Joint maximum likelihood estimation of activation and Hemodynamic Response Function for fMRI

Blood Oxygen Level Dependent (BOLD) functional magnetic resonance imaging (fMRI) maps the brain activity by measuring blood oxygenation level, which is related to brain activity via a temporal impulse response function known as the Hemodynamic Response Function (HRF). The HRF varies from subject to subject and within areas of the brain, therefore a knowledge of HRF is necessary for accurately computing voxel activations. Conversely a knowledge of active voxels is highly beneficial for estimating the HRF. This work presents a joint maximum likelihood estimation of HRF and activation based on low-rank matrix approximations operating on regions of interest (ROI). Since each ROI has limited data, a smoothing constraint on the HRF is employed via Tikhonov regularization. The method is analyzed under both white noise and colored noise. Experiments with synthetic data show that accurate estimation of the HRF is possible with this method without prior assumptions on the exact shape of the HRF. Further experiments involving real fMRI experiments with auditory stimuli are used to validate the proposed method.     

右美托咪定用于减轻颅内动脉瘤患者麻醉诱导期血流动力学波动的临床价值

目的 探讨右美托咪定在颅内动脉瘤介入手术全身麻醉诱导期减少血流动力学波动中的应用.方法 选择全身麻醉下行颅内动脉瘤介入手术的患者60例,采用随机数字表法分为低剂量芬太尼组、高剂量芬太尼组和低剂量芬太尼复合右美托咪定组(复合组),每组20例.麻醉诱导前,复合组经微量泵持续静脉注射右美托咪定,总量1μg/kg,泵注时间10 min;低剂量芬太尼组和高剂量芬太尼组注射等量0.9％氯化钠.麻醉诱导时,低剂量芬太尼组和复合组静脉注射芬太尼3μg/kg、高剂量芬太尼组静脉注射芬太尼5μg/kg,余用药相同.记录入手术室平静休息3 min (T0)、气管内插管前即刻(T1)、插管后即刻(T2)、插管后3 min (T3)的收缩压(SBP)、舒张压(DBP)、心率(HR).将每例患者麻醉诱导期间(T0～T3)SBP、DBP、HR最大值与最小值之差定义为各参数的波动值:△SBP、△DBP、△HR.记录诱导期间麻黄碱、阿托品的使用情况.结果 复合组△SBP、△DBP、△HR[(26.9±14.8) mm Hg(1 mm Hg =0.133 kPa)、(10.7±8.9) mm Hg、(12.5±4.3)次/min]均低于低剂量芬太尼组[(40.4±15.6) mm Hg、(20.3±9.4) mm Hg、(30.1±15.0)次/min](P＜ 0.05),高剂量芬太尼组△SBP、△HR [(29.8±16.8) mm Hg、(19.5±7.4)次/min]均低于低剂量芬太尼组(P＜0.05),复合组△HR低于高剂量芬太尼组(P＜0.05).麻醉诱导期三组阿托品使用率比较差异无统计学意义(P=0.364),高剂量芬太尼组麻黄碱使用率高于低剂量芬太尼组[30％(6/20)比5％(1/20),P=0.032].结论 麻醉诱导前应用1μg/kg右美托咪定,既能够良好抑制插管反应,又不会导致插管后血压严重下降,达到了稳定血流动力学的目标,特别适用于颅内动脉瘤患者的麻醉诱导.     

右室双部位起搏与双室同步起搏的急性血液动力学对比研究

比较右室双部位 (RV Bi)起搏和双室 (BiV)同步起搏对血液动力学的影响 ,并与右室心尖部 (RVA)、右室流出道 (RVOT)、左室基底部 (LVB)起搏相比较 ,明确双部位起搏是否优于单部位起搏。 15例患者中病窦综合征 8例、Ⅲ度房室阻滞 7例。分别行RVA、RVOT、LVB、RV Bi、BiV起搏 (VVI,6 0～ 90次 /分 ) ,测定心输出量 (CO)和心脏指数(CI)、肺毛细血管嵌顿压 (PCWP)和QRS波时限 (QRSd)。结果 :①与RVA起搏相比 ,RVOT、LVB、RV Bi、BiV起搏CI分别增加了 7.5 %、11.3%、15 .5 %和 17.2 % ,PCWP分别降低了 14.9%、10 .3%、2 1.7%和 2 0 .0 % (P均 <0 .0 1)。②RV Bi、BiV起搏较RVOT、LVB起搏的CO、CI增高而PCWP降低 (P均 <0 .0 5 )。③RV Bi与BiV起搏、RVOT与LVB起搏之间CO、CI和PCWP无显著差异。④RVOT、RV Bi、BiV起搏的QRSd(分别为 12 8± 11,111± 16 ,10 3± 13ms)较RVA起搏 (146± 18ms)时显著缩短 (P≤ 0 .0 0 1) ,而LVB起搏 (142± 15ms)与RVOT、RVA起搏时无显著差异。结论 :RV Bi起搏和BiV同步起搏的急性血液动力学效果无明显差异 ,但双部位起搏的效果明显优于单部位起搏 ;双部位起搏的QRSd也比单部位起搏明显缩短     

Effect of dopamine on hemodynamics and cerebral oxygen metabolism in the early stage-of post-resuscitation in rabbit with cardiac arrest北大核心CSCD

Objective To observe the effects of dopamine in different doses on hemodynamics and cerebral oxygen metabolism in the early stage of post-resuscitation in rabbit with cardiac arrest. Methods Healthy adult rabbits were randomly(random number) divided into 4 groups according to the different doses of dopamine administration: control group (CG), low dose group (LG), medium dose group (MG), high dose group (HG), (n=15 in each group). Ventricular fibrillation (VF) was induced by electricity and cardiopulmonary resuscitation (CPR) was performed subsequently as the experiment designed. When 10 rabbits with restoration of spontaneous circulation (ROSC) were got each group, it was enough for experiment carried out. Cardiac output (CO), mean arterial pressure (MAP), heart rate (HR), systemic vascular resistance index (SVRI) and the cerebral local tissue blood oxygen saturation (TOI) were observed at 0 min, 15 min, 30 min, 60 min, 120 min after ROSC. The animals were sacrificed at 120 min after ROSC, brain tissues were harvested for study by using HE staining. Repeated measure analysis of variance was used to determine the statistical significance among the four groups at different intervals. Multi-group quantitative data was analyzed by one way ANOVA and then further by LSD test for multiple comparisons. Chi-square test or Fisher's exact probabilities was applied for multi-group binomial classification variable. Log-rank test was used for comparisons of survival curves in four groups. A two-tailed value of P<0.05 was considered statistically significant. Results There were no differences in the rate of ROSC among groups. Compared with CG and LG, ROSC time was shorter in MG (27715 vs. 19012, PO.01 ; 25216 vs. 19012, P=0.016 ) with higher 120 min survival rate ( 20% vs. 90%,∗2=9.899, P=0.005; 30% vj. 90%,∗2=7.5, P=0.02) . CO was higher in MG than that in other groups at all given intervals in the early stage of post-resuscitation(P<0.05). MAP levels were significantly higher in MG and HG compared with CG and LG at given intervals 15 min after ROSC (P相似文献   

右室流入道间隔部起搏对心脏血流动力学和心室激动顺序的影响

目的通过与右室心尖部(RVA)和右室流出道(RVOT)起搏比较,探讨右室流入道间隔部(RVIS)起搏对血流动力学和心室激动顺序的影响。方法选择24例阵发性室上性心动过速需行射频导管消融术(RFCA)且心功能正常和无室内传导阻滞的患者。在RFCA成功后,置入漂浮导管行血流动力学监测,用心室起搏电极以同一频率随机顺序起搏RVIS、RVOT和RVA,分别测定和比较各部位起搏时的心输出量(CO)、心脏指数(CI)、平均肺动脉压(mPAP)、肺毛细血管楔嵌压(PCWP)以及体表心电图上QRS波时限、JTc间期(经心率校正后的JT间期)和额面平均心电轴的变化。结果①RVIS、RVOT和RVA起搏时CO、CI、mPAP和PCWP等血流动力学指标均无差异(P>0.05)。②与正常窦性心律时QRS波时限比较,各部位起搏时QRS波时限均延长(P均<0.001),其中RVIS起搏时QRS波时限延长程度最小,RVA起搏时延长程度最大,各部位两两比较P均<0.05;JTc间期的变化有类似趋势,但各起搏部位之间比较无显著差异(P>0.05);与正常窦性心律时的额面平均心电轴比较,RVIS起搏时接近正常,RVOT起搏时电轴呈右偏趋势,RVA起搏时呈左偏趋势。结论①对心功能正常者RVIS起搏较RVOT和RVA起搏未表现出更佳的急性血流动力学效应。②RVIS起搏与RVOT和RVA起搏相比,能够保持相对正常的心室激动顺序。     

Cardiovascular and hemodynamic effect of polyethylene glycol in Rats

BACKGROUND: Polyethylene Glycol (PEG) is a solvent and used in a wide range of biomedical applications. Many fatty-acid-based molecules cannot be administered without a solvent in vivo. PEG can be used to dissolve compounds to make them water soluble. However, the effect of PEG on the cardiovascular system has not been studied. In this study, we evaluated the effect of PEG on the cardiovascular system in rat models. METHODS: Twenty male Sprague-Dawley rats weighing 250-300 g were used in this study. The control group (10 rats) were injected intraperitoneally with 0.5 ml of 5% D/W in normal saline and the second group (10 rats) with PEG 400, 2 ml/kg ip, twice a day for 1 week. After 4 weeks, the rats underwent general anesthesia and a 1.4 French ultra miniature pressure volume catheter (Millar catheter) was placed in the left ventricle via the right carotid artery to measure comprehensive hemodynamic data. The data were analyzed with PVAN pressure-volume analysis software. RESULTS: All the systolic and diastolic parameters were similar in both groups except for the effective arterial elastance (Ea), which was decreased in the PEG group. There were no significant differences in maximum (dp/dt(max)) and minimum (dp/dt(min)) development of pressure stroke work, cardiac output, ejection fraction, end systolic volume (Ves), and end diastolic volume. CONCLUSIONS: We have demonstrated that PEG, as a solvent, decreases Ea in rats in comparison to a placebo. Therefore, PEG as a solvent should be used cautiously in the cardiovascular research.     

不同部位组合起搏对充血性心力衰竭患者急性血流动力学影响的研究

观察右房左室起搏对充血性心力衰竭 (CHF)患者急性血流动力学的影响。 8例心功能II～IV级CHF患者 ,分别置入右房、右室和左室电极 (经冠状静脉窦 ) ,行不同部位组合起搏的急性血流动力学研究 ,其中 6例获得成功。使用Bitronic公司生产的双腔起搏分析仪 (ERA30 0 )分别行单纯右室心尖部 (RVA)、右房右室 (RA +RV)、右房左室 (RA +LV)、右房双室 (RA +BiV)起搏 ,同时用二维超声心动图测定上述四种起搏状况下的血流动力学参数 ,并进行比较。结果 :右房左室起搏和右房双室起搏血流动力学参数两者间无显著差异 ,但比单纯右室心尖部起搏和右房右室起搏有所改善。结论 :右房左室起搏似可使更多的CHF患者在得益于起搏治疗的同时明显降低医疗费用。     

Hemodynamic effects of somatostatin in insulin-dependent diabetic subjects

Summary The aim of the present study was to evaluate possible hemodynamic effects of somatostatin in insulin-dependent diabetic subjects. For this purpose, 7 insulin-requiring juvenile-onset diabetics were submitted to a short-term infusion of cyclic somatostatin (250 μg/h, over 2 h) or saline in randomized order. Somatostatin infusion resulted in a progressive and significant decrease in heart rate, stroke volume, cardiac index and velocity circumferential fiber; on the other hand, left ventricular ejection time was augmented by somatostatin. None of these effects was seen in the saline control study. We conclude that somatostatin exerts a negative inotropic effect in insulin-dependent diabetes.     

Hemodynamic effects of sildenafil in patients with stable ischemic heart disease

Background: Recently the new specific phosphodiesterase-5 inhibitor sildenafil was introduced into therapy for erectile dysfunction. The hemodynamic effects of sildenafil may be potentially hazardous for patients with cardiac disease. Sildenafil has been reported to augment the hypotensive effects of nitrates. There is sparse information regarding the systemic and pulmonary hemodynamic effects of a single oral dose of sildenafil in patients with stable angina. Methods: Male patients referred for coronary angiography with diagnosis of chronic stable angina were enrolled in this study to assess the acute hemodynamic effects of sildenafil. Patients receiving long-acting or sublingual nitrates for the last 6 h before the study were excluded. Hemodynamic measurement were taken during right and left heart catheterization in the basal state and 60 min after 50 mg of oral sildenafil. Results: Twelve patients (age 53±7 years) were studied. All had stable angina CCS class II or III. Four had previous myocardial infarction. By coronary angiography, seven patients had at least one coronary artery with >70% stenosis, four had at least one with 50–70% stenosis, and one had only intimal irregularities. There were no significant effects of sildenafil on systemic or pulmonary arterial pressure, left ventricle endiastolic pressure, cardiac output, and systemic or pulmonary vascular resistance (P>0.05 for all). No adverse events were observed. Conclusion: A single oral dose of sildenafil had no significant hemodynamic effect in supine patients with stable angina. Isolated administration of sildenafil does not appear to be associated to adverse cardiovascular effects.