Tomoaki Miyazawa

Evaluation of regional liver function by gadolinium-EOB-DTPA-enhanced MR imaging.

We evaluated the role of magnetic resonance (MR)imaging withgadolinium-ethoxybenzyl-diethylenetriamine-pentaaceticacid (Gd-EOB-DTPA), in estimating regional liverfunction in a rat ischemia-reperfusion model. Ischemic liver damage was induced in theright lobe by vascular clamping for 0 (sham), 30 (I-30),60 (I-60), and 90 min (I-90 group). The ischemic lobesin the I-60 and I-90 groups was clearly visualized as a high intensity area in the T1 images atlate phase of Gd-EOB-DTPA enhancement, Moreover, the T1/2 of signal intensity in ischemic lobes significantlycorrelated with the duration of vascular clamping. We also observed significant correlationbetween T 1/2 and ATP concentration in the liver tissue(r = –0.719, P = 0.04). Our results indicate thatMR imaging with Gd-EOB-DTPA is useful for evaluation of regional liver function in rats.

Effect of resovist on rats with different severities of liver cirrhosis.

Kato N, Ihara S, Tsujimoto T, et al. Effect of Resovist on rats with different severities of liver cirrhosis. Invest Radiol 2002;37:292–298. rationale and objectives. Whether the degree of diffuse hepatic damage is correlated with the signal change on MR images after injection of superparamagnetic iron oxide (SPIO) particles was investigated. In addition, we investigated whether hepatic function deteriorates after injection of SPIO. methods. Seventy-six female Sprague-Dawley rats aged 3 to 4 weeks were given drinking water containing 0.03% thioacetamide (TAA) for 4 or 12 weeks to induce two grades of liver injury. Seventeen normal rats were served as a control. Normal and model rats were administered Resovist (10 &mgr;mol Fe/kg), and signal intensities in the liver on MR images obtained at 4.7 T were measured up to 60 minutes after injection (n = 5). The model rats were injected with 10 times the envisaged dose of Resovist (100 &mgr;mol Fe/kg) or saline as a control substance, and blood parameters were measured at 4, 24, and 48 hours after injection (n = 5 or 6). At 4 hours after injection, iron and Kupffer cells in the liver were stained (n = 3). results. Maximal signal reduction in the liver occurred 15 minutes after injection in all groups. The reduced signal persisted for 60 minutes after injection. However, the degree of maximal signal reduction in the model rats was significantly less than that in the normal rats (P < 0.05, 0.01). Signal reduction in the 12-week group was less than that in the 4-week group. In control rats, the number of iron-positive cells increased by 22 cells per area (0.065 mm2) following treatment with Resovist. In the 4-week and 12-week groups, numbers of iron-positive cells increased by 13 and 11 cells, respectively. There was no statistically significant difference in the number of Kupffer cells between control and model rats. No significant change was observed in blood parameters with Resovist. conclusion. The MR signal induced by Resovist depended on the degree of phagocytic activity in the liver. The safety profiles of Resovist remained unchanged even at 10 times the imaging dose.

Solid Solution Hardening Effect of Ir

Solid solution hardening effects of Ir was investigated to develop high temperature materials at 2223 K. Pt, Rh, Hf, and Zr were chosen as second elements because their solubility into Ir at 2223 K is over 2at% and the melting temperatures of Ir solid solution are above 2273 K. Compressive strength of Ir solid solution at 2223K were investigated. Solid solution hardening effect of Ir is discussed in terms of lattice parameter change and solubility,

Dose-dependency and rate of decay of efficacy of resovist on MR images in a rat cirrhotic liver model

RATIONALE AND OBJECTIVES To investigate the dose-dependency and half-life of decay of the signal reduction by super-paramagnetic iron oxides on three different spin-echo images in a rat model of cirrhosis. METHODS For normal and cirrhotic liver, signal intensities were measured 15 minutes after injection of Resovist (range, 1-40 mumol Fe/kg) on three different spin-echo images. Subsequently, recovery of signal intensity was monitored up to 2 weeks after injection. RESULTS The dose-dependency of efficacy was somewhat less at all doses and imaging parameters in cirrhotic liver. However, the submaximal effect was obtained at a dose of 20 mumol Fe/kg, the same as in normal liver. The rate of decay of the efficacy in cirrhotic liver was similar to or faster than that in normal liver. CONCLUSIONS The dose-dependency and rate of decay of efficacy of Resovist in cirrhosis were similar to those in normal liver, although the efficacy was less in cirrhotic liver and both the dose-dependency and rate of decay of efficacy were dependent on imaging parameters.

Experimental hepatic dysfunction: Evaluation by MR imaging with Gd-EOB-DTPA

Gadolinium (Gd)-ethoxylbenzyl (EOB)-diethylenetriamine-pentaacetic acid (DTPA) is a paramagnetic contrast agent for hepatobiliary magnetic resonance (MR) imaging. Some experimental animal studies have shown the potential of this contrast medium for the detection of liver tumors and have also investigated liver enhancement with this agent in hepatic injury (1-3). However, to our knowledge, there has been no report evaluating liver enhancement with this contrast agent in models with different degrees of severity of hepatic dysfunction. The purpose of this study was to investigate the potential of Gd-EOB-DTPA for the evaluation of liver dysfunction due to chemically induced hepatitis or to surgical damage.

Superparamagnetic Iron Oxide Enhanced Magnetic Resonance Imaging of Rat Liver with Hepatocellular Carcinoma and Benign Hyperplastic Nodule

RATIONALE AND OBJECTIVES The authors assess the potential of a new superparamagnetic iron oxide (SPIO) in grading hepatocellular carcinoma (HCC) histologically and in differentiating HCC from benign hyperplastic nodule (HPN). METHODS Nine Wistar rats (with poorly to moderately differentiated HCC, well-differentiated HCC, and HPN) received drinking water containing N-nitrosomorpholine, and were examined by magnetic resonance imaging (4.7 tesla). Spin-echo images (repetition time/echo time, 600/24.5 mseconds) were obtained before and 15 minutes after intravenous administration of 10 mumol Fe/kg of SH U 555A. RESULTS Poorly to moderately differentiated and well-differentiated HCC showed no significant change in signal-to-noise ratio (SNR) 15 minutes after contrast, whereas HPN showed a significant decrease in SNR. The contrast-to-noise ratio (CNR) between each kind of tumor and adjacent liver parenchyma showed a significant increase at 15 minutes after contrast. CONCLUSIONS The SPIO discussed in this article may help to differentiate HCC from HPN, but it remains difficult to grade hepatocellular carcinoma histologically.

Friction stir welding of 304 stainless steel using Ir based alloy tool

Abstract In order to investigate the durability of an Ir based alloy tool, friction stir welding (FSW) of 304 stainless steel plates was performed under various welding conditions, and the mechanical properties of the joints were measured. Defect free joints are possible under certain conditions, and the mechanical properties of the joints are the same as the base material. When the rotation pitch is ∼0·3, the degree of wear of the Ir based alloy tool with 1·4 mm probe height, which was used for the FSW of a 304 stainless steel plate with 2 mm thickness, was less than or equal to that of the polycrystalline cubic boron nitride tool with 2 mm probe height, which was used for the FSW of a 304 stainless steel plate with 9 mm thickness. The result of the tool life test in this study showed that the Ir based alloy tool enabled the FSW of 304 stainless steel over a 75 m length.

Evaluation of regional liver damage by magnetic resonance imaging with superparamagnetic iron oxide in rat liver.

The purpose of this study was to investigate whether regional liver damage could be detected by means of enhanced MR imaging with a superparamagnetic iron oxide (SH U 555A) in an ischemia–reperfusion model of rat liver. Ischemic liver damage was induced in the right lobe by vascular clamping for 0 (sham), 30 (I-30), 60 (I-60), and 90 minutes (I-90). There was no significant difference in relative enhancement (RE) between the ischemic and nonischemic lobes in the sham, I-30 and I-60 groups, while RE of the ischemic lobe was significantly lower than that of its nonischemic counterpart in the I-90 group as seen on SH U 555A enhanced proton density spin echo images (P < 0.05). Histological examination revealed that iron deposits were significantly smaller in the ischemic than the nonischemic lobe in the I-90 group (P < 0.05), although there was no significant difference in the number of Kupffer cells. Our results indicate that severe regional liver damage can be evaluated by MR imaging with SH U 555A.

Development of high strength Ir based alloy tool for friction stir welding

Abstract The friction stir welding (FSW) tools for high temperature materials are required to have high performance at elevated temperatures. The purposes of this study are to strengthen iridium with an excellent oxidation resistance at elevated temperatures and to develop an FSW tool for high temperature materials. As a result, it was clarified that Ir based alloys are strengthened by the addition of elements with a larger atomic radius than that of Ir, and Zr was the most effective element in this study. Ir–10Re–1Zr has excellent mechanical properties and oxidation resistance at elevated temperatures. The FSW tool made from this alloy was hardly worn even if the SUS 304 stainless steel was friction stir welded.

In vivo kinetics of microbubbles of SH U 508 A (Levovist®): comparison with Indocyanine Green in rabbits

The aim of this study was to evaluate in vivo kinetics of microbubbles of SH U 508 A, in comparison with Indocyanine Green, a dye used as an indicator of blood flow. Microbubble kinetics were evaluated in various vessels (i.e., vena cava, aorta, renal artery, renal vein and portal vein) in rabbits after injection of SH U 508 A by measuring Doppler signals (n = 5). The kinetics of Indocyanine Green were evaluated by measuring absorbance using a photodiode (n = 5). Test substances (SH U 508 A 300 mg/mL and Indocyanine Green 1.25 mg/mL) were injected IV at a dose of 0.1 mL/kg B.W. Peak signal intensity was observed immediately after injection of SH U 508 A, followed by biphasic decay. The rates of biphasic decay were similar in all vessels. A second peak of the signal, which indicated recirculation of the microbubbles, was observed in the vena cava. The circulation and recirculation times of the microbubbles after injection of SH U 508 A were similar to that of Indocyanine Green. These findings suggest that the majority of SH U 508 A microbubbles circulate through the body similarly to blood flow, without retention, in the vasculature.