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.

Arterial versus portal venous embolization for induction of hepatic hypertrophy before extended right hemihepatectomy in hilar cholangiocarcinomas: a prospective randomized study.

PURPOSE: To assess the efficacy and safety of portal vein (PV) embolization versus hepatic artery embolization (HAE) for induction of hepatic hypertrophy before extended right hemihepatectomy in patients with hilar cholangiocarcinoma. MATERIALS AND METHODS: Fifty patients (female, n = 15; male, n = 35; age range, 37-80 y) with hilar cholangiocarcinomas who were planned to undergo extended right hemihepatectomy were prospectively included in 2003-2006. In addition to biliary decompression of the left liver, patients were randomized to undergo embolization of the right hepatic artery (with transfemoral access and polyvinyl alcohol [PVA] particles plus coils) or right PV branches (with computed tomography [CT]-guided transhepatic access and PVA particles). CT was performed before and approximately 3 weeks after embolization for volumetric assessment of the liver. RESULTS: In the HAE group, median growth of the left lateral segments was 40 mL (P < .01), with a median reduction of the whole liver of 10 mL (P = .41); adverse events were observed in two of 25 patients (8%), who each developed an abscess in the right liver lobe. In the PV embolization group, median growth of the left lateral segments was 110 mL (P < .01), with a median growth of the whole liver of 10 mL (P = .92); a subcapsular seroma occurred in one of 25 patients (4%). The median growth of the left lateral segments after PV embolization was significantly greater than after HAE (P = .004). CONCLUSIONS: Compared with HAE, PV embolization was significantly superior regarding induction of hepatic hypertrophy of the left lateral segments.

Multidetector computed tomography for preoperative assessment of hepatic vasculature and prediction of splenic artery steal syndrome in patients with liver cirrhosis before transplantation.

The purpose of this study was to evaluate the accuracy of MDCT for preoperative assessment of hepatic vascular anatomy and the identification of liver-transplantation (OLT) patients at risk of developing subsequent splenic artery steal syndrome (SASS). A total of 145 patients with liver cirrhosis who had undergone OLT and had pre-operative three-phase MDCT (4- to 64-rows) within 100 days before OLT were enrolled retrospectively. MDCT and 3Ds were reviewed by two independent blinded observers (O1/O2). Pre-operative imaging findings were correlated with intra-operative results; findings indicative for SASS were correlated with clinical data and DSA. Among all 145 patients, 16 patients (11%) showed accessory hepatic arteries (accuracy O1/O2, 97%; with 3Ds, 100%); 32 (22%) patients had replaced hepatic arteries (accuracy O1, 97%; O2, 95%; with 3Ds, 100%; kappa = 0.87 and 0.89, P < 0.001). Among 119 patients, 12 patients developed SASS after OLT. The logistic regression model revealed the spleen volume (P = 0.0105) as a predictive factor of SASS. With spleen volumes >or=829 ml, an accuracy of 75% for prediction of SASS was obtained. MDCT with three-dimensional post-processing (3Ds) was highly accurate for pre-operative hepatic vessel evaluation in patients before OLT. In addition, spleen volume was a predictive factor for developing SASS after OLT.

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.

Size determination and response assessment of liver metastases with computed tomography--comparison of RECIST and volumetric algorithms.

OBJECTIVE: To compare different three-dimensional volumetric algorithms (3D-algorithms) and RECIST for size measurement and response assessment in liver metastases from colorectal and pancreatic cancer. METHODS: The volumes of a total of 102 liver metastases in 45 patients (pancreatic cancer, n=22; colon cancer, n=23) were estimated using three volumetric methods (seeded region growing method, slice-based segmentation, threshold-based segmentation) and the RECIST 1.1 method with volume calculation based on the largest axial diameter. Each measurement was performed three times by one observer. All four methods were applied to follow-up on 55 liver metastases in 29 patients undergoing systemic treatment (median follow-up, 3.5 months; range, 1-10 months). Analysis of variance (ANOVA) with post hoc tests was performed to analyze intraobserver variability and intermethod differences. RESULTS: ANOVA showed significant higher volumes calculated according to the RECIST guideline compared to the other measurement methods (p<0.001) with relative differences ranging from 0.4% to 41.1%. Intraobserver variability was significantly higher (p<0.001) for RECIST and threshold based segmentation (3.6-32.8%) compared with slice segmentation (0.4-13.7%) and seeded region growing method (0.6-10.8%). In the follow-up study, the 3D-algorithms and the assessment following RECIST 1.1 showed a discordant classification of treatment response in 10-21% of the patients. CONCLUSIONS: This study supports the use of volumetric measurement methods due to significant higher intraobserver reproducibility compared to RECIST. Substantial discrepancies in tumor response classification between RECIST and volumetric methods depending on applied thresholds confirm the requirement of a consensus concerning volumetric criteria for response assessment.

Flip angle modulations in late phase Gd-EOB-DTPA MRI improve the identification of the biliary system.

OBJECTIVES: To assess the improvement of bile duct visualization in Gd-EOB-DTPA enhanced MR-cholangiography (EOB-MRC) by using an increased flip angle. METHODS: 35 patients underwent Gd-EOB-DTPA enhanced MRI of the liver including T2-weighted MRCP and hepatobiliary phase EOB-MRC using a flip angle of 10° (FA10) and of 35° (FA35), respectively. Images were evaluated regarding the delineation of biliary ducts, the order of branching and anatomic visualization of the biliary tree. ROI analysis was performed to estimate the signal-to-noise (SNR) and contrast-to-noise (CNR) ratios. RESULTS: Applying the FA35 resulted in a significantly better SNR and CNR as compared to FA10. The overall image quality was rated as good for both, FA10 and FA35. The overall rating for regional delineation of the biliary system was rated significantly better for FA35 than for FA10 (p=0.02). Classification of bile duct anatomy variations, however, was equivalent in both techniques. CONCLUSIONS: Increasing the flip angle of a T1-weighted 3D-sequence from 10° to 35° during the hepatobiliary phase of Gd-EOB enhanced MRI visually and quantitatively improved the visualization of the biliary ducts.