Evaluation of renal function by dynamic MR imaging: effect of water load.

The aim of this study was to investigate the usefulness of magnetic resonance (MR) imaging in the evaluation of renal function, with particular attention to the effects of water load. Ten healthy volunteers underwent dynamic MR imaging after an injection of gadolinium diethylene-triaminepenta-acetic acid (Gd-DTPA) as a contrast agent to evaluate renal function by the following four methods: the positive method [longitudinal relaxation time (T1) shortening is the dominant effect], the negative method [transverse relaxation time (T2) shortening is the dominant effect] and two intermediate methods by switching the Gd-DTPA concentrations used in the positive and negative methods. A prolonged cortical peak time and a reduced medullary peak level were observed by the positive method under a dehydrated condition, suggesting that these variables were slightly influenced by Gd-DTPA concentrated in the medulla. By the negative method, low signals due to T2* (T2* is the effective transverse relaxation time, typically shorter than T2) shortening appeared in the medulla under normal conditions, but these signals were unclear when the subject was under an overhydrated condition. These results indicate that water metabolism, in addition to imaging parameters and Gd-DTPA dose levels, should be considered when renal function is evaluated by dynamic MR imaging. Analysis of both the pattern of MR images and the time-signal intensity curves may be useful in the evaluation of renal function. The results also indicate that the positive method is preferred when the patient is overhydrated as it allows the evaluation of the local renal kinetic function by recording changes in the regional contrast agent levels.</p

Differential diagnosis of adrenal masses by chemical shift and dynamic gadolinium enhanced MR imaging.

Chemical shift MRI is widely used for identifying adenomas, but it is not a perfect method. We determined whether combined dynamic MRI methods can lead to improved diagnostic accuracy. Fifty-seven adrenal masses were examined by chemical shift and dynamic MR imaging using 2 MR systems. The masses included 38 adenomas and 19 non-adenomas. In chemical shift MRI studies, the signal intensity index (SI) was calculated, and the lesions classified into 5 types in the dynamic MRI studies. Of the 38 adenomas studied, 37 had an SI greater than 0. In the dynamic MRI, 34 of 38 adenomas showed a benign pattern (type 1). If the SI for the adenomas in the chemical shift MRI was considered to be greater than 0, the positive predictive value was 0.9, and the negative predictive value was 0.94 and kappa = 0.79. If type 1 was considered to indicate adenomas in the dynamic MRI, the corresponding values were 0.94, 0.81 and kappa = 0.77 respectively. The results obtained when the 2 methods were combined were 1, 0.95 and kappa = 0.96 respectively. The chemical shift MRI was found to be useful for identifying adenomas in most cases. If the adrenal mass had a low SI (0 &#60; SI &#60; 5), dynamic MRI was also found to be helpful for making a differential diagnosis.</p

Zone-Based Energy Aware Data Collection Protocol for WSNs

In this paper we propose the Zone-based Energy Aware data coLlection (ZEAL) protocol. ZEAL is designed to be used in agricultural applications for wireless sensor networks. In these type of applications, all data is often routed to a single point (named “sink” in sensor networks). The overuse of the same routes quickly depletes the energy of the nodes closer to the sink. In order to minimize this problem, ZEAL automatically creates zones (groups of nodes) independent from each other based on the trajectory of one or more mobile sinks. In this approach the sinks collects data queued in sub-sinks in each zone. Unlike existing protocols, ZEAL accomplish its routing tasks without using GPS modules for location awareness or synchronization mechanisms. Additionally, ZEAL provides an energy saving mechanism on the network layer that puts zones to sleep when there are no mobile sinks nearby. To evaluate ZEAL, it is compared with the Maximum Amount Shortest Path (MASP) protocol. Our simulations using the ns-3 network simulator show that ZEAL is able to collect a larger number of packets with significantly less energy in the same amount of time

Experimental study of fast and ultrafast T2-weighted imaging sequences using AMI-25 superparamagnetic iron oxide (SPIO).

The objective of this study was to evaluate fast and ultrafast T2-weighted images (T2WI), including echo planar imaging (EPI), using an AMI-25 agar phantom. Image quality for conventional spin echo (CSE) and turbo spin echo (TSE) was almost equivalent. In high-resolution TSE, image quality was highest due to the use of a 512 x 256 matrix. Half-Fourier single-shot turbo SE (HASTE) was associated with blurring of images, and turbo-gradient SE (TGSE) showed a deterioration of image quality. EPI also suffered from poor image quality because this method is very sensitive to magnetic field inhomogeneity. CSE showed good signal-to-noise ratio (S/N) and contrast ratio (CR), but also required the longest imaging times. Among the TSE sequences, TSE with a short echo train length (ETL) was superior in terms of S/N. The CR of EPI and fast low angle shot (FLASH) images were improved in proportion to the effective echo time (TE). At present, TSE is inferior to CSE in terms of S/N and CR. However, taking into consideration scanning time, TSE with a short ETL is thought to be suitable for routine examinations. Effective TE is an important factor in gradient echo (GRE) examinations.&#60;/P&#62;</p

MR imaging of renal cell carcinoma: associations among signal intensity, tumor enhancement, and pathologic findings.

The purpose of this study was to compare the MR characteristics of renal cell carcinomas against histologic findings and to assess the correlations among signal intensity, tumor enhancement, and pathologic findings. Fifty-four patients (56 lesions) were examined by MR imaging and then underwent partial or radical nephrectomy. The pathologic diagnosis of all lesions was renal cell carcinoma. All MR examinations were performed as dynamic studies using the same 1.5-T scanner. MR characteristics were compared against pathologic findings after resection, and the correlations among signal intensity, tumor enhancement, and pathologic findings were then assessed. A significant correlation was observed between tumor grade and tumor enhancement, with G3 lesions tending to show little enhancement. Regardless of the histologic classification, G3 tumors were found to contain highly heterotypic cancer cells and very few vessels by histopathologic examination. No significant correlations were noted between the other MR characteristics and pathologic findings. Renal cell carcinomas showing little enhancement tend to be highly malignant lesions based on the pathologic findings. Special consideration is required for these tumors with regard to the selection of surgical intervention and follow-up observation.</p

2D-Time of Flight MR Angiography in Intrathoracic Masses

正常ボランティア5例, 胸部腫瘤性病変の患者15例に対してMR Angiographyを施行した.MRAは, 6秒の息、止めでFLASH法(TR=20msec, TE=8msec, Flip angle=30°)を用いて撮像した像から作成した.全ての症例で胸部大動脈, 上大静脈, 下大静脈, 肺動脈及び肺静脈根部など太い血管の明瞭なMRA像が得られ, 腫瘤とそれら大血管系との関係が把握しやすく胸部腫瘤性病変の評価に有用と考えられた.MR Angiography of the thorax was performed in 5 healthy volunteers and 15 patients with intrathoracic masses. 2D-MRA was obtained sequentially by means of a fast low angle shot(FLASH)technique(TR=20msec.TE=8msec, Flip angle=30within a 6-second period of breath holding. MRA for great vessels was successfully completed in all volunteers and all patients. The relation between tumor and vasculature can be visualized so definitely that MRA may be thought to be a promising complement to MR imaging in the evaluation of intrathoracic masses

Functional mutations in spike glycoprotein of Zaire ebolavirus associated with an increase in infection efficiency

Ebola virus (EBOV) is extremely virulent, and its glycoprotein is necessary for viral entry. EBOV may adapt to its new host humans during outbreaks by acquiring mutations especially in glycoprotein, which allows EBOV to spread more efficiently. To identify these evolutionary selected mutations and examine their effects on viral infectivity, we used experimental–phylogenetic–structural interdisciplinary approaches. In evolutionary analysis of all available Zaire ebolavirus glycoprotein sequences, we detected two codon sites under positive selection, which are located near/within the region critical for the host‐viral membrane fusion, namely alanine‐to‐valine and threonine‐to‐isoleucine mutations at 82 (A82V) and 544 (T544I), respectively. The fine‐scale transmission dynamics of EBOV Makona variants that caused the 2014–2015 outbreak showed that A82V mutant was fixed in the population, whereas T544I was not. Furthermore, pseudotype assays for the Makona glycoprotein showed that the A82V mutation caused a small increase in viral infectivity compared with the T544I mutation. These findings suggest that mutation fixation in EBOV glycoprotein may be associated with their increased infectivity levels; the mutant with a moderate increase in infectivity will fix. Our findings showed that a driving force for Ebola virus evolution via glycoprotein may be a balance between costs and benefits of its virulence