Medical Physics, and.
Clinical Radiology, NHS Tayside, Ninewells Hospital and Medical School, Dundee, United Kingdom.
Invest Radiol. 2019 Mar;54(3):169-176. doi: 10.1097/RLI.0000000000000526.
The aim of this study was to examine the variation in signal intensity ratio (SIR) values in Eurospin gel phantoms and healthy volunteer (HV) brain images in response to different magnetic resonance imaging hardware and software settings.
Gel phantoms with T1 relaxation times similar to the dentate nucleus (DN), pons (P), globus palladus (GP), and thalamus (Th) were scanned using a T1-weighted 2-dimensional spin-echo sequence on 2 magnetic resonance imaging scanners (3 T and 1.5 T). Imaging was performed by sequentially altering selected magnetic resonance (MR) parameters relative to a default pulse sequence, and the protocol was implemented repeatedly over 3 months. The experiment was also repeated on a cohort of 15 young HVs. Calculations of DN/P and GP/Th SIR values were derived for the images of the gels (GelDN/P and GelGP/Th) and the HVs (HVDN/P and HVGP/Th).
For the default sequence, the mean SIR values of GelDN/P and GelGP/Th varied by ±2.20% and ±0.75%, respectively, when measured over multiple imaging sessions (3 T). Within a single imaging session, these variations were smaller (±0.17% for GelDN/P and ±0.15% for GelGP/Th). At 1.5 T, the equivalent SIR variations for GelDN/P were ±1.41% (multiple sessions) and ±0.41% (single session), and that for GelGP/Th were ±0.47% (multiple sessions) and ±0.33% (single session).Sequential changes to the MR sequence parameters resulted in gel SIR variations as follows: 14.07% ± 2.43% (with/without normalization filters), -7.80% ± 0.28% (different echo times, TE), and -5.06% ± 0.59% (selective activation of RF coil elements). The largest variations were noted when the gels were positioned below the scanner isocenter, where SIR measurements were different by 22%.For the HVs, the SIR values were found to be consistently within 0.64% (single session) for the default sequence. Sequential changes to the MR sequence parameters resulted in SIR variations of -24.47% ± 2.47% (with/without normalization filters), -15.32% ± 7.71% (different echo times, TE), and -2.90% ± 0.78% (selective activation of RF coil elements).
This study has demonstrated that SIR percentage changes from baseline of a similar magnitude to brain gadolinium contrast agent signal hyperintensities can be replicated in phantom models and HVs by altering common MR acquisition parameters and hardware.
本研究旨在探讨在不同磁共振成像（MRI）硬件和软件设置下，Eurospin 凝胶体模和健康志愿者（HV）脑图像的信号强度比（SIR）值的变化。
使用 T1 加权二维自旋回波序列在两台 MRI 扫描仪（3T 和 1.5T）上对 T1 弛豫时间与齿状核（DN）、脑桥（P）、苍白球（GP）和丘脑（Th）相似的凝胶体模进行扫描。通过相对于默认脉冲序列依次改变选定的磁共振（MR）参数进行成像，该方案在 3 个月内重复实施。该实验还在 15 名年轻 HV 中重复进行。为凝胶体模（GelDN/P 和 GelGP/Th）和 HV（HVDN/P 和 HVGP/Th）的图像计算了 DN/P 和 GP/Th SIR 值。
对于默认序列，在多次成像过程中（3T），GelDN/P 和 GelGP/Th 的平均 SIR 值变化分别为±2.20%和±0.75%。在单个成像过程中，这些变化较小（GelDN/P 为±0.17%，GelGP/Th 为±0.15%）。在 1.5T 下，GelDN/P 的等效 SIR 变化为±1.41%（多次扫描）和±0.41%（单次扫描），GelGP/Th 的变化为±0.47%（多次扫描）和±0.33%（单次扫描）。MR 序列参数的顺序变化导致凝胶体模 SIR 变化如下：14.07%±2.43%（有/无归一化滤波器），-7.80%±0.28%（不同回波时间，TE），-5.06%±0.59%（射频线圈元件的选择性激活）。当凝胶体模位于扫描仪等中心下方时，会观察到最大的变化，SIR 测量值相差 22%。对于 HV，发现在默认序列下，SIR 值始终在 0.64%（单次扫描）以内。MR 序列参数的顺序变化导致 SIR 变化为-24.47%±2.47%（有/无归一化滤波器），-15.32%±7.71%（不同回波时间，TE），-2.90%±0.78%（射频线圈元件的选择性激活）。
本研究表明，通过改变常见的 MRI 采集参数和硬件，在体模模型和 HV 中可以复制出与脑钆造影剂信号高信号相似的 SIR 百分比变化。
