摘要:

AbstractQuantitative, single‐voxel proton NMR spectroscopy of normal brain was performed in five adult beagle dogs using the cerebral water signal as an internal intensity reference. The same brain regions were then rapidly isolated and frozen using a pneumatic biopsy drill, perchloric acid extracted, and analyzed by biochemical assay and high‐resolution NMR spectroscopy. The concentrations of the major resonances in thein vivoandin vitrospectra were compared, and good agreement was found between the different measurements. Thein vivospectra contained three peaks at 3.21, 3.04, and 2.02 ppm, which are usually assigned to trimethylamines (TMA), creatines, andN‐acetyl derivatives (NAc), which corresponded to be the following metabolite concentration values: 1.7 ± 0.6, 7.7 ± 2.1, and 10.9 ± 2.7 μmol/g wet weight respectively.In vitro, the following metabolite concentrations were measured: glycerophosphocholine (GPC) 1.3 ± 0.2, phosphocholine (PC) 0.5 ± 0.1, phosphocreatine (PCr) 2.6 ± 0.4, creatine (Cr) 5.9 ± 1.4, and N‐Acetyl aspartate (NAA) 8.9 ± 1.8 μmol/g wet weight. Therefore, the 3.21 ppm resonance observed in thein vivospectrum is predominantly GPC and PC in a ratio of 2.6:1, the 3.04 ppm resonance is Cr and PCr in a ratio of 2.3:1, and the 2.02 ppm resonance is predominantly (≈︁80%) NAA with small contributions fromN‐acetylaspartyl‐glutamate (NAAG) and glutamate. The data presented here validate the technique of water referencing as a simple and convenient means of quantitating single‐voxelin vivoprot

ISSN:0740-3194    

DOI:10.1002/mrm.1910320202

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

年代:1994

数据来源: WILEY

摘要:

Abstract31P NMR spectroscopy was used serially to study rejecting (ACI→LEW) and nonrejecting (ACl→ACl) orthotopic liver transplants in rats. Recipients were evaluated on post‐transplant days 1,3, 5, 7, 9, and 11. The relative changes in phosphomonoester (PME), inorganic phosphate (Pi), high‐energy phosphates and pH were studied. The earliest significant difference between the rejecting and nonrejecting groups was a decrease in the α‐NTP peak area on Day 5. This was followed by significant decreases in β‐NTP and pH, and increases in PME and Pion Day 7. High‐resolution31P NMR spectra of perchloric acid extracts demonstrated the PME increase to be due mainly to elevated phosphoethanolamine. Using the parameter (Pi+ PME)/(α + β + γ‐NTP), rejecting livers were distinguished from nonrejecting livers at a moderat

ISSN:0740-3194    

DOI:10.1002/mrm.1910320203

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe Cesium salt of BSSB (Cs4B24H22S2), a common boron‐neutron‐capture‐therapy (BNCT) agent, was injected into M2R mouse melanoma xenografts, and detectedin vivoby1H‐observed,10B‐edited NMR spectroscopy. The technique of spin‐echo difference spectroscopy, in which a proton spin‐echo is detected following the alternating presence and absence of a10B 180° pulse was used. This method provides much higher sensitivity than direct10B NMR detection, and should thus be suitable forin vivodetection in patients about to undergo BNCT treatment, where the infused agents are 95% isotopically

ISSN:0740-3194    

DOI:10.1002/mrm.1910320204

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

年代:1994

数据来源: WILEY

摘要:

AbstractDifferent approaches are being explored for the noninvasive observation of myocardial lipids in the human heart byin vivo1H NMR spectroscopy. One approach is to measure cardiac lipids using a combination of volume selection and 2D gradient phase encoding. From these data sets lipid images can be reconstructed. By comparing these lipid images with1H MR scout images, it is demonstrated that these signals represent epicardial and pericardial lipid. By selecting a smaller bar‐shaped volume combined with 1D phase encoding or by using single volume techniques, it is possible to avoid most of the pericardial and epicardial lipid to obtain myocardial1H NMR spectra of the human heart showing lipid signals, as well as trimethylamine and (phospho)creatine signals. These measurements demonstrate the feasibility of obtaining1H NMR spectra of the human myocardiu

ISSN:0740-3194    

DOI:10.1002/mrm.1910320205

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

年代:1994

数据来源: WILEY

摘要:

AbstractTo quantify metabolite and cation concentrations using NMR spectroscopy, the volumes of intracellular and extracellular spaces must be known. We describe a simple31P NMR spectroscopic method that employs dimethyl methylphosphonate (DMMP) as a marker of total water space and phenylphosphoriate (PPA) as a marker of extracellular space to determine intracellular and extracellular space volumes in the isolated, perfused rat heart.In vivoandin vitroradiolabel studies were used to verify this method. The difference between the total and extracellular water spaces, determined as milliliters/heart, gave the intracellular volume and allowed direct calculation of myocardial creatine phosphate, ATP, and inorganic phosphate concentrations, which were 13.4 mM, 10.1 mM, and 3.4 mM, respectively, for the glucose‐perfused rat heart. The extracellular volume decreased by 84% in hearts subjected to 28 min total, global ischemia and increased by 15% during reperfusion. The method described allows the determination of intracellular energy metabolite concentrations in perfused rat heart directly from a single, fully relaxed31P NMR spectru

ISSN:0740-3194    

DOI:10.1002/mrm.1910320206

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

年代:1994

数据来源: WILEY

摘要:

AbstractA method is demonstrated for the noninvasive detection and study of spreading cortical depression. Spreading depression (SD) was elicited in rats by topical application of potassium chloride to the exposed cortex. The apparent diffusion coefficient (Dapp) of water in a region of the cortex, measured using a PFG‐NMR spin echo sequence with an observation time of 40 ms, declines 35% within 30 s and recovers to the normal value within the next 30 s. The region of decreasedDappwas shown to be 2 mm in size and to move in the cortex, away from the point of application, with a uniform velocity of 3.3 ± 0.5 mm/min. The behavior of the affected region is consistent with other reports of the behavior of SD as monitored by electro‐physiological means. The technique can be implemented on currently available MRI equipment and makes possible the noninvasive study of SD in animal models of neurological disorders, their therapeutic intervention, and possibly the study of SD in hu

ISSN:0740-3194    

DOI:10.1002/mrm.1910320207

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

年代:1994

数据来源: WILEY

摘要:

AbstractTechniques are described to perform three dimensional (3D) MR microangiography. We have combined the use of a blood pool agent (Gd‐DTPA‐complexed with bovine serum albumin), three dimensional Fourier encoding, careful animal stabilization, and volume rendering to permit imaging with voxels of 60 × 60 × 60 pm. 3DFT encoding has been performed at 7.1 T with very large arrays (256 × 512 × 512). Interactive volume rendering allows a number of unique display opportunities that effectively exploit these isotropic 3D

ISSN:0740-3194    

DOI:10.1002/mrm.1910320208

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

年代:1994

数据来源: WILEY

摘要:

AbstractA tuned transmission line resonator has been developed in theory and in practical design for the clinical NMR volume coil application at 4.1 tesla. The distributed circuit transmission line resonator was designed for high frequency, large conductive volume applications where conventional lumped element coil designs perform less efficiently. The resonator design has made use of a resonant coaxial cavity, which could be variably tuned to the Larmor frequency of interest by tunable transmission line elements. Large head‐ and body‐sized volumes, high efficiencies, and broad tuning ranges have been shown to be characteristic of the transmission line resonator to frequencies of 500 MHz. The B1homogeneity of the resonator has been demonstrated to be a function of the electromagnetic properties of the load itself. By numerically solving Maxwell's: equations for the fully time‐dependent B1field, coil homogeneity was predicted with finite‐element models of anatomic structure, and inhomogeneities corrected for. A how‐to exposition of coil design and construction has been included. Simple methods of quadrature driving and double tuning the transmission line resonator have also been presented. Human head images obtained with a tuned transmission line resonator at 175 MHz have clearly demonstrated uncompromised high field advantages of signal‐to‐noise and spati

ISSN:0740-3194    

DOI:10.1002/mrm.1910320209

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe biexponential relaxation behavior of the sodium nucleus affects the accuracy of quantitative measurement ofin vivotissue sodium concentration (TSC). Theoretical analysis andin vivoexperimental results are used to demonstrate the extent of the large bias in the measured TSC that arises when the relaxation behaviorin vivodiffers significantly from that of the calibration standards which is when a significant fraction of the total sodium signal decays with a relaxation time much shorter than the echo time (TE) used for imaging. This bias can be as large as 20% for measurements of TSC in a normal rat brain withTE= 2 ms. Our findings indicate that shortening the echo time (TE<0.5 ms) by projection imaging is a reliable means of obtaining accuratein vivoestimates for TSC using MR.

ISSN:0740-3194    

DOI:10.1002/mrm.1910320210

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

年代:1994

数据来源: WILEY

摘要:

AbstractAn opposed solenoid intravascular receiver coil is used in a series of five pigs to generate images of the aorta. Severe ghosting artifacts are shown to occur if the motion of the intravascular coil is not restricted with respect to the vessel wall. Restricting coil motion and saturating the blood signal superior to the imaging plane are shown to produce high quality MR images. Layers within the artery wall could be discerned and the results of thein vivoanalysis compared favorably with high resolution MR images of the corresponding tissue after excision.

ISSN:0740-3194    

DOI:10.1002/mrm.1910320211

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

年代:1994

数据来源: WILEY