[en] Most fast imaging sequences use gradient echoes and make images with T2 artifacts. If spin-echo sequences are used, the corresponding Ernst angle is close to 180⁰, and it is difficult to achieve a clean section profile. The authors' sequence uses a nonselective 180⁰ pulse immediately before section selection, giving fast images whose signal strength and contrast are similar to those of gradient recalled acquisition of a steady state (GRASS) but without T2 artifacts. The technique has been applied to the study of the passage of Gd-DTPA through the kidney. The images were free of T2 artifacts, including the black band seen previously

[en] This paper evaluates the choice of MR angiographic techniques during the first 2 months of life when cerebral blood flow rates are normally lower than in later infancy and childhood. Twenty-five infants (newborn to age 2 months) with cerebrovascular insults were evaluated by means of one or more MR angiographic techniques: (1) three-dimensional time of flight (3DTOF), (2) two-dimensional time of flight (2DTOF), and (3) velocity compensated-uncompensated time of flight (VCU-TOF). Studies done with and without gadolinium injection were also evaluated. 2DTOF showed better visualization of slower distal arterial flow in cortical cerebral branches than did 3DTOF or VCU-TOF. The major limitation of 2DTOF was a relatively thick (2 mm) section. 3DTOF with gadolinium enhancement also showed good cerebral cortical vasculature but required needle placement and was problematic when contrast-enhancing damaged tissue was present. VCU-TOF proved useful in subtracting out high signal intensity methemoglobin clot, such as in parenchymal hematomas or dural sinus and deep venous thrombosis

[en] This paper establishes protocols and evaluates the efficacy of dynamic enhanced MR imaging in the lungs using TurboFLASH. Fifty-one patients were imaged with 1.0-T and 1.5-T Siemens imagers. TurboFLASH images were obtained at one image per second using a TE of 3 msec and TR of 6 msec, following a bolus injection of gadolinium. Total imaging time was less than 1 minute. Prominent contrast enhancement was seen in seven of seven patients with a variety of primary and metastatic lung tumors. Postoperative changes and granulomas were not enhanced with contrast material. Respiratory and cardiac motion created no significant degradation of images. Although the results are preliminary, and there is some nonspecificity associated with this procedure, the early data are nevertheless encouraging. The authors have been able to study the lungs and pulmonary vascularity without motion degradation. Initial findings suggest that it may be possible to distinguish neoplasms from both granulomas and postoperative changes

[en] Marked hypointensity on the second echo of long repetition time (TR) pulse sequences at 1.5 T has been noted in colloid cysts of the third ventricle and mucous retention cysts of the sinuses. Both are lesions containing a large quantity of material that stains positive for polysaccharide. In an attempt to explain these findings, polysaccharide materials (potato starch) were prepared at 1%, 3%, and 7% (liquid) and 10% (gel) concentrations in distilled deionized water, .01 and .1m mM FeCl3. Imaging at 1.5 T and measurements of T1 and T2 at 1.9 T were performed. Relaxation rates of 10% dextran solutions with average molecular weights of 17,000, 40,000, 70,000, 150,000 and 450,0000 were measured at 1.9 T. The addition of 1% - 10% starch to water shortened T1 and increased the brightness of images obtained at short TR/TE. The addition of FeCl3 increased T1 shortening and image brightness with T1 weighting. T2 was minimally affected by the soluble polysaccharide, but somewhat more decreased in the gelatinous material

[en] Sodium magnetic resonance imaging is being used to study pulmonary edema in rats. Alloxan is used to induce permeability edema, and a saline infusion to induce hydrostatic edema. Images are made before and after edema is induced and after an infusion of varying doses of dextran-magnetite (1-5 mL) of different particle sizes and coating (charged or uncharged). The dextran-magnetite reduces signal intensity in the heart, liver, and lungs by differing amounts. The amount that enters the extravascular space of the lung should be a function of the type of edema and dextranmagnetite parameters and may enable one to distinguish the type of edema

[en] Our purpose was to assess the effect of alterations in the cranial venous outflow on cerebrospinal fluid (CSF) flow waveforms using phase-contrast MRI. Thirteen healthy subjects were assessed for CSF flow and cerebral vascular flow at the C2-3 level, both before and after jugular venous compression (JVC). The flow waveforms were assessed both as an aggregate, and after dividing subjects in two groups based on percent jugular venous flow (PJVF) i. e. jugular outflow expressed as percent of cerebral arterial inflow. Group 1: 7 subjects with PJVF more than and including median (predominantly jugular outflow); Group 2: 6 subjects with PJVF less than median (predominantly extra-jugular outflow). CSF waveforms: JVC produced rounding of contours and flattening of dicrotic waves, with the effect being greater in group 1 than group 2. In group 1, systolic upslopes of the waveforms increased. No significant aggregate amplitude changes were noted; amplidutes increased in group 1 (P = 0.001), and decreased in group 2 (P = 0.03). Temporal interval to the maximum CSF systolic flow significantly increased in group 1. Vascular flow: Arterial flow significantly decreased in group 1. Jugular flow significantly decreased in both groups. The results suggest that CSF flow waveforms are sensitive to alterations in the cranial venous outflow. Changes in group 1 are most likely because of an elevation in intracranial pressure. Analysis of CSF flow waveforms appears a promising noninvasive tool for assessment of cranial compartment. (orig.)

[en] Localized proton nuclear magnetic resonance spectroscopy (MRS), obtained with stimulated echo and spin echo sequences, MR imaging (MRI) and MR angiography (MRA) were used to study the brain in 13 children and adolescents with sickle cell disease. Regions of interest (ROI) studied by MRS included regions appearing normal on MRI as well as regions showing complications of sickle cell disease, including focal deep white matter areas of high signal intensity (deep white matter ischemia, DWMI) seen on long TR images, focal atropic brain areas, and infarcts. The findings in these studies are summarized as follows: Normal-appearing regions on MRI have normal MRS. In ROI including small areas of DWMI, lactate elevation was not detected, but the levels of N-acetyl-aspartate (NAA) appeared slightly elevated. In areas of DWMI 1-2 cm in size, reduced blood flow could be seen on MRA and lactate elevation could be detected with MRS. When blood flow to a DWMI region was normal, NAA was reduced and there was little lactate elevation, as cell death had already occurred. ROI consisting of atrophic tissue had reduced NAA levels but total creatine levels were not changed. Sometimes lipids, presumably from broken cell membrane, could be detected. In regions of past massive stroke, all metabolites were absent except for small amounts of lactate or lipids. (orig.)

[en] Our purpose in this investigation was to explain the heterogeneity in the cerebrospinal fluid (CSF) flow pulsation amplitudes. To this end, we determined the contributions of the cerebral arterial and jugular venous flow pulsations to the amplitude of the CSF pulsation. We examined 21 healthy subjects by cine phase-contrast MRI at the C2-3 disc level to demonstrate the CSF and vascular flows as waveforms. Multiple regression analysis was performed to calculate the contributions of (a) the arterial and venous waveform amplitudes and (b) the delay between the maximum systolic slopes of the arterial and venous waveforms (AV delay), in order to predict the amplitude of the CSF waveform. The contribution of the arterial waveform amplitude was positive (r = 0.61; p 0.003) to the CSF waveform amplitude and that of the venous waveform amplitude was negative (r = -0.50; p = 0.006). Both in combination accounted for 56 % of the variance in predicting the CSF waveform amplitude (p < 0.0006). The contribution of AV delay was not significant. The results show that the variance in the CSF flow pulsation amplitudes can be explained by concurrent evaluation of the CSF and vascular flows. Improvement in the techniques, and controlled experiments, may allow use of CSF flow pulsation amplitudes for clinical applications in the non-invasive assessment of intracranial dynamics by MRI. (orig.). With 3 figs., 2 tabs