Abstract
Purpose
Magnetic resonance imaging (MRI) techniques are increasingly used to quantify and monitor liver tissue characteristics including fat fraction, stiffness, and liver volume. The purpose of this study was to assess the inter-relationships between multiple quantitative liver metrics and patient-specific factors in a large pediatric cohort with known or suspected fatty liver disease.
Materials and methods
In this IRB-approved, HIPAA-compliant study, we retrospectively reviewed patient data and quantitative liver MRI results in children with known/suspected fatty liver disease. Relationships between liver MRI tissue characteristics and patient variables [sex, age, body mass index (BMI), diabetic status (no diabetes mellitus, insulin resistance/“prediabetes” diagnosis, or confirmed diabetes mellitus), and serum alanine transaminase (ALT)] were assessed using linear mixed models.
Results
294 quantitative liver MRI examinations were performed in 202 patients [128/202 (63.4%) boys], with a mean age of 13.4 ± 2.9 years. Based on linear mixed models, liver fat fraction was influenced by age (−0.71%/+1 year, p = 0.0002), liver volume (+0.006%/+1 mL, p < 0.0001), liver stiffness (−2.80%/+1 kPa, p = 0.0006), and serum ALT (+0.02%/+1 U/L, p = 0.0019). Liver stiffness was influenced by liver volume (+0.0003 kPa/+1 mL, p = 0.001), fat fraction (−0.02 kPa/+1% fat, p = 0.0006), and ALT (0.002 kPa/+1 U/L, p = 0.0002). Liver volume was influenced by sex (−262.1 mL for girls, p = 0.0003), age (+51.8 mL/+1 year, p = 0.0001), BMI (+49.1 mL/+1 kg/m2, p < 0.0001), fat fraction (+30.5 mL/+1% fat, p < 0.0001), stiffness (+192.6 mL/+1 kPa, p = 0.001), and diabetic status (+518.94 mL for diabetics, p = 0.0009).
Conclusions
Liver volume, fat fraction, and stiffness are inter-related and associated with multiple patient-specific factors. These relationships warrant further study as MRI is increasingly used as a non-invasive biomarker for fatty liver disease diagnosis and monitoring.
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Conflict of interest
Joshi—none, Dillman—unrelated grant funding (Siemens Medical Solutions USA, Toshiba America Medical Systems, Guerbet Group), Singh—none, Serai—None, Towbin—unrelated grant funding (Siemens Medical Solutions USA, Guerbet Group), consultant (Applied Radiology), and royalties (Elsevier), Xanthakos—none, Zhang—none, Shu—none, Trout—unrelated grant funding (Siemens Medical Solutions USA, Toshiba America Medical Systems), consultant (American College of Radiology), and royalties (Elsevier).
Ethical approval
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. As this study was retrospective and involved analysis of existing data, the requirement for informed consent was waived by our institutional review board.
Appendices
Appendix 1
MR sequence parameters for fat fraction sequence on Philips and GE 1.5T MRI scanners.
Scanner | Philips Ingenia | Philips Ingenia | GE HDx |
---|---|---|---|
Technique | mDixon quant | Chemical shift encoded with lipid bag | Chemical shift encoded with lipid bag |
Pulse sequence | 3D GRE | 3D GRE | 3D GRE |
Matrix | 160 × 140 | 256 × 192 | 256 × 192 |
# of averages | 1 | 1 | 1 |
First TE (msec) | 0.98 | 2.2 | 2.2 |
Delta TE (msec) | 0.7 | 2.2 | 2.2 |
# of echoes | 6 | 2 | 2 |
TR (msec) | 5.7 | 6.7 | 6.7 |
Flip angle (degrees) | 5 | 5 | 5 |
Bandwidth (Hz/px) | 2799 | 500 | 500 |
Slice thickness (mm) | 6 | 4 | 4 |
Acceleration | SENSE | NA | NA |
Acceleration factor | 2 | NA | NA |
Scan time (minutes) | 0:16 | 0:18 | 0:18 |
Appendix 2
An example of chemical shift fat fraction calculation with correction to a 20% lipid standard is shown. Opposed-phase (A1) and in-phase (A2) images of the liver with the lipid bag (Fresenius Kabi, Sweden) along the left abdominal wall are also shown. Regions of interest (ROIs) of approximately 200–300 mm2 are shown, placed both in the right hepatic lobe, avoiding large vessels (black circles), and in the lipid bag on the same images (white circles). Corrected chemical shift is calculated as follows (LB = lipid bag, IP = in phase, OP = opposed phase):
Corrected liver fat is measured on each of three images and reported as an average of those three values. Uncorrected and corrected fat fraction values measured using this technique were compared to the results obtained with a commercially available gradient-echo-based fat quantitation sequence (HepaFat-Scan, Resonance Health; Australia) in 11 patients (A3). There was a strong, statistically significant correlation between each of the chemical shift techniques and the commercially available sequence (r = 0.96, p = 0.006 for both comparisons). The uncorrected data are indicated by empty boxes with a thin dashed trend line. The corrected data are indicated by black diamonds with a thin solid trend line. The solid gray line is the line of equality. For the exam shown, chemical shift fat fraction was calculated at 10.2% with a fat fraction of 9.6% calculated by HepaFat.
Appendix 3
Linear mixed model parameter estimates and p values based on solution for fixed effects for prediction of liver fat fraction (%). Models include variable (Age*Age_group), where 1 = age >10 years. Data for two separate models (“Clinical Data Only” and “Clinical and Imaging Data”) are presented.
Parameter | Clinical data only | Clinical and imaging data | ||
---|---|---|---|---|
Estimate | p value | Estimate | p value | |
Sex (female) | −3.44 | 0.0013 | −1.16 | 0.2586 |
Age (years) | 0.01 | 0.9961 | −0.45 | 0.2281 |
Age*Age_group | −0.30 | 0.1851 | −0.16 | 0.4299 |
BMI (kg/m2) | 0.19 | 0.0189 | −0.10 | 0.2827 |
ALT (U/L) | 0.03 | 0.0001 | 0.02 | 0.0016 |
Diabetes | 3.66 | 0.1211 | 0.17 | 0.9389 |
“Prediabetes” | 0.43 | 0.6810 | 0.35 | 0.7164 |
Liver volume (mL) | 0.006 | <.0001 | ||
Liver stiffness (kPa) | −2.70 | 0.0012 |
Linear mixed model parameter estimates and p values based on solution for fixed effects for prediction of liver stiffness (kPa). Models include variable (Age*Age_group), where 1 = age >10 years. Data for two separate models (“Clinical Data Only” and “Clinical and Imaging Data”) are presented.
Parameter | Clinical data only | Clinical and imaging data | ||
---|---|---|---|---|
Estimate | p value | Estimate | p value | |
Sex (female) | 0.04 | 0.5770 | 0.10 | 0.2499 |
Age (years) | −0.04 | 0.1295 | −0.08 | 0.0111 |
Age*Age_group | 0.03 | 0.0420 | 0.04 | 0.0390 |
BMI (kg/m2) | 0.02 | <.0001 | 0.01 | 0.1685 |
ALT (U/L) | 0.002 | <.0001 | 0.002 | 0.0006 |
Diabetes | 0.21 | 0.1633 | 0.12 | 0.5119 |
“Prediabetes” | 0.04 | 0.5322 | 0.06 | 0.4728 |
Liver volume (mL) | 0.0003 | 0.0012 | ||
Fat fraction (%) | −0.02 | 0.0012 |
Linear mixed model parameter estimates and p values based on solution for fixed effects for prediction of liver volume (mL). Models include variable (Age*Age_group), where 1 = age >10 years. Data for two separate models (“Clinical Data Only” and “Clinical and Imaging Data”) are presented.
Parameter | Clinical data only | Clinical and imaging data | ||
---|---|---|---|---|
Estimate | p value | Estimate | p value | |
Sex (female) | −288.19 | <.0001 | −262.08 | 0.0003 |
Age (years) | 13.42 | 0.5971 | 52.78 | 0.0487 |
Age*Age_group | 12.71 | 0.3586 | −0.65 | 0.9652 |
BMI (kg/m2) | 58.57 | <.0001 | 49.08 | <.0001 |
ALT (U/L) | 2.21 | <.0001 | 0.74 | 0.1531 |
Diabetes | 560.05 | 0.0002 | 519.21 | 0.0009 |
“Prediabetes” | 46.22 | 0.4939 | −2.35 | 0.9731 |
Fat fraction (%) | 30.50 | <.0001 | ||
Mean stiffness (kPa) | 192.98 | 0.0012 |
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Joshi, M., Dillman, J.R., Singh, K. et al. Quantitative MRI of fatty liver disease in a large pediatric cohort: correlation between liver fat fraction, stiffness, volume, and patient-specific factors. Abdom Radiol 43, 1168–1179 (2018). https://doi.org/10.1007/s00261-017-1289-y
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DOI: https://doi.org/10.1007/s00261-017-1289-y