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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
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Paediatric dacryocystorhinostomy 总被引:1,自引:0,他引:1
KN Hakin FRCS FRCOphth TJ Sullivan FRACO FRACS A Sharma FCOphth † RAN Welham FRCS FCOphth † 《Clinical & experimental ophthalmology》1994,22(4):231-235
Of 258 cases of dacryocystorhinostomy performed on children in the period September 1981 to September 1991, 130 were for simple, unresolved congenital nasolacrimal duct obstruction. Other indications for surgery included punctal agenesis, lacrimal fistula, post-traumatic and post-inflammatory canalicular obstruction. Of 177 children without canalicular pathology, 171 (96%) were relieved of symptoms with one operation, without canalicular intubation. Of 81 cases with canalicular disease, 55 of 70 (79%) who underwent DCR plus canalicular intubation, and 10 of 11 who underwent DCR plus Lester-Jones tube, were substantially improved with one operation. No child required peroperative or postoperative blood transfusion. Dacryocystorhinostomy in childhood, in experienced surgical hands, is a safe procedure, achieving relief of symptoms in most cases, particularly in the absence of canalicular disease. 相似文献
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Factors influencing women to undergo screening mammography 总被引:2,自引:0,他引:2
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The purpose of this study was to evaluate the reproducibility of visual analog scale ratings of the effort to breathe (VASe) and the degree of discomfort evoked by breathing (VASd) in patients with chronic obstructive pulmonary disease (COPD) during exercise. Six subjects with moderately severe COPD (FEV1 = 1.12 +/- 0.29 L, FEV1/FVC = 44 +/- 4%) underwent progressive incremental exercise testing to a symptom-limited maximum every week for 8 wk. VASe and VASd were highly correlated in each subject (r = 0.99 +/- 0.01). The slope of the VASd/VASe relationship for all trials in all subjects was not significantly different from 1, indicating that our subjects were rating a common sensation with the two scales. VASe at maximal exercise was reproducible in every subject; the within-subject coefficient of variation (CV) was 6% (range, 2 to 10%) and compared favorably with physiologic indices: 7% (range, 3 to 12%) for oxygen consumption and 10% (range, 5 to 16%) for minute ventilation (VI). In contrast, submaximal VAS ratings were highly variable. At 66% of the maximal work load, the within-subject CV for VASe was 21% (range, 11 to 28%) compared with 6% (range, 4 to 7%) for VO2 (p less than 0.003) and 10% (range, 5 to 16%) for VI (p less than 0.01). VASe correlated linearly with VI and VO2 in all subjects in all trials. However, within an individual subject the slope and position of these relationships varied widely between trials.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
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