摘要:

Abstract1H‐MR spectra of human skeletal muscle feature peak splittings due to dipolar coupling. Quantitative difference spectroscopy in a double‐blind cross‐over trial testing oral creatine supplementation revealed that most of the resonances affected by dipolar coupling can be assigned to creatine and/or phosphocreatine. The assignment was performed in two different skeletal muscles and confirmed by measurements at the magic angle where dipolar splittings vanish. Numerical spectral simulations revealed that the observed spectra are consistent with partly‐averaged dipolar coupling among methylene and methyl protons of (phospho)creatine. The possible nature of the molecular dynamics leading to incomplete dipolar averaging is di

ISSN:0740-3194    

DOI:10.1002/mrm.1910370202

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

年代:1997

数据来源: WILEY

摘要:

AbstractSimultaneous acquisition of1H‐decoupled31P and19F 3D CSI is demonstrated in the liver of a patient undergoing 5‐fluorouracil chemotherapy. Both31P and19F shared the same voxel size (64 or 27 ml), bi‐level1H‐decoupling and 0.35 sTR.The measurements were done in a 1.5 Tesla clinical imager with three radio‐frequency (RF) channels and a triple‐tuned surface‐coil. The overall MRI and MRS examination time was under 90 min. Simultaneous acquisition of31P and19F permits localized study of the influence of hepatic metabolism on the uptake and catabolism of fluoropyrimidine drugs without extra measurement time

ISSN:0740-3194    

DOI:10.1002/mrm.1910370203

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

年代:1997

数据来源: WILEY

摘要:

AbstractDiffusion‐weighted MRI at 2 T was used to monitor and assess tissue damage after permanent middle cerebral artery occlusion (MCAO) in wild‐type (WT) and mice deficient in nitric oxide synthase gene expression (nNOS−). The ischemic lesion was evaluated 3 h after occlusion and subdivided into the lesion core and peri‐infarct zone based on the magnitude of the apparent diffusion coefficient (ADC) change. Infarct volume, measured by using histochemical staining 24 h after MCA occlusion, correlated best with MRI infarct volume as assessed by an ADC threshold of 25% decrease from baseline at 3 h. For ADC thresholds of greater than 25% decrease, lesion size was not significantly different in nNOS−and WT mice. However, brain tissue showing ADC decreases of 10–25% was significantly smaller in the ipsilateral hemisphere of mutants (27 · 2% and 21 · 2% in WT and nNOS−, respectively;P<0.05). These findings occurred independently of infarct volume and are consistent with a smaller peri‐infarct zone in nNOS−mice. We postulate that the smaller peri‐infarct zone is a reflection of less severe metabolic disturbance after ischemia in nNOS−mice, possibly related to diminished production of nitric oxide (NO) or a related product. We conclude that magnetic resonance techniques previously used to assess ischemic damage in larger animals can be extended to the mouse, raising the possibility that the molecular mechanisms leading to ischemic damage can be examined by using gene

ISSN:0740-3194    

DOI:10.1002/mrm.1910370204

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

年代:1997

数据来源: WILEY

ISSN:0740-3194    

DOI:10.1002/mrm.1910370205

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

年代:1997

数据来源: WILEY

摘要:

AbstractIt is demonstrated that the stability of the Carr‐Purcell‐Mei‐boom‐Gill (CPMG) sequence reflects the existence of a steady state solution to the Bloch equations in the absence ofT2andT1decay. The steady state theory is then used to evaluate the performance of low flip angle RARE imaging sequences with both constant and optimally varied refocusing flip angles. The theory is experimentally verified in phantoms and then optimized, single shot, low flip angle RARE is used to obtain artifact‐free images from the brain of a normal

ISSN:0740-3194    

DOI:10.1002/mrm.1910370206

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

年代:1997

数据来源: WILEY

摘要:

AbstractThe requirements for imaging the skin are dictated by the organ's layered structure, which extends only a few millimeters from the surface and thus demands extremely high resolution in this direction. While less critical, resolution in the remaining two dimensions determines whether the skin's accessory structures can be resolved. The problem is compounded by short transverse relaxation times, in particular of the dermis, the structure of most clinical interest. In this work images of the normal human skin were obtainedin vivoat voxel sizes as small as 19 × 78 × 800 μm3, by means of customized 3D gradient and partial flip‐angle spin‐echo pulse sequences and very small transmit/receive coils on a 1.5T clinical imager equipped with high‐power whole‐body gradients. Structures resolved include hair follicles and the sublayers of the dermis. The very short time constant for the major component (91 %) for transverse relaxation in the dermis (T2* ∼10 ms) suggests the potential of substantial gains in achievable signal‐to‐noise ratio by shorteni

ISSN:0740-3194    

DOI:10.1002/mrm.1910370207

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

年代:1997

数据来源: WILEY

ISSN:0740-3194    

DOI:10.1002/mrm.1910370208

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

年代:1997

数据来源: WILEY

摘要:

AbstractMyotonic dystrophy is an inherited multi‐system disease. Its pathophysiology leading to muscle malfunction and damage is not well understood.23Na NMR spectroscopy was applied here for anin vivocomparative study of the calf muscles of 7 myotonic dystrophy patients at various stages of the disease and 11 healthy volunteers. Both the total sodium content, expressed as the ratio of the23Na and1H water signals, and the fast transverse relaxation time,T21, determined from the triple quantum‐filtered spectra, increased in correlation with the severity of the disease. The results demonstrate that23Na NMR enables the quantitation of myotonic dystrophy progress

ISSN:0740-3194    

DOI:10.1002/mrm.1910370209

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

年代:1997

数据来源: WILEY

摘要:

AbstractThe2H DQF NMR spectra of deuterated water molecules were measured for the first time inin vivorat brain. The observation of the DQF signal indicates that there is a water population that exhibits anisotropic motion. The characteristics of the DQF spectra premortem and postmortem are very similar (lineshape and relaxation times). In the 1st h there is a 10–15% decrease in the signal intensity of the DQF spectra followed by a gradual but a much slower decrease in the DQF signal intensity that reaches 65–70% of its initial value after only 12 h. When the brains were kept at 4°C, a 40% decrease in the DQ signal intensity was observed only after 7 days. Mechanical chopping of the brain tissues causes an immediate loss of more that 97% of the DQ signals. The slow, temperature‐sensitive decay of the signal, and its sensitivity to mechanical treatment point out that these signals originate from water molecules that interact with structural components in the brain. The characteristics of the DQF spectra depend on the amount of bulk water as exemplified by increased residual quadrupolar interaction and relaxation rates obtained when dehydrating the brain

ISSN:0740-3194    

DOI:10.1002/mrm.1910370210

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

年代:1997

数据来源: WILEY

ISSN:0740-3194    

DOI:10.1002/mrm.1910370211

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

年代:1997

数据来源: WILEY