2018 年 35 巻 3 号 p. 167-171
Human brain MR imaging has made remarkable advances since the 1970s with many improvements in imaging technologies, such as shorter scanning methods and the use of higher magnetic fields.
A quantitative MRI (qMRI) method with QRAPMASTER (quantification method using quantification of relaxation times and proton density by multi–echo acquisition of saturation–recovery using turbo spin–echo readout) pulse sequence, or well known as synthetic MRI (synthetic MR AB, Linköping, Sweden), enables simultaneous quantification of T1 and T2 relaxation rates, and proton density (PD) in a clinically acceptable time. Based on these quantitative values and with dedicated post–processing software, it is possible to obtain any contrast weighted images, such as T1–weighted, T2–weighted and inversion recovery images, automated brain segmentation and myelin measurement. In addition, axon volume fraction and g–ratio can also be estimated by combining this method and neurite orientation dispersion and density imaging (NODDI). Here, we provide an overview of synthetic MRI in brain diseases, such as Sturge–Weber syndrome and multiple sclerosis.
Diffusion MRI has also shown many developments in the last 40 years since its development. One of the advanced diffusion MRI techniques called Oscillating gradient spin–echo (OGSE) was proposed recently. With OGSE it is possible to reduce the diffusion time compare to conventional diffusion MRI technique. Therefore, OGSE has the potential to distinguish between spatial and viscous restriction. In this article, we show the use of OGSE in epidermoid cyst and acute brain infarction cases.
