Image-based gradient non-linearity characterization to determine higher-order spherical harmonic coefficients for improved spatial position accuracy in magnetic resonance imaging

被引：19

作者：

Weavers, Paul T. ^{[1
]}

Tao, Shengzhen ^{[1
,2
]}

Trzasko, Joshua D. ^{[1
]}

Shu, Yunhong ^{[1
]}

Tryggestad, Erik J. ^{[3
]}

Gunter, Jeffrey L. ^{[1
]}

McGee, Kiaran P. ^{[1
]}

Litwiller, Daniel V. ^{[4
]}

Hwang, Ken-Pin ^{[5
]}

Bernstein, Matt A. ^{[1
]}

机构：

[1] Mayo Clin, Radiol, 200 First St Southwest, Rochester, MN 55905 USA

[2] Mayo Clin, Mayo Grad Sch, 200 First St Southwest, Rochester, MN 55905 USA

[3] Mayo Clin, Radiat Oncol, 200 First St Southwest, Rochester, MN 55905 USA

[4] GE Heathcare, 3200 N Grandview Blvd, Waukesha, WI 53188 USA

[5] Univ Texas MD Anderson Canc Ctr, 1515 Holcomb Blvd, Houston, TX 77030 USA

来源：

MAGNETIC RESONANCE IMAGING | 2017年 / 38卷

基金：

美国国家卫生研究院;

关键词：

MRI; Treatment planning; Gradient non-linearity; Calibration; RADIATION ONCOLOGY; MRI SCANNER; DISTORTION; PHANTOM; BRAIN; FSL;

D O I：

10.1016/j.mri.2016.12.020

中图分类号：

R8 [特种医学]; R445 [影像诊断学];

学科分类号：

1002 ; 100207 ; 1009 ;

摘要：

Purpose: Spatial position accuracy in magnetic resonance imaging (MRI) is an important concern for a variety of applications, including radiation therapy planning, surgical planning, and longitudinal studies of morphologic changes to study neurodegenerative diseases. Spatial accuracy is strongly influenced by gradient linearity. This work presents a method for characterizing the gradient non-linearity fields on a per-system basis, and using this information to provide improved and higher-order (9th vs. 5th) spherical harmonic coefficients for better spatial accuracy in MRI. Methods: A large fiducial phantom containing 5229 water-filled spheres in a grid pattern is scanned with the MR system, and the positions all the fiducials are measured and compared to the corresponding ground truth fiducial positions as reported from a computed tomography (CT) scan of the object. Systematic errors from off-resonance (i.e., BO) effects are minimized with the use of increased receiver bandwidth (+/- 125 kHz) and two acquisitions with reversed readout gradient polarity. The spherical harmonic coefficients are estimated using an iterative process, and can be subsequently used to correct for gradient non-linearity. Test-retest stability was assessed with five repeated measurements on a single scanner, and cross-scanner variation on four different, identically-configured 3 T wide-bore systems. Results: A decrease in the root-mean-square error (RMSE) over a 50 cm diameter spherical volume from 1.80 mm to 0.77 mm is reported here in the case of replacing the vendor's standard 5th order spherical harmonic coefficients with custom fitted 9th order coefficients, and from 1.5 mm to 1 mm by extending custom fitted 5th order correction to the 9th order. Minimum RMSE varied between scanners, but was stable with repeated measurements in the same scanner. Conclusions: The results suggest that the proposed methods may be used on a per-system basis to more accurately calibrate MR gradient non-linearity coefficients when compared to vendor standard corrections. (C) 2016 Elsevier Inc. All rights reserved.

引用

页码：54 / 62

页数：9