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排序方式: 共有550条查询结果,搜索用时 15 毫秒
1.
Fast CT-PRESS-based spiral chemical shift imaging at 3 Tesla. 总被引:2,自引:0,他引:2
Dirk Mayer Dong-Hyun Kim Elfar Adalsteinsson Daniel M Spielman 《Magnetic resonance in medicine》2006,55(5):974-978
A new sequence is presented that combines constant-time point-resolved spectroscopy (CT-PRESS) with fast spiral chemical shift imaging. It allows the acquisition of multivoxel spectra without line splitting with a minimum total measurement time of less than 5 min for a field of view of 24 cm and a nominal 1.5x1.5-cm2 in-plane resolution. Measurements were performed with 17 CS encoding steps in t1 (Deltat1=12.8 ms) and an average echo time of 151 ms, which was determined by simulating the CT-PRESS experiment for the spin systems of glutamate (Glu) and myo-inositol (mI). Signals from N-acetyl-aspartate, total creatine, choline-containing compounds (Cho), Glu, and mI were detected in a healthy volunteer with no or only minor baseline distortions within 14 min on a 3 T MR scanner. 相似文献
2.
Familial and sporadic hyperinsulinism: histopathologic findings and segregation analysis support a single autosomal recessive disorder 总被引:4,自引:0,他引:4
P S Thornton A E Sumner E D Ruchelli R S Spielman L Baker C A Stanley 《The Journal of pediatrics》1991,119(5):721-724
We evaluated the possible genetic contribution to hyperinsulinism in a series of patients seen during the past 15 years. Of 26 families, 5 (19%) had more than one child affected (multiplex family). There were no apparent differences between patients in the 5 multiplex and 21 simplex families, clinically, biochemically, or on histologic examination of the pancreatic specimens. The families studied had a total of 63 offspring; the 26 index patients had 37 siblings, 6 of whom were affected. After four patients with hyperinsulinism caused by adenoma were excluded from the study, segregation analysis was carried out to test the data for agreement with results expected if familial and isolated hyperinsulinism represented a single disease with recessive mode of inheritance and a segregation ratio of 0.25. Excellent agreement was found between the observed number of affected siblings (20) and the expected number (19.65), with a segregation ratio of 0.254. The results were consistent with the hypothesis that in most or all cases, hyperinsulinism is inherited as an autosomal recessive disease. There was no evidence of distinct familial and sporadic types. 相似文献
3.
The cost of losing: an analysis of commercial weight-loss programs in a metropolitan area. 总被引:1,自引:0,他引:1
A B Spielman B Kanders M Kienholz G L Blackburn 《Journal of the American College of Nutrition》1992,11(1):36-41
Thirty-four million adult Americans are obese (greater than 30% above ideal body weight). 1990 national Health Objectives state that 50% of all adults should adopt weight-loss and exercise regimes. This recommendation has caused a dramatic surge in the number and variety of weight-loss programs currently available. A parallel surge has occurred in the cost of these weight-loss programs. This wide variation in personal expenditure (and treatment provided) necessitates a review of the programs and their cost to the participant. The cost of a 12-week outpatient commercial weight-loss program can range from $2,120 for the most expensive very low-calorie diet program to $108 for the least expensive nutrient-balanced hypocaloric diet program. This article reviews 11 commercial diet programs in the Boston area and analyzes the out-of-pocket cost paid to the clinic by the participant to lose 1 kg on each program. Given the complexity of treatment to achieve long-term weight control, knowledge of financial obligations is important. 相似文献
4.
Dirk Mayer Wolfgang Dreher Dieter Leibfritz Daniel M Spielman 《Magnetic resonance in medicine》2007,57(5):967-971
A numerical simulation tool was developed to calculate the echo amplitudes of J-coupled resonances within a series of radiofrequency (RF) refocused echoes. The signal modulation due to J-coupling in rapid acquisition with relaxation enhancement (RARE) is suppressed only when the inverse of the pulse interval (tau) is large compared to both the chemical shift (CS) difference (Deltadelta) of the coupled spins and the coupling constant. In contrast, the echo amplitudes in ultrafast low-flip-angle RARE (U-FLARE) oscillate around a quasi-steady-state value that is greater than zero (neglecting relaxation and diffusion) even when Deltadelta > 1/tau. The flip-angle distribution over the measured slice caused by the use of Gaussian-shape slice-selective refocusing pulses further reduces the echo oscillations. When the pulse interval falls short of the fast pulse rate regime, spectroscopic U-FLARE provides an improved spatial impulse response in the phase-encoding (PE) direction compared to spectroscopic RARE. 相似文献
5.
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7.
Thomas Adams William S. Spielman Kenneth R. Holmes S. R. Heisey Michael M. Chen 《Annals of biomedical engineering》1985,13(3-4):237-258
The kidney, with its heterogeneous regional perfusion in the two anatomically and functionally distinct vascular beds of the
renal cortex and medulla, and with its nonuniform blood vessel geometries, presents a unique challenge for measuring intrarenal
blood flow distribution. Determining whole organ perfusion, on the other hand, is comparatively simple for the kidney, but
it provides relatively little information about the suspected dependency of renal excretory function on local perfusion rate.
Among the variety of methods proposed for gauging regional renal blood flow, some depend on measuring one or more of the tissue's
thermal properties. The most straightforward, but least reliable, involve measurements either of focal tissue temperature
alone, or of regional tissue thermal gradients. Simply using heat as a diffusible indicator, however, is unreliable as a measure
of blood flow, for many of the same reasons that using an inert gas in a dilution technique is unreliable. Recently developed
thermal analytical methods, though, hold promise for measuring local tissue blood flow with accuracy and precision. Two of
them are reviewed here. One depends on measurement of the effective thermal conductivity of a small mass of tissue by evaluating
the steady state ratio between regional unidirectional heat flux across it and the associated temperature gradient in one
vector along a segment of it through an imposed spheroidal heat field. The other depends on analyses of tissue temperature
decay subsequent to a controlled pulse of heat delivered through a small inserted thermistor bead. Both techniques use bioheat
transfer equations to deduce regional blood flow
Research by K.R. Holmes and M.M. Chen was supproted by NIH-NHLBI Grant HL27011, that by T. Adams and S.R. Heisey through the
Michigan Heart Association, and that by W.S. Spielman through a grant from the NSF (PCM 8110588) who is a recipient of NIH
Research Career Development Award HL01010. 相似文献
8.
To standardize the procedure for isolating and culturing Lyme disease spirochetes, we modified the composition of the medium generally used for this purpose (BSK-II) and developed a system for its distribution. This medium contains no gelatin or agarose, and various components are used in proportions that differ from those in BSK-II. Each of the major proteinacious components was screened by substitution in samples of the complete product. The final medium was evaluated for the capacity to grow related spirochetes including Borrelia burgdorferi N40, Guilford, and JD-1 as well as strains of Borrelia hermsii (HS-1) and of Borrelia coriaceae (CO53). Each isolate developed from inocula containing as few as one to five organisms. Doubling time of B. burgdorferi during log-phase growth at 37 degrees C was 10 to 12 h. Lyme disease spirochetes were isolated in this medium from ear punch biopsies and dermal aspirates from naturally infected mice and rabbits, from dermal biopsies from a human patient, and by sampling field-collected deer ticks (Ixodes dammini). Cultured spirochetes remained infective to mice and to ticks. The medium can be stored at -20 degrees C or lower temperatures for at least 8 months without effect on its ability to support growth of small inocula to densities exceeding 10(8) spirochetes per ml. Lyme disease spirochetes remained infective to mice after being stored at -80 degrees C in this medium for at least 8 months. We anticipate that the availability of this standardized medium (Sigma Chemical Co.), supplemented with prescreened rabbit serum, will facilitate comparison of research results between laboratories and may eventually permit definitive clinical diagnosis of Lyme disease based on demonstration of the pathogen. The standardized medium is designated BSK-H. 相似文献
9.
Accelerated transmission of Lyme disease spirochetes by partially fed vector ticks. 总被引:3,自引:3,他引:3
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To determine how rapidly Lyme disease spirochetes (Borrelia burgdorferi) can be transmitted by partially fed vector ticks (Ixodes dammini), attached nymphs were removed from their hosts at various intervals post-attachment and subsequently permitted to re-feed to repletion on noninfected mice. We confirm previous reports that ticks deposit Lyme disease spirochetes in the skin of their hosts mainly after 2 days of attachment. Those that have been removed from a host within this interval can reattach and commence feeding. Spirochete-infected nymphs that have previously been attached to a host for 1 day become infectious to other hosts within another day. Noninfected nymphs acquire infection from spirochete-infected hosts within a day of attachment and become infectious to other hosts 3 to 5 days later. Virtually all ticks transmitted infection when reattaching after first feeding for 2 days. We conclude that partially fed nymphal ticks transmit spirochetal infection more rapidly than do ticks that have never been attached to a host and that infected ticks become infectious before they molt. 相似文献
10.
Seasonal activity of immature Ixodes dammini (Acari: Ixodidae) 总被引:2,自引:0,他引:2