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排序方式: 共有1337条查询结果,搜索用时 15 毫秒
1.
Intracranial circulation: pulse-sequence considerations in three- dimensional (volume) MR angiography 总被引:2,自引:0,他引:2
The technique and feasibility of magnetic resonance (MR) angiography of intracranial vessels were studied in 35 healthy volunteers. Variations in image orientation, repetition time (TR), and flip angle were evaluated to determine their effects on flow-related enhancement. Gradient modifications--including echo time (TE), motion compensation, bandwidth, and field of view--were also studied in an effort to reduce motion-induced phase shifts. Results indicated that a FISP (fast imaging with steady precession) sequence with a TR of 50 msec, TE of 15 msec, velocity compensation in the read and section-select directions, acceleration compensation in the read direction, anisotropic volume, and a 1.25-mm partition thickness produced three-dimensional angiographic MR images that were accurate and reproducible in the depiction of the major intracranial vessels. Difficulties with field of view, persistent signal void secondary to higher-order motion, and spatial resolution remain major problems requiring additional study. 相似文献
2.
Maxillary sinusitis in adults: an evaluation of placebo-controlled double-blind trials 总被引:1,自引:0,他引:1
BACKGROUND: In general practice, acute sinusitis is frequently diagnosed
and treated with antibiotics. OBJECTIVE: This study aimed to determine the
evidence for the effectiveness of antibiotic treatment in acute maxillary
sinusitis in adults by assessing the methodological quality of
placebo-controlled double-blind randomized trials. METHOD: An evaluation by
four raters through a 35-item scoring-scale for internal and external
validity of all placebo-controlled double-blind randomized trials on acute
sinusitis found between January 1966 and July 1996. RESULTS: Eighty-five
trials were excluded because they were not placebo-controlled,
double-blind, randomized, or were carried out in patients with chronic
sinusitis or in children. The three remaining trials were performed in
different populations (one in general practice) between 1973 and 1978. Only
one study claimed superiority of antibiotic treatment. Different inclusion
criteria and major outcome measures were used by the authors. The
reliability of major outcome events was reported poorly or not at all and
in two studies outcome measures were clinically inappropriate. The studies
scored 30-62% of the maximum attainable score for internal validity and
10-20% for external validity. CONCLUSION: The effectiveness of antibiotic
treatment in acute maxillary sinusitis in a general practice population is
not based sufficiently on evidence.
相似文献
3.
4.
V Z Agrba B A Lapin S V Novozhilov V V Timanovskaia M G Chikobava S V Semenova M T Ivanov V V Kakubava 《Voprosy virusologii》1991,36(2):130-133
Five continuous lymphoid suspension cell cultures were established by cultivation of lymphocytes from African green monkeys. The immunological typing revealed the mixed pattern of cultures consisting of B and T cell types. Two types of viruses: herpesvirus and retrovirus C-type were demonstrated by electron microscopy. Indirect immunofluorescence and molecular hybridization studies showed one of the viruses to be an EBV-related herpesvirus of green monkeys designated HVGM and the other to belong to H (S) TLV-1 group. 相似文献
5.
Digital image analysis of quantitative autoradiographic (QAR) films is widely used in neuroscience applications. Unless proper precautions are taken when autoradiographic images are converted to digital form they can be inadvertently modified by improper application of the sampling process. This type of modification is termed aliasing error and can cause nonexistent structures to appear in the reconstructed digital image, changing the apparent optical density values of the data. The theoretical basis of aliasing error is presented, along with examples of aliasing from optical resolution test patterns and 2-deoxy[14C]glucose (2-DG) experimental QAR images. We show that aliasing can change the apparent shape of structures, as well as the derived values obtained from QAR experiments. In an example with experimental 2-DG images, aliasing in the cerebellar cortex consistently underestimates tissue radioactivity levels in gray matter (P less than 0.001) and overestimates levels in adjacent white matter (P less than 0.001). Additional data transformations, such as the equations used for blood flow or glucose utilization, can, somewhat unpredictably, accentuate the errors introduced by aliasing. We present a discussion of the autoradiographic image features and electronic design that play a role in introducing aliasing errors and means by which aliasing can be recognized and minimized. 相似文献
6.
H Angus-Leppan GA Lambert J Michalicek 《Cephalalgia : an international journal of headache》1997,17(6):625-630
Co-existence of facial and occipital pain may occur in occipital neuralgia, migraine and cluster headache; suggesting convergence of trigeminal and cervical afferents. Such convergence has been shown in humans and other animals, but the site and extent of this are uncertain. In anaesthetized adult cats, the superior sagittal sinus and occipital nerve were stimulated electrically, and extracellular recordings made in the dorsolateral area of the upper cervical cord using glass-coated tungsten electrodes. Of 49 units in 10 cats, 33 (67%) had input from the superior sagittal sinus and the occipital nerve. Thirteen (27%) had superior sagittal sinus input and 3 (6%) had occipital nerve input. Convergent receptive fields were identified mechanically in 7 units. These experiments in cats show convergent input from occipital nerve and superior sagittal sinus on dorsolateral area units in two-thirds of cases studied. This experimental site of trigeminocervical convergence may relate to referral of pain in occipital neuralgia and other headaches. 相似文献
7.
In patients with PG-dependent renal function, NSAID administration
constantly reduces GFR and RBF in a dose-dependent fashion. In this
situation, the risk of overt acute renal failure is high and should be
taken into proper account. In contrast, the incidence of NSAID-related
renal structural alterations appears to be very low, yet the absolute
number of patients may be significant considering the wide use of such
drugs. Concerning the antiproteinuric effect of NSAIDs, the unfavourable
ratio risk/benefit does not seem to support their indication in proteinuric
nephropathies. The development of PGHS-2 selective inhibitors is promising,
and may open new therapeutical strategies in the treatment of the
progression of renal disease.
相似文献
8.
9.
Low doses of the uncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist dizocilpine (MK-801) induce locomotor stimulation in mice, whereas higher doses are associated with ataxia, stereotyped behaviors and catalepsy. We investigated the role of dopamine receptors and presynaptic dopamine neurons in the locomotor effects of dizocilpine. For comparison, we studied several other drugs that induce locomotor stimulation in mice. Pretreatment of male mice with haloperidol (0.1 mg/kg, i.p.) completely prevented the stimulation of normally coordinated locomotion induced by a non-intoxicating dose of dizocilpine (0.1 mg/kg, i.p.); haloperidol also attenuated the locomotor stimulation produced by phencyclidine (PCP, 1 and 2 mg/kg, i.p.), d-amphetamine (2 and 5 mg/kg, i.p.) and diazepam (0.5 mg/kg, i.p.). Haloperidol (doses up to 2.5 mg/kg) did not attenuate the ataxia and decreased locomotion induced by higher doses of dizocilpine (1 and 2 mg/kg). The active cis isomer of flupenthixol (0.5 mg/kg, i.p.), an antagonist of both D1 and D2 dopamine receptors, also diminished the stimulant actions of all of the test drugs, whereas its inactive trans form did not. The selective D1 antagonist R(±)-SCH 23390 (0.1 mg/kg) and the selective D2 antagonist raclopride (1 mg/kg) had little effect on the stimulatory effect of dizocilpine, although they did reduce the stimulation produced by PCP, d-amphetamine and diazepam. However, pretreatment with a combination of R(±)-SCH 23390 and raclopride completely prevented dizocilpine-induced locomotor stimulation. Pretreatment with α-methyl-p-tyrosine (AMPT, 50 and 250 mg/kg), an inhibitor of tyrosine hydroxylase, or with 6-hydroxydopamine (6-OH-DA, 50 μg, i.c.v.), a neurotoxin that destroys brain dopaminergic and noradrenergic neurons, did not attenuate the locomotor stimulation induced by dizocilpine, although these treatments did reduce the stimulant effects of d-amphetamine. In AMPT or 6-OH-DA pretreated mice, haloperidol (0.125 mg/kg) prevented the stimulatory effect of dizocilpine. These results support a role for dopamine receptors in the stimulation of normally coordinated locomotion by dizocilpine. However, the locomotor stimulant effect of dizocilpine, unlike that of d-amphetamine, can be expressed in the presence of D1 or D2 dopamine receptor blockade and does not appear to be dependent on intact presynaptic mechanisms. 相似文献
10.