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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
4.
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
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Posterior chamber intraocular lenses in a series of 75 autopsy eyes. Part I: Loop location 总被引:1,自引:0,他引:1
D J Apple S B Park K H Merkley R N Brems S C Richards K E Langley K L Piest R A Isenberg 《Journal of cataract and refractive surgery》1986,12(4):358-362
Over a period of 27 months, November 1983 to February 1986, 75 eyes obtained postmortem with posterior chamber intraocular lenses (IOLs) were examined at the Center for Intraocular Lens Research, University of Utah Health Sciences Center. These IOLs were studied by histopathological techniques to determine the location of the loops. The most common combination, found in 47% of the specimens, was one loop in the lens capsular sac (bag) and one loop in the ciliary sulcus. In 32% of the specimens, both loops were in the capsular sac; in 17%, both loops were in the ciliary sulcus. Compared to results observed in other autopsy studies, in which capsular fixation was documented in less than 3% of cases, these findings reflect a trend toward capsular sac (in-the-bag) implantation of open-looped posterior chamber IOLs. 相似文献
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W Bencivelli C Vitali D A Isenberg J S Smolen M L Snaith M Sciuto S Bombardieri 《Clinical and experimental rheumatology》1992,10(5):549-554
In the first phase of this study, a data-base containing clinical and laboratory findings of 704 patients with systemic lupus erythematosus (SLE), originating from 29 centres and 14 countries, was used to assess the validity of 4 common indices of disease activity, SLAM, BILAG, SLEDAI and SIS. The physician's judgement of activity was assumed as the unique reference criterion (gold standard). Computer programmes were developed to calculate automatically the 4 activity indices; this computation appeared to correspond with manual computations in a sample of 60 appropriately selected cases. All 4 indices were closely correlated with each other (r in the range of 0.716 to 0.872), and with the physician's score (r in the range of 0.620 to 0.719). In the second phase of the study the activity index developed in part I (ECLAM) was prospectively validated, and its performance compared to that of the other scales, both as a single state index and as a transition index (i.e., its ability to assess disease activity at a single point in time and to detect variations in consecutive readings). A computer-assisted clinical chart was prepared for this purpose. This chart allowed us to calculate automatically all the indices. Two consecutive observation times (time 0, and time 1 three months later) were included in the study protocol. Data on 75 patients from 19 centres were collected, and each patient was observed twice. All the computed indices were closely correlated, both at time 0 (r ranging from 0.725 to 0.884), and at time 1 (r ranging from 0.607 to 0.833).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
10.
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