Technical Note: Comparison of megavoltage, dual-energy, and single-energy CT-based μ-maps for a four-channel breast coil in PET/MRI
Technical Note: Comparison of megavoltage, dual-energy, and single-energy CT-based μ-maps for a four-channel breast coil in PET/MRI
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DOI：
10.1002/mp.12407
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发表时间：
2017-09-01
期刊：
影响因子：
3.8
通讯作者：
Gaede, Stewart
中科院分区：
文献类型：
--
作者：
Patrick, John C.;Thompson, R. Terry;Gaede, Stewart
目的：本研究的目的是描述和评估的方法计算兆电压计算机断层扫描（MVCT）衍生的MR硬件衰减图（mu地图）和双能CT（DECT）为511 keV photons.Methods：幻影测量上获得的全身混合PET/MRI系统，使用四通道只接收MR射频（RF）乳腺线圈。进行了两次采集：将体模放置在四通道RF乳腺线圈中，以及不使用乳腺线圈。使用三种不同的CT衍生硬件μ标测图校正乳房线圈的PET衰减：（a）单能量CT（SECT）、（B）DECT和（c）MVCT。每个衰减校正（AC）的PET体积进行了评估，并与没有乳房coil.Results：乳房线圈衰减PET光子10%的整体进行收购进行比较。将阈值应用于SECT μ图以减少金属伪影的影响，但过度校正发生在更高度衰减的区域。DECT衍生的虚拟单色图像减少了射束硬化伪影，但其他金属伪影仍然存在。尽管DECT图像中仍存在金属伪影，但它导致了衰减更严重区域的改善。MVCT图像似乎是免费的金属伪影，导致无伪影μ地图和进一步改善AC-PET images.Conclusions：我们的MVCT为基础的方法，用于创建磁共振射频线圈μ地图，大大减少了伪影产生的金属在SECT方法。这消除了对其他伪影减少方法的需要，包括应用窄波束衰减系数的阈值，或在使用千伏源成像之前拆卸硬件以去除高Z分量。(C)2017年美国医学物理学家协会
Purpose: The purpose of this study was to describe and evaluate methods for calculating a mega-voltage computed tomography (MVCT)-derived MR hardware attenuation map (mu-map) and dual-energy CT (DECT) for 511 keV photons.Methods: Phantom measurements were acquired on a whole-body hybrid PET/MRI system, using a four-channel receive-only MR radiofrequency (RF) breast coil. Two acquisitions were performed: with the phantoms positioned in the four-channel RF breast coil, and without the breast coil. PET attenuation from the breast coil was corrected using three different CT-derived hardware mu-maps: (a) Single-energy CT (SECT), (b) DECT, and (c) MVCT. Each attenuation-corrected (AC) PET volume was evaluated and compared with the acquisition performed without the breast coil.Results: The breast coil attenuated PET photons by 10% overall. Threshold values were applied to the SECT mu-map to reduce the effects of metal artifacts, but overcorrection occurred in more highly attenuated regions. The DECT-derived virtual monochromatic image reduced beam-hardening artifacts, but other metal artifacts remained. Despite the remaining metal artifacts in the DECT image, it led to an improvement in the more attenuated regions. The MVCT images appear to be free from metal artifacts leading to an artifact-free mu-map and a further improvement AC-PET images.Conclusions: Our MVCT-based approach for creating mu-maps for MR RF coils greatly reduces artifacts produced by metal in a SECT approach. This eliminates the need for other artifact reduction methods, including the application of a threshold of narrow beam attenuation coefficients, or disassembling hardware to remove high-Z components before imaging with a kilovoltage source. (C) 2017 American Association of Physicists in Medicine