Comparison between spectrum and time interval histogram of ultrasound Doppler signals

The relation between the time interval histogram (TIH) and the spectrum of an ultrasound Doppler signal is investigated theoretically. It is shown that the TIH displays well the center frequency as well as the width of a spectrum but does not give any more detailed information about the shape of the spectrum.     

An isothermal flowmeter with improved frequency response for measuring tissue blood flow

Summary An isothermal flowmeter with improved frequency response for measuring tissue blood flow was developed using thermistors. Direct heating of the thermistors allows a simple construction of small (0.5 mm outer diameter) capillary probes which do not require any additional heating coil. The changes of a feedback current necessary to keep the thermistor at a constant increment above tissue temperature indicate tissue blood flow; a second thermistor compensates variations of tissue temperature. The dynamic performance of the device shows a low-pass characteristic with a cut-off frequency higher than 5 Hz. For low flow rates the output signal was found to be proportional to the flow; for higher flow rates a linearization was necessary. Since tissue temperature can be recorded continuously, intermittent quantitative in-vivo calibration seems possible by evaluation of heater off curves in the perfused and non-perfused tissue. As the flowmeter is insensitive to tissue temperature, it can be used for long-term recordings.This study was supported by the Deutsche Forschungsgemeinschaft (SFB 90, Kardiovasculäres System)A preliminary report of a part of this investigation has been presented at the 46. Meeting of the Deutsche Physiologische Gesellschaft: Pflügers Arch., Suppl.362, R 53 (1976)     

术中判断肠活力三种方法的比较

术中准确地评价肠活力是外科医师面临的一个普遍问题。应用兔肠缺血模型，比较静脉荧光素、表面血氧测定和激光多普勒三种技术判断肠活力的精确性。结果：诊断效率静脉荧光素法为７８％，表面血氧测定为６８％，激光多普勒为９５％。后者精确度显著优于前二者，且操作简便、迅速，具有临床应用前景。