Characterization of focal hepatic lesions with ferumoxides-enhanced T2-weighted MR imaging

Perspective of Fe3O4 Nanoparticles Role in Biomedical Applications

In recent years, although many review articles have been presented about bioapplications of magnetic nanoparticles by some research groups with different expertise such as chemistry, biology, medicine, pharmacology, and materials science and engineering, the majority of these reviews are insufficiently comprehensive in all related topics like magnetic aspects of process. In the current review, it is attempted to carry out the inclusive surveys on importance of magnetic nanoparticles and especially magnetite ones and their required conditions for appropriate performance in bioapplications. The main attentions of this paper are focused on magnetic features which are less considered. Accordingly, the review contains essential magnetic properties and their measurement methods, synthesis techniques, surface modification processes, and applications of magnetic nanoparticles.

Superparamagnetic iron oxide-enhanced magnetic resonance imaging for focal hepatic lesions: Systematic review and meta-analysis

AIM: To evaluate the performance of superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance imaging (MRI) in the detection and characterization of focal hepatic lesions (FHLs).

METHODS: This meta-analysis compared relevant studies that were identified by searching PubMed, EMBASE, and the Cochrane Library databases for articles published between January 1988 and September 2014 and that met the following criteria: (1) SPIO-enhanced MRI was conducted to identify FHLs and data were sufficient for pooled analysis using Meta-DiSc 1.4; (2) hepatocellular carcinomas (HCCs) were differentiated from other FHLs; (3) well-differentiated HCCs (WD-HCCs) were contradistinguished from dysplastic nodules; and (4) WD-HCCs were compared with moderately and poorly differentiated HCCs (MD- and PD-HCCs, respectively).

RESULTS: The data obtained from 15 eligible studies yielded a sensitivity of 85% and a specificity of 78% for differentiating between HCCs and other FHLs. The sensitivity was unchanged and the specificity was increased to 87% when non-HCC malignancies were excluded. Comparative analyses between WD-HCCs and MD- and PD-HCCs from seven studies showed a sensitivity of 98% and a specificity of 50% for the diagnosis of MD- and PD-HCCs, and the area under the summary receiver operating characteristics (sROC) curve was 0.97. A comparison between WD-HCCs and dysplastic nodules revealed a sensitivity of 50% and a specificity of 92% for the diagnosis of WD-HCCs and the area under the sROC curve was 0.80.

CONCLUSION: SPIO-enhanced MRI is useful in differentiating between HCCs and other FHLs.

Can a decision-making model be justified in the management of hepatocellular adenoma?

During recent years, there was a great development in the area of hepatocellular adenomas (HCA), especially regarding the pathological subtype classification, radiological imaging and management during pregnancy. This review discusses the current knowledge about diagnosis and treatment modalities of HCA and proposes a decision-making model for HCA. A Medline search of studies relevant to epidemiology, histopathology, complications, imaging and management of HCA lesions was undertaken. References from identified articles were hand-searched for further relevant articles.

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.

Tumors of the liver and intrahepatic bile ducts: radiologic-pathologic correlation

Primary tumors of the liver can be classified pathologically based on their cell of origin into epithelial tumors, arising from hepatocytes or biliary epithelium, and nonepithelial tumors, including mesenchymal tumors and lymphoma. Characteristic findings on MR imaging can be seen in many cases. This article reviews the MR imaging appearance of these tumors with pathologic correlation.

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.

Improved characterization of focal liver lesions with liver-specific gadoxetic acid disodium-enhanced magnetic resonance imaging: a multicenter phase 3 clinical trial

OBJECTIVES

To evaluate the safety of gadoxetic acid disodium (Gd-EOB-DTPA) magnetic resonance imaging (MRI) and its efficacy in characterizing liver lesions.

METHODS

Lesion characterization and classification using combined (unenhanced and Gd-EOB-DTPA-enhanced) MRI were compared with those using unenhanced MRI and contrast-enhanced spiral computed tomography (CT) using on-site clinical and off-site blinded evaluations for patients with focal liver lesions.

RESULTS

Gadoxetic acid disodium was well tolerated in this study. For the clinical evaluation, more lesions were correctly characterized using combined (unenhanced and Gd-EOB-DTPA-enhanced) MRI than using unenhanced MRI and spiral CT (96% vs 84% and 85%, respectively; P < or = 0.0008). For the blinded evaluation, more lesions were correctly characterized using combined MRI compared with using unenhanced MRI (61%-76% vs 48%-65%, respectively; P < or = 0.0012 for 2/3 readers); when compared with spiral CT, a similar proportion of lesions were correctly characterized.

CONCLUSIONS

Gadoxetic acid disodium-enhanced MRI is of clinical benefit relative to unenhanced MRI and spiral CT for a radiological diagnosis of liver lesions.

Percentage of signal intensity loss for characterisation of focal liver lesions in patients with chronic liver disease using ferucarbotran-enhanced MRI

The purpose of this study was to determine the percentage of signal intensity loss (PSIL) threshold for the characterisation of focal liver lesions among patients with chronic liver disease. 55 nodules in 49 patients with chronic liver disease who underwent ferucarbotran-enhanced MR studies were included. Among the 49 patients, 40 had liver cirrhosis and 9 had chronic hepatitis. 8 haemangiomas, 3 focal nodular hyperplasia, 9 dysplastic nodules and 12 well, 19 moderately and 4 poorly differentiated hepatocellular carcinomas (HCCs) were revealed. The PSIL, signal-to-noise ratio and contrast-to-noise ratio of each lesion type were calculated. The diagnostic performance of PSIL on ferucarbotran-enhanced T(2) weighted images (PSIL(T2WI)) and T(2) weighted fat-suppression images (PSIL(FS-T2WI)) that characterised hepatic tumours was compared with receiver operating characteristic (ROC) analysis. Using ROC analysis, the diagnostic performance of PSIL(FS-T2WI) was superior to that of PSIL(T2WI) (p = 0.01). The mean PSIL(FS-T2WI) of the benign lesions was significantly higher than that of HCC (p<0.001), and the mean PSIL(FS-T2WI) of well-differentiated HCC was significantly higher than that of moderately/poorly differentiated HCCs (p = 0.001). With a PSIL(FS-T2WI) threshold of 40% in lesions characterising ferucarbotran-enhanced FS-T2WI, the sensitivity, specificity, accuracy, positive predictive value and negative predictive value were 88.6%, 95%, 90.9%, 96.9% and 82.6%, respectively. In conclusion, with ferucarbotran-enhanced FS-T2WI, a PSIL(FS-T2WI) threshold of 40% for characterising focal liver nodules among patients with chronic liver disease is recommended. It is useful for distinguishing HCC from benign nodules.

Magnetic resonance imaging of the liver: New imaging strategies for evaluating focal liver lesions

The early detection of focal liver lesions, particularly those which are malignant, is of utmost importance. The resection of liver metastases of some malignancies (including colorectal cancer) has been shown to improve the survival of patients. Exact knowledge of the number, size, and regional distribution of liver metastases is essential to determine their resectability. Almost all focal liver lesions larger than 10 mm are demonstrated with current imaging techniques but the detection of smaller focal liver lesions is still relatively poor. One of the advantages of magnetic resonance imaging (MRI) of the liver is better soft tissue contrast (compared to other radiologic modalities), which allows better detection and characterization of the focal liver lesions in question. Developments in MRI hardware and software and the availability of novel MRI contrast agents have further improved the diagnostic yield of MRI in lesion detection and characterization. Although the primary modalities for liver imaging are ultrasound and computed tomography, recent studies have suggested that MRI is the most sensitive method for detecting small liver metastatic lesions, and MRI is now considered the pre-operative standard method for diagnosis. Two recent developments in MRI sequences for the upper abdomen comprise unenhanced diffusion-weighted imaging (DWI), and keyhole-based dynamic contrast-enhanced (DCE) MRI (4D THRIVE). DWI allows improved detection (b = 10 s/mm²) of small (< 10 mm) focal liver lesions in particular, and is useful as a road map sequence. Also, using higher b-values, the calculation of the apparent diffusion coefficient value, true diffusion coefficient, D, and the perfusion fraction, f, has been used for the characterization of focal liver lesions. DCE 4D THRIVE enables MRI of the liver with high temporal and spatial resolution and full liver coverage. 4D THRIVE improves evaluation of focal liver lesions, providing multiple arterial and venous phases, and allows the calculation of perfusion parameters using pharmacokinetic models. 4D THRIVE has potential benefits in terms of detection, characterization and staging of focal liver lesions and in monitoring therapy.

Focal liver lesions: detection and characterization at double-contrast liver MR Imaging with ferucarbotran and gadobutrol versus single-contrast liver MR imaging

PURPOSE

To retrospectively compare, in a multiobserver study, double-contrast-material (sequential administration of ferucarbotran and gadobutrol) magnetic resonance (MR) imaging with single-contrast-material ferucarbotran-enhanced and dynamic postferucarbotran gadobutrol-enhanced MR imaging for the detection and characterization of benign and malignant focal liver lesions.

MATERIALS AND METHODS

This study was institutional review board approved, and the requirement for informed patient consent was waived. Eighty-nine patients with a total of 128 focal liver lesions underwent double-contrast liver MR imaging (nonenhanced, ferucarbotran-enhanced, and dynamic postferucarbotran gadobutrol-enhanced MR imaging performed during one session). Four readers independently reviewed the data sets during three reading sessions focused on focal liver lesion detection and characterization: In session 1, the nonenhanced and dynamic postferucarbotran gadobutrol-enhanced images obtained at double-contrast MR imaging were analyzed. In session 2, the nonenhanced and ferucarbotran-enhanced images were analyzed. In session 3, all MR images were analyzed together. The diagnostic performance of each MR technique and each reader was evaluated by using receiver operating characteristic (ROC) analysis; differences between postferucarbotran gadobutrol-enhanced, ferucarbotran-enhanced, and double-contrast MR imaging were assessed at Wilcoxon signed rank testing; and interreader agreement was assessed at Cohen kappa analysis. Histopathologic confirmation or an unchanged clinical course or MR finding was the reference standard.

RESULTS

The four readers' detection of the benign and malignant lesions was not significantly different (P > or = .11) between the three MR techniques. The benign and malignant focal liver lesions were differentiated with significantly higher confidence (P < or = .01) on the double-contrast (area under ROC curve [A(z)] = 0.988) and ferucarbotran-enhanced (A(z) = 0.985) MR images than on the dynamic gadobutrol-enhanced images (A(z) = 0.963). Accuracy in the diagnosis of hepatocellular carcinoma (HCC) was highest (P = .02) and confidence in the final diagnosis of HCC (P = .001) or metastasis (P = .049) was significantly higher with double-contrast imaging.

CONCLUSION

In select cases, double-contrast MR imaging can improve diagnostic accuracy and increase confidence in characterizing focal liver lesions as HCC or metastasis.

Diagnosis and treatment of benign focal liver lesions

BACKGROUND

With the routine use of improved imaging modalities, more benign liver lesions are detected nowadays. An accurate characterization of these incidental lesions may be a challenge, and frequently a biopsy or even unnecessary surgery is being performed. However, these interventions are not always to the benefit of the patient.

METHODS

A Medline search of studies relevant to imaging diagnosis and management of the most common, benign, solid and non-solid liver lesions was undertaken. References from identified articles were handsearched for further relevant articles. The authors' own experiences with benign liver lesions were also taken into account.

RESULTS

Although atypical imaging features are the exception rather than the rule, it is sometimes difficult to differentiate between benign and malignant lesions, and knowledge of their imaging features is essential if unnecessary work-up is to be avoided. The use of tissue-specific contrast media, which has clearly improved the accuracy of highly advanced radiological techniques, may be helpful during differential diagnosis. Once having established an accurate diagnosis, surgery is rarely indicated for a benign liver lesion because of its asymptomatic nature.

CONCLUSION

Knowledge of imaging features and a clear management strategy during diagnostic work-up, emphasizing the indications for surgery, will minimize the number of patients who have to undergo biopsy or unnecessary surgery.

Differentiation of well-differentiated hepatocellular carcinomas from other hepatocellular nodules in cirrhotic liver: value of SPIO-enhanced MR imaging at 3.0 Tesla

PURPOSE

To determine the diagnostic value of superparamagnetic iron oxide (SPIO)-enhanced MRI for the differentiation of well-differentiated hepatocellular carcinomas (WD-HCCs) from other hepatocellular nodules in cirrhotic liver.

MATERIALS AND METHODS

This study included 114 patients with 216 histologically confirmed hepatocellular nodules, i.e., 23 dysplastic nodules (DNs), 37 WD-HCCs, and 156 moderately or poorly differentiated HCCs (MD-/PD HCCs), who underwent SPIO-enhanced MRI at 3.0T. MRI included T2-weighted fast-spin echo and T2*-weighted gradient recalled echo (GRE) sequences before and after administration of ferucarbotran. The contrast-to-noise ratio (CNR) of the lesion was calculated. Reviewers analyzed signal intensity (SI) of the nodules and their enhancement features on SPIO-enhanced images. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy in the diagnosis of WD-HCC were also calculated.

RESULTS

The mean CNR of WD-HCC was significantly higher than that of DN on T2*-weighted image. Incomplete high SI on SPIO-enhanced T2*-weighted images were seen in 56.8% of WD-HCC. The most prevalent enhancement features of WD-HCCs on SPIO-enhanced T2*-weighted images, were iso SI with high SI foci [32.5% (12/37)] and homogenous subtle high SI [24.3% (9/37)]. Alternatively, 22 of 23 DNs (95.7%) showed low- or iso SI, and 145 of 156 (94.9%) MD-/PD HCCs showed strong high SI. When iso SI with high SI foci or subtle homogenous high SI nodule was considered as diagnostic criteria for WD-HCC, we could identify 56.8% of the WD-HCCs but only 4.4% of the DNs and 3.2% of the MD-/PD HCCs.

CONCLUSION

WD-HCCs have characteristic enhancement features that differentiate them from DNs and MD-/PD HCCs on SPIO-enhanced 3.0T MRI. The lesion conspicuity was better on T2*-weighted images than that on T2-weighted images.Inc.

Focal liver lesion detection and characterization: comparison of non-contrast enhanced and SPIO-enhanced diffusion-weighted single-shot spin echo echo planar and turbo spin echo T2-weighted imaging

PURPOSE

To compare lesion conspicuity and image quality between single-shot spin echo echo planar imaging (SS SE-EPI) before, immediately and 5min after intravenous (IV) injection of superparamagnetic iron oxide (SPIO) for detecting and characterizing focal liver lesions (FLLs).

MATERIALS AND METHODS

Twenty-five patients suspected for colorectal liver metastases were prospectively included. Lesion detection and characterization were compared between all SS SE-EPI and T2-weighted turbo spin echo (T2w TSE) sets (two-sided Fisher's exact test). Image quality and lesion conspicuity were compared for SS SE-EPI sets using rank order statistic (RIDIT). Reference standard comprised of surgery, biopsy and/or follow-up.

RESULTS

Reference standard demonstrated 18 benign and 43 malignant FLLs. Best lesion detection (p<0.05) was achieved with non-contrast-enhanced SS SE-EPI. Lesion characterization was best using all T2w TSE sequences. Best image quality and lesion conspicuity (p<0.05) was achieved with non-contrast-enhanced SS SE-EPI.

CONCLUSION

Non-contrast-enhanced SS SE-EPI was best for lesion detection. SS SE-EPI sequences were not useful for lesion characterization (differentiation between benign and malignant lesions). Unenhanced SS SE-EPI did not allow differentiation especially as many benign FLLs were hyperintense on the highest b-value images. Combining unenhanced and SPIO-enhanced SS SE-EPI performed better but still was not clinically useful due to variable degree of uptake and vascular pooling of SPIO for (especially) benign FLLs. T2w TSE with SPIO-enhancement was needed for characterization.

Diagnostic performance and description of morphological features of focal nodular hyperplasia in Gd-EOB-DTPA-enhanced liver magnetic resonance imaging: results of a multicenter trial

OBJECTIVES

The aim of this prospective study was to evaluate the diagnostic performance of magnetic resonance imaging (MRI) of the liver with the hepatocellular-specific contrast agent gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) in comparison to precontrast MRI and spiral computed tomography (CT) in the specific diagnosis of focal nodular hyperplasia (FNH) and to describe morphologic features and enhancement pattern of FNH.

MATERIALS AND METHODS

In 176 patients from a phase III multicenter trial, 59 confirmed FNHs were present (13 = histopathology; 46 = imaging follow-up within 12 months before or 3 months after the MRI study). MR examination consisted of precontrast T1- and T2-w sequences, T1-weighted (w) dynamic sequences after bolus-injection of 0.025 mmol Gd-EOB-DTPA (Primovist; Bayer Schering Pharma)/kg bodyweight and T1-w sequences with fat saturation in the hepatocyte-phase after 20 minutes. The number of correctly characterized FNHs was evaluated and compared with that determined on spiral CT in an on-site reading (clinical study) and an off-site reading (3 blinded readers). The morphologic appearance and enhancement patterns of the FNHs were evaluated.

RESULTS

Characterization with combined pre- and post-MRI (88.1%) was superior to that achieved with biphasic-enhanced spiral CT (84.7%, not significant) and precontrast MRI (67.8%, P < 0.05) in the clinical study and significantly superior to both precontrast MRI and spiral CT for 2 of 3 blinded readers. Complete or partial enhancement of the lesions was present in the early dynamic phase (arterial and portovenous dynamic phase) in 94% and 85%, respectively. The pattern of lesion enhancement in the early dynamic phase was mainly homogenous (78%-80%); the median contrast-to-noise ratio was -5.9 in T1-w precontrast images, 14.0 in the arterial phase, 2.4 in the portovenous phase, and 2.9 in the equilibrium phase. Enhancement in the hepatocyte-phase after 10 and 20 minutes was observed in 88% and 90% of lesions, respectively.

CONCLUSIONS

Characterization of FNH provided by Gd-EOB-DTPA-enhanced MRI is superior to that provided by precontrast MRI alone or spiral CT. FNHs show very similar enhancement characteristics to those of other extracellular contrast agents in the early dynamic phase after bolus injection of Gd-EOB-DTPA, after 20 minutes in the liver-specific phase enhancement is regularly seen.

Ferucarbotran-enhanced T2-weighted magnetic resonance imaging: differentiation of hepatic cavernous hemangiomas from malignant solid lesions

BACKGROUND

To demonstrate the characteristic feature of hepatic cavernous hemangiomas on ferucarbotran-enhanced T2-weighted MR imaging as a new diagnostic finding.

METHODS

In 201 hepatic lesions (61 hemangiomas, 61 cysts, 41 hepatocellular carcinomas, 31 metastatic carcinomas, and 7 cholangiocarcinomas), lesion-to-liver contrast on ferucarbotran-enhanced T2-weighted images was qualitatively compared with pre-contrast images by three independent readers using a four-grade scale (group 1, marked increase; group 2, mild increase; group 3, no change; group 4, decrease). The change in the contrast-to-noise ratio (CNR) for each lesion was quantitatively measured.

RESULTS

Only hemangiomas showed a significant decrease in CNR; 10% and 90% of the hemangiomas were categorized as group 3 and 4 lesions, respectively. Besides the hemangiomas, there was no other lesion categorized into group 4 except for one cyst. When group 4 lesions were considered hemangiomas, the accuracy of identification was 96.4%.

CONCLUSION

Hemangiomas show a significant decrease in lesion-to-liver contrast on T2-weighted images after ferucarbotran injection, which might be another typical diagnostic imaging finding of hemangiomas distinguished from solid malignant lesions.

The value of gadobenate dimeglumine-enhanced delayed phase MR imaging for characterization of hepatocellular nodules in the cirrhotic liver

OBJECTIVES

To evaluate the value of 1-hour delayed phase imaging (DPI) of gadobenate dimeglumine (Gd-BOPTA)-enhanced MR imaging for the characterization of hepatocellular carcinoma (HCC) and dysplastic nodule (DN) in patients with cirrhosis.

MATERIALS AND METHODS

A total of 37 patients with 42 HCCs and 13 DNs were included in this study and all lesions were histopathologically confirmed except for 15 HCCs. T1-weighted 3-dimensional gradient-echo images were acquired before, immediately after (30, 60, 180 s), and 1 hour after bolus injection of gadobenate dimeglumine at a dose of 0.1 mmol/kg. The lesions were classified as isointense, hypointense, or hyperintense compared with the surrounding liver parenchyma on DPI for qualitative assessment. We performed quantitative analyses of the contrast-to-noise ratio (CNR) and of the relative contrast enhancement of the lesion on the DPI.

RESULTS

In the qualitative analysis, among 42 HCCs, 30 (71.4%) were hypointense on DPI, and 10 (23.8%) and 2 (4.8%) were isointense and hyperintense, respectively; only 1 of 13 DNs (7.7%) was hypointense and 10 (76.9%) and 2 (15.4%) were isointense and hyperintense, respectively. In contrast, 25 HCCs (71.4%) of 35 hypervascular HCCs were hypointense on DPI, and no hypervascular DN (0/7) was hypointense with statistical significance (P = 0.0007). When we considered the hypointensity of the hepatic lesions on delayed phase as a sign of HCC in cirrhotic liver, our results gave a sensitivity of 71.4% and a specificity of 91.7%. In the quantitative analysis, the mean CNR of the HCCs and the DNs on the 1-hour DPI was -6.32 +/- 6.27 and -0.07 +/- 3.28, respectively; the difference between the HCCs and the DNs was significant (P < 0.05).

CONCLUSIONS

Delayed gadobenate dimeglumine-enhanced MR imaging allows improved characterization of HCC in cirrhotic liver. The relative hypointensity to adjacent normal liver parenchyma is a reliable predictor that this lesion favors HCC rather than DN in cirrhotic liver.

Distinguishing benign from malignant liver tumours

Liver masses are very common and most are benign. It is therefore important to avoid unnecessary interventions for benign lesions, while at the same time ensuring accurate diagnosis of hepatic malignancies. Many cancer patients, like the general population, have incidental benign liver lesions. In planning treatment for cancer patients, it is critical to avoid inappropriate treatment decisions based on misdiagnosis of a benign lesion as a metastasis or primary liver malignancy. This article describes the salient imaging features of the common benign liver masses and outlines a general approach to distinguishing between benign and malignant hepatic lesions.

Ferucarbotran versus Gd-DTPA-enhanced MR imaging in the detection of focal hepatic lesions

AIM: To evaluate the efficacy of ferucarbotran-enhanced MR imaging in the detection of focal hepatic lesions compared to plain and Gd-DTPA-enhanced MR imaging.

METHODS: Fifty-nine patients with suspected focal hepatic lesions were admitted to the study. Plain MR imaging (FSE T₂WI with fat suppression and GRE T₁WI sequences) and Gd-DTPA dynamic enhanced MR of the liver were initially performed followed by ferucarbotran-enhanced MR imaging 48 h later (including GRE T₁WI, FSE T₂WI with fat suppression, and GRE T₂*WI sequences). Images were reviewed independently by three observers. Results were correlated with surgery and pathologic examination or reference examination, and sensitivity was statistically calculated for the different MR imaging sequences.

RESULTS: Among all confirmed lesions (n = 133), ferucarbotran-enhanced MR imaging revealed 130 lesions on FSE T₂WI with fat suppression, 115 lesions on dynamic T₁WI GRE, and 127 lesions on GRE T₂*WI. Pre-contrast MR imaging revealed only 84 lesions on GRE T₁WI and 106 lesions on FSE T₂WI with fat suppression, while Gd-DTPA dynamic enhanced GRE T₁WI revealed 123 lesions. For 44 micro-lesions (< 1.0 cm) in all patients the detection rates were as follows: ferucarbotran-enhanced FSE T₂WI with fat suppression, 93.2% (41/44); ferucarbotran-enhanced GRE T₂*WI, 88.6% (39/44); Gd-DTPA dynamic-enhanced GRE T₁WI, 79.5% (35/44); pre-contrast FSE T₂WI with fat suppression, 54.5% (24/44); and pre-contrast GRE T₁WI, 34.1% (15/44). In detecting micro-lesions, statistically significant difference was found for Ferucarbotran-enhanced FSE T₂WI with fat suppression and GRE T₂*WI sequences compared to the other sequences (P < 0.05).

CONCLUSION: Ferucarbotran-enhanced FSE T₂WI with fat suppression and GRE T₂*WI sequences are superior in detecting micro-lesions (< 1 cm) in comparison with plain and Gd-DTPA dynamic-enhanced MR imaging.

Superparamagnetic iron oxide (SPIO)-enhanced liver MRI with ferucarbotran: efficacy for characterization of focal liver lesions

PURPOSE

To evaluate the efficacy of ferucarbotran in T2-weighted (T2W) fast spin-echo (FSE) and T2*W gradient-echo (GRE) sequences for characterizing focal liver lesions.

MATERIALS AND METHODS

In 68 patients, 46 malignant and 22 benign focal liver lesions were evaluated. Precontrast (NCE) T2W FSE images and contrast-enhanced (CE) T2W FSE and T2*W GRE images were obtained on a 1.5T MR system. Based on signal intensity (SI) measurements in focal lesions and liver parenchyma, the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated for all sequences. The percentage of SI loss (PSIL) in focal lesions after contrast agent (CA) application was calculated for the T2W FSE sequence. Qualitative analyses were performed to assess image quality and lesion conspicuity obtained with the CE-T2W FSE and CE-T2*W GRE sequences.

RESULTS

The mean PSIL was higher in solid benign lesions than in malignant lesions (39.6% vs. 3.2%, P<0.05). With a threshold PSIL of 25%, the sensitivity and specificity for characterizing malignant lesions were 97.8% and 92.9%, respectively. The mean CNR of the malignant lesions was higher in the CE-T2*W sequence than in the CE- and NCE-T2W FSE sequences (29.9 vs. 22.7 (P<0.01) vs. 12.8 (P<0.01)). CE-T2*W images showed a superior image quality and lesion conspicuity (P<0.05) compared to the CE-T2W FSE sequence.

CONCLUSION

The PSIL can be an accurate tool for characterizing benign and malignant lesions. The addition of a CE-T2*W GRE sequence is helpful for the detection and characterization of malignant lesions.

Evaluation of small (<or=2 cm) dysplastic nodules and well-differentiated hepatocellular carcinomas with ferucarbotran-enhanced MRI in a 1.0-T MRI unit: utility of T2*-weighted gradient echo sequences with an intermediate-echo time

PURPOSE

To evaluate the detectability and signal intensities of small (<or=2 cm) dysplastic nodules (DNs) and well-differentiated hepatocellular carcinomas (w-HCCs) by T2*-weighted gradient echo (GRE) sequences using an intermediate echo-time (TE) with ferucarbotran in a 1.0-T magnetic resonance imaging (MRI) unit.

MATERIALS AND METHODS

Pathologically confirmed DNs (n=13) and w-HCCs (n=31) with a median largest dimension of 1.1cm were scanned using ferucarbotran-enhanced MRI. Conventional T2*-weighted GRE sequences (conventional-T2*-GRE: repetition time, 280 ms; echo time, 14 ms; flip angle, 60 degrees) and specific T2*-weighted GRE sequences using an intermediate-TE (specific-T2*-GRE: repetition time, 140 ms; echo time, 8 ms; flip angle, 30 degrees) were obtained before and after ferucarbotran administration. Two independent observers scored all nodules for visibility and assigned confidence level scores to their observations. To assess the effect of ferucarbotran, the tumor-liver signal contrast-to-noise ratio (tumor-liver-CNR) was also calculated for detected nodules by the same two observers with consensus.

RESULTS

There was good interobserver agreement regarding the presence of nodules for both sequence types. Qualitative and quantitative analyses indicated that specific-T2*GRE sequences were superior to conventional-T2*-GRE sequences for detecting DNs and w-HCCs with hypointense signals. The tumor-liver-CNR of DNs was significantly different between specific-T2*-GRE sequences and conventional-T2*-GRE sequences (Mann-Whitney test, P<0.001). Both qualitative and quantitative analyses indicated that conventional-T2*-GRE sequences were superior to specific-T2*-GRE sequences for detecting w-HCCs with heterogeneous and hyperintense signals.

CONCLUSION

Specific-T2*-GRE sequences with ferucarbotran are useful for detecting DNs and w-HCCs that produce hypointense signals on a 1.0-T MRI unit.

Focal nodular hyperplasia: lesion characteristics on state-of-the-art MRI including dynamic gadolinium-enhanced and superparamagnetic iron-oxide-uptake sequences in a prospective study

PURPOSE

To image a cohort of patients with pathology-proven focal nodular hyperplasia (FNH) to assess which characteristics of state-of-the-art magnetic resonance imaging (MRI) of the liver are the most useful for improving the detection and characterization of FNH.

MATERIALS AND METHODS

In 14 patients, pathology-proven FNH (N=33) were prospectively examined using gadolinium (Gd) and superparamagnetic iron-oxide (SPIO) contrast media. All lesions were evaluated for signal intensity (SI), fatty infiltration, central scar, mode of enhancement with Gd, and uptake of SPIO. The percentage of dynamic contrast enhancement in the arterial, portal, and delayed phases was assessed. The contrast-to-noise ratio (CNR) before and after administration of SPIO contrast was calculated.

RESULTS

The SI of the lesions was low to isointense on T1-weighted (T1W) images, and intermediate to isointense on T2W images. Fatty infiltration of the lesions was present in 6%. The percentages of enhancement in the liver and lesion were 110%, 115%, and 95%, and 151%, 182%, and 160%, respectively (P<0.0001). All lesions showed uptake of SPIO with improved conspicuity of the central scar and septa. The CNR values precontrast and post-Gd/SPIO were significantly different for T1 in- and opposed-phase and black-blood echo-planar imaging (BBEPI).

CONCLUSION

Combining dynamic Gd-enhanced imaging with T1W and T2W sequences after administration of SPIO facilitates comprehensive evaluation of FNH.

Focal nodular hyperplasia: Intraindividual comparison of dynamic gadobenate dimeglumine- and ferucarbotran-enhanced magnetic resonance imaging

PURPOSE

To intraindividually compare the enhancement pattern of focal nodular hyperplasia (FNH) after dynamic administration of two bolus-injectable liver-specific MR contrast agents, ferucarbotran and gadobenate dimeglumine.

MATERIALS AND METHODS

A total of 19 patients with 24 FNHs underwent gadobenate dimeglumine- and ferucarbotran-enhanced MRI during the hepatic arterial-dominant phase (HAP; 25 seconds), the portal-venous phase (PVP; 60 seconds), and the equilibrium phase (EP; 180 seconds). Hepatospecific phases were acquired on T1-weighted images 120 minutes after gadobenate dimeglumine administration, and on T2-weighted images 10 minutes after ferucarbotran administration. Lesion enhancement was independently analyzed by two observers. The kappa statistic was determined to evaluate the agreement between the enhancement patterns of the lesions.

RESULTS

On gadobenate dimeglumine-enhanced MR images during HAP, PVP, and EP, FNHs were: hyperintense (24/20/13); isointense (0/4/11); and hypointense (0/0/0). On ferucarbotran-enhanced MR images during HAP, PVP, and EP, FNHs were: hyperintense (2/0/0); isointense (16/9/14); and hypointense (6/15/10). Overall, poor agreement between both contrast agents was observed. During the hepatospecific phases, most (20/24; 83%) FNHs showed a typical enhancement pattern during the delayed hepatospecific phase.

CONCLUSION

The dynamic enhancement pattern of FNHs is significantly different between gadobenate dimeglumine- and ferucarbotran-enhanced MRI. With respect to hepatospecific phase, the majority of FNHs showed a typical behavior on both contrast agents.

Optimal TE for SPIO-enhanced gradient-recalled echo MRI for the detection of focal hepatic lesions

OBJECTIVE

The objective of our study was to determine the optimal TE for superparamagnetic iron oxide (SPIO)-enhanced gradient-recalled echo (GRE) MRI for the detection of focal hepatic lesions.

MATERIALS AND METHODS

Ferucarbotran-enhanced GRE sequences, performed on a 1.5-T MR system, were used to evaluate 131 lesions (38 hepatocellular carcinomas, 37 metastases, 21 hemangiomas, 7 cholangiocarcinomas, 15 cysts, and 13 miscellaneous lesions) at four different TEs: 9, 13.5, 18, and 22.5 milliseconds. The lesion-to-liver signal difference-to-noise ratio (SDNR) was compared among the four GRE sequences by paired Student's t tests and among lesion types by an independent samples Student's t test. The McNemar test was used to compare the sensitivity for the detection of focal hepatic lesions. Wilcoxon's signed rank test was used to compare the subjective lesion conspicuity.

RESULTS

The SDNRs of lesions on GRE images obtained at a TE of 13.5 milliseconds (mean +/- SD, 60 +/- 24) were significantly (p < 0.001) higher than those at TEs of 9 (55 +/- 23), 18 (55 +/- 22), and 22.5 milliseconds (47 +/- 19). The SDNR was highest at a TE of 13.5 milliseconds for SPIO-uptake lesions and was comparable on images obtained with TEs of 18 and 13.5 milliseconds for non-SPIO-uptake lesions. The non-SPIO-uptake lesions showed a significantly higher SDNR than the SPIO-uptake lesions at a TE of 22.5 milliseconds (p = 0.007). The overall sensitivity for lesion detection was not significantly different among the four GRE sequences, and the subjective ratings of lesion conspicuity were comparable for images obtained using TEs of 8, 13.5, and 18 milliseconds, but the ratings of lesion conspicuity were significantly lower for images obtained using a TE of 22.5 milliseconds (p < 0.001).

CONCLUSION

For ferucarbotran-enhanced MRI, lesion SDNR was highest on images obtained using a TE of 13.5 milliseconds, but the sensitivity and lesion conspicuity were comparable at TEs of 9 and 18 milliseconds. The SDNR of liver lesions varied according to the lesion's potential capability of taking up SPIO agents.

Liver tumor characterization: comparison between liver-specific gadoxetic acid disodium-enhanced MRI and biphasic CT--a multicenter trial

OBJECTIVE

In our multi center trial we compared the potentials of biphasic contrast-enhanced computed tomography (CT) and a novel tissue-specific magnetic resonance imaging (MRI) contrast agent gadoxetic acid disodium in liver lesion characterization.

METHODS

A total of 176 patients with 252 liver lesions were analyzed. There were 104 malignant and 148 benign lesions. High-field strength (1.0 T or 1.5 T) MR systems with T1-and T2-weighted sequences were used with and without fat suppression. After gadoxetic acid disodium injection, dynamic imaging and hepatocyte phase MR imaging were performed. Biphasic with 150 mg I/kg of body weight (100-200 mL) spiral CT was also performed. Image reading consisted of on-site (by study investigators) and fully blinded off-site (by E.S.P; C.R; and A.S) evaluations. The classification (benign or malignant) and characterization (lesion type) outcomes of both techniques were assessed. All imaging results were verified against a standard of reference.

RESULTS

Both on-site and off-site evaluations demonstrated increases in the lesion classification accuracy with gadoxetic acid disodium-enhanced MRI when compared with spiral CT. This improvement was also shown for characterization. Gadoxetic acid disodium was well tolerated.

CONCLUSIONS

Gadoxetic acid disodium offers a safe and diagnostically powerful tool for the evaluation of patients with focal liver lesions with a reliable assessment of lesion classification and characterization.

Magnetic Resonance Imaging Appearance of Well-differentiated Hepatocellular Carcinoma

OBJECTIVE

To investigate the magnetic resonance imaging (MRI) features of well-differentiated hepatocellular carcinoma (HCC).

METHODS

We reviewed the MRI of 32 patients with 33 pathologically confirmed well-differentiated HCC. The MRI protocol included T2-weighted imaging with and without fat saturation, dual-phase T1-weighted imaging, and gadolinium-enhanced dynamic study. The signal intensity of each lesion was categorized as hyperintense, isointense, and hypointense with reference to the surrounding liver parenchyma.

RESULTS

Thirty-one (93.9%) of 33 well-differentiated HCC were demonstrated on the MRI. The remaining 2 were isointense in all magnetic resonance sequences and, therefore, could not be identified. Most of them were hyperintense (n = 15 [45.4%]) or isointense (n = 16 [48.5%]) on T1-weighted imaging, and hyperintense (n = 12 [36.4%]) or isointense (n = 17 [51.5%]) on T2-weighted imaging. On the dynamic study, 17 lesions (51.5%) were enhanced.

CONCLUSIONS

MRI may identify most well-differentiated HCC; however, the imaging appearance is diverse. Biopsy should be performed if magnetic resonance study is inconclusive.

Imaging well-differentiated hepatocellular carcinoma with dynamic triple-phase helical computed tomography

To investigate the imaging appearance of well-differentiated hepatocellular carcinoma (HCC) on dynamic CT, a total of 38 histopathologically proven well-differentiated HCC were included in a retrospective study. We reviewed the contrast-enhanced dynamic CT of all 38 tumours for attenuation of each tumour in unenhanced scan, arterial-dominant and delayed portal venous phases. Our results showed that dynamic CT identified 26 (68.4%) out of the 38 lesions. The remaining 12 lesions were isodense compared with surrounding liver parenchyma in each dynamic CT phase. There was no statistically significant difference between the mean size of tumours detected by dynamic CT and that of tumours not detected by dynamic CT (p = 0.1). Of a total of 38 tumours, most were isodense (n = 19) or hypodense (n = 16) in unenhanced scan, mostly hyperdense (n = 18) or isodense (n = 15) in arterial-dominant phase and mostly isodense (n = 22) or hypodense (n = 15) in delayed portal venous phase. Enhancement of tumour was observed in 19 (50.0%) of 38 lesions. In conclusion, the ability of dynamic CT to detect well-differentiated HCC is poor, and negative CT findings cannot exclude the presence of well-differentiated HCC, especially if there is well-grounded clinical suspicion for HCC.

Hepatocellular carcinoma in cirrhosis: enhancement patterns at dynamic gadolinium- and superparamagnetic iron oxide-enhanced T1-weighted MR imaging

PURPOSE

To prospectively compare intraindividual differences in enhancement patterns between gadolinium- and superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance (MR) imaging in patients with histologically proved hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Institutional review board approval and informed consent were obtained. Twenty-two patients (18 men, four women; mean age, 58.9 years) with 36 pathologically proved HCC lesions underwent contrast material-enhanced dynamic T1-weighted gradient-echo MR imaging twice. Gadopentetate dimeglumine was used at the first session. After a mean interval of 5 days, a second session was performed with a bolus-injectable SPIO agent, ferucarbotran. Qualitative analysis of contrast enhancement patterns with each agent during hepatic arterial, portal venous, and equilibrium phases was performed by two readers who classified lesions as isointense, hypointense, or hyperintense compared with surrounding liver parenchyma and searched for presence of hyperintense peritumoral ring enhancement. Results of signal intensity analysis during different vascular phases at both sessions were compared by using the McNemar test, and kappa statistic was used to evaluate agreement between signal intensity and enhancement pattern of lesions during different vascular phases.

RESULTS

On gadolinium-enhanced hepatic arterial phase images, HCC lesions (n = 36) were hyperintense in 21 (58%) cases, hypointense in 10 (28%), and isointense in five (14%). On ferucarbotran-enhanced hepatic arterial phase images, HCC lesions were isointense in 18 (50%) cases, hypointense in 11 (31%), and hyperintense in seven (19%). On gadolinium-enhanced portal venous and equilibrium phase images, respectively, HCC lesions were hypointense in 17 (47%) and 21 (58%) cases, hyperintense in 10 (28%) cases and one (3%) case, and isointense in nine (25%) and 14 (39%) cases. On ferucarbotran-enhanced portal venous and equilibrium phase images, respectively, HCC lesions were hypointense in 15 (42%) and 11 (31%) cases, hyperintense in three (8%) and three (8%) cases, and isointense in 18 (50%) and 22 (61%) cases.

CONCLUSION

For HCC, contrast enhancement pattern on T1-weighted gradient-echo MR images shows marked variability with gadolinium or SPIO contrast agents.

Characterization of Hepatocellular Tumors

PURPOSE

To assess the value of mangafodipir trisodium-enhanced MR imaging for characterization of hepatocellular lesions.

MATERIALS AND METHODS

Magnetic resonance images of 41 patients with 48 histopathologically proven hepatocellular lesions (20 cases of focal nodular hyperplasia [FNH], 4 adenomas, 15 hepatocellular carcinomas [HCCs], 7 regenerative nodules, and 2 others) were retrospectively studied. Magnetic resonance imaging was performed on a 1.5-T unit (Vision, Siemens, Erlangen, Germany; ACS-NT, Philips, Best, The Netherlands) using T2-weighted, fat-saturation, turbo spin echo imaging and T1-weighted gradient echo imaging before and 20 minutes after infusion of 5 micromol/kg mangafodipir (Amersham Health, Oslo, Norway). Qualitative analysis by 4 blinded independent readers included assessment of unenhanced images and, in a second step, assessment of unenhanced and contrast-enhanced images together. Lesions were classified as benign or malignant using a 5-point scale, and readers made a specific diagnosis.

RESULTS

For characterization of hepatocellular lesions, mangafodipir-enhanced imaging was significantly superior to unenhanced imaging (P < 0.05). On receiver operating characteristic analysis, the area under the curve was 0.768 (95% confidence interval: 0.633-0.903) for unenhanced images and 0.866 (95% confidence interval: 0.767-0.966) for evaluation of unenhanced and contrast-enhanced images together (P < 0.05). Analysis of enhancement patterns aided in characterization and classification of tumors.

CONCLUSION

Administration of mangafodipir improves the differentiation between adenoma or HCC and "nonsurgical" lesions (FNH or regenerative nodules). The accuracy for arriving at a specific diagnosis is higher when unenhanced and mangafodipir-enhanced images are considered together than for unenhanced MR images alone.

Focal nodular hyperplasia of the liver: usefulness of superparamagnetic iron oxide-enhanced magnetic resonance imaging

This report describes the use of superparamagnetic iron oxide-enhanced magnetic resonance imaging to diagnose fibronodular hyperplasia of the liver in a 12-year-old girl.

Hepatocellular adenoma: imaging findings and pathological correlation

A 45-year-old man presented with a 1-week history of gastrooesophageal reflux, epigastric discomfort and abdominal pain especially in the right hypochondrium. Abdominal ultrasonography, contrast-enhanced spiral computed tomography and magnetic resonance imaging of the abdomen were performed. Eventually, imaging findings were correlated with histopathological analysis, which confirmed the diagnosis of a 18 cm x 16 cm hepatocellular adenoma.

Detection and characterization of focal hepatic lesions: mangafodipir vs. superparamagnetic iron oxide-enhanced magnetic resonance imaging

PURPOSE

To compare the mangafodipir-enhanced magnetic resonance (MR) and superparamagnetic iron oxide (SPIO)-enhanced images for their ability to detect and characterize focal hepatic lesions.

MATERIALS AND METHODS

Unenhanced, mangafodipir-enhanced, and SPIO-enhanced hepatic MR images obtained from 64 patients were analyzed. A total of 121 hepatic lesions were included: 66 hepatocellular carcinomas (HCCs), 26 metastases, 14 hemangiomas, 5 cysts, 3 cholangiocarcinomas, 4 focal nodular hyperplasias (FNHs), 2 abscesses, and 1 adenoma. Two radiologists independently reviewed the two sets of images in a random order: 1) the unenhanced and mangafodipir-enhanced images (the mangafodipir set) and 2) the unenhanced and SPIO-enhanced images (the SPIO set). This study compared the accuracy of lesion detection, the ability to distinguish between a benign and malignant lesion, and the ability to distinguish between the hepatocellular and nonhepatocellular origins of the lesions using the areas (Az) under the receiver operating characteristic (ROC) curve.

RESULTS

The overall accuracy for detecting focal lesions was significantly higher (P < 0.05) with the SPIO set (Az = 0.846 and 0.871 for readers 1 and 2, respectively) than with the mangafodipir set (Az = 0.716 and 0.766). Most of the lesions detected only with the SPIO-enhanced MR images by the readers were small HCCs. For lesions larger than 15 mm, the sensitivities of the two contrast enhancement techniques were similar for both readers. The accuracy of the mangafodipir and SPIO sets in distinguishing between benign and malignant lesions was comparable. The accuracy for distinguishing between the hepatocellular and nonhepatocellular origins of the lesions was significantly higher (P < 0.05) using the mangafodipir set (Az = 0.897 and 0.946) than using the SPIO set (Az = 0.741 and 0.833).

CONCLUSION

SPIO- and mangafodipir-enhanced images were comparable for detection of focal hepatic lesions other than small HCCs, which were better detected on the SPIO-enhanced images. Mangafodipir-enhanced images are likely better than the SPIO-enhanced images for distinguishing between focal liver lesions with a hepatocellular or nonhepatocellular origin.

Quantitative analysis of focal masses at MR imaging: a plea for standardization

PURPOSE

To assess the effects of changing analytic method variables on the signal intensity (SI) difference-to-noise ratios (SDNRs) for the contrast between lesions and background organs depicted on magnetic resonance (MR) images and to propose a standardized analytic method for the quantitative analysis of focal masses seen at MR imaging.

MATERIALS AND METHODS

The SIs of 48 liver metastases (originating from colorectal cancer) in 20 patients, the surrounding liver parenchyma, and the background noise were measured on T2-weighted MR images. All 2000 and 2001 issues of the American Journal of Roentgenology, the Journal of Magnetic Resonance Imaging, Magnetic Resonance Imaging, and Radiology were searched for articles describing quantitative analyses. SDNRs were calculated by using formulas from these articles and various region-of-interest (ROI) locations to measure metastasis and background noise SIs. The Wilcoxon signed rank test was used to compare the various SDNR calculations.

RESULTS

In 34 articles in which quantitative analyses of focal masses are described, the reported SDNRs were calculated with four different formulas. The SDNRs for our study material calculated with the four formulas reported in the literature differed grossly in both number and unit. The SDNRs for ROIs encompassing the entire metastasis differed significantly (P =.034) from the SDNRs for ROIs in a homogeneous area of the metastasis margin. Differences in SDNRs between various noise ROI locations were significant (P <.022).

CONCLUSION

Slight changes in the variables of quantitative analysis of focal masses had marked effects on reported SDNRs. To overcome these effects, the use of a standardized method involving one formula, a lesion ROI in a homogeneous area at the metastasis margin, and a background noise ROI along the phase-encoding axis in the air (including systematic noise) is proposed for the quantitative analysis of findings on magnitude MR images.

Comparison of dynamic gadolinium-enhanced and ferumoxides-enhanced MRI of the liver on high- and low-field scanners

PURPOSE

To compare the performance of dynamic gadolinium-enhanced and ferumoxides-enhanced MRI in the detection and characterization of hepatic lesions, on 1.5-T and 0.2-T magnets

MATERIALS AND METHODS

In 41 patients (23 men, 18 women), 52 hepatic MR examinations were performed and retrospectively analyzed; 39 and 13 examinations were performed on 1.5-T and 0.2-T magnets, respectively. A total of 33 of 41 patients had known malignancies, and 31 of 33 patients had biopsy of at least one lesion. First, a combination of unenhanced T2-weighted sequences and gradient-echo T1-weighted sequences were performed. Then, dynamic gadolinium-enhanced (0.1 mmol/kg) T1 GRE sequences were obtained, followed by intravenous drip infusion of ferumoxides (10 micromol/kg). The T2-weighted sequences were then repeated. The unenhanced and gadolinium-enhanced images (the Gd set) were reviewed separately from the unenhanced and ferumoxides-enhanced images (the ferumoxides set) by two abdominal imagers. The reviewers were blinded to clinical history and reviewed the individual studies in each set randomly. Each detected lesion was scored on a five-point scale for characterization scores: nonsolid (1 or 2), indeterminate (3), or solid (4 or 5). A consensus review was then performed correlating all available pathology, imaging, clinical findings, and follow-up to act as a gold standard. Receiver-operating-characteristic (ROC) curves were generated and both area-under-the-curve (Az values) and sensitivity values were calculated. Significance of Az and sensitivity differences was assessed using standard Z-test and chi-square.

RESULTS

Of 270 lesions detected by consensus, 211 were on 1.5-T and 59 were on 0.2-T scanners. The accuracy (Az values) of lesion detection overall, of both readers, was greater for the ferumoxides set than for the Gd set (reader 1: 0.95 vs. 0.89 (P < 0.05); reader 2: 0.91 vs. 0.78 (P < 0.05)). Az values for both readers were greater on the ferumoxides set for both the 1.5-T scans and the 0.2-T scans. Out of 270 lesions detected, 231 were characterized by consensus review as solid (185) or nonsolid (46). There was a significant improvement in lesion characterization for both readers on the GD set compared with the ferumoxides set on both high and low field scanners (Az reader 1: 0.99 vs. 0.96 (P < 0.05); Az reader 2: 0.99 vs. 0.95 (P < 0.05)), respectively.

CONCLUSION

At both 1.5-T and 0.2-T, ferumoxides-enhanced sequences were better for lesion detection, while gadolinium-enhanced sequences were better for lesion characterization, respectively.

Using superparamagnetic iron oxide-enhanced MRI to differentiate metastatic hepatic tumors and nonsolid benign lesions

OBJECTIVE

We evaluated the ability of superparamagnetic iron oxide (SPIO)-enhanced MRI to differentiate solid metastatic tumors and nonsolid benign lesions by clarifying the characteristic signal-intensity pattern of each lesion on SPIO-enhanced T2-weighted and heavily T1-weighted gradient-echo images.

MATERIALS AND METHODS

SPIO-enhanced MRI was performed using a 1.5-T system in 33 consecutive patients without cirrhosis who had 81 focal hepatic lesions (42 cysts, 13 hemangiomas, 26 metastatic tumors). The relative signal intensity of lesions on SPIO-enhanced heavily T1- and T2-weighted gradient-echo images was classified into one of the following three categories: high intensity, isointensity, or low intensity relative to the surrounding liver parenchyma. The diagnostic accuracy for differentiating solid metastatic tumors from nonsolid benign lesions (cysts or hemangiomas) was determined.

RESULTS

A combination of the relative signal intensity of the lesion on T2- and heavily T1-weighted gradient-echo images could be classified into the following five categories: high intensity and high intensity (category 1), high intensity and isointensity (category 2), high intensity and low intensity (category 3), isointensity and isointensity (category 4), and isointensity and low intensity (category 5). According to these categories, category 1 contained two hemangiomas, category 2 had 11 hemangiomas, category 3 had 25 metastatic tumors and two cysts, category 4 had three cysts, and category 5 had 37 cysts and one metastatic tumor. When a tumor with a relative signal intensity of categories 1 or 2 was considered to be a hemangioma (category 3 metastatic tumors and categories 4 and 5 cysts), diagnostic accuracy for characterizing such hepatic lesions was 96% (78/81).

CONCLUSION

When evaluating metastatic liver tumors on SPIO-enhanced MRI, we recommend that heavily T1- and T2-weighted gradient-echo images be obtained with our parameters to exclude hemangiomas or cysts.

Focal hepatic lesions: detection and characterization with combination gadolinium- and superparamagnetic iron oxide-enhanced MR imaging

PURPOSE

To compare gadolinium- and superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance (MR) imaging for detection and characterization of focal hepatic lesions when different contrast agent administration sequences are used.

MATERIALS AND METHODS

Unenhanced, dynamic gadolinium-enhanced, and SPIO-enhanced hepatic MR images were obtained in 134 patients. SPIO-enhanced MR imaging was performed immediately after gadolinium-enhanced dynamic MR imaging in 50 patients, 1 day after gadolinium-enhanced dynamic MR imaging in 40 patients, and before gadolinium-enhanced dynamic MR imaging in 44 patients. Two radiologists independently reviewed the gadolinium image set (unenhanced and gadolinium-enhanced dynamic MR images) and the SPIO image set (unenhanced and SPIO-enhanced MR images) in random order. Lesion detection sensitivity and lesion characterization accuracy were compared by analyzing the area under the receiver operating characteristic curve (Az).

RESULTS

Overall lesion detection accuracy for pooled data was significantly higher with the SPIO set (Az = 0.903) than with the gadolinium set (Az = 0.857) (P <.05). When hypovascular lesions were excluded, the detection rate was similar with the two sets. When hepatocellular carcinomas were excluded, the detection rate was significantly higher with the SPIO set (P <.01). Readers were more accurate in differentiating benign from malignant lesions with the gadolinium set (Az = 0.915) than with the SPIO set (Az = 0.847) (P <.01). Detection accuracy tended to be better with the images obtained after the second contrast agent was used.

CONCLUSION

Hypovascular lesion detection was better with SPIO-enhanced MR images than with gadolinium-enhanced MR images. Detection and characterization of hypervascular lesions were improved with gadolinium-enhanced MR images.

Hepatic MR imaging with ferumoxides: multicenter study of safety and effectiveness of direct injection protocol

PURPOSE

To compare the safety and effectiveness of an undiluted direct injection of ferumoxides with those of a diluted slow infusion of ferumoxides during 30 minutes in patients with known liver lesions or in those suspected of having them.

MATERIALS AND METHODS

Two hundred thirty-three patients at 16 institutions were randomized to receive either an undiluted direct injection of 0.56 mg of iron per kilogram of body weight of ferumoxides administered during 2 minutes (2 mL/min) or a diluted slow infusion administered during 30 minutes. Safety was assessed with monitoring for adverse events and laboratory tests. For sensitivity, specificity, and accuracy analysis, two independent blinded observers identified and classified lesions as benign or malignant with precontrast images and with pre- and postcontrast images combined.

RESULTS

There was no statistically significant difference in adverse events in the group with direct injection compared with those in the group with infusion (21 [18%] of 114 patients vs 19 [17%] of 112 patients, respectively). No serious adverse events were observed. The most common adverse events in the group with direct injection versus the group with infusion were headache (five [4%] of 114 vs three [3%] of 112, respectively) and back pain (five [4%] of 114 vs three [3%] of 112, respectively). Overall, in 68 (62%) of 109 patients with direct injection and 71 (66%) of 108 patients with infusion, additional magnetic resonance (MR) imaging information was obtained after ferumoxides administration (P =.67). Sensitivity, specificity, and accuracy for the diagnosis of malignancy were significantly improved by adding images obtained after ferumoxides administration to the images obtained before contrast agent administration (P <.05 for all comparisons).

CONCLUSION

Direct injection of ferumoxides has safety and effectiveness profiles similar to those of slow infusion of the agent. Further findings indicate that the addition of ferumoxides increases the sensitivity and specificity of hepatic MR evaluation when compared with unenhanced MR imaging.

MRI of focal nodular hyperplasia (FNH) with gadobenate dimeglumine (Gd-BOPTA) and SPIO (ferumoxides): an intra-individual comparison

PURPOSE

To compare the efficacy of two different MR contrast agents for the detection and diagnosis of focal nodular hyperplasia (FNH).

MATERIALS AND METHODS

Fifty patients with 83 FNH lesions detected on spiral CT were studied in two different MRI sessions with Gd-BOPTA (MultiHance) and ferumoxides (Endorem). MRI with Gd-BOPTA was performed precontrast (T1wGRE and T2wTSE sequences) and during the dynamic and late (1-3 hours) phases after injection (T1wGRE sequences only). MRI with ferumoxides (T1wGRE and T2wTSE sequences) was performed before and at least 30 minutes after injection. Hyper- or isointensity of FNH in the late phase was considered typical for Gd-BOPTA, while isointensity or lesion hypointensity was considered typical for ferumoxides.

RESULTS

With Gd-BOPTA, 83 FNH lesions (100%) appeared hyperintense during the arterial phase of dynamic MRI. All but one lesion was iso- or slightly hyperintense in the portal-venous and equilibrium phases. In the late phase, 81 FNH lesions were hyper- or isointense to the surrounding parenchyma, with two lesions appearing slightly hypointense. With ferumoxides, a significant (P < 0.001) number (21/83, 25.3%) of FNH lesions (mean diameter = 16.8 +/- 6.6 mm) were not visible. Of the visible FNH lesions, 38/62 were slightly hyperintense, and 24/62 were isointense to the surrounding parenchyma on the T2wTSE images. On the T1wGRE images, 42/62 lesions were isointense, 19/62 were slightly hyperintense, and one lesion was slightly hypointense. Seventeen lesions in 12 patients with previous neoplasia were all detected after Gd-BOPTA administration, whereas only nine of these 17 lesions (52.9%) were detected after ferumoxide administration. Two of these nine lesions showed atypical enhancement features.

CONCLUSION

Gd-BOPTA-enhanced MRI is significantly better than ferumoxide-enhanced MRI for the identification and characterization of FNH.

Characterization of focal liver lesions with superparamagnetic iron oxide-enhanced MR imaging: value of distributional phase T1-weighted imaging

OBJECTIVE

To determine the potential value of distributional-phase T1-weighted ferumoxides-enhanced magnetic resonance (MR) imaging for tissue characterization of focal liver lesions.

MATERIALS AND METHODS

Ferumoxides-enhanced MR imaging was performed using a 1.5-T system in 46 patients referred for evaluation of known or suspected hepatic malignancies. Seventy-three focal liver lesions (30 hepatocellular carcinomas (HCC), 12 metastases, 15 cysts, 13 hemangiomas, and three cholangiocarcinomas) were evaluated. MR imaging included T1-weighted double-echo gradient-echo (TR/TE: 150/4.2 and 2.1 msec), T2*-weighted gradient-echo (TR/TE: 180/12 msec), and T2-weighted turbo spin-echo MR imaging at 1.5 T before and after intravenous administration of ferumoxides (15 mmol/kg body weight). Postcontrast T1-weighted imaging was performed within eight minutes of infusion of the contrast medium (distributional phase). Both qualitative and quantitative analysis was performed.

RESULTS

During the distributional phase after infusion of ferumoxides, unique enhancement patterns of focal liver lesions were observed for hemangiomas, metastases, and hepatocellular carcinomas. On T1-weighted GRE images obtained during the distributional phase, hemangiomas showed a typical positive enhancement pattern of increased signal; metastases showed ring enhancement; and hepatocellar carcinomas showed slight enhancement. Quantitatively, the signal-to-noise ratio of hemangiomas was much higher than that of other tumors (p <.05) and was similar to that of intrahepatic vessels. This finding permitted more effective differentiation between hemangiomas and other malignant tumors.

CONCLUSION

T1-weighted double-echo FLASH images obtained soon after the infusion of ferumoxides, show characteristic enhancement patterns and improved the differentiation of focal liver lesions.

Contrast agents for hepatic magnetic resonance imaging

The current availability of liver-specific contrast media (LSCM) allows the possibility to obtain an accurate diagnosis when studying focal liver lesions (FLL). It is necessary to have an in-depth knowledge of the biologic and histologic characteristics of FLL and the enhancement mechanism of LSCM to gain significant accuracy in the differential diagnosis of FLL. It is possible to subdivide FLL into three main groups according to the kinetics of contrast enhancement: hypervascular FLL, hypovascular FLL, and FLL with delayed enhancement. Dynamic contrast-enhanced magnetic resonance imaging is an important tool in the identification and characterization of FLL. LSCM with a first phase of extracellular distribution give both dynamic (morphologic) and late phase (functional) information useful for lesion characterization. With LSCM it is possible to differentiate with high accuracy benign from malignant lesions and hepatocellular from nonhepatocellular lesions. To understand contrast behavior after injection of LSCM, it is necessary to correlate contrast enhancement with the biologic and histologic findings of FLL.

Characterization of focal hepatic lesions with ferumoxides-enhanced MR imaging: utility of T1-weighted spoiled gradient recalled echo images using different echo times

PURPOSE

To evaluate the different signal characteristics of focal hepatic lesions on ferumoxides-enhanced MR imaging, including T1-weighted spoiled gradient recalled echo (GRE) images using different echo times (TE) and T2- and T2*-weighted images.

MATERIALS AND METHODS

Ferumoxides-enhanced MR imaging was performed using a 1.5-T system in 46 patients who were referred for evaluation of known or suspected hepatic malignancies. One hundred and seven lesions (42 hepatocellular carcinomas [HCC], 40 metastases, 13 cysts, eight hemangiomas, three focal nodular hyperplasias [FNHs], and one cholangiocarcinoma) were evaluated. Postcontrast MR imaging included 1) T2-weighted FSE; 2) T2*-weighted GRE; 3) T1-weighted spoiled GRE using moderate (TE = 4.2-4.4 msec) TE; and 4) minimum (TE = 1.8-2.1 msec) TE. Signal intensities of the focal lesions were rated by two radiologists in conference as follows: hypointense, isointense or invisible, hyperintense, and markedly hyperintense. Lesion-to-liver contrast-to-noise ratio (C/N) was measured by one radiologist for a quantitative assessment.

RESULTS

On ferumoxides-enhanced FSE images, 92% of cysts were "markedly hyperintense" and most of the other lesions were "hyperintense", and the mean C/N of cysts was significantly higher than that of other focal lesions. T2*-weighted GRE images showed most lesions with similar hyperintensities and the mean C/N was not significantly different between any two types of lesion. T1-weighted GRE images using moderate TE showed all FNHsand hemangiomas, 29 (69%) HCCs and eight (20%) metastases as "hyperintense". On T1-weighted GRE images using minimum TE, however, all HCCs and metastasis except one were iso- or hypointense, while all of the FNHs and hemangiomas were hyperintense. Ring enhancement was highly suggestive of malignant lesions, and was more commonly seen on the minimum TE images than on the moderate TE images.

CONCLUSION

Addition of T1-weighted GRE images using minimum and moderate TE is helpful for characterizing focal lesions in ferumoxides-enhanced MR imaging.

Characterization of focal hepatic lesions with SPIO-enhanced MRI

AIM

To evaluate the value of superparamagnetic iron oxide (SPIO) enhanced MRI in characterizing focal hepatic lesions.

METHODS

Forty-three patients (32 men,11 women, mean age 51 years, age range 25-74 years) with previously identified focal hepatic lesions were enrolled into this study. All the patients underwent plain, Gd-DTPA enhanced MRI and the SPIO enhanced MRI 1-7 d later. The surgico-pathologic diagnosis was aestablished in 31 cases and the diagnosis in other 12 cases was made on the basis of clinical findings and biochemical tests. The signal changes of lesions were analyzed and the CNRs of lesion-to-liver were measured before and after SPIO enhancement. The data were analyzed by paired t test.

RESULTS

Focal hepatic lesions included primary hepatocellular carcinoma (HCC,n=22), hemangioma (n=5), cyst (n=4), metastases (n=5), cirrhotic nodule (n=4), focal nodular hyperplasia (FNH, n=5) and other miscellaneous lesions (n=6). After SPIO enhancement HCC demonstrated iso- or slight hyperintensity on T1WI and moderate hyperintersity on T2WI, hemangioma showed moderate hyperintensity on T1WI and obvious hyperintensity on T2WI, the SI of cyst had no change either on T1WI or on T2WI, cirrhotic nodules revealed iso-intensity on T2WI, and the SI of FNH decreased significantly on T2WI. No specific manifestations were found in the other 6 miscellaneous lesions after SPIO enhancement.

CONCLUSION

SPIO enhanced-MRI can improve the characterization confidence for diagnosis of focal hepatic lesions.

Benign liver neoplasms

A variety of benign focal liver lesions are easily characterized with currently available imaging techniques and contrast agents. The most common benign liver lesions, such as hemangioma, bile duct cyst, and FNH, reveal characteristic cross-sectional imaging features that allow an accurate diagnosis. For atypical variants and more uncommon lesions, including HCA, angiomyelioma, infantile hemagioendothelioma, and mesenchymal hamartoma, integration of clinical data can often help in the interpretation of imaging studies. Finally, for the remaining lesions, such as hepatic adenomatosis, the imaging findings may not be specific enough to negate the need for a tissue biopsy.