Impact of magnetic field strength and receiver coil in ocular MRI: a phantom and patient study.

PURPOSE: Generally, high-resolution MRI of the eye is performed with small loop surface coils. The purpose of this phantom and patient study was to investigate the influence of magnetic field strength and receiver coils on image quality in ocular MRI. MATERIALS AND METHODS: The eyeball and the complex geometry of the facial bone were simulated by a skull phantom with swine eyes. MR images were acquired with two small loop surface coils with diameters of 4 cm and 7 cm and with a multi-channel head coil at 1.5 and 3 Tesla, respectively. Furthermore, MRI of the eye was performed prospectively in 20 patients at 1.5 Tesla (7 cm loop surface coil) and 3 Tesla (head coil). These images were analysed qualitatively and quantitatively and statistical significance was tested using the Wilcoxon-signed-rank test (a p-value of less than 0.05 was considered to indicate statistical significance). RESULTS: The analysis of the phantom images yielded the highest mean signal-to-noise ratio (SNR) at 3 Tesla with the use of the 4 cm loop surface coil. In the phantom experiment as well as in the patient studies the SNR was higher at 1.5 Tesla by applying the 7 cm surface coil than at 3 Tesla by applying the head coil. Concerning the delineation of anatomic structures no statistically significant differences were found. CONCLUSION: Our results show that the influence of small loop surface coils on image quality (expressed in SNR) in ocular MRI is higher than the influence of the magnetic field strength. The similar visibility of detailed anatomy leads to the conclusion that the image quality of ocular MRI at 3 Tesla remains acceptable by applying the head coil as a receiver coil.

Cardiac magnetic resonance angiography using blood-pool contrast agents: comparison of citrate-coated very small superparamagnetic iron oxide particles with gadofosveset trisodium in pigs.

PURPOSE: To compare citrate-coated very small superparamagnetic iron oxide particles (VSOP) with gadofosveset trisodium as blood pool contrast agents for cardiac magnetic resonance angiography (CMRA) in pigs. MATERIALS AND METHODS: Animal experiments were approved by the responsible authority. 10 CMRA-like examinations were performed at 1.5 T after administration of VSOP (0.06  mmol Fe/kg; 5 examinations) and gadofosveset trisodium (0.03  mmol Gd/kg; 5 examinations). The CMRA protocol included ECG-gated inversion-recovery-prepared T1-weighted gradient echo imaging (IR-GRE; one slice) and ECG-gated inversion recovery prepared steady state free precession imaging (IR SSFP; one slice) before and 1, 3, 5, 10, 15, 20, 25, 30, 40, 50, and 60  min after injection. At each time point, three different inversion times (TI; 200  msec, 300  msec, and 400  msec) were applied. Contrast-to-noise ratios (CNR) between blood and myocardium were calculated and compared using mixed linear models. RESULTS: No significant differences of CNR were found between IR-GRE and IR SSFP. At 3 and 5  min after contrast agent administration, VSOP showed a significantly higher CNR than gadofosveset trisodium when TI of 200  msec and 300 msec were applied (TI of 200  msec at 3 min: 8.2 ±â€Š0.7 vs. 5.4 ±â€Š0.7; TI of 200  msec at 5 min: 7.9 ±â€Š0.7 vs. 3.5 ±â€Š0.8; TI of 300  msec at 3  min: 11.7 ±â€Š0.7 vs. 8.8 ±â€Š0.8; TI of 300  msec at 5  min: 11.4 ±â€Š0.7 vs. 8.0 ±â€Š0.8; p < 0.05). Moreover, significant differences in favor of VSOP were found for all time points from 10 to 40  min irrespective of TI (p < 0.05). CONCLUSION: VSOP has superior blood-pool properties compared to gadofosveset trisodium resulting in prolonged improvement of CNR on CMRA.

MR spectroscopy (MRS) and magnetisation transfer imaging (MTI), lesion load and clinical scores in early relapsing remitting multiple sclerosis: a combined cross-sectional and longitudinal study.

The purpose of this study was to correlate magnetic resonance imaging (MRI)-based lesion load assessment with clinical disability in early relapsing remitting multiple sclerosis (RRMS). Seventeen untreated patients (ten women, seven men; mean age 33.0 +/- 7.9 years) with the initial diagnosis of RRMS were included for cross-sectional as well as longitudinal (24 months) clinical and MRI-based assessment in comparison with age-matched healthy controls. Conventional MR sequences, MR spectroscopy (MRS) and magnetisation transfer imaging (MTI) were performed at 1.5 T. Lesion number and volume, MRS and MTI measurements for lesions and normal appearing white matter (NAWM) were correlated to clinical scores [Expanded Disability Status Scale (EDSS), Multiple Sclerosis Functional Composite (MSFC)] for monitoring disease course after treatment initiation (interferon beta-1a). MTI and MRS detected changes [magnetisation transfer ratio (MTR), N-acetylaspartate (NAA)/creatine ratio] in NAWM over time. EDSS and lesional MTR increases correlated throughout the disease course. Average MTR of NAWM raised during the study (p < 0.05) and correlated to the MSFC score (r = 0.476, p < 0.001). At study termination, NAA/creatine ratio of NAWM correlated to the MSFC score (p < 0.05). MTI and MRS were useful for initial disease assessment in NAWM. MTI and MRS correlated with clinical scores, indicating potential for monitoring the disease course and gaining new insights into treatment-related effects.

Fabrication of a multichannel wavelength-division multiplexing-passive optical net demultiplexer with arrayed-waveguide gratings and diffractive optical elements.

A novel, to our knowledge, integrated wavelength-division multiplexing-passive optical net demultiplexer that uses an arrayed-waveguide grating and diffractive optical elements is presented. The demultiplexer is used to distribute 1.3-microm wavelength signals and to multiplex an eight-channel wavelength-division multiplexer spectrum at a 1.55-microm wavelength. The device shows high functionality and good optical performance. The measured cross talk was less than -21 dB, and the 3-dB bandwidth was determined to be 97 GHz, which is close to the theoretical value of 93 GHz. Average losses of 4.5 and 8 dB were measured for the 1.3- and the 1.55-microm signals, respectively.

Intraspecific Genomic Variation Within Xanthomonas albilineans, the Sugarcane Leaf Scald Pathogen.

ABSTRACT To better understand the nature of recent outbreaks of leaf scald disease of sugarcane in a number of sugarcane production regions of the world including Florida, Guadeloupe, Louisiana, Mauritius, Taiwan, and Texas, a study of the worldwide genetic variation of the pathogen was undertaken. A total of 218 strains from 31 geographic locations were examined. Genomic DNA of each strain was digested with the rare cutting restriction enzyme SpeI, and the fragments were separated by pulsed-field gel electrophoresis (PFGE). A total of 102 bands were identified, and 54 different DNA banding patterns (haplotypes) were observed. Eight groups of banding patterns, designated PFGE groups A through H, were consistently detected by visual, principal component, and cluster analyses. Five groups were comprised of multiple haplotypes representing numerous strains, and three were comprised of single haplotypes representing one strain each. The leaf scald outbreaks in Florida, Louisiana, Texas, and possibly Guadeloupe and Taiwan could be attributed to the introduction of strains belonging to PFGE group B. When infection by two strains each of the newly introduced strains (PFGE group B) and those previously present in Florida (PFGE group A) was analyzed in 22 sugarcane cultivars by reisolation 24 weeks after inoculation, a significantly greater mean frequency was detected for PFGE group B strains and no cultivar by PFGE group interaction was observed. Inadvertent dispersal of the pathogen among plants, possibly by means of aerosols or splashing water, was detected in a subsequent experiment. Strains of PFGE group B were recovered from the internal tissues of some plants inoculated with PFGE group A strains and were also found to be epiphytic colonizers of nonsymptomatic, noninoculated plants adjacent to the inoculated plants; whereas strains of PFGE group A were recovered only from plants that had been inoculated with them. Thus, the possibility became more apparent that strain variation might be associated, at least in part, with factors governing plant-to-plant spread of the pathogen in nature.

Developing a model for collaborative research.

Collaboration between nurses in clinical and educational settings has been advocated as a means of ensuring nursing research is both practice oriented and scientifically valid. This paper describes a model, jointly developed by colleagues from the Nursing Departments of Alfred Hospital and La Trobe University, to foster collaborative research and steer research projects generated by clinical nurses from conceptualisation to publication.