肝细胞癌CT灌注参数与VEGF表达的相关性研究

目的: 探讨肝细胞癌(HCC)CT灌注参数与血管内皮生长因子(VEGF)表达的相关性,以期获得在活体评价肿瘤血管生成状况的途径.材料和方法: 经手术病理证实的肝细胞癌组24例,对照组15例.患者均依次行常规全肝平扫、CT灌注扫描及常规全肝增强扫描.用免疫组化SP法检测HCC中VEGF的表达.结果: 肝癌组肝动脉灌注量(HAP)明显升高,门静脉灌注量(HPP)显著降低,肝癌组比对照组肝动脉灌注指数(HAI)明显升高而门静脉灌注指数(PPI)显著下降;不同VEGF表达组的HCC灌注参数不同,HAP值与VEGF表达存在正相关.结论: 肝细胞癌CT灌注参数HAP与VEGF表达存在正相关,灌注参数在一定程度上反映活体的肿瘤血管生成状况和恶性程度,有助于临床制定治疗方案,判断疗效及预后.     

99Tcm-MIBI心肌灌注显像诊断病毒性心肌炎的价值

目的探讨心肌灌注断层显像方法在病毒性心肌炎影像中半定量分析应用的诊断价值.方法采用99Tcm-MIBI心肌灌注断层显像,分析2003-01～2005-03的108例心肌炎患者显像结果,并以36例无心肌炎患者为对照,按心肌放射性分布密集均匀程度分为3度,观察患者心肌/肝计数比值(myocardium/liverM/L)及心腔/心肌计数比值(chambers heart/myocardium C/M)在早期和/或症状较轻之心肌炎患者临床诊断中的价值.结果虽然早期和/或症状较轻之心肌炎患者可能无花斑样改变,但心肌摄取显像剂的放射性计数通常降低,表现为M/L降低或/和C/M增高.对照组的M/L和C/M分别为1.21±0.38及0.26±0.17.108例Ⅰ、Ⅱ、Ⅲ度心肌炎患者M/L分别为1.14±0.32、1.12±0.33及1.08±0.22,与对照组比较明显降低(P＜0.01和/或P＜0.05);C/M分别为0.28±0.25、0.30±0.24及0.33±0.19,与对照组比较明显增高(P＜0.01和/或P＜0.05).结论 M/L降低和C/M比增高,对于早期及症状较轻的病毒性心肌炎患者之诊断有一定价值.     

Modeling and optimization of Look-Locker spin labeling for measuring perfusion and transit time changes in activation studies taking into account arterial blood volume.

This work describes a new compartmental model with step-wise temporal analysis for a Look-Locker (LL)-flow-sensitive alternating inversion-recovery (FAIR) sequence, which combines the FAIR arterial spin labeling (ASL) scheme with a LL echo planar imaging (EPI) measurement, using a multireadout EPI sequence for simultaneous perfusion and T*(2) measurements. The new model highlights the importance of accounting for the transit time of blood through the arteriolar compartment, delta, in the quantification of perfusion. The signal expected is calculated in a step-wise manner to avoid discontinuities between different compartments. The optimal LL-FAIR pulse sequence timings for the measurement of perfusion with high signal-to-noise ratio (SNR), and high temporal resolution at 1.5, 3, and 7T are presented. LL-FAIR is shown to provide better SNR per unit time compared to standard FAIR. The sequence has been used experimentally for simultaneous monitoring of perfusion, transit time, and T*(2) changes in response to a visual stimulus in four subjects. It was found that perfusion increased by 83 +/- 4% on brain activation from a resting state value of 94 +/- 13 ml/100 g/min, while T*(2) increased by 3.5 +/- 0.5%.     

Optimal design of pulsed arterial spin labeling MRI experiments.

Quantitative measurement of cerebral blood flow (CBF) using arterial spin labeling (ASL) MRI requires the acquisition of multiple inversion times (TIs) and the application of an appropriate kinetic model. The choice of these sampling times will have an impact on the precision of the estimated parameters. Here, optimal sampling schedule (OSS) design techniques, based on the Fisher Information approach, are applied in order to derive an optimal sampling scheme for pulsed arterial spin labeling (PASL) experiments. Such an approach should improve the precision of parameter estimation from experimental data, and provide a formal framework for optimally selecting a limited number of samples. In this study, we aimed to optimize the estimation precision of CBF and bolus arrival time from the PASL data. The performance of OSS was compared to a more standard evenly distributed sampling schedule (EDS) using both simulated and measured experimental data sets. It was found that OSS was able to significantly improve the precision of parameter estimation in PASL studies that sought to estimate either both CBF and bolus arrival time, or CBF alone.     

Increased prognostic value of combined myocardial perfusion imaging and exercise electrocardiography in patients with coronary artery disease

BACKGROUND: Myocardial perfusion imaging (MPI) with technetium-99m-labeled sestamibi and exercise electrocardiography (EECG) are widely used for risk stratification of patients with known or suspected coronary artery disease (CAD). However, no large-scale studies have addressed the prognostic power of the combined information from these diagnostic tools. METHODS AND RESULTS: We studied 697 consecutive patients who underwent a 2-day Tc-99m sestamibi cardiac perfusion imaging protocol. The EECG was performed on a bicycle ergometer by symptom-limited exercise. Causes of death were obtained from death certificates. Univariate survival analyses were performed with a Kaplan-Meier estimate and a corresponding log-rank test. A multivariate Cox proportional hazards model was applied to test for potential predictor covariates obtained from hospital records. The predominant risk factors of cardiac death were fixed perfusion defects (relative risk, 2.55; range, 1.43 to 4.55) and an impaired circulatory exercise response (relative risk, 3.26; range, 1.74 to 6.08). The major prognostic information of MPI was the ability to detect patients with a definitively low risk. Patients with impaired circulatory response to exercise test and fixed perfusion defects were at a very high risk. CONCLUSION: The combined results of MPI and EECG provide substantial information on the long-term risk of cardiac death in patients with suspected CAD.     

Pitfalls in MR measurement of tissue blood flow with intravascular tracers: Which mean transit time?

Measuring tissue blood flow with NMR imaging of intravascular tracers is more difficult than measurements of tissue blood volume. One major obstacle to the application of the Central Volume Principle is the direct measurement of the mean transit time. In this note, we demonstrate that mean transit time (MTT), which relates tissue blood volume to blood flow via the Central Volume Principle, is not the first moment of the concentration-time curve for MR or CT imaging of purely intravascular tracers. However, while first moment methods cannot be used by themselves to determine absolute flow, we show that transit curves may provide a useful relative measure of flow, for example, by considering ratios of the first moments.     

Relation of myocardial perfusion at rest and during pharmacologic stress to the PET patterns of tissue viability in patients with severe left ventricular dysfunction

Background. Stress perfusion imaging can assess effectively the amount of jeopardized myocardium, but its use for identifying underperfused but viable myocardium has yielded variable results. We evaluated the relation between measurements of myocardial perfusion at rest and during pharmacologic stress and the patterns of tissue viability as determined by positron emission tomographic (PET) imaging.Methods and Results. We studied 33 patients with coronary artery disease and left ventricular (LV) dysfunction (LV ejection fraction, 30% ± 8%). PET imaging was used to evaluate regional myocardial perfusion at rest and during pharmacologic stress with [¹³N]-ammonia as a flow tracer, and to delineate patterns of tissue viability (ie, perfusion-metabolism mismatch or match) using [¹⁸F]-deoxyglucose (FDG). We analyzed 429 myocardial regions, of which 229 were dysfunctional at rest. Of these, 30 had normal perfusion and 199 were hypoperfused. A severe resting defect (deficit>40% below normal) predicted lack of significant tissue viability; 31 of 35 regions (89%) had a PET match pattern denoting transmural fibrosis. Although regions with mild or moderate resting defects (deficit <40% below normal) showed evidence of metabolic activity, perfusion measurements alone failed to identify regions with PET mismatch (reflecting hibernating myocardium). Reversible stress defects were observed with slightly higher frequency in regions with a PET mismatch (10 of 37) than in those with a PET match (36 of 162) pattern of viability. A reversible stress defect was a specific (78%) marker, but was a relatively insensitive marker (27%) of viable myocardium as defined by the PET mismatch pattern.Conclusions. In patients with LV dysfunction, the severity of regional contractile abnormalities correlates with the severity of flow deficit at rest. Severe reductions in resting blood flow in these dysfunctional regions identify predominantly nonviable myocardium that is unlikely to have improved function after revascularization. Although dysfunctional myocardium with mild to moderate flow reductions contains variable amounts of viable tissue (as assessed by FDG uptake), flow measurements alone do not distinguish between regions with PET mismatch (potentially reversible dysfunction) and PET match (irreversible dysfunction). The presence of an irreversible defect on stress imaging is a relatively specific (78%) marker of PET match, whereas a reversible stress defect is a rather insensitive (27%) marker of viability, as defined by the PET mismatch pattern.     

Electrophysiological and neurochemical study of the rat geniculo‐cortical pathway. Evidence for glutamatergic neurotransmission

The projection from the dorsal lateral geniculate nucleus to the primary visual cortex of the rat was studied electrophysiologically. Electrical stimulation of the dorsal lateral geniculate nucleus and the optic tract produced three types of responses on neurons of area 17: excitation followed by inhibition, excitation and inhibition. These results extend and confirm, in adult rats, previous studies done in rat geniculate-visual cortex cocultures preparations in vitro. The role of glutamate in the neurotransmission of the rat geniculo-cortical pathway was also investigated. In a first set of experiments, the effects of kynurenate, an antagonist of glutamate receptors, on visual cortex neurons with a monosynaptic excitatory response to dorsal lateral geniculate nucleus stimulation were studied. Microiontophoresis of kynurenate in area 17 neurons selectively suppressed the excitatory response to dorsal lateral geniculate nucleus and optic tract stimulation. In a second set of experiments, the effects of electrical stimulation of the dorsal lateral geniculate nucleus and the optic tract on the release of amino acids in the rat visual cortex in vivo were studied. Using the push–pull method, we perfused a discrete region of the visual cortex with artificial cerebrospinal fluid (CSF), and the amino acid content of the perfusates was analysed by high performance liquid chromatography (HPLC). Stimulation of either the dorsal lateral geniculate nucleus or the optic tract significantly increased glutamate release in area 17. The rest of the amino acids studied did not show significant changes. The results provide evidence for the participation of glutamate in the neurotransmission of the geniculo-cortical pathway in the rat.     

Tissue perfusion in relation to cardiac output during continuous positive-pressure ventilation and administration of propranolol or verapamil

Background : Our objective was to determine whether administration of propranolol or verapamil modifies the hemodynamic adaptation to continuous positive-pressure ventilation (CPPV), in particular the regional distribution of cardiac output (CO).
Methods : General hemodynamics and regional blood flows assessed by microsphere technique (15 (μm) were recorded in 16 anesthetized pigs during spontaneous breathing (SB) and CPPV with 8 cm H₂O end-expiratory pressure (CPPV8) before and after intravenous administration of propranolol (0.3 mg · kg⁻¹ followed by 0.15 mg · kg⁻¹ · h⁻¹, n=8) or verapamil (0.1 mg · kg⁻¹ followed by 0.3 mg · kg⁻¹ · h⁻¹, n=8).
Results : CPPV8 depressed CO by 25% without shifts in its relative distribution with the exception of a noteworthy increase in adrenal perfusion. Propranolol increased arterial blood pressure, and due to a fall in heart rate, CO dropped by 25%. The kidneys and, to a lesser extent, the splanchic region and central nervous system received increased fractions of the remaining CO at the expense of skeletal muscle flow. Similar patterns were seen during SB and CPPV8 such that the combination of propranolol and CPPV8 depressed CO by 50%. The circulatory effects of verapamil were less evident but myocardial perfusion tended to increase.
Conclusions : The combination of propranolol or verapamil with CPPV does not result in any specific hemodynamic interaction in anesthetized pigs, except that the combined effect of propranolol and CPPV may severely reduce CO.     

Correlation of an exercise-induced increase in systemic circulation with neural retinal function in humans

Although the effects of physical exertion on intraocular pressure and systemic blood pressure are well established, the retinal response to such physiologic stress has not been examined. We studied the effect of short-term intense exercise on the principal waves in the scotopic and photopic flash electroretinograms, as well as the lower-amplitude oscillatory potentials. Sixteen healthy volunteers between 20 and 30 years of age participated in this experiment. The electroretinograms and oscillatory potentials were recorded with a Nicolet CA-1000 clinical averager, using DTL-type fiber electrodes. All retinal potentials were taken immediately before and after a minimum 20-min period of stationary bicycling that increased the heart rate to about 140 beats per minute. The electroretinograms were recorded from eyes with dilated pupils, 10 min after white-light adaptation of the right eye, and 30 min after dark adaptation of the left eye. Red flashes and dim white flashes were used to elicit photopic and scotopic electroretinograms, respectively. While no changes were recorded for any of the electroretinogram components recorded under photopic conditions, the amplitude of OP5 was decreased and the implicit time of OP4 was delayed after exercise for scotopic conditions. We concluded that exercise caused component-specific changes in the scotopic oscillatory potentials. Since it is well known that oscillatory potentials are vulnerable to ischemia, scotopic oscillatory potentials may be used as simple noninvasive indices of the reactivity of the retinal vascular autoregulatory system during exercise.