Impact of Magnetic Field Inhomogeneity on the Quality of Magnetic Resonance Images and Compensation Techniques: A Review

Figures & data

Table 1 Summary of Data Extracted from Some Articles

Author	Year	Journal/Publisher	Country	Aim	Results
Blasche et al^Citation1	2017	Siemens Health care GmbH	Germany	Magnet homogeneity and shimming capabilities were the main topics of discussion.	The use of a coil shim and slice adjustment improves the local field homogeneity.
Walker et al^Citation5	2014	Australasian physical and engineering sciences in medicine	Australia	Assessing variations in the geometric distortion in radiotherapy treatment planning	Increasing the bandwidth of the acquisition sequence decreased the amount of distortion. Slice thickness and phase encoding direction can influence image distortion
Drew & Murphy^Citation9	2018	Radiopaedia.org	Not mentioned	Optimization of magnetic field homogeneity	Individual or patient-by-patient homogeneity must be optimized by “shimming” the magnetic field
Wachowicz^Citation7	2014	Research and Reports in Nuclear Medicine	Canada	Focus on current developments and research directions on shimming techniques for brain imaging	Local field distortions could be reduced with multi-coil shim arrays
Cho et al^Citation6	1998	Medical physics	Korea	To determine how to eliminate artifacts caused by chemical shift, susceptibility, and static field inhomogeneity	The addition of a compensation gradient with the same amplitudes as the slice selection gradient can compensate for magnetic field inhomogeneity and chemical shift.
Koch et al^Citation8	2009	Progress in nuclear magnetic resonance spectroscopy	USA	To discuss high-field B0 shimming within small rodents and the human brain.	Dynamic shim updating, local shim coil application, and subject-specific passive shimming could all help to increase B0 homogeneity.
Och et al^Citation10	1992	Medical physics	USA	To propose and specify aspects that could be included in magnetic resonance imaging device acceptance testing	Image quality in MRI could be improve by evaluating the following; RF coils, Bo field homogeneity, Gradient field strength, Eddy current, SNR, radiographic output, geometrical distortion, slice thickness, image processing software
Frollo et al^Citation11	2018	IEEE Transactions on Magnetics	Slovakia	To compare magnetic field measurements of three methods (ie, Hall effect, NMR magnetometer, and imaging) in order to optimize the MR imager’s homogeneity	The imaging measuring method produced the best results of MR homogeneity.
Bley et al^Citation12	2010	Journal of Magnetic Resonance Imaging	USA	To review the fat suppression and fat–water imaging strategies	Chemically selective, Spatial-spectral pulse, STIR imaging, and nonuniform spectral response fat suppression methods are all useful in fat suppression and fat–water imaging strategies. The choice of fat suppression and water imaging strategies depends on the imaging scenario.
Mangrum et al^Citation13	2018	Case Review Series E-Book. Elsevier Health Sciences	USA	Case review series of MRI Physics
Geraldes & Lauren^Citation20	2009	Contrast media and molecular imaging	Portugal	To classify currently available contrast agents according to their effects on the MRI image using a combination of various related criteria.	The presence of Gd^3+ chelates in clinical MRI contrast agents gives physiological information that is important to the very high anatomical resolution of this imaging modality.
Juchem and Graaf^Citation14	2017	Analytical biochemistry	USA	To discuss the relevance of B0 homogeneity for in vivo MRS	The optimum B0 shimming method relies on the MR application for which it is used, and selecting one is a difficult task since several parameters must be addressed, including the species and region dependency of apparent magnetic field distortions, as well as the required level of field homogeneity.
Chang and Kamel^Citation15	2014	Applied Radiology	USA	Discuss the theoretical advantages of imaging at larger field strengths against 1.5T systems, as well as current body MRI imaging standards.	Chemical shift artifacts, magnetic and RF field inhomogeneities, and standing wave or dielectric shading artifacts are all critical considerations at 3T for abdominal imaging, and when used properly, they can improve image quality dramatically.
Yang et al^Citation17	2004	Magnetic Resonance in Medicine	Pennsylvania	To validate the theoretical analysis, experimental results of artifact reductions with SENSE, GESEPI, and SENSE-GESEPI in echo-planar imaging	In terms of artifact reduction, the SENSE and GESEPI approaches are complementary. When these two strategies are combined, a method is created that can reduce all three forms of EPI artifacts while retaining a fast acquisition time.
Bitar^Citation23	2006	Radiographics	Canada	To assist radiologists, understand the physical basis of the MR pulse sequences most commonly used in routine clinical imaging	There are just two basic types of magnetic resonance pulse sequences. Knowledge of MRI pulse sequences (SE and GRE) is required to aid radiologists in detecting sources and types of MRI artifacts, as well as to help clinical decision-making.
Cornfeld and Weinreb^Citation24	2008	American Journal of Roentgenology	USA	To demonstrate how understanding the differences between 3 and 1.5 T may be utilized to influence changes in normal 1.5-T techniques to create 3 T abdominal and pelvic images of high quality.	Susceptibility artifacts might be reduced by employing a greater receiver bandwidth with a shorter TE, whereas dielectric artifacts could be compensated for with a dielectric pad. Avoiding extending the echo-train length, decreasing the receiver bandwidth, and positioning the frequency direction in the anteroposterior direction can all improve image quality in the pelvis.
Wald and Polimeni^Citation36	2015	Academic Press	USA	To discuss high-speed, high-resolution acquisitions	Susceptibility gradient image distortions are a fundamental impediment to high-spatial-resolution single-shot EPI. The use of small loop coils could be effective in shimming small localized areas.
Hood et al^Citation38	1999	Radiographics	USA	To discuss basic principles of chemical shift and their relevance for clinical imaging	A chemical shift can help in the diagnosis of lipid-containing brain and body lesions. Suppression techniques such as STIR and fat saturation pulses can limit the signal from fat that causes artifacts
Delfaut et al^Citation39	1999	Radiographics		To discuss various techniques of fat suppression	Fat saturation, inversion recovery imaging, and opposing phased encoding are three strategies for fat suppression.
Khurram and Wael^Citation40	2020	Academic Press	UK	To discuss advances in MRI	Parallel imaging can shorten scan times, but it can also cause signal loss, which can be compensated for by using higher field strength (eg, 3.0 T) scanners’ that yield greater SNR and improve image quality

Figure 1 A 32-year-old male with several cavernous malformations who was being evaluated for intraparenchymal hemorrhage. (A) A left frontal cavernous malformation is visible on a T2-weighted image, and it is encircled by a significant haemosiderin ring. (B) Multiple punctate hypointense foci can be seen on the GE T₂*-weighted image, which are representative of tiny cavernous malformations in both hemispheres (arrows).¹⁸

Note: Reproduced from Gasparotti R, Pinelli L, Liserre R. New MR sequences in daily practice: susceptibility weighted imaging. A pictorial essay. Insights into imaging. 2011 Jun;2(3):335-47.

Figure 2 With increasing TE, T₂* weighting rises. This is so that more dephasing can occur prior to the development of an echo when the TE is longer. (A) TE = 10ms, (B) TE = 30ms, (C) TE = 50ms [Courtesy Allen D Elster, MRIQuestions.com].¹⁹

Figure 3 Iron-particle-related susceptibility artifact in mascara indicated by yellow solid arrow [Courtesy Allen D Elster, MRIQuestions.com].²¹

Figure 4 Chemical Shift artifact in the spine. At the junction between the vertebrae and the disk, there are a series of light and dark bands (indicated by solid red arrows) [Courtesy Allen D Elster, MRIQuestions.com].²²

Figure 5 At the water-fat interface, there is a chemical shift artifact. The axial T₁-weighted GRE MR image shows a dark rim on one border of the kidney and a bright rim on the opposite edge (indicated by white solid arrows), an artifact caused by the difference in fat and water precessional frequencies [Courtesy Allen D Elster, MRIQuestions.com].²²

Figure 6 Chemical Shift Artifact: The bandwidth per pixel in the phase-encode direction of EPI is very tiny (i.e., on the order of 1kHz). This narrow bandwidth in the phase-encode direction translates into a significant artifact (indicated by the solid yellow arrows) that can be up to 1 cm wide at 1.5 T, where the fat/water chemical shift is around 220 Hz [Courtesy Allen D Elster, MRIQuestions.com].²⁶

Figure 7 Phase cancellation chemical shift artifact indicated by solid yellow arrows of the abdomen. This form of chemical shift artifact occurs exclusively in gradient echo imaging [Courtesy Allen D Elster, MRIQuestions.com].²⁷

Figure 8 Effects of dielectric pads on 3T pelvic MRI artifact reduction. The solid red arrow in (A) depicts a signal dropout in the absence of a dielectric pad. (B) Signal is enhanced by the use of a dielectric pad [Courtesy Allen D Elster, MRIQuestions.com].³⁷

Blasche M, Fischer D, Healthineers. Magnet Homogeneity and Shimming. In: Siemens Healthineers. Siemens Healthcare GmbH; 2017. Available from: https://cdn0.scrvt.com/39b415fb07de4d9656c7b516d8e2d907/1800000003946047/b36c69893983/mreadings_mr-in-rt_3rd-edition_magnet-homogeneity-and-shimming_blasche_v2_1800000003946047.pdf. Accessed October 30, 2021.

 Google Scholar

Walker A, Liney G, Metcalfe P, Holloway L. MRI distortion: considerations for MRI-based radiotherapy treatment planning. Australas Phys Eng Sci Med. 2014;37(1):103–113. doi:10.1007/s13246-014-0252-2

 PubMed Web of Science ®Google Scholar

Drew Z, Murphy A. Magnetic field homogeneity. Reference article, Radiopaedia.org; 2018. Available from: https://radiopaedia.org/articles/magnetic-field-homogeneity. Accessed on November 19, 2021.

 Google Scholar

Wachowicz K. Evaluation of active and passive shimming in magnetic resonance imaging. Res Rep Nucl Med. 2014;4:1–12. doi:10.2147/RRNM.S46526

 Google Scholar

Cho ZH, Kim DJ, Kim YK. Total inhomogeneity correction including chemical shifts and susceptibility by view angle tilting. Med Phys. 1998;15(1):7–11. doi:10.1118/1.596162

 Web of Science ®Google Scholar

Koch KM, Rothman DL, de Graaf RA. Optimization of static magnetic field homogeneity in the human and animal brain in vivo. Prog Nucl Magn Reson Spectrosc. 2009;54(2):69. doi:10.1016/j.pnmrs.2008.04.001

 Web of Science ®Google Scholar

Och JG, Clarke GD, Sobol WT, Rosen CW, Mun SK. Acceptance testing of magnetic resonance imaging systems: report of AAPM nuclear magnetic resonance task group No. 6. Med Phys. 1992;19(1):217–229. doi:10.1118/1.596903

 Web of Science ®Google Scholar

Frollo I, Andris P, Krafčík A, Gogola D, Dermek T. Magnetic field homogeneity adjustment for magnetic resonance imaging equipment. IEEE Trans Magn. 2018;54(5):1–9. doi:10.1109/TMAG.2018.2804352

 Web of Science ®Google Scholar

Bley TA, Wieben O, François CJ, Brittain JH, Reeder SB. Fat and water magnetic resonance imaging. J Magn Reson Imaging. 2010;31(1):4–18. doi:10.1002/jmri.21895

 Web of Science ®Google Scholar

Mangrum W, Hoang QB, Amrhein TJ, et al. Duke Review of MRI Principles: Case Review Series E-Book. Elsevier Health Sciences; 2018.

 Google Scholar

Geraldes CF, Laurent S. Classification and basic properties of contrast agents for magnetic resonance imaging. Contrast Media Mol Imaging. 330 2009;4(1):1–23. doi:10.1002/cmmi.265

 Google Scholar

Juchem C, de Graaf RA. Bo magnetic field homogeneity and shimming for in vivo magnetic resonance spectroscopy. Anal Biochem. 2017;529:17–29. doi:10.1016/j.ab.2016.06.003

 Web of Science ®Google Scholar

Chang KJ, Kamel IR. Abdominal imaging at 3T: challenges and solutions. Appl Radiol. 2010;39(10):22. doi:10.37549/AR1773

 Google Scholar

Yang QX, Wang J, Smith MB, et al. Reduction of magnetic field inhomogeneity artifacts in echo-planar imaging with SENSE and GESEPI at high field. Magn Reson Med. 2004;52(6):1418–1423. doi:10.1002/mrm.20303

 Web of Science ®Google Scholar

Bitar R, Leung G, Perng R, et al. MR pulse sequences: what every radiologist wants to know but is afraid to ask. Radiographics. 2006;26(2):513–537. doi:10.1148/rg.262055063

 PubMed Web of Science ®Google Scholar

Cornfeld D, Weinreb J. Simple changes to 1.5-T MRI abdomen and pelvis protocols to optimize results at 3 T. American Journal of Roentgenology, 2008;190(2), W140–W150.

 Google Scholar

Wald LL, Polimeni JR. High-Speed, High-Resolution Acquisitions. Brain Mapping, an Encyclopedic Reference. San Diego, CA: Academic Press; 2015. 103–116. doi:10.1016/b978-0-12-397025-1

 Google Scholar

Hood MN, Ho VB, Smirniotopoulos JG, Szumowski J. Chemical shift: the artifact and clinical tool revisited. Radiographics. 1999;19(2):357–371. doi:10.1148/radiographics.19.2.g99mr07357

 Web of Science ®Google Scholar

Delfaut EM, Beltran J, Johnson G, Rousseau J, Marchandise X, Cotten A. Fat suppression in MR imaging: techniques and pitfalls. Radiographics. 1999;19(2):373–382. doi:10.1148/radiographics.19.2.g99mr03373

 Web of Science ®Google Scholar

Khurram S, Wael M. Advances in magnetic resonance imaging (MRI). In: Advances in Medical and Surgical Engineering. Academic Press; 2020: 121–142. ISBN 9780128197127. doi:10.1016/B978-0-12-819712-7.00009-7

 Google Scholar

Gasparotti R, Pinelli L, Liserre R. New MR sequences in daily practice: susceptibility weighted imaging. A pictorial essay. Insights into imaging. 2011 Jun;2(3):335–47.

 Google Scholar

Elster AD, Spoiled-GRE: Image Contrast. MRIQuestions.com; 2021. Available from: https://mriquestions.com/spoiled-gre-parameters.html. Accessed August 19, 2022.

 Google Scholar

Elster AD, Susceptibility artifact. MRIQuestions.com; 2021. Available from: https://www.mriquestions.com/susceptibility-artifact.html. Accessed August 20, 2022.

 Google Scholar

Elster AD, Chemical shift Artifact. MRIQuestions.com; 2021. Available from: https://mriquestions.com/chemical-shift-artifact.html. Accessed August 18, 2022.

 Google Scholar

Elster AD, Chemical Shift: Phase Effects. MRIQuestions.com; 2021. Available from: https://mriquestions.com/chemical-shift-in-phase.html. Accessed August 18, 2022.

 Google Scholar

Elster AD, Chemical Shift: 2nd Kind. MRIQuestions.com; 2021. Available from: https://mriquestions.com/chemical-shift-2nd-kind.html. Accessed August 20, 2022.

 Google Scholar

Elster AD, Dielectric Pads. MRIQuestions.com; 2021. Available from: https://mriquestions.com/dielectric-pads.html. Accessed August 20, 2022.

 Google Scholar