ABSTRACT
Both 0.2 T and 9.4 T MRI systems were used to image a mouse model of glioma. RF coils were designed for both fields. A spin-echo, multi-echo pulse sequence was used to determine T(2) relaxation times of both brain and tumor tissues. Contrast-to-noise ratio was calculated based on the selected echo time. The results showed that 0.2 T is suitable for mouse model imaging, however total scan time must be long to achieve high enough SNR. T(2) relaxation times of the tumor and brain tissues can be measured at 0.2 T and are 2.1 and 1.8 times respectively longer at 0.2 T than at 9.4 T. Contrast to noise ratio for tumor and brain was better at high field than at the low field. We concluded that 0.2 T may be used to study mouse model of glioma using spin echo pulse sequence, yet the total scan time is long (about 40 min), resolution is lower (â¼250 µm × 250 µm) and slice thickness (3mm) must be large enough to obtain sufficient SNR.
Subject(s)
Brain Neoplasms/pathology , Disease Models, Animal , Glioma/pathology , Image Enhancement/instrumentation , Magnetic Resonance Imaging/instrumentation , Magnetic Resonance Imaging/veterinary , Magnetics/instrumentation , Animals , Equipment Design , Equipment Failure Analysis , Humans , Male , Mice , Mice, Nude , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
Applications of low-field magnetic resonance imaging (MRI) systems (<0.3 T) are limited due to the signal-to-noise ratio (SNR) being lower than that provided by systems based on superconductive magnets (> or = 1.5 T). Therefore, the design of radiofrequency (RF) coils for low-field MRI requires careful consideration as significant gains in SNR can be achieved with the proper design of the RF coil. This article describes an analytical method for the optimization of solenoidal coils. Coil and sample losses are analyzed to provide maximum SNR and optimum B(1) field homogeneity. The calculations are performed for solenoidal coils optimized for the human head at 0.2 T, but the method could also be applied to any solenoidal coil for imaging other anatomical regions at low field. Several coils were constructed to compare experimental and theoretical results. A head magnetic resonance image obtained at 0.2 T with the optimum design is presented.
