摘要:

AbstractPresently, the scores of three to four reviewers of each abstract are averaged and form a major component of the input for decisions made in choosing papers for oral and poster presentations, and in rejecting others. No normalization is made for differences in either mean or standard deviation between the reviewers of the same abstracts. In this paper, several techniques for normalizing the scores of reviewers are examined, and the consequences of applying such normalization is to several categories of the 1994 abstract submissions are examined. It was found that some alterations in the acceptance and assignments of papers as oral and posters resulted for one of the categories, and the normalized scores were used during the program assembly. It is recommended that future review procedures utilize reviewer normalization.

ISSN:0740-3194    

DOI:10.1002/mrm.1910320402

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

年代:1994

数据来源: WILEY

摘要:

AbstractA method combining several previously used approaches is described for the rapid, accurate quantitation of the fat content of biological tissue based on chemical shift images (CSI) corrected for magnetic field inhomogeneity, and compensated forT1, andT2, effects. The gravimetrically determined lipid content of fatty tissues (pork fat, rabbit and human liver) that had been differentially depleted of lipid by chloroform extraction correlated well (r = 0.99) with the lipid image intensities of the respective tissues. This multi‐point CSI method was used to quantitate lipid in fresh fatty human liver tissue (wet and dry) containing varying amounts of lipid. Plots of integrated lipid intensity versus tissue lipid content gave straight parallel lines for hydrated (r = 0.94) and dehydrated (r = 0.98) tissues, permitting determination of a proportionality constant for measuring absolute amounts of lipid present in a specific biological tissue. These results suggest the feasibility of using the methodin vivofor absolute quantitation of lipid in tissues of agricultural (e.g. pork, beef) and medical (e.g. human liver) interes

ISSN:0740-3194    

DOI:10.1002/mrm.1910320403

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

年代:1994

数据来源: WILEY

摘要:

AbstractAbsolute metabolite concentrations were determined in four different brain regions using phosphorus magnetic resonance spectroscopy (31P MRS) on 10 healthy adult volunteers. Localized spectra were collected simultaneously from the cerebellum and the cerebrum and, later, from deep white matter and cortical gray matter by means of a two‐volume lSlS pulse sequence and a Helmholtz‐type RF‐coil. Each brain spectrum was quantified with a calibration spectrum from a head‐shaped simulation phantom. A time‐domain fitting routine was used to process the fully relaxed data. Several metabolite concentrations (mmolAiter) differed significantly between the cerebrum and the cerebellum (PME = 3.2 f 0.3 and 4.0&0.6, PC:r = 2.9&0.3 and 3.9 f 0.4, NTP = 2.9 f 0.2 and 2.6&0.2, respectively) and between cortical gray matter and deep white matter (PME = 3.1 f 0.4 and 4.3 ± 0.8, PDE = 10.1 f 2.5 and 14.2&2.6, respectively). The concentration of free magnesium ion was found to be similar in all four brain regions (0.53 ± 0.21 mmol/liter) but the intracellular pH was significantly higher in the cerebellum (7.04 ± 0.03) than in the cerebrum (

ISSN:0740-3194    

DOI:10.1002/mrm.1910320404

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

年代:1994

数据来源: WILEY

摘要:

AbstractAbsolute metabolite concentrations were assessed in the muscle, the liver, and the kidney of healthy human volunteers by31P MRS. Fully relaxedin vivospectra were acquired with a surface coil and were localized with an adiabatic lSlS pulse sequence. The spectra were quantified with a subsequent measurement of a calibration phantom and were processed iteratively in the time domain. The following mean metabolite concentrations (mmollliter) were measured in the resting male calf muscle (n= 9), in the fasting liver (n= 12), and in the orthiotopic kidney (n= 5): [PME] = 2.0 ± 0.6, 3.8 ± 0.7, and 2.6 ± 0.9, [Pi]= 2.9 ± 0.3, 1.8 ± 0.3, and 1.6 ± 0.4, [PDE] = 3.8 ± 0.8, 9.7 ± 1.5, and 4.9 ± 1.1, [PCr]= 22.0 ± 1.2, 0, and 0, [NTP] = 5.7 ± 0.4, 2.9 ± 0.4, and 2.0 ± 0.3, respectively. Several interesting findings are to be emphasized: The concentrations of Pi, PCr, and NTP were 20% lower in the muscle of women than of men. In addition, the pH, was significantly lower in female muscle (6.99 ± 0.03) than in male muscle (7.05 ± 0.03). The pH, in the liver (7.12 ± 0.09) and in the kidney (7.09 ± 0.08) were higher than in the muscle of both genders. The free magnesium concentration (mmollliter) was higher in the lliver (1.40 ± 0.64) than in the kidney (0.79 ± 0.39) and in the mu

ISSN:0740-3194    

DOI:10.1002/mrm.1910320405

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

年代:1994

数据来源: WILEY

摘要:

AbstractMagnetization transfer experiments using an off‐resonance irradiation technique were performed on bovine serum albumin solutions by varying the irradiation frequency and the concentration. A transition of the magnetization transfer spectrunr from Lorentzian to Gaussian line shape was observed around the critical concentration of 6.2 mmoles of protein to kg ad solution. Observed magnetizations were well expressed by the rate equations of populations for spins below and above the transition, which yielded the magnetization transfer rates, the intrinsic relaxation rates of both protein and water protons, and the effective tumbling time and the rigid line width of the protein. The result showed that the estimates of the values for magnetization transfer rate do not change once the critical concentration is reache

ISSN:0740-3194    

DOI:10.1002/mrm.1910320406

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

年代:1994

数据来源: WILEY

摘要:

AbstractPulsed gradient spin echo (PGSE) sequences have been used to measure the signal loss of19F in perfluorinated hydrocarbon blood substitutes moving within the vasculature of the rat brain in the experimental conditions of the study. The signal loss is not characterized by a single apparent pseudodiffusion coefficient. A simple vascular network model based on self‐similarity hss been used to calculate the shape of the signal loss. Excellent agreement with the experiment has been obtained showing that the IVlM measurements are sensitive to flow over a wide range of vessel diameters and flow rates. This model of vascular structure may serve well for other MR measurements that are sensitive to perfusio

ISSN:0740-3194    

DOI:10.1002/mrm.1910320407

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

年代:1994

数据来源: WILEY

摘要:

AbstractA noninvasive investigation of the structure of hemopoietic bone marrow is based on the determination of the magnetic field distribution within small volume elements in vertebral bodies by localized1H MR spectroscopy. In patients with he‐matological diseases the status of the bone marrow was found to considerably influence the homogeneity of the magnetic field in trabecular bonein vivo.The line widths of the1H signals were evaluated in follow‐up studies during initial chemotherapy of eight patients with leukemia. lntraindividual comparison revealed significant broadening of the field distribution after a few weeks of cytotoxic treatment in five of the patients. Additionally, 19 patients after bone marrow transplantation showed significantly broader field distributions in the lipid signals than 13 matched healthy volunteers. These alterations of the microscopic field homogeneity were not caused by trabecular density effects. Iliac crest biopsies revealed high amounts of hemosiderin in the cases with broadened line widths. Ten of the 19 patients after bone marrow transplantation showed high amounts of hemosiderin and broad lines in the spectra. The content of hemosiderin of the other patients was not significantly increa

ISSN:0740-3194    

DOI:10.1002/mrm.1910320408

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

年代:1994

数据来源: WILEY

摘要:

AbstractTime‐resolved velocity imaging using the magnetic resonance phase contrast technique can provide clinically important quantitative flow measurementsin vivobut suffers from long scan times when based on conventional spin‐warp sequences. This can be particularly problematic when imaging regions of the abdomen and thorax because of respiratory motion. We present a rapid phase contrast sequence based on an interleaved spiral k‐space data acquisition that permits time‐resolved, three‐direction velocity imaging within a breath‐hold. Results of steady and pulsatile flow phantom experiments are presented, which indicate excellent agreement between our technique and through plane flow measurements made with an in‐line ultrasound probe. Also shown are results of normal volunteer studies of the carotids, renal arteri

ISSN:0740-3194    

DOI:10.1002/mrm.1910320409

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

年代:1994

数据来源: WILEY

摘要:

AbstractSequentialin vivoMRI studies of experimental spinal cord injuries (SCI) were performed using a three‐dimensional implementation of the FATE (Fast low‐Angle spin echo sequence with shortTE) sequence. MRI‐observed pathology was quantified using a multispectral segmentation algorithm. Neurological analysis was performed on the same animals concurrently, in addition to end‐point histology, for comparison with quantitative MRI results. These studies suggest that it is possible to use MRI to detect the onset of secondary injury in the spinal cord. The data also indicate that early detection of MRI‐visible pathology may provide the necessary markers for predicting the long‐term level of neurolo

ISSN:0740-3194    

DOI:10.1002/mrm.1910320410

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

年代:1994

数据来源: WILEY

摘要:

AbstractA major problem in the development of high field (>100 MHz) large volume (>6000 cm3) MR coils is the interaction of the coil with the subject as well as the radiation loss to the environment. To reduce subject perturbation of the coil resonance modes, a volume coil that uses an array of freely rotating resonant elements radially mounted between two concentric cylinders was designed for operation at 170 MHz. Substantial electromagnetic energy is stored in the resonant elements outside the sample region without compromising the efficiency of the overall coil. This stored energy reduces the effect of the subject on the circuit and maintains a highQ, facilitating the tuning and matching of the coil. The unloadedQof the coil is 680; when loaded with a head, it was 129. The ratio of 5.3 of the unloaded to loadedQsupports the notion that the efficiency of the coil was maintained in comparison with previous designs. The power requirement and signal‐to‐noise performance are significantly improved. The coil is tuned by a mechanism that imparts the same degree of rotation on all of the elements simultaneously, varying their degree of mutual coupling and preserving the overall coil symmetry. A thin radiofrequency shield is an integral part of the coil to reduce the radiation effect, which is a significant loss mechanism at high fields. MR images were collected at 4T using this coil design with high sensitivity andB1, homogene

ISSN:0740-3194    

DOI:10.1002/mrm.1910320411

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

年代:1994

数据来源: WILEY