Neonatal hypoxic-ischemic encephalopathy (HIE) causes significant and life-long neurologic disability. Therapeutic hypothermia has become the standard treatment for neonates with moderate or severe HIE. It improves overall neurologic outcomes and reduces the incidence of death and disability. Magnetic Resonance Imaging (MRI) assists in defining the nature and extent of HIE. This review discusses the recent topics on the application of MRI on HIE. The following issues on the MRI findings are discussed;

1. The correlation of negative pseudonormalization of diffusion-weighted imaging (DWI) (residual high signal lesions on DWI beyond the first week) and clinical outcome.

2. MRI findings of “total brain injury”, as a new category of HIE caused by prolonged profound asphyxia, are shown with the serial MRI findings, including those from the first and second weeks of life.

3. Pontine and cerebellar injury: to characterize the MRI features of pontine and cerebellar injuries and a background HIE pattern and to localize the injury sites.

4. Pre-Wallerian degeneration preceding Wallerian degeneration (WD): The DWI obtained immediately after a brain injury demonstrates acute corticospinal injury preceding WD, known as “pre-Wallerian degeneration”. It has been observed in infants with neonatal arterial stroke, and neonates with HIE. The characteristics of MRI findings of pre-WD are shown with the background HIE pattern.

5. Diffusion restriction in optic radiation is commonly observed among HIE neonates. This diffusion restriction was associated with transsynaptic neuronal degeneration.

6. Injury to the mammillary body in term neonates with HIE has emerged as a topic in neonatal imaging. Mammillary body injuries during the neonatal period cause mammillary body atrophy and are associated with memory disturbance during later childhood at around 10 years of age.

　Physiological functions such as energy metabolism and free radicals are responsible for maintaining homeostasis of living bodies and play an important role in various diseases and treatments. Therefore, these functions can be used as imaging biomarkers for new disease imaging. Dynamic nuclear polarization (DNP)-MRI is a powerful technique that can be used to obtain the spatio-temporal information of glucose and tissue redox metabolism processes. In this article, we also introduce our study of glucose and in vivo redox metabolic imaging as well as possibilities for clinical application.

Purpose : The purpose of this study was to determine if fusion images from non-contrast magnetic resonance angiography (MRA) and non-contrast computed tomography (CT) can provide useful information for the pretreatment evaluation of peripheral artery disease patients with renal dysfunction prior to interventional radiology (IVR).

Methods : Non-contrast MRA was performed on 3 and 1.5 tesla MR system (Canon Medical Systems Vantage Titan^TM/cS Edition) with a 3D balanced SSFP of the abdomen and an FBI of the lower extremities, respectively.

　Non-contrast CT was performed on a Canon Medical Systems AQUILION-Prime SP. Auto Exposure Control (AEC) was used to reduce radiation dose, and image reconstruction was performed with Adaptive Iterative Dose Reduction (AIDR 3D). Fusion images of the non-contrast MRA with the CT were created at a workstation (FUJIFILM Medical Systems SYNAPSE VINCENT Ver.5.5).

Results : Fusion of the arterial information obtained by non-contrast MRA with the arterial calcification and surrounding bone information obtained by the CT provided a useful image to support the IVR procedures. No preoperative contrast-enhanced CT angiography was performed, thus reducing the overall amount of contrast media used. Appropriate patient immobilization reduced any misalignment between the MRI and CT.

Conclusion : Image fusion techniques of non-contrast MRA with non-contrast CT can provide minimally invasive and useful images to support IVR procedures without the use of contrast agents.