Comparison of Dynamic and Liver-Specific Gadoxetic Acid Contrast-Enhanced MRI versus Apparent Diffusion Coefficients

Hepatic lesions often present diagnostic connundrums with conventional MR techniques. Hepatobiliary phase contrast-enhanced imaging with gadoxetic acid can aid in the characterization of such lesions. However, quantitative measures describing late-phase enhancement must be assessed relative to their accuracy of hepatic lesion classification.To compare quantitative parameters in gadoxetic acid contrast-enhanced dynamic and hepatobiliary phase imaging versus apparent diffusion coefficients in hepatic lesion characterization.57 patients with focal hepatic lesions on gadoxetic acid MR were included. Lesion enhancement at standard post-contrast time points and in the hepatobiliary phase (HB; 15 and 25 minutes post-contrast) was assessed via calculation of contrast (CR) and enhancement ratios (ER). Apparent diffusion coefficient (ADC) values were also obtained. Values for these parameters were compared among lesions and ROC analyses performed.HB enhancement was greatest with FNH and adenomas. HB ER parameters but not HB CR could distinguish HCC from benign entities (0.9 ER ROC AUC versus 0.5 CR ROC AUC). There was no statistically significant difference found between the 15 and 25 minutes HB time points in detection of any lesion (p>0.4). ADC values were statistically significantly higher with hemangiomas (p<0.05) without greater accuracy in lesion detection relative to HB phase parameters.Hepatobiliary phase gadoxetic acid contrast-enhanced MR characterizes focal hepatic lesions more accurately than ADC and conventional dynamic post-contrast time point enhancement parameters. ER values are generally superior to CR. No discernible benefit of 25 minute versus 15 minute delayed imaging is demonstrated

Mean enhancement ratios over time.

<p>Mean enhancement ratios not demonstrating statistically significant differences are enclosed within a single shape (i.e. circle, square, or triangle). Those not enclosed by the same shape demonstrate statistically significant differences in mean enhancement ratios for a given time point (p<0.05).</p

Maximum sensitivity (SS) and specificity (SP) values obtainable with quantitative conventional and hepatobiliary phase enhancement parameters.

<p>ER – enhancement ratio.</p><p>CR – contrast ratio.</p><p>HB – hepatobiliary phase.</p><p>HCC = Hepatocellular carcinoma.</p><p>FNH = Focal Nodular Hyperplasia.</p

Representative images illustrating a case of focal nodular hyperplasia on fat saturated T2-weighted images (top left), ADC maps (top middle), and post-contrast images in the arterial (top right), portal venous (bottom left), venous (bottom middle), and hepatobiliary phases (15 minutes post-contrast; bottom right).

<p>Representative images illustrating a case of focal nodular hyperplasia on fat saturated T2-weighted images (top left), ADC maps (top middle), and post-contrast images in the arterial (top right), portal venous (bottom left), venous (bottom middle), and hepatobiliary phases (15 minutes post-contrast; bottom right).</p

Differentiation Between Pairs of Liver Lesions.

*<p>denotes a statistically significant (p<0.05) areas under the curve values relative to a random test (AUC = 0.5).</p><p>Bolded values denote AUC values significantly less than non-bolded values in a given row.</p><p>HCC = Hepatocellular carcinoma.</p><p>FNH = Focal Nodular Hyperplasia.</p><p>ROC AUC = Receiver Operator Characteristic Area Under the Curve Values.</p><p>ADC = Apparent Diffusion Coefficient (mm²/s).</p><p>HB 1,2 = Hepatobiliary Phase (15 and 25 minutes post-contrast).</p

Cutoff values for quantitative enhancement parameters in the differentiation of HCC from other solitary hepatic lesions.

*<p>Denotes measures recommended quantitative parameter for this evaluation.</p><p>SS – Sensitivity.</p><p>SP– Specificity.</p><p>ER – enhancement ratio.</p><p>CR – contrast ratio.</p><p>HB 1,2 = Hepatobiliary Phase (15 and 25 minutes post-contrast).</p

ROC curves generated from contrast ratio (CR) and enhancement ratio (ER) parameters.

<p>These were used for identification of hepatocellular carcinoma (HCC), focal nodular hyperplasia (FNH), hemangiomas, and adenomas at hepatobiliary phase time points 15 (HB1) and 25 minutes post-contrast. * reflects statistically significant (p<0.05) differences relative to a random test (AUC = 0.5) and *** reflects statistically significant reflects p-values less than 0.001. AUC values statistically significantly greater than others are boxed.</p

ROC curves for ADC values.

<p>These reflect the ability to detect hepatocellular carcinoma (HCC), focal nodular hyperplasia (FNH), hemangiomas, and adenomas. * reflects statistically significant (p = 0.05) differences relative to a random test (AUC = 0.5).</p

Representative images illustrating a case of a hemangioma on fat saturated T2-weighted images (top left), ADC maps (top middle), and post-contrast images in the arterial (top right), portal venous (bottom left), venous (bottom middle), and hepatobiliary phases (15 minutes post-contrast; bottom right).

<p>Representative images illustrating a case of a hemangioma on fat saturated T2-weighted images (top left), ADC maps (top middle), and post-contrast images in the arterial (top right), portal venous (bottom left), venous (bottom middle), and hepatobiliary phases (15 minutes post-contrast; bottom right).</p

Representative images illustrating a case of hepatocellular carcinoma on fat saturated T2-weighted images (top left), ADC maps (top middle), and post-contrast images in the arterial (top right), portal venous (bottom left), venous (bottom middle), and hepatobiliary phases (15 minutes post-contrast; bottom right).

<p>Representative images illustrating a case of hepatocellular carcinoma on fat saturated T2-weighted images (top left), ADC maps (top middle), and post-contrast images in the arterial (top right), portal venous (bottom left), venous (bottom middle), and hepatobiliary phases (15 minutes post-contrast; bottom right).</p