Leah A Gilligan1, Jonathan R Dillman1,2, Jean A Tkach1, Andrew T Trout3,4. 1. Department of Radiology, MLC 5031, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH, 45229, USA. 2. Department of Radiology, University of Cincinnati College of Medicine, Cincinnati, OH, USA. 3. Department of Radiology, MLC 5031, Cincinnati Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH, 45229, USA. andrew.trout@cchmc.org. 4. Department of Radiology, University of Cincinnati College of Medicine, Cincinnati, OH, USA. andrew.trout@cchmc.org.
Abstract
PURPOSE: Acquired over a breath hold, multi-echo Dixon (mDixon) magnetic resonance imaging (MRI) of the liver can be used to quantify proton density fat fraction (PDFF) and iron-related signal decay. However, young, obese, and co-morbid patients may have limited breath holding capacity and could benefit from a motion-robust mDixon acquisition. The purpose of this study was to compare hepatic PDFF and R2* values between navigator-gated and breath-held mDixon MRI acquisition techniques in children and young adults with suspected liver disease. MATERIALS AND METHODS: This retrospective study was institutional review board-approved with a waiver of informed consent. Patients who underwent liver MRI with breath-held and navigator-gated mDixon sequences between January 2017 and July 2018 were included. One reviewer, blinded to sequence, measured PDFF and R2* on four images from each sequence. Another blinded reviewer graded respiratory motion (5-point Likert scale). Pearson correlation (r), Lin's concordance coefficients (rc), and Bland-Altman analyses were used to assess agreement between techniques. Frequency of clinically limiting motion (score ≥ 3) was compared with Fisher's exact test. RESULTS: Forty-two patients were included (15 female, 27 male; mean age: 15.7 ± 4.6 years). Mean PDFF and R2* were 16.6 ± 13.1% and 29.3 ± 4.7 s-1 (breath-held) versus 17.0 ± 13.2% and 29.6 ± 5.2 s-1 (navigator-gated). PDFF agreed almost perfectly between sequences (rc = 0.997, 95% CI 0.994-0.998; mean bias: 0.3%; 95% limits of agreement: - 2.4 to +1.7%), while R2* values correlated very strongly but with poor agreement (r = 0.837, rc = 0.832, 95% CI 0.716-0.910). Navigator-gated images exhibited significantly higher frequency of clinically limiting respiratory motion (88% vs. 48%, p = 0.0001). CONCLUSION: Despite greater respiratory motion artifact, a free-breathing navigator-gated mDixon sequence produces PDFF values with almost perfect agreement to a breath-held sequence.
PURPOSE: Acquired over a breath hold, multi-echo Dixon (mDixon) magnetic resonance imaging (MRI) of the liver can be used to quantify proton density fat fraction (PDFF) and iron-related signal decay. However, young, obese, and co-morbid patients may have limited breath holding capacity and could benefit from a motion-robust mDixon acquisition. The purpose of this study was to compare hepatic PDFF and R2* values between navigator-gated and breath-held mDixon MRI acquisition techniques in children and young adults with suspected liver disease. MATERIALS AND METHODS: This retrospective study was institutional review board-approved with a waiver of informed consent. Patients who underwent liver MRI with breath-held and navigator-gated mDixon sequences between January 2017 and July 2018 were included. One reviewer, blinded to sequence, measured PDFF and R2* on four images from each sequence. Another blinded reviewer graded respiratory motion (5-point Likert scale). Pearson correlation (r), Lin's concordance coefficients (rc), and Bland-Altman analyses were used to assess agreement between techniques. Frequency of clinically limiting motion (score ≥ 3) was compared with Fisher's exact test. RESULTS: Forty-two patients were included (15 female, 27 male; mean age: 15.7 ± 4.6 years). Mean PDFF and R2* were 16.6 ± 13.1% and 29.3 ± 4.7 s-1 (breath-held) versus 17.0 ± 13.2% and 29.6 ± 5.2 s-1 (navigator-gated). PDFF agreed almost perfectly between sequences (rc = 0.997, 95% CI 0.994-0.998; mean bias: 0.3%; 95% limits of agreement: - 2.4 to +1.7%), while R2* values correlated very strongly but with poor agreement (r = 0.837, rc = 0.832, 95% CI 0.716-0.910). Navigator-gated images exhibited significantly higher frequency of clinically limiting respiratory motion (88% vs. 48%, p = 0.0001). CONCLUSION: Despite greater respiratory motion artifact, a free-breathing navigator-gated mDixon sequence produces PDFF values with almost perfect agreement to a breath-held sequence.