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Whole-organ and segmental stiffness measured with liver magnetic resonance elastography in healthy adults: significance of the region of interest.

Rusak G, Zawada E, Lemanowicz A, Serafin Z - Abdom Imaging (2015)

Bottom Line: Since the method is not well established, several different protocols were proposed that differ in results.Results of measurement within segment 8 were closest to the whole-liver method (ICC, 0.84).The most reproducible method is averaging of cross sections of the whole liver.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology and Diagnostic Imaging, Nicolaus Copernicus University, Collegium Medicum, ul. Skłodowskiej-Curie 9, 85-094, Bydgoszcz, Poland.

ABSTRACT

Purpose: MR elastography (MRE) is a recent non-invasive technique that provides in vivo data on the viscoelasticity of the liver. Since the method is not well established, several different protocols were proposed that differ in results. The aim of the study was to analyze the variability of stiffness measurements in different regions of the liver.

Methods: Twenty healthy adults aged 24-45 years were recruited. The examination was performed using a mechanical excitation of 64 Hz. MRE images were fused with axial T2WI breath-hold images (thickness 10 mm, spacing 10 mm). Stiffness was measured as a mean value of each cross section of the whole liver, on a single largest cross section, in the right lobe, and in ROIs (50 pix.) placed in the center of the left lobe, segments 5/6, 7, 8, and the parahilar region.

Results: Whole-liver stiffness ranged from 1.56 to 2.75 kPa. Mean segmental stiffness differed significantly between the tested regions (range from 1.55 ± 0.28 to 2.37 ± 0.32 kPa; P < 0.0001, ANOVA). Within-method variability of measurements ranged from 14 % for whole liver and segment 8-26 % for segment 7. Within-subject variability ranged from 13 to 31 %. Results of measurement within segment 8 were closest to the whole-liver method (ICC, 0.84).

Conclusions: Stiffness of the liver presented significant variability depending on the region of measurement. The most reproducible method is averaging of cross sections of the whole liver. There was significant variability between stiffness in subjects considered healthy, which requires further investigation.

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Related in: MedlinePlus

Single cross section of the liver. Whole-liver stiffness was calculated as a mean of such ROIs drawn on all axial slices of the liver. The ROI is presented on T2-weighted image (left), elastogram (middle), and fused image of T2WI and elastogram (right).
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Fig1: Single cross section of the liver. Whole-liver stiffness was calculated as a mean of such ROIs drawn on all axial slices of the liver. The ROI is presented on T2-weighted image (left), elastogram (middle), and fused image of T2WI and elastogram (right).

Mentions: The stiffness was measured on 8 axial slices. The middle (5th) slice was placed at the bifurcation of the portal vein and served as a reference slice in each patient. Whole-liver stiffness was measured using consecutive ROIs, which covered slices of the whole liver, excluding the inferior vena cava and the gallbladder. Therefore, stiffness was an average of 8 cross sections of the liver (Fig. 1). Cross-sectional stiffness measured according to the method by Lee et al. [15]. It was calculated in a ROI that was placed on a single largest cross section of the liver and was excluding great hepatic vessels; it accounted for approximately 70 % of the entire cross section of the liver. Right lobe stiffness was measured on the largest single cross section, excluding hepatic great vessels. Additionally, segmental stiffness was measured in 5 small ROIs (50 pix.—approx. 150 mm2) that were placed in the center of the left lobe (segments 2/3), segments 5/6, 7, 8, and the parahilar region (Fig. 2). ROIs were placed centrally within the liver parenchyma avoiding large hepatic vessels.Fig. 1


Whole-organ and segmental stiffness measured with liver magnetic resonance elastography in healthy adults: significance of the region of interest.

Rusak G, Zawada E, Lemanowicz A, Serafin Z - Abdom Imaging (2015)

Single cross section of the liver. Whole-liver stiffness was calculated as a mean of such ROIs drawn on all axial slices of the liver. The ROI is presented on T2-weighted image (left), elastogram (middle), and fused image of T2WI and elastogram (right).
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4372679&req=5

Fig1: Single cross section of the liver. Whole-liver stiffness was calculated as a mean of such ROIs drawn on all axial slices of the liver. The ROI is presented on T2-weighted image (left), elastogram (middle), and fused image of T2WI and elastogram (right).
Mentions: The stiffness was measured on 8 axial slices. The middle (5th) slice was placed at the bifurcation of the portal vein and served as a reference slice in each patient. Whole-liver stiffness was measured using consecutive ROIs, which covered slices of the whole liver, excluding the inferior vena cava and the gallbladder. Therefore, stiffness was an average of 8 cross sections of the liver (Fig. 1). Cross-sectional stiffness measured according to the method by Lee et al. [15]. It was calculated in a ROI that was placed on a single largest cross section of the liver and was excluding great hepatic vessels; it accounted for approximately 70 % of the entire cross section of the liver. Right lobe stiffness was measured on the largest single cross section, excluding hepatic great vessels. Additionally, segmental stiffness was measured in 5 small ROIs (50 pix.—approx. 150 mm2) that were placed in the center of the left lobe (segments 2/3), segments 5/6, 7, 8, and the parahilar region (Fig. 2). ROIs were placed centrally within the liver parenchyma avoiding large hepatic vessels.Fig. 1

Bottom Line: Since the method is not well established, several different protocols were proposed that differ in results.Results of measurement within segment 8 were closest to the whole-liver method (ICC, 0.84).The most reproducible method is averaging of cross sections of the whole liver.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology and Diagnostic Imaging, Nicolaus Copernicus University, Collegium Medicum, ul. Skłodowskiej-Curie 9, 85-094, Bydgoszcz, Poland.

ABSTRACT

Purpose: MR elastography (MRE) is a recent non-invasive technique that provides in vivo data on the viscoelasticity of the liver. Since the method is not well established, several different protocols were proposed that differ in results. The aim of the study was to analyze the variability of stiffness measurements in different regions of the liver.

Methods: Twenty healthy adults aged 24-45 years were recruited. The examination was performed using a mechanical excitation of 64 Hz. MRE images were fused with axial T2WI breath-hold images (thickness 10 mm, spacing 10 mm). Stiffness was measured as a mean value of each cross section of the whole liver, on a single largest cross section, in the right lobe, and in ROIs (50 pix.) placed in the center of the left lobe, segments 5/6, 7, 8, and the parahilar region.

Results: Whole-liver stiffness ranged from 1.56 to 2.75 kPa. Mean segmental stiffness differed significantly between the tested regions (range from 1.55 ± 0.28 to 2.37 ± 0.32 kPa; P < 0.0001, ANOVA). Within-method variability of measurements ranged from 14 % for whole liver and segment 8-26 % for segment 7. Within-subject variability ranged from 13 to 31 %. Results of measurement within segment 8 were closest to the whole-liver method (ICC, 0.84).

Conclusions: Stiffness of the liver presented significant variability depending on the region of measurement. The most reproducible method is averaging of cross sections of the whole liver. There was significant variability between stiffness in subjects considered healthy, which requires further investigation.

Show MeSH
Related in: MedlinePlus