It is a technological difficulty to acquire data from ultrasound with ultra-band in the study of microwave-induced thermoacoustic tomography. A high-speed data acquisition system for the ultrasonic signal with a frequency fewer than 500 MHz is designed in the paper. The result obtained demonstrates that the system holds good for microwave-induced thermoacoustic tomography.

Objective To evaluate the plasma amino acid level alteration and determine amino acid loss in patients with abdominal inflammation and acute renal failure during continuous veno-venous hemofiltration (CVVH). Methods Ten patients with abdominal infection and acute renal failure were admitted to the Nanjing General Hospital of Nanjing Military Command of PLA from September 2008 to September 2009. CVVH was performed with AV600S polysulfone hemofilter for 24 hours. Samples of plasma amino acid were obtained before,at 12 and 24 hours after the beginning of CVVH. High pressure liquid chromatography was used to detect amino acid concentrations in plasma and replacement fluid. All data were analyzed using t test or Wilcoxon rank sum test. Results Of the ten patients, three died of septic shock and three died of multi-organ dysfunction syndrome.The level of plasma amino acids decreased significantly after CVVH, and the levels of histidine, isoleucine, cysteine and glutamine decreased from (22.1 ±10.3), (20.0 ±7.6), (10.3±4.7), (122.3 ±72.2)μmol/L to (5.6 ±3.4), ( 6.4 ± 2.5 ), ( 2.9 ± 2.4 ), (42.5 ± 33.6) μ mol/L. The total plasma amino acid levels significantly reduced by 52% at 12 hours after the beginning of CVVH and by 59% at 24 hours after the beginning of CVVH.The mean amino acid loss was (9631± 1089)mg/d. The mean losses of essential and non-essential amino acids were ( 5072 ± 618 ) mg/d and ( 3747 ± 654 ) mg/d, respectively, with a significant difference ( t = 4. 52,P ＜0.05 ). There was a positive correlation between individual amino acid loss and the plasma concentrations of respective amino acids at 12 hours after the beginning of CVVH ( r = 0. 68, P ＜ 0.05 ). Conclusions Plasma amino acid would be cleared through hemofilter during CVVH in patients with abdominal inflammation and acuterenal failure. As a result, it is necessary to take account of the ultrafiltrate amino acid loss when setting nutritional schedule, especially increasing the non-essential amino acid content of total parenteral nutrition.