RESUMEN
PURPOSE: To investigate the relative gain in sensitivity of five histology coils designed in-house to accommodate tissue sections of various sizes and compare with commercial mouse head coils. METHODS: The coil set was tailored to house tissue sections ranging from 5 to1000 µm encased in either glass slides or coverslips. RESULTS: Our simulations and experimental measurements demonstrated that although the sensitivity of this flat structure consistently underperforms relative to a birdcage head coil based on the gain expected from their respective filling factor ratios, our results demonstrate that it can still provide a remarkable gain in sensitivity. Our study also describes preparation protocols for freshly excised sections, as well as premounted tissue slides of both mouse and human specimens. Examples of the exceptional level of tissue detail and the near-perfect magnetic resonance imaging to light microscopic image coregistration are provided. CONCLUSION: The increase in filling factor achieved by the histology radiofrequency (RF) probe overcomes the losses associated with electric leaks inherent to this structure, leading to a 6.7-fold improvement in performance for the smallest coil implemented. Alternatively, the largest histology coil design exhibited equal sensitivity to the mouse head coil while nearly doubling the RF planar area coverage.
Asunto(s)
Aumento de la Imagen/instrumentación , Imagen por Resonancia Magnética/instrumentación , Magnetismo/instrumentación , Microscopía/instrumentación , Microtomía/instrumentación , Imagen Multimodal/instrumentación , Transductores , Animales , Ratones , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Relación Señal-RuidoRESUMEN
Mouse cardiac MR gating using ECG is affected by the hostile MR environment. It requires appropriate signal processing and correct QRS detection, but gating software methods are currently limited. In this study we sought to demonstrate the feasibility of digital real-time automatically updated gating methods, based on optimizing a signal-processing technique for different mouse strains. High-resolution MR images of mouse hearts and aortic arches were acquired using a chain consisting of ECG signal detection, digital signal processing, and gating signal generation modeled using Simulink (The MathWorks, Inc., Natick, MA, USA). The signal-processing algorithms used were respectively low-pass filtering, nonlinear passband, and wavelet decomposition. Both updated and nonupdated gating signal generation methods were tested. Noise reduction was assessed by comparison of the ECG signal-to-noise ratio (SNR) before and after each processing step. Gating performance was assessed by measuring QRS detection accuracy before and after online trigger-level adjustments. Low-pass filtering with trigger-level adjustment gave the best performance for mouse cardiovascular imaging using gradient-echo (GE), spin-echo (SE), and fast SE (FSE) sequences with minimum induced delay and maximum gating efficiency (99% sensitivity and R-peak detection). This simple digital gating interface will allow various gating strategies to be optimized for cardiovascular MR explorations in mice.