20-MHz phased array ultrasound transducer for in vivo ultrasound imaging of small animals.

In vivo ultrasound imaging with phased array transducers is of great importance for both clinical application and biomedical research. In this work, relaxor ferroelectric PMN-0.28PT single crystal with very high piezoelectric constant d33 ≥ 2000 pC/N and electromechanical coupling coefficient k33 âˆ¼ 0.92 is used to fabricate high-frequency phased array transducers. A 128-element 20-MHz phased array transducer is successfully fabricated, and the optimized performance of -6 dB average bandwidth of âˆ¼ 84 % and insertion loss of -43 dB are achieved. The axial and lateral imaging resolutions of the transducer are determined to be 81 µm and 243 µm, respectively. With Verasonics image platform, in vivo fisheye images are acquired, demonstrating the potential application of our developed high-frequency phased array transducer for biomedical research on small animals.

Low-field Switching Four-state Nonvolatile Memory Based on Multiferroic Tunnel Junctions.

Multiferroic tunneling junction based four-state non-volatile memories are very promising for future memory industry since this kind of memories hold the advantages of not only the higher density by scaling down memory cell but also the function of magnetically written and electrically reading. In this work, we demonstrate a success of this four-state memory in a material system of NiFe/BaTiO3/La0.7Sr0.3MnO3 with improved memory characteristics such as lower switching field and larger tunneling magnetoresistance (TMR). Ferroelectric switching induced resistive change memory with OFF/ON ratio of 16 and 0.3% TMR effect have been achieved in this multiferroic tunneling structure.

Color Doppler ultrasound detection and classification of the tangential hepatic vein before laparoscopic cholecystectomy.

BACKGROUND: Unexpected fatal bleeding from the gallbladder bed during laparoscopic cholecystectomy is often associated with injury to the middle hepatic vein. This paper studies whether preoperative color Doppler ultrasound is effective in reducing the risk of injury. Also a venous classification is suggested. METHODS: Between June 1999 and February 2004, 2,146 patients undergoing laparoscopic cholecystectomy by standard method received preoperative color Doppler ultrasound examinations. The closest distance between the hepatic vein and the gallbladder was studied. Also, cases of liver cirrhosis, number of conversions to open cholecystectomy, intraoperative blood loss, operative time, complications, and hospital stay were recorded (group D). At the end of the study, we retrospectively reviewed the same parameter of another 2,146 patients who received laparoscopic cholecystectomy without preoperative color Doppler ultrasound between the period of March 1995 and June 1999 (group ND). RESULTS: In group D, 108 patients had cirrhosis. Four hundred and ninety-six patients (27 cases of cirrhosis) had a closest distance of 1 mm or less between the vein and the gallbladder. There were two conversions to open cholecystectomy, but none related to gallbladder bed bleeding. In group ND, there were five conversions, including four cases of gallbladder bed bleeding from the middle hepatic vein and one case of severe adhesion. The conversion rate was significantly higher. In group ND, the mean intraoperative blood loss in the cases of liver cirrhosis was significantly greater. Also, the operative time of patients with the closest vein and gallbladder distance of 1 mm or less in group D was significantly longer. CONCLUSIONS: Color Doppler ultrasound is an effective method for detecting the presence of potential bleeders. Although the operative time will be a bit longer, the operation can be done under meticulous care and complete preparation, so that the conversion rate and the risk of fatal hemorrhage can be reduced, especially in patients with liver cirrhosis.

Detecting awareness during general anaesthetic caesarean section. An evaluation of two methods.

Seventy-four patients received general anaesthesia for Caesarean section. Seven percent of the elective group and 28% of the emergency patients reported dreaming or recall of voices during the procedure (p less than 0.05) at postoperative interview. One patient from each group reported feeling pain or suffocation. All patients were monitored for awareness using the isolated forearm technique and lower oesophageal contractility. Provoked lower oesophageal contractility was the most effective of the different indices. A value greater than 35 mmHg on at least one occasion had a false negative rate of 33%, a false positive rate of 28% and a predictive value of 25%. A value greater than 13 mmHg picked up all patients who dreamed, with a false positive rate of 68%. Both of the 'aware' patients had provoked lower oesophageal contractility response of greater than 70 mmHg, an attribute shared by only 8% of the rest. The isolated forearm was particularly ineffective.