Diffusion kurtosis imaging with the breath-hold technique for staging hepatic fibrosis: A preliminary study

Field-of-view optimized and constrained undistorted single shot intravoxel incoherent motion diffusion-weighted imaging of the cervix during the menstrual cycle: A prospective study

OBJECTIVE

To provide insight into the biological characteristics of the healthy cervix by defining intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) parameters across the menstrual cycle.

METHODS

Forty-three females of reproductive age (18-45 years old) were included in this prospective study. Conventional magnetic resonance imaging (MRI) and IVIM-DWI scans were performed at multiple time-points across the menstrual cycle: T1 (menses), T2 (follicular phase), T3 (luteal phase). Intra- and interobserver repeatability of the IVIM-DWI values were evaluated with intraclass correlation coefficients (ICC), and D* was excluded from the analyses due to poor repeatability. Differences in each IVIM-DWI parameter among T1, T2, and T3 were explored. Subjects were stratified by age and parity for subgroup analyses (younger [18 - < 30 years] vs. older [≥30-45 years]; parity 0 vs. parity 1 and 2). Correlations between subject age and IVIM-DWI parameters were assessed. The overlap for each IVIM-DWI parameter among T1, T2, and T3 was evaluated.

RESULTS

ADC and D values of the cervix were significantly lower at T3 compared with T1 (p = 0.02 and 0.03) or T2 (p < 0.01 and < 0.01). In younger subjects (n = 26), ADC and D values were significantly lower at T3 compared with T1 (p < 0.01 and p = 0.02) or T2 (p = 0.03 and p = 0.04). In older subjects (n = 17), ADC values were significantly higher at T2 compared with T1 (p = 0.01) or T3 (p = 0.01). There were significant differences in ADC values at T1 in subgroup analyses stratified by age and parity (both p < 0.01). There was a moderate correlation between age and ADC values at T1. Overlap for IVIM-DWI parameters across the menstrual cycle was >50%.

CONCLUSION

ADC and D values of the heathy cervix differed across the menstrual cycle. Age and parity may influence the ADC value.

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.

Noninvasive diagnosis of liver cirrhosis: qualitative and quantitative imaging biomarkers

A diagnosis of cirrhosis initiates a shift in the management of chronic liver disease and affects the diagnostic workflow and treatment decision of primary liver cancer. Liver biopsy remains the gold standard for cirrhosis diagnosis, but it is invasive and susceptible to sampling bias and observer variability. Various qualitative and quantitative imaging biomarkers based on ultrasound, CT and MRI have been proposed for noninvasive diagnosis of cirrhosis. Qualitative imaging features are easy to apply but have moderate diagnostic sensitivity. Elastography techniques allow quantitative assessment of liver stiffness and are highly accurate for cirrhosis diagnosis. Ultrasound elastography are widely used in clinical practice, while MR elastography has narrower availability. Although not applicable in clinical practice yet, other quantitative imaging features, including liver surface nodularity, linear and volumetric measurement, extracellular volume fraction, liver enhancement on hepatobiliary phase, and parameters derived from diffusion-weighted imaging, can provide additional information of liver morphology, perfusion, and function, thus may increase diagnosis performance. The introduction of radiomics and deep learning has further improved diagnostic accuracy while reducing subjectivity. Several imaging features may also help to assess liver function and outcomes in patients with cirrhosis. In this review, we summarize the qualitative and quantitative imaging biomarkers for noninvasive cirrhosis diagnosis, and the assessment of liver function and outcomes, and discuss the challenges and future directions in this field.

Staging liver fibrosis by a continuous-time random-walk diffusion model

PURPOSE

Noninvasive assessment of liver fibrosis holds significant clinical importance. We aimed to evaluate the clinical potential of using a continuous-time random-walk diffusion model (CTRW) for staging liver fibrosis.

METHODS

This prospective study included 52 patients suspected of liver disease and scheduled for liver biopsy. All patients underwent multi-b value diffusion-weighted imaging (DWI) using a 1.5 T MR scanner to derive the anomalous diffusion coefficient (D) and temporal (α) and spatial (β) diffusion heterogeneity indexes sourced from the CTRW. The mono-exponential DWI-derived apparent diffusion coefficient (ADC), transient elastography-derived liver stiffness measurement (LSM), aspartate aminotransferase-to-platelet ratio index (APRI), and fibrosis-4 (FIB-4) index were calculated. We assessed and compared the correlations of these parameters with fibrosis stages and their efficacy in staging liver fibrosis.

RESULTS

Significant correlations with fibrosis stages were found for APRI (r = 0.336), FIB-4 (r = 0.351), LSM (r = 0.523), D (r = -0.458), and ADC (r = -0.473). Significant differences were observed between APRI, LSM, D, and ADC of different fibrosis stages. The diagnostic performance of an index that combined D, α, β, ADC, and LSM was superior to that of ADC or LSM alone for fibrosis stage F ≥ 2 and better than the index that combined D, α, β for fibrosis stage F ≥ 4.

CONCLUSIONS

Accurate liver fibrosis staging was achieved with a model that combined CTRW-derived parameters (D, α, and β), ADC, and LSM. The model could serve as a reliable tool for noninvasive fibrosis evaluation.

Field-of-view optimized and constrained undistorted single-shot study of intravoxel incoherent motion and diffusion-weighted imaging of the uterus during the menstrual cycle: a prospective study

PURPOSE

This study aimed to compare the variability of the uterus during the menses phase (MP), follicular phase (FP), and luteal phase (LP) of the menstrual cycle using intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI).

METHODS

This prospective study was conducted at the Guangdong Provincial Hospital of Traditional Chinese Medicine between January 2022 and January 2023. Women of childbearing age (18-45 years) with appropriate progesterone levels were included in this study. Conventional magnetic resonance imaging and IVIM-DWI scans were performed during the MP, FP, and LP. The differences in IVIM-DWI-derived parameters between these phases were then compared, and the overlap was quantitatively described.

RESULTS

The apparent diffusion coefficient (ADC) and pure molecular diffusion coefficient (D) values from the endometrium, uterine junctional zone (UJZ), and myometrium indicated statistical differences between the MP and FP and the MP and LP (ADC: endometrium, both P < 0.001; UJZ, P = 0.008 and P < 0.001, respectively; myometrium, P = 0.033 and P = 0.006, respectively; D: endometrium, both P < 0.001; UJZ, P = 0.008 and P = 0.006, respectively; myometrium, P = 0.041 and P = 0.045, respectively). The perfusion-related diffusion coefficient (D*) values from the myometrium indicated statistical differences between the FP and MP and the FP and LP (D*: myometrium, P = 0.049 and P = 0.009, respectively). The overlapping endometrium ratios between the MP and FP or LP were lower than 50% in the ADC and D values (ADC: overlapping of MP and FP: 33.33%, overlapping of MP and LP: 23.33%; D: overlapping of MP and FP: 40.00%, overlapping of MP and LP: 43.33%).

CONCLUSION

The ADC and IVIM-derived parameters indicated differences in the uterus in diverse phases of the menstrual cycle, especially in the endometrium in relation to ADC and D values.

Galangin delivered by retinoic acid-modified nanoparticles targeted hepatic stellate cells for the treatment of hepatic fibrosis

Hepatic fibrosis (HF) is a chronic hepatic pathological process induced by various liver injuries, with few available therapies. Previous research studies revealed that HF is characterized by the accumulation of excess extracellular matrix in the liver, mainly overexpressed by activated hepatic stellate cells (HSC). Therefore, HSC have been targeted in clinical trials for the management of HF. The aim of the present study was to develop an anti-HF drug delivery system with acrylic resin (Eudragit® RS100, Eud RS100) nanoparticles (NPs) through modification by retinoic acid (RA), modified for binding the retinol-binding protein reporter (RBPR) in HSC. Galangin (GA), is a multiple effects flavonoid which has demonstrated an anti-HF effect in our previous studies. In this study, GA was utilized for the treatment of HF. The results revealed that the NPs were well formed (diameter: 70 nm), spherical in shape, and exhibited uniform distribution and a high encapsulation efficiency. Moreover, a prominent controlled release effect and a significant increase in bioavailability was observed following the encapsulation of GA in NPs. These findings indicated that the limitation of low bioavailability due to the hydrophobic feature of GA was overcome. Furthermore, the pharmacodynamics studies demonstrated that NPs could drastically influence the anti-HF effects of GA after modification with retinoic acid. The results of the present study suggested that retinoic acid-modified GA NPs represent a promising candidate in the development of an anti-HF drug delivery system for the treatment of HF.

Technical Advancements in Abdominal Diffusion-weighted Imaging

Since its first observation in the 18th century, the diffusion phenomenon has been actively studied by many researchers. Diffusion-weighted imaging (DWI) is a technique to probe the diffusion of water molecules and create a MR image with contrast based on the local diffusion properties. The DWI pixel intensity is modulated by the hindrance the diffusing water molecules experience. This hindrance is caused by structures in the tissue and reflects the state of the tissue. This characteristic makes DWI a unique and effective tool to gain more insight into the tissue's pathophysiological condition. In the past decades, DWI has made dramatic technical progress, leading to greater acceptance in clinical practice. In the abdominal region, however, acquiring DWI with good quality is challenging because of several reasons, such as large imaging volume, respiratory and other types of motion, and difficulty in achieving homogeneous fat suppression. In this review, we discuss technical advancements from the past decades that help mitigate these problems common in abdominal imaging. We describe the use of scan acceleration techniques such as parallel imaging and compressed sensing to reduce image distortion in echo planar imaging. Then we compare techniques developed to mitigate issues due to respiratory motion, such as free-breathing, respiratory-triggering, and navigator-based approaches. Commonly used fat suppression techniques are also introduced, and their effectiveness is discussed. Additionally, the influence of the abovementioned techniques on image quality is demonstrated. Finally, we discuss the current and future clinical applications of abdominal DWI, such as whole-body DWI, simultaneous multiple-slice excitation, intravoxel incoherent motion, and the use of artificial intelligence. Abdominal DWI has the potential to develop further in the future, thanks to scan acceleration and image quality improvement driven by technological advancements. The accumulation of clinical proof will further drive clinical acceptance.

Quantitative evaluation of hepatic fibrosis by fibro Scan and Gd-EOB-DTPA-enhanced T1 mapping magnetic resonance imaging in chronic hepatitis B

PURPOSE

Studies have found that both FibroScan (FS) and Gd-EOB-DTPA-enhanced T1 mapping magnetic resonance imaging (Gd-MRI) could assess liver fibrosis (LF) with high effectiveness. The aim of this study is to compare their accuracy in the quantitative evaluation of LF in patients with chronic hepatitis B (CHB), and to explore the diagnostic accuracy of their combination.

METHODS

160 patients with CHB were included in this study. FS and Gd-MRI were performed within 3 months before the pathological LF staging, which was classified according to the Scheuer-Ludwig scale. The liver stiffness measurement (LSM) was obtained by FS. T1 mapping images of the liver before and 20 min after enhancement were obtained by Look-Locker Gd-MRI.

RESULTS

There were 45, 35, 31 and 49 patients with stage S1, S2, S3 and S4 LF, respectively. LSM increased and the reduction rate of T1 relaxation time of 20 min (rrT1_20min%) decreased with the severity of LF. The area under curve (AUC) of LSM, rrT1_20min% and LSM + rrT1_20min% for the diagnosis of ≥ S2 LF were 0.892, 0.811 and 0.900, respectively. The AUC for ≥ S3 LF was 0.883, 0.838 and 0.899, respectively. The AUC for S4 LF was 0.882, 0.894 and 0.928, respectively.

CONCLUSION

The diagnostic accuracy of FS is better than that of Gd-MRI in the evaluation of ≥ S2 stage LF. The combination of these two methods significantly improved the diagnostic efficiency in the evaluation of S4 stage LF.

Magnetic resonance quantification of non-Gaussian water diffusion in hepatic fibrosis staging: a pilot study of diffusion kurtosis imaging to identify reversible hepatic fibrosis

Background

This study aimed to evaluate the diagnostic accuracy of diffusion kurtosis imaging (DKI) in differentiating early hepatic fibrosis (HF) from normal liver and advanced HF in rabbits.

Methods

A total of 35 healthy New Zealand white rabbits were included in the study. A model of HF was established in 30 rabbits through subcutaneous injections of 50% carbon tetrachloride (CCl₄)/olive oil, while 5 rabbits received saline injections. The gradually increased doses of CCl₄ were 0.1, 0.2, and 0.3 mL/kg in weeks 1 to 3, weeks 4 to 6, and weeks 7 to 10, respectively. Two injections were given each week. Two rabbits in the experimental group died. All rabbits underwent DKI with three b values (0, 500, and 1,000 s/mm²) at week 5 (n=8), week 6 (n=9), week 7 (n=8), and week 10 (n=8). Approximately 2 liver lobes per rabbit were selected for histopathology. Mean diffusivity (MD) and mean kurtosis (MK) were calculated. Discrimination capacities of DKI parameters were analyzed and compared by receiver operating characteristic (ROC) analysis.

Results

The meta-analysis of histological data in viral hepatitis (METAVIR) scoring system was used to classify liver lobes into the control group (F0, n=0), early HF group (F1-F2, n=28), and advanced HF group (F3-F4, n=28). MD and MK values were significantly different among the three groups (all P<0.05). MD value was negatively correlated with increased fibrosis level, while MK value was positively correlated with increased fibrosis level (ρ=-0.540, 0.614; P<0.05). The area under ROC curves (AUCs) for MD and MK were 0.886 and 0.875, respectively, for characterization of F0 and F1-F2, and 0.975 and 0.957 for F0 and F3-F4. AUC for MK was 0.751 for characterization of F1-F2 and F3-F4. MD performed better than MK for characterization of F0 and F1-F2 as well as F0 and F3-F4. MK showed good differentiation performance between F1-F2 and F3-F4.

Conclusions

Our results showed that DKI contributed to discriminating reversible early HF from normal liver and advanced HF and as a result, showed promise for use in HF diagnosis.

A novel identification system combining diffusion kurtosis imaging with conventional magnetic resonance imaging to assess intestinal strictures in patients with Crohn's disease

PURPOSE

To determine the utility of diffusion kurtosis imaging (DKI) for assessing bowel fibrosis and to establish a new magnetic resonance imaging (MRI)-based classification based on DKI and conventional MRI parameters for characterizing intestinal strictures in Crohn's disease (CD) using the histological evaluation of resected intestine samples as the reference standard.

METHODS

Thirty-one patients with CD undergoing preoperative conventional MRI and diffusion-weighted imaging (DWI) (b values = 0-2000 s/mm²) were consecutively enrolled. We classified the mural T2-weighted signal intensity and arterial-phase enhancement patterns on conventional MRI. We also measured DWI-derived apparent diffusion coefficients (ADCs) and DKI-derived apparent diffusion for non-Gaussian distribution (D_app) and apparent diffusional kurtosis (K_app). A new MRI-based classification was established to characterize intestinal strictures in CD. Its performance was validated in nine additional patients with CD.

RESULTS

Histological inflammation grades were significantly correlated to T2-weighted signal intensity (r = 0.477; P < 0.001) and ADC (r = - 0.226; P = 0.044). Histological fibrosis grades were moderately correlated to K_app (r = 0.604, P < 0.001); they were also correlated to D_app (r = - 0.491; P < 0.001) and ADC (r = - 0.270; P = 0.015). T2-weighted signal intensity could differentiate between no-to-mild and moderate-to-severe bowel inflammation (sensitivity, 0.970; specificity, 0.479). K_app could differentiate between no-to-mild and moderate-to-severe bowel fibrosis (sensitivity, 0.959; specificity, 0.781). The agreement between the new MRI-based classification and the histological classification was moderate in the test (κ = 0.507; P < 0.001) and validation (κ = 0.530; P < 0.001) sets.

CONCLUSIONS

DKI can be used to assess bowel fibrosis. The new MRI-based classification can help to distinguish between fibrotic and inflammatory intestinal strictures in patients with CD.

Comparison of MR-PWI quantitative and semi-quantitative parameters for the evaluation of liver fibrosis

Background

To evaluate different stages of liver fibrosis in cynomolgus monkeys by comparing magnetic resonance-perfusion weighted imaging (MR-PWI) quantitative and semi-quantitative parameters, and confirm the best detection indicators for diagnosis of liver fibrosis.

Methods

A liver fibrosis model of different stages (S0–S4) was established in cynomolgus monkeys. The changes in MR-PWI quantitative and semi-quantitative parameters with the progression of liver fibrosis were investigated.

Results

MR-PWI quantitative parameters gradually decreased with the progression of liver fibrosis. Hepatic arterial perfusion index (HPI) was found to increase with the progression of liver fibrosis and significant differences of HPI between each group were observed. There was a highly positive correlation between HPI and the stages of liver fibrosis. Receiver operating characteristic (ROC) curve analysis showed that HPI had the highest efficacy of the MR-PWI quantitative parameters for the diagnosis of liver fibrosis. The MR-PW semi-quantitative parameters gradually reduced with the progression of liver fibrosis, and the differences were statistically significant between stages S3–S4 and S0–S2. Time to peak (TPP) gradually extended and showed a positive correlation with the stages of liver fibrosis. TTP had the highest efficacy of the semi-quantitative parameters for diagnosis of liver fibrosis.

Conclusions

Both the MR-PWI quantitative and semi-quantitative parameters of the liver fibrosis model in cynomolgus monkeys varied at different stages of liver fibrosis, and HPI and TTP were the best detection indices for quantitative and semi-quantitative evaluation of liver fibrosis, respectively.

Differentiating mild and substantial hepatic fibrosis from healthy controls: a comparison of diffusion kurtosis imaging and conventional diffusion-weighted imaging

BACKGROUND

Early and accurate detection of liver fibrosis are important for clinical treatment.

PURPOSE

To compare the diagnostic accuracy of liver diffusion kurtosis imaging (DKI) and conventional diffusion-weighted imaging (cDWI) in differentiating patients with mild and substantial fibrosis from normal individuals.

MATERIAL AND METHODS

Twenty-seven healthy volunteers with no fibrosis (S0) and 45 patients with mild (S1) or substantial (S2) liver fibrosis underwent DWI with multiple b-values. Liver mean apparent diffusion (MD) and mean kurtosis (MK) values derived from DKI and apparent diffusion coefficient (ADC) derived from cDWI were measured and compared. Their discriminative abilities were analyzed and compared by receiver operating characteristic (ROC) curve analysis.

RESULTS

Significant differences in MD and ADC values were found between groups (P < 0.05). MD value was statistically different between S0 and S1 (P = 0.028) and S0 and S2 (P = 0.005). ADC value was statistically different between S0 and S2 (P = 0.012). MK value was similar between groups (P = 0.646). MD and ADC values significantly correlated with fibrosis stages (r_s = -0.668, -0.341; P < 0.01). MK values had no correlation with fibrosis stages (r_s = 0.180; P = 0.130). The area under ROC curves (AUC) for MD and ADC was 0.937 and 0.707 for characterization of S1-2 and 0.817 and 0.658 for S2, respectively. MD performed better than ADC for characterization of S1-2 and S2 (P < 0.05).

CONCLUSION

Differentiating patients with mild or substantial fibrosis from normal individuals is feasible using DKI, which performs better than cDWI.

Magnetic Resonance Diffusion Kurtosis Imaging versus Diffusion-Weighted Imaging in Evaluating the Pathological Grade of Hepatocellular Carcinoma

Purpose

To investigate the diagnostic efficacy of diffusion kurtosis imaging (DKI) and conventional diffusion-weighted imaging (DWI) for pathological grading.

Methods

From December 2015 to January 2017, consecutive patients suspected of having hepatocellular carcinoma (HCC) without prior treatment were prospectively enrolled in this study. MRI examinations were performed before surgical treatment. HCC patients confirmed by surgical pathology were included in the study. The mean diffusivity (MD) values, mean kurtosis (MK) values, and apparent diffusion coefficient (ADC) were calculated. The differences and correlations of these parameters among different pathological grades were analyzed. The diagnostic efficiency of DKI and DWI for predicting high-grade HCC was evaluated by receiver operating characteristic (ROC) curves. Logistic regression analyses were used to evaluate the predictive factors for pathological grade.

Results

A total of 128 patients (79 males and 49 females, age: 56.9±10.9 years, range, 32–80) with primary HCC were included: grade I: 22 (17.2%) patients, grade II: 37 (28.9%) patients, grade III: 43 (33.6%) patients, grade IV: 26 (20.3%) patients. The MK values of stage I, II, III, and IV were 0.86±0.13, 1.06±0.11, 1.27±0.17, and 1.57±0.13, respectively. The MK values were significantly higher in the high-grade group than in the low-grade group and were positively correlated with pathological grade (rho =0.7417, P<0.001). The MK value demonstrated a larger area under the curve (AUC), with a value of 0.93 than the MD value, which had an AUC of 0.815 (P<0.001), and ADC, which had an AUC of 0.662 (P=0.01). The MK value (>1.19), ADC (≤1.29×10^–3 mm²/s), and HBV (+) were independent predictors for the pathological grade of HCCs.

Conclusion

The MK values derived from DKI and the ADC values obtained from traditional DWI were more valuable than the MD values in predicting the histological grade of HCCs and could potentially guide clinical treatment before surgery.

Diffusion Kurtosis Imaging-A Superior Approach to Assess Tumor-Stroma Ratio in Pancreatic Ductal Adenocarcinoma

Extensive desmoplastic stroma is a hallmark of pancreatic ductal adenocarcinoma (PDAC) and contributes to tumor progression and to the relative resistance of tumor cells towards (radio) chemotherapy. Thus, therapies that target the stroma are under intense investigation. To allow the stratification of patients who would profit from such therapies, non-invasive methods assessing the stroma content in relation to tumor mass are required. In the current prospective study, we investigated the usefulness of diffusion-weighted magnetic resonance imaging (DW-MRI), a radiologic method that measures the random motion of water molecules in tissue, in the assessment of PDAC lesions, and more specifically in the desmoplastic tumor stroma. We made use of a sophisticated DW-MRI approach, the so-called diffusion kurtosis imaging (DKI), which possesses potential advantages over conventional and widely used monoexponential diffusion-weighted imaging analysis (cDWI). We found that the diffusion constant D from DKI is highly negatively correlated with the percentage of tumor stroma, the latter determined by histology. D performed significantly better than the widely used apparent diffusion coefficient (ADC) from cDWI in distinguishing stroma-rich (>50% stroma percentage) from stroma-poor tumors (≤50% stroma percentage). Moreover, we could prove the potential of the diffusion constant D as a clinically useful imaging parameter for the differentiation of PDAC-lesions from non-neoplastic pancreatic parenchyma. Therefore, the diffusion constant D from DKI could represent a valuable non-invasive imaging biomarker for assessment of stroma content in PDAC, which is applicable for the clinical diagnostic of PDAC.

Diffusion kurtosis imaging in liver: a preliminary reproducibility study in healthy volunteers

OBJECTIVES

To systematically test the reproducibility of DKI technique in normal liver and report a complete set of DKI measurement data.

MATERIALS AND METHODS

Thirty-two healthy volunteers were examined with liver DKI twice on the GE 3.0 T MRI scanner and reviewed by three professional experts. DKI-derived parameters fractional anisotropy of kurtosis (FAk), mean diffusivity (Md), axial diffusivity (Da), radial diffusivity (Dr), mean kurtosis (Mk), axial kurtosis (Ka), and radial kurtosis (Kr) in eight segments divided by Couinaud octagonal method were collected. Inter-class correlation coefficient (ICC) was used to assess the agreement between three experts. For each expert, the reproducibility of twice scans was evaluated by Bland-Altman method. Multivariate analysis of variance was to explore the regional distribution characteristics of DKI-derived parameters, and showed with box-plot graph.

RESULTS

Using ICC analysis, except for FAk (ICC 0.312, 0.307), other DKI metric values showed high reproducibility (0.716 < ICC < 0.907) between three experts for each of two DKI measurements. With Bland-Altman method, liver segment 5 (S5) showed the best reproducibility between two DKI measurement, and the reproducibility of segment 4 (S4) was the worst. The reproducibility of the right lobe was significantly higher than the left lobe. The values of diffusion metrics (Md, Da, and Dr) and kurtosis metrics (Mk, Ka, and Kr) existed significantly difference between the right and left hepatic lobes.

CONCLUSION

DKI has shown excellent reproducibility in liver imaging. The range of values for multiple DKI parameters, derived from the normal liver, was reported, and may provide data reference for further clinical DKI applications. Additionally, DKI technique is a non-invasive method to reflect the perfusion or structural differences between the left and right hepatic lobes from the molecular level.

Non-Gaussian Diffusion Models and T1 rho Quantification in the Assessment of Hepatic Sinusoidal Obstruction Syndrome in Rats

BACKGROUND

Non-Gaussian diffusion models and T₁ rho quantification may reflect the changes in tissue heterogeneity in hepatic sinusoidal obstruction syndrome (SOS).

PURPOSE

To investigate the feasibility of diffusion kurtosis imaging (DKI), stretched exponential model (SEM), and T₁ rho quantification in detecting and staging SOS in a monocrotaline (MCT)-induced rat model.

STUDY TYPE

Animal study.

POPULATION

Thirty male Sprague-Dawley rats gavaged with MCT to induce hepatic SOS and six male rats without any intervention.

FIELD STRENGTH/SEQUENCE

3.0T, DWI with five b-values (0-2000 s/mm² ) and T₁ rho with five spin lock times (1-60 msec).

ASSESSMENT

MRI was performed 1 day before and 1, 3, 5, 7, and 10 days after MCT administration. The corrected apparent diffusion coefficient (D_app ), kurtosis coefficient (K_app ), distributed diffusion coefficient (DDC), and intravoxel water molecular diffusion heterogeneity (α) were calculated from the corresponding non-Gaussian diffusion model. The T₁ rho value was calculated using a monoexponential model. Specimens obtained from the six timepoints were categorized into normal liver (n = 6), early-stage (n = 16), and late-stage (n = 14) SOS in accordance with the pathological score.

STATISTICAL TESTS

Parametric statistical methods and receiver operating characteristic (ROC) curves were employed to determine diagnostic accuracy.

RESULTS

The D_app , K_app , DDC, α, and T₁ rho values were correlated with pathological score with r values of -0.821, 0.726, -0.828, -0.739, and 0.714 (all P < 0.001), respectively. DKI (combined D_app and K_app ) and SEM (combined DDC and α) were better than T₁ rho for staging SOS. The areas under the ROC curve of DKI, SEM, and T₁ rho for differentiating normal liver and early-stage SOS were 0.97, 1.00, and 0.79, whereas those of DKI, SEM, and T₁ rho for differentiating early-stage and late-stage SOS were 1.00, 0.97, and 0.92, respectively.

DATA CONCLUSION

DKI, SEM, and T₁ rho may be helpful in staging SOS.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY STAGE: 2 J. Magn. Reson. Imaging 2020;52:1110-1121.

Evaluation of diffusion kurtosis imaging in stratification of nonalcoholic fatty liver disease and early diagnosis of nonalcoholic steatohepatitis in a rabbit model

PURPOSE

To examine the feasibility of MR diffusion kurtosis imaging (DKI) for characterizing nonalcoholic fatty liver disease (NAFLD) and diagnosing nonalcoholic steatohepatitis (NASH).

METHODS

Thirty-two rabbits on high fat diet with different severities of NAFLD were imaged at 3 T MR including diffusion weighted imaging (DWI) and DKI using b values of 0, 400, 800 s/mm² with 15 diffusion directions at each b value. Apparent diffusion coefficient (ADC) was derived from the linear exponential DWI model. Mean diffusion (MD) and mean kurtosis (MK) were derived from the quadratic exponential model of DKI. Correlations between MR parameters and hepatic pathology determined by the NAFLD activity scoring system were analyzed by Spearman rank correlation analysis. Receiver operating characteristic analyses were applied to determine the cutoff values of MD, MK as well as ADC in distinguishing NASH from non-NASH. The diagnostic efficacies of MD and MK in detecting NASH were compared with that of ADC.

RESULTS

Values for ADC and MD significantly decreased as the severity of NAFLD increased (ρ = -0.529, -0.904, respectively; P < 0.05). MK values significantly increased as the severity of NAFLD increased (ρ = 0.761; P < 0.05). In addition, both MD and MK values were significantly different between borderline NASH and NASH groups (MD: 1.729 ± 0.144 vs. 1.458 ± 0.240[×10^-3 mm²/s]; MK: 1.096 ± 0.079 vs. 1.237 ± 0.180; P < 0.05). Moreover, there was a significantly higher area under the curve (AUC) for both MD (0.955) and MK (0.905), as compared to ADC (0.736).

CONCLUSION

Diffusion kurtosis imaging was feasible for stratifying NAFLD, and more accurately discriminated NASH from non-NASH when compared with DWI.

Magnetic Resonance Diffusion Kurtosis Imaging for Evaluating Stage of Liver Fibrosis in a Rabbit Model

RATIONALE AND OBJECTIVES

As an extension of the conventional diffusion weighted imaging, diffusion kurtosis imaging (DKI) is based on the non-Gaussian diffusion model that can inherently account for restricted water diffusion within the complex microstructure of most tissues. This study aimed to investigate association of liver DKI derived parameter with stage of liver fibrosis.

MATERIALS AND METHODS

Fifty-six healthy New Zealand white rabbits were enrolled into this study, among which 48 rabbits were randomly given carbon tetrachloride to model liver fibrosis, and 8 rabbits treated with normal saline served as control subjects. All rabbits underwent liver DKI followed by biopsy to stage fibrosis (stages F0-F4) on 6th, 8th, 10th, and 12th weekends after initiation of modeling fibrosis. Mean kurtosis (MK), fractional anisotropy (FA), and mean diffusion (MD) were derived from DKI data. Statistical analysis was to evaluate association of DKI derived parameter with stage of fibrosis.

RESULTS

FA (r = 0.512) and MK (r = 0.567) increased, and MD (r = -0.574) decreased with increasing stage of fibrosis from F0 to F4 (all p values < 0.05). Significant differences were found in all parameters between F0 and F3 or F4, F1 and F4, F0 and F1-4, and F0-1 and F2-4 (all p values < 0.05). FA and MD could distinguish between F0 from F2, MD, and MK could distinguish F1 from F3, F0-2 from F3-4, and F1-2 from F3-4, and MK and FA could distinguish F2 from F4, and F0-3 from F4 (all p values < 0.05). According to receiver operating characteristic analysis, MK could best predict stage ≥F1, ≥F2, ≥F3, and F4, and discriminate F1-2 from F3-4 with areas under receiver operating characteristic curve of 0.766-0.930.

CONCLUSION

DKI derived parameters can help stage fibrosis.

Diffusion kurtosis imaging in the assessment of liver function: Its potential as an effective predictor of liver function

OBJECTIVES:

We aimed to determine whether diffusion kurtosis imaging (DKI) analysis with the breath-hold technique can replace liver function results obtained from laboratory tests.

METHODS:

Patients (n = 79) suspected of having a hepatobiliary disease, and control group without liver diseases (n = 15) were examined with non-Gaussian diffusion-weighted imaging using a 3.0 T magnetic resonance imaging unit. Based on the findings of DKI, various blood serum parameters, including the indocyanine green (ICG) retention rate 15 min after an intravenous injection of ICG (ICG-R15) and mean kurtosis values and Child-Pugh and albumin-bilirubin (ALBI) scores, were calculated. In total, 17 patients were tested using ICG-R15. For evaluating liver function, correlations between the mean kurtosis value and the Child-Pugh score, ALBI score, and ICG-R15 value as indicators of liver function obtained from blood data were assessed using Spearman's rank correlation. In apparent diffusion coefficient as well, we assessed correlations with these indicators.

RESULTS:

The mean kurtosis value correlated with the Child-Pugh score (Spearman's rank-correlation coefficient, ρ = 0.3992; p < 0.0001). Moreover, the mean kurtosis value revealed a correlation with the ICG-R15 value (Spearman's rank-correlation coefficient, ρ = 0.5972; p = 0.00114). The correlation between the mean kurtosis value and the ALBI score was the poorest among these (Spearman's rank-correlation coefficient, ρ = 0.3395; p = 0.0008).

CONCLUSION:

Liver function correlating with the Child-Pugh score and ICG-R15 value can be quantitatively estimated using the mean kurtosis value obtained from DKI analysis. DKI analysis with the breath-hold technique can be used to determine liver function instead of performing laboratory tests.

ADVANCES IN KNOWLEDGE:

Previous studies have not evaluated liver function in vivo using DKI.