Impulse patterns of Ia afferents and Ia-activated DSCT neurons during sinusoidal muscle stretch in cats

Summary The cat gastrocnemius muscles of one hind leg were stretched sinusoidally with amplitudes between 10 m and 2.5 mm and frequencies between 1 and 30 Hz. The stretch response of deefferented muscle spindle afferents and of Ia-activated cells within Clarke's column were investigated by means of extra-cellular recordings of action potentials. The responses to 20–50 cycles were displayed in impulse patterns (raster diagrams) of the responding action potentials. The impulse patterns of Ia afferents exhibited a high degree of phase-locking (regularity) on the stretch cycle of amplitudes of about 50 m at 3 Hz and all higher amplitudes or frequencies. At comparable stretch parameters the regularity in Ia afferents was 4–6 times larger than in Ia-activated DSCT neurons. The regularity in the DSCT patterns increased with an increase in stretch frequency. The impulse patterns of DSCT cells exhibited a high negative correlation between successive interspike intervals (–0.4 to –0.6) at low stretch frequencies (<3 Hz), which decreased with an increase in stretch frequency.     

双源CT的Lung Care评估孤立性肺结节的应用价值研究

目的：探讨Siemens双源CT的Lung Care软件对孤立性肺结节的辅助诊断能力及适用范围。方法：收集双源CT扫描并经病理证实的肺内孤立性结节40例。应用Lung Care软件中的r-MPR或VOI法三维重建技术对SPN的基本征象进行分析,并与胸部CT常规扫描进行比较;其中20例肺结节患者于12个月内分3个阶段进行随访,以测量结节生长速度或倍增时间。结果：在40例SPN中,恶性结节28例,良性结节12例。胸部CT常规扫描与Lung Care软件三维重建对恶性结节诊断准确率分别为53.57%、82.14%,对良性结节诊断准确率分别为41.67%、83.33%,两者均有显著性差异（P〈0.05）。Lung Care软件具有的自动分析测量结节体积功能,可准确地计算出结节体积、X径、Y径、Z径、最大径、最小径,通过20例12个月内随访,8例结节体积增大,7例结节体积缩小,5例结节体积不变,8例体积增大的结节中5例手术切除,经病理证实均为恶性结节。结论：Lung Care软件对肺结节的诊断具有一定辅助作用,可以有效地鉴别结节真伪,观察结节的形态特征,适应于对肺结节的良恶性鉴别诊断。     

Quantification of left and right ventricular function and myocardial mass: comparison of low-radiation dose 2nd generation dual-source CT and cardiac MRI

Objective

To prospectively evaluate the accuracy of left and right ventricular function and myocardial mass measurements based on a dual-step, low radiation dose protocol with prospectively ECG-triggered 2nd generation dual-source CT (DSCT), using cardiac MRI (cMRI) as the reference standard.

Materials and methods

Twenty patients underwent 1.5 T cMRI and prospectively ECG-triggered dual-step pulsing cardiac DSCT. This image acquisition mode performs low-radiation (20% tube current) imaging over the majority of the cardiac cycle and applies full radiation only during a single adjustable phase. Full-radiation-phase images were used to assess cardiac morphology, while low-radiation-phase images were used to measure left and right ventricular function and mass. Quantitative CT measurements based on contiguous multiphase short-axis reconstructions from the axial CT data were compared with short-axis SSFP cardiac cine MRI. Contours were manually traced around the ventricular borders for calculation of left and right ventricular end-diastolic volume, end-systolic volume, stroke volume, ejection fraction and myocardial mass for both modalities. Statistical methods included independent t-tests, the Mann–Whitney U test, Pearson correlation statistics, and Bland–Altman analysis.

Results

All CT measurements of left and right ventricular function and mass correlated well with those from cMRI: for left/right end-diastolic volume r = 0.885/0.801, left/right end-systolic volume r = 0.947/0.879, left/right stroke volume r = 0.620/0.697, left/right ejection fraction r = 0.869/0.751, and left/right myocardial mass r = 0.959/0.702. Mean radiation dose was 6.2 ± 1.8 mSv.

Conclusions

Prospectively ECG-triggered, dual-step pulsing cardiac DSCT accurately quantifies left and right ventricular function and myocardial mass in comparison with cMRI with substantially lower radiation exposure than reported for traditional retrospective ECG-gating.     

Convergence of muscle spindle afferents on single neurons of the cat dorsal spino-cerebellar tract and their synaptic efficacy

By means of tungsten microelectrodes, action potentials from axons within the dorsal spino-cerebellar tract (DSCT) and from muscle spindle afferents were recorded. A quantitative study was performed in monomuscular DSCT neurons which were excited predominantly by Ia fibers originating in the gastrocnemius muscles. In some experiments single Ia fibers were stimulated electrically while the impulse sequence of a DSCT neuron postsynaptic to the respective afferent fiber was recorded. The gastrocnemius DSCT neurons receive excitatory inputs from 10-18 Ia muscle spindle afferents. The efficacy of each of these inputs is very similar. Thus the neuronal activation decreased approximately linearly with the number of the excitatory afferents cut. Cross-correlograms between the impulse sequence of a Ia gastrocnemius muscle spindle afferent and a DSCT neuron postsynaptic to it exhibited an increased discharge probability of the DSCT neuron from 3-4 ms to 10 ms after the Ia action potential. With increasing impulse rates of the Ia afferent fibers, the excitatory efficacy of the single action potential decreased, but the overall excitation increased with the presynaptic discharge frequency, according to a hyperbolic function. This effect was tested by electrical stimulation of a single Ia axon exciting the DSCT neuron recorded. Interval histograms computed from DSCT neuron impulse trains at steady stretch conditions were predominantly monomodal. They can be well approximated by a Gaussian distribution. The coefficient of variation was independent of the mean activity. At impulse rates above 25 imp X s-1 a negative correlation between successive intervals was observed in first order joint interval diagrams. With an increasing mean discharge rate this correlation (expressed as the serial linear correlation coefficient of the first order r1,2) became stronger up to--0.62 at 90 imp X s-1. Only in a few neurons did the higher order linear correlation coefficients deviate significantly from zero. In 15% of the observed histograms double discharging (mean interval 3-5 ms) produced bimodal distributions. Under steady-state conditions the response of Ia-activated DSCT cells are linearly related to muscle stretch within a middle range of extensions. The differences between Ia impulse pattern and DSCT neuron impulse pattern at steady stretch are discussed. The number of large dendrites of the principal cells in the nucleus dorsalis (Clarke's column) corresponds to the number of excitatory afferent muscle fibers. It is assumed that each excitatory Ia axon sends one axon collateral to the DSCT neuron, forming a climbing type terminal mainly on one of the large dendrites of a DSCT cell.     

Dual-source CT assessment of ventricular function in healthy and infarcted myocardium: An animal study

Purpose

To assess global and regional ventricular function in the presence of myocardial infarction (MI) using cardiac dual-source computed tomography (DSCT) in comparison to magnetic resonance (MR) imaging.

Materials and methods

Fourteen pigs (58.6 ± 8.9 kg) were included in this study. In seven animals acute MI was induced by temporary balloon occlusion of the left circumflex artery. Thereafter, DSCT and MR imaging were performed with standardized examination protocols. Left (LV) and right ventricular (RV) volumes, ejection fraction (EF), peak filling rate (PFR), and peak ejection rate (PER) as well as LV myocardial mass were calculated. LV wall motion was visually assessed from cine loops. Data was analyzed using Bland-Altman plots, Lin's concordance-correlation coefficient (ρ_c) and weighted kappa statistics.

Results

Ventricular volumes and mass as determined by DSCT correlated well with MR imaging. Mean LV-EF was 49.4 ± 16.5% on DSCT and 50.0 ± 16.1% on MR imaging (ρ_c = 0.9928). The corresponding mean RV-EF results were 45.9 ± 10.6% and 45.8 ± 10.6% (ρ_c = 0.9969), respectively. Bland-Altman plots revealed no systematic errors, but PER and PFR showed a relevant scattering. Regional wall motion scores agreed in 216/224 myocardial segments (κ = 0.925).

Conclusion

DSCT permits the reliable assessment of global and regional function in healthy and infarcted myocardium, but is not yet suited for the assessment of dynamic functional parameters like PER and PFR.     

Prevalence of noncardiac findings in computed tomography angiography before transcatheter aortic valve replacement

ObjectiveThis study sought to determine the prevalence of significant and nonsignificant noncardiac findings in patients undergoing preprocedural dual-source CT (DSCT) before transcatheter aortic valve implantation (TAVI).MethodsPatients (n = 204; aged, 80.5 ± 5.1 years; 106 men) underwent preprocedural DSCT of the thoracoabdominal aorta and the pelvic arterial vessels. Noncardiac findings were recorded and categorized as nonsignificant (group A), incidental findings requiring follow-up examinations (group B), and significant findings with a demand for clinical treatment (group C).ResultsIn 60 of 204 DSCT examinations (29.4%) no noncardiac findings were observed. Of the remaining 144 examinations (70.6%), 260 had noncardiac findings; 35 of 204 patients (17.1%) had a total of 37 clinically significant noncardiac findings. Eight malignancies were detected; 5 of them were incidentally diagnosed on DSCT and changed patient management. A total of 223 nonsignificant findings were observed in 116 of 204 patients (56.9%; group A), the most frequent findings were pleural effusions or colorectal diverticulosis. The prevalence of incidental and significant findings on DSCT before TAVI increased with patient age (r² = 0.69; P = .01).ConclusionSignificant noncardiac findings are common in patients referred to routine preprocedural DSCT for planning TAVI (17.1%).     

双源CT在主动脉瓣置换术前左心功能评价中的应用

目的:以磁共振成像(MRI)为金标准,用双源CT(DSCT)定量评价左心功能,探讨DSCT在主动脉瓣置换术前左心功能评价中的应用价值.方法:选取临床诊断主动脉瓣病变欲行主动脉瓣置换术的患者21例,全部病例均行DSCT和MRI心功能分析检查.由有经验的2位放射科医生独立进行,结果以均数士标准差表示.两种仪器间测量值应用配对样本t检验及相关分析检验,同一仪器测量值的差异相互关系用组内相关系数描述,P ＜0.05为有统计学意义.结果:DSCT和MRI两种方法测量的心功能指标差异无统计学意义,舒张末期容积(EDV)、收缩末期容积(ESV)、每搏输出量(SV)、左室射血分数(EF)相关性高,r值(EDV)=0.93,r值(ESV)=0.94,r值(SV)=0.89,r值(EF)=0.85.EDV均值:DSCT＞ MRI;ESV均值:DSCT＞ MRI;SV均值:DSCT＞ MRI; EF均值:DSCT＞ MRI.同一仪器三次测量值的差异相互关系(ICC值):MRI测量的EDV、ESV、SV、EF值的ICC值在0.8～1之间;DSCT测量的EDV、ESV、SV、EF值的ICC值在0.6～0.75之间.结论:DSCT在左心室收缩功能定量评价方面准确、可靠,重复性好,并可在不增加放射剂量的前提下,一次DSCT冠状动脉造影检查同时评估冠状动脉狭窄情况和左心室收缩功能,能够为临床主动脉瓣置换术前评估及制订手术方案提供更多重要的参考信息.     

双源CT诊断非金属可疑食管异物的队列研究

目的通过分析双源CT诊断非金属食管异物的敏感性和特异性,评价双源CT对非金属可疑食管异物的诊断意义。方法应用前瞻性队列研究,选取2015年1月1日～2016年12月31日符合纳入标准的患者153例双源CT和正侧位平片对照。结果93例双源CT阳性示食管异物,其中57例平片阳性;内镜检查证实并取出92例,内镜检查阴性1例。本组病例中双源CT敏感性100%（92/92）,特异性98.4%（60/61）,阴性预测值100%（60/60）。结论双源CT检查非金属食管异物敏感性、特异性、阴性预测值高,能明确异物类型及异物位置。双源CT可作为非金属食管异物的常规检查,及时诊断,避免不必要的食管内镜检查。     

Corticofugal influences on transmission to the dorsal spinocerebellar tract from hindlimb primary afferents

Summary Effects from the cerebral cortex on neurones of the dorsal spinocerebellar tract (DSCT) were examined: I. In group I units (units receiving monosynaptic excitation from group I fibres) repetitive stimulation of the contralateral sensorimotor cortex usually inhibited impulse transmission from the primary afferents. The inhibition had a latency of 10–20 msec and lasted for 82-100 msec or more. Discharges induced by muscle stretch were also inhibited by the cortical stimulation. DSCT units belonging to extensors and flexors were both inhibited from the cortex. In a small percentage of group I units the inhibition was preceded by a shorter-lasting excitation. 2. FRA units (units receiving excitation from cutaneous and/or high threshold muscle afferents) were typically excited by the cortical stimulation. The excitation was often followed by a period of depression of transmission from the periphery. 3. It is suggested from the effective cortical area and experiments with lesions in the medullary pyramid and in the spinal cord that the inhibition in group I units and the excitation of FRA units are both mediated by the corticospinal tract.Experiments were also made to determine the level where the cell body of a given DSCT unit is located, and the results from 56 units are presented.