Differentiation between cavernous hemangiomas and untreated malignant neoplasms of the liver with free-breathing diffusion-weighted MR imaging: Comparison with T2-weighted fast spin-echo MR imaging

Differentiation of Hepatocellular Carcinoma from Hepatic Hemangioma and Focal Nodular Hyperplasia using Computed Tomographic Spectral Imaging

BACKGROUND AND AIMS

Hepatocellular carcinoma (HCC) is the most common primary hepatic malignancy. This study was designed to investigate the value of computed tomography (CT) spectral imaging in differentiating HCC from hepatic hemangioma (HH) and focal nodular hyperplasia (FNH).

METHODS

This was a retrospective study of 51 patients who underwent spectral multiple-phase CT at 40-140 keV during the arterial phase (AP) and portal venous phase (PP). Slopes of the spectral curves, iodine density, water density derived from iodine- and water-based material decomposition images, iodine uptake ratio (IUR), normalized iodine concentration, and the ratio of iodine concentration in liver lesions between AP and PP were measured or calculated.

RESULTS

As energy level decreased, the CT values of HCC (n=31), HH (n=17), and FNH (n=7) increased in both AP and PP. There were significant differences in IUR in the AP, IUR in the PP, normalized iodine concentration in the AP, slope in the AP, and slope in the PP among HCC, HH, and FNH. The CT values in AP, IUR in the AP and PP, normalized iodine concentration in the AP, slope in the AP and PP had high sensitivity and specificity in differentiating HH and HCC from FNH. Quantitative CT spectral data had higher sensitivity and specificity than conventional qualitative CT image analysis during the combined phases.

CONCLUSIONS

Mean CT values at low energy (40-90 keV) and quantitative analysis of CT spectral data (IUR in the AP) could be helpful in the differentiation of HCC, HH, and FNH.

Current state of the art imaging approaches for colorectal liver metastasis

One of the most common cancers worldwide, colorectal cancer (CRC) has been associated with significant morbidity and mortality and therefore represents an enormous burden to the health care system. Recent advances in CRC treatments have provided patients with primary and metastatic CRC a better long-term prognosis. The presence of synchronous or metachronous metastasis has been associated, however, with worse survival. The most common site of metastatic disease is the liver. A variety of treatment modalities aimed at targeting colorectal liver metastases (CRLM) has been demonstrated to improve the prognosis of these patients. Loco-regional approaches such as surgical resection and tumor ablation (operative and percutaneous) can provide patients with a chance at long-term disease control and even cure in select populations. Patient selection is important in defining the most suitable treatment option for CRLM in order to provide the best possible survival benefit while avoiding unnecessary interventions and adverse events. Medical imaging plays a crucial role in evaluating the characteristics of CRLMs and disease resectability. Size of tumors, proximity to adjacent anatomical structures, and volume of the unaffected liver are among the most important imaging parameters to determine the suitability of patients for surgical management or other appropriate treatment approaches. We herein provide a comprehensive overview of current-state-of-the-art imaging in the management of CRLM, including staging, treatment planning, response and survival assessment, and post-treatment surveillance. Computed tomography (CT) scan and magnetic resonance imaging (MRI) are two most commonly used techniques, which can be used solely or in combination with functional imaging modalities such as positron emission tomography (PET) and diffusion weighted imaging (DWI). Providing up-to-date evidence on advantages and disadvantages of imaging modalities and tumor assessment criteria, the current review offers a practice guide to assist providers in choosing the most suitable imaging approach for patients with CRLM.

[Differential diagnosis of hepatocellular carcinoma and hepatic hemangiomas based on radiomic features of gadoxetate disodium-enhanced magnetic resonance imaging]

OBJECTIVE

To evaluate the feasibility of using radiomic features for differential diagnosis of hepatocellular carcinoma (HCC) and hepatic cavernous hemangioma (HHE).

METHODS

Gadoxetate disodium-enhanced magnetic resonance imaging data were collected from a total of 135 HCC and HHE lesions. The radiomic texture features of each lesion were extracted on the hepatobiliary phase images, and the performance of each feature was assessed in differentiation and classification of HCC and HHE. In multivariate analysis, the performance of 3 feature selection algorithms (namely minimum redundancy-maximum relevance, mRmR; neighborhood component analysis, NCA; and sequence forward selection, SFS) was compared. The optimal feature subset was determined according to the optimal feature selection algorithm and used for testing the 3 classifier algorithms (namely the support vector machine, RBF-SVM; linear discriminant analysis, LDA; and logistic regression). All the tests were repeated 5 times with 10-fold cross validation experiments.

RESULTS

More than 50% of the radiomic features exhibited strong distinguishing ability, among which gray level co-occurrence matrix feature S (3, -3) SumEntrp showed a good classification performance with an AUC of 0.72 (P<0.01), a sensitivity of 0.83 and a specificity of 0.57. For the multivariate analysis, 15 features were selected based on the SFS algorithm, which produced better results than the other two algorithms. Testing of these 15 selected features for their average cross-validation performance with RBF-SVM classifier yielded a test accuracy of 0.82∓0.09, an AUC of 0.86∓0.12, a sensitivity of 0.88∓0.11, and a specificity of 0.76∓0.18.

CONCLUSION

The radiomic features based on gadoxetate disodium-enhanced magnetic resonance images allow efficient differential diagnosis of HCC and HHE, and can potentially provide important assistance in clinical diagnosis of the two diseases.

[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.

Could ADC values be a promising diagnostic criterion for differentiating malignant and benign hepatic lesions in Asian populations: A meta-analysis

BACKGROUND

Liver cancer exhibits geographic and ethnic differences in its prevalence and biology, which implies that it is impractical to develop universal guidelines for all patients. Thus, a meta-analysis was conducted to identify the accuracy of apparent diffusion coefficients (ADCs) for discriminating malignant from benign liver lesions in Asians.

METHODS

Eligible studies published in PubMed, Ovid, and Embase/Medline were updated onto October 2014. STATA 12.0 and Meta-Disc 1.4 were used to perform this meta-analysis.

RESULTS

Eight studies comprising 661 benign liver lesions and 598 malignant liver lesions fulfilled all the inclusion criteria. The pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and diagnostic odds ratio were 0.88 (95% confidence interval [CI] 0.75-0.95), 0.93 (95% CI 0.86-0.97), 12.42 (95% CI 6.09-25.31), 0.13 (95% CI 0.06-0.29), and 95.58 (95% CI 35.29-258.89), respectively. Overall, the area under the summary receiver-operating characteristic curve was 0.96 (95% CI 0.94-0.98). Heterogeneity was found to originate potentially from the type of benign lesion. A subgroup analysis showed that differentiating between hemangiomas, cysts, and malignant liver lesions produced a significantly higher diagnostic accuracy than that of solid liver lesions.

CONCLUSION

Our meta-analysis indicated that ADC could be promising for characterizing liver lesions among Asians, indicating that the ADC value is a promising diagnostic criterion candidate. Meanwhile, the use of dual b values could be sufficient for liver lesion characterization. However, large-scale, high-quality trials should be conducted to identify specific standards, including cut-off values for further development of diffusion-weighted imaging as a routine clinical application among Asian populations.

High-flow haemangiomas versus hypervascular hepatocellular carcinoma showing "pseudo-washout" on gadoxetic acid-enhanced hepatic MRI: value of diffusion-weighted imaging in the differential diagnosis of small lesions

AIM

To validate the usefulness of diffusion-weighted imaging (DWI) in the differentiation of high-flow haemangiomas showing pseudo-washout appearance on gadoxetic acid-enhanced hepatic MRI from small hypervascular hepatocellular carcinomas (HCCs).

MATERIALS AND METHODS

DWI (b=50, 800 s/mm²) with apparent diffusion coefficient (ADC) maps for 50 haemangiomas (6.4±2.9 mm) showing intense enhancement on arterial dominant phase imaging and hypointensity on transitional and/or hepatobiliary phase imaging during gadoxetic acid-enhanced MRI were retrospectively analysed and compared with that of 113 hypervascular HCCs (12.8±3.7 mm). In addition to measurement of mean ADC values on DWI and contrast-to-noise ratio (CNR) on corresponding T2-weighted imaging, qualitative analysis of DWI was performed for each lesion by two independent observers using a five-point scale.

RESULTS

Both of mean ADC value (1.902 versus 0.997×10^-3 mm²/s) and mean CNR (119.2 versus 36.9) for haemangioma were significantly larger than for HCC (p<0.001). On receiver operating characteristic (ROC) analysis, an area under the curve (AUC) of 0.995 for ADC values was significantly larger than 0.915 for CNRs (p=0.002). When the ADC value of 1.327×10^-3 mm²/s was used as the threshold for the diagnosis of haemangioma, the sensitivity and specificity were 98% and 97.3%, respectively. The mean sensitivity and specificity of qualitative analysis for the differentiation of haemangioma from HCC were 92% and 99.1%, respectively.

CONCLUSION

For high-flow small haemangiomas showing pseudo-washout appearance during gadoxetic acid-enhanced hepatic MRI, high b-factor DWI including an ADC map may provide additional information to enhance the confidence to exclude small hypervascular HCCs.

Diffusion-weighted magnetic resonance imaging in colorectal cancer

Magnetic resonance imaging (MRI) plays now a major role in patients with colorectal cancer regarding tumor staging, surgical planning, therapeutic decision, assessment of tumor response to chemoradiotherapy and surveillance of rectal cancer, and detection and characterization of liver or peritoneal metastasis of colorectal cancers. Diffusion-weighted MRI (DW-MRI) is a functional imaging tool that is now part of the standard MRI protocol for the investigation of patients with colorectal cancer. DW-MRI reflects micro-displacements of water molecules in tissues and conveys high degrees of accuracy to discriminate between benign and malignant colorectal conditions. Thus, in addition to morphological imaging, DW-MRI has an important role to accurately detect colorectal neoplasms and peritoneal implants, to differentiate benign focal liver lesions from metastases and to detect tumor relapse within fibrotic changes. This review provides a comprehensive overview of basic principles, clinical applications and future trends of DW-MRI in colorectal cancers.

MR imaging features of focal liver lesions in Wilson disease

Hepatic involvement in Wilson disease (WD) manifests as a diffuse chronic disease in the majority of patients. However, in a subset of patients focal liver lesions may develop, presenting with a wide range of imaging features. The majority of focal liver lesions in patients with WD are benign nodules, but there are reports that have described malignant liver tumors or dysplastic nodules in these patients. Because of the possibility of malignant transformation of liver nodules, major concerns have been raised with respect to the management and follow-up of patients with WD in whom focal liver lesions have been identified. The assessment of liver involvement in patients with WD is generally performed with ultrasonography. However, ultrasonography conveys limited specificity so that magnetic resonance (MR) imaging is often performed to improve lesion characterization. This review was performed to illustrate the spectrum of MR imaging features of focal liver lesions that develop in patients with WD. It is assumed that familiarity with the MR imaging presentation of focal liver lesions in WD may help clarify the actual nature of hepatic nodules in patients with this condition.

Feasibility of Routine Application of Gadoxetic Acid-Enhanced MRI in Combination with Diffusion-Weighted MRI for the Preoperative Evaluation of Colorectal Liver Metastases

BACKGROUND

Gadoxetic acid-enhanced magnetic resonance imaging (MRI) in combination with diffusion-weighted MRI (Gd-EOB-MRI/DWI) has become popular for evaluating colorectal liver metastases (CRLM). This retrospective observational study aimed to determine whether this procedure should be indicated prior to hepatectomy in all patients with CRLM.

METHODS

A retrospective survey of relevant data of patients who had undergone hepatectomy for CRLM from 2008 to 2014 was performed. The rates of detection by contrast-enhanced computed tomography (CE-CT) and Gd-EOB-MRI/DWI were evaluated. In addition, relapse-free and overall survivals after primary hepatectomy were compared between patients who had undergone only CE-CT versus those who had undergone both CE-CT and Gd-EOB-MRI/DWI.

RESULTS

In all, 419 pathologically confirmed CRLM were resected in 202 hepatectomies in 177 patients. The sensitivity of detection of CRLM was 77 % for CE-CT and 93 % for Gd-EOB-MRI/DWI (P < 0.01). The sensitivity of detection of 1-5, 6-10, and 11-15 mm CRLM by CE-CT was 9.6 % (5/52), 47 % (26/55), and 76 % (57/75), respectively, whereas that by Gd-EOB-MRI/DWI was 54 % (28/52), 91 % (50/55), and 99 % (74/75), respectively; these differences are significant (P < 0.01 for all three groups). Relapse-free (P = 0.99) and overall survival (P = 0.79) did not differ significantly between 37 patients evaluated preoperatively by only CE-CT and 168 patients evaluated by both CE-CT and Gd-EOB-MRI/DWI.

CONCLUSION

Gd-EOB-MRI/DWI detects small CRLM (≤15 mm) with higher sensitivity than CE-CT. However, whether Gd-EOB-MRI/DWI should be a routine component of preoperative evaluation remains unclear in terms of survival benefit.

Diffusion-weighted MRI in Crohn's disease: Current status and recommendations

Over the past years, technological improvements and refinements in magnetic resonance imaging (MRI) hardware have made high-quality diffusion-weighted imaging (DWI) routinely possible for the bowel. DWI is promising for the detection and characterization of lesions in Crohn's disease (CD) and has been advocated as an alternative to intravenous gadolinium-based contrast agents. Furthermore, quantification using the apparent diffusion coefficient may have value as a biomarker of CD activity and has shown promise. In this article we critically review the literature pertaining to the value of DWI in CD for detection, characterization, and quantification of disease activity and complications. Although the body of supportive evidence is growing, it is clear that well-designed, multicenter studies are required before the role of DWI in clinical practice can be fully established. J. Magn. Reson. Imaging 2016;44:1381-1396.

Focal nodular hyperplasia of the liver: diffusion-weighted magnetic resonance imaging characteristics using high b values

OBJECTIVE

To qualitatively and quantitatively assess the presentation of hepatic focal nodular hyperplasia (FNH) at diffusion-weighted magnetic resonance imaging (DWMRI) using multiple high b values.

MATERIALS AND METHODS

Twenty-five patients with 27 FNHs had liver DWMRI at 1.5 T using free-breathing acquisition and 3 b values (0, 600, 1000 s/mm). Focal nodular hyperplasias were evaluated qualitatively using visual analysis of diffusion-weighted magnetic resonance (DWMR) images and quantitatively using conventional apparent diffusion coefficient (ADC) and normalized ADC measurements.

RESULTS

All FNHs (100%) were visible on b0 DWMR images; 26 of the 27 FNHs (96%), on b600 DWMR images; and 21 of the 27 FNHs (78%), on b1000 DWMR images. A total of 18 of the 27 FNHs (67%) exhibited a hyperintense central scar on the b0 DWMR images that remained visible on the b600 and b1000 DWMR images in 6 of the 27 FNHs (22%). Conventional ADC value of FNHs (1.318 × 10 mm/±0.208) was significantly lower than that of adjacent hepatic parenchyma (1.414 × 10 mm/s ± 1.95) (P = 0.0003), although a substantial overlap was found. The use of normalized ADC using the liver as reference organ resulted in a more restricted distribution of ADC values (variation coefficient, 5.3%).

CONCLUSIONS

Focal nodular hyperplasias show a wide range of morphological features at DWMRI using high b values. Further studies are needed to fully investigate as to what extent normalized ADC may result in better lesion characterization.

Utility of R2* obtained from T2*-weighted imaging in differentiating hepatocellular carcinomas from cavernous hemangiomas of the liver

Purpose

To evaluate the feasibility of applying R₂* values to differentiate hepatocellular carcinomas (HCC) from cavernous hemangiomas of the liver (CHL).

Materials and Methods

This retrospective study was approved by the participating Institutional Review Board and written informed consent for all subjects were obtained. Seventy-three patients with 79 pathologically identified HCCs and 65 patients with 91 clinically or pathologically identified CHLs were enrolled in this study. All subjects underwent a breath-hold multi-echo T₂* weighted MR imaging on a 1.5T clinical MR scanner. R₂* values from HCC and CHL groups were compared using the Mann-Whitney non-parametric U test. A cut-off value of R₂* was evaluated with receiver operator characteristic (ROC) analysis.

Results

The mean R₂* value was 23.32±12.23 Hz (95% confidence interval [CI]: 20.58 Hz, 26.06 Hz) for the HCC group, and 3.66±2.37 Hz (95% CI: 3.17 Hz, 4.15 Hz) for the CHL group. The mean R₂* value for HCC was significantly higher than that of CHL (p<0.001). A threshold of 9.48 Hz for the minimum R₂* value in the diagnosis of HCC resulted in a sensitivity of 96.20% (76 out of 79 patients), and a specificity of 97.80% (89 out of 91 patients). The positive predictive value (PPV), negative predictive value (NPV) and diagnostic accuracy for HCC were 97.44% (76 out of 78 patients), 96.74% (89 out of 92 patients) and 97.06% (165 out of 170 patients), respectively. The AUC for differentiation between these two groups was 0.994 (95% CI: 0.980, 1.000).

Conclusions

R₂* is a significant MRI biomarker to differentiate HCC from CHL with satisfying sensitivity and specificity.

Liver diffusion-weighted MR imaging: reproducibility comparison of ADC measurements obtained with multiple breath-hold, free-breathing, respiratory-triggered, and navigator-triggered techniques

PURPOSE

To prospectively compare the reproducibility of normal liver apparent diffusion coefficient (ADC) measurements by using different respiratory motion compensation techniques with multiple breath-hold (MBH), free-breathing (FB), respiratory-triggered (RT), and navigator-triggered (NT) diffusion-weighted (DW) imaging and to compare the ADCs at different liver anatomic locations.

MATERIALS AND METHODS

The study protocol was approved by the institutional review board, and written informed consent was obtained from each participant. Thirty-nine volunteers underwent liver DW imaging twice. Imaging was performed with a 1.5-T MR imager with MBH, FB, RT, and NT techniques (b = 0, 100, and 500 sec/mm(2)). Three representative sections--superior, central, and inferior--were selected on left and right liver lobes, respectively. On each selected section, three regions of interest were drawn, and ADCs were measured. Analysis of variance was used to assess ADCs among the four techniques and various anatomic locations. Reproducibility of ADCs was assessed with the Bland-Altman method.

RESULTS

ADCs obtained with MBH (range: right lobe, [1.641-1.662] × 10(-3)mm(2)/sec; left lobe, [2.034-2.054] ×10(-3)mm(2)/sec) were higher than those obtained with FB (right, [1.349-1.391] ×10(-3)mm(2)/sec; left, [1.630-1.700] ×10(-3)mm(2)/sec), RT (right, [1.439-1.455] ×10(-3)mm(2)/sec; left, [1.720-1.755] ×10(-3)mm(2)/sec), or NT (right, [1.387-1.400] ×10(-3)mm(2)/sec; left, [1.661-1.736] ×10(-3)mm(2)/sec) techniques (P < .001); however, no significant difference was observed between ADCs obtained with FB, RT, and NT techniques (P = .130 to P >.99). ADCs showed a trend to decrease moving from left to right. Reproducibility in the left liver lobe was inferior to that in the right, and the central middle segment in the right lobe had the most reproducible ADC. Statistical differences in ADCs were observed in the left-right direction in the right lobe (P < .001), but they were not observed in the superior-inferior direction (P = .144-.450). However, in the left liver lobe, statistical differences existed in both directions (P = .001 to P = .016 in the left-right direction, P < .001 in the superior-inferior direction).

CONCLUSION

Both anatomic location and DW imaging technique influence liver ADC measurements and their reproducibility. FB DW imaging is recommended for liver DW imaging because of its good reproducibility and shorter acquisition time compared with that of MBH, RT, and NT techniques.

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.

Comparison of Dynamic and Liver-Specific Gadoxetic Acid Contrast-Enhanced MRI versus Apparent Diffusion Coefficients

Background

Hepatic lesions often present diagnostic connundrums with conventional MR techniques. Hepatobiliary phase contrast-enhanced imaging with gadoxetic acid can aid in the characterization of such lesions. However, quantitative measures describing late-phase enhancement must be assessed relative to their accuracy of hepatic lesion classification.

Purpose: To compare quantitative parameters in gadoxetic acid contrast-enhanced dynamic and hepatobiliary phase imaging versus apparent diffusion coefficients in hepatic lesion characterization.

Material and Methods

57 patients with focal hepatic lesions on gadoxetic acid MR were included. Lesion enhancement at standard post-contrast time points and in the hepatobiliary phase (HB; 15 and 25 minutes post-contrast) was assessed via calculation of contrast (CR) and enhancement ratios (ER). Apparent diffusion coefficient (ADC) values were also obtained. Values for these parameters were compared among lesions and ROC analyses performed.

Results: HB enhancement was greatest with FNH and adenomas. HB ER parameters but not HB CR could distinguish HCC from benign entities (0.9 ER ROC AUC versus 0.5 CR ROC AUC). There was no statistically significant difference found between the 15 and 25 minutes HB time points in detection of any lesion (p>0.4). ADC values were statistically significantly higher with hemangiomas (p<0.05) without greater accuracy in lesion detection relative to HB phase parameters.

Conclusion

Hepatobiliary phase gadoxetic acid contrast-enhanced MR characterizes focal hepatic lesions more accurately than ADC and conventional dynamic post-contrast time point enhancement parameters. ER values are generally superior to CR. No discernible benefit of 25 minute versus 15 minute delayed imaging is demonstrated.

Intravoxel incoherent motion (IVIM) MR imaging of colorectal liver metastases: are we only looking at tumor necrosis?

PURPOSE

To determine if intra-voxel incoherent motion diffusion-weighted imaging (IVIM-DWI) parameters, including free molecular-based (D) and perfusion-related (D*, f) diffusion parameters, correlate with the degree of tumor necrosis and viable tumor in colo-rectal cancer (CRC) metastasis.

MATERIALS AND METHODS

Fifteen patients referred for resection of liver metastases from CRC were retrospectively included in this Institutional Review Board approved study. An IVIM-DWI sequence was performed on a 1.5 Tesla MR imaging system, with 10 b factors (0, 10, 20, 30, 50, 80, 100, 200, 400 and 800 s/mm(2) ). Mean D, D*, f and apparent diffusion coefficient (ADC) values were determined in metastases with a longest diameter above 10 mm. Correlations between the diffusion parameters and the degree of liver tumor necrosis and viable tissue were determined (Spearman).

RESULTS

Correlation between diffusion parameters and histopathological findings was performed in 35 hepatic metastases with a diameter of more than 10 mm (mean size of 17.9 mm; range, 1-68 mm). Both D (r = 0.36; P = 0.035) and ADC (r = 0.4; P = 0.02) correlated with the degree of tumor necrosis but not with viable tumor.

CONCLUSION

ADC variation observed in CRC metastases following systemic chemotherapy reflects a specific increase in free-molecular diffusion (D), in itself correlated to the degree of metastasis necrosis.

Characterization of focal pancreatic lesions using normalized apparent diffusion coefficient at 1.5-Tesla: preliminary experience

PURPOSE

To compare the capabilities of apparent diffusion coefficient (ADC) and normalized ADC using the pancreatic parenchyma as reference organ in the characterization of focal pancreatic lesions.

PATIENTS AND METHODS

Thirty-six patients with focal pancreatic lesions (malignant, n=18; benign tumors, n=10; focal pancreatitis, n=8) underwent diffusion-weighted MR imaging (DWI) at 1.5-Tesla using 3 b values (b=0, 400, 800 s/mm(2)). Lesion ADC and normalized lesion ADC (defined as the ratio of lesion ADC to apparently normal adjacent pancreas) were compared between lesion types using nonparametric tests.

RESULTS

Significant differences in ADC values were found between malignant (1.150 × 10(-3)mm(2)/s) and benign tumors (2.493 × 10(-3)mm(2)/s) (P=0.004) and between benign tumors and mass-forming pancreatitis (1.160 × 10(-3)mm(2)/s) (P=0.0005) but not between malignant tumors and mass-forming pancreatitis (P=0.1092). Using normalized ADC, significant differences were found between malignant tumors (0.933 × 10(-3)mm(2)/s), benign tumors (1.807 × 10(-3)mm(2)/s) and mass-forming pancreatitis (0.839 × 10(-3)mm(2)/s) (P<0.0001).

CONCLUSION

Our preliminary results suggest that normalizing ADC of focal pancreatic lesions with ADC of apparently normal adjacent pancreatic parenchyma provides higher degrees of characterization of focal pancreatic lesions than the conventional ADC does.

Diffusion-weighted MR imaging of the normal pancreas: reproducibility and variations of apparent diffusion coefficient measurement at 1.5- and 3.0-Tesla

PURPOSE

To evaluate reproducibility and variations in apparent diffusion coefficient (ADC) measurement in normal pancreatic parenchyma at 1.5- and 3.0-Tesla and determine if differences may exist between the four pancreatic segments.

MATERIALS AND METHODS

Diffusion-weighted MR imaging of the pancreas was performed at 1.5-Tesla in 20 patients and at 3.0-Tesla in other 20 patients strictly matched for gender and age using the same b values (0, 400 and 800s/mm(2)). Two independent observers placed regions of interest within the four pancreatic segments to measure ADC at both fields. Intra- and inter-observer agreement in ADC measurement was assessed using Bland-Altman analysis and comparison between ADC values obtained at both fields using non-parametrical tests.

RESULTS

There were no significant differences in ADC between repeated measurements and between ADC obtained at 1.5-Tesla and those at 3.0-Tesla. The 95% limits of intra-observer agreement between ADC were 2.3%-22.7% at 1.5-Tesla and 1%-24.2% at 3.0-Tesla and those for inter-observer agreement between 1.9%-14% at 1.5-Tesla and 8%-25% at 3.0-Tesla. ADC values were similar in all pancreatic segments at 3.0-T whereas the tail had lower ADC at 1.5-Tesla.

CONCLUSION

ADC measurement conveys high degrees of intra- and inter-observer reproducibility. ADC have homogeneous distribution among the four pancreatic segments at 3.0-Tesla.

Differentiation between pelvic abscesses and pelvic tumors with diffusion-weighted MR imaging: a preliminary study

PURPOSE

Use diffusion-weighted magnetic resonance imaging (MRI) in differentiating pelvic abscess from pelvic cystic tumor.

MATERIALS AND METHODS

Patients with pelvic abscess (n=23) or pelvic cystic tumor (n=15) who underwent diffusion-weighted MRI were reviewed.

RESULTS

Pelvic abscesses showed hyperintensity on diffusion-weighted MRI and hypointensity on apparent diffusion coefficient (ADC) map. The mean ADC values of fluid in pelvic abscess and pelvic tumors were 0.73 ± 0.15 × 10(-3) and 2.27 ± 0.45 × 10(-3) mm(2)/s, respectively. Pelvic abscesses had significantly lower ADC values than pelvic cystic tumors (P<.001).

CONCLUSION

Diffusion-weighted MRI provides a noncontrast method for interpreting pelvic cystic lesions.

Diffusion-weighted MRI of focal cystic pancreatic lesions at 3.0-Tesla: preliminary results

PURPOSE

To determine the utility of 3.0-Tesla diffusion-weighted (DW) magnetic resonance imaging (MRI) for focal cystic pancreatic lesion (FCPL) characterization.

MATERIALS AND METHODS

55 FCPL (34 IPMN, 5 serous cystadenoma, and 16 inflammatory) were evaluated. Two radiologists reviewed in consensus DW-MRI images. Reference standard was obtained from patient history, cytological and histopathology data, FCPL fluid analysis, and follow-up imaging results. Signal intensity (SI) and apparent diffusion coefficient values (ADC) of FCPL and normal pancreas were measured. FCPL-to-pancreas SI and ADC ratios were also calculated.

RESULTS

Qualitatively, 11 of 21 non-mucinous vs. 4 of 34 mucinous lesions appeared hyperintense at b value of 1,000 s/mm(2) (P = 0.02). Three FCPL demonstrated restricted diffusion: all inflammatory. Significant differences in mean ADC between neoplastic vs. non-neoplastic (P = 0.009), and mucinous vs. non-mucinous (P = 0.013) lesions were demonstrated. FCPL-to-pancreas ADC and SI ratios demonstrated significant differences between neoplastic vs. non-neoplastic lesions [ADC, (P = 0.019); SI for b values 750 (P = 0.010) and 1,000 s/mm(2) (P = 0.017)] and mucinous vs. non-mucinous lesions [ADC (P = 0.018); SI for b values 750 (P = 0.013) and 1,000 s/mm(2) (P = 0.015)].

CONCLUSION

Although mean ADC values and FCPL-to-pancreas SI and ADC ratios may be helpful in differentiating FCPL, characterization of individual FCPL by means of 3.0-Tesla DW-MRI appears limited.