Synthesis of optically active star polymers consisting of helical poly(phenylacetylene) chains by the living polymerization of phenylacetylenes and their chiroptical properties.

Star polymers consisting of three helical poly(phenylacetylene) chains with a precisely controlled molecular weight (molar mass dispersity < 1.03) were successfully synthesized by the living polymerization of phenylacetylene derivatives with a Rh-based multicomponent catalyst system comprising trifunctional initiators, which have three phenylboronates centered on a benzene ring, the Rh complex [Rh(nbd)Cl]2, diphenylacetylene, triphenylphosphine, and a base. The analysis of chiroptical properties of the optically active star polymers obtained by the living polymerization of optically active phenylacetylene derivatives revealed that the star polymers exhibited chiral amplification properties owing to their unique topology compared with the corresponding linear polymers.

[Usefulness of short inversion time inversion recovery-low B diffusion weighted imaging after pouring in gadolinium- ethoxybenzyl-diethylene-triaminepentaacetic acid].

Diffusion weighted imaging (DWI) using a low b value for examination of the body is not common, so we examined its usefulness. Phantom experiments were performed in which I changed the length of the echo time (TE), with and without short inversion time inversion recovery (STIR). The signal intensity of each phantom was reduced by using a longer TE or by combination with STIR, but contrast was improved. We noted a similar pattern in clinical cases, and concluded that the results of the phantom study and clinical cases indicated the potential usefulness of TE with moderate STIR. Low-b DWI using appropriate imaging parameters gave better results than high-b DWI followed by visual assessment. The T1 value of normal liver cells is shortened by incorporating gadolinium-ethoxybenzyl-diethylene-triaminepentaacetic acid (Gd-EOB-DTPA). Normal liver cells are close to the null point in STIR-low-b DWI under these conditions. The signal-to-noise ratio (SNR) of normal liver cells thus decreases, unlike that for tumors containing no normal liver cells, giving improved contrast. At high SNRs, the use of low-b DWI provides several advantages: the anatomical location structure is easy to identify, and there is less left lateral division of liver signal degradation. We thus conclude STIR-low-b DWI after injection of Gd-EOB-DTPA to be a useful technique.

[Imaging characteristics of two-dimensional spin echo T1-weighted image in carotid artery plaque].

Recently, T1 weighted image (T1WI) has proven to be useful for diagnosing carotid plaque. This time, the image parameter of two-dimensional spin echo (2D SE) T1WI was examined. Phantoms that imitated muscle and carotid plaque were made. Signal noise ratio (SNR) and the contrast of phantoms were examined when the flip angle (FA) of radio frequency (RF) pulse, repetition time (TR), and echo train length (ETL) was changed. A visual evaluation was done in a clinical case. Both SE and fast spin echo (FSE) SNR improved according to the extension of TR, and the contrast decreased. Moreover, the contrast improved when there was a lot of ETL and the FA of RF pulse. It is thought that this is because SNR and the contrast depend on the interrelation of TR, T1 value, and the FA of RF pulse. When the FA of RF pulse was set to 70 degrees and the TR was set to 400 ms resulting from the phantom experiment, clinical cases obtained great results. This examination confirmed the utility of 2D SE in carotid plaque inspection.