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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Pressure-volume loop experiments ： ウィキペディア英語版 Pressure-volume loop experiments Pressure Volume loops are widely used in basic and preclinical research. Left ventricular PV loops are considered to be the gold standard for hemodynamic assessment and are widely used in research to evaluate cardiac performance. While it has long been possible to measure pressure in real time from the left ventricle, measuring the volume was technically more difficult. The use of ultrasonic sonomicrometry and the development of the conductance catheter triggered renewed interest in PV loops studies. In sonomicrometry, small ultrasonic transducers (usually referred to as "crystals") transmit signals to each other, and the distance between them is accurately determined based on the transit-time of the signals. By knowing the long and short axis lengths of the ventricle, ventricular volume is easily and accurately determined. Conductance cathethers measure instantaneous conductance in the left ventricle, which is then converted to blood volume using complex formulas and usually after determining and applying various correction factors. Typically only one method is used to perform PV studies in research settings. The miniaturization of sonomicrometer crystals and pressure catheters have made mice PV loop studies feasible and more common. ==Sonomicrometer method== A sonomicrometer system is composed of an electronic signal-processing unit that is connected to small ultrasonic transducers (crystals). A computer acting as a data acquisition and display device obtains data in real time from the signal processor unit, while the crystals are implanted in or on the left ventrical. As few as 2 or as many as 6 crystals can be used to perform 1-axis, 2-axis, or 3-axis length measurements of the axial planes of the heart, usually at a rate of 200 to 2000 times per second. A typical sonomicrometer system has a resolution of 12 micrometres, enabling high-resolution measurements of the axial lengths. Ventricular volume is computed directly (either in micro-liters or milli-liters) by combining the axial length measurements in standard spherical or ellipsoidal volume equations: $Volume\; =\; \backslash frac\; \backslash times\; \backslash pi\; \backslash times\; r^3$ (for a single-axis measurement) $Volume\; =\; \backslash frac\; \backslash times\; L\_1\; \backslash times\; L\_2^2$ (for a two-axis measurement, where L1 is the length of the long axis) $Volume\; =\; \backslash frac\; \backslash times\; L\_1\; \backslash times\; L\_2\; \backslash times\; L\_3$ (for a three-axis measurement) When the axial measurements are acquired in terms of millimeters, then the volume units in these equations will be in terms of milliliters. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Pressure-volume loop experiments」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.