Accuracy of Liver Fat Quantification With Advanced CT, MRI, and Ultrasound Techniques: Prospective Comparison With MR Spectroscopy

Abstract

OBJECTIVE The purpose of this study was to prospectively evaluate the accuracy of proton-density fat-fraction, single- and dual-energy CT (SECT and DECT), gray-scale ultrasound (US), and US shear-wave elastography (US-SWE) in the quantification of hepatic steatosis with MR spectroscopy (MRS) as the reference standard. SUBJECTS AND METHODS Fifty adults who did not have symptoms (23 men, 27 women; mean age, 57 ± 5 years; body mass index, 27 ± 5) underwent liver imaging with unenhanced SECT, DECT, gray-scale US, US-SWE, proton-density fat-fraction MRI, and MRS for this prospective trial. MRS voxels for the reference standard were colocalized with all other modalities under investigation. For SECT (120 kVp), attenuation values were recorded. For rapid-switching DECT (80/140 kVp), monochromatic images (70–140 keV) and fat density–derived material decomposition images were reconstructed. For proton-density fat fraction MRI, a quantitative chemical shift–encoded method was used. For US, echogenicity was evaluated on a qualitative 0–3 scale. Quantitative US shear-wave velocities were also recorded. Data were analyzed by linear regression for each technique compared with MRS. RESULTS There was excellent correlation between MRS and both proton-density fat-fraction MRI (r2 = 0.992; slope, 0.974; intercept, −0.943) and SECT (r2 = 0.856; slope, −0.559; intercept, 35.418). DECT fat attenuation had moderate correlation with MRS measurements (r2 = 0.423; slope, 0.034; intercept, 8.459). There was good correlation between qualitative US echogenicity and MRS measurements with a weighted kappa value of 0.82. US-SWE velocity did not have reliable correlation with MRS measurements (r2 = 0.004; slope, 0.069; intercept, 6.168). CONCLUSION Quantitative MRI proton-density fat fraction and SECT fat attenuation have excellent linear correlation with MRS measurements and can serve as accurate noninvasive biomarkers for quantifying steatosis. Material decomposition with DECT does not improve the accuracy of fat quantification over conventional SECT attenuation. US-SWE has poor accuracy for liver fat quantification.

Standardized Approach for ROI-Based Measurements of Proton Density Fat Fraction and R2* in the Liver

“…This study retrospectively analyzed 90 liver CSE MRI datasets previously acquired for studies at the University of Wisconsin-Madison [19, 24, 26, 27]. These studies were compliant with HIPAA and approved by the institutional review board.…”

“…Datasets were divided into two cohorts. Cohort A included 53 subjects (mean age, 51.9 years; age range, 23–84 years; 27 women, 26 men): 34 patients presenting with a clinical indication for an abdominal MRI [19, 24, 26] and 19 healthy subjects recruited as part of a study comparing CT and MRI [27]. To ensure that our analysis included high R2* values, cohort B included 37 patients (mean age, 43.6 years; age range, 10–78 years; 24 men, 13 women) recruited on the basis of having suspected liver iron overload.…”

The measurement of liver fat from single-energy quantitative computed tomography scans

“…Methods of investigation and diagnosis include liver biopsy (30,31), ultrasonography (22,32), CT imaging (22,32) and MR imaging, including proton magnetic resonance spectroscopy ( 1 H-MRS) (27,28) and the modified Dixon (mDixon) technique (29). Of these, the MR methods are widely accepted as the most sensitive non-invasive method to assess hepatic steatosis (33,34). However, the CT methods with which they have been compared have been semiquantitative methods based on Hounsfield units, or the difference in attenuation between the liver and spleen (7)(8)(9)(10)(11), and as such not subject to rigorous calibration and quality control and dependent on factors such as kV p , X-ray filtration, patient size, and the make and model of CT scanner.…”

Multiorgan, Multimodality Imaging in Cardiometabolic Disease

“…Steatotic liver demonstrates increased scatter and attenuation sound waves compared to normal liver and produces characteristic qualitative markers such as hyperintense liver, blurry hepatic vessels and poor resolution of the diaphragm. US is the most common method for hepatic fat quantification although its use is limited by low sensitivity and poor penetration in obese individuals 25 .…”

“…Spectroscopy is typically less widely available both in instrumentation and expertise. Imaging techniques leverage the difference between in and out-of phase water and fat signals and can produce fat fraction maps 25 .…”