Temperature-Dependent Spin-Lattice Relaxation of the Nitrogen-Vacancy Spin Triplet in Diamond.

Spin-lattice relaxation within the nitrogen-vacancy (NV) center's electronic ground-state spin triplet limits its coherence times, and thereby impacts its performance in quantum applications. We report measurements of the relaxation rates on the NV center's |m_{s}=0⟩↔|m_{s}=±1⟩ and |m_{s}=-1⟩↔|m_{s}=+1⟩ transitions as a function of temperature from 9 to 474 K in high-purity samples. We show that the temperature dependencies of the rates are reproduced by an ab initio theory of Raman scattering due to second-order spin-phonon interactions, and we discuss the applicability of the theory to other spin systems. Using a novel analytical model based on these results, we suggest that the high-temperature behavior of NV spin-lattice relaxation is dominated by interactions with two groups of quasilocalized phonons centered at 68.2(17) and 167(12) meV.

Image guided aneurysm surgery in a Brainsuite® ioMRI Miyabi 1.5 T environment.

OBJECTIVE: Current literature only gives sparse account of aneurysm surgery in an intraoperative MRI environment. After installation of a BrainSuite(®) ioMRI Miyabi 1.5 T at our institution the aim of the present preliminary study was to evaluate feasibility, pros and cons of aneurysm surgery in this special setting. MATERIAL AND METHODS: Since February 2009, during a 3 months period we performed elective image guided aneurysm surgery in 4 ACM and 1 ACOM aneurysm (four patients) in this ioMRI setting. The patients' heads were rigidly fixed in the Noras 8-Channel OR Head Coil. Our imaging protocol included MP-RAGE, T2-TSE axial, TOF-MRA and diffusion-/perfusion-imaging immediately before surgery and after clip application. Presurgical 3D-planning was performed using the iPlan®-Software. RESULTS: All five aneurysms were operated without temporary clipping. There were no intra- or postoperative complications. Patient positioning and head fixation with the integrated Noras Head Clamp was feasible, but there were significant limitations particularly with regard to more complex approaches and patient physiognomy. Image quality especially TOF-MRA was good in 4, insufficient in 1 aneurysm. Presurgical planning especially vessel extraction from TOF-MRA was possible but certainly needs significant future improvement. Diffusion- and perfusion weighted examinations yielded good image quality. CONCLUSION: Our limited experience is encouraging so far. Further improvement particularly concerning flexibility of patient positioning and presurgical 3D-planning for vascular procedures is most necessary. As a future perspective image guided aneurysm surgery in an ioMRI-environment may be helpful especially in complex aneurysms and provide neurosurgeons and neuroanaesthesiologists with additional information about cerebral haemodynamics and perfusion pattern in the vascular territory distal to the target vessel.

A minimally invasive metabolic test with intramuscular injection of halothane 5 and 6 vol% to detect probands at risk for malignant hyperthermia.

We hypothesised that intramuscular halothane injection increases local Pco(2) concentrations in malignant hyperthermia susceptible (MHS) but not in non-susceptible (MHN) individuals. Pco(2) probes with attached microtubing catheters for halothane injection were placed into the lateral vastus muscle of eight MHS and eight MHN probands. Following equilibration, a single bolus of 200 microl halothane 5 and 6 vol% was injected. Pco(2) was measured spectrophotometrically. Baseline Pco(2) concentrations were similar between groups. Maximum Pco(2) and maximum rate of Pco(2) increase was significantly enhanced by halothane 5 and 6 vol% in MHS compared to MHN probands. Systemic haemodynamic and metabolic parameters did not differ between both groups. Local halothane application induces a hypermetabolic reaction with a significant Pco(2) increase in MHS compared to MHN probands, indicating a susceptibility to malignant hyperthermia. Intramuscular halothane injection with Pco(2) measurement seems to be a suitable method for the development of a minimally invasive metabolic test to diagnose malignant hyperthermia susceptibility.