Added value of breathhold diffusion-weighted MRI in detection of small hepatocellular carcinoma lesions compared with dynamic contrast-enhanced MRI alone using receiver operating characteristic curve analysis

Small hypervascular hepatocellular carcinomas: value of diffusion-weighted imaging compared with "washout" appearance on dynamic MRI

OBJECTIVE

To compare the value of diffusion-weighted MRI (DWI) with the venous "washout" appearance during dynamic MRI for the assessment of small arterial hypervascular lesions in cirrhotic liver.

METHODS

After exclusion of benign hypervascular lesions, including haemangiomas and subcapsular non-tumorous arterioportal shunts, indicated by typical imaging features, a total of 109 small arterial hypervascular lesions (0.5-3.0 cm in the longest diameter) in 65 patients with cirrhosis who underwent gadopentetate dimeglumine-enhanced dynamic MRI and DWI (b=50, 400, 800 s mm(-2)) at 1.5 T during a 16-month period were retrospectively analysed to determine the presence of venous washout during dynamic imaging or sustained hyperintensity upon increasing the b factor size on DWI.

RESULTS

Among the 99 hypervascular hepatocellular carcinomas (HCCs), sustained hyperintensity on DWI (92/99, 93%) was more prevalent than the washout appearance (72/99, 72%) on dynamic MRI (p<0.001). Depending on the lesion size, subcentimetre-sized HCCs had a significantly lower prevalence of venous washout (13/30, 43%) than the sustained hyperintensity on DWI (27/30, 90%) (p=0.001). In all 10 hypervascular benign conditions, there was no venous washout on dynamic MRI and no sustained hyperintensity on DWI. Sensitivity and specificity for diagnosis of hypervascular HCCs were 92.9% and 100% in DWI and 72% and 100% in dynamic MRI, respectively.

CONCLUSION

Compared with the venous washout during dynamic imaging, DWI provides more reliable information in the MRI assessment of small hypervascular HCCs, distinguishing them from atypical hypervascular benign or pseudolesions. DWI could complement the early diagnosis of small hypervascular HCCs that do not display venous washout during dynamic imaging.

Differentiation of early hepatocellular carcinoma from benign hepatocellular nodules on gadoxetic acid-enhanced MRI

OBJECTIVE

To test new diagnostic criteria for the discrimination of early hepatocellular carcinoma (HCC) from benign hepatocellular nodules on gadoxetic acid-enhanced MRI (Gd-EOB-MRI).

METHODS

We retrospectively analysed 34 patients with 29 surgically diagnosed early HCCs and 31 surgically diagnosed benign hepatocellular nodules. Two radiologists reviewed Gd-EOB-MRI, including diffusion-weighted imaging (DWI), and the signal intensity at each sequence, presence of arterial enhancement and washout were recorded. We composed new diagnostic criteria based on the lesion size and MRI findings, and then the diagnostic performance was compared with that of conventional imaging criteria with logistic regression and a generalised estimating equation method.

RESULTS

A size cut-off value (≥1.5 cm diameter) and MRI findings of T(1) hypointensity, T(2) hyperintensity, DWI hyperintensity on both low and high b-value images (b=50 and 800 s mm(-2), respectively), arterial enhancement, late washout and hepatobiliary hypointensity were selected as the diagnostic criteria. When lesions were considered malignant if they satisfied three or more of the above criteria, the sensitivity was significantly higher than when making a diagnosis based on arterial enhancement and washout alone (58.6% vs 13.8%, respectively; p=0.0002), while the specificity was 100.0% for both criteria.

CONCLUSION

Our new diagnostic criteria on Gd-EOB-MRI may help to improve the discrimination of early HCC from benign hepatocellular nodules.

MRI of Focal Liver Lesions

Magnetic resonance imaging, MRI has more advantages than ultrasound, computed tomography, CT, positron emission tomography, PET, or any other imaging modality in diagnosing focal hepatic masses. With a combination of basic T1 and T2 weighted sequences, diffusion weighted imaging, DWI, and hepatobiliary gadolinium contrast agents, that is gadobenate dimeglumine (Gd-BOPTA) and gadoxetic acid (Gd-EOB), most liver lesions can be adequately diagnosed. Benign lesions, as cyst, hemangioma, focal nodular hyperplasia, FNH or adenoma, can be distinguished from malignant lesions. In a non-cirrhotic liver, the most common malignant lesions are metastases which may be hypovascular or hypervascular. In the cirrhotic liver hepatocellular carcinoma, HCC, is of considerable importance. Besides, intrahepatic cholangiocarcinoma and other less common malignancies has to be assessed. In this review, the techniques and typical MRI features are presented as well as the new algorithm issued by American Association for the Study of the Liver Diseases (AASLD).

Histological grade of differentiation of hepatocellular carcinoma: comparison of the efficacy of diffusion-weighted MRI with T2-weighted imaging and angiography-assisted CT

INTRODUCTION

The purpose of this study is to determine the usefulness of diffusion-weighted imaging (DWI) for evaluating the histological grade of differentiation of hepatocellular carcinoma (HCC) compared with T2-weighted imaging (T2WI) and tumour haemodynamics.

METHODS

We retrospectively evaluated 32 patients with 42 pathologically confirmed HCC nodules. These patients underwent MRI, CT during arterial portography and CT hepatic arteriography. We evaluated the relationship between the histological grade of differentiation and the apparent diffusion coefficient (ADC) values, conspicuity of tumour on DWI, DWI and T2WI contrast-to-noise (C/N) ratios and tumour haemodynamics.

RESULTS

There was no correlation between the histological grade of differentiation and the ADC values. The DWI C/N ratio was significantly different among all histological grades, but the T2WI C/N ratio was not. Tumour conspicuity on DWI correlated well with the histological grade of differentiation, but tumour haemodynamics only partially correlated with the histological grade of differentiation.

CONCLUSION

DWI was useful for evaluating the histological grade of differentiation of HCC.

Additional diffusion-weighted imaging in the detection of new, very small hepatocellular carcinoma lesions after interventional therapy compared with conventional 3 T MRI alone

AIM

To evaluate the added value of diffusion-weighted imaging (DWI) combined with conventional magnetic resonance imaging (MRI) in the detection of new, very small hepatocellular carcinoma lesions (≤1 cm) in patients with hepatocellular carcinoma following interventional therapy compared to conventional MRI alone.

MATERIALS AND METHODS

After interventional therapy, 45 patients with hepatocellular carcinoma underwent conventional MRI and DWI with a b-value of 0 and 700 s/mm(2). Twenty-one new, small hepatocellular carcinoma lesions were confirmed in 16 patients at follow-up MRI. Two observers independently retrospectively analysed the two imaging sets in random order. The diagnostic performance using each imaging set was evaluated by received operating characteristic curve analysis.

RESULTS

Twenty-one new, very small hepatocellular carcinoma lesions found in 16 patients was confirmed as the final result. The area under the receiver operating characteristic curve of the DWI/conventional MRI combination (observer 1, 0.952; observer 2, 0.976) and conventional MRI images alone (observer 1, 0.905; observer 2, 0.905) were statistically significant. The kappa value of the DWI/conventional MRI combination was 0.884, and that of conventional MRI was 0.722. Among the 21 lesions, 100% (21/21) of the lesions were both recognized by two independent reviewers on DWI, while only 76% (16/21) and 71% (15/21) of the lesions were regarded as very small hepatocellular carcinomas on conventional MRI.

CONCLUSION

Due to the higher detection rate of new subcentimetre lesions in hepatocellular carcinoma patients following interventional therapy, DWI could be considered complementary to conventional MRI in the diagnosis of hepatocellular carcinoma.

Applications of diffusion-weighted magnetic resonance imaging in renal cell carcinoma

Diffusion-weighted MRI (DW-MRI) has received more attention recently, especially from uroradiologists, owing to its role in the characterization of renal lesions. Moreover, the apparent diffusion coefficient (ADC), a value calculated based on DW-MRIs, has been used to analyze renal lesions quantitatively. However, many factors influence the accuracy of the ADC value calculation during the DW-MRI procedure. In addition, it is of great interest whether DW-MRI is superior to more conventional dynamic contrast-enhanced (DCE)-MRI for the characterization of renal lesions, or whether DW-MRI combined with DCE-MRI may provide more valuable information. Here we review state-of-the-art DW-MRI for the evaluation of renal cell carcinomas, discuss factors that influence the calculation of ADC maps, examine the impact of field strength on ADC values and, finally, compare DW-MRI and DCE-MRI for imaging renal lesions.

Can the patient with cirrhosis be imaged for hepatocellular carcinoma without gadolinium?: Comparison of combined T2-weighted, T2*-weighted, and diffusion-weighted MRI with gadolinium-enhanced MRI using liver explantation standard

PURPOSE

This study aimed to evaluate a non-gadolinium-enhanced magnetic resonance imaging (MRI) protocol including T2-weighted, T2*-weighted, and diffusion-weighted MRI sequences for identifying hepatocellular carcinoma (HCC) with liver explantation as the reference standard. Also, a stand-alone pre- and dynamic post-gadolinium-enhanced liver MRI data set was interpreted from the available patient data for relative comparison purposes.

MATERIALS AND METHODS

A retrospective review identified 37 appropriately selected liver transplant patients who had had preoperative MRI. Two data sets were created from the MRI studies: (1) non-gadolinium-enhanced (including T2-weighted, T2*-weighted, and diffusion-weighted sequences) and (2) pre- and dynamic post-gadolinium-enhanced (3-dimensional T1-weighted gradient recalled echo) and were presented to 2 independent, blinded observers. A separate blinded observer assessed the pathologic results from liver explantation to establish the reference standard.

RESULTS

On explant pathology, 21 of 37 patients had 31 HCC (mean [SD] largest diameter, 19 [9] cm; range, 7-40 mm). Per-lesion sensitivity of non-gadolinium-enhanced MRI for identifying HCC was 52% (reader 1) and 55% (reader 2), and specificity was 90% (reader 1) and 88% (reader 2). Per-lesion sensitivity of the stand-alone pre- and dynamic post-gadolinium-enhanced MRI was 84% (reader 1) and 81% (reader 2), and specificity was 62% (reader 1) and 65% (reader 2).

CONCLUSIONS

Non-gadolinium-enhanced MRI had a moderate sensitivity for HCC but had a high specificity. Although non-gadolinium-enhanced MRI cannot be recommended as a primary imaging approach for HCC, the results demonstrate the contribution of non-gadolinium-enhanced sequences to imaging of HCC. A non-gadolinium-enhanced MRI protocol may have a diagnostic value when gadolinium cannot be administered.

Gadoxetic acid-enhanced hepatobiliary phase MRI and high-b-value diffusion-weighted imaging to distinguish well-differentiated hepatocellular carcinomas from benign nodules in patients with chronic liver disease

OBJECTIVE

The purpose of this article is to evaluate the value of gadoxetic acid-enhanced hepatobiliary phase imaging and high-b-value diffusion-weighted imaging (DWI) for distinguishing well-differentiated hepatocellular carcinomas (HCCs) from benign hepatocellular nodules in patients with chronic liver disease using 3-T MRI.

MATERIALS AND METHODS

Forty-five patients with 46 well-differentiated HCCs (mean, 2.3 cm) and 21 patients with 24 benign hepatocellular nodules (five large regenerative nodules and 19 dysplastic nodules; mean, 1.8 cm) were included in this study. Diagnosis of well-differentiated HCCs and benign hepatocellular nodules was made histopathologically by percutaneous biopsy (n = 12 and n = 11, respectively) or surgical resection (n = 34 and n = 13, respectively). Gadoxetic acid-enhanced MRI was performed for all patients, and DWI (b values of 0 and 800 s/mm(2)) was performed for 31 well-differentiated HCCs and 11 benign hepatocellular nodules. Two radiologists performed a consensus review of the MRI scans for signal intensity compared with that of the surrounding liver parenchyma on hepatobiliary phase images and DWI (b value, 800 s/mm(2)) for qualitative analysis. The contrast-to-noise ratio (CNR) and relative contrast enhancement of lesions on hepatobiliary phase images and the apparent diffusion coefficient (ADC) values were assessed for quantitative analysis.

RESULTS

In the qualitative analysis, 39 well-differentiated HCCs (85%) and 14 benign hepatocellular nodules (58%) were hypointense on hepatobiliary phase images, and seven well-differentiated HCCs (15%) and 10 benign hepatocellular nodules (42%) were iso- or hyperintense (p = 0.04). Twenty-five well-differentiated HCCs (81%) and three benign hepatocellular nodules (27%) were hyperintense on DWI, with b value of 800 s/mm(2), and six well-differentiated HCCs (19%) and eight benign hepatocellular nodules (73%) were iso- or hypointense (p = 0.01). When lesion hypointensity on hepatobiliary phase images or hyperintensity on DWI were considered signs of HCC in cirrhotic liver, our results yielded sensitivities of 85% and 81% and specificities of 42% and 73%, respectively. In the quantitative analysis, the mean (± SD) relative contrast enhancement ratio of the well-differentiated HCCs (0.76 ± 2.30) was significantly higher than that of benign hepatocellular nodules (0.25 ± 0.97) (p = 0.02). The lesion-to-liver CNRs and the mean ADC values were not significantly different between the two groups (p > 0.05).

CONCLUSION

Hypointensity on gadoxetic acid-enhanced hepatobiliary phase images and hyperintensity on high-b-value DWI to surrounding liver parenchyma suggest well-differentiated HCCs rather than benign hepatocellular nodules in chronic liver disease.

Magnetic resonance imaging of the chest: current and new applications, with an emphasis on pulmonology

The objective of the present review study was to present the principal applications of magnetic resonance imaging (MRI) of the chest, including the description of new techniques. Over the past decade, this method has evolved considerably because of the development of new equipment, including the simultaneous interconnection of phased-array multiple radiofrequency receiver coils and remote control of the table movement, in addition to faster techniques of image acquisition, such as parallel imaging and partial Fourier acquisitions, as well as the introduction of new contrast agents. All of these advances have allowed MRI to gain ground in the study of various pathologies of the chest, including lung diseases. Currently, MRI is considered the modality of choice for the evaluation of lesions in the mediastinum and in the chest wall, as well as of superior sulcus tumors. However, it can also facilitate the diagnosis of lung, pleural, and cardiac diseases, as well as of those related to the pulmonary vasculature. Pulmonary MRI angiography can be used in order to evaluate various pulmonary vascular diseases, and it has played an ever greater role in the study of thromboembolism. Because cardiac MRI allows morphological and functional assessment in the same test, it has also become part of the clinical routine in the evaluation of various cardiac diseases. Finally, the role of MRI has been extended to the identification and characterization of pulmonary nodules, the evaluation of airway diseases, and the characterization of pleural effusion.

Diffusion-weighted MR imaging in gynecologic cancers

Diffusion-weighted imaging (DWI) reflects changes in proton mobility caused by pathological alterations of tissue cellularity, cellular membrane integrity, extracellular space perfusion, and fluid viscosity. Functional imaging is becoming increasingly important in the evaluation of cancer patients because of the limitations of morphologic imaging. DWI is being applied to the detection and characterization of tumors and the evaluation of treatment response in patients with cancer. The advantages of DWI include its cost-effectiveness and brevity of execution, its complete noninvasiveness, its lack of ionizing radiation, and the fact that it does not require injection of contrast material, thus enabling its use in patients with renal dysfunction. In this article, we describe the clinical application of DWI to gynecological disorders and its diagnostic efficacy therein.

3 T MRI of hepatocellular carcinomas in patients with cirrhosis: does T2-weighted imaging provide added value?

AIM

To assess whether T2-weighted imaging (T2WI) provides any added value for the detection of hepatocellular carcinoma (HCC) in patients with cirrhosis, especially for lesions smaller than 2 cm.

MATERIALS AND METHODS

Sixty-five patients with cirrhosis underwent liver 3 T MRI. Images were qualitatively analysed independently by two observers in two separate sessions, including a dynamic enhanced session and a combination of dynamic and T2WI. The diagnostic accuracy was evaluated using the alternating free-response receiver operating characteristic. Sensitivity and positive predictive values were calculated for all HCCs and for the subgroup of HCCs that were smaller than 2 cm. Additionally, artefacts on T2WI were evaluated by two observers in consensus.

RESULTS

Ninety HCCs (>2 cm n = 36; ≤2 cm n = 54) were detected in 46 patients. For all HCCs and for lesions smaller than 2 cm, the sensitivities were significantly higher for the combined session than the dynamic session alone (p < 0.05). Conversely, for the Az and positive predictive values, there was no significant difference between the two sessions. For smaller HCC, 9% (5/54) and 7% (4/54) of the 54 HCCs were correctly interpreted by observers 1 and 2, respectively, only when T2WI was included. Three false-positive lesions (≤2 cm) were correctly diagnosed by one of the observers after combining T2WI. Conspicuity of only one large HCC was severely reduced by the artefacts from massive ascites.

CONCLUSION

At 3 T liver imaging, combining with T2WI can improve the sensitivity of detection of HCC compared with dynamic MRI alone by increasing observer confidence, especially for lesions smaller than 2 cm. Additionally, T2 image quality was not significantly affected by artefacts.

Quantitative MR imaging: physical principles and sequence design in abdominal imaging

Quantitative magnetic resonance (MR) imaging seeks to quantify fundamental biologic and MR-inducible tissue properties, in contrast to the routine application of MR imaging in the clinic, in which differences in MR parameters are used to generate contrast for subsequent subjective image analysis. Fundamental parameters that are commonly quantified by using MR imaging include proton density, diffusion, T1 relaxation, T2 and T2* relaxation, and magnetization transfer. Applications of these MR imaging-quantifiable parameters to abdominal imaging include oncologic imaging, evaluation of diffuse liver disease, and assessment of splenic, renal, and pancreatic disease. An understanding of the inherent physical principles underlying the basic quantitative parameters as well as the commonly used pulse sequences requisite to their derivation is critical, as this field is rapidly growing and its use will likely continue to expand in the clinic. The full potential of quantitative MR imaging applied to abdominal imaging has yet to be realized, but the myriad applications reported to date will undoubtedly continue to grow.

Hypervascular hepatocellular carcinoma in the cirrhotic liver: diffusion-weighted imaging versus superparamagnetic iron oxide-enhanced MRI

PURPOSE

The purpose of the study was to validate diffusion-weighted imaging (DWI) in the assessment of hypervascular hepatocellular carcinoma (HCC) compared with superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance imaging (MRI) in the cirrhotic liver.

MATERIAL AND METHODS

Forty-six consecutive patients with 106 hypervascular focal lesions in the cirrhotic liver who underwent DWI using three b factors and gadopentetate dimeglumine-enhanced dynamic MRI followed by SPIO-enhanced MRI were enrolled. Two independent radiologists evaluated two separated image sets (SPIO set, dynamic MRI and SPIO-enhanced T2*-weighted images; DWI set, DWI and dynamic MRI) and assigned confidence levels for diagnosis of HCC using a five-point scale for each lesion. Area under the receiver operating characteristic curve (A(z)) was calculated for each image set.

RESULTS

The A(z) value of the DWI set was larger than the SPIO set by both readers (reader 1, 0.936 vs. 0.900, P=.050; reader 2, 0.938 vs. 0.905, P=.110). For the sensitivity (reader 1, 93.1% vs. 86.2%, P=.146; reader 2, 95.4% vs. 88.5%, P=.070) and specificity (reader 1, 89.5% vs. 73.7%, P=.250; reader 2, 79.0% vs. 73.7%, P=1.000) of HCC diagnosis, DWI sets were superior to SPIO sets without statistically significant differences.

CONCLUSION

For assessment of hypervascular HCC, DWI in combination with dynamic MRI provides comparable or slightly better information compared with the combination of dynamic and SPIO-enhanced MRI.

FDG PET for giant cavernous hemangioma: important clue to differentiate from a malignant vascular tumor in the liver

Giant cavernous hemangioma of the liver sometimes has a very inhomogeneous appearance with intratumoral degeneration on computed tomography or magnetic resonance imaging, and may mimic a malignant hepatic tumor, including angiosarcoma. There are many reports about F-18 fluorodeoxyglucose (FDG) uptake of angiosarcoma; however, knowledge regarding positron emission tomography findings with FDG for giant hepatic cavernous hemangioma is still limited. We herein present 2 cases of giant hepatic cavernous hemangioma in which low FDG uptake was considered helpful to differentiate from malignant hepatic tumor.

[Radiological diagnosis of hepatocellular carcinoma in 2010]

The aim of diagnosis imaging is to detect hepatocellular carcinoma at an early stage, when a curative treatment is available. Biopsy is no longer required prior to treatment, and diagnosis of hepatocellular carcinoma is heavily dependent of imaging characteristics. Therefore, the purpose of this article is to describe the typical features of small (<20mm) and larger hepatocellular carcinomas with noninvasive diagnostic criteria, including ultrasound, computed tomography and MRI. Advances in these imaging modalities have greatly improved the detection of small hepatic nodules on liver cirrhosis, including the different steps of carcinogenesis, from regenerative to dysplastic nodules, and we emphasize the difficulties of radiological differentiation of precancerous lesions and small hepatocellular carcinomas.

APASL and AASLD Consensus Guidelines on Imaging Diagnosis of Hepatocellular Carcinoma: A Review

Consensus guidelines for radiological diagnosis of hepatocellular carcinoma (HCC) have been drafted by several large international working groups. This article reviews the similarities and differences between the most recent guidelines proposed by the American Association for Study of Liver Diseases and the Asian Pacific Association for the Study of the Liver. Current evidence for the various imaging modalities for diagnosis of HCC and their relevance to the consensus guidelines are reviewed.

Effect of Gd-EOB-DTPA on T2-weighted and diffusion-weighted images for the diagnosis of hepatocellular carcinoma

PURPOSE

To evaluate the effect of gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) on T2-weighted imaging (T2WI) and diffusion-weighted imaging (DWI) for the diagnosis of hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

The phantom signal intensity was measured. We also evaluated 72 patients including 30 patients with HCC. T2WI and DWI were obtained before and then 4 and 20 min after injecting the contrast medium. The signal to noise ratio (SNR), contrast to noise ratio (CNR), and apparent diffusion coefficient (ADC) were calculated in the tumor and liver parenchyma.

RESULTS

The phantom signal intensity increased on T2WI at a concentration of contrast medium less than 0.2 mmol/L but decreased when the concentration exceeded 0.4 mmol/L. SNR of the liver parenchyma on T2WI was significantly different between before and 4 min after injecting the contrast medium, while there were no significant differences between before and 4 and 20 min after injection. On T2WI, SNR, and CNR of HCC showed no significant differences at any time. SNR, CNR, and ADC of the liver parenchyma and tumor on DWI also showed no significant differences at any time.

CONCLUSION

It is acceptable to perform T2WI and DWI after injection of Gd-EOB-DTPA for the diagnosis of HCC.

Contribution of diffusion-weighted magnetic resonance imaging in the characterization of hepatocellular carcinomas and dysplastic nodules in cirrhotic liver

OBJECTIVES

To evaluate the diagnostic value of diffusion-weighted magnetic resonance imaging (DWI) for the characterization of hepatocellular carcinoma (HCC) and dysplastic nodule (DN) in cirrhotic liver, compared with contrast material-enhanced magnetic resonance imaging (CE-MRI).

METHODS

A total of 54 patients with 40 HCC and 19 DN lesions were included in our study, and all lesions were histopathologically confirmed. All lesions were evaluated with CE-MRI, and breath-hold DWI was performed with b = 500 s/mm. The signal intensity (SI) of the lesions were classified as low, iso-, slightly high, and strongly high SI compared with that of the surrounding liver parenchyma on DWI for qualitative assessment. Apparent diffusion coefficients (ADCs) and lesion-to-liver ADC ratio of HCCs and DNs were measured and compared by using the Mann-Whitney U test. The lesions were characterized with the use of CE-MRI criteria and DWI, respectively. Receiver operating characteristic analysis was performed to assess the diagnostic value of DWI, CE-MRI, and these techniques combined in the differentiation of HCCs from DNs.

RESULTS

In the qualitative analysis, among 40 HCCs, 39 (97.5%) had slightly high or strongly high SI on DWI, and 1 (2.5%) had low SI; only 4 (21.5%) of 19 DNs had slightly high SI, and 15 (78.95%) had iso-SI or low SI. The mean (SD) ADC and ADC ratio for HCCs (1.28 x 10 [0.25] mm/s and 0.88 [0.15], respectively) were significantly lower (P < 0.01 and P < 0.001, respectively) than those for DNs (1.53 x 10 [0.33] mm/s and 1.00 [0.08], respectively). The area, Az, under the receiver operating characteristic curve for the SI feature, the ADC ratio, and the ADCs based on the diagnosis of HCC versus DN were 0.88, 0.81, and 0.68, respectively. When the slightly high SI of lesion with a cutoff ADC ratio less than 0.92 was applied as a criterion, the Az, the sensitivity, the specificity, and the accuracy of DWI for the diagnosis of HCC versus DN were 0.81, 67.50%, 94.74%, and 76.27%, respectively. The corresponding Az, sensitivity, specificity, and accuracy of CE-MRI were 0.70, 82.50%, 57.89%, and 74.58%, respectively. Combined DWI plus CE-MRI had 0.91 Az, 97.50% sensitivity, and 93.22% accuracy, which increased significantly compared with those of CE-MRI alone.

CONCLUSIONS

Diffusion-weighted MRI can provide additional information to differentiate HCC from DN. Combined with CE-MRI, DWI allows improved characterization of HCC versus DN in cirrhotic liver.

Detection of hepatocellular carcinoma (HCC) using super paramagnetic iron oxide (SPIO)-enhanced MRI: Added value of diffusion-weighted imaging (DWI)

PURPOSE

To evaluate whether diffusion-weighted imaging (DWI) improves the detection of hepatocellular carcinoma (HCC) on super paramagnetic iron oxide (SPIO)-enhanced MRI.

MATERIALS AND METHODS

This retrospective study group consisted of 30 patients with 50 HCC nodules who underwent MRI at 1.5 Tesla. Two combined MR sequence sets were compared for detecting HCC: SPIO-enhanced MRI (axial T2-weighted fast spin-echo (FSE) and T1-/T2*-weighted fast field echo (FFE) scanned before and after administration of ferucarbotran) and SPIO-enhanced MRI + DWI (SPIO-enhanced MRI with axial DWI scanned before and after administration of ferucarbotran). Three blinded readers independently reviewed for the presence of HCC on a segment-by-segment basis using a four-point confidence scale. The performance of the two combined MR sequence sets was evaluated using receiver operating characteristic (ROC) analysis.

RESULTS

The average area under the ROC curve (Az) of the three readers for the SPIO-enhanced MRI + DWI set (0.870 +/- 0.046) was significantly higher that that for the SPIO-enhanced MRI set (0.820 +/- 0.055) (P = .025). The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for detection of HCC were 66.0%, 98.0%, 90.0%, and 91.4%, respectively, for the SPIO-enhanced MRI set, and 70.0%, 98.6%, 92.9%, and 92.4%, respectively, for the SPIO-enhanced MRI + DWI set.

CONCLUSION

The SPIO-enhanced MRI + DWI set outperformed the SPIO-enhanced MRI set for depicting HCC.

Diffusion and perfusion imaging of the liver

MRI of the liver is an important tool for the detection and characterization of focal liver lesions, for assessment of tumor response to treatment, and for the evaluation of diffuse liver disease. With recent advances in technology, functional MRI methods such as diffusion-weighted (DW) and perfusion-weighted (PW)-MRI are increasingly used in the abdomen with promising results, particularly in the evaluation of diffuse and focal liver diseases. In this review, we will discuss background, technical considerations, acquisition, applications, limitations and future applications of DW-MRI and PW-MRI applied in evaluation of diffuse and focal liver diseases.

Diffusion weighted imaging in the liver

Diffusion weighted magnetic resonance imaging (DWI) is an imaging technique which provides tissue contrast by the measurement of diffusion properties of water molecules within tissues. Diffusion is expressed in an apparent diffusion coefficient (ADC), which reflects the diffusion properties unique to each type of tissue. DWI has been originally used in neuroradiology. More recently, DWI has increasingly been used in addition to conventional unenhanced and enhanced magnetic resonance imaging (MRI) in other parts of the body. The reason for this delay was a number of technical problems inherent to the technique, making DWI very sensitive to artifacts, which had to be overcome. With assessment of ADC values, DWI proved to be helpful in characterization of focal liver lesions. However, DWI should always be used in conjunction to conventional MRI since there is considerable overlap between ADC values of benign and malignant lesions. DWI is useful in the detection of hepatocellular carcinoma in the cirrhotic liver and detection of liver metastases in oncological patients. In addition, DWI is a promising tool in the prediction of tumor responsiveness to chemotherapy and the follow-up of oncological patients after treatment, as DWI may be capable of detecting recurrent disease earlier than conventional imaging. This review focuses on the most common applications of DWI in the liver.

Diffusion-weighted magnetic resonance imaging of the liver using tracking only navigator echo: feasibility study

PURPOSE

To introduce and assess the TRacking Only Navigator echo (TRON) technique for diffusion-weighted magnetic resonance imaging (DWI) of the liver.

SUBJECTS AND METHODS

A total of 10 volunteers underwent TRON, respiratory triggered (RT), and free breathing (FB) DWI of the liver. Scan times of TRON and RT DWI were measured, and image sharpness in TRON, RT, and FB DWI was assessed and compared using nonparametric tests. Furthermore, 14 patients with liver metastasis who had undergone TRON and RT DWI of the liver were retrospectively assessed. Relative contrast ratios (RCRs) and apparent diffusion coefficients (ADCs) of the largest hepatic metastasis in TRON and RT DWI were measured. RCRs were compared using a parametric test and agreement in ADCs was assessed using the Bland-Altman method.

RESULTS

In the volunteers, mean scan times of TRON and RT relative to FB DWI were 110% to 112% and 261% to 290%, respectively. On axial images, there were no significant differences in images sharpness among TRON, RT, and FB DWI, but on coronal images image sharpness in TRON was nearly always significantly better (P < 0.05) than in RT and FB DWI. In the patients, mean RCRs between TRON and RT DWI were not significantly different (P = 0.9091). Mean difference in ADC +/- limits of agreement (in 10 mm/s) between TRON and RT DWI was -0.16 +/- 0.79.

CONCLUSION

TRON offers sharp diffusion-weighted images of the liver using an efficient scan time, making it an excellent alternative to RT and FB DWI. The moderate to poor agreement in ADCs of liver metastases between TRON and RT DWI requires further investigation.

Diffusion-weighted MR imaging of the liver at 3.0 Tesla using TRacking Only Navigator echo (TRON): a feasibility study

PURPOSE

To assess the feasibility of TRacking Only Navigator echo (TRON) for diffusion-weighted magnetic resonance imaging (DWI) of the liver at 3.0T.

MATERIALS AND METHODS

Ten volunteers underwent TRON, respiratory triggered, and free breathing DWI of the liver at 3.0 Tesla (T). Scan times were measured. Image sharpness, degree of stair-step and stripe artifacts for the three methods were assessed by two observers.

RESULTS

Mean scan times of TRON and respiratory triggered DWI relative to free breathing DWI were 34% and 145% longer respectively. In four of eight comparisons (two observers, two b-values, two slice orientations), TRON DWI image sharpness was significantly better than free breathing DWI, but inferior to respiratory triggered DWI. In two of four comparisons (two observers, two b-values), degree of stair-step artifacts in TRON DWI was significantly lower than in respiratory triggered DWI. Degree of stripe artifacts between the three methods was not significantly different.

CONCLUSION

DWI of the liver at 3.0T using TRON is feasible. Image sharpness in TRON DWI is superior to that in free breathing DWI. Although image sharpness of respiratory triggered DWI is still better, TRON DWI requires less scan time and reduces stair-step artifacts.