Dynamic gadolinium-enhanced echo-planar MR imaging of the liver: Effect of pulse sequence and dose on enhancement

To develop guidelines for clinical magnetic resonance imaging of the liver, the authors undertook an animal study to investigate the effect of dose and pulse sequence on liver signal intensity in gadopentetate dimeglumine—enhanced echo-planar imaging. Serial imaging of the liver was performed in anesthetized rats after intravenous administration of five different doses (0.01, 0.05, 0.1, 0.2, and 0.5 mmol/kg) of contrast agent, with six different pulse sequences. The results show that gadopentetate dimeglumine—enhanced echo-planar images obtained during the perfusion phase can yield either positive (due to increased T1 relaxation rates) or negative (due to susceptibility-induced increased T2 relaxation rates) liver enhancement depending on choice of pulse sequence and dose. At the current clinically recommended dose of 0.1 mmol/kg, maximal liver signal enhancement was seen with a T1-weighted inversion-recovery sequence, while maximal liver signal diminution was seen with a T2*-weighted gradient-echo sequence. The authors conclude that gadopentetate dimeglumine—enhanced echo-planar imaging can provide T1, T2, and T2* contrast that may be exploited for both lesion detection and lesion characterization.     

Time-resolved MR imaging by automatic data segmentation

A method for time-resolved imaging that provides a flexible trade-off between imaging time and temporal resolution is presented. It is based on a view order selection technique that automatically segments the acquired raw data into appropriate temporal frames. When used with cardiac monitoring and phase-contrast imaging, data similar to that obtained with a conventional gated phase-contrast sequence are acquired rapidly. For many applications, the temporal resolution can be reduced enough to permit imaging within a breath-hold interval, while still allowing accurate time-averaged flow quantitation. This is a general technique that can be implemented within a variety of pulse sequences and can resolve other motion cycles, including the respiratory cycle.     

Rapid diagnosis of parasitic diseases: current scenario and future needs

Background

Parasitic diseases are one of the world's most devastating and prevalent infections, causing millions of morbidities and mortalities annually. In the past, many of these infections have been linked predominantly to tropical or subtropical areas. Nowadays, however, climatic and vector ecology changes, a significant increase in international travel, armed conflicts, and migration of humans and animals have influenced the transmission of some parasitic diseases from ‘book pages’ to reality in developed countries. It has also been noted that many patients who have never travelled to endemic areas suffer from blood-borne infections caused by protozoa. In the light of existing knowledge, this new trend can be explained by the fact that in the process of migration a large number of asymptomatic carriers become a part of the blood bank donor and transplant donor populations. Accurate and rapid diagnosis represents the crucial weapon in the fight against parasitic infections.

一种快速分离纯化外周血细胞线粒体DNA方法的建立

目的探索快速分离纯化人外周血细胞线粒体DNA(mtDNA)的方法. 方法收集抗凝外周血,首先破红细胞,然后裂解白细胞,去除细胞膜和核DNA后获得mtDNA;再经过去除蛋白和RNA,获得纯mtDNA.用PCR扩增人线粒体ND1基因片段,PCR产物经纯化后测序和核苷酸同源性分析.结果用本研究中建立的方法制备的mtDNA纯度高,每毫升抗凝血可获得100ng左右的mtDNA.经过PCR扩增ND1基因433bp片段,较用细胞总DNA为模板,模板用量少,扩增产物多.测序后经核苷酸同源性分析证实扩增片段为ND1基因.结论本研究中建立的快速分离外周血细胞mtDNA的方法,可制备高纯度的mtDNA用于线粒体相关研究.     

Functional modification of agonist-antagonist electromyographic activity for rapid movement inhibition

Subjects made a fast elbow extension movement to designated target in response to a go signal. In 45% of trials a stop signal was presented after the go signal, to which subjects were asked to stop the movement as rapidly as possible. The interstimulus interval (ISI), or time interval between the go and stop signals, was randomly varied between 0 and 200 ms. Electromyographic (EMG) activity was recorded from biceps brachii and triceps brachii. Subjects could sometimes completely inhibit initiation of the movements when the ISI was 0 ms, but could rarely do so when the ISI exceeded 100 ms. For responses that were initiated but stopped on the way, the amplitude of the movement decreased linearly as the time interval (=modification time) from the stop signal to EMG onset increased. The peak velocity increased linearly as the movement amplitude increased. This tendency was similar to those previously reported in step-tracking movements with various amplitudes. In spite of the similarity in the kinematics of the movement, the EMG pattern was different from that of step-tracking movement. While the initial agonist burst (AG1) decreased linearly after the modification time exceeded 100 ms, the antagonist burst (ANT) increased compared with the go trial for the modification time from 0 to 200 ms and decreased after the modification time exceeded 300 ms. This change of activation is analogous to functional modification of middle-latency reflex EMG response to load, or cutaneous perturbation. In conclusion, it is suggested that adaptive mechanisms, which would functionally modify the reflex responses, are also continuously working during voluntary movements in response to sudden changes in environmental information. Received: 3 November 1997 / Accepted: 3 February 1998     

Diagnostic performance of arginase activity in colorectal cancer

Arginase activity was measured in serum and biopsy from healthy individuals and colorectal cancer patients. Arginase activity in tumor samples (87±7.7 U/g tissue) was significantly higher than in controls (40.7±3.3 U/g tissue). However, serum arginase activity did not show any significant change in both groups. Finally, the micromethod used to quantify arginase activity in this study is superior to other methods because it has increased sensitivity, requires less sample, and is less time-consuming. Arginase differences are significant, according to the t-test (P<0.05). Received: 14 September 2001 / Accepted: 6 February 2002     

Down syndrome and trisomy 18 in the bedouins

Direct chromosome preparations of neonatal cord blood provides the unique opportunity for rapid chromosome analysis (turnaround time; 6 hr), without the necessity of bone marrow aspiration. Based on 42 samples we confirm the finding of Garnham and Sutherland [1987] for suitability of cord blood for direct chromosome preparation. Procedural modifications are provided for higher yield of cells for chromosome analysis. The procedure may well be of major significance for rapid diagnosis of neonates who suffer from aneusomy.     

定制化胫骨平台系统的构建及应用

为解决传统人工胫骨平台假体个体匹配性差，结构强度与生物活性难统一等问题，提出了定制化复合增强型人工胫骨平台系统的设计制造方法。采用解剖学建模技术设计出外形匹配，内含三维网状构架的复合假体模型，利用快速成型技术制造出假体的树脂原型，并分别通过精密铸造和粉末烧结技术制造出钛合金胫骨平台和大段多孔陶瓷人工骨。结果显示，该方法能快速而精确地制造出形状复杂的人工胫骨平台系统，是实现假体定制化制造的有利保证；通过将金属假体和多孔陶瓷人工骨复合，解决了载重部位大段骨缺损的修复问题。临床应用表明，该假体能与对侧关节匹配运动，通过将机械重建与生物重建相结合可实现受损关节的功能重建。     

人工器官的快速成形制造

综述了一种快速成形技术在医学物理模型、可植入假体和组织工程人工器官制造中的应用，并比较了各种快速成形技术在人工器官制造中的优缺点，探讨了人工器官快速成形制造的发展方向。