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发布于:2018-3-9 12:14:24  访问:6 次 回复:0 篇
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The Secrets To Get Caspase inhibitor Uncovered In Seven Simple Steps
Tube voltage has a more dramatic effect on radiation dosage, which varies approximately with the square of the kVp. Budoff et al. [20] demonstrated the use of 100?kVp with no degradation of image quality reducing radiation dose by 42% using prospective triggering and 40% using retrospective imaging, as compared to 120?kVp (P?Ceftiofur and by using appropriate filters limits the scatter of X-rays towards the detectors [19]. Hausleiter [7] has shown a 1% increase in scan length was associated with a 5% increase in radiation. However, the biggest reduction in dose has occurred with the use of prospective Caspase inhibitor gating acquisition rather than retrospective gating which was the standard at the time of PROTECTION 1 [7]. Despite the difference in dose, Shuman et al. [21] showed there to be minimal difference in image quality whilst Pontone et al. [22] little difference in diagnostic accuracy between the two techniques. Prospective gating was originally used with electron beam CT angiography [4] and subsequently for coronary calcium scoring www.selleckchem.com with multislice CT, and has now been applied to CCTA. As shown in Fig. 1, it turns off the X-ray tube except for a short period of exposure usually at mid-diastole, the point in the cardiac cycle when coronary motion is minimal at slow heart rates. Prospective gating therefore limits radiation to one pre-defined time window of the cardiac cycle, generally centred at 75% in mid diastole [9]. The radiation tube is inactive for the remainder of the cardiac cycle compared to retrospective electrocardiographic gating which applies the radiation throughout [9]. In particular, extremely low exposure radiation doses can be achieved during a narrow ECG window without a need for padding in patients with a slow and regular rhythm as shown in our study. PROTECTION1 [7] reported a mean effective dose of 12?mSv in a large international multicentre study over 50 sites in 2009 compared to 3.39?mSv in our study using prospective gating. In Hausleiter‘s study there was a great deal of variability in the way the studies were performed from site to site and country to country but is likely to be a true representation of real world practice at the time. In the PROTECTION 1 study the acquisition protocol for only 6% of patients was prospective gating, the rest were acquired retrospectively.
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