抄録
MRI systems have recently undergone dramatic improvement in capability with innovations in technology and technique. The higher magnetic field strength of 3T MR systems have provided higher SNR than previous 1.5T MR systems, thereby improving spatial resolution, temporal resolution and/or a combination of both. Phased-array coils have also increased SNR and with parallel imaging has improved spatial and/or temporal resolution. And diffusion weighted imaging, when applied to abdominal MR, has allowed better detection of small lesions than conventional MRI and has enabled the prediction of treatment response of malignant tumors and evaluation of treatment efficacy. DWI also has the potential to evaluate the degree or severity of liver fibrosis or cirrhosis. Another improvement in MR technology is in the availability of various tissue specific MR contrast agents based on their distribution in the body. Extracellular contrast agents are generally used in abdominal MRI and are helpful for the detection of hypervascular lesions. Hepatocyte specific agents can be used as a positive contrast agent of the liver on T1-weighted images. And RES specific contrast agent is taken by the RES system and works as a negative contrast agent by darkening the normal liver on T2-weighted images. Most recently, hybrid contrast agents which have both the characteristics of extracellular and hepatocyte specific contrast agents have been developed. With these developments of the MRI system, diagnostic accuracy has been much improved.
