Fast CPMG-based Bloch-Siegert B(1)+ mapping.

A novel method for B(1)+ mapping based on the Bloch-Siegert (BS) shift was recently presented. This method applies off-resonant pulses before signal acquisition to encode B(1) information into the signal phase. BS-based methods possess significant advantages in measurement time and accuracy compared to magnitude-based B(1)+ methods. This study extends the idea of BS B(1)+ mapping to Carr, Purcell, Meiboom, Gill (CPMG)-based multi-spin-echo (BS-CPMG-MSE) and turbo-spin-echo (BS-CPMG-TSE) imaging. Compared to BS-based spin echo imaging (BS-SE), faster acquisition of the B(1)+ information was possible using the BS-CPMG-TSE sequence. Furthermore, signal loss by T(2)* effects could be minimized using these spin echo-based techniques. These effects are critical for gradient echo-based BS methods at high field strengths. However, multi-spin-echo-based BS B(1) methods inherently possess high specific absorption rates. Thus, the relative specific absorption rate of BS-CPMG-TSE sequences was estimated and compared with the specific absorption rate produced by BS-SE sequences.

Improved encoding strategy for CPMG-based Bloch-Siegert B(1)(+) mapping.

Bloch-Siegert (BS) based B(1)(+) mapping methods use off-resonant pulses to encode quantitative B(1)(+) information into the signal phase. It was recently shown that the principle behind BS-based B(1)(+) mapping can be expanded from spin echo (BS-SE) and gradient-echo (BS-FLASH) based BS B(1)(+) mapping to methods such as Carr, Purcell, Meiboom, Gill (CPMG)-based turbo-spin echo (BS-CPMG-TSE) and multi-spin echo (BS-CPMG-MSE) imaging. If CPMG conditions are preserved, BS-CPMG-TSE allows fast acquisition of the B(1)(+) information and BS-CPMG-MSE enables simultaneous mapping of B(1)(+), M(0), and T(2). To date, however, two separate MRI experiments must be performed to enable the calculation of B(1)(+) maps. This study investigated a modified encoding strategy for CPMG BS-based methods to overcome this limitation. By applying a "bipolar" off-resonant BS pulse before the refocusing pulse train, the needed phase information was able to be encoded into different echo images of one echo train. Thus, this technique allowed simultaneous B(1)(+) and T(2) mapping in a single BS-CPMG-MSE experiment. To allow single-shot B(1)(+) mapping, this method was also applied to turbo-spin echo imaging. Furthermore, the presented modification intrinsically minimizes phase-based image artifacts in BS-CPMG-TSE experiments.

Application of compressed sensing to in vivo 3D ¹9F CSI.

This study shows how applying compressed sensing (CS) to (19)F chemical shift imaging (CSI) makes highly accurate and reproducible reconstructions from undersampled datasets possible. The missing background signal in (19)F CSI provides the required sparsity needed for application of CS. Simulations were performed to test the influence of different CS-related parameters on reconstruction quality. To test the proposed method on a realistic signal distribution, the simulation results were validated by ex vivo experiments. Additionally, undersampled in vivo 3D CSI mouse datasets were successfully reconstructed using CS. The study results suggest that CS can be used to accurately and reproducibly reconstruct undersampled (19)F spectroscopic datasets. Thus, the scanning time of in vivo(19)F CSI experiments can be significantly reduced while preserving the ability to distinguish between different (19)F markers. The gain in scan time provides high flexibility in adjusting measurement parameters. These features make this technique a useful tool for multiple biological and medical applications.

[Ventilation hazard caused by a soft ventilation bag]. / Materialbedingte Gefährdung der Beatmung durch weichen Beatmungsbeutel.

The introduction of a new ventilation bag was associated with the occurrence of an unexpected ventilation problem. The analysis revealed a technical problem related to the high plasticity of the new bag allowing incomplete obstruction due to torsion of the anesthesia bag.

[Can the addition of clonidine improve the analgesic efficacy of low dose intrathecal morphine? A randomised double-blind trial]. / Verbessert der Zusatz von Clonidin zur Spinalanästhesie die analgetische Wirkung niedrig dosierten intrathekalen Morphins? Eine randomisierte doppelblinde Studie.

OBJECTIVE: To evaluate the influence of intrathecal clonidine on spinal morphine analgesia and adverse effects after major orthopaedic surgery. METHODS: The study was approved by the local Ethics Committee.After written informed consent, 45 ASA I-III patients scheduled for hip or knee replacement were included. Patients were randomly allocated to receive either placebo, 0.1 mg morphine or 0.1 mg morphine+50 microg clonidine in addition to 15 mg bupivacaine intrathecally. The primary outcome parameter was the time to first opioid request. Statistical differences were calculated with U-test or Fisher's exact test. RESULTS: Clonidine did not result in a significant improvement of postoperative analgesia. The mean time until first opioid request was for placebo 10.3+/-7.9 h, for 0.1 mg morphine 23.0+/-3.9 h and for 0.1 mg morphine+ 50 microg clonidine 21+/-6.9 h, respectively. Clonidine significantly increased the rate of adverse effects. CONCLUSION: Our trial did not confirm an improved analgesia with the combination of intrathecal morphine and clonidine. Due to increased adverse effects the combination of intrathecal clonidine and morphine does not seem to be a reasonable alternative in the management of postoperative pain after orthopaedic surgery.

Glycopeptide-albumin derivative: it preparation and histochemical ligand properties.

Carrier-immobilized mono- or disaccharides and other carbohydrate structures, derived by custom-made chemical synthesis, have already proven to be valuable ligands for localizing carbohydrate-binding proteins in tissue sections. Defined purified glycopeptides, as components of neoglycoproteins, offer the possibility of increasing their structural complexity and, thereby, their receptor selectivity. To test the feasibility of this approach, the glycopeptide man6-glcNAc2-asparagine derived from ovalbumin was purified after pronase digestion. It was coupled to bovine serum albumin as carrier protein with the homobifunctional linking agent bis-(sulphosuccinimidyl)suberate to yield the diglycosylated concanavalin A-reactive product. Following biotinylation, it was used to detect mannose-specific binding sites in fixed cells of seven human leukemia or lymphoma lines and in fixed, paraffin-embedded sections of human breast cancer. In comparison to chemically mannosylated bovine serum albumin with ten sites of glycosylation or to ovalbumin, this derivative produced a similar pattern of reaction with a quantitatively lower extent of staining in most cases. Remarkably, the presence of potential endogenous ligands for the detected receptor sites was ascertained using the plant lectin concanavalin A. Thus, the conjugation of a purified, deliberately selected glycopeptide to a suitable carrier produces a histochemical tool for detecting glycopeptide-specific binding sites.

A proton magnetic resonance investigation of the glycosyl torsion angle of uracil nucleosides and nucleotides.

The use of line-shape decomposition techniques permitted the small 5-bond (5-J51') and 4-bond (4-J61') proton-proton coupling constants of a series of uracil nucleosides and nucleotides to be determined accurately. From an analysis of these coupling constants we have determined that the uracil base is in a predominantly anti conformation in aqueous solution and the mean position is not substantially altered by phosphate substitution at the 2', 3', or 5' positions, by changing the furanose stereochemistry from a ribose to a deoxyribose or an arabinose, or by an increase in temperature of 43 degree C.