On the Relationship between Dynamic Contrast-Enhanced Ultrasound Parameters and the Underlying Vascular Architecture Extracted from Acoustic Angiography

Dynamic contrast-enhanced ultrasound (DCE-US) has been proposed as a powerful tool for cancer diagnosis by estimation of perfusion and dispersion parameters reflecting angiogenic vascular changes. This work was aimed at identifying which vascular features are reflected by the estimated perfusion and dispersion parameters through comparison with acoustic angiography (AA). AA is a high-resolution technique that allows quantification of vascular morphology. Three-dimensional AA and 2-D DCE-US bolus acquisitions were used to monitor the growth of fibrosarcoma tumors in nine rats. AA-derived vascular properties were analyzed along with DCE-US perfusion and dispersion to investigate the differences between tumor and control and their evolution in time. AA-derived microvascular density and DCE-US perfusion exhibited good agreement, confirmed by their spatial distributions. No vascular feature was correlated with dispersion. Yet, dispersion provided better cancer classification than perfusion. We therefore hypothesize that dispersion characterizes vessels that are smaller than those visible with AA.     

P波时限、P波离散度对特发性心房颤动的预测价值初探

Objective:To assess the sensitivity and the specifity of predicting idiopathic AF with P wave dura-tion and P wave dispersion. Methods: The maximum P wave duration and P wave dispersion in 36 patients with idio-pathic AF were measured and compared with those of sex-and age-matched healthy subjects. Results:The maxi-mum P wave duration and P wave dispersion were higher in patients with idiopathic Af than in control group. Themaximum P wave duration >110ms or P wave dispersion >40ms was used to differentiate patients from healthy     

A Model for Transport and Dispersion in the Circulatory System Based on the Vascular Fractal Tree

Materials are distributed throughout the body of mammals by fractal networks of branching tubes. Based on the scaling laws of the fractal structure, the vascular tree is reduced to an equivalent one-dimensional, tube model. A dispersion–convection partial differential equation with constant coefficients describes the heterogeneous concentration profile of an intravascular tracer in the vascular tree. A simple model for the mammalian circulatory system is built in entirely physiological terms consisting of a ring shaped, one-dimensional tube which corresponds to the arterial, venular, and pulmonary trees, successively. The model incorporates the blood flow heterogeneity of the mammalian circulatory system. Model predictions are fitted to published concentration-time data of indocyanine green injected in humans and dogs. Close agreement was found with parameter values within the expected physiological range. © 2003 Biomedical Engineering Society. PAC2003: 8710+e, 8719Hh, 8719Uv     

急性心肌梗死早期QT间期JT间期离散度与近期严重心律失常的关系

目的 :探讨AMI早期QT间期离散度、JT间期离散度与严重心律失常的关系。方法 :测定 46例AMI患者心梗发生后第 3d的QT间期离散度 (QTd)和JT间期离度 (JTd)。并与30例正常人的对照组比较。结果 :AMI组QTd、JTd、QTcd较对照组显著增大 (P <0 0 1 )。住院期间严重室性心律失常发生组 (1 8例 )的QTd、JTd、QTcd较无严重室性心律失常组 (2 8例 )明显增大 (P <0 0 1 ) ,且发生室颤的 9例患者QTd、JTd、QTcd比无室颤的明显增大 (P <0 0 1 )。结论 :早期测定AMI患者QTd、JTd、QTcd对患者近期严重室性心律失常的发生有预测意义     

利巴韦林分散片的制备及稳定性评价

目的研究利巴韦林分散片的处方和制备工艺。方法对按笔者自我设计配方制备的4种利巴韦林分散片,采用高效液相色谱法测定溶出度及进行稳定性评价。结果以处方3工艺制成的片剂,质量可控,稳定性较好。结论处方3工艺成熟,质量稳定,是一种易于服用、奏效快的新制剂。     

Amphiphilic amino acid copolymers as stabilizers for the preparation of nanocrystal dispersion

The recent advance of particle size engineering in nanometer ranges has widened the formulation opportunities of relatively water-insoluble drugs. However, the ‘nanoformulation’ suffers from a lack of systematic understanding about the requirements of polymeric stabilizers. Furthermore, the polymers that can be used for the preparation of nanocrystals are so limited that finding a proper stabilizer for a given formulation is often difficult. In this study, amino acid copolymers whose properties can systematically be tailored are developed, and their morphological and compositional effects are investigated. Copolymers containing lysine (K) as their hydrophilic segments, and phenylalanine (F) or leucine (L) as their hydrophobic segments successfully produce stable nanocrystals (200–300 nm) in water, while copolymers of K and alanine (A) could not generate nanosized particles. Not the morphology but the hydrophobicity of copolymers seems to be a critical parameter in the preparation of drug nanocrystals by wet comminution. The effective stabilization performance of copolymers requires the hydrophobic moiety content to be higher than 15 mol%. Comminution for only 5 min is long enough for nanocrystal preparation, and the crystallinity of drug is found intact after the processing.     

Impact of Acoustic Radiation Force Excitation Geometry on Shear Wave Dispersion and Attenuation Estimates

Shear wave elasticity imaging (SWEI) characterizes the mechanical properties of human tissues to differentiate healthy from diseased tissue. Commercial scanners tend to reconstruct shear wave speeds for a region of interest using time-of-flight methods reporting a single shear wave speed (or elastic modulus) to the end user under the assumptions that tissue is elastic and shear wave speeds are not dependent on the frequency content of the shear waves. Human tissues, however, are known to be viscoelastic, resulting in dispersion and attenuation. Shear wave spectroscopy and spectral methods have been previously reported in the literature to quantify shear wave dispersion and attenuation, commonly making an assumption that the acoustic radiation force excitation acts as a cylindrical source with a known geometric shear wave amplitude decay. This work quantifies the bias in shear dispersion and attenuation estimates associated with making this cylindrical wave assumption when applied to shear wave sources with finite depth extents, as commonly occurs with realistic focal geometries, in elastic and viscoelastic media. Bias is quantified using analytically derived shear wave data and shear wave data generated using finite-element method models. Shear wave dispersion and attenuation bias (up to 15% for dispersion and 41% for attenuation) is greater for more tightly focused acoustic radiation force sources with smaller depths of field relative to their lateral extent (height-to-width ratios <16). Dispersion and attenuation errors associated with assuming a cylindrical geometric shear wave decay in SWEI can be appreciable and should be considered when analyzing the viscoelastic properties of tissues with acoustic radiation force source distributions with limited depths of field.     

P波离散度预测扩张型心肌病伴阵发性心房颤动的临床价值

目的探讨P波离散度(Pd)预测扩张型心肌病(DCM)伴阵发性心房颤动(PAF)的价值。方法30例DCM伴阵发性Af者(A组),26例DCM无Af者(B组)。通过12导联体表心电图测定P波最大持续时间(Pmax)与最小持续时间(Pmin),计算Pd(Pd=Pmax-Pmin)。比较A组与B组的Pd与Pmax。结果A组Pd为48.44-13.8ms,Pmax为122.84-13.7ms,Pmin为76.2±12.0ms,与B组Pd30.6±10.2ms,Pmaxll0.2±10.4ms,Pmin80.8+11.5ms相比明显延长(p<0.01)。A组左房(LA)内径41.415.6mm,B组LA内径40.24-6.2mm,两组相比无显著差异(p>0.05)。为预测Af,取P波时限≥120ms,Pd≥40ms以及两者相结合,敏感性分别为86%、90%、73%,特异性分别为80%、85%、89%,阳性预测值分别为84%、87%、88%。结论Pd增加和P波宽度延长,可预测DCM并发阵发性Af的危险性。     

Reinforcement of denture base resin with short vegetable fiber

Objectives

Short ramie fibers were selected to investigate the effect of fiber length and volume fraction on the flexural properties of ramie fiber reinforced denture base PMMA. With the aid of measured interfacial shear strength and theoretical prediction values, experimental results were well interpreted.

Methods

Interfacial properties between denture base PMMA and ramie fibers were evaluated by single fiber pull-out test. Then, chopped ramie fibers were pre-stirred with PMMA powder by a mechanical blender and then mixed with MMA liquid to fabricate composites. Two crucial influencing factors, fiber volume fraction and fiber length, were studied to clarify their effects on flexural properties of composites.

Results

With 1.5 mm fibers addition, flexural modulus of denture base PMMA rose from 2.50 to 3.46 GPa with 10 vol.% fibers, while flexural strength declined steadily with increment of fiber content. If fiber length was 3.0 mm, the modulus showed a growth to 3.5 GPa at 4 vol.% fiber content followed by a drop to 3.00 GPa at 10 vol.%, whereas fluctuation in strength was experienced. Experimental results were discussed by comparison with two theoretical models.

Significance

Short ramie fiber reinforced denture base PMMA had higher flexural modulus than neat resin, while strength was lowered due to the weak interfacial adhesion. The potential of vegetable fibers as reinforcing agents for denture base should be further investigated by strengthening the interface between cellulose and denture base PMMA.     

Active and uncontrolled asthma among children exposed to air stack emissions of sulphur dioxide from petroleum refineries in Montreal,Quebec: A cross-sectional study

BACKGROUND:

Little attention has been devoted to the effects on children’s respiratory health of exposure to sulphur dioxide (SO₂) in ambient air from local industrial emissions. Most studies on the effects of SO₂ have assessed its impact as part of the regional ambient air pollutant mix.

OBJECTIVE:

To examine the association between exposure to stack emissions of SO₂ from petroleum refineries located in Montreal’s (Quebec) east-end industrial complex and the prevalence of active asthma and poor asthma control among children living nearby.

METHODS:

The present cross-sectional study used data from a respiratory health survey of Montreal children six months to 12 years of age conducted in 2006. Of 7964 eligible households that completed the survey, 842 children between six months and 12 years of age lived in an area impacted by refinery emissions. Ambient SO₂ exposure levels were estimated using dispersion modelling. Log-binomial regression models were used to estimate crude and adjusted prevalence ratios (PRs) and 95% CIs for the association between yearly school and residential SO₂ exposure estimates and asthma outcomes. Adjustments were made for child’s age, sex, parental history of atopy and tobacco smoke exposure at home.

RESULTS:

The adjusted PR for the association between active asthma and SO₂ levels was 1.14 (95% CI 0.94 to 1.39) per interquartile range increase in modelled annual SO₂. The effect on poor asthma control was greater (PR=1.39 per interquartile range increase in modelled SO₂ [95% CI 1.00 to 1.94]).

CONCLUSIONS:

Results of the present study suggest a relationship between exposure to refinery stack emissions of SO₂ and the prevalence of active and poor asthma control in children who live and attend school in proximity to refineries.