Objective

Inversion recovery-pointwise encoding time reduction with radial acquisition (IR-PETRA) is an effective magnetic resonance (MR) pulse sequence in generating pseudo-CTs. The hardware-related spatial-distortion (HRSD) in MR images potentially deteriorates the accuracy of pseudo-CTs. Thus, we aimed at characterizing HRSD for IR-PETRA.

Materials and methods

gross-HRSD_overall (Euclidean-sum of gross-HRSD_i (i = x, y, z)) for IR-PETRA was assessed using a brain-specific phantom for two MR scanners (1.5 T-Aera and 3.0 T-Prisma). Moreover, hardware imperfections were analyzed by determining gradient-nonlinearity spatial-distortion (GNSD) and B₀-inhomogeneity spatial-distortion (B₀ISD) for magnetization-prepared rapid acquisition gradient-echo (MP-RAGE) which has well-known distortion characteristics.

Results

In 3.0 T, maximum of gross-GNSD_overall (Euclidean-sum of gross-GNSD_i) and gross-B₀ISD for MP-RAGE was 2.77 mm and 0.57 mm, respectively. For this scanner, the mean and maximum of gross-HRSD_overall for IR-PETRA were 0.63 ± 0.38 mm and 1.91 mm, respectively. In 1.5 T, maximum of gross-GNSD_overall and gross-B₀ISD for MP-RAGE was 3.41 mm and 0.78 mm, respectively. The mean and maximum of gross-HRSD_overall for IR-PETRA were 1.02 ± 0.50 mm and 3.12 mm, respectively.

Discussion

The spatial accuracy of MR images, besides being impacted by hardware performance, scanner capabilities, and imaging parameters, is mainly affected by its imaging strategy and data acquisition scheme. In 3.0 T, even without applying vendor correction algorithms, spatial accuracy of IR-PETRA image is sufficient for generating pseudo-CTs. In 1.5 T, distortion-correction is required to provide this accuracy.

中文翻译：

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使用大脑特定体模表征 IR-PETRA 脉冲序列的硬件相关空间失真。

客观的

逆向恢复逐点编码时间减少与径向采集 (IR-PETRA) 是生成伪 CT 的有效磁共振 (MR) 脉冲序列。MR 图像中与硬件相关的空间失真 (HRSD) 可能会降低伪 CT 的准确性。因此，我们旨在表征 IR-PETRA 的 HRSD。

材料和方法

毛-HRSD_整体（欧几里得-总和毛-HRSD_我（我 =  X，ÿ，Ž）），用于IR-PETRA是使用脑特异性幻象评估二个MR扫描器（1.5 T-海爱瑞和3.0 T-Prisma的） . 此外，通过确定具有众所周知失真的磁化准备快速采集梯度回波 (MP-RAGE) 的梯度非线性空间失真 (GNSD) 和 B ₀不均匀空间失真 (B ₀ ISD) 来分析硬件缺陷特征。

结果

在3.0 T，最大的毛- GNSD_整体（毛-GNSD的欧几里德求和_我和）毛-乙₀ ISD为MP-RAGE分别2.77毫米和0.57毫米。对于此扫描器，平均和最大的毛- HRSD_整体为IR-PETRA分别为0.63±0.38毫米，1.91毫米。在1.5 T，最大的毛- GNSD_整体和毛-乙₀ ISD为MP-RAGE分别3.41毫米和0.78毫米。的平均值和最大毛- HRSD_整体为IR-PETRA分别为1.02±0.50毫米，3.12毫米。

讨论

MR图像的空间精度除了受硬件性能、扫描仪能力和成像参数的影响外，主要受其成像策略和数据采集方案的影响。在 3.0 T 中，即使不应用供应商校正算法，IR-PETRA 图像的空间精度也足以生成伪 CT。在 1.5 T 中，需要失真校正来提供此精度。