MRI compatibility study of an integrated PET/RF-coil prototype system at 3T
MRI compatibility study of an integrated PET/RF-coil prototype system at 3T
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DOI：
10.1016/j.jmr.2017.08.010
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发表时间：
2017-10-01
影响因子：
2.2
通讯作者：
Yamaya, Taiga
中科院分区：
文献类型：
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作者：
Akram, Md Shahadat Hossain;Obata, Takayuki;Yamaya, Taiga
我们一直致力于为现有的磁共振成像（MRI）系统开发PET插入器，用于同时进行PET/MR成像，该系统集成了射频（RF）屏蔽PET检测器模块和射频头线圈。为了避免PET检测电路与不同MRI产生的电磁场之间的干扰，PET检测电路安装在8个铜屏蔽纤维增强塑料盒内，这8个屏蔽PET模块集成在直径270 mm、轴长280 mm的圆柱形鸟笼式射频线圈的8个元件之间，该线圈设计用于3-T临床MRI系统。轴向视场为12 mm的PET闪烁体直径变为255 mm，非常接近成像区域。在这项研究中，我们研究了这种PET/RF线圈集成系统对MRI性能的影响，包括评估静态场（Bo）不均匀性、RF场（B1）分布、局部比吸收率（SAR）分布、平均SAR和信噪比（SNR）。对于中心直径为170 mm、轴长为80 mm（总直径为200 mm、轴长为100 mm）的均匀圆柱形体，在中心和偏离中心的40 mm横向面上，Bo不均匀性最大增加了约31个百分点，在中心横向面上B1场不均匀性增加了5个百分点（未PET时为84%，有PET时为79%）。而在PET与射频头线圈集成后，沿冠状面B1均匀性几乎没有变化（77%）。平均SAR和最大局部SAR分别增加了1.21倍和1.62倍。然而，自旋回波和梯度回波序列的信噪比研究表明，由于屏蔽PET模块，信噪比分别降低了约70%和60%。总体结果证明了该集成PET/ rf线圈系统与现有MRI系统配合使用的可行性。(C) 2017爱思唯尔公司版权所有。
We have been working on the development of a PET insert for existing magnetic resonance imaging (MRI) systems for simultaneous PET/MR imaging, which integrates radiofrequency (RF)-shielded PET detector modules with an RF head coil. In order to avoid interferences between the PET detector circuits and the different MRI-generated electromagnetic fields, PET detector circuits were installed inside eight Cu-shielded fiber-reinforced plastic boxes, and these eight shielded PET modules were integrated in between the eight elements of a 270-mm-diameter and 280-mm-axial-length cylindrical birdcage RF coil, which was designed to be used with a 3-T clinical MRI system. The diameter of the PET scintillators with a 12-mm axial field-of-view became 255 mm, which was very close to the imaging region. In this study, we have investigated the effects of this PET/RF-coil integrated system on the performance of MRI, which include the evaluation of static field (Bo) inhomogeneity, RF field (B1) distribution, local specific absorption rate (SAR) distribution, average SAR, and signal-to-noise ratio (SNR). For the central 170-mm diameter and 80-mm-axial-length of a homogenous cylindrical phantom (with the total diameter of 200 mm and axial-length of 100 mm), an increase of about a maximum of 31ST in the Bo inhomogeneity was found, both in the central and 40-mm off-centered transverse planes, and a 5 percentage point increase of B1 field inhomogeneity was observed in the central transverse plane (from 84% without PET to 79% with PET), while B1 homogeneity along the coronal plane was almost unchanged (77%) following the integration of PET with the RF head coil. The average SAR and maximum local SAR were increased by 1.21 and 1.62 times, respectively. However, the SNR study for both spin-echo and gradient-echo sequences showed a reduction of about 70% and 60%, respectively, because of the shielded PET modules. The overall results prove the feasibility of this integrated PET/RF-coil system for using with the existing MRI system. (C) 2017 Elsevier Inc. All rights reserved.