Awake monkey fMRI and diffusion MRI combined with conventional neuroscience techniques has the potential to study the structural and functional neural network. The majority of monkey fMRI and diffusion MRI experiments...Awake monkey fMRI and diffusion MRI combined with conventional neuroscience techniques has the potential to study the structural and functional neural network. The majority of monkey fMRI and diffusion MRI experiments are performed with single coils which suffer from severe EPI distortions which limit resolution. By constructing phased array coils for monkey MRI studies, gains in SNR and anatomical accuracy (i.e., reduction of EPI distortions) can be achieved using parallel imaging. The major challenges associated with constructing phased array coils for monkeys are the variation in head size and space constraints. Here, we apply phased array technology to a 4-channel phased array coil capable of improving the resolution and image quality of full brain awake monkey fMRI and diffusion MRI experiments. The phased array coil is that can adapt to different rhesus monkey head sizes (ages 4-8) and fits in the limited space provided by monkey stereotactic equipment and provides SNR gains in primary visual cortex and anatomical accuracy in conjunction with parallel imaging and improves resolution in fMRI experiments by a factor of 2 (1.25 mm to 1.0 mm isotropic) and diffusion MRI experiments by a factor of 4 (1.5 mm to 0.9 mm isotropic).展开更多
In this article, a novel designed radio frequency （RF） coil is designed and built for the imaging of puppies in a V-shape permanent magnetic resonance imaging （MRI） system. Two sets of Helmholtz coil pairs with a ...In this article, a novel designed radio frequency （RF） coil is designed and built for the imaging of puppies in a V-shape permanent magnetic resonance imaging （MRI） system. Two sets of Helmholtz coil pairs with a V-shape structure are used to improve the holding of an animal in the coil. The homogeneity and the sensitivity of the RF field in the coil are analysed by theoretical calculation. The size and the shape of the new coil are optimized and validated by simulation through using the finite element method （FEM）. Good magnetic resonance （MR） images are achieved on a shepherd dog.展开更多
The design and development of a new dual-frequency RF probe-head are presented. This probe was initially dedicated for the MRI of both proton (1H) and hyperpolarized Xenon-129 (HP 129Xe) in the rat brain at 2.35 Tesla...The design and development of a new dual-frequency RF probe-head are presented. This probe was initially dedicated for the MRI of both proton (1H) and hyperpolarized Xenon-129 (HP 129Xe) in the rat brain at 2.35 Tesla. It consists of a double-tuned (100 MHz- 27.7 MHz) volume coil, which could be used for both transmitting and receiving, and of a receive-only single-tuned (27.7 MHz) coil. The double-tuned coil consists of two concentric birdcage resonators. The inner one is a low-pass design and it is tuned to 27.7 MHz, while the outer one, tuned to 100 MHz, is high-pass. The receive-only coil is a surface coil which is decoupled from the double-tuned volume coil by an active decoupling circuitry based on the use of PIN diodes. A home-built Transmit/Receive (T/R) driver ensures biasing of the PIN diodes in both volume and surface coils. The original concepts of the design are addressed, and practical details of realization are presented. One of the underlying ideas behind this work is to proceed well beyond the application to the MRI of HP 129Xe. Actually, this design could be easily adapted for a large palette of other MRI applications. Indeed, we tried to make the design versatile, simple and easy to replicate by other research groups, with a low-cost, minimum development time and accepted performances. The prototype was validated at 100 MHz and at 26.4 MHz (sodium-23 resonance frequency at 2.35 T). MRI experiments were performed using phantoms. In vivo 1H images and 23Na spectra of the rat brain are also presented.展开更多
文摘Awake monkey fMRI and diffusion MRI combined with conventional neuroscience techniques has the potential to study the structural and functional neural network. The majority of monkey fMRI and diffusion MRI experiments are performed with single coils which suffer from severe EPI distortions which limit resolution. By constructing phased array coils for monkey MRI studies, gains in SNR and anatomical accuracy (i.e., reduction of EPI distortions) can be achieved using parallel imaging. The major challenges associated with constructing phased array coils for monkeys are the variation in head size and space constraints. Here, we apply phased array technology to a 4-channel phased array coil capable of improving the resolution and image quality of full brain awake monkey fMRI and diffusion MRI experiments. The phased array coil is that can adapt to different rhesus monkey head sizes (ages 4-8) and fits in the limited space provided by monkey stereotactic equipment and provides SNR gains in primary visual cortex and anatomical accuracy in conjunction with parallel imaging and improves resolution in fMRI experiments by a factor of 2 (1.25 mm to 1.0 mm isotropic) and diffusion MRI experiments by a factor of 4 (1.5 mm to 0.9 mm isotropic).
基金supported by the National Key Technology Research and Development Program of China (Grant No. 001BA210A03)
文摘In this article, a novel designed radio frequency （RF） coil is designed and built for the imaging of puppies in a V-shape permanent magnetic resonance imaging （MRI） system. Two sets of Helmholtz coil pairs with a V-shape structure are used to improve the holding of an animal in the coil. The homogeneity and the sensitivity of the RF field in the coil are analysed by theoretical calculation. The size and the shape of the new coil are optimized and validated by simulation through using the finite element method （FEM）. Good magnetic resonance （MR） images are achieved on a shepherd dog.
文摘The design and development of a new dual-frequency RF probe-head are presented. This probe was initially dedicated for the MRI of both proton (1H) and hyperpolarized Xenon-129 (HP 129Xe) in the rat brain at 2.35 Tesla. It consists of a double-tuned (100 MHz- 27.7 MHz) volume coil, which could be used for both transmitting and receiving, and of a receive-only single-tuned (27.7 MHz) coil. The double-tuned coil consists of two concentric birdcage resonators. The inner one is a low-pass design and it is tuned to 27.7 MHz, while the outer one, tuned to 100 MHz, is high-pass. The receive-only coil is a surface coil which is decoupled from the double-tuned volume coil by an active decoupling circuitry based on the use of PIN diodes. A home-built Transmit/Receive (T/R) driver ensures biasing of the PIN diodes in both volume and surface coils. The original concepts of the design are addressed, and practical details of realization are presented. One of the underlying ideas behind this work is to proceed well beyond the application to the MRI of HP 129Xe. Actually, this design could be easily adapted for a large palette of other MRI applications. Indeed, we tried to make the design versatile, simple and easy to replicate by other research groups, with a low-cost, minimum development time and accepted performances. The prototype was validated at 100 MHz and at 26.4 MHz (sodium-23 resonance frequency at 2.35 T). MRI experiments were performed using phantoms. In vivo 1H images and 23Na spectra of the rat brain are also presented.
