Efficacy and safety of MR imaging with liver-specific contrast agent: U.S. multicenter phase III study

Machine learning based on gadoxetic acid-enhanced MRI for differentiating atypical intrahepatic mass-forming cholangiocarcinoma from poorly differentiated hepatocellular carcinoma

PURPOSE

The study was to develop a Gd-EOB-DTPA-enhanced MRI radiomics model for differentiating atypical intrahepatic mass-forming cholangiocarcinoma (aIMCC) from poorly differentiated hepatocellular carcinoma (pHCC).

MATERIALS AND METHODS

A total of 134 patients (51 aIMCC and 83 pHCC) who underwent Gadoxetic acid-enhanced MRI between March 2016 and March 2022 were enrolled in this study and then randomly assigned to the training and validation cohorts by 7:3 (93 patients and 41 patients, respectively). The radiomics features were extracted from the hepatobiliary phase of Gadoxetic acid-enhanced MRI. In the training cohort, the SelectKBest and the least absolute shrinkage and selection operator (LASSO) were used to select the radiomics features. The clinical, radiomics, and clinical-radiomics model were established using four machine learning algorithms. The performance of the model was evaluated by the receiver operating characteristic (ROC) curve. Comparison of the radiomics and clinical-radiomics model was done by the Delong test. The clinical usefulness of the model was evaluated using decision curve analysis (DCA).

RESULTS

In 1132 extracted radiomic features, 15 were selected to develop radiomics signature. For identifying aIMCC and pHCC, the radiomics model constructed by random forest algorithm showed the high performance (AUC = 0.90) in the training cohort. The performance of the clinical-radiomics model (AUC = 0.89) was not significantly different (P = 0.88) from that of the radiomics model constructed by random forest algorithm (AUC = 0.86) in the validation cohort. DCA demonstrated that the clinical-radiomics model constructed by random forest algorithm had a high net clinical benefit.

CONCLUSION

The clinical-radiomics model is an effective tool to distinguish aIMCC from pHCC and may provide additional value for the development of treatment plans.

Comprehensive Approach to Assessment of Liver Viability During Normothermic Machine Perfusion

Liver transplantation is the most effective treatment of advanced liver disease, and the use of extended criteria donor organs has broadened the source of available livers. Although normothermic machine perfusion (NMP) has become a useful tool in liver transplantation, there are no consistent criteria that can be used to evaluate the viability of livers during NMP. This review summarizes the criteria, indicators, and methods used to evaluate liver viability during NMP. The shape, appearance, and hemodynamics of the liver can be analyzed at a macroscopic level, while markers of liver injury, indicators of liver and bile duct function, and other relevant indicators can be evaluated by biochemical analysis. The liver can also be assessed by tissue biopsy at the microscopic level. Novel methods for assessment of liver viability are introduced. The limitations of evaluating liver viability during NMP are discussed and suggestions for future clinical practice are provided.

Application of A U-Net for Map-like Segmentation and Classification of Discontinuous Fibrosis Distribution in Gd-EOB-DTPA-Enhanced Liver MRI

Highlights

Abstract

We aimed to evaluate whether U-shaped convolutional neuronal networks can be used to segment liver parenchyma and indicate the degree of liver fibrosis/cirrhosis at the voxel level using contrast-enhanced magnetic resonance imaging. This retrospective study included 112 examinations with histologically determined liver fibrosis/cirrhosis grade (Ishak score) as the ground truth. The T1-weighted volume-interpolated breath-hold examination sequences of native, arterial, late arterial, portal venous, and hepatobiliary phases were semi-automatically segmented and co-registered. The segmentations were assigned the corresponding Ishak score. In a nested cross-validation procedure, five models of a convolutional neural network with U-Net architecture (nnU-Net) were trained, with the dataset being divided into stratified training/validation (n = 89/90) and holdout test datasets (n = 23/22). The trained models precisely segmented the test data (mean dice similarity coefficient = 0.938) and assigned separate fibrosis scores to each voxel, allowing localization-dependent determination of the degree of fibrosis. The per voxel results were evaluated by the histologically determined fibrosis score. The micro-average area under the receiver operating characteristic curve of this seven-class classification problem (Ishak score 0 to 6) was 0.752 for the test data. The top-three-accuracy-score was 0.750. We conclude that determining fibrosis grade or cirrhosis based on multiphase Gd-EOB-DTPA-enhanced liver MRI seems feasible using a 2D U-Net. Prospective studies with localized biopsies are needed to evaluate the reliability of this model in a clinical setting.

Gadolinium-ethoxybenzyl-diethylenetriamine penta-acetic acid-enhanced magnetic resonance imaging for evaluating fibrosis regression in chronic hepatitis C patients after direct-acting antiviral

BACKGROUND

Direct acting antiviral (DAA) therapy has enabled hepatitis C virus infection to become curable, while histological changes remain uncontained. Few valid non-invasive methods can be confirmed for use in surveillance. Gadolinium-ethoxybenzyl-diethylenetriamine penta-acetic acid (Gd-EOB-DTPA) is a liver-specific magnetic resonance imaging (MRI) contrast, related to liver function in the hepatobiliary phase (HBP). Whether Gd-EOB-DTPA-enhanced MRI can be used in the diagnosis and follow up of hepatic fibrosis in patients with chronic hepatitis C (CHC) has not been investigated.

AIM

To investigate the diagnostic and follow-up values of Gd-EOB-DTPA-enhanced MRI for hepatic histology in patients with CHC.

METHODS

Patients with CHC were invited to undergo Gd-EOB-DTPA-enhanced MRI and liver biopsy before treatment, and those with paired qualified MRI and liver biopsy specimens were included. Transient elastography (TE) and blood tests were also arranged. Patients treated with DAAs who achieved 24-wk sustained virological response (SVR) underwent Gd-EOB-DTPA-enhanced MRI and liver biopsy again. The signal intensity (SI) of the liver and muscle were measured in the unenhanced phase (UEP) (SI_UEP-liver, SI_UEP-muscle) and HBP (SI_HBP-liver, SI_HBP-muscle) via MRI. The contrast enhancement index (CEI) was calculated as [(SI_HBP-liver/SI_HBP-muscle)]/[(SI_UEP-liver/SI_UEP-muscle)]. Liver stiffness measurement (LSM) was confirmed with TE. Serologic markers, aspartate aminotransferase-to-platelet ratio index (APRI) and Fibrosis-4 (FIB-4), were also calculated according to blood tests. The grade of inflammation and stage of fibrosis were evaluated with the modified histology activity index (mHAI) and Ishak fibrosis score, respectively. Fibrosis regression was defined as a ≥ 1-point decrease in the Ishak fibrosis score. The correlation between the CEI and liver pathology was evaluated. The diagnostic and follow-up values of the CEI, LSM, and serologic markers were compared.

RESULTS

Thirty-nine patients with CHC were enrolled [average age, 42.3 ± 14.4 years; 20/39 (51.3%) male]. Twenty-one enrolled patients had eligible paired Gd-EOB-DTPA-enhanced MRI and liver tissues after achieving SVR. The mHAI median significantly decreased after SVR [baseline 6.0 (4.5-13.5) vs SVR 2.0 (1.5-5.5), Z = 3.322, P = 0.017], but the median stage of fibrosis did not notably change (P > 0.05). Sixty pairs of qualified MRI and liver tissue samples were available for use to analyze the relationship between the CEI and hepatic pathology. The CEI was negatively correlated with the mHAI (r = -0.56, P < 0.001) and Ishak score (r = -0.69, P < 0.001). Further stratified analysis showed that the value of the CEI decreased with the progression of the stage of fibrosis rather than with the grade of necroinflammation. For patients with Ishak score ≥ 5, the areas under receiver operating characteristics curve of the CEI, LSM, APRI, and FIB-4 were approximately at baseline, 0.87–0.93, and after achieving SVR, 0.83–0.91. The CEI cut-off value was stable (baseline 1.58 and SVR 1.59), but those of the APRI (from 1.05 to 0.24), FIB-4 (from 1.78 to 1.28), and LSM (from 10.8 kpa to 7.1 kpa) decreased dramatically. The APRI and FIB-4 cannot be used as diagnostic means for SVR in patients with Ishak score ≥ 3 (P > 0.05). Seven patients achieved fibrosis regression after achieving SVR. In these patients, the CEI median increased (from 1.71 to 1.83, Z = -1.981, P = 0.048) and those of the APRI (from 1.71 to 1.83, Z = -2.878, P = 0.004) and LSM (from 6.6 to 4.8, Z = -2.366, P = 0.018) decreased. However, in patients without fibrosis regression, the medians of the APRI, FIB-4, and LSM also changed significantly (P < 0.05).

CONCLUSION

Gd-EOB-DTPA-enhanced MRI has good diagnostic value for staging fibrosis in patients with CHC. It can be used for fibrotic-change monitoring post SVR in patients with CHC treated with DAAs.

Stereotactic radiotherapy for liver oligometastases

The liver is the first metastatic site in 15–25% of colorectal cancer patients and one of the first metastatic sites for lung and breast cancer patients.

A computed tomography (CT ) scan with contrast medium is a standard procedure for assessing liver lesions but magnetic resonance imaging (MRI) characterizes small lesions better thanks to its high soft-tissue contrast. Positron emission tomography with computed tomography (PET-CT ) plays a complementary role in the diagnosis of liver metastases. Triphasic (arterial, venous and time-delayed) acquisition of contrast-medium CT images is the first step in treatment planning. Since the liver exhibits a relatively wide mobility due to respiratory movements and bowel filling, appropriate techniques are needed for target identification and motion management. Contouring requires precise recognition of target lesion edges. Information from contrast MRI and/or PET-CT is crucial as they best visualize metastatic disease in the parenchyma. Even though different fractionation schedules were reported, doses and fractionation schedules for liver stereotactic radiotherapy (SRT ) have not yet been established. The best local control rates were obtained with BED₁₀ values over 100 Gy. Local control rates from most retrospective studies, which were limited by short follow-ups and included different primary tumors with intrinsic heterogeneity, ranged from 60% to 90% at 1 and 2 years. The most common SRT-related toxicities are increases in liver enzymes, hyperbilirubinemia and hypoalbuminemia. Overall, late toxicity is mild even in long-term follow-ups.

Imaging-Based Staging of Hepatic Fibrosis in Patients with Hepatitis B: A Dynamic Radiomics Model Based on Gd-EOB-DTPA-Enhanced MRI

Accurate grading of liver fibrosis can effectively assess the severity of liver disease and help doctors make an appropriate diagnosis. This study aimed to perform the automatic staging of hepatic fibrosis on patients with hepatitis B, who underwent gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging with dynamic radiomics analysis. The proposed dynamic radiomics model combined imaging features from multi-phase dynamic contrast-enhanced (DCE) images and time-domain information. Imaging features were extracted from the deep learning-based segmented liver volume, and time-domain features were further explored to analyze the variation in features during contrast enhancement. Model construction and evaluation were based on a 132-case data set. The proposed model achieved remarkable performance in significant fibrosis (fibrosis stage S1 vs. S2–S4; accuracy (ACC) = 0.875, area under the curve (AUC) = 0.867), advanced fibrosis (S1–S2 vs. S3–S4; ACC = 0.825, AUC = 0.874), and cirrhosis (S1–S3 vs. S4; ACC = 0.850, AUC = 0.900) classifications in the test set. It was more dominant compared with the conventional single-phase or multi-phase DCE-based radiomics models, normalized liver enhancement, and some serological indicators. Time-domain features were found to play an important role in the classification models. The dynamic radiomics model can be applied for highly accurate automatic hepatic fibrosis staging.

Ex vivo gadoxetate relaxivities in rat liver tissue and blood at five magnetic field strengths from 1.41 to 7 T

Quantitative mapping of gadoxetate uptake and excretion rates in liver cells has shown potential to significantly improve the management of chronic liver disease and liver cancer. Unfortunately, technical and clinical validation of the technique is currently hampered by the lack of data on gadoxetate relaxivity. The aim of this study was to fill this gap by measuring gadoxetate relaxivity in liver tissue, which approximates hepatocytes, in blood, urine and bile at magnetic field strengths of 1.41, 1.5, 3, 4.7 and 7 T. Measurements were performed ex vivo in 44 female Mrp2 knockout rats and 30 female wild-type rats who had received an intravenous bolus of either 10, 25 or 40 μmol/kg gadoxetate. T1 was measured at 37 ± 3°C on NMR instruments (1.41 and 3 T), small-animal MRI (4.7 and 7 T) and clinical MRI (1.5 and 3 T). Gadolinium concentration was measured with optical emission spectrometry or mass spectrometry. The impact on measurements of gadoxetate rate constants was determined by generalizing pharmacokinetic models to tissues with different relaxivities. Relaxivity values (L mmol-1 s-1 ) showed the expected dependency on tissue/biofluid type and field strength, ranging from 15.0 ± 0.9 (1.41) to 6.0 ± 0.3 (7) T in liver tissue, from 7.5 ± 0.2 (1.41) to 6.2 ± 0.3 (7) T in blood, from 5.6 ± 0.1 (1.41) to 4.5 ± 0.1 (7) T in urine and from 5.6 ± 0.4 (1.41) to 4.3 ± 0.6 (7) T in bile. Failing to correct for the relaxivity difference between liver tissue and blood overestimates intracellular uptake rates by a factor of 2.0 at 1.41 T, 1.8 at 1.5 T, 1.5 at 3 T and 1.2 at 4.7 T. The relaxivity values derived in this study can be used retrospectively and prospectively to remove a well-known bias in gadoxetate rate constants. This will promote the clinical translation of MR-based liver function assessment by enabling direct validation against reference methods and a more effective translation between in vitro findings, animal models and patient studies.

Does Hepatic Steatosis Influence the Detection Rate of Metastases in the Hepatobiliary Phase of Gadoxetic Acid-Enhanced MRI?

The aim of this exploratory study was to evaluate the influence of hepatic steatosis on the detection rate of metastases in gadoxetic acid-enhanced liver magnetic resonance imaging (MRI). A total of 50 patients who underwent gadoxetic acid-enhanced MRI (unenhanced T1w in- and opposed-phase, T2w fat sat, unenhanced 3D-T1w fat sat and 3-phase dynamic contrast-enhanced (uDP), 3D-T1w fat sat hepatobiliary phase (HP)) were retrospectively included. Two blinded observers (O1/O2) independently assessed the images to determine the detection rate in uDP and HP. The hepatic signal fat fraction (HSFF) was determined as the relative signal intensity reduction in liver parenchyma from in- to opposed-phase images. A total of 451 liver metastases were detected (O1/O2, n = 447/411). O1/O2 detected 10.9%/9.3% of lesions exclusively in uDP and 20.2%/15.5% exclusively in HP. Lesions detected exclusively in uDP were significantly associated with a larger HSFF (area under curve (AUC) of receiver operating characteristic (ROC) analysis, 0.93; p < 0.001; cutoff, 41.5%). The exclusively HP-positive lesions were significantly associated with a smaller diameter (ROC-AUC, 0.82; p < 0.001; cutoff, 5 mm) and a smaller HSFF (ROC-AUC, 0.61; p < 0.001; cutoff, 13.3%). Gadoxetic acid imaging has the advantage of detecting small occult metastatic liver lesions in the HP. However, using non-optimized standard fat-saturated 3D-T1w protocols, severe steatosis (HSFF > 30%) is a potential pitfall for the detection of metastases in HP.

A 3D Deep Neural Network for Liver Volumetry in 3T Contrast-Enhanced MRI

PURPOSE

 To create a fully automated, reliable, and fast segmentation tool for Gd-EOB-DTPA-enhanced MRI scans using deep learning.

MATERIALS AND METHODS

 Datasets of Gd-EOB-DTPA-enhanced liver MR images of 100 patients were assembled. Ground truth segmentation of the hepatobiliary phase images was performed manually. Automatic image segmentation was achieved with a deep convolutional neural network.

RESULTS

 Our neural network achieves an intraclass correlation coefficient (ICC) of 0.987, a Sørensen-Dice coefficient of 96.7 ± 1.9 % (mean ± std), an overlap of 92 ± 3.5 %, and a Hausdorff distance of 24.9 ± 14.7 mm compared with two expert readers who corresponded to an ICC of 0.973, a Sørensen-Dice coefficient of 95.2 ± 2.8 %, and an overlap of 90.9 ± 4.9 %. A second human reader achieved a Sørensen-Dice coefficient of 95 % on a subset of the test set.

CONCLUSION

 Our study introduces a fully automated liver volumetry scheme for Gd-EOB-DTPA-enhanced MR imaging. The neural network achieves competitive concordance with the ground truth regarding ICC, Sørensen-Dice, and overlap compared with manual segmentation. The neural network performs the task in just 60 seconds.

KEY POINTS

  · The proposed neural network helps to segment the liver accurately, providing detailed information about patient-specific liver anatomy and volume.. · With the help of a deep learning-based neural network, fully automatic segmentation of the liver on MRI scans can be performed in seconds.. · A fully automatic segmentation scheme makes liver segmentation on MRI a valuable tool for treatment planning..

CITATION FORMAT

· Winther H, Hundt C, Ringe KI et al. A 3D Deep Neural Network for Liver Volumetry in 3T Contrast-Enhanced MRI. Fortschr Röntgenstr 2021; 193: 305 - 314.

Gd-EOB-DTPA MRI for focal nodular hyperplasia-like lesions in pediatric cancer survivors

OBJECTIVES

To investigate the hepatobiliary enhancement patterns of gadoxetic acid (Gd-EOB-DTPA) MRI and the temporal evolution of focal nodular hyperplasia (FNH)-like lesions in pediatric cancer survivors.

METHODS

We retrospectively included pediatric cancer survivors who had new liver lesions detected during surveillance imaging and who were diagnosed with FNH-like lesions by Gd-EOB-DTPA MRI without the aid of a hepatobiliary phase. The hepatobiliary enhancement patterns of FNH-like lesions were categorized as homogeneous hyperintense/isointense, heterogeneous hyperintense, and ring-like enhancement. Temporal changes in the FNH-like lesions were evaluated by follow-up Gd-EOB-DTPA MRI. Statistical analyses included one-way analysis of variance and Spearman's rank correlation test.

RESULTS

A total of 132 radiologically diagnosed FNH-like lesions in 18 patients showed the three different hepatobiliary enhancement patterns: homogeneous hyperintense/isointense (n = 65, 49%), heterogeneous hyperintense (n = 24, 18%), and ring-like enhancement (n = 43, 33%). A weak positive correlation was found between the lesion size and the hepatobiliary enhancement pattern (p = 0.015). Follow-up MRI showed alterations in the size and number of 55 FNHs in 8 patients, including stable size (n = 15, 27%), increased size (n = 17, 31%), decreased size (n = 11, 20%), disappearance (n = 12, 22%), and 74 new lesions (5 patients, 63%).

CONCLUSIONS

FNH-like lesions in pediatric cancer survivors showed three different hepatobiliary enhancement patterns and various temporal changes. Recognition of the radiological characteristics of FNH-like lesions may avoid unnecessary invasive procedures and reduce patients/parents' anxiety.

KEY POINTS

• FNH-like lesions in pediatric cancer survivors showed three different hepatobiliary enhancement patterns. The most common was homogeneous hyperintense/isointense, followed by heterogeneous hyperintense, and ring-like enhancement. • FNH-like lesions in pediatric cancer survivors can show various temporal changes during follow-up.

Combined gadoxetic acid and gadobenate dimeglumine enhanced liver MRI: a parameter optimization study

PURPOSE

To demonstrate the feasibility of combined delayed-phase gadoxetic acid (GA) and gadobenate dimeglumine (GD) enhanced liver MRI for improved detection of liver metastases, and to optimize contrast agent dose, timing, and flip angle (FA).

METHODS

Fourteen healthy volunteers underwent liver MRI at 3.0T at two visits during which they received two consecutive injections: 1. GA (Visit 1 = 0.025 mmol/kg; Visit 2 = 0.05 mmol/kg) and 2. GD (both visits = 0.1 mmol/kg) 20 min after GA administration. Two sub-studies were performed: Experiment-1 Eight subjects underwent multi-phase breath-held 3D-fat-saturated T1-weighted spoiled gradient echo (SGRE) imaging to determine the optimal imaging window for the combined GA + GD protocol to create a homogeneously hyperintense liver and vasculature ("plain-white-liver") with maximum contrast to muscle which served as a surrogate for metastatic lesions in both experiments. Experiment-2 Six subjects underwent breath-held 3D-fat-saturated T1-weighted SGRE imaging at three different FA to determine the optimal FA for best image contrast. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were evaluated.

RESULTS

Experiment-1 The combined GA + GD protocol created a homogeneously hyperintense liver and vasculature with maximum CNR liver/muscle at approximately 60-120 s after automatic GD-bolus detection. Experiment-2 Flip angles between 25° and 35° at a dose of 0.025 mmol/kg GA provided the best combination that minimized liver/vasculature CNR, while maximizing liver/muscle CNR. CNR performance to achieve a "plain-white-liver" was superior with 0.025 mmol/kg GA compared to 0.05 mmol/kg.

CONCLUSION

Combined GA + GD enhanced T1-weighted MRI is feasible to achieve a homogeneously "plain-white-liver". Future studies need to confirm that this protocol can improve sensitivity of liver lesion detection in patients with metastatic liver disease.

[Examination of Gd-EOB-DTPA Liver Dynamic Contrast-enhanced MRI Using Radial VIBE with k-space Weighted Image Contrast Method]

Dynamic contrast-enhanced magnetic imaging (DCE-MRI) is a useful method for detection and diagnosis of liver lesions. However, DCE-MRI using Gd-EOB-DTPA has some problems with arterial phase images. Radial volumetric imaging breath-holding examination (r-VIBE) with k-space weighted image contrast reconstruction (KWIC), which is a modification of Cartesian VIBE (c-VIBE), is a new 3D-gradient echo sequence with a number of advantages compared with c-VIBE, including lower motion sensitivity. This study was performed to evaluate image contrast, blurring, and temporal phase division effects of r-VIBE in comparison with c-VIBE. Image contrast using diluted Gd-EOB-DTPA aqueous solution showed no significant difference between r-VIBE and c-VIBE. Imaging was performed with r-VIBE and c-VIBE during injection of a Gd-EOB-DTPA solution into a serpentine tube. r-VIBE showed a smaller half-width of the signal intensity profile of the tube and less image artifacts by blurring when compared to c-VIBE. The arrival times and durations of the maximum signal strengths of r-VIBE and c-VIBE images during injection of Gd-EOB-DTPA solution into the tube were almost identical. r-VIBE improved the temporal resolution without degradation of liver DCE-MRI using Gd-EOB-DTPA.

Noninvasive Assessment of Liver Fibrosis in Patients with Chronic Hepatitis B or C by Contrast-Enhanced Magnetic Resonance Imaging

Background and Aim. To develop a noninvasive magnetic resonance imaging (MRI) method for evaluation of liver fibrosis. We evaluate the utility of hepatocyte-phase Gadoxetate disodium-enhanced magnetic resonance (MR) imaging in staging hepatic fibrosis and compare it with histological analysis as the reference standard (liver biopsy). Methods. Prospective cohort of 78 patients, who received Gadoxetate disodium dynamic contrast-enhanced MRI (DCE-MRI), were divided into three groups. The first group (n=19) was a control group of healthy individuals without liver injury and remaining 59 subjects were chronic hepatitis B and C patients who underwent liver biopsy. These patients were divided into the mild fibrosis F1-F2 (n=32) and advanced fibrosis F3-F4 (n=27) groups. Patients were examined by generated DCE-MRI in 20th minute. Variables such as liver surface changes, homogeneities, and quantitative contrast liver/spleen ratio-Q-LSCR were evaluated and these results were consequently compared between the three groups. Results. Gd-EOB-DTPA contrast-enhanced dynamic liver MRI examination (DCE-MRI) can in the 20th minute differentiate mild stage of liver fibrosis (F1-F2) from severe stage of liver fibrosis (F3-F4) on the basis of liver surface changes, homogeneities, and quantitative contrast liver/spleen ratio-Q-LSCR. Diagnostic MRI criteria were created and named MRI Triple test. This test correctly identified 96% of patients with F3-F4 fibrosis and 91% of patients with the F1-F2 fibrosis in the liver biopsy. This test correctly identified 42,1% of patients in the control group (presumed F0 fibrosis without liver disease). Spearman's rank correlation coefficient (r = 0,86, P < .001) confirmed high agreement of biopsy and MR Triple test. MR Triple test's sensitivity was 96.30% (95%CI 81.03% to 99.91%), specificity 90.62% (95%CI 74.98% to 98.02%), positive predictive value 89.66% (95%CI 74.64% to 96.23%), and negative predictive value 96.67% (95%CI 80.86% to 99.50%) for discrimination between F3-4 and F1-2 fibrosis on liver biopsy. Conclusions. Gd-EOB-DTPA contrast-enhanced MRI liver examination in 20th minute is able to reliably differentiate mild stage of liver fibrosis (F1-F2) from severe stage fibrosis (F3-F4) on the basis of Triple test (liver surface changes, homogeneities, and quantitative contrast liver/spleen ratio-Q-LSCR).

A new formula to calculate the resection limit in hepatectomy based on Gd-EOB-DTPA-enhanced magnetic resonance imaging

Background and aim

Dynamic magnetic resonance imaging with gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (EOB-MRI) can be used not only to detect liver tumors but also to estimate liver function. The aim of this study was to establish a new EOB-MRI-based formula to determine the resection limit in patients undergoing hepatectomy.

Methods

Twenty-eight patients with a normal liver (NL group) and five with an unresectable cirrhotic liver (UL group) who underwent EOB-MRI were included. Standardized liver function (SLF) was calculated based on the signal intensity (SI), the volume of each subsegment (S1–S8), and body surface area. A formula defining the resection limit was devised based on the difference in the SLF values of patients in the NL and UL groups. The formula was validated in 50 patients who underwent EOB-MRI and hepatectomy.

Results

The average SLF value in the NL and UL groups was 2038 and 962 FV/m², respectively. The difference (1076 FV/m²) was consistent with a 70% in resection volume. Thus, the resection limit for hepatectomy was calculated as a proportion of 70%: 70×(SLF−962)/1076 (%). The one patient who underwent hepatectomy over the resection limit died due to liver failure. In other 49 patients, in whom the resection volume was less than the resection limit, procedures were safely performed.

Conclusions

Our formula for resection limit based on EOB-MRI can improve the safety of hepatectomy.

Technical Note: Evaluation of kV CBCT enhancement using a liver-specific contrast agent for stereotactic body radiation therapy image guidance

PURPOSE

To evaluate possible use for cone-beam computed tomography (CBCT) guidance, this phantom study evaluated the contrast enhancement provided by Gadoxetate Disodium (Primovist^® CAN/EU, or Eovist^® USA, Bayer Healthcare, Leverkusen, Germany), a contrast agent that is taken up selectively by liver cells and is retained for up to an hour. Image quality from CBCT was benchmarked against helical fan-beam computed tomography for two phantom geometries.

METHODS AND MATERIALS

Concentrations were diluted to 0.0125-0.1 mmol per kilogram of body weight (mmol/kg) corresponding to expected physiological concentrations in the liver. Kilovoltage CBCT imaging parameters of x-ray tube potential, current, and filtration were investigated using clinically available options on a TrueBeam STx linear accelerator CBCT platform. Two phantoms were created, a cylindrical idealized imaging geometry and an ellipsoidal more realistic abdominal geometry. All parameters were optimized according to the contrast-to-noise ratio (CNR) image quality metric, as a function of concentration, following the Rose criterion for CNR.

RESULTS

Acceptable CNR was defined as greater than or equal to three, in accordance with the Rose criterion for CNR. These were found in a range of expected liver concentrations of 0.025-0.1 mmol/kg for a tube potential of 100 kVp, half-fan bowtie filtration and tube currents giving exposures between 2025 and 5085 mAs. Linear correlations were found for all CNR as a function of concentration, in agreement with the literature.

CONCLUSION

Based on this phantom study, with appropriate selection of imaging protocol, Gadoxetate Disodium may provide useful liver CBCT enhancement at physiologically achievable liver concentrations.

Diagnostic performance of Gd-EOB-DTPA-enhanced MRI for evaluation of liver dysfunction: a multivariable analysis of 3T MRI sequences

OBJECTIVE

The aim of this study was to evaluate the diagnostic performance of a multiparametric gadolinium ethoxybenzyl-diethylenetriaminepentaacetic acid (Gd-EOB-DTPA)-enhanced MRI examination for the estimation of liver dysfunction classified by the Model for End-Stage Liver Disease (MELD) score.

RESULTS

Liver dysfunction can be assessed by different methods. In a logistic regression analysis, T1- and T2-weighted images were affected by impaired liver function. In the assessment of liver dysfunction, the reduction rate in T1 mapping sequences showed a significant correlation in simple and multiple logistic regression.

CONCLUSION

Changes in Gd-EOB-DTPA-enhanced MRI between plain images and images obtained during the hepatobiliary phase allowed good prediction of liver dysfunction, especially when using T1 mapping sequences.

MATERIALS AND METHODS

A total of 199 patients underwent contrast-enhanced MRI with a hepatocyte-specific contrast agent at 3T. In the multivariable analysis, the full range of available MRI sequences was used to estimate the liver dysfunction of patients with various MELD scores.

Conspicuity of Malignant Liver Tumors on Diffusion-Weighted Imaging With Short tau Inversion Recovery After Gadolinium Ethoxybenzyl Diethylenetriaminepentaacetic Acid Administration

BACKGROUND

Diffusion-weighted imaging (DWI) has been used for the detection and characterization of liver tumors because it has excellent contrast resolution. DWI using short tau inversion recovery (STIR) can improve tumor-to-liver contrast after gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (Gd-EOB-DTPA) administration that shortens the T₁ relaxation of liver parenchyma.

PURPOSE

To quantitatively and qualitatively compare the conspicuity of malignant liver tumors on DWI after Gd-EOB-DTPA administration between STIR and chemical shift selective (CHESS) sequences.

STUDY TYPE

Single-institution retrospective study.

SUBJECTS

Fifty-seven patients with histologically confirmed malignant liver tumors were evaluated.

FIELD STRENGTH/SEQUENCE

Low b-value DWIs with STIR and CHESS sequences 18-20 minutes after Gd-EOB-DTPA administration were acquired at 1.5T.

ASSESSMENT

Tumor contrast-to-noise ratio (CNR) and visual grade of tumor conspicuity on DWI between STIR and CHESS sequences were compared.

STATISTICAL TESTS

Paired Student's t-test and the Wilcoxon signed rank-test were applied. P < 0.05 was considered statistically significant.

RESULTS

The mean tumor CNR and visual grade of tumor conspicuity on DWI were significantly higher for STIR than for CHESS (both P < 0.001). Regardless of the presence of chronic liver disease, the mean CNR (normal liver 33.5 ± 19.8 vs. 15.7 ± 12.2, P < 0.001; chronic liver disease 19.6 ± 11.0 vs. 9.2 ± 7.8, P < 0.001) and the visual conspicuity grade (normal liver 3.36 ± 0.64 vs. 2.56 ± 0.77, P < 0.001; chronic liver disease 2.94 ± 0.80 vs. 2.25 ± 0.84, P = 0.001) were significantly higher for STIR than for CHESS. Mean CNR and the visual conspicuity grade were also significantly higher for STIR than for CHESS in patients with hepatocellular carcinomas (CNR 18.1 ± 10.5 vs. 8.8 ± 7.2, P < 0.001; visual grade 2.88 ± 0.83 vs. 2.22 ± 0.87, P = 0.001) or metastases (CNR 35.0 ± 19.3 vs. 16.2 ± 13.1, P < 0.001; visual grade 3.45 ± 0.51 vs. 2.59 ± 0.73, P < 0.001).

DATA CONCLUSION

DWI using STIR may be more helpful for depicting malignant liver tumors after Gd-EOB-DTPA administration compared with DWI using CHESS.

LEVEL OF EVIDENCE

3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:565-573.

Peri-tumoral hyperintensity on hepatobiliary phase of gadoxetic acid-enhanced MRI in hepatocellular carcinomas: correlation with peri-tumoral hyperplasia and its pathological features

PURPOSE

Peri-tumoral hyperintensity (P-hyperintensity) is occasionally seen in hepatocellular carcinoma (HCC) on the hepatobiliary (HB) phase of gadoxetic acid-enhanced MRI (EOB-MRI). A recent study reported peri-tumoral hyperplasia (P-hyperplasia) associated with over-expression of glutamine synthetase (GS) in HCC or metastatic carcinoma. The aim of this study was to analyze the correlation between P-hyperintensity on the HB phase and GS expression indicating P-hyperplasia and reveal its pathological features.

METHODS

Seventy-seven surgically resected HCCs from 68 patients were analyzed. The grade of P-hyperintensity on HB phase was divided according to the degree of the peri-tumoral hyperintense signal: grade 0 (no P-hyperintensity), grade 1 (less than 50% of the tumor border), grade 2 (50%-80%), grade 3 (80%-100%). Immunohistochemical staining for GS and organic anion transporter polypeptides (OATP)1B3 was performed. The relationships among P-hyperplasia (peri-tumoral GS expression) and OATP1B3 expression, P-hyperintensity, and pathological features of the tumor were analyzed.

RESULTS

Thirty-four HCCs were classified as P-hyperintensity grade 0, 29 HCCs as grade 1,10 nodules as grade 2, and 4 HCCs as grade 3. P-hyperplasia was observed in 3/34 (8.8%) P-hyperintensity grade 0, 16/29 (55.2%) grade 1, 9/10 (90%) grade 2, and 4/4 (100%) grade 3. The incidence of P-hyperplasia was significantly increased in P-hyperintensity grades 1-3 compared with grade 0 (p < 0.0001). Hepatocytes in all P-hyperplasia sites demonstrated definite OATP1B3 expression. Microscopic hepatic venous invasion was significantly increased in P-hyperintensity-positive HCCs compared with negative HCCs (p = 0.0017).

CONCLUSIONS

P-hyperintensity on HB phase in HCC may indicate p-hyperplasia with GS and OATP1B3 expression and a higher incidence of microscopic hepatic venous invasion.

Prediction of Posthepatectomy Liver Failure: MRI With Hepatocyte-Specific Contrast Agent Versus Indocyanine Green Clearance Test

OBJECTIVE

The objective of our study was to identify whether quantitative measurements from gadoxetic acid-enhanced MRI are useful for predicting posthepatectomy liver failure (PHLF) in patients with hepatocellular carcinoma (HCC) compared with and in combination with future remnant liver volume (FRLV) and an indocyanine green (ICG) clearance test.

MATERIALS AND METHODS

Preoperative gadoxetic acid-enhanced MR images were retrospectively evaluated in 73 patients who underwent anatomic liver resection for HCC between 2011 and 2013. For quantitative measurement of hepatocyte function, relative liver enhancement (RLE) and remnant hepatocyte uptake index (rHUI) were measured using hepatobiliary phase MR images. FRLV was determined using measurements from preoperative CT scans. Univariate and multivariate analyses of measurements from gadoxetic acid-enhanced MRI, ICG clearance tests, and FRLV for finding predictors of PHLF were performed. To compare the diagnostic performance of predictors, ROC analyses were also performed.

RESULTS

Eighteen (25%) of 73 patients met the criteria for PHLF. Univariate analysis revealed that all measurements related to MRI including RLE, rHUI, ICG clearance, and FRLV were significantly associated with PHLF. Multivariate analysis showed that RLE, FRLV, ICG-plasma disappearance rate (ICG-PDR), rHUI, and rHUI corrected for body weight (rHUI-BW) were independent predictors of PHLF (p = 0.011, p = 0.034, p = 0.003, p < 0.001, and p = 0.001, respectively). In ROC analyses, AUCs of rHUI and rHUI-BW were larger than those of other independent predictors; the differences were statistically significant (for rHUI-BW vs RLE, ICG-PDR, and FRLV, p = 0.016, 0.007, and 0.046, respectively; for rHUI vs RLE and ICG-PDR, p = 0.045 and 0.016, respectively).

CONCLUSION

Measurements from gadoxetic acid-enhanced MRI predicted PHLF better than the ICG clearance test in patients with HCC who underwent hepatectomy.

Measuring hepatic functional reserve using T1 mapping of Gd-EOB-DTPA enhanced 3T MR imaging: A preliminary study comparing with 99mTc GSA scintigraphy and signal intensity based parameters

PURPOSE

To determine the utility of liver T1-mapping on gadolinium-ethoxybenzyl-diethylenetriamine-pentaacetic acid (Gd-EOB-DTPA) enhanced magnetic resonance (MR) imaging for the measurement of liver functional reserve compared with the signal intensity (SI) based parameters, technetium-99m-galactosyl serum albumin (^99mTc-GSA) scintigraphy and indocyanine green (ICG) clearance.

MATERIALS AND METHODS

This retrospective study included 111 patients (Child-Pugh-A 90; -B 21) performed with both Gd-EOB-DTPA enhanced liver MR imaging and ^99mTc-GSA (76 patients with ICG). Receiver operating characteristic (ROC) curve analysis was performed to compare diagnostic performances of T1-relaxation-time parameters [pre-(T1pre) and post-contrast (T1hb) Gd-EOB-DTPA], SI based parameters [relative enhancement (RE), liver-to-muscle-ratio (LMR), liver-to-spleen-ratio (LSR)] and ^99mTc-GSA scintigraphy blood clearance index (HH15)] for Child-Pugh classification. Pearson's correlation was used for comparisons among T1-relaxation-time parameters, SI-based parameters, HH15 and ICG.

RESULTS

A significant difference was obtained for Child-Pugh classification with T1hb, ΔT1, all SI based parameters and HH15. T1hb had the highest AUC followed by RE, LMR, LSR, ΔT1, HH15 and T1pre. The correlation coefficients with HH15 were T1pre 0.22, T1hb 0.53, ΔT1 -0.38 of T1 relaxation parameters; RE -0.44, LMR -0.45, LSR -0.43 of SI-based parameters. T1hb was highest for correlation with HH15. The correlation coefficients with ICG were T1pre 0.29, T1hb 0.64, ΔT1 -0.42 of T1 relaxation parameters; RE -0.50, LMR -0.61, LSR -0.58 of SI-based parameters; 0.64 of HH15. Both T1hb and HH15 were highest for correlation with ICG.

CONCLUSION

T1 relaxation time at post-contrast of Gd-EOB-DTPA (T1hb) was strongly correlated with ICG clearance and moderately correlated HH15 with ^99mTc-GSA. T1hb has the potential to provide robust parameter of liver functional reserve.

Brief communication (Original). Correlation between liver signal intensity in hepatobiliary phase of Gd-EOB-DTPA enhancement and liver function reserves

Background: Gadolinium diethylenetriamine-pentaacetic acid (Gd-EOB-DTPA) is a developed agent with preferential uptake by hepatocytes. A rapid and specific hepatocyte uptake with biliary excretion was observed of approximately 50% of the injected dose. The amount of contrast uptake is thought to be related to reserve liver function.

Objectives: To evaluate correlation between liver signal intensity in the hepatobiliary phase of Gd-EOB-DTPA and reserved liver function by using the model score for end-stage liver disease (MELD).

Methods:All patients who underwent magnetic resonance (MR) imaging with Gd-EOB-DTPA were retrospectively collected. The patients with serum creatinine level higher than 1.5 mg/dL or patients without available data to estimate MELD score were excluded. Thirty-six patients were enrolled. A signal-to-noise ratio (SNR) in the liver parenchyma on a fat-suppressed three dimensional fast spoiled-gradient recalled echo sequence images before and 20 minutes after contrast injection were measured and calculated on PACS by two radiologists. The MELD score was determined and interobserver reliability was estimated.

Results: Among 36 patients, we found a negative relationship between the percentage enhancement and the MELD score (P < 0.01, r = 0.545). The SNR at 20 minutes after Gd-EOB-DTPA injection also had a negative relationship with the MELD score with statistical significance (P < 0.01, r = 0.460). Interobserver reliability was 0.675.

Conclusion: The percentage enhancement in hepatobiliary phase of Gd-EOB-DTPA can predict reserved liver function.

Quantitative analysis of gadoxetic acid-enhanced magnetic resonance imaging predicts histological grade of hepatocellular carcinoma

OBJECTIVE

To confirm the histological grade of hepatocellular carcinoma (HCC) by gadoxetic acid-enhanced MRI.

METHODS

Ninety-five HCC patients underwent gadoxetic acid-enhanced MRI before surgical intervention. The correlations among the signal absolute enhancement, contrast enhancement ratio (CER) and tumor histological grade were analyzed.

RESULTS

The correlation between CER of tumor-to-liver and the grades of tumor differentiation is the most significant negative. The k-value for the CER of tumor-to-liver and histopathologic analysis is 0.62, which gives evidence of good agreement.

CONCLUSION

The quantitative analysis of gadoxetic acid-enhanced MRI can predict the histological grades of small HCCs.

Hepatocellular carcinoma detection: diagnostic performance of a simulated abbreviated MRI protocol combining diffusion-weighted and T1-weighted imaging at the delayed phase post gadoxetic acid

PURPOSE

The purpose of this study was to evaluate the diagnostic performance of a "simulated" abbreviated MRI (AMRI) protocol using diffusion-weighted imaging (DWI) and T1-weighted (T1w) imaging obtained at the hepatobiliary phase (HBP) post gadoxetic acid injection alone and in combination, compared to dynamic contrast-enhanced (CE)-T1w imaging for the detection of hepatocellular carcinoma (HCC).

METHODS

This was an IRB approved HIPAA compliant retrospective single institution study including patients with liver disease who underwent gadoxetic acid-enhanced MRI for HCC diagnosis. Three independent observers assessed 2 sets of images (full CE-set and AMRI including DWI+T1w-HBP). Diagnostic performance of T1w-HBP and DWI alone and in combination was compared to that of CE-set. All imaging sets included unenhanced T1w and T2w sequences. A preliminary analysis was performed to assess cost savings of AMRI protocol compared to a full MRI study.

RESULTS

174 patients including 62 with 80 HCCs were assessed. Equivalent per-patient sensitivity and negative predictive value (NPV) were observed for DWI (85.5% and 92.2%, pooled data) and T1w-HBP (89.8% and 94.2%) (P = 0.1-0.7), while these were significantly lower for the full AMRI protocol (DWI+T1w-HBP, 80.6% and 80%, P = 0.02) when compared to CE-set (90.3% and 94.9%). Higher specificity and positive predictive value were observed for CE-set vs. AMRI (P = 0.02). The estimated cost reduction of AMRI versus full MRI ranged between 30.7 and 49.0%.

CONCLUSION

AMRI using DWI and T1w-HBP has a clinically acceptable sensitivity and NPV for HCC detection. This could serve as the basis for a future study assessing AMRI for HCC screening and surveillance.

Comparison of Contrast-Enhanced Ultrasound and Gadolinium-Ethoxybenzyl-Diethylenetriamine Pentaacetic Acid-Enhanced MRI for the Diagnosis of Macroscopic Type of Hepatocellular Carcinoma

OBJECTIVE

We compared the efficacy of contrast-enhanced ultrasound sonography (CEUS) with sonazoid and gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced MRI for the assessment of macroscopic classification of nodular hepatocellular carcinoma (HCC).

METHODS

Seventy-seven consecutive patients with 79 surgically resected HCCs who underwent both preoperative CEUS and Gd-EOB-DTPA-enhanced MRI were enrolled in this retrospective study. Based on the macroscopic diagnosis of resected specimens, nodules were categorized into the simple nodular (SN) and non-SN type HCC. Two hepatologists independently assessed image datasets of the post-vascular phase of CEUS and hepatobiliary phase of Gd-EOB-DTPA-enhanced MRI to compare their diagnostic performance.

RESULTS

Gd-EOB-DTPA-enhanced MRI enabled the evaluation of macroscopic classification in a significantly larger number of nodules than CEUS (78/79 (98.7%) vs. 70/79 (88.6%), p < 0.05). Of 70 nodules that could be evaluated by both modalities, 41 and 29 nodules were pathologically categorized as SN and non-SN, respectively. The areas under the receiver operating characteristic curve (AUC) for non-SN did not differ between CEUS and Gd-EOB-DTPA-enhanced MRI (reader 1: 0.748 for CEUS, 0.808 for MRI; reader 2: 0.759 for CEUS, 0.787 for MRI). The AUC of combined CEUS and Gd-EOB-DTPA-enhanced MRI for SN HCC was 0.855 (reader 1) and 0.824 (reader 2), indicating higher AUC values for the combined modalities.

CONCLUSIONS

The diagnostic performance for macroscopic classification of nodular HCC of CEUS was comparable with that of Gd-EOB-DTPA-enhanced MRI, although some HCCs could not be evaluated by CEUS owing to lower detectability. The combination of the 2 modalities had a more accurate diagnostic performance.

Benign Hepatocellular Nodules: Hepatobiliary Phase of Gadoxetic Acid-enhanced MR Imaging Based on Molecular Background

Gadoxetic acid is a contrast agent for magnetic resonance (MR) imaging with hepatocyte-specific properties and is becoming increasingly important in detection and characterization of hepatocellular carcinoma and benign hepatocellular nodules, including focal nodular hyperplasia (FNH), nodular regenerative hyperplasia (NRH), hepatocellular adenoma (HCA), and dysplastic nodule. In these hepatocellular nodules, a positive correlation between the grade of membranous uptake transporter organic anion-transporting polypeptide (OATP) 1B3 expression and signal intensity in the hepatobiliary (HB) phase has been verified. In addition, it has been clarified that OATP1B3 expression is regulated by activation of β-catenin and/or hepatocyte nuclear factor 4α. On the other hand, recent studies have also revealed some of the background molecular mechanisms of benign hepatocellular nodules. FNH commonly shows iso- or hyperintensity in the HB phase with equal or stronger OATP1B3 expression, with map-like distribution of glutamine synthetase (a target of Wnt/β-catenin signaling) and OATP1B3 expression. NRH shows doughnut-like enhancement with hypointensity in the central portion in the HB phase with OATP1B3 expression. The majority of HCAs show hypointensity in the HB phase, but β-catenin-activated HCA exclusively demonstrates iso- or hyperintensity with increased expression of nuclear β-catenin, glutamine synthetase, and OATP1B3. Dysplastic nodule commonly shows iso- or hyperintensity in the HB phase with similar to increased OATP1B3 expression, but one-third of high-grade dysplastic nodules can be demonstrated as a hypointense nodule with decreased OATP1B3 expression. Knowledge of these background molecular mechanisms of gadoxetic acid-enhanced MR imaging is important not only for precise imaging diagnosis but also understanding of the pathogenesis of benign hepatocellular nodules. ^©RSNA, 2016.

Application of magnetic resonance imaging-based liver function assessment in hepatic surgery

Liver function is often assessed before liver surgery for surgical planning and prognosis prediction. The commonly used methods are not accurate as desired and cannot fully meet the clinical requirements. The advancement of imaging technology and contrast agents has made it possible to use liver-specific contrast agent-enhanced magnetic resonance imaging (MRI) to estimate the total and segmental liver function. Herein, we summarize several evaluation methods currently used and their shortcomings, and describe the principle of hepatic tissue-specific MRI contrast agents, a variety of relevant methods and the latest technological advances. The hepatic tissue-specific contrast-based MRI holds a promise to become a quantitative method for preoperative evaluation of liver function, and achieve the precise assessment of liver function that is needed for precise hepatic surgery.

Usefulness of breath-hold inversion recovery-prepared T1-weighted two-dimensional gradient echo sequence for detection of hepatocellular carcinoma in Gd-EOB-DTPA-enhanced MR imaging

The aim is to evaluate the diagnostic performance and the added value of breath-hold inversion recovery-prepared T1-weighted two-dimensional gradient echo (IR-2D-GRE) sequence for detection of hepatocellular carcinoma (HCC) in patients with insufficient liver parenchymal enhancement during the hepatobiliary phase (HBP) of Gd-EOB-DTPA-enhanced magnetic resonance imaging (MRI). Seventeen patients with a quantitative liver-to-spleen contrast ratio of ≤1.5 on HBP images and 36 HCCs were included. Liver-to-lesion contrast ratios on HBP images obtained with IR-2D-GRE sequence were significantly higher than those with three-dimensional gradient echo sequence. The addition of IR-2D-GRE sequence during HBP of Gd-EOB-DTPA-enhanced MRI yielded higher diagnostic accuracy and improved sensitivity.

Capecitabine-related liver lesions: sinusoidal dilatation mimicking liver metastasis

A 30‐year‐old lady treated with capecitabine for primary colon adenocarcinoma developed liver lesions suspicious for metastasis. Liver biopsies showed sinusoidal dilatation thought to be secondary to capecitabine. This case highlights the importance of differentiating between benign and malignant liver lesions during cancer surveillance preventing unnecessary liver resections for benign disease.

MR liver imaging with Gd-EOB-DTPA: The need for different delay times of the hepatobiliary phase in patients with different liver function

PURPOSE

To determine the optimal hepatobiliary delay time after Gd-EOB-DTPA injection for lesion characterization in cirrhosis patients with different liver function.

MATERIALS AND METHODS

Ninety consecutive patients with liver cirrhosis who underwent Gd-EOB-DTPA-enhanced MRI for the evaluation of known or suspected focal liver lesions were enrolled in this retrospective study. The patients were divided into Child-Pugh A, B and C groups depending on their liver function through the Child-Pugh classification. Hepatobiliary phase images obtained at 5, 10, 15, and 20min were assessed in each group by the following items: parenchymal enhancement, contrast agent excretion into the bile ducts and ureter, and contrast- and signal-to-noise ratios for lesions.

RESULTS

In the Child-Pugh A group, parenchymal enhancement increased significantly from 5min to 15min (P<0.05), and stabilized at 20min (P=0.22). However, there was no significant difference in parenchymal enhancement among all of the hepatobiliary phases in the Child-Pugh B and C groups. The biliary contrast agent excretion was first observed before 20min in all of the patients in the Child-Pugh A group, at 20min in 4 patients (25%) in the Child-Pugh B group, and after 20min in 11 patients (78.6%) in the Child-Pugh C group. The numbers of patients whose urethral contrast agent excretion was first observed at 5min in the Child-Pugh A, B and C groups were 38 (63.3%), 12 (75.0%) and 11 (78.6%), respectively. The CNR of the lesions increased significantly (P<0.05), up to 15min after enhancement without a further increase at 20min in the Child-Pugh A group; however, no significant change was found from 5min to 20min in the Child-Pugh B and C groups. For the SNR of lesions, there was no significant difference at 5, 10, 15 and 20min in all of the groups.

CONCLUSIONS

A delay time of 15min for the hepatobiliary phase was sufficient for patients with mild liver dysfunction who were classified as Child-Pugh A. Nevertheless, for the patients with moderate or severe liver dysfunction who were classified as Child-Pugh B or C, a delay time longer than 5min is meaningless for lesion characterization.

Gd-EOB enhanced MRI T1-weighted 3D-GRE with and without elevated flip angle modulation for threshold-based liver volume segmentation

BACKGROUND

Despite novel software solutions, liver volume segmentation is still a time-consuming procedure and often requires further manual optimization. With the high signal intensity of the liver parenchyma in Gd-EOB enhanced magnetic resonance imaging (MRI), liver volume segmentation may be improved.

PURPOSE

To evaluate the practicability of threshold-based segmentation of the liver volume using Gd-EOB-enhanced MRI including a customized three-dimensional (3D) sequence.

MATERIAL AND METHODS

A total of 20 patients examined with Gd-EOB MRI (hepatobiliary phase T1-weighted (T1W) 3D sequence [VIBE]; flip angle [FA], 10° and 30°) were enrolled in this retrospective study. The datasets were independently processed by two blinded observers (O1 and O2) in two ways: manual (man) and threshold-based (thresh; study method) segmentation of the liver each followed by an optimization step (man+opt and thresh+opt; man+opt [FA10°] served as reference method). Resulting liver volumes and segmentation times were compared. A liver conversion factor was calculated in percent, describing the non-hepatocellular fraction of the total liver volume, i.e. bile ducts and vessels.

RESULTS

Thresh+opt (FA10°) was significantly faster compared to the reference method leading to a median volume overestimation of 4%/8% (P < 0.001). Using thresh+opt (FA30°), segmentation was even faster (P < 0.001) and even reduced median volume deviation of 0%/2% (O1/O2; both P > 0.2). The liver conversion factor was found to be 10%.

CONCLUSION

Threshold-based liver segmentation employing Gd-EOB-enhanced hepatobiliary phase standard T1W 3D sequence is accurate and time-saving. The performance of this approach can be further improved by increasing the FA.

Liver fibrosis and Gd-EOB-DTPA-enhanced MRI: A histopathologic correlation

Gadolinium ethoxybenzyl-diethylenetriaminepentaacetic acid (Gd-EOB-DTPA) is a hepatocyte-specific MRI contrast agent. Because the hepatic uptake of Gd-EOB-DTPA depends on the integrity of the hepatocyte mass, this uptake can be quantified to assess liver function. We report the relationship between the extent of Gd-EOB-DTPA uptake and the degree of liver fibrosis. T1-weighted volume-interpolated breath-hold examination (VIBE) sequences with fat suppression were acquired before and 20 minutes after contrast injection. Strong correlations of the uptake characteristics of Gd-EOB-DTPA with the relative enhancement (RE) of the liver parenchyma and the grade of fibrosis/cirrhosis, classified using the Ishak scoring system, were observed. The subdivisions between the grades of liver fibrosis based on RE were highly significant for all combinations, and a ROC revealed sensitivities ≥82% and specificities ≥87% for all combinations. MR imaging is a satisfactorily sensitive method for the assessment of liver fibrosis/cirrhosis.

Validation of 10-Minute Delayed Hepatocyte Phase Imaging with 30° Flip Angle in Gadoxetic Acid-Enhanced MRI for the Detection of Liver Metastasis

Objectives

To compare 10-minute delayed hepatocyte phase imaging using a 30° flip angle (10min-FA30) and 20-minute hepatocyte phase imaging using a 10° FA (20min-FA10) in gadoxetic acid-enhanced MRI of patients with possible liver metastases, regarding lesion-to-liver contrast-to-noise ratio (CNR) and focal hepatic lesion (FHL) detection to evaluate whether 10min-FA30 would be superior to 20min-FA10.

Materials and Methods

Eighty-three patients with 248 liver metastases and 78 benign FHLs who underwent gadoxetic acid-enhanced MRI with 10min-FA30 and 20min-FA10 were enrolled. Lesion-to-liver CNRs were compared between the two image groups. Two radiologists independently assessed the presence of FHLs using a four-point scale and detection sensitivity was calculated.

Results

The mean CNR for liver metastases on the 10min-FA30 (248.5 ± 101.6) were significantly higher than that of the 20min-FA10 (187.4 ± 77.4) (p < 0.001). The mean CNR difference between the two image groups was 61.2 ± 56.8. There was no significant difference in detection sensitivity of FHLs for two readers between 10min-FA30 (mean 97.7%) and 20min-FA10 (mean 97.9%), irrespective of the lesion size or malignancy.

Conclusion

10min-FA30 yielded higher CNR with similar sensitivity compared to 20min-FA10. This finding indicates that 10min-FA30 can potentially replace 20min-FA10 with higher diagnostic performance and save 10 minutes of time.

Prospective diagnostic test accuracy comparison of computed tomography during arterial portography and Primovist magnetic resonance imaging in the pre-operative assessment of colorectal cancer liver metastases

OBJECTIVES

To assess and compare the accuracy and inter-observer agreement for the detection of liver lesions using Primovist magnetic resonance imaging (pMRI) and computed tomography during arterial portography (CTAP).

METHODS

Patients evaluated at St George Hospital Liver Unit for colorectal liver metastases (CRCLM) underwent CTAP as part of standard staging. pMRI was added to the pre-operative assessment. Two radiologists reported CTAP and two reported pMRI. The sensitivity and specificity of CTAP and pMRI were calculated using histopathology as the gold standard.

RESULTS

Complete data were available for 62 patients corresponding to 219 lesions confirmed on histopathology. Agreement on the detection of lesions between the two radiologists that reported pMRI was higher than for CTAP (Kappa = 0.80 versus 0.74). Specificity of lesion detection for pMRI was 0.88 and 0.83 for CTAP (P = 0.112). Sensitivity for pMRI was 0.83 and 0.81 for CTAP. For patients who had chemotherapy before evaluation, pMRI had a significantly higher specificity than CTAP (0.79 versus 0.63, P = 0.011).

CONCLUSIONS

pMRI is less invasive, has a good inter-observer agreement, has comparable sensitivity and specificity to CTAP in the pre-chemotherapy population and demonstrates better specificity in patients assessed post-chemotherapy. pMRI is a valid alternative to CTAP in the assessment of CRCLM.

Clinical utility of gadoxetate disodium-enhanced hepatic MRI for stereotactic body radiotherapy of hepatocellular carcinoma

PURPOSE

To investigate the utility of gadoxetate disodium-enhanced hepatic MRI (EOB-MRI) for stereotactic body radiotherapy (SBRT) to treat hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

We divided 30 HCC patients who underwent SBRT into group A (no change in their Child-Pugh score 6 months post-SBRT) and group B (increased score 6 months post-SBRT). EOB-MRI was performed before and 6 months after SBRT. We calculated the liver-spleen contrast (LSC) ratio for each radiation dose area on hepatobiliary phase scans (LSCbefore using images obtained before SBRT and LSCafter using images acquired after SBRT) and the weighted LSC (W-LSC) as: [(mean LSCbefore (0-30 Gy) × liver volume (0-30 Gy) + mean LSCbefore (30 Gy-) × liver volume (30 Gy-))/total liver volume]. Then we compared the W-LSC, percentage of the liver volume exposed to >20 Gy (V20), and mean liver dose in the two groups.

RESULTS

The LSCafter at 48, 40, and 30 Gy to the liver was statistically lower than the unirradiated area of the liver (p < 0.01). Univariate analysis showed that only W-LSC was significantly associated with group B (p = 0.02).

CONCLUSION

W-LSC was a useful parameter for predicting changes in hepatic function after SBRT.

Preoperative estimation of future remnant liver function following portal vein embolization using relative enhancement on gadoxetic acid disodium-enhanced magnetic resonance imaging

Objective

To retrospectively evaluate relative enhancement (RE) in the hepatobiliary phase of gadoxetic acid disodium-enhanced magnetic resonance (MR) imaging as a preoperative estimation of future remnant liver (FRL) function in a patients who underwent portal vein embolization (PVE).

Materials and Methods

In 53 patients, the correlation between the indocyanine green clearance (ICG-K) and RE imaging was analyzed before hepatectomy (first analysis). Twenty-three of the 53 patients underwent PVE followed by a repeat RE imaging and ICG test before an extended hepatectomy and their results were further analyzed (second analysis). Whole liver function and FRL function were calculated on the MR imaging as follows: RE x total liver volume (RE Index) and FRL-RE x FRL volume (Rem RE Index), respectively. Regarding clinical outcome, posthepatectomy liver failure (PHLF) was evaluated in patients undergoing PVE.

Results

Indocyanine green clearance correlated with the RE Index (r = 0.365, p = 0.007), and ICG-K of FRL (ICG-Krem) strongly correlated with the Rem RE Index (r = 0.738, p < 0.001) in the first analysis. Both the ICG-Krem and the Rem RE Index were significantly correlated after PVE (r = 0.508, p = 0.013) at the second analysis. The rate of improvement of the Rem RE Index from before PVE to after PVE was significantly higher than that of ICG-Krem (p = 0.014). Patients with PHLF had a significantly lower Rem RE Index than patients without PHLF (p = 0.023).

Conclusion

Relative enhancement imaging can be used to estimate FRL function after PVE.

The added value of PET/Ce-CT/DW-MRI fusion in assessment of hepatic focal lesions: PET/Ce-CT/DW-MRI fusion in hepatic focal lesion

INTRODUCTION

The liver hosts a variety of benign and malignant tumors. Accurate diagnosis can be challenging in certain cases, especially in patients with a history of malignancy or in those with underlying liver pathology, such as cirrhosis.

OBJECTIVES

To evaluate the added clinical value of multi-modality liver imaging utilizing PET/Ce-CT/DW-MRI for characterization of hepatic focal lesions (HFL) and compare it with each diagnostic modality when interpreted alone.

METHODS

The study included 35 patients with HFL. They were 7 females & 28 males; their age ranged from 41 to 78years, all patients underwent PET/Ce-CT and DW-MRI scans. Ce-CT, PET and DW-MR images were reviewed independently, and then combined PET/Ce-CT, PET/DW-MRI and PET/Ce-CT/DW-MRI scans were analyzed. The results were correlated with histopathology or clinical/imaging follow-up.

RESULTS

The 35 patients had 98 focal lesions. Fifty-three lesions were finally diagnosed as primary hepatocellular carcinoma, 18 lesions were metastases, 7 lesions were lymphoma and 20 lesions were benign. On a patient based analysis; the sensitivity, specificity, PPV, NPV and accuracy were 100%, 67%, 94%, 100% and 94% for PET/Ce-CT compared to 97%, 83%, 97%, 83% and 94 % for DW-MRI, respectively. Combined PET/Ce-CT/DW-MR scans raise those parameters up to 100%. On a lesion based analysis; the sensitivity, specificity, PPV, NPV and accuracy were 94%, 75%, 94%, 75%, 90% for PET/Ce-CT compared to 94%, 95%, 99%, 97% and 94 % for DW-MRI, respectively. All these parameters were 100 % with PET/Ce-CT/DW-MRI.

CONCLUSIONS

The addition of DW-MRI to PET/Ce-CT is valuable in the characterization of hepatic focal lesions.