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排序方式: 共有229条查询结果,搜索用时 15 毫秒
61.
Li N Jia X Murari K Parlapalli R Rege A Thakor NV 《Journal of neuroscience methods》2009,176(2):230-236
Previous studies have implicated the abnormal activation of the trigeminal system to be a factor in the pathogenesis of migraine. The relationship between vascular changes and migraine, however, is under considerable debate. In this study, temporal laser speckle contrast imaging is combined with ridge tracking based vessel detection to obtain high resolution (6.7 microm x 6.7 microm), high contrast images of cerebral vascular structure. For the first time, the vasomotor and blood flow responses to electrical stimulation in rat peripheral trigeminal system were obtained simultaneously. The system is capable of picking up individual vessels with diameters down to 30 microm. The spatial spread of the blood velocity response relative to the point of stimulation was studied. Analysis of branching vessels showed a 50+/-5% vs. 30+/-5% change in mean peak magnitude and a 54% per second vs. 17% per second change in mean rate of increase for vessels proximal vs. distal to the stimulation site. The penetration depth of the laser used was proven to be sufficient to image dural as well as cortical vessels through a thinned skull preparation. Different responses were observed from cortical and dural vessels. While the diameter of cortical vessels did not change in response to the stimulation the blood velocity went up by 65+/-5% per second. Dural vessels enlarged by 40+/-8% and the blood velocity increased by 50+/-5%. The method described here could be very useful in understanding and studying disorders in the neurovascular system. 相似文献
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64.
SA Pungavkar MA Lawande DP Patkar NV Agrawal S Gadani 《Journal of Medical Imaging and Radiation Oncology》2005,49(6):489-492
Optic nerve glioma is the most common primary neoplasm of the optic nerve in childhood. It can extend intracranially along the optic pathway (optic pathway glioma). The lesion tends to present with decreased visual acuity in the affected eye, but can cause additional symptoms when it is large. Local involvement within the orbit can be characterized using CT, but MRI is superior in showing the intracranial extent of the lesion. Intracranial calcification in optic pathway glioma is rare. We present a rare case of optic pathway glioma with calcification in the intracranial component. Also, we describe MR spectroscopy (MRS) findings in this case. 相似文献
65.
Optical imaging, such as transmission imaging, is used to study brain tissue injury. Transmission imaging detects cellular swelling via an increase in light transmitted by tissue slices due to a decrease in scattering particle concentration. Transmission imaging cannot distinguish sub-cellular particle size changes from cellular swelling or shrinkage. We present an optical imaging method, based on Mie scatter theory, to detect changes in sub-cellular particle size and concentration. The system uses a modified inverted microscope and a 16-bit cooled CCD camera to image tissue light scatter at two angles. Dual-angle scatter ratio imaging successfully discriminated latex microsphere suspensions of differing sizes (0.6, 0.8, 1 and 2 microm) and concentrations. We applied scatter imaging to hippocampal slices treated with 100 microM N-methyl-D-aspartate (NMDA) to model excitotoxic injury or -40 mOsm hypotonic perfusion solution to cause edema injury. We detected light scatter decreases similar to transmission imaging in the CA1 region of the hippocampus for both treatments. Using our system, we could distinguish between NMDA and hypotonic treatments on the basis of statistically significant (P<0.0003) differences in the scatter ratio measured in CA1. Scatter imaging should be useful in studying tissue injuries or activity resulting in brain tissue swelling as well as morphological changes in sub-cellular organelles such as mitochondrial swelling. 相似文献
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67.
Noise and motion artefacts interfere with ambulatory ECG recording. In the paper the hypothesis that proper skin preparation
and electrode design and placement could reduce the artefact levels is tested. The comparison of four commercial electrodes
shows differences in adhesive strength and levels of skin irritation but does not indicate significant differences in the
artefact levels produced by the electrodes. Four treatments are compared—no skin preparation, rubbing with alcohol, abrasion
and puncturing—for their effectiveness in reducing motion artefact. Skin preparations do not reduce the motion artefact significantly
but cause much discomfort. Therefore, skin preparation is not recommended. We recorded the signal (QRS complex) to-noise (artefact
at the electrode site) ratio at 15 thoracic locations and recommend two pairs for ambulatory ECG recording. The statistical
experimental design procedures used can also be adopted for comparison and testing for improvement of other electrode properties
and designs. 相似文献
68.
Ventricular fibrillation detection by a regression test on the autocorrelation function 总被引:3,自引:0,他引:3
S. Chen Dr N. V. Thakor M. M. Mower 《Medical & biological engineering & computing》1987,25(3):241-249
The paper investigates quantitative differences in the signal characteristics of ventricular fibrillation (VF) and other cardiac
arrhythmias. The analysis procedure comprises two steps: calculation of a short-term autocorrelation function (ACF) followed
by a regression test on a plot of peak magnitudes of the ACF against lag values (the ACF/lag plot). We detect VF by testing
the hypothesis that the ACF/lag plot of VF does not pass a linear regression test. Analysis of 31 separate episodes (of VF
and other ventricular arrhythmias), each comprising three successive segments of 1·5s each produced the following results:
(1) 100 per cent sensitivity (Se), 62 per cent specificity (Sp) and 74 per cent test efficiency (TE) after analysis of the
first segment; (2) 100 per cent Se, 86 per cent Sp and 90 per cent TE after the second segment; and (3) 100 per cent Se, 100
per cent Sp and 100 per cent TE after the third segment. This method quantifies the notion that VF signals are nonperiodic
with a random amplitude distribution, whereas ventricular tachycardia (VT) signals are usually periodic with more uniform
amplitude distributions. Accurate discrimination and identification of VF can be very important in intensive-care settings,
as well as in the design of automatic cardioverters and defibrillators. 相似文献
69.
70.
Autosomal recessive retinitis pigmentosa and cone-rod dystrophy caused by splice site mutations in the Stargardt's disease gene ABCR 总被引:12,自引:2,他引:12
Cremers FP; van de Pol DJ; van Driel M; den Hollander AI; van Haren FJ; Knoers NV; Tijmes N; Bergen AA; Rohrschneider K; Blankenagel A; Pinckers AJ; Deutman AF; Hoyng CB 《Human molecular genetics》1998,7(3):355-362
Ophthalmological and molecular genetic studies were performed in a
consanguineous family with individuals showing either retinitis pigmentosa
(RP) or cone-rod dystrophy (CRD). Assuming pseudodominant (recessive)
inheritance of allelic defects, linkage analysis positioned the causal gene
at 1p21-p13 (lod score 4.22), a genomic segment known to harbor the ABCR
gene involved in Stargardt's disease (STGD) and age- related macular
degeneration (AMD). We completed the exon-intron structure of the ABCR gene
and detected a severe homozygous 5[prime] splice site mutation,
IVS30+1G->T, in the four RP patients. The five CRD patients in this
family are compound heterozygotes for the IVS30+1G- >T mutation and a
5[prime] splice site mutation in intron 40 (IVS40+5G- >A). Both splice
site mutations were found heterozygously in two unrelated STGD patients,
but not in 100 control individuals. In these patients the second mutation
was either a missense mutation or unknown. Since thus far no STGD patients
have been reported to carry two ABCR null alleles and taking into account
that the RP phenotype is more severe than the STGD phenotype, we
hypothesize that the intron 30 splice site mutation represents a true null
allele. Since the intron 30 mutation is found heterozygously in the CRD
patients, the IVS40+5G->A mutation probably renders the exon 40 5[prime]
splice site partially functional. These results show that mutations in the
ABCR gene not only result in STGD and AMD, but can also cause autosomal
recessive RP and CRD. Since the heterozygote frequency for ABCR mutations
is estimated at 0.02, mutations in ABCR might be an important cause of
autosomal recessive and sporadic forms of RP and CRD.
相似文献