Determination of malignancy and characterization of hepatic tumor type with diffusion-weighted magnetic resonance imaging: comparison of apparent diffusion coefficient and intravoxel incoherent motion-derived measurements. Invest Radiol. 2013;48:722-728. [PMID: 23669588 DOI: 10.1097/rli.0b013e3182915912]

A Platinum-Aluminum Bimetallic Salen Complex for Pro-senescence Cancer Therapy

Cell senescence is defined as irreversible cell cycle arrest, which can be triggered by telomere shortening or by various types of genotoxic stress. Induction of senescence is emerging as a new strategy for the treatment of cancer, especially when sequentially combined with a second senolytic drug capable of killing the resulting senescent cells, however severely suffering from the undesired off-target side effects from the senolytic drugs. Here, we prepare a bimetalic platinum-aluminum salen complex (Alumiplatin) for cancer therapy-a combination of pro-senesence chemotherapy with in situ senotherapy to avoid the side effects. The aluminum salen moiety, as a G-quadruplex stabilizer, enhances the salen's ability to induce cancer cell senescence and this phenotype is in turn sensitive to the cytotoxic activity of the monofunctional platinum moiety. It exhibits an excellent capability for inducing senescence, a potent cytotoxic activity against cancer cells both in vitro and in vivo, and an improved safety profile compared to cisplatin. Therefore, Alumiplatin may be a good candidate to be further developed into safe and effective anticancer agents. This novel combination of cell senescence inducers with genotoxic drugs revolutionizes the therapy options of designing multi-targeting anticancer agents to improve the efficacy of anticancer therapies.

Magnetic resonance elastography-derived stiffness: potential imaging biomarker for differentiation of benign and malignant pancreatic masses

OBJECTIVE

This study sought to determine the diagnostic performance of magnetic resonance elastography (MRE) for pancreatic solid masses, compared with diffusion-weighted imaging (DWI) and serum CA19-9, to establish a threshold for differentiating between pancreatic ductal adenocarcinoma (PDAC) and benign tumors in pancreas.

MATERIALS AND METHODS

Between July 2021 to January 2023, 75 adult patients confirmed with pancreatic solid tumors were enrolled in this prospective and consecutive study. All patients underwent MRE and DWI examinations that were both performed with a spin echo-EPI sequence. Stiffness maps and apparent diffusion coefficient (ADC) maps were generated, with MRE-derived mass stiffness and stiffness ratio (computing as the ratio of mass stiffness to the parenchyma stiffness) and DWI-derived ADC values obtained by placing regions of interest over the focal tumors on stiffness and ADC maps. Further analysis of comparing diagnostic performances was assessed by calculating the area under ROC curves.

RESULTS

PDAC had significantly higher tumor stiffness [3.795 (2.879-4.438) kPa vs. 2.359 (2.01-3.507) kPa, P = 0.0003], stiffness ratio [1.939 (1.562-2.511) vs. 1.187 (1.031-1.453), P < 0.0001] and serum CA19-9 level [276 (31.73-1055) vs. 10.45 (7.825-14.15), P < 0.0001] than other pancreatic masses. Mass stiffness, stiffness ratio and serum CA19-9 showed good diagnostic performance for differentiation with AUC of 0.7895, 0.8392 and 0.9136 respectively. The sensitivity/specificity/positive predictive value/negative predictive value for differentiating malignant from benign pancreatic tumors with mass stiffness (cutoff, > 2.8211 kPa) and stiffness ratio (cutoff, > 1.5117) were 78.4/66.7/82.9/60% and 77.8/83.3/90.3/65.2% respectively. The combined performance of Mass stiffness, stiffness ratio and serum CA19-9 got an AUC of 0.9758.

CONCLUSION

MRE holds excellent clinical potential in discriminating pancreatic ductal adenocarcinoma from other pancreatic solid masses according to their mechanical properties.

Histopathological graded liver lesions: what role does the IVIM analysis method have?

PURPOSE

This study aims to investigate three different image processing methods on quantitative parameters of IVIM sequence, as well as apparent diffusion coefficients and simple perfusion fractions, for benign and malignant liver tumors.

MATERIALS AND METHODS

IVIM images with 8 b-values (0-1000 s/mm2) and 1.5 T MRI scanner in 16 patients and 3 healthy people were obtained. Next, the regions of interest were selected for malignant, benign, and healthy liver regions (50, 56, and 12, respectively). Then, the bi-exponential equation of the IVIM technique was fitted with two segmented fitting methods as well as one full fitting method (three methods in total). Using the segmented fitting method, diffusion coefficient (D) is fixed with a mono-exponential equation with b-values that are greater than 200 s/mm2. The perfusion fraction (f) can then be calculated by extrapolating, as the first method, or fitting simultaneously with the pseudo-diffusion coefficient (D*) as the second method. In the full fitting method, as the third method, all IVIM parameters were obtained simultaneously. The mean values of parameters from different methods were compared in different grades of lesions.

RESULTS

Our results indicate that the image processing method can change statistical comparisons between different groups for each parameter. The D value is the only quantity in this technique that does not depend on the fitting process and can be used as an indicator of comparison between studies (P < 0.05). The most effective method to distinguish liver lesions is the extrapolated f method (first method). This method created a significant difference (P < 0.05) between the perfusion parameters between benign and malignant lesions.

CONCLUSION

Using extrapolated f is the most effective method of distinguishing liver lesions using IVIM parameters. The comparison between groups does not depend on the fitting method only for parameter D.

Application of intravoxel incoherent motion diffusion-weighted imaging in hepatocellular carcinoma

The morbidity and mortality of hepatocellular carcinoma (HCC) rank 6^th and 4^th, respectively, among malignant tumors worldwide. Traditional diffusion-weighted imaging (DWI) uses the apparent diffusion coefficient (ADC) obtained by applying the monoexponential model to reflect water molecule diffusion in active tissue; however, the value of ADC is affected by microcirculation perfusion. Using a biexponential model, intravoxel incoherent motion (IVIM)-DWI quantitatively measures information related to pure water molecule diffusion and microcirculation perfusion, thus compensating for the shortcomings of DWI. The number of studies examining the application of IVIM-DWI in patients with HCC has gradually increased over the last few years, and many results show that IVIM-DWI has vital value for HCC differentiation, pathological grading, and predicting and evaluating the treatment response. The present study principally reviews the principle of IVIM-DWI and its research progress in HCC differentiation, pathological grading, predicting and evaluating the treatment response, predicting postoperative recurrence and predicting gene expression prediction.

Comparison of different ROI analysis methods for liver lesion characterization with simplified intravoxel incoherent motion (IVIM)

This study investigated the impact of different ROI placement and analysis methods on the diagnostic performance of simplified IVIM-DWI for differentiating liver lesions. 1.5/3.0-T DWI data from a respiratory-gated MRI sequence (b = 0, 50, 250, 800 s/mm²) were analyzed in patients with malignant (n = 74/54) and benign (n = 35/19) lesions. Apparent diffusion coefficient ADC = ADC(0,800) and IVIM parameters D₁' = ADC(50,800), D₂' = ADC(250,800), f₁' = f(0,50,800), f₂' = f(0,250,800), and D*' = D*(0,50,250,800) were calculated voxel-wise. For each lesion, a representative 2D-ROI, a 3D-ROI whole lesion, and a 3D-ROI from "good" slices were placed, including and excluding centrally deviating areas (CDA) if present, and analyzed with various histogram metrics. The diagnostic performance of 2D- and 3D-ROIs was not significantly different; e.g. AUC (ADC/D₁'/f₁') were 0.958/0.902/0.622 for 2D- and 0.942/0.892/0.712 for whole lesion 3D-ROIs excluding CDA at 1.5 T (p > 0.05). For 2D- and 3D-ROIs, AUC (ADC/D₁'/D₂') were significantly higher, when CDA were excluded. With CDA included, AUC (ADC/D₁'/D₂'/f₁'/D*') improved when low percentiles were used instead of averages, and was then comparable to the results of average ROI analysis excluding CDA. For lesion differentiation the use of a representative 2D-ROI is sufficient. CDA should be excluded from ROIs by hand or automatically using low percentiles of diffusion coefficients.

The role of quantitative diffusion-weighted imaging in characterization of hypovascular liver lesions: A prospective comparison of intravoxel incoherent motion derived parameters and apparent diffusion coefficient

BACKGROUND

The utility of intravoxel incoherent motion (IVIM) related parameters in differentiation of hypovascular liver lesions is still unknown.

PURPOSE

The purpose of this study was to evaluate the value of IVIM related parameters in comparison to apparent diffusion coefficient (ADC) for differentiation among intrahepatic mass-forming cholangiocarcinoma (IMC), and hypovascular liver metastases (HLM).

METHODS

Seventy-four prospectively enrolled patients (21 IMC, and 53 HLM) underwent 1.5T magnetic resonance examination with IVIM diffusion-weighted imaging using seven b values (0-800 s/mm2). Two independent readers performed quantitative analysis of IVIM-related parameters and ADC. Interobserver reliability was tested using a intraclass correlation coefficient. ADC, true diffusion coefficient (D), perfusion-related diffusion coefficient (D*), and perfusion fraction (ƒ) were compared among the lesions using Kruskal-Wallis H test. The diagnostic accuracy of each parameter was assessed by receiver operating characteristic (ROC) curve analysis.

RESULTS

The interobserver agreement was good for ADC (0.802), and excellent for D, D*, and ƒ (0.911, 0.927, and 0.942, respectively). ADC, and D values were significantly different among IMC and HLM (both p < 0.05), while there was no significant difference among these lesions for ƒ and D* (p = 0.101, and p = 0.612, respectively). ROC analysis showed higher diagnostic performance of D in comparison to ADC (AUC = 0.879 vs 0.821).

CONCLUSION

IVIM-derived parameters in particular D, in addition to ADC, could help in differentiation between most common hypovascular malignant liver lesions, intrahepatic mass-forming cholangiocarcinoma and hypovascular liver metastases.

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 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.

Opposite responses of normal hepatocytes and hepatocellular carcinoma cells to substrate viscoelasticity

The cellular microenvironment plays a critical role in cell differentiation, proliferation, migration, and homeostasis. Recent studies have shown the importance of substrate viscosity in determining cellular function. Here, we study the mechanoresponse of normal hepatocytes and hepatocellular carcinoma cells (HCC) to elastic and viscoelastic substrates using the Huh7 cell line derived from a human liver tumor and primary human hepatocytes (PHH). Unlike PHH and fibroblasts, which respond to viscoelastic substrates by reducing spreading area and actin bundle assembly compared to purely elastic substrates of the same stiffness, Huh7 cells spread faster on viscoelastic substrates than on purely elastic substrates. The steady state spreading areas of Huh7 cells are larger on viscoelastic substrates, whereas the opposite effect occurs with PHH cells. The viscoelasticity of the microenvironment also promotes motility and multiple long protrusions in Huh7 cells. Pharmacologic disruption of the actin assembly makes cells unable to spread on either elastic or viscoelastic substrates. In contrast, upon vimentin perturbation, cells still spread to a limited degree on elastic substrates but are unable to spread on viscoelastic substrates. The time evolution of cell traction force shows that the peak occurs at an earlier time point on viscoelastic substrates compared to elastic substrates. However, the total force generation at steady state is the same on both substrates after 4 hours. Our data suggest that stress relaxation time scales of the viscoelastic substrate regulate cell dynamics and traction force generation, indicating different binding-unbinding rates of the proteins that form cell attachment sites in HCC cells and normal hepatocytes. These results suggest that liver cancer cells may have different characteristic lifetimes of binding to the substrate in comparision to normal cells, which might cause differences in cell spreading and motility within the diseased tissue.

A comparative study of monoexponential versus biexponential models of diffusion-weighted imaging in differentiating histologic grades of hepatitis B virus-related hepatocellular carcinoma

PURPOSE

To compare the diagnostic value of apparent diffusion coefficient (ADC) and intravoxel incoherent motion metrics in discriminating histologic grades of hepatocellular carcinoma (HCC) in patients with hepatitis B virus (HBV) infection.

METHODS

117 chronic HBV patients with 120 pathologically confirmed HCCs after surgical resection or liver transplantation were enrolled in this retrospective study. Diffusion-weighted imaging was performed using eleven b values (0-1500 s/mm²) and two b values (0, 800 s/mm²) successively on a 3.0 T system. ADC_{0, 800}, ADC_total, diffusion coefficient (D), pseudodiffusion coefficient (D*), and perfusion fraction (f) were calculated. The parameters of three histologically differentiated subtypes were investigated using Kruskal-Wallis test, Spearman rank correlation, and receiver-operating characteristic analysis. Interobserver agreement was assessed using the intraclass correlation coefficient.

RESULTS

There was excellent agreement for ADC_total/D/f, good agreement for ADC_0,800, and moderate agreement for D*. ADC_total, ADC_{0, 800,}D, and f were significantly different for well, moderately, and poorly differentiated HCCs (P < 0.001), and they were all inversely correlated with histologic grades: r = - 0.633, - 0.394, - 0.435, and - 0.358, respectively (P < 0.001). ADC_total demonstrated higher performance than ADC_0,800 in diagnosing both well and poorly differentiated HCCs (P < 0.001 and P = 0.04, respectively). ADC_total showed higher performance than D and f in diagnosing well differentiated HCCs (P < 0.001) and similar performance in diagnosing poorly differentiated HCCs (P = 0.06 and 0.13, respectively).

CONCLUSIONS

ADC_total showed better diagnostic performance than ADC_0,800, D, and f to discriminate histologic grades of HCC.

Role of Intravoxel Incoherent Motion in Discriminating Hepatitis B Virus-Related Intrahepatic Mass-Forming Cholangiocarcinoma from Hepatocellular Carcinoma Based on Liver Imaging Reporting and Data System v2018

Backgroud: Intravoxel incoherent motion (IVIM) could be used to characterize benign and malignant hepatic lesions and predict the histological grade of hepatocellular carcinoma (HCC). To evaluate IVIM-derived parameters for differentiating between hepatitis B virus (HBV)-related intrahepatic mass-forming cholangiocarcinoma (IMCC) and HCC based on the Liver Imaging Reporting and Data System (LI-RADS) v2018. Materials and Methods: 20 IMCC patients and one-to-one matched control HCC patients were retrospectively assessed. IVIM scanning with 11 b-values (from 0 to 1500 s/mm²) was obtained using a 3.0-T magnetic resonance scanner. Apparent diffusion coefficient (ADC) and IVIM parameters, including diffusion coefficient (D), pseudodiffusion coefficient (D*), and perfusion fraction (f), were compared between IMCC and HCC. Receiver operating characteristic (ROC) curve analysis was performed to assess the diagnostic performances of ADC, D, f, and D*. The LI-RADS features and a final category were also compared using LI-RADS v2018. Results: ADC and D were significantly higher in IMCC than in HCC (p = 0.012 and p = 0.007, respectively); f was significantly higher in HCC than in IMCC (p = 0.004). The area under the ROC curve values for ADC, D, and f for differentiating HBV-related IMCC from HCC were 0.724, 0.753, and 0.741, respectively. Conclusion: The majority of HBV-related IMCCs can be categorized as LR-M by using LI-RADS. However, atypical IMCCs may be classified as non-LR-M. ADC, D, and f values may be helpful in differentiating HBV-related IMCC from HCC, and similar diagnostic performances were obtained for these values.

Diffusion kurtosis imaging and conventional diffusion weighted imaging to assess electrochemotherapy response in locally advanced pancreatic cancer

Background The aim of the study was to evaluate diagnostic performance of functional parameters derived by conventional mono-exponential approach of diffusion weighted imaging (DWI) and by diffusion kurtosis imaging (DKI) in the assessment of pancreatic tumours treated with electrochemotherapy (ECT). Patients and methods Twenty-one consecutive patients with locally advanced pancreatic adenocarcinoma subjected to ECT were enrolled in a clinical approved trial. Among twenty-one enrolled patients, 13/21 (61.9%) patients were subjected to MRI before and after ECT. DWI was performed with a 1.5 T scanner; a free breathing axial single shot echo planar DWI pulse sequence parameters were acquired using seven b value = 0, 50, 100, 150, 400, 800, 1000 s/mm2. Apparent diffusion coefficient by conventional mono-exponential approach and mean of diffusion coefficient (MD) and mean of diffusional kurtosis (MK) by DKI approach were derived from DWI. Receiver operating characteristic (ROC) analysis was performed and sensitivity, specificity, positive and negative predictive value were calculated. Results Among investigated diffusion parameters, only the MD derived by DKI showed a significant variation of values between pre and post treatment (p = 0.02 at Wilcoxon test) and a significant statistically difference for percentage change between responders and not responders (p = 0.01 at Kruskal Wallis test). MD had a good diagnostic performance with a sensitivity of 80%, a specificity of 100% and area under ROC of 0.933. Conclusions MD derived by DKI allows identifying responders and not responders patients subject to ECT treatment. MD had higher diagnostic performance to assess ECT response compared to conventional DWI derived parameters.

Determination of Hepatocellular Carcinoma and Characterization of Hepatic Focal Lesions with Adaptive Multi-Exponential Intravoxel Incoherent Motion Model

PURPOSE: To distinguish hepatocellular carcinoma (HCC) from other types of hepatic lesions with the adaptive multi-exponential IVIM model. METHODS: 94 hepatic focal lesions, including 38 HCC, 16 metastasis, 12 focal nodular hyperplasia, 13 cholangiocarcinoma, and 15 hemangioma, were examined in this study. Diffusion-weighted images were acquired with 13 b values (b = 0, 3, …, 500 s/mm²) to measure the adaptive multi-exponential IVIM parameters, namely, pure diffusion coefficient (D), diffusion fraction (f_d), pseudo-diffusion coefficient (D_i*) and perfusion-related diffusion fraction (f_i) of the ith perfusion component. Comparison of the parameters of and their diagnostic performance was determined using Mann-Whitney U test, independent-sample t test, one-way analysis of variance, Z test and receiver-operating characteristic analysis. RESULTS: D, D₁* and D₂* presented significantly difference between HCCs and other hepatic lesions, whereas f_d, f₁ and f₂ did not show statistical differences. In the differential diagnosis of HCCs from other hepatic lesions, D₂* (AUC, 0.927) provided best diagnostic performance among all parameters. Additionally, the number of exponential terms in the model was also an important indicator for distinguishing HCCs from other hepatic lesions. In the benign and malignant analysis, D gave the greatest AUC values, 0.895 or 0.853, for differentiation between malignant and benign lesions with three or two exponential terms. Most parameters were not significantly different between hypovascular and hypervascular lesions. For multiple comparisons, significant differences of D, D₁* or D₂* were found between certain lesion types. CONCLUSION: The adaptive multi-exponential IVIM model was useful and reliable to distinguish HCC from other hepatic lesions.

Meta-analysis of intravoxel incoherent motion magnetic resonance imaging in differentiating focal lesions of the liver

INTRODUCTION

Accurate detection and characterization of focal liver lesions, including differentiation between malignant and benign lesions, are particularly important. The objective of this meta-analysis was to evaluate the parameters of intravoxel incoherent motion (IVIM), including apparent diffusion coefficient (ADC), pure molecular diffusion coefficient (D), perfusion-related diffusion coefficient (D*), and perfusion fraction (f) in differentiating focal liver lesions.

METHODS

IVIM method employed for focal liver lesion and the quality assessment of diagnostic studies were evaluated. Standardized mean differences and 95% confidence intervals were calculated. The heterogeneity was quantified with the I statistic.

RESULTS

The difference between groups was analyzed according to the I values from 6 different studies using fixed effects or random effects models. Significant differences in ADC (P < .001) and D (P < .001) were observed between benign and malignant lesions. Moreover, significant differences in ADC (P < .001), D (P < .001), and f (P = .01) were found between hemangioma and hepatocellular carcinoma (HCC). In addition, no significant difference was observed between the metastases and HCC.

CONCLUSIONS

D and ADC values were useful for the differentiation between benignity and malignancy; higher values of ADC, D, and f were observed in hemangioma compared to HCC. Nevertheless, IVIM did not result as the optimal approach for differentiation between the metastases and HCC.

Assessment of different mathematical models for diffusion-weighted imaging as quantitative biomarkers for differentiating benign from malignant solid hepatic lesions

To quantitatively compare the monoexponential, biexponential, and stretched‐exponential diffusion‐weighted imaging (DWI) models in differentiating benign from malignant solid hepatic lesions. The institutional review board approved this retrospective study and waived the informed consent requirement. A total of 188 patients with 288 hepatic lesions included 202 malignant lesions and 86 benign lesions were assessed (confirmed by pathology or clinical follow‐up for 6 months). All patients underwent hepatic 3.0‐T MRI, including multi‐b DWI that used 12 b values. The ADC, D_p, D_t, perfusion fraction (f_p), α, and DDC values for normal liver, benign liver lesions, and malignant liver lesions were calculated. Independent sample t tests were used for comparisons. The diagnostic performance of the parameters was evaluated using ROC analysis. The AUC value for each model was also calculated. The value of D_p was significantly lower in benign lesions than in normal hepatic parenchyma while others were significantly higher (P < .001). Whereas Values of D_t and α in malignant hepatic lesions were significantly higher than in normal hepatic parenchyma (P < .001), and the D_p value was significantly lower (P < .001). Values of ADC, f_p, DDC, and α for malignant hepatic lesions were significantly lower than those for benign hepatic lesions (P < .001). ROC analysis showed that the diagnostic value of the biexponential model of normal hepatic parenchyma vs benign hepatic lesions and normal hepatic parenchyma vs malignant hepatic lesions was high (0.946 and 0.876, respectively). In the differential diagnosis of benign and malignant hepatic lesions, DDC had the highest AUC value (0.819). The biexponential and stretched‐exponential DWI may provide additional information and improve the differential diagnosis of benign and malignant hepatic lesions compared with the monoexponential DWI.

Accurate IVIM model-based liver lesion characterisation can be achieved with only three b-value DWI

OBJECTIVE

The objective of this study was to evaluate a simplified intravoxel incoherent motion (IVIM) approach of diffusion-weighted imaging (DWI) with four b-values for liver lesion characterisation at 1.5 T.

METHODS

DWI data from a respiratory-gated MRI sequence with b = 0, 50, 250, 800 s/mm² were retrospectively analysed in 173 lesions and 40 healthy livers. The apparent diffusion coefficient ADC = ADC(0,800) and IVIM-based parameters D₁' = ADC(50,800), D₂' =ADC(250,800), f₁', f₂', D*', ADC_low = ADC(0,50), and ADC_diff=ADC_low-D₂' were calculated voxel-wise without fitting procedures. Differences between lesion groups were investigated.

RESULTS

Focal nodular hyperplasias were best discriminated from all other lesions by f₁' with an area under the curve (AUC) of 0.989. Haemangiomas were best discriminated by D₁' (AUC of 0.994). For discrimination between malignant and benign lesions, ADC(0,800) and D₁' were best suited (AUC of 0.915 and 0.858, respectively). Discriminatory power was further increased by using a combination of D₁' and f₁'.

CONCLUSION

IVIM parameters D and f approximated from three b-values provided more discriminatory power between liver lesions than ADC determined from two b-values. The use of b = 0, 50, 800 s/mm² was superior to that of b = 0, 250, 800 s/mm². The acquisition of four instead of three b-values has no further benefit for lesion characterisation.

KEY POINTS

• Diffusion and perfusion characteristics are assessable with only three b-values. • Association of b = 0, 50, 800 s/mm²is superior to b = 0, 250, 800 s/mm². • A fourth acquired b-value has no benefit for differential diagnosis. • For liver lesion characterisation, simplified IVIM analysis is superior to ADC determination. • Simplified IVIM approach guarantees numerically stable, voxel-wise results and short acquisition times.

Comparison of bi-exponential and mono-exponential models of diffusion-weighted imaging for detecting active sacroiliitis in ankylosing spondylitis

Background There has been a growing need for a sensitive and effective imaging method for the differentiation of the activity of ankylosing spondylitis (AS). Purpose To compare the performances of intravoxel incoherent motion (IVIM)-derived parameters and the apparent diffusion coefficient (ADC) for distinguishing AS-activity. Material and Methods One hundred patients with AS were divided into active (n = 51) and non-active groups (n = 49) and 21 healthy volunteers were included as control. The ADC, diffusion coefficient ( D), pseudodiffusion coefficient ( D*), and perfusion fraction ( f) were calculated for all groups. Kruskal-Wallis tests and receiver operator characteristic (ROC) curve analysis were performed for all parameters. Results There was good reproducibility of ADC /D and relatively poor reproducibility of D*/f. ADC, D, and f were significantly higher in the active group than in the non-active and control groups (all P < 0.0001, respectively). D* was slightly but significant lower in the active group than in the non-active and control group ( P = 0.0064, 0.0215). There was no significant difference in any parameter between the non-active group and the control group (all P > 0.050). In the ROC analysis, ADC had the largest AUC for distinguishing between the active group and the non-active group (0.988) and between the active and control groups (0.990). Multivariate logistic regression analysis models showed no diagnostic improvement. Conclusion ADC provided better diagnostic performance than IVIM-derived parameters in differentiating AS activity. Therefore, a straightforward and effective mono-exponential model of diffusion-weighted imaging may be sufficient for differentiating AS activity in the clinic.

Intravoxel incoherent motion: application in differentiation of hepatocellular carcinoma and focal nodular hyperplasia

PURPOSE

We aimed to explore whether intravoxel incoherent motion (IVIM)-related parameters of hepatocellular carcinoma (HCC) and focal nodular hyperplasia (FNH) demonstrate differences that could be used to differentiate and improve diagnostic efficiency.

METHODS

A total of 27 patients, including 22 with HCC and 5 with FNH, underwent liver 3.0 T magnetic resonance imaging for routine sequences. They were concurrently examined by IVIM diffusion-weighted imaging (DWI) scanning with 11 different b values (0-800 s/mm2). IVIM-derived parameters, such as pure diffusion coefficient (D), pseudo-diffusion coefficient (D*), perfusion fraction (f), and apparent diffusion coefficient (ADCtotal), were quantified automatically by post-processing software and compared between HCC and FNH groups. A receiver operating characteristic (ROC) curve was then created to predict their diagnostic value.

RESULTS

D* was weak in terms of reproducibility among the other parameters. ADCtotal, D, and D* were significantly lower in the HCC group than in the FNH group, while f did not show a significant difference. ADCtotal and D had the largest area under the curve values (AUC; 0.915 and 0.897, respectively) and similarly high efficacy to differentiate the two conditions.

CONCLUSION

IVIM provides a new modality to differentiate the HCC and FNH. ADCtotal and D demonstrated outstanding and comparable diagnosing utility.

Application values of 3.0T magnetic resonance diffusion weighted imaging for distinguishing liver malignant tumors and benign lesions

The aim of the present study was to investigate the significance and values of 3.0T diffusion weighted imaging (DWI) to differentially diagnose benign and malignant space-occupying liver lesions. A total of 91 patients with liver space-occupying lesions (145 lesions) were admitted into Zhongnan Hospital of Wuhan University (Wuhan, China) from November 2015 to May 2016. Routine scanning, DWI and high-resolution T2-weighted imaging using spin-echo echo-planar imaging were performed on all patients, to compare the apparent diffusion coefficient (ADC) values of three regions of interest in lesions with normal liver tissue. The ADC values of malignant liver lesions compared with benign liver cysts demonstrated a statistically significant difference in low b-value (P<0.05) and there was also a significant difference between malignant lesion and hepatic cyst, hepatic hemangioma or hepatic abscess in middle b-value (P<0.05). The measured ADC value may be more conducive to identify the nature of the liver space-occupying lesions; as the ADC values of malignant liver lesion, liver cyst, and liver abscesses demonstrated a statistical significance in high b-value (P<0.05). The mean ADC values between malignant liver tumors compared with benign lesions indicated a statistically significant difference. In the present study, liver space-occupying lesions demonstrated different DWI features and ADC ranges, and 3.0T DWI may be a potential means to accurately determine the nature of lesions, identifying benign and malignant space-occupying lesions.

Can diffusion-weighted imaging distinguish between benign and malignant pediatric liver tumors?

BACKGROUND

There are limited data on utility of diffusion-weighted imaging (DWI) in the evaluation of pediatric liver lesions.

OBJECTIVE

To determine whether qualitative and quantitative DWI can be used to differentiate benign and malignant pediatric liver lesions.

MATERIALS AND METHODS

We retrospectively reviewed MRIs in children with focal liver lesions to qualitatively evaluate lesions noting diffusion restriction, T2 shine-through, increased diffusion, hypointensity on DWI and apparent diffusion coefficient (ADC) maps, and intermediate signal on both, and to measure ADC values. Pathology confirmation or a combination of clinical, laboratory and imaging features, and follow-up was used to determine final diagnosis.

RESULTS

We included 112 focal hepatic lesions in 89 children (median age 11.5 years, 51 female), of which 92 lesions were benign and 20 malignant. Interobserver agreement was almost perfect for both qualitative (kappa 0.8735) and quantitative (intraclass correlation coefficient [ICC] 0.96) diffusion assessment. All malignant lesions showed diffusion restriction. Most benign lesions other than abscesses were not restricted. There was significant association of qualitative restriction with malignancy and non-restriction with benignancy (Fisher exact test P<0.0001). Mean normalized ADC values of malignant lesions (1.23x10^-3 mm²/s) were lower than benign lesions (1.62x10^-3 mm²/s; Student's t-test, P<0.015). However, there was significant overlap of ADC between benign and malignant lesions, with wide range for each diagnosis. Receiver operating characteristic (ROC) analysis revealed an area under the curve (AUC) of 0.63 for predicting malignancy using an ADC cut-off value of ≤1.20x10^-3 mm²/s, yielding a sensitivity of 78% and a specificity of 54% for differentiating malignant from benign lesions.

CONCLUSION

Qualitative diffusion restriction in pediatric liver lesions is a good predictor of malignancy and can help to differentiate between benign and malignant lesions, in conjunction with conventional MR sequences. Even though malignant lesions demonstrated significantly lower ADC values than benign lesions, the use of quantitative diffusion remains limited in its utility for distinguishing them because of the significant overlap and wide ranges of ADC values.

Intravoxel Incoherent Motion Diffusion-weighted Imaging: Evaluation of the Differentiation of Solid Hepatic Lesions

PURPOSE

To evaluate whether intravoxel incoherent motion (IVIM)-related parameters could be used to differentiate malignant from benign focal liver lesions (FLLs) and to improve diagnostic efficiency.

METHODS

Seventy-four patients with 75 lesions, including 51 malignant FLLs and 24 benign FLLs, underwent liver 3.0-T magnetic resonance imaging for routine examination sequences. IVIM diffusion-weighted imaging (DWI) with 11 b values (0-800s/mm²) was also acquired concurrently. Apparent diffusion coefficient (ADC_total) and IVIM-derived parameters, such as the pure diffusion coefficient (D), the pseudodiffusion coefficient (D^⁎), and the perfusion fraction (f), were calculated and compared between the two groups. A receiver operating characteristic curve analysis was performed to assess their diagnostic value.

RESULTS

ADC_total, D, and f were significantly lower in the malignant group than in the benign group, whereas D^⁎ did not show a statistical difference. D had a larger area under the curve value (0.968) and higher sensitivity (92.30%) for differentiation.

CONCLUSION

IVIM is a useful method to differentiate malignant and benign FLLs. The D value showed higher efficacy to detect hepatic solid lesions.

Intravoxel incoherent motion and dynamic contrast-enhanced MRI for differentiation between hepatocellular adenoma and focal nodular hyperplasia

OBJECTIVE

To examine if intravoxel incoherent motion (IVIM) and dynamic contrast-enhanced MRI (DCE-MRI) can be used as new and supplemental MRI techniques to differentiate hepatocellular adenomas (HCAs) from focal nodular hyperplasias (FNHs) and analyse if diffusion parameter apparent diffusion coefficient (ADC) and IVIM parameter true diffusion coefficient (D) differ in doing so.

METHODS

This prospective study included 21 patients (8 HCAs and 13 FNHs) who underwent a specifically designed MRI scanning protocol, including series for analysis of IVIM (four b-values 0, 10, 150 and 800 s mm^-2) and DCE-MRI. On a dedicated workstation, identical regions of interest were placed in parametric maps of K^trans, V_e, D and ADC in each lesion for quantification. Diagnostic accuracy was assessed using receiver operating characteristics analysis. Time-intensity curves (TICs) were classified in different types.

RESULTS

HCAs had significantly lower values for K^trans (mean 1.45 vs 2.68 min^-1; p = 0.029) and D (mean 1.02 × 10^-3 vs 1.22 × 10^-3 mm² s^-1; p = 0.033). Both parameters showed good diagnostic accuracy of 76%. TIC analysis could not differentiate between HCAs and FNHs.

CONCLUSION

In this exploratory study, K^trans and D were able to differentiate HCAs from FNHs in most cases, whereas V_e, ADC and TIC analysis were not. Advances in knowledge: Histological differences between HCAs and FNHs can be quantified on MRI using K^trans and D.

Chemotherapy response evaluation in a mouse model of gastric cancer using intravoxel incoherent motion diffusion-weighted MRI and histopathology

AIM

To determine the role of intravoxel incoherent motion (IVIM) diffusion-weighted (DW) magnetic resonance imaging (MRI) using a bi-exponential model in chemotherapy response evaluation in a gastric cancer mouse model.

METHODS

Mice bearing MKN-45 human gastric adenocarcinoma xenografts were divided into four treated groups (TG1, 2, 3 and 4, n = 5 in each group) which received Fluorouracil and Calcium Folinate and a control group (CG, n = 7). DW-MRI scans with 14 b-values (0-1500 s/mm²) were performed before and after treatment on days 3, 7, 14 and 21. Fast diffusion component (presumably pseudo-perfusion) parameters including the fast diffusion coefficient (D*) and fraction volume (f_p), slow diffusion coefficient (D) and the conventional apparent diffusion coefficients (ADC) were calculated by fitting the IVIM model to the measured DW signals. The median changes from the baseline to each post-treatment time point for each measurement (ΔADC, ΔD* and Δf_p) were calculated. The differences in the median changes between the two groups were compared using the mixed linear regression model by the restricted maximum likelihood method shown as z values. Histopathological analyses including Ki-67, CD31, TUNEL and H&E were conducted in conjunction with the MRI scans. The median percentage changes were compared with the histopathological analyses between the pre- and post-treatment for each measurement.

RESULTS

Compared with the control group, D* in the treated group decreased significantly (ΔD*_treated% = -30%, -34% and -20%, with z = -5.40, -4.18 and -1.95. P = 0.0001, 0.0001 and 0.0244) and f_p increased significantly (Δf_ptreated% = 93%, 113% and 181%, with z = 4.63, 5.52, and 2.12, P = 0.001, 0.0001 and 0.0336) on day 3, 7 and 14, respectively. Increases in ADC in the treated group were higher than those in the control group on days 3 and 14 (z = 2.44 and 2.40, P = 0.0147 and P = 0.0164).

CONCLUSION

Fast diffusion measurements derived from the bi-exponential IVIM model may be more sensitive imaging biomarkers than ADC to assess chemotherapy response in gastric adenocarcinoma.

The Therapeutic Response of Gastrointestinal Stromal Tumors to Imatinib Treatment Assessed by Intravoxel Incoherent Motion Diffusion-Weighted Magnetic Resonance Imaging with Histopathological Correlation

Purpose

To exploit the intravoxel incoherent motion (IVIM) diffusion-weighted (DW) MRI when evaluating the therapeutic response of gastrointestinal stromal tumors (GIST) to Imatinib in a mouse model.

Materials and Methods

Mice with xenografts bearing cells from the GIST-T1 cell line were randomly divided into a treated group receiving Imatinib and a control group. DWMRI scans with 14 b-values (0–1500 s/mm²) were performed before and after treatment (days 1, 3 and 7). IVIM related parameters perfusion fractions (fp) and perfusion-related diffusion coefficients (D*) and the conventional apparent diffusion coefficients (ADC) were calculated by fitting the DWMRI signal decay. The mean changes from baseline to each post-treatment time point for each measurement (ΔADC, Δfp and ΔD*) were calculated. The differences of mean changes between the two groups were tested for statistical significance. Histopathological analyses including Ki-67, CD31, TUNEL and H&E were conducted in conjunction with the MRI scans.

Results

Increases in ADC of the treated group were higher than those of the control group after treatment, whereas statistical significances were not observed. Compared to the control group, D* in the treated group decreased significantly (ΔD*_treated = -41%, -49%, and -49% with P = 0.0001, 0.0001 and 0.0001), and fp increased significantly (Δfp_treated = 79%, 82% and 110%, with P = 0.001, 0.0001 and P = 0.0007) on days 1, 3 and 7 after treatment. Histopathological analyses demonstrated different tumor tissue characteristics between the treated and control groups.

Conclusion

IVIM measurements may serve as more sensitive imaging biomarkers than ADC when assessing GIST response to Imatinib as early as one day after treatment.

Hepatic Fibrosis, Inflammation, and Steatosis: Influence on the MR Viscoelastic and Diffusion Parameters in Patients with Chronic Liver Disease

Purpose To determine the relationship of liver fibrosis, inflammation, and steatosis with the magnetic resonance (MR) viscoelastic and diffusion parameters in patients with chronic liver disease and to compare the diagnostic accuracy of the imaging parameters in staging liver fibrosis. Materials and Methods Consecutive patients with chronic liver disease scheduled for liver biopsy were prospectively recruited from November 2010 to October 2012 for this institutional review board-approved study after they provided written informed consent. Sixty-eight patients underwent three-dimensional MR elastography and intravoxel incoherent motion diffusion-weighted MR imaging with a 1.5-T MR system. Fibrosis, inflammation, and steatosis were assessed with the METAVIR and steatosis, activity, and fibrosis (or SAF) scoring systems. Spearman correlation and multiple regression analyses were performed to determine the relationship between liver fibrosis, inflammation, steatosis, and alanine aminotransferase (ALT) levels and viscoelastic and diffusion parameters. The accuracy of three-dimensional MR elastography and diffusion-weighted MR imaging in the determination of fibrosis stage was assessed with Obuchowski measures. Results At multiple regression analysis, fibrosis was the only variable associated with viscoelastic parameters (β = 0.6, P < .001, R² = 0.33 for shear modulus; β = 0.6, P < .001, R² = 0.32 for elasticity). Fibrosis had a weaker independent association with the apparent diffusion coefficient (β = -0.3, P = .02, R² = 0.33) than did steatosis (β = -0.5, P < .001, R² = 0.33). Steatosis was the only factor independently associated with the pure diffusion coefficient (β = -0.4, P = .002, R² = 0.22). Inflammation and ALT level were not associated with the viscoelastic or diffusion parameters. The diagnostic accuracy of fibrosis staging was significantly higher when measuring the shear modulus rather than the apparent diffusion coefficient (Obuchowski measures, 0.82 ± 0.04 vs 0.30 ± 0.06; P < .001). Conclusion Fibrosis is independently associated with the MR viscoelastic parameters and is less associated with the diffusion parameters than is steatosis. These results and those of diagnostic accuracy suggest that MR elastography should be preferred over diffusion-weighted MR imaging in the staging of liver fibrosis. ^© RSNA, 2016.

A Standardized Parameter-Free Algorithm for Combined Intravoxel Incoherent Motion and Diffusion Kurtosis Analysis of Diffusion Imaging Data

OBJECTIVES

The aims of this study were to implement and systematically evaluate the performance of a new parameter-free segmented algorithm for analysis of diffusion imaging data using a combined intravoxel incoherent motion and diffusion kurtosis imaging (IVIM-DKI) model of spin diffusion in comparison with the simpler intravoxel incoherent motion (IVIM) model.

MATERIALS AND METHODS

A multistep algorithm was implemented intended to separate diffusion kurtosis from IVIM effects in multi-b-value diffusion measurements using an adaptive b-value threshold technique. For each possible b-value threshold (separating diffusion and perfusion effects), diffusion kurtosis analysis of high b-values is followed by IVIM analysis keeping kurtosis parameters fixed. The b-value threshold with smallest Akaike information criterion is chosen as best model solution. The algorithm was tested in diffusion data sets of the upper abdomen from 8 healthy volunteers with 16 different b-values and compared with a standard multistep IVIM analysis.

RESULTS

The proposed algorithm could successfully be applied to all data sets and provided a significantly better fit of the observed signal decay in all assessed organs (all P < 0.03). Using the proposed IVIM-DKI model of diffusion instead of an IVIM model had a systematic impact on the resulting IVIM parameters: The pure diffusion coefficient and the pseudodiffusion coefficient were significantly increased (P < 0.03 in all assessed organs), accompanied by a decrease in the perfusion fraction in liver, pancreas, renal cortex, and skeletal muscle (all P < 0.02). Optimal b-value thresholds separating diffusion from perfusion effects had a tendency to lower values when the IVIM-DKI model was used.

CONCLUSIONS

The proposed algorithm provides a new approach for separation of IVIM and kurtosis effects of diffusion data without organ-specific adaptation.

Intravoxel incoherent motion diffusion-weighted imaging for characterizing focal hepatic lesions: Correlation with lesion enhancement

PURPOSE

To evaluate the value of intravoxel incoherent motion (IVIM) parameters for characterizing focal hepatic lesions, and to assess the correlation between IVIM parameters and arterial nodule enhancement.

MATERIALS AND METHODS

We retrospectively evaluated 161 lesions (91 hepatocellular carcinomas [HCCs], 27 intrahepatic cholangiocarcinomas [IHCCs], 20 hemangiomas, 9 combined hepatocellular-cholangiocarcinomas, 9 metastases, and 5 other tumors) in 161 patients (105 men and 56 women; mean age, 56.4 years). Diffusion-weighted imaging was performed using nine b-values (0-900 s/mm² ) at 1.5T. Apparent diffusion coefficient (ADC), molecular diffusion coefficient (D_slow ), perfusion fraction (f), and perfusion-related diffusion coefficient (D_fast ) were compared among the hepatic lesions using analysis of variance (ANOVA). Receiver-operating-characteristic analysis was performed to assess diagnostic performance. The enhancement fraction (EF) and the relative enhancement (RE) of the hepatic lesions on arterial phase gadoxetic acid-enhanced images were correlated with the IVIM parameters using Spearman's test.

RESULTS

For the differentiation of hemangiomas from malignant tumors, D_slow showed the largest area under the curve (0.933) among all parameters. Although ADC did not show any difference among malignant lesions (P ≥ 0.28), HCCs showed a significantly lower D_slow than IHCC (P < 0.001) and a higher f than did IHCC (P < 0.001) and metastasis (P = 0.027); f had a significant positive correlation with EF (r = 0.420, P < 0.001) and RE (r = 0.264, P = 0.001).

CONCLUSION

IVIM parameters are more helpful in characterizing malignant hepatic lesions than ADC; f may reflect the extent and degree of hepatic nodule enhancement in the arterial phase, and may allow for differentiation of HCC from IHCC and metastasis.

LEVEL OF EVIDENCE

3 J. MAGN. RESON. IMAGING 2017;45:1589-1598.

Simultaneous multi-slice echo planar diffusion weighted imaging of the liver and the pancreas: Optimization of signal-to-noise ratio and acquisition time and application to intravoxel incoherent motion analysis

PURPOSE

To optimize and test a diffusion-weighted imaging (DWI) echo-planar imaging (EPI) sequence with simultaneous multi-slice (SMS) excitation in the liver and pancreas regarding acquisition time (TA), number of slices, signal-to-noise ratio (SNR), image quality (IQ), apparent diffusion coefficient (ADC) quantitation accuracy, and feasibility of intravoxel incoherent motion (IVIM) analysis.

MATERIALS AND METHODS

Ten healthy volunteers underwent DWI of the upper abdomen at 3T. A SMS DWI sequence with CAIPIRINHA unaliasing technique (acceleration factors 2/3, denoted AF2/3) was compared to standard DWI-EPI (AF1). Four schemes were evaluated: (i) reducing TA, (ii) keeping TA identical with increasing number of averages, (iii) increasing number of slices with identical TA (iv) increasing number of b-values for IVIM. Acquisition schemes i-iii were evaluated qualitatively (reader score) and quantitatively (ADC values, SNR).

RESULTS

In scheme (i) no differences in SNR were observed (p=0.321-0.038) with reduced TA (AF2 increase in SNR/time 75.6%, AF3 increase SNR/time 102.4%). No SNR improvement was obtained in scheme (ii). Increased SNR/time could be invested in acquisition of more and thinner slices or higher number of b-values. Image quality scores were stable for AF2 but decreased for AF3. Only for AF3, liver ADC values were systematically lower.

CONCLUSION

SMS-DWI of the liver and pancreas provides substantially higher SNR/time, which either may be used for shorter scan time, higher slice resolution or IVIM measurements.

Diffusion-Related MRI Parameters for Assessing Early Treatment Response of Liver Metastases to Cytotoxic Therapy in Colorectal Cancer

OBJECTIVE

The objective of our study was to evaluate early therapeutic response after cytotoxic chemotherapy in patients with liver metastasis from colorectal cancer (CRC) using intravoxel incoherent motion (IVIM) DWI and dynamic contrast-enhanced MRI (DCE-MRI).

SUBJECTS AND METHODS

Nineteen patients with liver metastasis from CRC underwent DCE-MRI and IVIM DWI at baseline and after the first cycle of chemotherapy. IVIM DWI parameters including the apparent diffusion coefficient (ADC), true diffusion coefficient (D), pseudodiffusion coefficient (D*), and perfusion fraction (f) and DCE-MRI perfusion parameters including the volume transfer constant (K(trans)), reverse volume transfer constant (Kep), extravascular extracellular volume fraction (Ve), and initial area under the concentration curve in 60 seconds (iAUC) were calculated. The response evaluation was based on Response Evaluation Criteria in Solid Tumors version 1.1.

RESULTS

There were eight responding and 11 nonresponding patients. ADC (baseline value vs value after first cycle of chemotherapy [mean ± SD]: 1191.9 ± 232.2 vs 1263.5 ± 266.4 × 10(-3) mm(2)/s; p = 0.012), D (1085.9 ± 232.9 vs 1173.5 ± 248.9 × 10(-3) mm(2)/s; p = 0.012), and f (173.7% ± 39.8% vs 133.5% ± 28.3%; p = 0.017) showed a significant change after the first cycle of chemotherapy in the response group, whereas ADC and D showed no significant change in the nonresponse group. In addition, DCE-MRI perfusion parameters showed no significant changes. A correlation was found between each of perfusion-related IVIM parameters and the DCE-MRI parameters before chemotherapy (r = 1.33, p > 0.05).

CONCLUSION

Diffusion-related MRI parameters are useful for the early prediction of therapeutic response after cytotoxic chemotherapy for liver metastasis from CRC.

Use of intravoxel incoherent motion diffusion-weighted MR imaging for assessment of treatment response to invasive fungal infection in the lung

OBJECTIVES

The purpose of this study was to determine whether intravoxel incoherent motion (IVIM) -derived parameters and apparent diffusion coefficient (ADC) could act as imaging biomarkers for predicting antifungal treatment response.

METHODS

Forty-six consecutive patients (mean age, 33.9 ± 13.0 y) with newly diagnosed invasive fungal infection (IFI) in the lung according to EORTC/MSG criteria were prospectively enrolled. All patients underwent diffusion-weighted magnetic resonance (MR) imaging at 3.0 T using 11 b values (0-1000 sec/mm²). ADC, pseudodiffusion coffiecient D*, perfusion fraction f, and the diffusion coefficient D were compared between patients with favourable (n=32) and unfavourable response (n=14).

RESULTS

f values were significantly lower in the unfavourable response group (12.6%±4.4%) than in the favourable response group (30.2%±8.6%) (Z=4.989, P<0.001). However, the ADC, D, and D* were not significantly different between the two groups (P>0.05). Receiver operating characteristic curve analyses showed f to be a significant predictor for differentiation, with a sensitivity of 93.8% and a specificity of 92.9%.

CONCLUSIONS

IVIM-MRI is potentially useful in the prediction of antifungal treatment response to patients with IFI in the lung. Our results indicate that a low perfusion fraction f may be a noninvasive imaging biomarker for unfavourable response.

KEY POINTS

• Recognition of IFI indicating clinical outcome is important for treatment decision-making. • IVIM can reflect diffusion and perfusion information of IFI lesions separately. • Perfusion characteristics of IFI lesions could help differentiate treatment response. • An initial low f may predict unfavourable response in IFI.

Diffusion-weighted MR imaging of pancreatic cancer: A comparison of mono-exponential, bi-exponential and non-Gaussian kurtosis models

OBJECTIVES

To compare two Gaussian diffusion-weighted MRI (DWI) models including mono-exponential and bi-exponential, with the non-Gaussian kurtosis model in patients with pancreatic ductal adenocarcinoma.

MATERIALS AND METHODS

After written informed consent, 15 consecutive patients with pancreatic ductal adenocarcinoma underwent free-breathing DWI (1.5T, b-values: 0, 50, 150, 200, 300, 600 and 1000 s/mm²). Mean values of DWI-derived metrics ADC, D, D*, f, K and D_K were calculated from multiple regions of interest in all tumours and non-tumorous parenchyma and compared. Area under the curve was determined for all metrics.

RESULTS

Mean ADC and D_K showed significant differences between tumours and non-tumorous parenchyma (both P < 0.001). Area under the curve for ADC, D, D*, f, K, and D_K were 0.77, 0.52, 0.53, 0.62, 0.42, and 0.84, respectively.

CONCLUSION

ADC and D_K could differentiate tumours from non-tumorous parenchyma with the latter showing a higher diagnostic accuracy. Correction for kurtosis effects has the potential to increase the diagnostic accuracy of DWI in patients with pancreatic ductal adenocarcinoma.

Assessment of renal dysfunction with diffusion-weighted imaging: comparing intra-voxel incoherent motion (IVIM) with a mono-exponential model

BACKGROUND

Because renal dysfunction is a worldwide problem, accurate assessment is required for planning treatment and follow-up. Intra-voxel incoherent motion (IVIM) can isolate fast from slow water motion in well-perfused organs and may be helpful in assessing renal dysfunction.

PURPOSE

To determine the clinical value of IVIM in the assessment of renal dysfunction compared with a mono-exponential model.

MATERIAL AND METHODS

Fifty-four consecutive participants (mean age, 53.13 ± 13.96 years) were recruited into this study. The estimated glomerular filtration rate (eGFR) was calculated to classify the participants as having severe renal injury (sRI, eGFR ≤ 30 mL/min/1.73 m(2)) or not (non-sRI). DWI with seven b-factors was performed. Image analysis was performed by a radiologist to generate an apparent diffusion coefficient map (ADCmon) by mono-exponential model, diffusion coefficient (Dslow and Dfast), and fraction of fast diffusion (Ffast) maps by IVIM. The circular regions of interest were placed at the interface between the cortex and medulla for parameter measurements.

RESULTS

The ADCmon, Dslow, Dfast, and Ffast were less in sRI than non-sRI (P < 0.05). ADCmon and Dslow were positively related with eGFR (P < 0.05). For differentiating sRI from non-sRI, receiver operating characteristic curve indicated no significant difference between the two methods (P > 0.05). Furthermore, the correlation was 0.93 between ADCmon and Dslow, followed by 0.57 between Dfast and Ffast, 0.48 between ADCmon and Dfast, and 0.34 between ADCmon and Ffast (P < 0.05).

CONCLUSION

The IVIM model contributed little to improving the assessment of renal dysfunction compared with a mono-exponential model.

Evaluation of Hepatic Tumors Using Intravoxel Incoherent Motion Diffusion-Weighted MRI

Background

This study aimed to evaluate the diagnostic value of the D value, D* value, and f magnitude for identifying benign and malignant hepatic tumors using intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI).

Material/Methods

Data of 89 cases (123 lesions) with hepatic tumor confirmed by surgical pathology and postoperative follow-up were retrospectively collected. Among these cases, 40 cases were benign hepatic tumors (57 lesions) and 49 cases were malignant hepatic tumors (66 lesions). All subjects underwent conventional MRI with T₁WI, T₂WI, multi-b-value DWI, and dynamic enhanced LAVA scan. Diffusion-weighted images with 11 b values (0, 10, 20, 30, 50, 80, 100, 200, 400, 800, and 1000 s/mm²) were obtained to calculate true molecular diffusion (D), perfusion-related diffusion coefficient (D*), and perfusion fraction (f). The diagnostic performance in differentiating between malignant and benign hepatic lesions was analyzed.

Results

Malignant lesions had a significantly lower D value ([1.04±0.34]×10⁻³ mm²/s) and D* value ([16.5±7.7]×10⁻³ mm²/s) compared to benign lesions (D value: [1.70±0.55]×10⁻³ mm²/s, P<0.01; D* value: [21.7±9.9]×10⁻³ mm²/s, P<0.01). There was no statistically significant difference in f values between malignant (23.3±9.5) and benign lesions (33.5±14.9, P=0.13). In addition, D exhibited a better diagnostic performance than D* in terms of the area under the curve, sensitivity, and specificity when identifying malignancies from benign lesions.

Conclusions

D and D* are significant parameters for diagnosing hepatic tumors. Moreover, the D value is a more reliable parameter in distinguishing benign and malignant hepatic tumors.

Multiparametric MR Imaging in Abdominal Malignancies

Modern MR imaging protocols can yield both anatomic and functional information for the assessment of hepatobiliary and pancreatic malignancies. Diffusion-weighted imaging is fully integrated into state-of-the-art protocols for tumor detection, characterization, and therapy monitoring. Hepatobiliary contrast agents have gained ground in the evaluation of focal liver lesions during the last years. Perfusion MR imaging is expected to have a central role for monitoring therapy in body tumors treated with antivascular drugs. Approaches such as Magnetic resonance (MR) elastography and (1)H-MR spectroscopy are still confined to research centers, but with the potential to grow in a short time frame.

Intravoxel incoherent motion diffusion-weighted imaging in differentiating uterine fibroid from focal adenomyosis: initial results

To evaluate the performance of intravoxel incoherent motion (IVIM)-diffusion-weighted imaging (DWI) in differentiating uterine fibroids from focal adenomyosises. Twenty-five uterine fibroids and 21 focal adenomyosises prospectively underwent IVIM-DWI examination prior to surgery. Four parameters including apparent diffusion coefficient total values (ADCtot), true diffusion coefficient (D), pseudodiffusion coefficient (D*) and perfusion fraction (f) derived from IVIM-DWI images were separately calculated and compared across four groups. There was a statistically significant difference in IVIM-derived f parameter between fibroid and focal adenomyosis (p = 0.01) and control group (p = 0.02). Uterine fibroids gave higher coefficient of variation (CV) of all IVIM-derived parameters than focal adenomyosises. IVIM-DWI could improve the sensitivity and specificity of detecting focal adenomyosis to 100 and 92.6 %, respectively. IVIM-f parameter could be potentially used to better distinguish uterine fibroid from focal adenomyosis. The higher CV of IVIM-derived parameters with acceptable range is often observed in the diseased group.

Hepatocellular carcinoma: IVIM diffusion quantification for prediction of tumor necrosis compared to enhancement ratios

Purpose

To correlate intra voxel incoherent motion (IVIM) diffusion parameters of liver parenchyma and hepatocellular carcinoma (HCC) with degree of liver/tumor enhancement and necrosis; and to assess the diagnostic performance of diffusion parameters vs. enhancement ratios (ER) for prediction of complete tumor necrosis.

Patients and methods

In this IRB approved HIPAA compliant study, we included 46 patients with HCC who underwent IVIM diffusion-weighted (DW) MRI in addition to routine sequences at 3.0 T. True diffusion coefficient (D), pseudo-diffusion coefficient (D*), perfusion fraction (PF) and apparent diffusion coefficient (ADC) were quantified in tumors and liver parenchyma. Tumor ER were calculated using contrast-enhanced imaging, and degree of tumor necrosis was assessed using post-contrast image subtraction. IVIM parameters and ER were compared between HCC and background liver and between necrotic and viable tumor components. ROC analysis for prediction of complete tumor necrosis was performed.

Results

79 HCCs were assessed (mean size 2.5 cm). D, PF and ADC were significantly higher in HCC vs. liver (p < 0.0001). There were weak significant negative/positive correlations between D/PF and ER, and significant correlations between D/PF/ADC and tumor necrosis (for D, r 0.452, p < 0.001). Among diffusion parameters, D had the highest area under the curve (AUC 0.811) for predicting complete tumor necrosis. ER outperformed diffusion parameters for prediction of complete tumor necrosis (AUC > 0.95, p < 0.002).

Conclusion

D has a reasonable diagnostic performance for predicting complete tumor necrosis, however lower than that of contrast-enhanced imaging.

A comparative study of apparent diffusion coefficient and intravoxel incoherent motion-derived parameters for the characterization of common solid hepatic tumors

BACKGROUND

The performance of diffusion-weighted imaging parameters for characterizing hepatic tumors is controversial.

PURPOSE

To compare the performances of apparent diffusion coefficient (ADC) and intravoxel incoherent motion (IVIM)-derived parameters, including the pure diffusion coefficient (D), perfusion coefficient (D*), and perfusion fraction (f), in the characterization of common solid hepatic tumors.

MATERIAL AND METHODS

Twelve healthy volunteers and 43 patients underwent free-breath diffusion-weighted magnetic resonance imaging (DW-MRI) of the liver using eight b values (10-800 s/mm(2)). Twelve regions of interest (ROIs) of normal liver tissue in healthy volunteers and 49 hepatic lesions (23 hepatocellular carcinomas [HCCs], 16 hemangiomas, and 10 metastases) were measured. Conventional ADC(0,500) and ADCtotal obtained by the mono-exponential model, as well as D, D*, and f were calculated. Student t-tests and receiver operating characteristic (ROC) analysis were also performed.

RESULTS

ADC(0,500), ADCtotal, and D were significantly lower in the malignant group ([1.48 ± 0.35] × 10(-3) mm(2)/s; [1.35 ± 0.30] × 10(-3) mm(2)/s; [1.18 ± 0.33] × 10(-3) mm(2)/s) compared to the hemangioma group ([2.74 ± 1.03] × 10(-3) mm(2)/s; [2.61 ± 0.81] × 10(-3) mm(2)/s; [1.97 ± 0.79] × 10(-3) mm(2)/s]. D* did not differ among multiple comparisons. For the area under the ROC curve (AUC-ROC), the maximum value was attained with ADCtotal (0.983) and was closely followed by ADC(0,500) (0.967), with lower values obtained for D (0.837), f (0.649), and D* (0.599). Statistically significant differences were found between the AUC-ROC of both ADCs (ADCtotal and ADC(0,500)) and D. There was no statistically significant difference between the AUC-ROC of ADCtotal and ADC(0,500).

CONCLUSION

ADCs showed superior diagnostic performance compared to IVIM-derived parameters in detecting differences between the malignant group and hemangioma group.

Whole-body diffusion kurtosis imaging: initial experience on non-Gaussian diffusion in various organs

INTRODUCTION

Diffusion kurtosis imaging (DKI) is based on a non-Gaussian diffusion model that should inherently better account for restricted water diffusion within the complex microstructure of most tissues than the conventional diffusion-weighted imaging (DWI), which presumes Gaussian distributed water molecule displacement probability. The aim of this investigation was to test the technical feasibility of in vivo whole-body DKI, probe for organ-specific differences, and compare whole-body DKI and DWI results.

MATERIALS AND METHODS

Eight healthy subjects underwent whole-body DWI on a clinical 3.0 T magnetic resonance imaging system. Echo-planar images in the axial orientation were acquired at b-values of 0, 150, 300, 500, and 800 mm²/s. Parametrical whole-body maps of the diffusion coefficient (D), the kurtosis (K), and the traditional apparent diffusion coefficient (ADC) were generated. Goodness of fit was compared between DKI and DWI fits using the sums of squared residuals. Data groups were tested for significant differences of the mean by paired Student t tests.

RESULTS

Good-quality parametrical whole-body maps of D, K, and ADC could be computed. Compared with ADC values, D values were significantly higher in the cerebral gray matter (by 30%) and white matter (27%), renal cortex (23%) and medulla (21%), spleen (101%), as well as erector spinae muscle (34%) (each P value <0.001). No significant differences between D and ADC were found in the cerebrospinal fluid (P = 0.08) and in the liver (P = 0.13). Curves of DKI fitted the measurement points significantly better than DWI curves did in most organs.

CONCLUSIONS

Whole-body DKI is technically feasible and may reflect tissue microstructure more meaningfully than whole-body DWI.

Comparison of magnetic resonance elastography and diffusion-weighted imaging for differentiating benign and malignant liver lesions

OBJECTIVES

Comparison of magnetic resonance elastography (MRE) and diffusion-weighted imaging (DWI) for differentiating malignant and benign focal liver lesions (FLLs).

METHODS

Seventy-nine subjects with 124 FLLs (44 benign and 80 malignant) underwent both MRE and DWI. MRE was performed with a modified gradient-echo sequence and DWI with a free breathing technique (b = 0.500). Apparent diffusion coefficient (ADC) maps and stiffness maps were generated. FLL mean stiffness and ADC values were obtained by placing regions of interest over the FLLs on stiffness and ADC maps. The accuracy of MRE and DWI for differentiation of benign and malignant FLL was compared using receiver operating curve (ROC) analysis.

RESULTS

There was a significant negative correlation between stiffness and ADC (r = -0.54, p < 0.0001) of FLLs. Malignant FLLs had significantly higher mean stiffness (7.9kPa vs. 3.1kPa, p < 0.001) and lower mean ADC (129 vs. 200 × 10(-3)mm(2)/s, p < 0.001) than benign FLLs. The sensitivity/specificity/positive predictive value/negative predictive value for differentiating malignant from benign FLLs with MRE (cut-off, >4.54kPa) and DWI (cut-off, <151 × 10(-3)mm(2)/s) were 96.3/95.5/97.5/93.3% (p < 0.001) and 85/81.8/88.3/75% (p < 0.001), respectively. ROC analysis showed significantly higher accuracy for MRE than DWI (0.986 vs. 0.82, p = 0.0016).

CONCLUSION

MRE is significantly more accurate than DWI for differentiating benign and malignant FLLs.

KEY POINTS

• MRE is superior to DWI for differentiating benign and malignant focal liver lesions. • Benign lesions with large fibrous components may have higher stiffness with MRE. • Cholangiocarcinomas tend to have higher stiffness than hepatocellular carcinomas. • Hepatocellular adenomas tend to have lower stiffness than focal nodular hyperplasia. • MRE is superior to conventional MRI in differentiating benign and malignant liver lesions.

New imaging techniques for liver diseases

Newly developed or advanced methods of ultrasonography and MR imaging provide combined anatomical and quantitative functional information about diffuse and focal liver diseases. Ultrasound elastography has a central role for staging liver fibrosis and an increasing role in grading portal hypertension; dynamic contrast-enhanced ultrasonography may improve tumor characterization. In clinical practice, MR imaging examinations currently include diffusion-weighted and dynamic MR imaging, enhanced with extracellular or hepatobiliary contrast agents. Moreover, quantitative parameters obtained with diffusion-weighted MR imaging, dynamic contrast-enhanced MR imaging and MR elastography have the potential to characterize further diffuse and focal liver diseases, by adding information about tissue cellularity, perfusion, hepatocyte transport function and visco-elasticity. The multiparametric capability of ultrasonography and more markedly of MR imaging gives the opportunity for high diagnostic performance by combining imaging biomarkers. However, image acquisition and post-processing methods should be further standardized and validated in multicenter trials.

Value of diffusion-weighted MR imaging using various parameters for assessment and characterization of solitary pulmonary nodules

OBJECTIVES

To determine the appropriate parameters and evaluation method for characterizing solitary pulmonary nodules (SPNs) using quantitative parameters of diffusion-weighted imaging (DWI).

METHODS

Thirty-two subjects with 36 SPNs underwent DWI with seven different b values (0, 50, 100, 150, 300, 500, and 1000s/mm(2)). Five quantitative parameters were obtained from the region of interest drawn over each SPN: apparent diffusion coefficients (ADCs), true diffusion coefficients (DCs), and perfusion fractions (PFs), and signal-intensity ratios between lesion and spinal cord from DWI (b values: 1000 [LSR1000] and 500 [LSR500)]). All quantitative parameters and the diagnostic capabilities were statistically compared.

RESULTS

SPNs were diagnosed as follow: malignant (n=27) and benign (n=9). Parameter comparisons for malignant and benign showed both LSRs differed significantly (p<0.05). Applying feasible threshold values showed LSR500 specificity (88.9% [8/9]) and accuracy (77.8% [28/36]) were significantly higher than ADC, DC, and PF specificity and accuracy (p<0.05). LSR1000 accuracy (72.2% [26/36]) was significantly higher than DC accuracy, and its specificity (88.9% [8/9]) was significantly higher than ADC, DC, and PF specificities (p<0.05).

CONCLUSIONS

For quantitative differentiation of SPNs, LSR evaluation was more useful and practical than ADC, DC, and PF, and choice of b values showed little impact for the differentiation.

Intratumoral heterogeneity of breast cancer xenograft models: texture analysis of diffusion-weighted MR imaging

Objective

To investigate whether there is a relationship between texture analysis parameters of apparent diffusion coefficient (ADC) maps and histopathologic features of MCF-7 and MDA-MB-231 xenograft models.

Materials and Methods

MCF-7 estradiol (+), MCF-7 estradiol (-), and MDA-MB-231 xenograft models were made with approval of the animal care committee. Twelve tumors of MCF-7 estradiol (+), 9 tumors of MCF-7 estradiol (-), and 6 tumors in MDA-MB-231 were included. Diffusion-weighted MR images were obtained on a 9.4-T system. An analysis of the first and second order texture analysis of ADC maps was performed. The texture analysis parameters and histopathologic features were compared among these groups by the analysis of variance test. Correlations between texture parameters and histopathologic features were analyzed. We also evaluated the intraobserver agreement in assessing the texture parameters.

Results

MCF-7 estradiol (+) showed a higher standard deviation, maximum, skewness, and kurtosis of ADC values than MCF-7 estradiol (-) and MDA-MB-231 (p < 0.01 for all). The contrast of the MCF-7 groups was higher than that of the MDA-MB-231 (p = 0.004). The correlation (COR) of the texture analysis of MCF-7 groups was lower than that of MDA-MB-231 (p < 0.001). The histopathologic analysis showed that Ki-67_mean and Ki-67_diff of MCF-7 estradiol (+) were higher than that of MCF-7 estradiol (-) or MDA-MB-231 (p < 0.05). The microvessel density (MVD)_mean and MVD_diff of MDA-MB-231 were higher than those of MCF-7 groups (p < 0.001). A diffuse-multifocal necrosis was more frequently found in MDA-MB-231 (p < 0.001). The proportion of necrosis moderately correlated with the contrast (r = -0.438, p = 0.022) and strongly with COR (r = 0.540, p = 0.004). Standard deviation (r = 0.622, r = 0.437), skewness (r = 0.404, r = 0.484), and kurtosis (r = 0.408, r = 0.452) correlated with Ki-67_mean and Ki-67_diff (p < 0.05 for all). COR moderately correlated with Ki-67_diff (r = -0.388, p = 0.045). Skewness (r = -0.643, r = -0.464), kurtosis (r = -0.581, r = -0.389), contrast (r = -0.473, r = -0.549) and COR (r = 0.588, r = 0.580) correlated with MVD_mean and MVD_diff (p < 0.05 for all).

Conclusion

The texture analysis of ADC maps may help to determine the intratumoral spatial heterogeneity of necrosis patterns, amount of cellular proliferation and the vascularity in MCF-7 and MDA-MB-231 xenograft breast cancer models.