Evaluation of hepatic fibrosis using intravoxel incoherent motion in diffusion-weighted liver MRI. J Comput Assist Tomogr. 2014;38:110-116. [PMID: 24378888 DOI: 10.1097/rct.0b013e3182a589be]

Staging liver fibrosis with various diffusion-weighted magnetic resonance imaging models

BACKGROUND

Diffusion-weighted imaging (DWI) has been developed to stage liver fibrosis. However, its diagnostic performance is inconsistent among studies. Therefore, it is worth studying the diagnostic value of various diffusion models for liver fibrosis in one cohort.

AIM

To evaluate the clinical potential of six diffusion-weighted models in liver fibrosis staging and compare their diagnostic performances.

METHODS

This prospective study enrolled 59 patients suspected of liver disease and scheduled for liver biopsy and 17 healthy participants. All participants underwent multi-b value DWI. The main DWI-derived parameters included Mono-apparent diffusion coefficient (ADC) from mono-exponential DWI, intravoxel incoherent motion model-derived true diffusion coefficient (IVIM-D), diffusion kurtosis imaging-derived apparent diffusivity (DKI-MD), stretched exponential model-derived distributed diffusion coefficient (SEM-DDC), fractional order calculus (FROC) model-derived diffusion coefficient (FROC-D) and FROC model-derived microstructural quantity (FROC-μ), and continuous-time random-walk (CTRW) model-derived anomalous diffusion coefficient (CTRW-D) and CTRW model-derived temporal diffusion heterogeneity index (CTRW-α). The correlations between DWI-derived parameters and fibrosis stages and the parameters' diagnostic efficacy in detecting significant fibrosis (SF) were assessed and compared.

RESULTS

CTRW-D (r = -0.356), CTRW-α (r = -0.297), DKI-MD (r = -0.297), FROC-D (r = -0.350), FROC-μ (r = -0.321), IVIM-D (r = -0.251), Mono-ADC (r = -0.362), and SEM-DDC (r = -0.263) were significantly correlated with fibrosis stages. The areas under the ROC curves (AUCs) of the combined index of the six models for distinguishing SF (0.697-0.747) were higher than each of the parameters alone (0.524-0.719). The DWI models' ability to detect SF was similar. The combined index of CTRW model parameters had the highest AUC (0.747).

CONCLUSION

The DWI models were similarly valuable in distinguishing SF in patients with liver disease. The combined index of CTRW parameters had the highest AUC.

Intravoxel incoherent motion for differentiating residual/recurrent tumor from post-treatment change in patients with high-grade glioma

PURPOSE

To investigate the diagnostic value of f derived from IVIM technique and to correlate it with rCBV derived from DSC for the differentiation of residual/recurrent tumor from post-treatment change in patients with high-grade glioma.

MATERIALS AND METHODS

Patients who underwent MR imaging with IVIM and DSC studies for evaluation of high-grade glioma after standard treatment were enrolled in this retrospective study. For qualitative analysis, the f and rCBV maps were interpreted as hypoperfused or hyperperfused in each parameter. Quantitative analysis was performed using ROI analysis in f and rCBV parameters. The lesions were divided into residual/recurrent tumor and post-treatment change groups.

RESULTS

Nineteen patients with high-grade glioma were included. In qualitative analysis, the f-map shows higher sensitivity (100.0%) than rCBV map (92.3%), while the rCBV map shows higher specificity (100.0%) than the f-map (83.3%). In quantitative analysis, the optimal cutoff values of 1.19 for f and 1.06 for rCBV are shown to provide high diagnostic value with high sensitivity (91.7%) for both parameters but slightly higher specificity of rCBV (85.7%) than f (71.4%). The correlation between f and rCBV was good with ICC of 0.810.

CONCLUSION

The f value measured by IVIM technique, non-contrast perfusion technique, has high diagnostic performance and potential to be an alternative method to CBV measured by DSC for differentiation between residual/recurrent tumor and post-treatment change in patients with high-grade glioma.

Comparison between Intravoxel Incoherent Motion and Splenic Volumetry to Predict Hepatic Fibrosis Staging in Preoperative Patients

Intravoxel incoherent motion (IVIM) and splenic volumetry (SV) for hepatic fibrosis (HF) prediction have been reported to be effective. Our purpose is to compare the HF prediction of IVIM and SV in 67 patients with pathologically staged HF. SV was divided by body surface area (BSA). IVIM indices, such as slow diffusion-coefficient related to molecular diffusion (D), fast diffusion-coefficient related to perfusion in microvessels (D*), apparent diffusion-coefficient (ADC), and perfusion related diffusion-fraction (f), were calculated by two observers (R1/R2). D (p = 0.718 for R1, p = 0.087 for R2) and D* (p = 0.513, p = 0.708, respectively) showed a poor correlation with HF. ADC (p = 0.034, p = 0.528, respectively) and f (p < 0.001, p = 0.007, respectively) decreased as HF progressed, whereas SV/BSA increased (p = 0.015 for R1). The AUCs of SV/BSA (0.649-0.698 for R1) were higher than those of f (0.575-0.683 for R1 + R2) for severe HF (≥F3-4 and ≥F4), although AUCs of f (0.705-0.790 for R1 + R2) were higher than those of SV/BSA (0.628 for R1) for mild or no HF (≤F0-1). No significant differences to identify HF were observed between IVIM and SV/BSA. SV/BSA allows a higher estimation for evaluating severe HF than IVIM. IVIM is more suitable than SV/BSA for the assessment of mild or no HF.

Impact of velocity- and acceleration-compensated encodings on signal dropout and black-blood state in diffusion-weighted magnetic resonance liver imaging at clinical TEs

PURPOSE

The study aims to develop easy-to-implement concomitant field-compensated gradient waveforms with varying velocity-weighting (M1) and acceleration-weighting (M2) levels and to evaluate their efficacy in correcting signal dropouts and preserving the black-blood state in liver diffusion-weighted imaging. Additionally, we seek to determine an optimal degree of compensation that minimizes signal dropouts while maintaining blood signal suppression.

METHODS

Numerically optimized gradient waveforms were adapted using a novel method that allows for the simultaneous tuning of M1- and M2-weighting by changing only one timing variable. Seven healthy volunteers underwent diffusion-weighted magnetic resonance imaging (DWI) with five diffusion encoding schemes (monopolar, velocity-compensated (M1 = 0), acceleration-compensated (M1 = M2 = 0), 84%-M1-M2-compensated, 67%-M1-M2-compensated) at b-values of 50 and 800 s/mm2 at a constant echo time of 70 ms. Signal dropout correction and apparent diffusion coefficients (ADCs) were quantified using regions of interest in the left and right liver lobe. The blood appearance was evaluated using two five-point Likert scales.

RESULTS

Signal dropout was more pronounced in the left lobe (19%-42% less signal than in the right lobe with monopolar scheme) and best corrected by acceleration-compensation (8%-10% less signal than in the right lobe). The black-blood state was best with monopolar encodings and decreased significantly (p < 0.001) with velocity- and/or acceleration-compensation. The partially M1-M2-compensated encoding schemes could restore the black-blood state again. Strongest ADC bias occurred for monopolar encodings (difference between left/right lobe of 0.41 μm2/ms for monopolar vs. < 0.12 μm2/ms for the other encodings).

CONCLUSION

All of the diffusion encodings used in this study demonstrated suitability for routine DWI application. The results indicate that a perfect value for the level of M1-M2-compensation does not exist. However, among the examined encodings, the 84%-M1-M2-compensated encodings provided a suitable tradeoff.

Imaging Phenotypes and Evolution of Hepatic Langerhans Cell Histiocytosis on CT/MRI: A Retrospective Study of Clinical Cases and Literature Review

(1) Background: pathological changes in hepatic Langerhans cell histiocytosis (LCH) have been observed; however, corresponding imaging findings can appear vague to physicians and radiologists. The present study aimed to comprehensively illustrate the imaging findings of hepatic LCH and to investigate the evolution of LCH-associated lesions. (2) Methods: LCH patients with liver involvement treated at our institution were retrospectively reviewed along with prior studies in PubMed. Initial and follow-up computed tomography (CT) and magnetic resonance imaging (MRI) were systematically reviewed, and three imaging phenotypes were created based on the lesion distribution pattern. Clinical features and prognoses were compared among the three phenotypes. Liver fibrosis was evaluated visually on T2-weighted imaging (T2WI) and diffusion-weighted imaging (DWI), and apparent diffusion coefficient (ADC) values of the fibrotic areas were measured. Descriptive statistics and a comparative analysis were used to analyze the data. (3) Results: based on the lesion distribution pattern on CT/MRI scans, patients with liver involvement were categorized as the disseminated lesion phenotype, scattered lesion phenotype, and central periportal lesion phenotype. Patients with scattered lesion phenotype were typically adults, and only a few of them had hepatomegaly (n_present = 1, 1/6, 16.7%) and liver biochemical abnormalities (n_present = 2, 2/6, 33.3%); patients with central periportal lesion phenotype were typically young children, and hepatomegaly and biochemical abnormalities were more apparent in these patients than those with another phenotype; and those with the disseminated lesion phenotype were found in all age groups, and the lesions evolved rapidly on medical imaging. Follow-up MRI scans show more details and can better document the evolution of lesions than CT. T2-hypointense fibrotic changes, including the periportal halo sign (n_present = 2, 2/9, 22.2%), patchy liver parenchyma changes (n_present = 6, 6/9, 66.7%), and giant hepatic nodules close to the central portal vein (n_present = 1, 1/9, 11.1%), were found, while fibrotic changes were not observed in patients with the scattered lesion phenotype. The mean ADC value for the area of liver fibrosis in each patient was lower than the optimal cutoff for significant fibrosis (METAVIR Fibrosis Stage ≥ 2) in a previous study that assessed liver fibrosis in chronic viral hepatitis. (4) Conclusions: The infiltrative lesions and liver fibrosis of hepatic LCH can be well characterized on MRI scans with DWI. The evolution of these lesions was well demonstrated on follow-up MRI scans.

Updates on Quantitative MRI of Diffuse Liver Disease: A Narrative Review

Diffuse liver diseases are highly prevalent conditions around the world, including pathological liver changes that occur when hepatocytes are damaged and liver function declines, often leading to a chronic condition. In the last years, Magnetic Resonance Imaging (MRI) is reaching an important role in the study of diffuse liver diseases moving from qualitative to quantitative assessment of liver parenchyma. In fact, this can allow noninvasive accurate and standardized assessment of diffuse liver diseases and can represent a concrete alternative to biopsy which represents the current reference standard. MRI approach already tested for other pathologies include diffusion-weighted imaging (DWI) and radiomics, able to quantify different aspects of diffuse liver disease. New emerging MRI quantitative methods include MR elastography (MRE) for the quantification of the hepatic stiffness in cirrhotic patients, dedicated gradient multiecho sequences for the assessment of hepatic fat storage, and iron overload. Thus, the aim of this review is to give an overview of the technical principles and clinical application of new quantitative MRI techniques for the evaluation of diffuse liver disease.

Noninvasive staging of liver fibrosis: review of current quantitative CT and MRI-based techniques

Liver fibrosis features excessive protein accumulation in the liver interstitial space resulting from repeated tissue injury due to chronic liver disease. Liver fibrosis eventually proceeds to cirrhosis and associated complications. So, early diagnosis and staging of liver fibrosis are of vital importance for clinical treatment. Liver biopsy remains the gold standard for the diagnosing and staging of fibrosis, but it is suboptimal due to various limitations. Recently, efforts have been made to migrate toward noninvasive techniques for assessing liver fibrosis. CT is relatively easy to perform, relatively standardized for different scanners, and does not require additional hardware in liver fibrosis staging. MRI is frequently performed to characterize indeterminate liver lesions. Because it does not use ionizing radiation and features high image contrast, its role has increased in the staging of liver fibrosis. More recently, several studies on liver fibrosis staging using deep learning algorithms in CT or MRI have been proposed and have shown meaningful results. In this review, we summarize the basic concept, diagnostic performance, and advantages and limitations of each technique to noninvasively stage liver fibrosis.

Staging Chronic Hepatitis B Related Liver Fibrosis with a Fractional Order Calculus Diffusion Model

RATIONALE AND OBJECTIVES

Accurately staging liver fibrosis is of great clinical significance. We aimed to evaluate the clinical potential of the non-Gaussian fractional order calculus (FROC) diffusion model in staging liver fibrosis.

MATERIALS AND METHODS

A total of 82 patients with chronic hepatitis B (CHB) were included in this prospective study. Diffusion weighted imaging (DWI)-derived parameters including the diffusion coefficient (D), fractional order parameter (β) and microstructural quantity (μ) sourced from FROC-DWI, and apparent diffusion coefficient (ADC) derived from mono-exponential DWI, as well as the aspartate aminotransferase-to-platelet ratio index (APRI) and fibrosis-4 (FIB-4) were calculated. Their correlations with fibrosis stages and the diagnostic efficacy in predicting liver fibrosis were assessed and compared.

RESULTS

D (r = -0.667), β (r = -0.671), μ (r = -0.481), and ADC (r = -0.665) displayed significant correlations with fibrosis stages (p < 0.001). D, β and ADC (p < 0.01) were independently associated with fibrosis; and compared to inflammatory activity, fibrosis was the independent factor significantly correlated with D, β and ADC (p < 0.001). There were no significant differences between the area under curves of D, β, μ or their combinations and ADC for predicting different fibrosis stages (p > 0.05). The diagnostic performance of the combined index with four diffusion metrics was better than D, β, μ or ADC used alone (p < 0.05) as well as APRI or FIB-4 (p < 0.01) in fibrosis staging.

CONCLUSION

FROC-DWI was valuable in staging liver fibrosis in patients with CHB, but there were no significant differences between the FROC-DWI parameters and the classical ADC. However, the combined DWI-derived index including D, β, μ and ADC offered the best diagnostic efficacy and may serve as a reliable tool for fibrosis evaluation, superior to APRI and FIB-4.

Comparison of diffusion-weighted imaging and MR elastography in staging liver fibrosis: a meta-analysis

PURPOSE

To compare the diagnostic performance of diffusion-weighted imaging (DWI), gradient-recalled echo-based magnetic resonance elastography (GRE-MRE), and spin-echo echo-planar imaging-based MRE (SE-EPI-MRE) in liver fibrosis staging.

METHODS

A systematic literature search was done to collect studies on the performance of DWI, GRE-MRE, and SE-EPI-MRE for diagnosing liver fibrosis. Pooled sensitivity, specificity, diagnostic odds ratio, positive and negative likelihood ratio, and a summary receiver operating characteristic (ROC) curve were estimated with a bivariate random effects model. Subgroup analyses on various study characteristics were performed.

RESULTS

Sixty studies with a total of 6620 patients were included in the meta-analysis. Pooled sensitivity and specificity of GRE-MRE and SE-EPI-MRE showed high diagnostic accuracy and did not differ significantly. The area under the summary ROC curve for all stages of fibrosis differed significantly between DWI (0.83-0.88) and either GRE-MRE (0.95-0.97) or SE-EPI-MRE (0.95-0.99). Substantial heterogeneity was detected for all three imaging methods.

CONCLUSIONS

Both GRE-MRE and SE-EPI-MRE are highly accurate for detection of each liver fibrosis stage, with high potential to replace liver biopsy. Although DWI had a moderate accuracy in distinguishing liver fibrosis, it could be regarded as an alternative to MRE, since it is widely available and easily implemented in routine liver MRI.

Evaluating the Histopathology of Pancreatic Ductal Adenocarcinoma by Intravoxel Incoherent Motion-Diffusion Weighted Imaging Comparing With Diffusion-Weighted Imaging

Objectives

To explore the differences between intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) and diffusion-weighted imaging (DWI) in evaluating the histopathological characters of pancreatic ductal adenocarcinoma (PDAC).

Methods

This retrospective study enrolled 50 patients with PDAC confirmed by pathology from December 2018 to May 2020. All patients underwent DWI and IVIM-DWI before surgeries. Patients were classified into low- and high-fibrosis groups. Apparent diffusion coefficient (ADC), diffusion coefficient (D), false diffusion coefficient (D*), and perfusion fraction (f) were measured by two radiologists, respectively in GE AW 4.7 post-processing station, wherein ADC values were derived by mono-exponential fits and f, D, D* values were derived by biexponential fits. The tumor tissue was stained with Sirius red, CD34, and CK19 to evaluate fibrosis, microvascular density (MVD), and tumor cell density. Furthermore, the correlation between ADC, D, D*, and f values and histopathological results was analyzed.

Results

The D values were lower in the high-fibrosis group than in the low-fibrosis group, while the f values were opposite. Further, no statistically significant differences were detected in ADC and D* values between the high- and low-fibrosis groups. The AUC of D and f values had higher evaluation efficacy in the high- and low-fibrosis groups than ADC values. A significant negative correlation was established between D values, and fibrosis and a significant positive correlation were observed between f values and fibrosis. No statistical difference was detected between DWI/IVIM parameters values and MVD or tumor cell density except for the positive correlation between D* values and tumor cell density.

Conclusions

D and f values derived from the IVIM model had higher sensitivity and diagnostic performance for grading fibrosis in PDAC compared to the conventional DWI model. IVIM-DWI may have the potential as an imaging biomarker for predicting the fibrosis grade of PDAC.

A study of the correlations between IVIM-DWI parameters and the histologic differentiation of hepatocellular carcinoma

The present study aimed to investigate the value of intravoxel incoherent motion diffusion weighted imaging (IVIM-DWI) in the preoperative prediction of the histologic differentiation of hepatocellular carcinoma (HCC). Seventy HCC patients were scanned with a 3.0 T magnetic resonance scanner. The values of apparent diffusion coefficient (ADC), slow apparent diffusion coefficient (D), fast apparent diffusion coefficient (D*), and the fraction of the fast apparent diffusion coefficient (f) were measured. Analysis of variance was used to compare the differences in parameters between groups with different degrees of histologic differentiation. p < 0.05 was considered statistically significant. Receiver operating characteristic (ROC) curves were used to analyse the efficacy of IVIM-DWI parameters for predicting the histologic differentiation of HCC. The ADC and D values for well, moderately and poorly differentiated HCC were 1.35 ± 0.17 × 10^-3 mm²/s, 1.16 ± 0.17 × 10^-3 mm²/s, 0.98 ± 0.21 × 10^-3 mm²/s, and 1.06 ± 0.15 × 10^-3 mm²/s, 0.88 ± 0.16 × 10^-3 mm²/s, 0.76 ± 0.18 × 10^-3 mm²/s, respectively, and all differences were significant. The D* and f values of the three groups were 32.87 ± 14.70 × 10^-3 mm²/s, 41.68 ± 17.90 × 10^-3 mm²/s, 34.54 ± 18.60 × 10^-3 mm²/s and 0.22 ± 0.07, 0.23 ± 0.08, 0.18 ± 0.07, respectively, with no significant difference. When the cut-off values of ADC and D were 1.25 × 10^-3 mm²/s and 0.97 × 10^-3 mm²/s, respectively, their diagnostic sensitivities and specificities for distinguishing well differentiated HCC from moderately differentiated and poorly differentiated HCC were 73.3%, 85.5%, 86.7%, and 78.2%, and their areas under the ROC curve were 0.821 and 0.841, respectively. ADC and D values can be used preoperatively to predict the degree of histologic differentiation in HCC, and the D value has better diagnostic value.

A study of the correlations between IVIM-DWI parameters and the histologic differentiation of hepatocellular carcinoma

The present study aimed to investigate the value of intravoxel incoherent motion diffusion weighted imaging (IVIM-DWI) in the preoperative prediction of the histologic differentiation of hepatocellular carcinoma (HCC). Seventy HCC patients were scanned with a 3.0 T magnetic resonance scanner. The values of apparent diffusion coefficient (ADC), slow apparent diffusion coefficient (D), fast apparent diffusion coefficient (D*), and the fraction of the fast apparent diffusion coefficient (f) were measured. Analysis of variance was used to compare the differences in parameters between groups with different degrees of histologic differentiation. p < 0.05 was considered statistically significant. Receiver operating characteristic (ROC) curves were used to analyse the efficacy of IVIM-DWI parameters for predicting the histologic differentiation of HCC. The ADC and D values for well, moderately and poorly differentiated HCC were 1.35 ± 0.17 × 10⁻³ mm²/s, 1.16 ± 0.17 × 10⁻³ mm²/s, 0.98 ± 0.21 × 10⁻³ mm²/s, and 1.06 ± 0.15 × 10⁻³ mm²/s, 0.88 ± 0.16 × 10⁻³ mm²/s, 0.76 ± 0.18 × 10⁻³ mm²/s, respectively, and all differences were significant. The D* and f values of the three groups were 32.87 ± 14.70 × 10⁻³ mm²/s, 41.68 ± 17.90 × 10⁻³ mm²/s, 34.54 ± 18.60 × 10⁻³ mm²/s and 0.22 ± 0.07, 0.23 ± 0.08, 0.18 ± 0.07, respectively, with no significant difference. When the cut-off values of ADC and D were 1.25 × 10⁻³ mm²/s and 0.97 × 10⁻³ mm²/s, respectively, their diagnostic sensitivities and specificities for distinguishing well differentiated HCC from moderately differentiated and poorly differentiated HCC were 73.3%, 85.5%, 86.7%, and 78.2%, and their areas under the ROC curve were 0.821 and 0.841, respectively. ADC and D values can be used preoperatively to predict the degree of histologic differentiation in HCC, and the D value has better diagnostic value.

Noninvasive DW-MRI metrics for staging hepatic fibrosis and grading inflammatory activity in patients with chronic hepatitis B

PURPOSE

To assess the value of various diffusion parameters obtained from monoexponential, biexponential, and stretched-exponential diffusion-weighted imaging (DWI) models for staging hepatic fibrosis (HF) and grading inflammatory activity in patients with chronic hepatitis B (CHB).

METHODS

82 patients with CHB and 30 healthy volunteers underwent DWI with 13 b-values on a 3T MRI unit. The standard apparent diffusion coefficient (ADC_st) was calculated using a monoexponential model. The true diffusion coefficient (D_t), pseudo-diffusion coefficient (D_p), and perfusion fraction (f) were calculated using a biexponential model. The distributed diffusion coefficient (DDC) and water-molecule diffusion heterogeneity index (α) were calculated using a stretched-exponential model. Receiver operating characteristic (ROC) curves were performed for diffusion parameters to compare the diagnosis performance.

RESULTS

The distributions of hepatic fibrosis stages and the inflammatory activity grades (METAVIR scoring system) were as follows: F0, n = 1; F1, n = 16; F2, n = 31; F3, n = 19; and F4, n = 15. A0, n = 1; A1, n = 14; A2, n = 46; and A3, n = 21. ADC_st, D_t and DDC values showed negative correlation with the fibrosis stage (r = - 0.418, - 0.717 and - 0.630, all P < 0.001) and the inflammatory activity grade (r = - 0.514, - 0.626 and - 0.550, all P < 0.001). The area under the ROC curve (AUC) of D_t (AUC = 0.854, 0.881) and DDC (AUC = 0.794, 0.834) were significantly higher than that of ADC_st (AUC = 0.637, 0.717) in discriminating significant fibrosis (≥ F2) and advanced fibrosis (≥ F3) (all P < 0.05). Although D_t (AUC = 0.867, 0.836) and DDC (AUC = 0.810, 0.808) showed higher AUCs than ADC_st (AUC = 0.767, 0.803), there was no significant difference in their ability in detecting inflammatory activity grade ≥ A2/A3 (P > 0.05).

CONCLUSIONS

D_t and DDC are promising indicators and outperform ADC_st for staging HF. While both D_t and DDC have similar diagnostic performance compared with ADC_st for grading inflammatory activity.

Liver Fibrosis Assessment

Early diagnosis of hepatic fibrosis (HF) is pivotal for management to cease progression to cirrhosis and hepatocellular carcinoma. HF is the telltale sign of chronic liver disease, and confirmed by liver biopsy, which is an invasive technique and inclined to sampling errors. The morphologic parameters of cirrhosis are assessed on conventional imaging such as on ultrasound (US), computed tomography (CT) and magnetic resonance imaging (MRI). Newer imaging modalities such as magnetic resonance elastography and US elastography are reliable and accurate. More research studies on novel imaging modalities such as MRI with diffusion weighted imaging, enhancement by hepatobiliary contrast agents, and CT using perfusion are essential for earlier diagnosis, surveillance and accurate management. The purpose of this article is to discuss non-invasive CT, MRI, and US imaging modalities for diagnosis and stratify HF.

Noninvasive evaluation of liver fibrosis: comparison of the stretched exponential diffusion-weighted model to other diffusion-weighted MRI models and transient elastography

OBJECTIVES

To compare the diagnostic performance of the stretched exponential model to those of other DWI models and transient elastography (TE) and to evaluate the influence of confounding factors on the staging of liver fibrosis.

METHODS

This retrospective study included 78 consecutive patients who underwent both DWI and TE. The distributed diffusion coefficient (DDC) and intravoxel heterogeneity index (α) from the stretched exponential model, apparent diffusion coefficient (ADC), perfusion fraction (f), pseudodiffusion coefficient (D_p), true diffusion coefficient (D_t), and TE were obtained. Associations between imaging parameters and pathological fibrosis, inflammation, and steatosis were evaluated using Spearman's correlation and multiple regression analysis. Diagnostic accuracy of parameters for fibrosis staging was assessed via the Obuchowski measures.

RESULTS

DDC was the only parameter to differ between F0-1 and F2-3 (p < 0.001) and between F2-3 and F4 (p = 0.013). DDC showed significant correlation with fibrosis (p < 0.001) and inflammation (p = 0.001), but not with steatosis (p = 0.619), and was independently associated with only fibrosis in multiple regression analysis (β = - 0.114, p < 0.001). ADC, D_p, and D_t showed a significant correlation with steatosis (ps ≤ 0.038). DDC showed the highest diagnostic performance for liver fibrosis (0.717; 95% confidence interval, 0.653-0.765) followed by TE (0.681, 0.623-0.733) without a significant difference between DDC and TE (p > 0.999).

CONCLUSIONS

DDC from the stretched exponential model is the most accurate DWI parameter with no confounding effect from steatosis and with overall similar diagnostic performance to TE.

KEY POINTS

• The distributed diffusion coefficient (DDC) from the stretched exponential model is the most accurate DWI parameter for staging liver fibrosis. • DDC and transient elastography have similar good diagnostic performance for evaluating liver fibrosis. • The stretched exponential DWI model has no confounding effect by steatosis, unlike other DWI models.

CT and MR perfusion techniques to assess diffuse liver disease

Perfusion imaging allows for the quantitative extraction of physiological perfusion parameters of the liver microcirculation at levels far below the spatial the resolution of CT and MR imaging. Because of its peculiar structure and architecture, perfusion imaging is more challenging in the liver than in other organs. Indeed, the liver is a mobile organ and significantly deforms with respiratory motion. Moreover, it has a dual vascular supply and the sinusoidal capillaries are fenestrated in the normal liver. Using extracellular contrast agents, perfusion imaging has shown its ability to discriminate patients with various stages of liver fibrosis. The recent introduction of hepatobiliary contrast agents enables quantification of both the liver perfusion and the hepatocyte transport function using advanced perfusion models. The purpose of this review article is to describe the characteristics of liver perfusion imaging to assess chronic liver disease, with a special focus on CT and MR imaging.

Magnetic Resonance imaging analysis of liver fibrosis and inflammation: overwhelming gray zones restrict clinical use

Magnetic resonance (MR) identification and grading of subjects with liver fibrosis and inflammation represents a clinical challenge. MR elastography plays a well-defined role in fibrosis estimation, but its use is not widely available in clinical settings. Given that liver MR is becoming the reference standard for fat and iron quantitation, there is a need to clarify whether there is any role for MR imaging in the concomitant evaluation of fibrosis and inflammation in this setting. This review summarizes the diagnostic estimations of different MR imaging parameters obtained from conventional non-contrast-enhanced multiple b values diffusion-weighted acquisitions, variable flip angles T1 relaxation maps and STIR images. Although some derived parameters have shown a significant correlation to histological scores, a small magnitude of effect with wide overlap across severity grades is the rule. Contrary to fat and iron quantification, the low precision and reproducibility of MR imaging metrics limits its clinical relevance in fibrosis and inflammation assessment. In a sequential clinical approach combining different methodologies, MR imaging has no applicability for ruling-out and low accuracy for ruling-in advanced fibrosis. Thereby, MR elastography remains as the only image method with high diagnostic accuracy for the detection of advanced fibrosis. Until date, inflammation remains in a gray zone where biopsy cannot be replaced, and further investigations are needed. The present review offers an in-depth discuss of the MR imaging diagnostic performance for the evaluation of liver fibrosis and inflammation, highlighting the need for scientific improvements.

Diffusion-weighted imaging and texture analysis: current role for diffuse liver disease

Multiparametric MRI represents the primary imaging modality to assess diffuse liver disease, both in a qualitative and in a quantitative manner. Diffusion-weighted imaging (DWI) is among the imaging techniques that can be used to assess fibrosis due to its unique capability to assess microstructural changes at the tissue level. DWI is based on water mobility patterns and has the potential to become a non-invasive and non-destructive virtual biopsy to assess diffuse liver disease, overcoming sampling bias errors due to its three-dimensional imaging capabilities. Parallel to DWI, another quantitative method called texture analysis may be used to assess early and advanced diffused liver disease through quantifying spatial relationships in a global and local level, applying to any type of digital imaging technique like MRI or CT. Initial results using texture analysis hold great promise. In the current paper, we will review the role of DWI and texture analysis using MR images in assessing diffuse liver disease.

The feasibility and diagnostic value of intravoxel incoherent motion diffusion-weighted imaging in the assessment of myocardial fibrosis in hypertrophic cardiomyopathy patients

PURPOSE

To investigate the feasibility and diagnostic value of intravoxel incoherent motion (IVIM) in the assessment of myocardial fibrosis in hypertrophic cardiomyopathy (HCM) patients.

METHODS

Fifty-five HCM patients underwent IVIM diffusion-weighted cardiovascular resonance imaging; Cine, T1 mapping, IVIM and late gadolinium enhancement (LGE) were performed. The relationship of strain, pre T1, extracellular volume (ECV), IVIM-derived parameters (D, D* and f) and LGE were analyzed based on 16 American Heart Association segments. Abnormal segments of myocardial fibrosis were defined as: the presence of LGE (LGE+) or ECV ≥ 29.6 %.

RESULTS

D parameter was significantly increased in LGE + vs LGE- (1.89 ± 0.14 μm²/ms vs. 1.63 ± 0.12 μm²/ms, p < 0.001) and ECV ≥ 29.6 % vs ECV < 29.6 % (1.84 ± 0.13 μm²/ms vs. 1.61 ± 0.12 μm²/ms, p < 0.001), respectively. D* and f parameters were significantly decreased in LGE + vs LGE- (D*: 34.9 ± 6.6 μm²/m vs 55.2 ± 11.4 μm²/m, p < 0.001; f: 10.8 ± 1.29 % vs 12.5 ± 1.26 %, p < 0.001) and ECV ≥ 29.6 % vs ECV < 29.6 % (D*: 37.5 ± 6.9 μm²/m vs 59.6 ± 9.2 μm²/m, p < 0.001; f: 10.9 ± 1.1 % vs 13.00 ± 1.0 %, p = 0.021), respectively. Moreover, significant correlations were demonstrated between D and ECV, as well as D* and f.

CONCLUSIONS

IVIM DW-CMR has proven to be ingenious in the investigation of myocardial fibrosis; D* and f parameters may have potential value to assess the perfusion status of fibrotic regions in HCM patients.

Progress of intravoxel incoherent motion diffusion-weighted imaging in liver diseases

Traditional magnetic resonance (MR) diffusion-weighted imaging (DWI) uses a single exponential model to obtain the apparent diffusion coefficient to quantitatively reflect the diffusion motion of water molecules in living tissues, but it is affected by blood perfusion. Intravoxel incoherent motion (IVIM)-DWI utilizes a double-exponential model to obtain information on pure water molecule diffusion and microcirculatory perfusion-related diffusion, which compensates for the insufficiency of traditional DWI. In recent years, research on the application of IVIM-DWI in the diagnosis and treatment of hepatic diseases has gradually increased and has achieved considerable progress. This study mainly reviews the basic principles of IVIM-DWI and related research progress in the diagnosis and treatment of hepatic diseases.

Intravoxel incoherent motion parameters in the evaluation of chronic hepatitis B virus-induced hepatic injury: fibrosis and capillarity changes

OBJECTIVE

To evaluate the diagnostic efficacy of intravoxel incoherent motion (IVIM) parameters in hepatitis B virus (HBV)-induced hepatic fibrosis using different calculation methods and to investigate histopathologic origins.

MATERIALS AND METHODS

Liver biopsies from 37 prospectively recruited chronic hepatitis B patients were obtained. Twelve b-value (0-1000 s/mm²) diffusion-weighted imaging (DWI) was performed with a 1.5 T scanner and was followed by blinded percutaneous liver biopsy. All biopsy specimens were evaluated with Ishak staging, and the microvascular density (MVD) was calculated. Patients were classified as having no/mild (F0-1), moderate (F2-3), or marked (F4-5) fibrosis. Pseudodiffusion (D*), the perfusion fraction (f), and the apparent diffusion coefficient (ADC) were calculated using all b-values, while true diffusion (D) was calculated using all b-values [D_0-1000] and b-values greater than 200 s/mm² [D_200-1000]. Three concentric regions of interest (ROIs) (5, 10, and 20 mm) centered on the biopsy site were used.

RESULTS

D* was correlated with the MVD (p = 0.015, Pearson's r = 0.415), but f was not (p = 0.119). D_0-1000 was inversely correlated with Ishak stage (p = 0.000, Spearman's r_s =  - 0.685) and was significantly decreased in all the fibrosis groups; however, only the no/mild and marked fibrosis groups had significantly different D_200-1000 values. A pairwise comparison of receiver operating characteristic (ROC) curves of D_0-1000 and D_200-1000 showed significant differences (p = 0.039). D* was the best at discriminating early fibrosis (AUC = 0.861), while the ADC best discriminated advanced fibrosis (AUC = 0.964).

CONCLUSION

D* was correlated with the MVD and is a powerful parameter to discriminate early hepatic fibrosis. D significantly decreased with advanced fibrosis stage when using b-values less than 200 s/mm² in calculations.

Value of intravoxel incoherent motion in detecting and staging liver fibrosis: A meta-analysis

BACKGROUND

Liver fibrosis (LF) is a common pathological feature of all chronic liver diseases. With the accumulation of extracellular matrix in the fibrotic liver, true molecular water diffusion and perfusion-related diffusion are restricted. Intravoxel incoherent motion (IVIM) can capture the information on tissue diffusivity and microcapillary perfusion separately and reflect the fibrotic severity with diffusion coefficients.

AIM

To investigate the diagnostic performance of IVIM in detecting and staging LF with histology as a reference standard.

METHODS

A comprehensive literature search was conducted to identify studies on the diagnostic accuracy of IVIM for assessment of histologically proven LF. The stages of LF were classified as F0 (no fibrosis), F1 (portal fibrosis without septa), F2 (periportal fibrosis with few septa), F3 (septal fibrosis), and F4 (cirrhosis) according to histopathological findings. Data were extracted to calculate the pooled sensitivity, specificity, positive and negative likelihood ratios, and diagnostic odds ratio, as well as the area under the summary receiver operating characteristic curve (AUC) in each group.

RESULTS

A total of 12 studies with 923 subjects were included in this meta-analysis with 5 studies (n = 465) for LF ≥ F1, 9 studies (n = 757) for LF ≥ F2, 4 studies (n = 413) for LF ≥ F3, and 6 studies (n = 562) for LF = F4. The pooled sensitivity and specificity were estimated to be 0.78 (95% confidence interval: 0.73-0.82) and 0.81 (0.74-0.86) for LF ≥ F1 detection with IVIM; 0.82 (0.79-0.86) and 0.80 (0.75-0.84) for staging F2 fibrosis; 0.85 (0.79-0.90) and 0.83 (0.77-0.87) for staging F3 fibrosis, and 0.90 (0.84-0.94) and 0.75 (0.70-0.79) for detecting F4 cirrhosis, respectively. The AUCs for LF ≥ F1, F2, F3, F4 detection were 0.862 (0.811-0.914), 0.883 (0.856-0.909), 0.886 (0.865-0.907), and 0.899 (0.866-0.932), respectively. Moderate to substantial heterogeneity was observed with inconsistency index (I²) ranging from 0% to 77.9%. No publication bias was detected.

CONCLUSION

IVIM is a noninvasive tool with good diagnostic performance in detecting and staging LF. Optimized and standardized IVIM protocols are needed to further improve its diagnostic accuracy in clinical practice.

Intravoxel incoherent motion diffusion-weighted imaging to differentiate hepatocellular carcinoma from intrahepatic cholangiocarcinoma

The present study aimed to explore the value of intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) in differentiating hepatocellular carcinoma (HCC) from intrahepatic cholangiocarcinoma (ICC). This study included 65 patients with malignant hepatic nodules (55 with HCC, 10 with ICC), and 17 control patients with normal livers. All patients underwent IVIM-DWI scans on a 3.0 T magnetic resonance imaging (MRI) scanner. The standard apparent diffusion coefficient (ADC), pure diffusion coefficient (Dslow), pseudo-diffusion coefficient (Dfast), and perfusion fraction (f) were obtained. Differences in the parameters among the groups were analysed using one-way ANOVA, with p < 0.05 indicating statistical significance. Receiver operating characteristic (ROC) curve analysis was used to compare the efficacy of each parameter in differentiating HCC from ICC. ADC, Dslow, Dfast, f significantly differed among the three groups. ADC and Dslow were significantly lower in the HCC group than in the ICC group, while Dfast was significantly higher in the HCC group than in the ICC group; f did not significantly differ between the HCC and ICC groups. When the cut-off values of ADC, Dslow, and Dfast were 1.27 × 10−3 mm2/s, 0.81 × 10−3 mm2/s, and 26.04 × 10−3 mm2/s, respectively, their diagnostic sensitivities for differentiating HCC from ICC were 98.18%, 58.18%, and 94.55%, their diagnostic specificities were 50.00%, 80.00%, and 80.00%, and their areas under the ROC curve (AUCs) were 0.687, 0.721, and 0.896, respectively. Dfast displayed the largest AUC value. IVIM-DWI can be used to differentiate HCC from ICC.

Intravoxel incoherent motion diffusion-weighted imaging to differentiate hepatocellular carcinoma from intrahepatic cholangiocarcinoma

The present study aimed to explore the value of intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) in differentiating hepatocellular carcinoma (HCC) from intrahepatic cholangiocarcinoma (ICC). This study included 65 patients with malignant hepatic nodules (55 with HCC, 10 with ICC), and 17 control patients with normal livers. All patients underwent IVIM-DWI scans on a 3.0 T magnetic resonance imaging (MRI) scanner. The standard apparent diffusion coefficient (ADC), pure diffusion coefficient (D_slow), pseudo-diffusion coefficient (D_fast), and perfusion fraction (f) were obtained. Differences in the parameters among the groups were analysed using one-way ANOVA, with p < 0.05 indicating statistical significance. Receiver operating characteristic (ROC) curve analysis was used to compare the efficacy of each parameter in differentiating HCC from ICC. ADC, D_slow, D_fast, f significantly differed among the three groups. ADC and D_slow were significantly lower in the HCC group than in the ICC group, while D_fast was significantly higher in the HCC group than in the ICC group; f did not significantly differ between the HCC and ICC groups. When the cut-off values of ADC, D_slow, and D_fast were 1.27 × 10⁻³ mm²/s, 0.81 × 10⁻³ mm²/s, and 26.04 × 10⁻³ mm²/s, respectively, their diagnostic sensitivities for differentiating HCC from ICC were 98.18%, 58.18%, and 94.55%, their diagnostic specificities were 50.00%, 80.00%, and 80.00%, and their areas under the ROC curve (AUCs) were 0.687, 0.721, and 0.896, respectively. D_fast displayed the largest AUC value. IVIM-DWI can be used to differentiate HCC from ICC.

Liver lobe based intravoxel incoherent motion diffusion weighted imaging in hepatitis B related cirrhosis: Association with child-pugh class and esophageal and gastric fundic varices

Liver cirrhosis is a common chronic progressive liver disease in clinical practice, and intravoxel incoherent motion (IVIM) is a promising magnetic resonance method to assess liver cirrhosis, so our purpose was to investigate association of liver-lobe-based IVIM-derived parameters with hepatitis-B-related cirrhosis and its severity, and esophageal and gastric fundic varices. Seventy-four patients with hepatitis-B-related cirrhotic and 25 healthy volunteers were enrolled and underwent upper abdominal IVIM diffusion-weighted imaging with b-values of 0, 20, 50, 80, 100, 200, 400, 600, and 800 s/mm. IVIM-derived parameters (D, pure molecular diffusion; D, pseudo diffusion; and f, perfusion fraction) of left lateral lobe (LLL), left medial lobe (LML), right lobe (RL), and caudate lobe (CL) were assessed statistically to show their associations with cirrhosis and its severity, and esophageal and gastric fundic varices. In this research, we found that D, D, and f values of LLL, LML, RL, and CL were lower in cirrhotic liver than in normal liver (all P-values <.05). D, D, and f values of LLL, LML, RL, and CL were inversely correlated with Child-Pugh class of cirrhosis (r = -0.236 to -0.606, all P-values <.05). D of each liver lobe, D of LLL and CL, and f of LLL, LML, and CL in patients with esophageal and gastric fundic varices were lower than without the varices (all P-values <.05). D values of RL and CL could best identify cirrhosis, and identify esophageal and gastric fundic varices with areas under receiver-operating characteristic curve of 0.857 and 0.746, respectively. We concluded that liver-lobe-based IVIM-derived parameters can be associated with cirrhosis, and esophageal and gastric fundic varices.

Non-invasive assessment of hepatic fibrosis: comparison of MR elastography to transient elastography and intravoxel incoherent motion diffusion-weighted MRI

OBJECTIVE

To compare the ability of MR elastography (MRE) with transient elastography (TE) and intravoxel incoherent motion (IVIM) diffusion-weighted MRI in staging hepatic fibrosis (HF).

MATERIALS AND METHODS

100 patients with chronic liver disease and 25 healthy volunteers underwent preoperative MRE, IVIM on a 3T MRI unit, and ultrasound-based TE. Liver stiffness measurement from MRE (LSM-MRE) and liver stiffness measurement from TE (LSM-TE) were measured; four diffusion parameters including the true diffusion coefficient (D_t), pseudo-diffusion coefficient, perfusion fraction (f), and apparent diffusion coefficient (ADC) were calculated. Receiver operating characteristic (ROC) curves were performed for significant parameters to compare the diagnosis performance for detecting HF.

RESULTS

LSM-MRE and LSM-TE values showed positive correlation with the fibrosis stage (r = 0.910 and 0.813, P < 0.001). D_t, f, and ADC values showed negative correlation with the fibrosis stage (r = - 0.727, - 0.503, and - 0.601, all P < 0.001). The area under the ROC curve (AUC) of LSM-MRE (AUC = 0.965, 0.957, 0.983) was significantly higher than that of LSM-TE (AUC = 0.906, 0.913, 0.931) and D_t (AUC = 0.875, 0.879, 0.861) in discriminating significant HF (≥ F2), advanced HF (≥ F3), or cirrhosis (F4) (all P < 0.05). Although LSM-TE showed higher AUCs than D_t in detecting fibrosis stages, there were no significant differences between LSM-TE and D_t (P > 0.05) except for detecting F4 (P < 0.05).

CONCLUSION

MRE shows excellent diagnostic performance for predicting significant fibrosis, advanced fibrosis compared with TE and IVIM, while TE and IVIM have comparable diagnostic performance.

Intravoxel incoherent motion imaging for diagnosing and staging the liver fibrosis and inflammation

PURPOSE

To evaluate the diagnostic accuracy of intravoxel incoherent motion (IVIM) model parameters for the diagnosis and staging of liver fibrosis and inflammation in patients with chronic hepatitis B.

METHODS

Fifty-four patients with chronic hepatitis B and 42 healthy volunteers were included in the study. All subjects were examined by 3 T magnetic resonance imaging. Diffusion-weighted imaging was undertaken with sixteen b values. IVIM parameters [D (true diffusion coefficient), D* (pseudo-diffusion coefficient), f (perfusion fraction)] were calculated. Histological evaluation of biopsy samples was considered the reference standard for the staging of liver fibrosis and inflammation. Differences in IVIM parameters between patient and control groups were analyzed. In the patient group, fibrosis stage and inflammation grade groups were analyzed with respect to IVIM parameters. The correlation was assessed between IVIM parameters and Ishak-modified scale of fibrosis stages and inflammation grades.

RESULTS

The D was significantly lower in the patient group than the control group, p = 0.038 with Cohen's d effect size of 0.452. D was significantly different between fibrosis stage levels. D values decreased in fibrosis stages from the minimal to moderate to marked fibrosis. Fibrosis grades significantly negatively correlated with D and D* values, p = 0.001, and 0.021, respectively. In addition, inflammation grades negatively correlated with f values, p = 0.047.

CONCLUSION

D values measured with IVIM imaging may help to diagnose liver fibrosis. IVIM imaging could be an alternative to liver biopsy for the staging of liver fibrosis.

A comparative study of MR extracellular volume fraction measurement and two-dimensional shear-wave elastography in assessment of liver fibrosis with chronic hepatitis B

OBJECTIVE

To evaluate the value of MR liver extracellular volume (ECV_liver) in assessment of liver fibrosis with chronic hepatitis B (CHB), and to compare its performance with two-dimensional (2D) shear-wave elastography (SWE).

MATERIALS AND METHODS

A total of 68 CHB patients who were histologically diagnosed as fibrosis stages F0 to F4 were retrospectively analyzed. All patients underwent gadopentetate dimeglumine-enhanced T1-mapping and 2D SWE. ECV_liver and liver stiffness were measured and compared between fibrosis subgroups; their correlations with histologic findings were evaluated using Spearman correlation test and multiple regression analysis. Diagnostic performance in evaluating liver fibrosis stages was assessed and compared using receiver-operating characteristic analysis.

RESULTS

Both ECV_liver and liver stiffness increased as the fibrosis score increased (F = 17.08 to 10.99, P < 0.001). ECV_liver displayed a strong correlation with fibrosis stage (r = 0.740, P < 0.001), and liver stiffness displayed a moderate correlation (r = 0.651, P < 0.001); multivariate analysis revealed that only ECV_liver was independently correlated with fibrosis stage (P < 0.001). Univariate analyses showed significant correlations of ECV_liver with fibrosis stage, inflammatory activity, and platelet count; among all, the fibrosis stage had the highest correlation coefficient and was the only independent factor (P < 0.001). Overall, ECV_liver had no significant different performance compared with 2D SWE for the identification of both fibrosis stage s ≥ F2 and F4 (P = 0.868 and 0.171).

CONCLUSION

MR ECV_liver plays a promising role in the prediction of liver fibrosis for patients with CHB, comparable to 2D SWE.

Assessing liver fibrosis in chronic hepatitis B using MR extracellular volume measurements: Comparison with serum fibrosis indices

OBJECTIVES

To evaluate the diagnostic value of liver extracellular volume (ECV_liver) measurement by equilibrium MR in staging liver fibrosis in chronic hepatitis B (CHB) patients, and to compare its performance with serum fibrosis indices.

MATERIALS AND METHODS

91 CHB patients were included and underwent gadopentetate dimeglumine-enhanced MRI with T1 mapping sequence before and 15-min after contrast. ECV_liver, aspartate aminotransferase-to-platelet ratio index (APRI) and fibrosis index based on the four factors (FIB-4) were calculated and compared between fibrosis subgroups, and the correlations between the three indices and fibrosis stage or inflammatory activity were measured by Spearman correlation analysis and stepwise multiple regression analysis. Diagnostic performance in evaluating liver fibrosis stage was assessed and compared using receiver operating characteristic analysis.

RESULTS

Interobserver agreement showed an excellent interclass correlation coefficient of 0.895 for ECV_liver. ECV_liver, APRI and FIB-4 were different between fibrosis stages as a whole (F/H = 18.44-24.36, P ≤ 0.001). ECV_liver had the strongest correlation with fibrosis stage (r = 0.727, P < 0.001), while APRI and FIB-4 had weak correlations (r = 0.466 and 0.440, P < 0.001). Multivariate analysis showed that only ECV_liver was independently correlated with fibrosis stage (P < 0.001). The fibrosis stage was the only independent factor correlated with ECV_liver comparing to inflammatory activity (P < 0.001). AUCs of ECV_liver were larger than both APRI and FIB-4 in fibrosis staging, with significant differences in the diagnosis of advanced fibrosis (≥F3) and cirrhosis (F4) (P = 0.0024 to 0.0049).

CONCLUSION

MR ECV_liver provides a promising noninvasive tool in staging liver fibrosis for CHB patients, superior to the fibrosis indices of APRI and FIB-4.

Intravoxel Incoherent Motion (IVIM) Diffusion-Weighted Imaging (DWI) in Patients with Liver Dysfunction of Chronic Viral Hepatitis: Segmental Heterogeneity and Relationship with Child-Turcotte-Pugh Class at 3 Tesla

Background

Few studies focused on the region of interest- (ROI-) related heterogeneity of liver intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI). The aim of the study was to evaluate the differences of liver IVIM parameters among liver segments in cirrhotic livers (chronic viral hepatitis).

Material and Methods

This was a retrospective study of 82 consecutive patients with chronic liver disease who underwent MRI examination at the Jinan Infectious Diseases Hospital between January 2015 and December 2016. IVIM DWI (seven different b values) was performed on a Siemens 3.0-T MRI scanner. Pure molecular diffusion (D), pseudodiffusion (D^∗), and perfusion fraction (f) in different liver segments were evaluated.

Results

f, D, and D^∗ were different among the liver segments (all p < 0.05), indicating heterogeneity in IVIM parameters among liver segments. f was consistently higher in Child-Turcotte-Pugh (CTP) class A compared with CTP class B + C (p < 0.01). D and D^∗ were higher in CTP class A compared with CTP class B + C (p < 0.05). In patients with mean f value of >0.29, the AUC was 0.88 (95% CI: 0.81-0.96), with 86.8% sensitivity and 81.8% specificity for predicting CTP class A from CTP class B + C.

Conclusion

Liver IVIM could be a promising method for classifying the severity of segmental liver dysfunction of chronic viral hepatitis as evaluated by the CTP class, which provides a noninvasive alternative for evaluating segmental liver dysfunction with accurate selection of ROIs. Potentially it can be used to monitor the progression of CLD and LC in the future.

Reproducibility of intravoxel incoherent motion of liver on a 3.0T scanner: free-breathing and respiratory-triggered sequences acquired with different numbers of excitations

Purpose

To optimise the intravoxel incoherent motion (IVIM) imaging of the liver on a 3.0T scanner by assessing parameter reproducibility on free-breathing (FB) and respiratory-triggered (RT) sequences acquired with different numbers of signal averages (NSA).

Material and methods

In this prospective study 20 subjects (M/F: 10/10; age: 25-62 years, mean: 39 years) underwent IVIM magnetic resonance imaging (MRI) on a 3.0T scanner using an 18-channel phase-arrayed coil and four different echo-planar sequences, each with 10 b values: 0, 10, 30, 50, 75, 100, 150, 200, 500, and 900 s/mm². Images were acquired with FB and RT with NSA = 1-4 (FBNSA1-4, RTNSA1-4) and with NSA = 3-6 (FBNSA3-6, RTNSA3-6). Subsequently, for the assessment of reproducibility of IVIM-derived parameters (f, D, D*), each subject was scanned again with an identical protocol during the same session. IVIM parameters were calculated. The distribution of IVIM-parameters for each DWI sequence were given as the median value with first and third quartile. Inter-scan reproducibility for each IVIM parameter was evaluated using coefficient of variance and Bland-Altman difference. Differences between FB sequence and RT sequence were tested using non-parametric Wilcoxon signed-rank test.

Results

Mean coefficient of variance (%) for f, D, and D* ranged from 60 to 64, from 58 to 84, and from 82 to 99 for FBNSA1-4 sequence; from 50 to 69, from 41 to 97, and from 80 to 82 for RTNSA1-4 sequence; from 22 to 27, 15, and from 70 to 80 for FBNSA3-6 sequence; and from 21 to 32, from 12 to, and from 50 to 80 for RTNSA3-6 sequence, respectively.

Conclusions

Increasing the number of signal averages for IVIM acquisitions allows us to improve the reproducibility of IVIM-derived parameters. The sequence acquired during free-breathing with NSA = 3-6 was optimal in terms of reproducibility and acquisition time.

Histogram Analysis of Diffusion Kurtosis Magnetic Resonance Imaging for Diagnosis of Hepatic Fibrosis

Objective

To investigate the diagnostic value of diffusion kurtosis imaging (DKI) histogram analysis in hepatic fibrosis staging.

Materials and Methods

Thirty-six rats were divided into carbon tetrachloride-induced fibrosis groups (6 rats per group for 2, 4, 6, and 8 weeks) and a control group (n = 12). MRI was performed using a 3T scanner. Histograms of DKI were obtained for corrected apparent diffusion (D), kurtosis (K) and apparent diffusion coefficient (ADC). Mean, median, skewness, kurtosis and 25th and 75th percentiles were generated and compared according to the fibrosis stage and inflammatory activity.

Results

A total of 35 rats were included, and 12, 5, 5, 6, and 7 rats were diagnosed as F0–F4. The mean, median, 25th and 75th percentiles, kurtosis of D map, median, 25th percentile, skewness of K map, and 75th percentile of ADC map demonstrated significant correlation with fibrosis stage (r = −0.767 to 0.339, p < 0.001 to p = 0.039). The fibrosis score was the independent variable associated with histogram parameters compared with inflammatory activity grade (p < 0.001 to p = 0.041), except the median of K map (p = 0.185). Areas under the receiver operating characteristic curve of D were larger than K and ADC maps in fibrosis staging, although no significant differences existed in pairwise comparisons (p = 0.0512 to p = 0.847).

Conclusion

Corrected apparent diffusion of DKI histogram analysis provides added value and better diagnostic performance to detect various liver fibrosis stages compared with ADC.

Liver Fibrosis Quantification by Magnetic Resonance Imaging

Liver fibrosis is a hallmark of chronic liver disease characterized by the excessive accumulation of extracellular matrix proteins. Although liver biopsy is the reference standard for diagnosis and staging of liver fibrosis, it has some limitations, including potential pain, sampling variability, and low patient acceptance. Hence, there has been an effort to develop noninvasive imaging techniques for diagnosis, staging, and monitoring of liver fibrosis. Many quantitative techniques have been implemented on magnetic resonance imaging (MRI) for this indication. The most widely validated technique is magnetic resonance elastography, which aims to measure viscoelastic properties of the liver and relate them to fibrosis stage. Several additional MRI methods have been developed or adapted to liver fibrosis quantification. Diffusion-weighted imaging measures the Brownian motion of water molecules which is restricted by collagen fibers. Texture analysis assesses the changes in the texture of liver parenchyma associated with fibrosis. Perfusion imaging relies on signal intensity and pharmacokinetic models to extract quantitative perfusion parameters. Hepatocellular function, which decreases with increasing fibrosis stage, can be estimated by the uptake of hepatobiliary contrast agents. Strain imaging measures liver deformation in response to physiological motion such as cardiac contraction. T1ρ quantification is an investigational technique, which measures the spin-lattice relaxation time in the rotating frame. This article will review the MRI techniques used in liver fibrosis staging, their advantages and limitations, and diagnostic performance. We will briefly discuss future directions, such as longitudinal monitoring of disease, prediction of portal hypertension, and risk stratification of hepatocellular carcinoma.

Liver intravoxel incoherent motion diffusion-weighted imaging for the assessment of hepatic steatosis and fibrosis in children

AIM

To evaluate the correlation between intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI) parameters and the degree of hepatic steatosis and fibrosis in children.

METHODS

This retrospective study was approved by the institutional review board. The children (≤ 18 years) who underwent liver IVIM DWI with 8 b-values under the suspicion of hepatic steatosis or fibrosis from February 2013 to November 2016 were included. Subjects were divided into normal, fatty liver (FAT), and fibrotic liver (FIB) groups. The slow diffusion coefficient (D), fast diffusion coefficient (D*), perfusion fraction (f), and apparent diffusion coefficient (ADC) were measured. MR proton density fat fraction (PDFF), MR elastography (MRE), and IVIM values were compared.

RESULTS

A total of 123 children (median age of 12 years old, range: 6-18 years) were included, with 8 in the normal group, 93 in the FAT group, and 22 in the FIB group. The D* values were lower in the FIB group compared with those of the normal (P = 0.015) and FAT (P = 0.003) groups. The f values were lower in the FIB group compared with the FAT group (P = 0.001). In multivariate analyses, PDFF value was positively correlated with f value (β = 3.194, P < 0.001), and MRE value was negatively correlated with D* value (β = -7.031, P = 0.032). The D and ADC values were not influenced by PDFF or MRE value.

CONCLUSION

In liver IVIM DWI with multiple b-values in children, there was a positive correlation between hepatic fat and blood volume, and a negative correlation between hepatic stiffness and endovascular blood flow velocity, while diffusion-related parameters were not affected.

Prospective comparison of diffusion-weighted MRI and dynamic Gd-EOB-DTPA-enhanced MRI for detection and staging of hepatic fibrosis in primary sclerosing cholangitis

PURPOSE

To assess the diagnostic value of multiparametric magnetic resonance imaging (MRI) including dynamic Gd-EOB-DTPA-enhanced (DCE) and diffusion-weighted (DW) imaging for diagnosis and staging of hepatic fibrosis in primary sclerosing cholangitis (PSC) using transient elastography as a standard reference.

MATERIAL AND METHODS

Multiparametric MRI was prospectively performed on a 3.0-Tesla scanner in 47 patients (age 43.9±14.3 years). Transient elastography derived liver stiffness measurements (LSM), DCE-MRI derived parameters (hepatocellular uptake rate (Ki), arterial (Fa), portal venous (Fv) and total (Ft) blood flow, mean transit time (MTT), and extracellular volume (Ve)) and the apparent diffusion coefficient (ADC) were calculated. Correlation and univariate analysis of variance with post hoc pairwise comparison were applied to test for differences between LSM derived fibrosis stages (F0/F1, F2/3, F4). ROC curve analysis was used as a performance measure.

RESULTS

Both ADC and Ki correlated significantly with LSM (r= -0.614; p<0.001 and r= -0.368; p=0.01). The ADC significantly discriminated fibrosis stages F0/1 from F2/3 and F4 (p<0.001). Discrimination of F0/1 from F2/3 and F4 reached a sensitivity/specificity of 0.917/0.821 and 0.8/0.929, respectively. Despite significant inter-subject effect for classification of fibrosis stages, post hoc pairwise comparison was not significant for Ki (p>0.096 for F0/1 from F2/3 and F4). LSM, ADC and Ki were significantly associated with serum-based liver functional tests, disease duration and spleen volume.

CONCLUSION

DW-MRI provides a higher diagnostic performance for detection of hepatic fibrosis and cirrhosis in PSC patients in comparison to Gd-EOB-DTPA-enhanced DCE-MRI.

KEY POINTS

• Both ADC and hepatocellular uptake rate (Ki) correlate significantly with liver stiffness (r= -0.614; p<0.001 and r= -0.368; p=0.01). • The DCE-imaging derived quantitative parameter hepatocellular uptake rate (Ki) fails to discriminate pairwise intergroup differences of hepatic fibrosis (p>0.09). • DWI is preferable to DCE-imaging for discrimination of fibrosis stages F0/1 to F2/3 (p<0.001) and F4 (p<0.001).

Evaluation of liver fibrosis with a monoexponential model of intravoxel incoherent motion magnetic resonance imaging

To evaluate hepatic fibrosis with a monoexponential model of intravoxel incoherent motion magnetic resonance imaging, and assess the potential application value of intravoxel incoherent motion (IVIM) in diffusion-weighted imaging (IVIM-DWI) in determining staging of liver fibrosis. 28 patients with hepatic fibrosis and 25 volunteers with healthy livers had IVIM examination and conventional MRI. All standard apparent diffusion coefficient (ADC) values of IVIM raw data were post-processed off-line after completion of data collection. All regions of interest (ROIs) were manually positioned by two experienced radiologists. All values of the different fibrosis stages in the study group were compared using independent sample t tests. Using ROC analysis, both AUC values of ADC_total and ADC_{0-400-600-800} from study and control group were found to be between 0.8 and 1 for staging fibrosis. The mean ADC_total and ADC_{0-400-600-800} values of the liver in the study group were significantly lower than the values in the control group (P < 0.05). Spearman rho correlation analysis was used to determine the relationship among fibrosis stages and the ADC_total and ADC_{0-400-600-800} in the study group. As the stage of the fibrosis increased, the values decreased. Significant differences between the two subgroups of liver fibrosis stages were found (P < 0.05). The monoexponential model of IVIM-DWI adopted multiple b values for quantitative analysis of the water molecules diffused in the tissue. It could be used as a noninvasive and valuable method for assessment of liver fibrosis.

Does intravoxel incoherent motion reliably stage hepatic fibrosis, steatosis, and inflammation?

OBJECTIVE

To investigate the usefulness of intravoxel incoherent motion (IVIM) in determining the severity of hepatic fibrosis, steatosis, and inflammation in patients with chronic liver disease.

METHODS

Forty-nine patients who had liver MRI with IVIM sequence and liver biopsy within three months of MRI were enrolled. A reviewer, blinded to histology, placed regions of interest of 1-2 cm² in the right liver lobe. In addition, the first twenty patients were assessed with a second reviewer. Perfusion fraction (f), pseudodiffusion coefficient (D _fast), true diffusion coefficient (D _slow), and apparent diffusion coefficient (ADC) were calculated from normalized signal intensities that were fitted into a biexponential model. Errors in the model were minimized with global stochastic optimization using Simulated Annealing. ANOVA with post hoc Tukey-Kramer test and multivariate generalized linear model analysis were performed, using histological findings as the gold standard.

RESULTS

The most common etiologies for liver disease were hepatitis C and alcohol, accounting together for 76% (37/49) of patients. Low-grade fibrosis (F0, F1), hepatic steatosis, and inflammation were seen in 24% (12/49), 31% (15/49), and 29% (14/49) of patients, respectively. The interobserver correlation was poor for D _fast and D _slow (0.105, 0.173) and moderate for f and ADC (0.461, 0.418). ANOVA showed a strong inverse association between D _fast and liver fibrosis grade (p = 0.001). A weak inverse association was seen between ADC and hepatic steatosis (p = 0.059). Multivariate general linear model revealed that the only significant association between IVIM parameters and pathological features was between D _fast and fibrosis. On ROC curve analysis, D _fast < 23.4 × 10^-3 mm²/s had a sensitivity of 82.8% and a specificity of 64.3% in predicting high-grade fibrosis.

CONCLUSION

D _fast has the strongest association with hepatic fibrosis but has weak interobserver correlation. IVIM parameters were not significantly associated with hepatic inflammation or steatosis.

Liver fibrosis: stretched exponential model outperforms mono-exponential and bi-exponential models of diffusion-weighted MRI

OBJECTIVES

To compare the ability of diffusion-weighted imaging (DWI) parameters acquired from three different models for the diagnosis of hepatic fibrosis (HF).

METHODS

Ninety-five patients underwent DWI using nine b values at 3 T magnetic resonance. The hepatic apparent diffusion coefficient (ADC) from a mono-exponential model, the true diffusion coefficient (D _t ), pseudo-diffusion coefficient (D _p ) and perfusion fraction (f) from a biexponential model, and the distributed diffusion coefficient (DDC) and intravoxel heterogeneity index (α) from a stretched exponential model were compared with the pathological HF stage. For the stretched exponential model, parameters were also obtained using a dataset of six b values (DDC^#, α^#). The diagnostic performances of the parameters for HF staging were evaluated with Obuchowski measures and receiver operating characteristics (ROC) analysis. The measurement variability of DWI parameters was evaluated using the coefficient of variation (CoV).

RESULTS

Diagnostic accuracy for HF staging was highest for DDC^# (Obuchowski measures, 0.770 ± 0.03), and it was significantly higher than that of ADC (0.597 ± 0.05, p < 0.001), D _t (0.575 ± 0.05, p < 0.001) and f (0.669 ± 0.04, p = 0.035). The parameters from stretched exponential DWI and D _p showed higher areas under the ROC curve (AUCs) for determining significant fibrosis (≥F2) and cirrhosis (F = 4) than other parameters. However, D _p showed significantly higher measurement variability (CoV, 74.6%) than DDC^# (16.1%, p < 0.001) and α^# (15.1%, p < 0.001).

CONCLUSIONS

Stretched exponential DWI is a promising method for HF staging with good diagnostic performance and fewer b-value acquisitions, allowing shorter acquisition time.

KEY POINTS

• Stretched exponential DWI provides a precise and accurate model for HF staging. • Stretched exponential DWI parameters are more reliable than D _p from bi-exponential DWI model • Acquisition of six b values is sufficient to obtain accurate DDC and α.

MR imaging of hepatocellular adenomas on genotype-phenotype classification: A report from China

PURPOSE

To investigate and compare the MR features between hepatocellular adenoma (HCA) subtypes in China, including preliminary observations on diffusion-weighted imaging (DWI).

METHODS

Thirty-six patients with 39 pathologically proven HCAs underwent gadopentetate dimeglumine enhanced MRI. The morphological and imaging features on T1, T2-weighted, dynamic-enhanced imaging and DWI were retrospectively evaluated and compared between four HCA subtypes, using Kruskal-Wallis test, Fisher's exact test and Dunn-Bonferroni post hoc test.

RESULTS

HCA frequently occurred in male (n = 19, 52.8%), lacked an association with oral contraceptives (n = 0), and had a relatively high incidence of coexistent Hepatitis B infection (n = 6, 16.7%). Signals on T1 and T2-weighted imaging, enhancement pattern and intensity, lesion heterogeneity, as well as accompanying findings including lesion steatosis, necrosis or cystic component, central scar, and pseudocapsule were different between HCA subtypes (P < .0001 to P = .019). Apparent diffusion coefficient (ADC) values among HCA subtypes were different as a whole (P = .029), within which β-catenin-mutated HCA had the lowest ADCs; but post hoc comparisons demonstrated no significant differences between groups (P = .066-1.000).

CONCLUSION

Both clinical and MR imaging presentation of HCA in China had some specific characteristics, and a good relationship existed between MR data and genotype-phenotype classification. Furthermore, ADC value may provide a potential indicator of malignant transformation.

Intravoxel incoherent motion diffusion-weighted MR imaging for differentiation of benign and malignant musculoskeletal tumours at 3 T

OBJECTIVE

To evaluate the intravoxel incoherent motion (IVIM) diffusion-weighted (DW) MRI for differentiating between benign and malignant musculoskeletal tumours at 3 T.

METHODS

65 patients with treatment-naïve musculoskeletal tumours (47 malignant and 23 benign lesions) who underwent 3 T MRI including IVIM DW imaging were included. IVIM-derived parameters included pure diffusion coefficient (D), perfusion related incoherent microcirculation (D*, pseudodiffusion coefficient), and perfusion fraction (f). IVIM parameters and mono-exponential apparent diffusion coefficient (ADC) were retrospectively measured by two independent musculoskeletal radiologists.

RESULTS

D and ADC values of malignant tumours (923 ± 360, 965 ± 353 µm² s^-1, respectively) were significantly lower than those of benign tumours (1668 ± 546, 1689 ± 526 µm² s^-1) (p < 0.001). F values of malignant tumours (9.6%) were significantly higher than those of benign tumours (7.2%) (p = 0.021), whereas D* values showed no significant difference (p > 0.05). The area under the receiver operating characteristic (ROC) curve of D, ADC and f were 0.874, 0.880 and 0.671, respectively. Using cut-off values of D and ADC of 1200 µm² s^-1, the sensitivity, specificity and accuracy were 92, 83, 89%, 92, 87 and 90%, respectively.

CONCLUSION

D and ADC may be more accurate and reliable for differentiation of malignant from benign musculoskeletal tumours than f and D* at 3 T IVIM DW imaging. Advances in knowledge: Among IVIM-derived parameters, D is more accurate and reliable in differentiating malignant from benign musculoskeletal tumours than f and D* at 3.0T IVIM DW imaging. There was no significant difference in the diagnostic performance of D and ADC.

Role of MR in the differentiation of IgG4-related from non-IgG4-related hepatic inflammatory pseudotumor

BACKGROUND

Hepatic inflammatory pseudotumor (IPT) is classified into 2 types based on IgG4 stain: IgG4-related and non-IgG4-related; the two types differ not only in their pathological characteristics, but also in the clinical features. This study aimed to investigate the MR character of hepatic IPT, and differentiate the IgG4-related IPT from the non-IgG4-related IPT.

METHODS

Twenty-five patients with 27 histologically proven hepatic IPTs were retrospectively analyzed. Ten lesions were diagnosed as IgG4-related IPT, and the other 17 as non-IgG4-related IPT. The MR signal features on T1, T2-weighted, dynamic-enhanced, and diffusion-weighted imaging were evaluated and compared.

RESULTS

The dominant lesions were subcapsularly distributed (n=17, 63.0%) with clear boundary (n=20, 74.1%), and showed progressive enhancement pattern (n=21, 77.8%) with diffuse homogeneous (n=12, 44.4%) or heterogeneous (n=8, 29.6%) hyperintensity, accompanied by delayed capsule-like enhancement (n=17, 63.0%) and central nonenhanced areas (n=18, 66.7%). Morphological features (P>0.05) were not sufficient to differentiate IgG4-related IPT from non-IgG4-related IPT; the wash-out pattern was only found in 2 IgG4-related IPT, while the progressive enhancement pattern was more common in the non-IgG4-related lesions (n=16) (P=0.022). During portal and delayed phases, iso-/hypoenhanced lesions were only seen in 3 IgG4-related IPT, and circular-enhanced lesions (n=5) existed exceptionally in the non-IgG4-related group with significant differences (P=0.029 and 0.027). Most IgG4-related IPTs had lower apparent diffusion coefficient compared with the liver parenchyma (n=6), while most non-IgG4-related IPTs had higher apparent diffusion coefficient value (n=13) (P=0.046).

CONCLUSIONS

Although MR images of hepatic IPT have certain characteristics, they are not enough to differentiate IgG4-related IPT from non-IgG4-related IPT. The enhancement pattern, signal features on portal and delayed phases, and the apparent diffusion coefficient value of the lesion may be helpful for the diagnosis.

Liver fibrosis: in vivo evaluation using intravoxel incoherent motion-derived histogram metrics with histopathologic findings at 3.0 T

PURPOSE

To retrospectively determine the feasibility of intravoxel incoherent motion (IVIM) imaging based on histogram analysis for the staging of liver fibrosis (LF) using histopathologic findings as the reference standard.

METHODS

56 consecutive patients (14 men, 42 women; age range, 15-76, years) with chronic liver diseases (CLDs) were studied using IVIM-DWI with 9 b-values (0, 25, 50, 75, 100, 150, 200, 500, 800 s/mm²) at 3.0 T. Fibrosis stage was evaluated using the METAVIR scoring system. Histogram metrics including mean, standard deviation (Std), skewness, kurtosis, minimum (Min), maximum (Max), range, interquartile (Iq) range, and percentiles (10, 25, 50, 75, 90th) were extracted from apparent diffusion coefficient (ADC), true diffusion coefficient (D), pseudo-diffusion coefficient (D*), and perfusion fraction (f) maps. All histogram metrics among different fibrosis groups were compared using one-way analysis of variance or nonparametric Kruskal-Wallis test. For significant parameters, receivers operating characteristic curve (ROC) analyses were further performed for the staging of LF.

RESULTS

Based on their METAVIR stage, the 56 patients were reclassified into three groups as follows: F0-1 group (n = 25), F2-3 group (n = 21), and F4 group (n = 10). The mean, Iq range, percentiles (50, 75, and 90th) of D* maps between the groups were significant differences (all P < 0.05). Area under the ROC curve (AUC) of the mean, Iq range, 50, 75, and 90th percentile of D* maps for identifying significant LF (≥F2 stage) was 0.901, 0.859, 0.876, 0.943, and 0.886 (all P < 0.0001), respectively; for diagnosing severe fibrosis or cirrhosis (F4), AUC was 0.917, 0.922, 0.943, 0.985, and 0.939 (all P < 0.0001), respectively. The histogram metrics of ADC, D, and f maps demonstrated no significant difference among the groups (all P > 0.05).

CONCLUSION

Histogram analysis of D* map derived from IVIM can be used to stage liver fibrosis in patients with CLDs and provide more quantitative information beyond the mean value.

Imaging biomarkers in liver fibrosis

There is a need for early identification of patients with chronic liver diseases due to their increasing prevalence and morbidity-mortality. The degree of liver fibrosis determines the prognosis and therapeutic options in this population. Liver biopsy represents the reference standard for fibrosis staging. However, given its limitations and complications, different non-invasive methods have been developed recently for the in vivo quantification of fibrosis. Due to their precision and reliability, biomarkers' measurements derived from Ultrasound and Magnetic Resonance stand out. This article reviews the different acquisition techniques and image processing methods currently used in the evaluation of liver fibrosis, focusing on their diagnostic performance, applicability and clinical value. In order to properly interpret their results in the appropriate clinical context, it seems necessary to understand the techniques and their quality parameters, the standardization and validation of the measurement units and the quality control of the methodological problems.

Magnetic resonance elastography is as accurate as liver biopsy for liver fibrosis staging

BACKGROUND

Liver MR elastography (MRE) is available for the noninvasive assessment of liver fibrosis; however, no previous studies have compared the diagnostic ability of MRE with that of liver biopsy.

PURPOSE

To compare the diagnostic accuracy of liver fibrosis staging between MRE-based methods and liver biopsy using the resected liver specimens as the reference standard.

STUDY TYPE

A retrospective study at a single institution.

POPULATION

In all, 200 patients who underwent preoperative MRE and subsequent surgical liver resection were included in this study. Data from 80 patients were used to estimate cutoff and distributions of liver stiffness values measured by MRE for each liver fibrosis stage (F0-F4, METAVIR system). In the remaining 120 patients, liver biopsy specimens were obtained from the resected liver tissues using a standard biopsy needle.

FIELD STRENGTH/SEQUENCE

2D liver MRE with gradient-echo based sequence on a 1.5 or 3T scanner was used.

ASSESSMENT

Two radiologists independently measured the liver stiffness value on MRE and two types of MRE-based methods (threshold and Bayesian prediction method) were applied. Two pathologists evaluated all biopsy samples independently to stage liver fibrosis. Surgically resected whole tissue specimens were used as the reference standard.

STATISTICAL TESTS

The accuracy for liver fibrosis staging was compared between liver biopsy and MRE-based methods with a modified McNemar's test.

RESULTS

Accurate fibrosis staging was achieved in 53.3% (64/120) and 59.1% (71/120) of patients using MRE with threshold and Bayesian methods, respectively, and in 51.6% (62/120) with liver biopsy. Accuracies of MRE-based methods for diagnoses of ≥F2 (90-91% [108-9/120]), ≥F3 (79-81% [95-97/120]), and F4 (82-85% [98-102/120]) were statistically equivalent to those of liver biopsy (≥F2, 79% [95/120], P ≤ 0.01; ≥F3, 88% [105/120], P ≤ 0.006; and F4, 82% [99/120], P ≤ 0.017).

DATA CONCLUSION

MRE can be an alternative to liver biopsy for fibrosis staging.

LEVEL OF EVIDENCE

3. Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:1268-1275.

Assessment of liver fibrosis using T1 mapping on Gd-EOB-DTPA-enhanced magnetic resonance

BACKGROUND

Few studies have investigated the value of Gd-EOB-DTPA-enhanced T1 mapping in exact fibrosis staging, especially its correlation with hepatic molecular transporters.

AIMS

To investigate the diagnostic value of Gd-EOB-DTPA-enhanced T1 mapping in staging liver fibrosis and its relationship with hepatic molecular transporters.

METHODS

Thirty rats were divided into the carbon tetrachloride-induced fibrosis groups and a control group. T1-mapping was performed before and 20min after administration of Gd-EOB-DTPA. The T1 relaxation time and reduction rate (Δ%) were calculated, and their correlations with the degree of fibrosis, necroinflammatory activity, iron load and hepatic molecular transporters were assessed and compared.

RESULTS

Hepatobiliary phase T1 relaxation time (HBP) and Δ% were different between each adjacent fibrosis subgroups(P=0.000-0.042). Very strong correlations existed between fibrosis and both HBP and Δ% (r=0.960/-0.952), and multivariate analyses revealed that fibrosis was the only factor independently predicted by HBP (P=0.000) and Δ% (P=0.001), comparing to necroinflammatory activity and iron load. The expression of the organic anion transporting polypeptide1a1 (Oatp1a1) was significantly correlated with HBP and Δ% at both mRNA (r=-0.741/0.697) and protein (r=-0.577/0.602) levels. Weaker correlations were found for multidrug resistance associated protein2 (Mrp2). Generally, both transporters showed decreasing levels with increasing degrees of fibrosis.

CONCLUSION

Gd-EOB-DTPA-enhanced T1 mapping may provide a reliable diagnostic tool in staging liver fibrosis, and can be regarded as a useful imaging biomarker of hepatocyte transporter function.