Value of diffusion-weighted magnetic resonance images for discrimination of focal benign and malignant hepatic lesions: a meta-analysis

Diagnostic accuracy of apparent diffusion coefficient (ADC) value in differentiating malignant from benign solid liver lesions: a systematic review and meta-analysis

OBJECTIVES

We undertook a systematic review and meta-analysis of the diagnostic performance of mean apparent diffusion coefficient (ADC) values derived by diffusion-weighted (DW)-MRI in the characterization of solid benign and malignant liver lesions, and to assess their value in discriminating these lesions in daily routine practice.

METHODS

A systematic review of PubMed, Embase, Scopus, and Web of Science was conducted to retrieve studies that used ADC values for differentiating solid benign/dysplastic nodules and malignant liver lesions. A bivariate random-effects model with pooled sensitivity and specificity values with 95% CI (confidence interval) was used. This meta-analysis was performed on the per-lesion basis. Summary receiver operating characteristic (SROC) plot and area under curve (AUC) were created.

RESULTS

A total of 14 original articles were retrieved. The combined (95% CI) sensitivity and specificity of mean ADC values for differentiating solid benign from malignant lesions were 78% (67-86%) and 74% (64-81%), respectively. The pooled (95% CI) positive and negative LRs were respectively 3 (2.3-3.8) and 0.3 (0.21-0.43). The DOR (95% CI) was 10 (7-15). The AUC (95% CI) of the SROC plot was 82% (78-85%). Reporting bias was negligible (p value of regression test = 0.36). Mean size of malignant lesions and breathing pattern of MRI were found to be sources of heterogeneity of pooled sensitivity.

CONCLUSION

ADC measurement independently may not be an optimal diagnostic imaging method for differentiating solid malignant from solid benign hepatic lesions. The meta-analysis showed that ADC measurement had moderate diagnostic accuracy for characterizing solid liver lesions. Further prospective and comparative studies with pre-specified ADC thresholds could be performed to investigate the best MRI protocol and ADC threshold for characterizing solid liver lesions.

ADVANCES IN KNOWLEDGE

ADC measurement by DW-MRI does not have a good diagnostic performance to differentiate solid malignant from solid benign lesions. Therefore, we suggest not using ADC values in clinical practice to evaluate solid liver lesions.

The diagnostic value of diffusion-weighted imaging in differentiating benign from malignant hepatic lesions

Background

Diffusion-weighted imaging (DWI) is a novel imaging technique with growing application in onco-imaging. This modality evaluates the diffusion of water molecules in various tissues, which is restricted in hyper cellular regions such as malignant tissue. Apparent diffusion co-efficient (ADC) is a method which can quantify the degree of restriction in tissues and can have diagnostic roles in characterization of hepatic lesions. In this study, 93 patients with proven hepatic lesions were included. These patients had undergone initial evaluation via ultrasonography and dynamic CT scan, and had a definite diagnosis confirmed by biopsy. These patients underwent DW imaging and ADC values of their lesions were calculated. Patients were divided into two groups, benign and malignant groups, based on their biopsy results; and ADC values of hepatic lesions were compared in the two groups.

Results

The two groups were gender matched. There was a significant difference in the age distribution between the two groups. Mean ADC values for benign and malignant hepatic lesions were 1.58 ± 0.35 (10-3 mm2/s) and 0.87 ± 0.16 (10-3 mm2/s), respectively. There was a statistically significant differences between benign and malignant hepatic lesions (p value < 10-3). DW imaging had a sensitivity of 97.6% and specificity of 98.7% in detecting malignant hepatic lesions from benign ones (p = 0.0001, AUC = 0.99).

Conclusion

DW MRI imaging can differentiate malignant and benign liver lesions with high sensitivity and specificity using ADC values generated; furthermore, each subgroup of hepatic lesions could be determined based on ADC values.

Diagnostic Performance of Diffusion Tensor Imaging for Characterizing Breast Tumors: A Comprehensive Meta-Analysis

Rationale and Objectives: Controversy still exists on the diagnosability of diffusion tensor imaging (DTI) for breast lesions characterization across published studies. The clinical guideline of DTI used in the breast has not been established. This meta-analysis aims to pool relevant evidences and evaluate the diagnostic performance of DTI in the differential diagnosis of malignant and benign breast lesions.

Materials and Methods: The studies that assessed the diagnostic performance of DTI parameters in the breast were searched in Embase, PubMed, and Cochrane Library between January 2010 and September 2019. Standardized mean differences and 95% confidence intervals of fractional anisotropy (FA), mean diffusivity (MD), and three diffusion eigenvalues (λ1, λ2, and λ3) were calculated using Review Manager 5.2. The pooled sensitivity, specificity, and area under the curve (AUC) were calculated with a bivariate model. Publication bias and heterogeneity between studies were also assessed using Stata 12.0.

Results: Sixteen eligible studies incorporating 1,636 patients were included. The standardized mean differences indicated that breast cancers had a significantly higher FA but lower MD, λ1, λ2, and λ3 than those of benign lesions (all P < 0.05). Subgroup analysis indicated that invasive breast carcinoma (IBC) had a significantly lower MD value than that of ductal carcinoma in situ (DCIS) (P = 0.02). λ1 showed the best diagnostic accuracy with pooled sensitivity, specificity, and AUC of 93%, 92%, and 0.97, followed by MD (AUC = 0.92, sensitivity = 87%, specificity = 83%) and FA (AUC = 0.76, sensitivity = 70%, specificity = 70%) in the differential diagnosis of breast lesions.

Conclusion: DTI with multiple quantitative parameters was adequate to differentiate breast cancers from benign lesions based on their biological characteristics. MD can further distinguish IBC from DCIS. The parameters, especially λ1 and MD, should attract our attention in clinical practice.

Evaluation of ADCratio on liver MRI diffusion to discriminate benign versus malignant solid liver lesions

PURPOSE

The aim of this project is to investigate the usefulness of the absolute liver lesion ADC value and ratio of Apparent diffusion coefficient (ADC) values of a liver lesion and liver parenchyma to discriminate between a benign and malignant lesion.

METHODS

Liver MRI scans performed between January 2009 and June 2015 were retrospectively analysed. Scans were performed on either a 1.5 T or 3 T MRI unit. The type of liver lesion (benign or malignant) was determined by its radiological appearance, histology result and clinical management. Lesions with undetermined diagnosis or MRI studies degraded by artifacts were excluded. Liver cysts were also excluded from the analysis. ADC value of a lesion and liver parenchyma was measured and ADC_ratio was calculated. The values were analysed using independent samples t-test Results:Data set contained 39 benign lesions and 36 malignant lesions. Mean ADC value for benign lesions was 1678, and the mean value for malignant lesions was 1097 with a statistically significant difference of p < 0.001. All lesions with ADC value below 955 were malignant, while all lesions with ADC value above 1880 were benign. ADC value of 1260 was identified as the best available cut-off value for differentiating benign and malignant lesions, achieving sensitivity of 92%, specificity of 80% and an overall accuracy of 89%. The mean lesion to liver ADC_ratio for benign lesions was 1.3467 and for malignant lesions was 0.9038 with a statistically significant difference of p < 0.001. All lesions with ADC_ratio measuring <0.9 were malignant while lesions with ADC_ratio>1.5 were benign. ADC_ratio of 1.1 was identified statistically as the best available cut-off value for differentiating benign from malignant lesions, with sensitivity of 82%, specificity of 86% and an overall accuracy of 92%.

CONCLUSION

Our dataset indicates that lesion to background liver ADC_ratio is superior in discriminating between benign and malignant focal lesions compared to absolute ADC values of the hepatic lesions.

[Importance of diffusion imaging in liver metastases]

CLINICAL/METHODICAL ISSUE

Detection and characterization of focal liver lesions.

STANDARD RADIOLOGICAL METHODS

Due to its excellent soft tissue contrast, the availability of liver-specific contrast agents and the possibility of functional imaging, magnetic resonance imaging (MRI) is the method of choice for the evaluation of focal liver lesions.

METHODICAL INNOVATIONS

Diffusion-weighted imaging (DWI) enables generation of functional information about the microstructure of a tissue besides morphological information.

PERFORMANCE

In the detection of focal liver lesions DWI shows a better detection rate compared to T2w sequences and a slightly poorer detection rate compared to dynamic T1w sequences. In principle, using DWI it is possible to distinguish malignant from benign liver lesions and also to detect a therapy response at an early stage.

ACHIEVEMENTS

For both detection and characterization of focal liver lesions, DWI represents a promising alternative to the morphological sequences; however, a more detailed characterization with the use of further sequences should be carried out particularly for the characterization of solid benign lesions. For the assessment and prognosis of therapy response, DWI offers advantages compared to morphological sequences.

PRACTICAL RECOMMENDATIONS

For the detection of focal liver lesions DWI is in principle sufficient. After visual detection of a solid liver lesion a more detailed characterization should be carried out using further sequences (in particular dynamic T1w sequences). The DWI procedure should be used for the assessment and prognosis of a therapy response.

Diffusion Quantification in Body Imaging

Diffusion-weighted imaging (DWI) is increasingly incorporated into routine body magnetic resonance imaging protocols. DWI can assist with lesion detection and even in characterization. Quantitative DWI has exhibited promise in the discrimination between benign and malignant pathology, in the evaluation of the biologic aggressiveness, and in the assessment of the response to treatment. Unfortunately, inconsistencies in DWI acquisition parameters and analysis have hampered widespread clinical utilization. Focusing primarily on liver applications, this article will review the basic principles of quantitative DWI. In addition to standard mono-exponential fitting, the authors will discuss intravoxel incoherent motion and diffusion kurtosis imaging that involve more sophisticated approaches to diffusion quantification.

Focal Liver Lesions Classification and Characterization: What Value Do DWI and ADC Have?

OBJECTIVE

The aim of this work was to analyze the value of diffusion-weighted imaging (DWI) in the classification/characterization of focal liver lesions (FLLs).

METHODS

Retrospective study, approved by ethical board, of 100 proven FLLs (20 hemangiomas, 20 focal nodular hyperplasia, 20 dysplastic nodules, 20 hepatocellular carcinomas, and 20 metastases) was performed by 1.5-T MR. For each lesion, 2 readers, blinded of medical history, have evaluated 6 sets of images: set A (T1/T2-weighted images), set B (set A + DWI), set C (set B + apparent diffusion coefficient [ADC] map), set D (set A + dynamic and hepatobiliary phases), set E (set D + DWI), set F (set E + ADC map).

RESULTS

In unenhanced images, the evaluation of the ADC improves the accuracy in classification/characterization (+9%/14%, respectively), whereas in enhanced images the accuracy was increased by DWI (+7%/12%, respectively) and ADC (+13%/19%, respectively). Diffusion-weighted imaging does not improve classification/characterization of hemangiomas, may be useful in focal nodular hyperplasia/dysplastic nodules vs metastases/hepatocellular carcinoma differentiation, and increases the classification/characterization of metastases in both unenhanced and enhanced images.

CONCLUSIONS

Diffusion-weighted imaging may improve classification/characterization of FLLs at unenhanced/enhanced examinations.

Standard-b-Value Versus Low-b-Value Diffusion-Weighted Imaging in Hepatic Lesion Discrimination: A Meta-analysis

OBJECTIVE

We sought to determine the comparative diagnostic performance of standard-b-value (500-1000s/mm) versus low-b-value (≤500 s/mm) diffusion-weighted imaging (DWI) in the discrimination of hepatic lesions.

METHODS

A total of 1775 hepatic malignant lesions and 1120 benign hepatic lesions from 21 studies were included.

RESULTS

(1) The global sensitivity was 0.86 (95% confidence interval [CI], 0.847-0.879), the specificity was 0.82 (95% CI, 0.797-0.842), the positive likelihood ratio (PLR) was 6.234 (95% CI, 4.260-9.123), the negative likelihood ratio (NLR) was 0.175 (95% CI, 0.135-0.227), and diagnostic odds ratio (DOR) was 42.836 (95% CI, 24.134-76.031). The area under the curve (AUC) and Q* index were 0.93 and 0.87. Publication bias was not present (P > 0.05). (2)The sensitivity of a subgroup meta-analysis of standard-b-value DWI was 0.858 (95% CI, 0.835-0.880), the specificity was 0.836 (95% CI, 0.807-0.863), the PLR was 6.527 (95% CI, 3.857-11.046), the NLR was 0.168 (95% CI, 0.123-0.239), and the DOR was 49.716 (95% CI, 22.897-107.98). The AUC and Q* index were 0.941 and 0.88. (3)The sensitivity of a subgroup meta-analysis of low-b-value DWI was 0.87 (95% CI, 0.84-0.89), the specificity was 0.80 (95% CI, 0.76-0.83), the PLR was 6.22 (95% CI, 3.29-11.76), the NLR was 0.19 (95% CI, 0.12-0.29), and the DOR was 37.14 (95% CI, 14.80-93.18). The AUC and Q* index were 0.922 and 0.86.

CONCLUSIONS

Hepatic DWI is useful in differentiating between malignant and benign hepatic lesions. Standard-b-value DWI displayed an overall superior diagnostic accuracy over low-b-value DWI. Further trials needed to determine whether increasing b values beyond 1000 s/mm affects the diagnostic accuracy of hepatic lesion discrimination.

Hepatocellular Carcinoma and Diffusion-Weighted MRI: Detection and Evaluation of Treatment Response

Differentiating between cancerous tissue and healthy liver parenchyma could represent a challenge with the only conventional Magnetic Resonance (MR) imaging. Diffusion weighted imaging (DWI) exploits different tissue characteristics to conventional Magnetic Resonance Imaging (MRI) sequences that enhance hepatocellular carcinoma (HCC) detection, characterization, and post-treatment evaluation. Detection of HCC is improved by DWI, infact this technology increases conspicuity of lesions that might otherwise not be identified due to obscuration by adjacent vessels or due to low contrast between the lesion and background liver. It is important to remember that DWI combined with contrast-enhanced MRI has higher sensitivity than DWI alone, and that some patients are not eligible for use of contrast on CT and MRI; in these patients DWI has a prominent role. MRI has advanced beyond structural anatomic imaging to now showing pathophysiologic processes. DWI is a promising way to characterize lesions utilizing the inherent contrast within the liver and has the benefit of not requiring contrast injection. DWI improves detection and characterization of HCC. Proposed clinical uses for DWI include: assessing prognosis, predicting response, monitoring response to therapy, and distinguishing tumor recurrence from treatment effect. Ideally, DWI will help risk stratify patients and will participate in prognostic modeling.

Fifty Years of Technological Innovation: Potential and Limitations of Current Technologies in Abdominal Magnetic Resonance Imaging and Computed Tomography

Magnetic resonance imaging (MRI) has become an important modality for the diagnosis of intra-abdominal pathology. Hardware and pulse sequence developments have made it possible to derive not only morphologic but also functional information related to organ perfusion (dynamic contrast-enhanced MRI), oxygen saturation (blood oxygen level dependent), tissue cellularity (diffusion-weighted imaging), and tissue composition (spectroscopy). These techniques enable a more specific assessment of pathologic lesions and organ functionality. Magnetic resonance imaging has thus transitioned from a purely morphologic examination to a modality from which image-based disease biomarkers can be derived. This fits well with several emerging trends in radiology, such as the need to accurately assess response to costly treatment strategies and the need to improve lesion characterization to potentially avoid biopsy. Meanwhile, the cost-effectiveness, availability, and robustness of computed tomography (CT) ensure its place as the current workhorse for clinical imaging. Although the lower soft tissue contrast of CT relative to MRI is a long-standing limitation, other disadvantages such as ionizing radiation exposure have become a matter of public concern. Nevertheless, recent technical developments such as dual-energy CT or dynamic volume perfusion CT also provide more functional imaging beyond morphology.The aim of this article was to review and discuss the most important recent technical developments in abdominal MRI and state-of-the-art CT, with an eye toward the future, providing examples of their clinical utility for the evaluation of hepatic and renal pathologies.

Clinical applications of diffusion-weighted magnetic resonance imaging in diagnosis of renal lesions - a systematic review

Diffusion-weighted magnetic resonance imaging (DW-MRI) is an established technique to detect the changes of the diffusion of water in biological tissues and reflect the pathophysiological process on the molecular level. It is a promising non-invasive imaging modality in detection of microstructural and functional changes in pathologies of kidney. To systematically review the research advancement of the DW-MRI in diagnosis of renal lesions, a systematic literature search was performed up to 8 October 2014 using the MEDLINE/PubMed and Embase databases for articles reporting on DW-MRI in diagnosis of renal lesions. Only articles with full data about DW-MRI application with potential implication in solving usually encountered clinical challenges about renal lesions were finally examined. The clinical application of DW-MRI allows a better understanding of some pathologic conditions of the kidney including renal insufficiency, renal artery stenosis, ureteral obstruction, foetal kidney disease, hydronephrosis and pyonephrosis. In addition, DW-MRI can also provide clinicians with the information of function evaluation of renal allograft and curative effect assessment of renal tumour. In summary, performance of renal DW-MRI, presuming that measurements are high quality, will further boost this modality, particularly for early detection of diffusion renal conditions, as well as more accurate characterization of renal lesions.

Differential diagnosis of pancreatic cancer by single-shot echo-planar imaging diffusion-weighted imaging

AIM: To investigate the diagnostic ability of single-shot echo-planar imaging (EPI) diffusion-weighted imaging (DWI) to differentiate between malignant and benign pancreatic lesions.

METHODS: A computerized search was performed on PubMed, MEDLINE and EMBASE up to August 2014. Nine studies (10 sets of data) with a total of 304 malignant pancreatic lesions and 188 benign pancreatic lesions were included. The characteristics of each study included the study name, year of publication, magnetic resonance modalities used, patient population, strength of field, pulse time, repetition time, echo time (TE), maximum b factor, mean age, mean body weight, fat suppression, number of benign and malignant lesions, and true positive, true negative, false positive and false negative results. All analyses were performed using Meta-DiSc and Stata 11.0.

RESULTS: The pooled sensitivity and specificity of single-shot EPI DWI were 0.83 (95%CI: 0.79-0.87) and 0.77 (95%CI: 0.70-0.83), respectively. The positive likelihood ratio and negative likelihood ratio were 5.09 (95%CI: 2.19-11.84) and 0.23 (95%CI: 0.15-0.36), respectively. The P value for the χ² heterogeneity for all pooled estimates was < 0.05. From the fitted summary receiver operating characteristic curve, the area under the curve and Q* index were 0.89 and 0.82, respectively. Publication bias was not present (t = 0.58, P = 0.58). Meta-regression analysis indicated that fat suppression, mean age, TE, and maximum b factor were not sources of heterogeneity (all P > 0.05).

CONCLUSION: Single-shot EPI DWI is useful to differentiate between malignant and benign pancreatic lesions. Lesion size ≥ 2 cm is the limit for the diagnosis of early lesions.

EUS-derived criteria for distinguishing benign from malignant metastatic solid hepatic masses

BACKGROUND

Detection of hepatic metastases during EUS is an important component of tumor staging.

OBJECTIVE

To describe our experience with EUS-guided FNA (EUS-FNA) of solid hepatic masses and derive and validate criteria to help distinguish between benign and malignant hepatic masses.

DESIGN

Retrospective study, survey.

SETTING

Single, tertiary-care referral center.

PATIENTS

Medical records were reviewed for all patients undergoing EUS-FNA of solid hepatic masses over a 12-year period.

INTERVENTIONS

EUS-FNA of solid hepatic masses.

MAIN OUTCOME MEASUREMENTS

Masses were deemed benign or malignant according to predetermined criteria. EUS images from 200 patients were used to create derivation and validation cohorts of 100 cases each, matched by cytopathologic diagnosis. Ten expert endosonographers blindly rated 15 initial endosonographic features of each of the 100 images in the derivation cohort. These data were used to derive an EUS scoring system that was then validated by using the validation cohort by the expert endosonographer with the highest diagnostic accuracy.

RESULTS

A total of 332 patients underwent EUS-FNA of a hepatic mass. Interobserver agreement regarding the initial endosonographic features among the expert endosonographers was fair to moderate, with a mean diagnostic accuracy of 73% (standard deviation 5.6). A scoring system incorporating 7 EUS features was developed to distinguish benign from malignant hepatic masses by using the derivation cohort with an area under the receiver operating curve (AUC) of 0.92; when applied to the validation cohort, performance was similar (AUC 0.86). The combined positive predictive value of both cohorts was 88%.

LIMITATIONS

Single center, retrospective, only one expert endosonographer deriving and validating the EUS criteria.

CONCLUSION

An EUS scoring system was developed that helps distinguish benign from malignant hepatic masses. Further study is required to determine the impact of these EUS criteria among endosonographers of all experience.

Is quality and completeness of reporting of systematic reviews and meta-analyses published in high impact radiology journals associated with citation rates?

Purpose

The purpose of this study is to determine whether study quality and completeness of reporting of systematic reviews (SR) and meta-analyses (MA) published in high impact factor (IF) radiology journals is associated with citation rates.

Methods

All SR and MA published in English between Jan 2007–Dec 2011, in radiology journals with an IF >2.75, were identified on Ovid MEDLINE. The Assessing the Methodologic Quality of Systematic Reviews (AMSTAR) checklist for study quality, and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist for study completeness, was applied to each SR & MA. Each SR & MA was then searched in Google Scholar to yield a citation rate. Spearman correlation coefficients were used to assess the relationship between AMSTAR and PRISMA results with citation rate. Multivariate analyses were performed to account for the effect of journal IF and journal 5-year IF on correlation with citation rate. Values were reported as medians with interquartile range (IQR) provided.

Results

129 studies from 11 journals were included (50 SR and 79 MA). Median AMSTAR result was 8.0/11 (IQR: 5–9) and median PRISMA result was 23.0/27 (IQR: 21–25). The median citation rate for SR & MA was 0.73 citations/month post-publication (IQR: 0.40–1.17). There was a positive correlation between both AMSTAR and PRISMA results and SR & MA citation rate; ρ=0.323 (P=0.0002) and ρ=0.327 (P=0.0002) respectively. Positive correlation persisted for AMSTAR and PRISMA results after journal IF was partialed out; ρ=0.243 (P=0.006) and ρ=0.256 (P=0.004), and after journal 5-year IF was partialed out; ρ=0.235 (P=0.008) and ρ=0.243 (P=0.006) respectively.

Conclusion

There is a positive correlation between the quality and the completeness of a reported SR or MA with citation rate which persists when adjusted for journal IF and journal 5-year IF.

Differential diagnosis between hepatic metastases and benign focal lesions using DWI with parallel acquisition technique: a meta-analysis

We aim to investigate the diagnostic capability of diffusion-weighted imaging using parallel acquisition technique for the differentiation between hepatic metastases and benign focal lesions with a meta-analysis. The meta-analysis included a total of 858 hepatic metastases and 440 benign liver lesions from nine studies. The pooled sensitivity and specificity of diffusion-weighted imaging (DWI) were 0.87 (95% CI, 0.84-0.89) and 0.90 (95% CI, 0.87-0.93), respectively. The positive likelihood ratio (PLR) and negative likelihood ratio (NLR) were 8.50 (95% CI, 4.97-14.52) and 0.17 (95% CI, 0.11-0.26), respectively. The P value for χ (2) heterogeneity for all pooled estimates was <0.05. From the fitted summary receiver operating characteristics (SROC), the area under the curve (AUC) and Q* index were 0.95 and 0.88, respectively. Publication bias is not present (t = -0.76, P = 0.471). The meta-regression analysis indicated that evaluated covariates included patient number, patient population, mean age, maximum of b factor, number of cysts, number of hemangiomas, and field were not sources of heterogeneity (all P value >0.05). Diffusion-weighted imaging was useful for differentiation between hepatic metastases and benign focal lesions. The diffusion characteristics of the benign hepatocellular lesions, including cases of focal nodular hyperplasia (FNH) and adenoma, have rarely been reported and need further studies. The diagnostic capability of DWI with parallel acquisition technique for differentiation between metastases and benign hepatic focal lesions might be overestimated.

Can a b value of 500 be substituted for a b value of 1000 in the characterization of focal liver lesions?

PURPOSE

Comparison of two different b values in diffusion-weighted magnetic resonance imaging (DWI) for characterization of focal liver lesions.

METHODS

A total of 174 focal liver lesions from 100 patients were analyzed using two different b values (500 and 1000 s/mm(2)). The DWI with b values of 500 s/mm(2) (DWI500) and 1000 s/mm(2) (DWI1000) were analyzed using the Mann-Whitney test, kappa statistic, and paired t test with respect to image quality. The statistically significant differences between DWI500 and DWI1000 in the characterization of the lesions with respect to the cutoff ADC values were evaluated via χ (2) test.

RESULTS

DWI500 had the highest mean score in the qualitative evaluation of image quality (p < 0.0001) and the highest signal-to-noise ratio (8.7 ± 2.1; p < 0.0001). The sensitivity, specificity, and AUC for discriminating malignant from benign focal lesions on DWI500 and DWI1000 using cutoff ADC values of 1.54 × 10(-3) and 1.38 × 10(-3) s/mm(2) were 95.8%, 92.3%, 0.98, and 93.8%, 92.3%, 0.97, respectively. There was no statistically significant difference in sensitivity, specificity, and AUC values between DWI500 and DWI1000 with respect to the cutoff ADC values (p > 0.05).

CONCLUSIONS

The image quality of DWI500 was better than that of DWI1000, and there was no significant difference between DWI500 and DWI1000 in the characterization of the lesions with respect to the cutoff ADC values. The b value of 500 s/mm(2) can be substituted for the b value of 1000 s/mm(2) in the characterization of focal liver lesions.

Diffusion-weighted imaging for the left hepatic lobe has higher diagnostic accuracy for malignant focal liver lesions

BACKGROUND

This study was conducted to investigate whether apparent diffusion coefficient (ADC) measurements by dividing the liver into left and right hepatic lobes may be utilized to improve the accuracy of differential diagnosis of benign and malignant focal liver lesions.

MATERIALS AND METHODS

A total of 269 consecutive patients with 429 focal liver lesions were examined by 3-T magnetic resonance imaging that included diffusion-weighted imaging. For 58 patients with focal liver lesions of the same etiology in left and right hepatic lobes, ADCs of normal liver parenchyma and focal liver lesions were calculated and compared using the paired t-test. For all 269 patients, ADC cutoffs for focal liver lesions and diagnostic accuracy in the left hepatic lobe, right hepatic lobe and whole liver were evaluated by receiver operating characteristic curve analysis.

RESULTS

For the group of 58 patients, mean ADCs of normal liver parenchyma and focal liver lesions in the left hepatic lobe were significantly higher than those in the right hepatic lobe. For differentiating malignant lesions from benign lesions in all patients, the sensitivity and specificity were 92.6% and 92.0% in the left hepatic lobe, 94.4% and 94.4% in the right hepatic lobe, and 90.4% and 94.7% in the whole liver, respectively. The area under the curve of the right hepatic lobe, but not the left hepatic lobe, was higher than that of the whole liver.

CONCLUSIONS

ADCs of normal liver parenchyma and focal liver lesions in the left hepatic lobe were significantly higher than those in the right hepatic lobe. Optimal ADC cutoff for focal liver lesions in the right hepatic lobe, but not in the left hepatic lobe, had higher diagnostic accuracy compared with that in the whole liver.

Diffusion-weighted MRI and optimal b-value for characterization of liver lesions

BACKGROUND

Diffusion-weighted imaging (DWI) is commonly used to distinguish between benign and malignant liver lesions. However, different b-values are recommended.

PURPOSE

To determine the most suitable b-value in DWI for differentiation of benign and malignant liver lesions.

MATERIAL AND METHODS

A total of 124 lesions in 89 consecutive patients (43 men, 46 women; age, mean ± standard deviation, 58 ± 14 years) with a pathological or radiological diagnosis of malignant or benign focal liver lesions after magnetic resonance imaging (MRI) were included in this study. Routine abdominal MRI and DWI were performed using seven b-values (0, 50, 200, 400, 600, 800, 1000 s/mm(2)). Lesions were analyzed for benignity/malignity using apparent diffusion coefficient (ADC) values with 10 b-value combinations and by measuring the lesion/normal parenchyma ADC ratio.

RESULTS

Mean ADC values were significantly different between malignant and benign lesions for all b-value combinations (P=0.000). The best b-value combination was 0 and 800 (Az=0.935). Using lower b-values such as 0 and 50 together with higher b-values ≥ 600 s/mm(2) was beneficial (Az=0.928 and 0.927). Mean ADC values were approximately 13% (1-15%) higher in total when b=0 and b=50 s/mm(2) were included in multiple b-value combinations.

CONCLUSION

In DWI, we recommend the use of b-values of 0 and 800 s/mm(2) as two b-values, or b=0, 50, 600, 800, and 1000 s/mm(2) as multiple b-values for distinguishing between benign and malignant liver lesions. Mean ADC value is 13% higher in total by additional use of b=0 and b=50 s/mm(2) in multiple b-value combinations.

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

OBJECTIVE

The objective of this study was to compare the value of the apparent diffusion coefficient (ADC) determined with 3 b values and the intravoxel incoherent motion (IVIM)-derived parameters in the determination of malignancy and characterization of hepatic tumor type.

MATERIALS AND METHODS

Seventy-six patients with 86 solid hepatic lesions, including 8 hemangiomas, 20 lesions of focal nodular hyperplasia, 9 adenomas, 30 hepatocellular carcinomas, 13 metastases, and 6 cholangiocarcinomas, were assessed in this prospective study. Diffusion-weighted images were acquired with 11 b values to measure the ADCs (with b = 0, 150, and 500 s/mm) and the IVIM-derived parameters, namely, the pure diffusion coefficient and the perfusion-related diffusion fraction and coefficient. The diffusion parameters were compared between benign and malignant tumors and between tumor types, and their diagnostic value in identifying tumor malignancy was assessed.

RESULTS

The apparent and pure diffusion coefficients were significantly higher in benign than in malignant tumors (benign: 2.32 [0.87] × 10 mm/s and 1.42 [0.37] × 10 mm/s vs malignant: 1.64 [0.51] × 10 mm/s and 1.14 [0.28] × 10 mm/s, respectively; P < 0.0001 and P = 0.0005), whereas the perfusion-related diffusion parameters did not differ significantly between the 2 groups. The apparent and pure diffusion coefficients provided similar accuracy in assessing tumor malignancy (areas under the receiver operating characteristic curve of 0.770 and 0.723, respectively). In the multigroup analysis, the ADC was found to be significantly higher in hemangiomas than in hepatocellular carcinomas, metastases, and cholangiocarcinomas. In the same manner, it was higher in lesions of focal nodular hyperplasia than in metastases and cholangiocarcinomas. However, the pure diffusion coefficient was significantly higher only in hemangiomas versus hepatocellular and cholangiocellular carcinomas.

CONCLUSIONS

Compared with the ADC, the diffusion parameters derived from the IVIM model did not improve the determination of malignancy and characterization of hepatic tumor type.

Liver lesion detection and characterization: role of diffusion-weighted imaging

Diffusion-weighted imaging (DWI) plays an emerging role for the assessment of focal and diffuse liver diseases. This growing interest is due to that fact that DWI is a noncontrast technique with inherent high contrast resolution, with promising results for detection and characterization of focal liver lesions. Recent advances in diffusion image quality have also added interest to this technique in the abdomen. The purpose of this review is to describe the current clinical roles of DWI for the detection and characterization of focal liver lesions, and to review pitfalls, limitations, and future directions of DWI for assessment of focal liver disease.

Does diffusion-weighted imaging add diagnostic confidence in discriminating between benign and malignant solid focal liver lesions?

We investigated whether diffusion-weighted Imaging (DWI) adds diagnostic confidence in assessing focal liver lesions (FLLs). By reviewing FLLs without and with DWI at 1.5 T, two radiologists scored the confidence in diagnosing benignancy/malignancy (confidence score), and DWI usefulness (usefulness score). We showed that adding DWI significantly decreased the confidence score of the most experienced radiologist and increased his confidence in false-negative diagnoses showing atypical features on conventional magnetic resonance imaging.

Diffusion analysis with triexponential function in hepatic steatosis

Our purpose was to assess the influence of liver steatosis on diffusion by triexponential analysis. Thirty-three patients underwent diffusion-weighted magnetic resonance imaging with multiple b values for perfusion-related diffusion, fast free diffusion, and slow restricted diffusion coefficients (D p, D f, D s) and fractions (F p, F f, F s). They also underwent dual-echo gradient-echo imaging for measurement of the hepatic fat fraction (HFF). Of these, 13 patients were included in the control group and 20 in the fatty liver group with HFF >5 %. The parameters of the two groups were compared by use of the Mann-Whitney U test. The relationships between diffusion coefficients and HFFs were assessed by use of the Pearson correlation. D p and D f were reduced significantly in the steatotic liver group compared with those in the control group (D p = 27.72 ± 6.61 × 10(-3) vs. 33.33 ± 6.47 × 10(-3) mm(2)/s, P = 0.0072; D f = 1.70 ± 0.53 × 10(-3) vs. 2.06 ± 0.40 × 10(-3) mm(2)/s, P = 0.0224). There were no significant differences in the other parameters between the two groups. Furthermore, D p and D f were correlated with HFF (P < 0.0001, r = -0.64 and P = 0.0008, r = -0.56, respectively). Decreased liver perfusion in steatosis caused the reduction in D p, and extracellular fat accumulation and intracellular fat droplets in steatosis led to the reduction in D f. Thus, the influence of hepatic steatosis should be taken into consideration when triexponential function analysis is used for assessment of diffuse liver disease.

Contrast-Enhanced Ultrasound for the differentiation of benign and malignant focal liver lesions: a meta-analysis

BACKGROUND

International guidelines of Ultrasound recommend the performance of contrast-enhanced ultrasound (CEUS) as the first method of choice after conventional ultrasound for the diagnostic work-up of focal liver lesions. However, these recommendations are based on the results of multiple single studies and only few large multicentre studies.

AIMS

The rationale of the present systematic review and meta-analysis was to assess the overall sensitivity and specificity of CEUS for the diagnosis of malignant liver lesions.

METHODS

Literature databases were searched up to March 2012. Inclusion criteria were evaluation of CEUS, assessment of sensitivity and specificity of CEUS for the diagnosis of malignant liver lesions. The meta-analysis was performed using the random-effects model based on the DerSimonian Laird method. Quality analyses were carried out to assess sources of heterogeneity.

RESULTS

A total of 45 studies with 8147 focal liver lesions were included in the analysis. Overall sensitivity and specificity of CEUS for the diagnosis of malignant liver lesions was 93% (95%-CI: 91-95%) and 90% (95%-CI: 88-92%) respectively. Significant heterogeneity was found between studies. However, subanalysis revealed no significant difference when evaluating studies using histology for all liver lesions, when comparing high-quality and low-quality studies, and blinded vs non-blinded studies.

CONCLUSION

The results of this meta-analysis support the international recommendations on CEUS for the diagnostic work-up of focal liver lesions selecting patients who need further diagnostics.

A pooled analysis of diffusion-weighted imaging in the diagnosis of hepatocellular carcinoma in chronic liver diseases

BACKGROUND AND AIM

The purpose of this study was to perform a meta-analysis of all available studies of the diagnostic performance of diffusion-weighted imaging (DWI) in the detection of hepatocellular carcinoma (HCC) in patients with chronic liver disease.

METHODS

Databases including MEDLINE and EMBASE were searched for relevant original articles published from January 2000 to April 2012. Pooled estimation and subgroup analysis data were obtained by statistical analysis.

RESULTS

Across the nine studies (476 patients), DWI sensitivity was 81% (95%CI: 67%-90%), and specificity was 89% (95% CI: 76%-95%). Overall, positive likelihood ratio was 7.11 (95%CI: 3.50, 14.48), negative likelihood ratio was 0.21 (95%CI: 0.12-0.37), and the diagnostic odds ratio (DOR) was 33.48 (95%CI: 16.67-67.25). The area under the curve of the summary receiver operator characteristic (ROC) was 0.92 (95% CI:0.89-0.94). In studies in which both DWI and conventional contrast-enhanced magnetic resonance imaging (CE-MRI) were performed, the comparison of DWI performance with that of conventional CE-MRI suggested no major differences against these two methods (P > 0.05). DWI combined CE-MRI had higher pooled sensitivity than DWI alone (93% vs 73%) (P < 0.05).

CONCLUSION

DWI has good diagnostic performance in the detection of HCC in patients with chronic liver disease and equivalent to conventional CE-MRI. Combination of CE-MRI and DWI can improve the diagnostic accuracy of MRI. Further larger prospective studies are still needed to establish its value for detecting HCC in patients with chronic liver disease.

That liver lesion on MDCT in the oncology patient: is it important?

Multidetector-row computed tomography (MDCT) has become the primary imaging test for the staging and follow-up of most malignancies that originate outside of the central nervous system. Technical advances in this imaging technique have led to significant improvement in the detection of metastatic disease to the liver. An unintended by-product of this improving diagnostic acumen is the discovery of incidental hepatic lesions in oncology patients that in the past remained undetected. These ubiquitous, incidentally identified hepatic lesions have created a management dilemma for both clinicians and radiologists: are these lesions benign or do they represent metastases? Naturally, the answer to this question has profound prognostic and therapeutic implications. In this review, guidelines concerning the diagnosis and management of some of the more common hepatic incidental lesions detected in patients with extrahepatic malignancies are presented.

Accuracy of visual analysis vs. apparent diffusion coefficient quantification in differentiating solid benign and malignant focal liver lesions with diffusion-weighted imaging

PURPOSE

The authors compared the accuracy of diffusion-weighted imaging (DWI) visual analysis (VA) vs. apparent diffusion coefficient quantification (ADC-Q) in assessing malignancy of solid focal liver lesions (FLLs).

MATERIALS AND METHODS

Using a 1.5-T system, two radiologists retrospectively assessed as benign or malignant 50 solid FLLs: (a) by VA of signal intensity on DWI images at b=800 s/mm(2) and ADC map; (b) by quantifying lesion ADC. Reference standard included histology or follow-up confirmation of diagnosis by a consensus panel. Receiver operating characteristic (ROC) curve analysis was performed.

RESULTS

because of 20 false-negative hepatocellular carcinomas, VA showed lower accuracy than ADC-Q (52.0% VS. 68.0%). however, stratified accuracy for metastases was higher with VA (75.0 VS. 66%). ADC and signal features of malignant and benign FLLs were found to largely overlap.

CONCLUSIONS

VA performed worse than ADC-Q for hepatocellular carcinoma and better for metastases. Overall, the accuracy of both methods was limited because of the overlap in visual appearance and ADC values between solid benign and malignant FLLs.

Diffusion weighted MR imaging in patients with HCC and liver cirrhosis after administration of different gadolinium contrast agents: is it still reliable?

PURPOSE

Diffusion weighted imaging (DWI) is an emerging technique for abdominal MR and usually performed before intravenous contrast injection. Recent studies performed in patients with normal liver function have shown that DWI can be performed after gadolinium administration. Aim of this study was to compare DWI before and after administration of different gadolinium compounds in patients with HCC and liver cirrhosis.

MATERIALS AND METHODS

15 patients with known HCC and liver cirrhosis underwent liver MRI at 1.5T (Magnetom Avanto, Siemens) including DWI on day 1 before and after administration of gadobutrol (Gadovist(®)) and on day 2 after administration of EOB-Gadolinium-DTPA (Primovist(®)). Signal to noise ratios (SNR) and contrast to noise ratios (CNR) of HCC lesions were determined for all DWI data sets. Furthermore, ADC values were compared using a Wilcoxon test. A p-value <0.05 indicated statistically significant differences.

RESULTS

There were no statistically significant differences regarding SNR pre-contrast (mean: 48.1), after gadobutrol (mean: 47.7) or after EOB-Gadolinium-DTPA (mean: 50.0; values for b=50s/mm(2)). Similarly, no significant differences were found for CNR (average values:34.4 vs. 32.3 vs. 30.7; b=50s/mm(2)) nor for ADC-values (mean: 1.5 vs. 1.4 vs. 1.5×10(-3)mm(2)/s) of HCC.

CONCLUSION

There is no significant difference regarding DWI in patients with cirrhosis before and after contrast injection. Hence, it is reliable to run DWI after gadolinium either as an alternative for unsuccessful pre-contrast DWI or as a gap filler to spare time in EOB-Gadolinium-DTPA imaging.