The postoperative neurological complications is associated with intraoperative cerebral emboli, which results from extracorporeal circulation and operation. It can effectively reduce the incidence of neurological complications with ultrasonic radiation. In fluids, a particle will change it's motion trail when it is acted by the radiation force generated by the ultrasound. This article mainly discuss how to shielding emboli with ultrasound. The equipment can transmit phased ultrasonic signals, which is designed on a FPGA development board. The board can generate a square wave, which is converted into a sine wave through a power amplifier. In addition, the control software has been developed on Qt development environment. The result indicates it's feasible to shielding emboli with ultrasonic radiation force. This article builds a strong foundation for the future research.
Humans ; Intracranial Embolism ; diagnostic imaging ; prevention & control ; Intraoperative Complications ; prevention & control ; Postoperative Complications ; prevention & control ; Ultrasonics ; instrumentation ; Ultrasonography

In this paper, according to the requirement of the focused sound field measurement, a focused sound field measurement system was established based on the LabVIEW virtual instrument platform. The system can automatically search the focus position of the sound field, and adjust the scanning path according to the size of the focal region. Three-dimensional sound field scanning time reduced from 888 hours in uniform step to 9.25 hours in variable step. The efficiency of the focused sound field measurement was improved. There is a certain deviation between measurement results and theoretical calculation results. Focal plane--6 dB width difference rate was 3.691%, the beam axis--6 dB length differences rate was 12.937%.
Computer Simulation ; Numerical Analysis, Computer-Assisted ; Software ; Sound

Monte Carlo method was used for calculation of finite-diameter laser distribution in tissues through convolution operation. Photo-thermal ablation model was set up on the basis of Pennes bioheat equation, and tissue temperature distribution was simulated by using finite element method by ANSYS through the model. The simulation result is helpful for clinical application of laser.
Algorithms ; Finite Element Analysis ; Laser Therapy ; Monte Carlo Method ; Temperature

Small-scale intellectualized medical instrument has attracted great attention in the field of biomedical engineering, and LabVIEW (Laboratory Virtual Instrument Engineering Workbench) provides a convenient environment for this application due to its inherent advantages. The principle and system structure of the hyperthermia instrument are presented. Type T thermocouples are employed as thermotransducers, whose amplifier consists of two stages, providing built-in ice point compensation and thus improving work stability over temperature. Control signals produced by specially designed circuit drive the programmable counter/timer 8254 chip to generate PWM (Pulse width modulation) wave, which is used as ultrasound radiation energy control signal. Subroutine design topics such as inner-tissue real time feedback temperature control algorithm, water temperature control in the ultrasound applicator are also described. In the cancer tissue temperature control subroutine, the authors exert new improvments to PID (Proportional Integral Differential) algorithm according to the specific demands of the system and achieve strict temperature control to the target tissue region. The system design and PID algorithm improvement have experimentally proved to be reliable and excellent, meeting the requirements of the hyperthermia system.
Algorithms ; Computer Simulation ; Hyperthermia, Induced ; instrumentation ; Neoplasms ; therapy ; Software Design ; Ultrasonic Therapy ; instrumentation ; methods

Objective To determine the power-time-ablation scope correlogram of a water-cooled single needle electrode radiofrequency (RF) ablation system and to establish a theoretical basis for its practical application.Methods RF ablations were performed using a water-cooled single needle electrode radiofrequency ablation system developed by the authors using fresh ox liver as well as liver and muscles of healthy adult New Zealand white rabbits.The temperature of the ablation area was monitored using a multichannel thermometric system.The maximum ablation scope was determined by detecting the rim at which the temperature was no less than 50 °C.The specific absorption rate (SAR) of the isolated liver tissue was calculated.Results In the treatment voltage range of 100-130V,the process was smooth and steady.No impedance variation was obvious.The maximum diameter of a single ablation was 51 cm.With the treatment voltage at 140-170 V,a larger ablation area could be reached in less time,but eventually the impedance began to increase while the ablation area was no longer expanded.When the treatment voltage reached the range of 180-200 V the impedance almost always increased rapidly out of limits,and the treatment system stopped automatically.The measured SAR value was consistent with the theoretical value.Pathology confirmed that both liver tissue and muscle tissue manifested typical coagulative necrosis.Conclusions The power amplifier,cooling,thermometric and control sections of the RF ablation system worked stably,and the practical ablation effect met the design and clinical treatment requirements.

This paper introduces the simulation and measurement results of the phased-array focused ultrasound field of two-foci pattern.
Ultrasonic Therapy ; methods ; Ultrasonics

This article add mode control module to the phased-array using digital sampling technology which achieved a phase accuracy of 3.75 degrees, making phase, phased signal duration, interval for continuous signal and repeat times pre-configured before the out put of phased signal, to realize the precise timing of phased signal. Experiments indicate that the output of phased signal modulated by mode control can reach the timing precision of 0.48 micros and will not affect the original phase control function t. In addition it can realize intermittent therapy mode which can reduce the injury of non-focal areas caused by ultrasound energy.
Equipment Design ; Signal Processing, Computer-Assisted ; Transducers

In the interactive image-guided thermotherapy, we need the real time image and location of the target tumor. But the current mono-modal imaging technique can not do it. We present a method to register a preoperative 3D MRI volume to a set of intra-operative ultrasound images for the target localization of the liver tumor in the thermotherapy. The registration method is a genetic algorithm based on the features such as liver surface vessels and liver surface.
Humans ; Hyperthermia, Induced ; Image Processing, Computer-Assisted ; Imaging, Three-Dimensional ; Liver Neoplasms ; diagnostic imaging ; therapy ; Magnetic Resonance Imaging ; Ultrasonic Therapy ; methods ; Ultrasonography, Interventional

Objeetive To discuss the correlation of creatinine reduction ratio(CRR2)from posttransplant day 1 to day 2 and early graft function recovery status after kidney transplantation. Methods Clinical data of 80 patients after renal transplantation from Jan 2005 to Mar 2007 were retrospectively analyzed.Patients were divided into three groups according to the post-operative serum creatinine level:53 patients within IGF group[cereatinine＜265.2 μmol/L by post-operative day(POD)no.5],14 patients within SGF group(creatinine＞265.2 μmol/L on POD no.5,but no need for dialysis),and 13 patients within DGF group(need for dialysis in the first week post-transplant).Then the value and 99%CI of CRRz of these three groups were calculated. Results The value of CRR2 of IGF,SGF and DGF was(46.8±14.6)%,(25.6±13.5)%and(0.7±17.7)%respectively.And CRR2 99%CI of IGF,SGF and DGF was 41%-52%,15%-36%and-14%-16 0A respectively.There was significant difference in the value of CRR2 among IGF,SGF and DGF group.So a criteria for early diagnosis of IGF,SGF and DGF by CRR2 99%C1 was established:IGF(CRR2≥40%),SGF (15%＜CRR2＜40%)and DGF(CRR2≤15%). Conclusion CRR2 has a good correlation with early graft function recovery after kidney transplantation,and can be used to predict the occurrence of SGF and DGF.

A small HIFU system was used to investigate the phase-shift droplet vaporization in vivo and its effect on thermal absorption in tissue-mimicking phantoms. The experiments demonstrated that droplets could be vaporized to bubbles in vivo by the small HIFU system and the volume of bubbles could increase by tens of times. With appropriate droplets concentration, lesion volume produced by HIFU could be increased significantly under the same HIFU parameter.
Fluorocarbons ; Image Enhancement ; Ultrasonic Therapy ; methods