Combining Dipole and Loop Coil Elements for 7 T Magnetic Resonance Studies of the Human Calf Muscle.

Combining proton and phosphorus magnetic resonance spectroscopy offers a unique opportunity to study the oxidative and glycolytic components of metabolism in working muscle. This paper presents a 7 T proton calf coil design that combines dipole and loop elements to achieve the high performance necessary for detecting metabolites with low abundance and restricted visibility, specifically lactate, while including the option of adding a phosphorus array. We investigated the transmit, receive, and parallel imaging performance of three transceiver dipoles with six pair-wise overlap-decoupled standard or twisted pair receive-only coils. With a higher SNR and more efficient transmission decoupling, standard loops outperformed twisted pair coils. The dipoles with standard loops provided a four-fold-higher image SNR than a multinuclear reference coil comprising two proton channels and 32% more than a commercially available 28-channel proton knee coil. The setup enabled up to three-fold acceleration in the right-left direction, with acceptable g-factors and no visible aliasing artefacts. Spectroscopic phantom measurements revealed a higher spectral SNR for lactate with the developed setup than with either reference coil and fewer restrictions in voxel placement due to improved transmit homogeneity. This paper presents a new use case for dipoles and highlights their advantages for the integration in multinuclear calf coils.

New approach to quantifying acute stress in cataract surgeons to investigate the relationship between surgeon experience and intraoperative stress.

PURPOSE: To quantify intraoperative stress levels in cataract surgeons and investigate the relationship between intraoperative stress and surgeon experience. SETTING: Department of Ophthalmology, Hanusch Krankenhaus, Vienna, Austria. DESIGN: Prospective, observational case series. METHODS: 5 ophthalmologists with surgery experiences of 70 to 15 000 previous surgeries volunteered for this study. Surgeons' heart rate (HR) and heart rate variability (HRV) were measured during a total of 45 cataract surgeries. HR and HRV values were normalized to the minimal HR and maximal HRV of an overnight baseline measurement. The resulting normalized HR measure and HRV stress index are stress dependent and comparable between subjects. No case selection was performed. RESULTS: Less experienced surgeons showed higher HRV stress indices; differences between the surgeons with less than 180 and 500 surgeries and the 2 with 600 and 1500 surgeries, respectively, were statistically significant (α = 0.05). No statistically significant difference in stress indices was found between surgeons with 1500 and 15 000 surgeries, suggesting that there may be a plateau effect after 1500 surgeries. HRV stress indices and case times were negatively correlated with the logarithm of experience in the number of previously performed surgeries (r2 = 0.67 and 0.52). No significant stress buildup over multiple successive surgeries was found (α = 0.05). CONCLUSIONS: The new HRV stress index is a simple but powerful tool for quantifying intraoperative stress in cataract surgeons. Decreases in stress with increasing experience are congruent with previous works on general surgeons' stress and follow a similar timeline as previously published, proficiency-based learning curves for cataract surgery.

Thermal field formation during wIRA-hyperthermia: temperature measurements in skin and subcutis of piglets as a basis for thermotherapy of superficial tumors and local skin infections caused by thermosensitive microbial pathogens.

Purpose: The temporal and spatial formation of the temperature field and its changes during/upon water-filtered infrared-A (wIRA)-irradiation in porcine skin and subcutis were investigated in vivo in order to get a detailed physical basis for thermotherapy of superficial tumors and infections caused by thermosensitive microbial pathogens (e.g., Mycobacterium ulcerans causing Buruli ulcer). Methods: Local wIRA-hyperthermia was performed in 11 anesthetized piglets using 85.0 mW cm-2, 103.2 mW cm-2 and 126.5 mW cm-2, respectively. Invasive temperature measurements were carried out simultaneously in 1-min intervals using eight fiber-optical probes at different tissue depths between 2 and 20 mm, and by an IR thermometer at the skin surface. Results: Tissue temperature distribution depended on incident irradiance, exposure time, tissue depths and individual 'physiologies' of the animals. Temperature maxima were found at depths between 4 and 7 mm, exceeding skin surface temperatures by about 1-2 K. Tissue temperatures above 37 °C, necessary to eradicate M. ulcerans at depths <20 mm, were reached reliably. Conclusions: wIRA-hyperthermia may be considered as a novel therapeutic option for treatment of local skin infections caused by thermosensitive pathogens (e.g., in Buruli ulcer). To ensure temperatures required for heat treatment of superficial tumors deeper than 4 mm, the incident irradiance needed can be controlled either by (a) invasive temperature measurements or (b) control of skin surface temperature and considering possible temperature increases up to 1-2 K in underlying tissue.