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Quantitative measurements are important for imaging fluid content in porous media. Conventional MRI methods suffer from contrast because of relaxation times in porous media, resulting in measurements of apparent fluid content, not the true fluid content. We compare four magnetic resonance imaging methods for fluid content imaging in several water‐saturated reservoir core plugs: frequency‐encoded spin echo, single point ramped imaging with T1 enhancement, hybrid spin echo single point imaging (SE‐SPI), and T2 mapping SE‐SPI. 1‐D profiles obtained with each method were compared in terms of image quality, image sensitivity, and quantification of water content. The image quality of short T2 lifetime samples suffered from blurring in hybrid SE‐SPI images. Image sensitivity was the highest in the profiles obtained with frequency‐encoded spin echo. The quantification of frequency‐encoded spin echo, T2 mapping SE‐SPI, and hybrid SE‐SPI suffered in core plugs with a significant population of short T2 components because of T2 attenuation. Overall, single point ramped imaging with T1 enhancement was found to be the most general method for fluid content imaging. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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SPRITE探测器的电阻是一个重要的器件参数。研究了Hg1-xCdxTe材料组分和电阻率、芯片厚度和表面电导等因素对该电阻的影响,并就实验数据进行了比较结果表明:SPRITE器件的室温电阻主要是受Hg1-xCdxTe材料组份和芯片厚度的影响。而其液氮温度电阻则主要是受芯片表面电导的影响。 相似文献
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为使自动金丝球焊接技术应用于碲镉汞红外器件的研制工艺,在大量试验的基础上,摸索出一套使用自动金丝球焊接技术进行了SPRITE红外器件内引线焊接的可靠方法。文中还对自动焊接的精度和最小间距进行了探讨。 相似文献
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Prado PJ Balcom BJ Mastikhin IV Cross AR Armstrong RL Logan A 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1999,137(2):324-332
A pure phase-encoding MRI technique, single-point ramped imaging withT1enhancement, SPRITE, is introduced for the purpose of gas phase imaging. The technique utilizes broadband RF pulses and stepped phase encode gradients to produce images, substantially free of artifacts, which are sensitive to the gasT1andT*:2relaxation times. Images may be acquired from gas phase species with transverse relaxation times substantially less than 1 ms. Methane gas images,1H, were acquired in a phantom study. Sulfur hexafluoride,19F, images were acquired from a gas-filled porous coral sample. High porosity regions of the coral are observed in both the MRI image and an X-ray image. Sensitivity and resolution effects due to signal modulation during the time-efficient acquisition are discussed. A method to increase the image sensitivity is discussed, and the predicted improvement is shown through 1D images of the methane gas phantom. 相似文献
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N. Jon Shah Joachim B. Kaffanke Sandro Romanzetti 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2009,199(2):136-145
Single point imaging methods such as SPRITE are often the technique of choice for imaging fast-relaxing nuclei in solids. Single point imaging sequences based on SPRITE in their conventional form are ill-suited for in vivo applications since the acquisition time is long and the SAR is high. A new sequence design is presented employing variable repetition times and variable flip angles in order to improve the characteristics of SPRITE for in vivo applications. The achievable acquisition time savings as well as SAR reductions and/or SNR increases afforded by this approach were investigated using a resolution phantom as well as PSF simulations. Imaging results in phantoms indicate that acquisition times may be reduced by up to 70% and the SAR may be reduced by 40% without an appreciable loss of image quality. 相似文献
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用SPRITE探测器的脉冲响应(格林函数)描述了基于时间频率和空间频率变化的SPRITE探测器光学传递函数(OTF)、调制传递函数MTF和相位传递函数(PTF),并由此分析了该探测器对红外辐射图像在时间域和空间域的联合滤波特性 相似文献
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