Reed Galen D, Ma Junjie, Park Jae Mo, Schulte Rolf F, Harrison Crystal E, Chen Albert P, Pena Salvador, Baxter Jeannie, Derner Kelly, Tai Maida, Raza Jaffar, Liticker Jeff, Hall Ronald G, Dean Sherry A, Zaha Vlad G, Malloy Craig R
GE Healthcare, Dallas, TX, USA.
Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, USA.
Magn Reson Med. 2021 Jul;86(1):157-166. doi: 10.1002/mrm.28691. Epub 2021 Feb 5.
This study aimed to investigate the role of regional inhomogeneity in spiral hyperpolarized C image quality and to develop measures to alleviate these effects.
Field map correction of hyperpolarized C cardiac imaging using spiral readouts was evaluated in healthy subjects. Spiral readouts with differing duration (26 and 45 ms) but similar resolution were compared with respect to off-resonance performance and image quality. An map-based image correction based on the multifrequency interpolation (MFI) method was implemented and compared to correction using a global frequency shift alone. Estimation of an unknown frequency shift was performed by maximizing a sharpness objective based on the Sobel variance. The apparent full width half at maximum (FWHM) of the myocardial wall on [ C]bicarbonate was used to estimate blur.
Mean myocardial wall FWHM measurements were unchanged with the short readout pre-correction (14.1 ± 2.9 mm) and post-MFI correction (14.1 ± 3.4 mm), but significantly decreased in the long waveform (20.6 ± 6.6 mm uncorrected, 17.7 ± 7.0 corrected, P = .007). Bicarbonate signal-to-noise ratio (SNR) of the images acquired with the long waveform were increased by 1.4 ± 0.3 compared to those acquired with the short waveform (predicted 1.32). Improvement of image quality was observed for all metabolites with correction.
-map correction reduced blur and recovered signal from dropouts, particularly along the posterior myocardial wall. The low image SNR of [ C]bicarbonate can be compensated with longer duration readouts but at the expense of increased artifacts, which can be partially corrected for with the proposed methods.
本研究旨在探讨区域不均匀性在螺旋超极化碳-13（¹³C）成像质量中的作用，并制定减轻这些影响的措施。
在健康受试者中评估使用螺旋读出的超极化¹³C心脏成像的场图校正。比较了具有不同持续时间（26和45毫秒）但分辨率相似的螺旋读出在失谐性能和图像质量方面的差异。实施了基于多频插值（MFI）方法的基于¹³C图的图像校正，并与仅使用全局频移校正进行比较。通过基于Sobel方差最大化锐度目标来估计未知频移。使用[¹³C]碳酸氢盐上心肌壁的表观半高全宽（FWHM）来估计模糊度。
短读出预校正（14.1±2.9毫米）和MFI校正后（14.1±3.4毫米）心肌壁平均FWHM测量值不变，但长波形中显著降低（未校正为20.6±6.6毫米，校正后为17.7±7.0毫米，P = 0.007）。与短波形采集的图像相比，长波形采集的图像中碳酸氢盐的信噪比（SNR）提高了1.4±0.3（预测为1.32）。校正后所有代谢物的图像质量均有改善。
¹³C图校正减少了模糊度并从信号丢失中恢复了信号，特别是沿心肌后壁。[¹³C]碳酸氢盐的低图像SNR可以通过更长持续时间的读出进行补偿，但代价是增加了¹³C伪影，所提出的方法可以部分校正这些伪影。
