in 16 healthy individuals using quantitative H215O-PET during standardized happy and sad mood induction and during two non-emotional control conditions. During sad mood, blood flow increased in the left amygdala and these changes correlated with shifts towards a negative affect. In the present study blood oxygenation level dependent (BOLD) changes were measured with fMRI during the same experimentally controlled mood states and control tasks. Twelve right-handed normal subjects were examined with a T2*-weighted FLASH sequence. A significant increase in signal intensity was found during sad as well as happy mood induction in the left amygdala. This converging evidence supports the potential of fMRI for advancing the understanding of neural substrates for emotional experience in humans.

We report a man with a ruptured intracranial dermoid cyst, suffering from headache, nausea, vomiting and a generalised seizure. MRI was performed before and 2 weeks after surgical resection. On T1-weighted images the tumour gave high signal, as did fatty material in the frontal and parietal brain sulci. Identification of this hyper-intense material as lipids was possible by chemical-shift-selective 3D gradient-echo imaging, which provided excellent contrast between the subarachnoid lipids and the adjacent normal brain, with a good spatial resolution. Possible complications of subarachnoid and intraventricular lipid particles after dermoid cyst rupture are discussed and the diagnostic value of 3 D chemical-shift-selective additional to conventional T-1-weighted spin-echo images in identification of even small amounts of fat is emphasised.

This study addressed the use of 3D MR angiography with flip angles (FAs) linearly varying across the excitation volume in order to diminish spin saturation. The shape of the ramp profile was varied to optimize the method for different regions and pathological alterations. Radio frequency pulses with ramp-shaped excitation profiles were generated using Fourier transformation and integrated into a flow-compensated 3D-FISP sequence. With the use of ramp-shaped excitation profiles good results were obtained for intracranial arteries as well as for neck arteries (i.e. carotid and vertebral arteries) which were demonstrated in 6 healthy volunteers and in 5 patients with various stenoses and anomalies of the carotid and vertebral arteries. With this technique it was possible to use increased thicknesses of the excitation volume (slab) up to 256 mm. Ramp-shaped excitation pulses with linearly increasing FAs in main flow direction can provide improved contrast of the vessel parts located distally to the entry side of the slab. Although this method has no advantage concerning complex flow or other dephasing effects; its particular effectiveness lies in the reduction of spin saturation.

Quantification of citrate by localized 1H spectroscopy is usually performed using the water signal as reference, but the signal behavior of the J-coupled AB spin system of citrate after multipulse excitation is not as trivial as for uncoupled substances. The influence of the timing scheme of double spin-echo sequences and of the spatial flip angle distribution of (nonideal) refocusing pulses was analyzed systematically for the citrate resonances. Both single echo times of the double spin-echo sequence were varied between 20 ms and 250 ms in theoretical and experimental approaches. Relatively long total echo times (TE > 120 ms) provide high selectivity to citrate signals, since signals from triglycerides at 2.6 ppm are markedly reduced. Asymmetrical timing schemes of the double spin-echo sequence with one short single echo time of 20 ms and one longer single echo time of about 120 ms result in high integral signal from the central lines of citrate, whereas symmetrical timing leads to high sensitivity for total echo times TE near 100 ms. The integral citrate signals in spectra with relatively long echo times (TE > 120 ms) were found to depend markedly on the type of the refocusing pulses, affecting quantitative citrate measurements in vitro and in vivo.

Changes in regional cerebral blood oxygenation during experimentally modified psychological activation can be measured with functional magnetic resonance imaging (fMRI). fMRI is a new imaging technique for perfusion-based signal intensities of the brain without the necessity of radioactivity and with superior anatomical and temporal resolution compared to positron emission tomography (PET). In this study a T2* FLASH sequence (TR 240ms, TE 60ms, slice thickness 4 mm, alpha = 40 degrees, matrix 64 x 128) was used to investigate changes in signal intensity within the temporal lobe and the amygdala during experimentally induced emotions. Visual stimuli of happy [sad] facial portraits were presented to volunteers to induce changes in the subjects' mood while lying in the tomograph. In agreement with a previous PET study, a significant increase in signal intensity in the left amygdala was found during induction of a sad mood, while no comparable effect was visible during induction of a happy mood.

The quantitative assessment of lactic acid in tissue is an important goal for in vivo volume-selective NMR spectroscopy to aid in the noninvasive diagnosis of oxygen deficiency of other metabolic disorders. PRESS localized 1H spectra provide comparatively high signal-to-noise ratio from small volume elements in a single acquisition mode. The quantification of lactate after multipulse excitation is not trivial due to the J-coupling characteristics which do not occur for the substances serving as references. The influence of the timing scheme and of the quality of the refocusing pulses was systematically evaluated for the lactate resonances by volume-selective measurements. Gaussian pulses, Hanning-filtered sinc pulses, and numerically optimized RE-BURP-pulses were applied for refocusing the magnetization in the PRESS sequence and the effects on the lactate AX3 spin system were compared. For these pulses, sequence parameters are presented providing high sensitivity to lactate signals. Timing schemes are shown which provide good quantification of lactate, even in cases with B1-inhomogeneities or slight misadjustment of the transmitter amplitude. The combination of both echo times in the double-echo sequences clearly influences the signal characteristics of lactate at overall echo times near TE = 145 and 290 ms, which may result in pure in-phase magnetization for this weakly coupled homonuclear system. Numerically optimized refocusing pulses (RE-BURP) provided up to 50% higher signal ratio of the methyl protons of lactate to uncoupled nuclei than the often used Hanning-filtered sinc pulses.

Spin saturation effects in 3D time-of-flight (TOF) MR angiography (MRA) can be reduced by using radio-frequency (RF) pulses with linearly increasing flip angles (ramp pulses) in the main direction of flow. MR angiograms of the cervical arteries of five healthy volunteers and eleven patients suffering from stenosis of the internal carotid arteries were acquired using a standard flow-compensated 3D FISP sequence with a single volume technique. Compared with the conventional MR angiograms acquired with constant flip angles, the MR angiograms could be considerably improved using the ramp pulses. Especially the distal parts of the vessels were depicted more clearly due to significantly reduced saturation effects. Since the vessel signal largely depends on the shape of the ramp pulses, we developed a model for calculating the signal distribution of the flowing protons for different ramp shapes and a given excitation volume (slab). The calculated signals were largely consistent with the signals in the MR angiograms, thus permitting numerical optimization of the shape of the ramp pulses for the cervical arteries. This optimized shape of the ramp pulse provided a high homogeneous vessel signal across the slab.

We examined 32 patients with intracranial tumors (17 meningiomas, 8 neuromas, 7 pituitary adenomas) by conventional and dynamic contrast-enhanced MRI. Our aim was to clarify whether the pathological dural contrast enhancement adjacent to meningiomas (the "dural tail") is specific to meningiomas and, more important, whether it represents neoplastic dural infiltration or hypervascularization as a tumor accompanying reaction. A "dural tail" was found in 9 of 17 meningiomas. None of the other extra-axial tumours (neuromas, pituitary adenomas) showed comparable dural enhancement. Dynamic examinations with an ultrafast single slice imaging technique (snapshot-FLASH) after a bolus injection of contrast medium showed a "dural tail" in seven out of these nine meningiomas, while in two cases the "dural tail" turned out to be a cortical vein with a characteristic dynamic contrast enhancement pattern. In the dynamic study all seven "dural tails" were found to have earlier, steeper contrast enhancement than the corresponding tumours. All the tumours and part of the adjacent dura mater in four of the seven meningiomas with dural enhancement were examined histopathologically. In none of these four cases was neoplastic tissue found more than 2 mm away from the main tumour. The results strongly support the suggestion that the "dural tail" adjacent to meningiomas represents a hypervascular, non-neoplastic dural reaction.

As recently demonstrated, spin saturation effects in 3D time-of-flight (TOF) MR angiography (MRA) can be reduced by using RF pulses with linearly increasing flip angles (ramp pulses) in the main direction of flow. We developed a model for calculating the signal distribution of proton flow within the excitation volume (slab) for different ramp slopes and compared the results with the measured distribution for the lower-leg arteries. The ramp pulses were generated using the Fourier transformation of the desired excitation profiles. With a bandwidth of 6 kHz and a pulse length of 2.56 ms satisfactory ramps with variable slopes were generated and applied in a standard flow-compensated 3D FISP sequence. The effects on the signal distribution in the resulting angiograms of the lower limbs revealed a considerable reduction of saturation losses in agreement with the calculations. Calculated optimal ramp slopes are provided for flow velocities ranging from 5 to 50 cm/s and excitation volumes ranging from 5 to 25 cm.

A magnetic resonance method is described which provides good-quality field-mapping images of the spine, although the in vivo signals from red bone marrow of the vertebral bodies exhibit similar fractions of lipid and water protons with their chemical-shift difference of 3.4 ppm. The susceptibilities of bone marrow and intervertebral disks were examined in 20 cadaveric human spines, 9 healthy volunteers, and 9 patients with degenerative disk alterations. The influence of geometrical properties was studied in cylindrical spine phantoms of different size and contents with different susceptibility. The measurements reveal interindividual differences of the susceptibility of the intervertebral disks in healthy subjects. Three out of nine degenerated disks with low signal in T2-weighted spin-echo images showed irregularities of the field distribution within the nucleus pulposus.

The slice selection properties of three different soft refocusing-pulses (sinc-pulse, Hanning filtered sinc-pulse, and the numerically optimized reburp-pulse) within a standard double spin-echo sequence for localized proton spectroscopy were examined and compared. The slice profiles were measured acquiring two-dimensional images of the selected volumes of interest (VOI) appending a gradient-echo imaging part at the end of the spectroscopic part of the sequence. A comparison of the reached signal strength with the different pulses using the same voxel size (same Full Width Half Maximum, FWHM) was performed by in vitro and in vivo measurements. Additionally theoretical calculations using the Schrödinger equation for spin 1/2 particles in combination with a phase averaging method that takes into account the magnetic field spoiling and selection gradients of the spectroscopy sequence were performed. Calculated and measured slice profiles did well correspond. The numerically optimized reburp-pulse showed significant better slice selection and phase behaviour properties compared to the sinc-pulses. Further, a signal gain of about 20% was measured using the reburp-pulse, which was in good agreement with the calculated signal gain of 23%.

Purpose: To investigate whether exact evaluation of the dynamic contrast enhancement pattern within intracranial tumors can help to classify tumor histology and vascularity., Method: Forty-nine patients suffering from different intra- and extraaxial intracranial tumors underwent MR-examination in a 1.5-T superconductive whole body system. After rapid injection of Gd-DTPA, 48 images were acquired during the first 1.5 to 2 minutes of contrast enhancement within the tumors. A fast snapshot-FLASH imaging technique allowed measurement times of 1 second per image. Appearance of Gd-DTPA in a venous sinus served as a temporal reference point. Transformation of 48 discrete measurement points (mean signal values of the enhancing tumor region) into a continuous curve, using a cubic spline approximation, allowed calculation of the time of maximum signal increase (Tm1) and the following time of half maximum increase (Tm2). These time parameters were compared to histopathologic findings, especially the degree of tumor vascularization., Results: Significantly different dynamic patterns of the early enhancement period were found for the different tumors. All eight neurinomas, typically less vascularized than most meningiomas, showed a characteristically prolonged contrast enhancement with a long Tm2. Histopathologic findings concerning the degree of vascularization showed two subtypes in meningiomas (n = 17) as well as in pituitary macroadenomas (n = 7). This was confirmed by dynamic evaluation in all cases, in the sense that short Tm1 and Tm2 were found in cases with higher degrees of vascularization. Negatives values of Tm1 were measured in two glomus jugulare tumors, reflecting the arterialization of these vascular tumors. In neuroepithelial tumors (n = 15), the glioblastomas (n = 7) showed very short Tm1 compared to the lower grade gliomas (n = 8). This is explained by histologic findings of pathologic vessels with arteriovenous shunts., Conclusion: The evaluated dynamic time parameters can be used to narrow differential diagnostic possibilities and to infer the degree of vascularization of intracranial tumors.