ISSN:0740-3194    

DOI:10.1002/mrm.1910340302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractRelative cerebral blood flow changes can be measured by a novel simple blood flow measurement technique with endogenous water protons as a tracer based on flow‐sensitive alternating inversion recovery (FAIR). Two inversion recovery (IR) images are acquired by interleaving slice‐selective inversion and nonselective inversion. During the inversion delay time after slice‐selective inversion, fully magnetized blood spins move into the imaging slice and exchange with tissue water. The signal enhancement (FAIR image) measured by the signal difference between two images is directly related to blood flow. For functional MR imaging studies, two IR images are alternatively and repeatedly acquired during control and task periods. Relative signal changes in the FAIR images during the task periods represent the relative regional cerebral blood flow changes. The FAIR technique has been successfully applied to functional brain mapping studies in humans during finger opposition movements. The technique is capable of generating microvascular‐based function

ISSN:0740-3194    

DOI:10.1002/mrm.1910340303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractA chemical‐shift selective (CHESS)19F MR imaging technique was used to map selectively the antineoplastic drug 5‐fluorouracil (5‐FU) and its major catabolite α‐fluoro‐β‐alanine (FBAL) in tumor‐bearing rats. The pulse sequence employed a CHESS RF saturation pulse to suppress either the 5‐FU or the FBAL resonance before the other component in the two‐line19F MR spectra was measured. Selective 5‐FU and FBAL images with a spatial resolution of 10 x 10 x 15 mm3(1.5 ml) were obtained in 40 min from six ACI rats with implanted Morris hepatoma. Because the transmitter frequency could always be set to the Larmor frequency of the19F resonance employed for imaging, the images were free of chemical‐shift artifacts in readout and slice‐selection direction. Whereas FBAL appeared only in the liver, the kidneys, and the bladder, 5‐FU could also be detected in all major organs and in the muscular system. In the Morris hepatomas, a small 5‐FU uptake and no FBAL accumulation were measured. The CHESS19F MRI technique provides useful physiological and biochemical data on the biodistribution of the antineoplastic drug 5‐FU and on the different cata

ISSN:0740-3194    

DOI:10.1002/mrm.1910340304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractA new three‐dimensional imaging strategy based on magnetization prepared ultrafast gradient recalled echo technique that demonstrates pronounced T1contrast at high fields is introduced. High‐resolution three‐dimensional image sets of human brain showing high contrast between white and gray matter areas are presented. The ratio of contrast‐to‐noise was examined as a function of the relevant parameters in the imaging sequence; calculations based on high‐field T1values as well as the experimental data demonstrated that maximal contrast‐to‐noise ratio is attained under the same magnetization preparation conditions both for cortical and subcortical gray matter relative to white matter, leading to approximately equivalent appearance of all gray matter areas in the same image. In addition, the images displayed clear visualization of subtle anatomical structures such as the subthalamic nuclei (ventral tier nuclei, dorsomedial nucleus, and pulvinar) and mammillo

ISSN:0740-3194    

DOI:10.1002/mrm.1910340305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThiamine deficiency (TD) in rats produces lesions similar to those found in humans suffering from Wernicke's encephalopathy, an organic mental disorder associated with alcoholism. Male Sprague‐Dawley rats (n= 29) were deprived of thiamine via a regimen of thiamine‐deficient chow and daily intraperitoneal injections of the thiamine antagonist pyrithiamine hydrobromide. Spectra were obtained by using the STEAM sequence. No significant change occurred in the ratio of Cr/NAA, while the ratio of Cho/NAA declined significantly (60 ± 11%) on Day 14. Eleven rats received intraperitoneal injections of thiamine hydrochloride at the end of 12 days, and dose‐dependent recovery in Cho/NAA was ob

ISSN:0740-3194    

DOI:10.1002/mrm.1910340306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe goal of this work was to investigate magnetization transfer (MT) in cartilage by measuring water proton signalsMs/Mo, as an indicator of MT, in (i) single‐component systems of the tissue's constituent macromolecules and (ii) intact cartilage under control conditions and after two pathomimetic interventions.Ms/Mowas quantified with a 12‐μT saturation pulse applied 6 kHz off resonance. Both glycosaminoglycans (GAG) and collagen exhibited concentration dependent effects onMs/Mo, being approximately linear for GAG solutions (Ms/Mo= ‐0.0137[% GAG] + 1.02]and exponential for collagen suspensions (Ms/Mo= 0.80 x exp[‐(%collagen)/6.66] + 0.20); the direct saturation of water could not account for the measuredMs/Mo. Although the effect of collagen onMs/Mois much stronger than for a corresponding concentration of GAG,Ms/Mois not very sensitive to changes in collagen concentration in the physiological range. Tissue degradation with 25 mg/ml trypsin led to an increase inMs/Mofrom the baseline value of 0.2 (final/initial values = 1.15 ± 0.13,n= 11,P<0.001). In contrast, a 10‐day treatment of cartilage with 100 ng/ml of interleukin‐1β (1L‐1β) caused a 19% decrease inMs/Mo(final/initial values = 0.81 ± 0.08,n= 3,P= 0.085). The changes in hydration and macromolecular content for the two treatments were comparable, suggesting thatMs/Mois sensitive to macromolecular structure as well as concentration. In conclusion, whereas the baselineMs/Movalue in cartilage may be primarily due to the tissue collagen concentration, changes inMs/Momay be due to physiological or pathophysiological changes in GAG concentration and tissue structure, and the measuredMs/Momay differentiate between various pathomimetic degr

ISSN:0740-3194    

DOI:10.1002/mrm.1910340307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractA kinetic analysis of water signal intensity changes measured in human visual cortex by PRESS localized1H spectroscopy at 500 ms resolution with light‐emitting diode (LED) goggle stimulation was used to determine vascular transit times for transitions between rest and activation. Monoexponential curve fitting was used to determine bothR2*values for each free induction decay and the time constants forR2*changes with activation and deactivation. Measured transit time values were in general agreement with the literature, and were significantly shorter for “Off→On” than for “On→Off” transitions, consistent with known alterations in blood flow with activation and deactivation. The differences in transit times between “Off→On” and “On→Off” also varied with stimulus frequency in accordance with known physiology. This type of analysis may provide a useful means of analyzing functional activation data and for quantitatively comparing functional activation results from differing subj

ISSN:0740-3194    

DOI:10.1002/mrm.1910340308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe potential of two‐dimensional (2D)‐J NMR forin vivoproton MRS is examined. Single voxel measurements on the rat brain were performed at 4.7 T using point‐resolved spectrocopy localization with a voxel size of 64 μl and total measuring times of 10‐15 min. It is shown that a series of measurements with only 16 or fewer different echo times (TE) enables good signal localization in thef1axis corresponding to the coupling patterns. For data evaluation, the 2D‐J NMR spectrum as well as cross‐sections at givenf1values and projections onto thef2axis are used. A comparison between cross‐section spectra taken at differentf1values may help to solve problems of peak assignment. The projection of the 2D magnitude spectrum onto thef2axis corresponds to a homonuclear decoupled 1D proton spectrum. Because theT2relaxation times of several coupled resonances (e.g., myo‐inositol and glutamate) are rather long, only minor losses in the quality of the projection spectra occur if the measurements with shortTE(≤ 50 ms) are not used for data processing. Thus, homonuclear decoupled proton spectra detecting uncoupled and several coupled resonances can be measured with high qualityin vivo, even on MR systems that are not equipped with actively shielded gradients, prohibiting data acquisition withTE

ISSN:0740-3194    

DOI:10.1002/mrm.1910340309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe anticancer agent temozolomide labeled with13C (8‐Carbamoyl‐3‐13C‐methylimidazo‐[5,1‐d]‐1,2,3,5‐tetrazin‐4‐(3H)‐one), was noninvasively detected in subcutaneous RIF‐1 tumors by a selective cross polarization13C NMR method, at a field strength of 9.4T. Pharmacokinetics of the drug, at a dose of 150 mg/kg, were determined for intravenous and intraperitoneal modes of administration (three animals per mode). The half‐life of the drug in the tumors was approximately 60 min. The uptake and clearance of the drug, however, varied significantly between individual hosts, for both modes of administration. These results demonstrate the feasibility of obtaining pharmacokinetics of anticancer agents for individual tumors without the need for a label that might modify drug activity (e.g., fluorine). The variability of thein vivomeasurements, even within the same tumor model, demonstrates the necessity of directly monitoring the tumor to evalu

ISSN:0740-3194    

DOI:10.1002/mrm.1910340310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractRapid changes in the average water diffusion constant,Dav= 1/3{Dxx+Dyy+ Dzz}, and in the concentrations of lactate and purine nucleotides and nucleosides were measured upon global ischemia (cardiac arrest) in cat brain, at a combined time resolution of 36 s (n= 7). At this time resolution, the normalized time curves of 1 ‐Davand the increases in ATP breakdown products did not coincide, with the changes inDavbeing most rapid. The normalized curves of 1 ‐Davand the lactate increase coincided for the first 2‐2.5 min after which the change inDavwas more rapid. After this time point, an excellent correlation was found between the drop inDavand the decrease in energy utilization rate, which was calculated from the measured time curves of lactate formation and ATP breakdown, and from the time curve for phosphocreatine use reported in the literature. These results are in agreement with the expected biphasic changes in ion and water homeostasis during ischemia and with the model of diffusional changes being a consequence of a water shift from interstitial to intra‐cellula

ISSN:0740-3194    

DOI:10.1002/mrm.1910340311

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY