Biomedical subjects

I K Hong

Publications and source records attributed to I K Hong.

3 recordsLinked to original sources

PubMed1998

A new silent magnetic resonance imaging using a rotating DC gradient.

A new approach to silent MR imaging using a rotating DC gradient has been explored and experimentally studied. Acoustic or sound noise has been one of the problems in examining patients, mainly due to the fast gradient pulsings in interaction with the main magnetic field. The sound noise has been noted to be proportionately louder as the magnetic field strength becomes larger. In this report, we describe a new imaging technique using a mechanically rotating DC gradient coil. The rotating DC gradient coil can effectively replace both phase encoding as well as readout gradient pulsings, and data obtained in this manner can provide a set of projection data that later can be used for projection reconstruction. With some interpolation techniques one can also perform conventional two-dimensional fast Fourier transform image reconstruction. The sound noise intensity compared with the conventional imaging technique, such as the spin-echo sequence, has been reduced down to about -20.7 dB or 117.5 times with this new technique. The experimental pulse sequence and its principle are described and images obtained by the new silent MR imaging technique are reported.

Equipment Design↗

PubMed1996

Some new observations on pulse sequence dependent diffusion related edge enhancement in MR microscopy.

Self-diffusion of nuclear spins has been suggested to cause edge enhancement in images especially on a microscopic scale. According to previously published work, theory suggests that edge enhancement is caused by motional narrowing due to the boundaries and spin self-diffusion during the data acquisition period. More careful examination reveals that edge enhancement due to motional narrowing develops only under a few specific conditions. This lack of generality of motional narrowing theory, as well as experimental observations, indicate that edge enhancement due to effects other than motional narrowing alone can exist. It is found that edge enhancement depends greatly on the data acquisition mode; therefore, the images obtained are different depending on the pulse sequence employed. For example, excessive attenuation of DC components due to diffusion can result in edge enhancement in the spin echo signal. However, in the case of FID-like signals, DC components are preserved while positive high frequency parts are attenuated, thereby degrading resolution. The new phenomenon observed has been termed selective spectral suppression since the observed edge enhancement results from the selective attenuation of certain frequency components in the nuclear signals due to diffusion-dependent signal attenuation for a given pulse sequence.

Diffusion↗

PubMed1993

A case of biliary ascariasis accompanied by cholelithiasis.

A 43-year-old Korean woman with biliary ascariasis accompanied by cholelithiasis is reported. Her chief complaints were abdominal pain, nausea, and vomiting. She had the past history of several attacks of abdominal pain in her childhood. Biliary stones were recovered from the left hepatic duct after cholecystectomy, which contained degenerated cuticle or body wall, and numerous eggs of Ascaris lumbricoides. It is strongly suggested that the biliary stones were formed from the dead Ascaris worm(s). This is a rare case of biliary ascariasis during the recent 5 years in Korea.

Adult↗