Quantitative assessment of hepatic function and its relevance to the liver surgeon

Lobe-Based Hepatic Uptake Index of Gd-EOB-DTPA on Contrast-Enhanced MRI to Quantitatively Discriminate between Compensated and Decompensated Hepatitis B-Related Cirrhosis

Purpose

To use hepatic uptake index (HUI) of liver lobes on gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI) to discriminate between patients with hepatitis B-related cirrhosis in compensated and decompensated statuses.

Methods

Forty-four consecutive patients with hepatitis B-related cirrhosis who underwent Gd-EOB-DTPA-enhanced MRI were divided into compensated and decompensated statuses based on clinical evaluation. Volume and signal intensity of individual lobes were retrospectively measured to calculate HUI of the right liver lobe (RHUI), medial (MHUI) and lateral (LHUI) left liver lobes, and caudate lobe (CHUI). Spearman's rank correlation analyses were performed to evaluate relationships of lobe-based HUI with Child-Pugh and model for end-stage liver disease (MELD) scoring system scores in compensated and decompensated statuses. The Mann-Whitney U-test was used to compare the lobe-based HUI between compensated and decompensated statuses. The performance of lobe-based HUI in distinguishing cirrhosis was evaluated using receiver operating characteristic (ROC) analysis, and the area under the ROC curve (AUC) was calculated as a measure of accuracy. Delong's method was used for statistical analysis to elucidate which HUI is optimal.

Results

Compensated and decompensated liver cirrhosis were confirmed in 25 (56.82%) and 19 (43.18%) patients, respectively. According to Spearman's rank correlation analysis, RHUI, MHUI, LHUI, and CHUI were all significantly associated with Child-Pugh and MELD scores (all P values <0.05). Receiver operating characteristic analysis demonstrated that among all lobe-based HUI parameters, RHUI could best perform the previous discrimination with a cut-off of 485.73 and obtain an AUC of 0.867. The AUC of RHUI improved and was significantly different from that of MHUI, LHUI, and CHUI (P = 0.03, P = 0.007, and P < 0.001, respectively, Delong's test).

Conclusions

The RHUI could help quantitatively discriminate hepatitis B-related cirrhosis between compensated and decompensated statuses.

Radiomics Analysis of Gd-EOB-DTPA Enhanced Hepatic MRI for Assessment of Functional Liver Reserve

Rationale and Objectives To evaluate the effectiveness of radiomics analysis based on Gd-EOB-DTPA enhanced hepatic MRI for functional liver reserve assessment in HCC patients. Materials and Methods Radiomics features were extracted from Gd-EOB-DTPA enhanced MRI images in 60 HCC patients. Boruta algorithm was performed to select features associated with indocyanine green retention rate at 15 min (ICG R15). Prediction and classification model were built by performing Random Forest regression analysis. Pearson correlation analysis and AUC of ROC were used to assess performance of the two models. Results A total of 165 radiomics features were extracted. Six radiomics features were selected to build the prediction model. A Predicted value of ICG R15 for each patient was calculated by the prediction model. Pearson correlation analysis revealed that predicted values were significantly associated with actual values of ICG R15 (R value = 0.90, p < 0.001). Nine radiomics features were selected to build the classification model. AUC of ROC revealed favorable performance of the classification model for identifying patients with ICG R15 <10% (AUC: 0.906, 95%CI: 0.900-0.913), <15% (AUC: 0.954, 95%CI: 0.950-0.958), and <20% (AUC: 0.996, 95%CI: 0.995-0.996). Conclusion Radiomics analysis of Gd-EOB-DTPA enhanced hepatic MRI can be used for assessment of functional liver reserve in HCC patients.

Hepatic function assessment to predict post-hepatectomy liver failure: what can we trust? A systematic review

Post hepatectomy liver failure (PHLF) could occur even though an adequate liver volume is preserved. Liver function is not strictly related to the volume and the necessity to pre-operatively predict the future liver remnant (FLR) function is emerging, together with the wide spreading of techniques, aiming to optimize the FLR. The aim of this study was to systematically review all the available tests, to pre-operatively assess the liver function and to estimate the risk of PHLF. A systematic literature research of Medline, Embase, Scopus was performed in accordance to the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines, to identify all the studies available for pre-operative liver function tests to assess the risk of PHLF and/or complications. From the 1122 references retrieved, 79 were included in the review. Dynamic functional tests, such as indocyanine green test (ICG), could evaluate only global liver function, with no definition of functional capacity of the remnant. Magnetic resonance imaging (MRI) with liver-specific contrast agents enables both liver function and volume evaluation; the absence of ionizing radiation showed a better patient's compliance. Nuclear imaging studies as hepatobiliary scintigraphy (HBS) present the unique ability to allow a precise evaluation of the segmental liver function of the remnant liver. Liver volume could overestimate liver function. Several liver function tests are available to evaluate the risk of PHLF in the pre-operative setting. However, no single test alone could accurately predict PHLF. Pre-operative combination between a dynamic quantitative test, such as ICG, with MRI or HBS, should enable a more complete functional evaluation. Functional tests to predict PHLF should be chosen according to patient's characteristics, disease, and center experience.

Hepatobiliary MRI: Signal intensity based assessment of liver function correlated to 13C-Methacetin breath test

Gadoxetic acid (Gd-EOB-DTPA) is a paramagnetic MRI contrast agent with raising popularity and has been used for evaluation of imaging-based liver function in recent years. In order to verify whether liver function as determined by real-time breath analysis using the intravenous administration of ¹³C-methacetin can be estimated quantitatively from Gd-EOB-DTPA-enhanced MRI using signal intensity (SI) values. 110 patients underwent Gd-EOB-DTPA-enhanced 3-T MRI and, for the evaluation of liver function, a ¹³C-methacetin breath test (¹³C-MBT). SI values from before (SI_pre) and 20 min after (SI_post) contrast media injection were acquired by T1-weighted volume-interpolated breath-hold examination (VIBE) sequences with fat suppression. The relative enhancement (RE) between the plain and contrast-enhanced SI values was calculated and evaluated in a correlation analysis of ¹³C-MBT values to SI_post and RE to obtain a SI-based estimation of ¹³C-MBT values. The simple regression model showed a log-linear correlation of ¹³C-MBT values with SI_post and RE (p < 0.001). Stratified by 3 different categories of ¹³C-MBT readouts, there was a constant significant decrease in both SI_post (p ≤ 0.002) and RE (p ≤ 0.033) with increasing liver disease progression as assessed by the ¹³C-MBT. Liver function as determined using real-time ¹³C-methacetin breath analysis can be estimated quantitatively from Gd-EOB-DTPA-enhanced MRI using SI-based indices.

Gd-EOB-DTPA-enhanced T1 relaxometry for assessment of liver function determined by real-time 13C-methacetin breath test

OBJECTIVES

To determine whether liver function as determined by intravenous administration of ¹³C-methacetin and continuous real-time breath analysis can be estimated quantitatively from gadoxetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance (MR) relaxometry.

METHODS

Sixty-six patients underwent a ¹³C-methacetin breath test (¹³C-MBT) for evaluation of liver function and Gd-EOB-DTPA-enhanced T1-relaxometry at 3 T. A transverse 3D VIBE sequence with an inline T1 calculation based on variable flip angles was acquired prior to (T1 pre) and 20 min post-Gd-EOB-DTPA (T1 post) administration. The reduction rate of T1 relaxation time (rrT1) and T1 relaxation velocity index (∆R1) between pre- and post-contrast images was evaluated. ¹³C-MBT values were correlated with T1_post, ∆R1 and rrT1, providing an MRI-based estimated ¹³C-MBT value. The interobserver reliability was assessed by determining the intraclass correlation coefficient (ICC).

RESULTS

Stratified by three different categories of ¹³C-MBT readouts, there was a constant increase of T1 post with increasing progression of diminished liver function (p ≤ 0.030) and a constant significant decrease of ∆R1 (p ≤ 0.025) and rrT1 (p < 0.018) with progression of liver damage as assessed by ¹³C-methacetin breath analysis. ICC for all T1 relaxation values and indices was excellent (> 0.88). A simple regression model showed a log-linear correlation of ¹³C-MBT values with T1_post (r = 0.57; p < 0.001), ∆R1 (r = 0.59; p < 0.001) and rrT1 (r = 0.70; p < 0.001).

CONCLUSION

Liver function as determined using real-time ¹³C-methacetin breath analysis can be estimated quantitatively from Gd-EOB-DTPA-enhanced MR relaxometry.

KEY POINTS

• Gd-EOB-DTPA-enhanced T1 relaxometry quantifies liver function • Gd-EOB-DTPA-enhanced MR relaxometry may provide parameters for assessing liver function before surgery • Gd-EOB-DTPA-enhanced MR relaxometry may be useful for monitoring liver disease progression • Gd-EOB-DTPA-enhanced MR relaxometry has the potential to become a novel liver function index.

Metabolic liver function in humans measured by 2-18F-fluoro-2-deoxy-D-galactose PET/CT-reproducibility and clinical potential

Background

PET/CT with the radioactively labelled galactose analogue 2-¹⁸F-fluoro-2-deoxy-D-galactose (¹⁸F-FDGal) can be used to quantify the hepatic metabolic function and visualise regional metabolic heterogeneity. We determined the day-to-day variation in humans with and without liver disease. Furthermore, we examined whether the standardised uptake value (SUV) of ¹⁸F-FDGal from static scans can substitute the hepatic systemic clearance of ¹⁸F-FDGal (K_met, mL blood/min/mL liver tissue/) quantified from dynamic scans as measure of metabolic function.

Four patients with cirrhosis and six healthy subjects underwent two ¹⁸F-FDGal PET/CT scans within a median interval of 15 days for determination of day-to-day variation. The correlation between K_met and SUV was examined using scan data and measured arterial blood concentrations of ¹⁸F-FDGal (blood samples) from 14 subjects from previous studies. Regional and whole-liver values of K_met and SUV along with total metabolic liver volume and total metabolic liver function (total SUV, average SUV multiplied by total metabolic liver volume) were calculated.

Results

No significant day-to-day differences were found for K_met or SUV. SUV had higher intraclass correlation coefficients than K_met (0.92–0.97 vs. 0.49–0.78). The relationship between K_met and SUV was linear. Total metabolic liver volume had non-significant day-to-day variation (median difference 50 mL liver tissue; P = 0.6). Mean total SUV in healthy subjects was 23,840 (95% CI, 21,609; 26,070), significantly higher than in the patients (P < 0.001).

Conclusions

The reproducibility of ¹⁸F-FDGal PET/CT was good and SUV can substitute K_met for quantification of hepatic metabolic function. Total SUV of ¹⁸F-FDGal is a promising tool for quantification of metabolic liver function in pre-treatment evaluation of individual patients.

Gd-EOB-DTPA-enhanced MRI for evaluation of liver function: Comparison between signal-intensity-based indices and T1 relaxometry

Gadolinium ethoxybenzyl-diethylenetriaminepentaacetic acid (Gd-EOB-DTPA) is a paramagnetic hepatobiliary magnetic resonance (MR) contrast agent. Due to its OATP1B1/B3-dependent hepatocyte-specific uptake and paramagnetic properties increasing evidence has emerged to suggest that Gd-EOB-DTPA-enhanced MRI can be potentially used for evaluation of liver function. In this paper we compare the diagnostic performance of Gd-EOB-DTPA-enhanced relaxometry-based and commonly used signal-intensity (SI)-based indices, including the hepatocellular uptake index (HUI) and SI-based indices corrected by spleen or muscle, for evaluation of liver function, determined using the Indocyanin green clearance (ICG) test. Simple linear regression model showed a significant correlation of the plasma disappearance rate of ICG (ICG-PDR) with all Gd-EOB-DTPA-enhanced MRI-based liver function indices with a significantly better correlation of relaxometry-based indices on ICG-PDR compared to SI-based indices. Among SI-based indices, HUI achieved best correlation on ICG-PDR and no significant difference of respective correlations on ICG-PDR could be shown. Assessment of liver volume and consecutive evaluation of multiple linear regression model revealed a stronger correlation of ICG-PDR with both (SI)-based and T1 relaxometry-based indices. Thus, liver function can be estimated quantitatively from Gd-EOB-DTPA-enhanced MRI-based indices. Here, indices derived from T1 relaxometry are superior to SI-based indices, and all indices benefit from taking into account respective liver volumes.

Hepatocyte Concentrations of Indocyanine Green Reflect Transfer Rates Across Membrane Transporters

Perioperative imaging with indocyanine green (ICG) is developing to increase safety in dissecting anatomical structures during hepatobiliary surgery. Images obtained with the fluorescence camera rely on concentrations measured in liver regions of interest. However, how ICG sinusoidal uptake and hepatocyte elimination rates generate ICG hepatocyte concentrations is largely unknown. To investigate such issue and better understand the role of membrane transporters in generating ICG hepatocyte concentrations, we perfused ICG in livers isolated from normal livers. Whether the well-known transporter inhibitor rifampicin modifies hepatocyte ICG concentrations was also studied. The dye has a very high and constant extraction ratio (96%) into hepatocytes. This persistent high extraction ratio generates a huge uphill concentration gradient across the sinusoidal membrane: from 5 μM (sinusoids) to 1600 μM (liver). When inside hepatocytes, ICG has low hepatocyte elimination (7 nmol/min.) and liver concentrations do not decrease much over time. Moreover, the tiny hepatocyte ICG efflux is mainly due to ICG return back to sinusoids (90%). Rifampicin slightly inhibits ICG uptake into hepatocytes and when inside hepatocytes blocks ICG efflux into bile canaliculi. In contrast, it increases ICG efflux back to sinusoids with significant decrease in ICG liver concentrations. Imaging with ICG in the perioperative period reflects the high hepatocyte concentrations and relies on the high extraction ratio across hepatocyte sinusoidal membrane. Although ICG concentrations are low in bile ducts, they are adequate for a good visualization and avoid bile duct injury.

Noninvasive mapping of the redox status of dimethylnitrosamine-induced hepatic fibrosis using in vivo dynamic nuclear polarization-magnetic resonance imaging

Hepatic fibrosis is a chronic disorder caused by viral infection and/or metabolic, genetic and cholestatic disorders. A noninvasive procedure that enables the detection of liver fibrosis based on redox status would be useful for disease identification and monitoring, and the development of treatments. However, an appropriate technique has not been reported. This study describes a novel method for assessing the redox status of the liver using in vivo dynamic nuclear polarization-magnetic resonance imaging (DNP-MRI) with the nitroxyl radical carbamoyl-PROXYL as a molecular imaging probe, which was tested in dimethylnitrosamine-treated mice as a model of liver fibrosis. Based on the pharmacokinetics of carbamoyl-PROXYL in control livers, reduction rate mapping was performed in fibrotic livers. Reduction rate maps demonstrated a clear difference between the redox status of control and fibrotic livers according to the expression of antioxidants. These findings indicate that in vivo DNP-MRI with a nitroxyl radical probe enables noninvasive detection of changes in liver redox status.

Gadoxetic acid: pearls and pitfalls

Gadoxetic acid is a hepatocyte-specific magnetic resonance imaging contrast agent with the ability to detect and characterize focal liver lesions and provide structural and functional information about the hepatobiliary system. Knowledge of the pharmacokinetics of gadoxetic acid is paramount to understanding imaging protocol and lesion appearance and facilitates identification and avoidance of undesired effects with use of this intravenous contrast agent. This article reviews the utility of gadoxetic acid in liver and biliary imaging, with emphasis on the hepatobiliary phase.

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.

The inhomogeneous distribution of liver function: possible impact on the prediction of post-operative remnant liver function

BACKGROUND

Previous studies have shown that liver function is inhomogeneously distributed in diseased livers, and this uneven distribution cannot be compensated for if a global liver function test is used for the prediction of post-operative remnant liver function. Dynamic Gd-EOB-DTPA-enhanced magnetic resonance imaging (MRI) can assess segmental liver function, thus offering the possibility to overcome this problem.

METHODS

In 10 patients with liver cirrhosis and 10 normal volunteers, the contribution of individual liver segments to total liver function and volume was calculated using dynamic Gd-EOB-DTPA-enhanced MRI. Remnant liver function predictions using a segmental method and global assessment were compared for a simulated left hemihepatectomy. For the prediction based on segmental functional MRI assessment, the estimated function of the remnant liver segments was added.

RESULTS

Global liver function assessment overestimated the remnant liver function in 9 out of 10 patients by as much as 9.3% [median -3.5% (-9.3-3.5%)]. In the normal volunteers there was a slight underestimation of remnant function in 9 out of 10 cases [median 1.07% (-0.7-2.5%)].

DISCUSSION

The present study underlines the necessity of a segmental liver function test able to compensate for the non-homogeneous nature of liver function, if the prediction of post-operative remnant liver function is to be improved.

Imaging-based evaluation of liver function: comparison of ⁹⁹mTc-mebrofenin hepatobiliary scintigraphy and Gd-EOB-DTPA-enhanced MRI

OBJECTIVES

To compare Gd-EOB-enhanced MRI and (99m)Tc-mebrofenin hepatobiliary scintigraphy (HBS) as imaging-based liver function tests for separate evaluation of right (RLL) and left liver lobe (LLL) function.

METHODS

Fourteen patients underwent Gd-EOB-enhanced MRI and (99m)Tc-mebrofenin HBS after portal vein embolization within 24 h. Relative enhancement (RE) and hepatic uptake index (HUI) were determined from MRI; and T max, T 1/2 and mebrofenin uptake were determined from HBS, all values separately for RLL and LLL.

RESULTS

Mebrofenin uptake correlated significantly with HUI and RE for both liver lobes. There was strong correlation of mebrofenin uptake with HUI for RLL (r (2) = 0.802, p = 0.001) and RE for LLL (r (2) = 0.704, p = 0.005) and moderate correlation with HUI for LLL (r (2) = 0.560, p = 0.037) and RE for RLL (r (2) = 0.620, p = 0.018). Correlating the percentage share of RLL function derived from MRI (with HUI) with the percentage of RLL function derived from mebrofenin uptake revealed a strong correlation (r (2) = 0.775, p = 0.002).

CONCLUSIONS

Both RE and HUI correlate with mebrofenin uptake in HBS. The results suggest that Gd-EOB-enhanced MRI and (99m)Tc-mebrofenin HBS may equally be used to separately determine right and left liver lobe function.

KEY POINTS

• Information about liver function can be acquired with routine Gd-EOB-MRI. • Gd-EOB-MRI and (99m) Tc-mebrofenin HBS show elevated function of non-embolized lobe. • Gd-EOB-MRI and (99m) Tc-mebrofenin HBS can determine lobar liver function.

Evaluation of gadolinium-EOB-DTPA uptake after portal vein embolization: value of an increased flip angle

BACKGROUND

The optimal sequence for Gd-EOB-DTPA uptake measurement in the liver with the purpose of liver function measurement is still not defined.

PURPOSE

To prospectively evaluate the effect of an increased flip angle (FA) of a T1-weighted fat-saturated 3D sequence for the measurement of hepatocyte uptake of Gd-EOB-DTPA magnetic resonance imaging (MRI) after right portal vein embolization (PVE).

MATERIAL AND METHODS

Ten patients who received a PVE prior to an extended hemihepatectomy were examined 14 days after PVE using Gd-EOB-DTPA enhanced MRI of the liver using the standard FA of 10° and the increased FA of 30°.

RESULTS

Relative enhancement of the right liver lobe (RLL) was 0.52 ± 0.12 for 10° and 1.41 ± 0.39 for 30°. Relative enhancement of the left liver lobe (LLL) was 0.58 ± 0.11 for 10° and 2.05 ± 0.61 for 30°. Relative enhancement of the RLL was significantly higher for 30° than for 10° (P = 0.009) and significantly higher in the 30° than in the 10° sequences (P = 0.005) for the LLL.

CONCLUSION

A flip angle of 30° increases the contrast between liver partitions with and without portal venous embolization. Thereby, the sensitivity for differences in uptake intensity is increased. This could be of value for a more exact determination of differences in regional liver function and, consequently, the estimation of the future remnant liver function.

Preoperative liver function assessments to estimate the prognosis and safety of liver resections

Liver function assessment is important to ensure safe surgical procedures in patients with hepatocellular disease. Because the liver influences a wide variety of functions, including protein synthesis and metabolic, immune and storage functions, no single parameter is sufficient to adequately address all of these functions. We reviewed the relevant literature concerning the scoring systems, functional tests, plasma parameters and imaging modalities currently used to evaluate the liver function in an attempt to determine which parameters provide the most comprehensive and useful results. While the Child-Pugh scoring system is the gold standard for liver disease assessment, the liver damage grading system recommended by the Liver Cancer Study Group of Japan is also useful. Various models for end-stage liver disease scoring are used for organ allocation. While the indocyanine green clearance test is widely accepted throughout the world, other assessments have not been used routinely for clinical evaluations. The levels of plasma proteins, including albumin, prealbumin, retinol binding protein, apolipoprotein, coagulation factors and antithrombin III, represent the liver productivity. Liver fibrotic markers also correlate with liver function. Imaging modalities such as (99m)Tc-galactosyl serum albumin scintigraphy, (99m)Tc-mebrofenin hepatobiliary scintigraphy and transient elastography are also available, but future studies are needed to validate their clinical efficacy.

Consensus report from the 6th International forum for liver MRI using gadoxetic acid

As the utility of liver-specific magnetic resonance imaging (MRI) increases, it is pertinent to optimize and expand protocols to improve accuracy and foster evolution of techniques; in turn, positive impacts should be seen in patient management. This article reports on the latest expert thinking and current evidence in the field of liver-specific MRI, as discussed at the 6(th) International Forum for Liver MRI, which was held in Vancouver, Canada in September 2012. Topics discussed at this forum described the use of gadoxetic acid-enhanced MRI for the assessment of liver function at the segmental level; to increase accuracy in the diagnosis of liver metastases; to overcome current challenges in patients with cirrhosis, including management of arterial hypo-/isovascular, hepatobiliary phase hypointense nodules; and the data which would be required in order to recommend the use of this modality in hepatocellular carcinoma management guidelines. Growing evidence suggests that gadoxetic acid-enhanced MRI can help to improve the management of patients with a number of different liver disorders; however, more data are needed in some areas, and there may be a case for developing an interpretation guideline for gadoxetic acid-enhanced MRI findings to aid standardization.

Feasibility of semiautomated MR volumetry using gadoxetic acid-enhanced MRI at hepatobiliary phase for living liver donors

PURPOSE

To assess the feasibility of semiautomated MR volumetry using gadoxetic acid-enhanced MRI at the hepatobiliary phase compared with manual CT volumetry.

METHODS

Forty potential live liver donor candidates who underwent MR and CT on the same day, were included in our study. Semiautomated MR volumetry was performed using gadoxetic acid-enhanced MRI at the hepatobiliary phase. We performed the quadratic MR image division for correction of the bias field inhomogeneity. With manual CT volumetry as the reference standard, we calculated the average volume measurement error of the semiautomated MR volumetry. We also calculated the mean of the number and time of the manual editing, edited volume, and total processing time.

RESULTS

The average volume measurement errors of the semiautomated MR volumetry were 2.35% ± 1.22%. The average values of the numbers of editing, operation times of manual editing, edited volumes, and total processing time for the semiautomated MR volumetry were 1.9 ± 0.6, 8.1 ± 2.7 s, 12.4 ± 8.8 mL, and 11.7 ± 2.9 s, respectively.

CONCLUSION

Semiautomated liver MR volumetry using hepatobiliary phase gadoxetic acid-enhanced MRI with the quadratic MR image division is a reliable, easy, and fast tool to measure liver volume in potential living liver donors.

N-acetylcysteine administration does not improve patient outcome after liver resection

BACKGROUND

Post-operative hepatic dysfunction is a major cause of concern when undertaking a liver resection. The generation of reactive oxygen species (ROS) as a result of hepatic ischaemia/reperfusion (I/R) injury can result in hepatocellular injury. Experimental evidence suggests that N-acetylcysteine may ameliorate ROS-mediated liver injury.

METHODS

A cohort of 44 patients who had undergone a liver resection and receiving peri-operative N-acetylcysteine (NAC) were compared with a further cohort of 44 patients who did not. Liver function tests were compared on post-operative days 1, 3 and 5. Peri-operative outcome data were retrieved from a prospectively maintained database within our unit.

RESULTS

Administration of NAC was associated with a prolonged prothrombin time on the third post-operative day (18.4 versus 16.4 s; P = 0.002). The incidence of grades B and C liver failure was lower in the NAC group although this difference did not reach statistical significance (6.9% versus 14%; P = 0.287). The overall complication rate was similar between groups (32% versus 25%; P = ns). There were two peri-operative deaths in the NAC group and one in the control group (P = NS).

CONCLUSION

In spite of promising experimental evidence, this study was not able to demonstrate any advantage in the routine administration of peri-operative NAC in patients undergoing a liver resection.

Increase in left liver lobe function after preoperative right portal vein embolisation assessed with gadolinium-EOB-DTPA MRI

OBJECTIVES

To prospectively evaluate the early development of regional liver function after right portal vein embolisation (PVE) with Gd-EOB-DTPA-enhanced MRI in patients scheduled for extended right hemihepatectomy.

METHODS

Ten patients who received a PVE before an extended hemihepatectomy were examined before and 14 days after PVE using Gd-EOB-DTPA-enhanced MRI of the liver. In these sequences representative region of interest measurements were performed in the embolised right (RLL) and the non-embolised left liver lobe (LLL). The volume as well as hepatic uptake index (HUI) was calculated independently for each lobe.

RESULTS

Relative enhancement 14 days after PVE decreased in the RLL and increased significantly in the LLL (P < 0.05). Average hepatic uptake index (HUI) for RLL was significantly lower 14 days after PVE than before PVE (P < 0.05) and significantly higher for LLL (P < 0.05).

CONCLUSIONS

A significant shift of contrast uptake from the right to the left liver lobe can be depicted as early as 14 days after right PVE by using Gd-EOB-DTPA-enhanced MRI, which could reflect the redirected portal venous blood flow and the rapid utilisation of a hepatic functional reserve.

KEY POINTS

• Preoperative portal vein embolisation (PVE) is widely performed before right-sided hepatic resection. • PVE increases intravenous contrast medium uptake in the left lobe of liver. • The hepatic uptake index for the left liver lobe increases rapidly after PVE. • Left liver lobe function increase may be visualised by Gd-EOB-DTPA-enhanced MRI.

Gd-EOB-DTPA-enhanced MRI for the assessment of liver function and volume in liver cirrhosis

OBJECTIVE

The aims of this study were to use dynamic hepatocyte-specific contrast-enhanced MRI to evaluate liver volume and function in liver cirrhosis, correlate the results with standard scoring models and explore the inhomogeneous distribution of liver function in cirrhotic livers.

METHODS

10 patients with liver cirrhosis and 20 healthy volunteers, serving as controls, were included. Hepatic extraction fraction (HEF), input relative blood flow and mean transit time were calculated on a voxel-by-voxel basis using deconvolutional analysis. Segmental and total liver volumes as well as segmental and total hepatic extraction capacity, expressed in HEFml, were calculated. An incongruence score (IS) was constructed to reflect the uneven distribution of liver function. The Mann-Whitney U-test was used for group comparison of the quantitative liver function parameters, liver volumes and ISs. Correlations between liver function parameters and clinical scores were assessed using Spearman rank correlation.

RESULTS

Patients had larger parenchymal liver volume, lower hepatocyte function and more inhomogeneous distribution of function compared with healthy controls.

CONCLUSION

The study demonstrates the non-homogeneous nature of liver cirrhosis and underlines the necessity of a liver function test able to compensate for the heterogeneous distribution of liver function in patients with diseased liver parenchyma.

ADVANCES IN KNOWLEDGE

The study describes a new way to quantitatively assess the hepatic uptake of gadoxetate or gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid in the liver as a whole as well as on a segmental level.

Assessment of hepatic function with Gd-EOB-DTPA-enhanced hepatic MRI

Assessment of hepatic function is essential in determining the prognosis and clinical management of a patient who has chronic liver disease or undergoes liver surgery. For a patient with locally varying hepatic parenchymal abnormalities, a regional assessment of hepatic function mapped onto hepatic anatomy is clinically more meaningful than conventional global metrics of hepatic function. Of late, hepatic magnetic resonance imaging has been increasingly used because of its superb tissue contrast and delineation of hepatic morphology and underlying abnormalities. The introduction of hepatocyte-specific contrast agents such as Gd-EOB-DTPA allows us to view not only the hepatic anatomy but also assess regional hepatic function. In this article, we review and discuss recently published studies that used Gd-EOB-DTPA-enhanced magnetic resonance imaging to evaluate hepatic function.

Chemotherapy-associated liver injury in patients with colorectal liver metastases: a systematic review and meta-analysis

BACKGROUND

Chemotherapy-associated liver injury is a major cause for concern when treating patients with colorectal liver metastases. The aim of this review was to determine the pathological effect of specific chemotherapy regimens on the hepatic parenchyma as well as on surgical morbidity, mortality and overall survival.

METHODS

A systematic review of the published literature and a meta-analysis were performed. For each of the variables under consideration, the effects of different chemotherapy regimens were determined by calculation of relative risks by a random-effects model.

RESULTS

Hepatic parenchymal injury is regimen specific, with oxaliplatin-based regimens being associated with grade 2 or greater sinusoidal injury (number needed to harm 8; 95 % confidence interval [CI] 6.4-13.6), whereas irinotecan-based regimens associated with steatohepatitis (number needed to harm 12; 95 % CI 7.8-26). The use of bevacizumab alongside FOLFOX reduces the risk of grade 2 or greater sinusoidal injury (relative risk 0.34; 95 % CI 0.15-0.75).

CONCLUSIONS

Chemotherapy before resection of colorectal liver metastases is associated with an increased risk of regimen-specific liver injury. This liver injury may have implications for the functional reserve of the liver for patients undergoing major hepatectomy for colorectal liver metastases.

Liver function testing with nuclear medicine techniques is coming of age

Liver function is a broad term, as the organ participates in a multitude of different physiological and biochemical processes, including metabolic, synthetic, and detoxifying functions. However, it is the function of the hepatocyte that is central to sustaining normal life and dealing with disease states. When the liver begins to fail in severely ill patients, it forecasts a terminal outcome. However, unlike the glomerular filtration rate which clearly quantifies the key renal function, at most practice sites, there is no clinically available quantitative test for liver function. Although it is commonplace to assess indirect evidence of that function (by measuring blood levels of its end products and by-products) and to detect an acute injury (by following rising transaminases), a widely available test that would directly measure hepatocellular function is lacking. This article reviews current knowledge on liver function studies and focuses on those nuclear medicine tests available to study the whole liver and regional liver function. The clinical application driving these tests, prediction of remnant liver function after partial hepatectomy for primary liver malignancy or metastatic disease, is addressed here in detail. The test was recently validated for this specific application and was shown to be better than the current standard of practice (computed tomography volumetry), particularly in patients with hepatic comorbidities like cirrhosis, steatosis, or cholestasis. Furthermore, early assessment of regional liver function increase after preoperative portal vein embolization becomes possible with this technology. The limiting factor to a wider acceptance of this test is based on the lack of clinical software that would allow calculation of liver function parameters. This article provides information that enables a clinical nuclear medicine facility to provide this test using readily available equipment. Furthermore, it addresses emerging clinical applications that are under investigation.

Consensus report of the 4th International Forum for Gadolinium-Ethoxybenzyl-Diethylenetriamine Pentaacetic Acid Magnetic Resonance Imaging

This paper reports on issues relating to the optimal use of gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid magnetic resonance imaging (Gd-EOB-DTPA MR imaging) together with the generation of consensus statements from a working group meeting, which was held in Seoul, Korea (2010). Gd-EOB-DTPA has been shown to improve the detection and characterization of liver lesions, and the information provided by the hepatobiliary phase is proving particularly useful in differential diagnoses and in the characterization of small lesions (around 1-1.5 cm). Discussion also focused on advances in the role of organic anion-transporting polypeptide 8 (OATP8) transporters. Gd-EOB-DTPA is also emerging as a promising tool for functional analysis, enabling the calculation of post-surgical liver function in the remaining segments. Updates to current algorithms were also discussed.

Use of hepatocyte and stem cells for treatment of post-resectional liver failure: are we there yet?

Post-operative liver failure following extensive resections for liver tumours is a rare but significant complication. The only effective treatment is liver transplantation (LT); however, there is a debate about its use given the high mortality compared with the outcomes of LT for chronic liver diseases. Cell therapy has emerged as a possible alternative to LT especially as endogenous hepatocyte proliferation is likely inhibited in the setting of prior chemo/radiotherapy. Both hepatocyte and stem cell transplantations have shown promising results in the experimental setting; however, there are few reports on their clinical application. This review identifies the potential stem cell sources in the body, and highlights the triggering factors that lead to their mobilization and integration in liver regeneration following major liver resections.

Biliary physiology and disease: reflections of a physician-scientist

A review is presented of Gustav Paumgartner's five decades of research and practice in hepatology focusing on biliary physiology and disease. It begins with studies of the excretory function of the liver including hepatic uptake of indocyanine green, bilirubin, and bile acids. The implications of these studies for diagnosis and understanding of liver diseases are pointed out. From there, the path of scientific research leads to investigations of hepatobiliary bile acid transport and the major mechanisms of bile formation. The therapeutic effects of the hydrophilic bile acid, ursodeoxycholic acid, have greatly stimulated these studies. Although ursodeoxycholic acid therapy for dissolution of cholesterol gallstones and some other nonsurgical treatments of gallstones were largely superseded by surgical techniques, ursodeoxycholic acid is currently considered the mainstay of therapy of some chronic cholestatic liver diseases, such as primary biliary cirrhosis. The major mechanisms of action of ursodeoxycholic acid therapy in cholestatic liver diseases are discussed. An attempt is made to illustrate how scientific research can lead to advances in medical practice that help patients.

Liver functional reserve estimation: state of the art and relevance for local treatments: the Eastern perspective

Liver function reserve estimation is important for selecting the appropriate patients for hepatectomy or ablation of tumors. Many liver function tests have been devised, but the indocyanine green (ICG) clearance test remains the most popular for its simplicity and perhaps accuracy. Compared with the Child-Pugh classification, the ICG retention value at 15 min (ICGR-15) after intravenous injection provides more information. Though a significant difference in ICGR-15 has been observed between patients with Child-Pugh A and B liver function, the hospital mortality rates following partial hepatectomy are not significantly different between the two groups. Yet, ICGR-15 values can differentiate patients with or without hospital mortality. The cutoff values of ICGR-15 for a safe major and minor hepatectomy are 14 and 22%, respectively.