Bardwell Speltz Lydia J, Kang Daehun, In Myung-Ho, Campeau Norbert G, Huston John, Trzasko Joshua D, Halverson Maria, Gray Erin, Warner David O, Bernstein Matt A, Shu Yunhong
Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA.
Med Phys. 2025 Aug;52(8):e18039. doi: 10.1002/mp.18039.
Flow-related ghost artifact from a 3D Magnetization Prepared Rapid Gradient Echo (MPRAGE) sequence results from unsaturated magnetization of incoming arterial flow. This is especially common on MR scanners equipped with smaller radiofrequency (RF) transmit coils. A high-performance compact 3T (C3T) scanner features a smaller RF-transmit coil (inner diameter 37 cm, length 40 cm), leading to a rapid fall-off of the B1 field below the neck. This configuration results in more intense flow-related ghost artifacts, especially in younger patients.
The C3T scanner's smaller RF-transmit coil provides RF field coverage over the brain region, causing bright in-flow arterial signals and flow-related artifacts in the conventional 3D-MPRAGE scans. The purpose of this study is to suppress these artifacts by adding a RF saturation band (RFSB) pulses to the 3D-MPRAGE sequence.
The RFSB was added to the 3D-MPRAGE sequence as a preparation pulse option. To test the effectiveness, 37 subjects were scanned on the C3T under an IRB-approved protocol using 3D-MPRAGE with and without RFSB. Ten of those subjects underwent repeated scans with and without RFSB to evaluate test-retest reliability. A consensus evaluation by two neuroradiologists was performed on all data to compare signal to noise ratio, image contrast, presence of artifacts, and diagnostic confidence. Quantitative analysis included calculating test-retest differences by image subtraction and evaluating the variance in flow-artifact-induced image intensity between the scans with and without RFSB. Additionally, one subject was scanned on a whole-body 3T scanner using a transmit/receive (T/R) head coil to demonstrate the method's applicability across different MRI platforms as a proof of concept.
The Wilcoxon signed-rank test of the neuroradiologist evaluations showed a significant reduction in artifacts and an improvement in diagnostic confidence in the posterior fossa region with and without RFSB (p < 0.0001). Test-retest analysis showed that adding RFSB significantly reduced image intensity variability in the cerebellum, even among subjects without visible flow artifacts. The normalized difference decreased from 8.71% to 6.41% (p = 0.0059), suggesting improved image reliability in regions prone to flow-related artifacts. Additionally, similar findings were observed in scans on a whole-body 3T with a T/R head coil, demonstrating the broader applicability of this method.
Incorporating RFSB into 3D-MPRAGE scans effectively reduces flow-related ghost artifact on the C3T scanner, improving image quality and diagnostic confidence. These findings suggest that the proposed method could be widely implemented across MRI systems utilizing a smaller RF-transmit coil.
三维磁化准备快速梯度回波（MPRAGE）序列中与血流相关的鬼影伪影是由流入动脉血的未饱和磁化引起的。这在配备较小射频（RF）发射线圈的磁共振成像（MR）扫描仪上尤为常见。一台高性能紧凑型3T（C3T）扫描仪具有较小的RF发射线圈（内径37厘米，长度40厘米），导致颈部以下B1场迅速衰减。这种配置会导致更强烈的与血流相关的鬼影伪影，尤其是在年轻患者中。
C3T扫描仪较小的RF发射线圈可覆盖脑部区域，在传统的三维MPRAGE扫描中会产生明亮的流入动脉信号和与血流相关的伪影。本研究的目的是通过在三维MPRAGE序列中添加射频饱和带（RFSB）脉冲来抑制这些伪影。
将RFSB作为准备脉冲选项添加到三维MPRAGE序列中。为测试其有效性，根据机构审查委员会（IRB）批准的方案，对37名受试者在C3T扫描仪上使用有和没有RFSB的三维MPRAGE进行扫描。其中10名受试者在有和没有RFSB的情况下进行了重复扫描，以评估重测可靠性。由两名神经放射科医生对所有数据进行一致性评估，以比较信噪比、图像对比度、伪影的存在情况和诊断置信度。定量分析包括通过图像相减计算重测差异，并评估有和没有RFSB的扫描之间血流伪影引起的图像强度方差。此外，对一名受试者使用发射/接收（T/R）头部线圈在全身3T扫描仪上进行扫描，以证明该方法作为概念验证在不同MRI平台上的适用性。
神经放射科医生评估的Wilcoxon符号秩检验显示，无论有无RFSB，后颅窝区域的伪影均显著减少，诊断置信度有所提高（p < 0.0001）。重测分析表明，添加RFSB可显著降低小脑的图像强度变异性，即使在没有可见血流伪影的受试者中也是如此。归一化差异从8.71%降至6.41%（p = 0.0059），表明在容易出现与血流相关伪影的区域，图像可靠性有所提高。此外，在使用T/R头部线圈的全身3T扫描中也观察到了类似的结果，证明了该方法具有更广泛的适用性。
在三维MPRAGE扫描中加入RFSB可有效减少C3T扫描仪上与血流相关的鬼影伪影，提高图像质量和诊断置信度。这些发现表明，所提出的方法可在使用较小RF发射线圈的MRI系统中广泛应用。
