MR imaging of hepatic metastases

The humbling hemangioma: uncommon CT and MRI imaging features and mimickers of hepatic hemangiomas

Cavernous hemangiomas are among the most common liver lesions encountered in abdominal imaging. While classical imaging characteristics usually aid the radiologist in confidently arriving at its diagnosis, atypical hemangiomas can prove to be difficult to distinguish from other more worrisome hepatic lesions such as metastases and hepatocellular carcinoma. Furthermore, some malignant lesions can display features that simulate hemangiomas. The radiologist must be aware of these pitfalls to make an accurate diagnosis, when possible.

Differentiating peripheral cholangiocarcinoma in stages T1N0M0 and T2N0M0 from hepatic hypovascular nodules using dynamic contrast-enhanced MRI

Because cholangiocarcinoma shows no specific clinical signs or symptoms and presents with non-specific biological and tumor markers in the early stages, MRI findings often lack typical features before this lesion becomes symptomatic and might be mistaken for other liver lesions. An evaluation of relevant radiological findings in nodular cholangiocarcinoma (≤3 cm) in stages T1N0M0 and T2N0M0 is urgently needed. In our study, we compared two groups of liver hypovascular nodules and found that a distinct margin and enhanced area/nodule size >2/3 in the delayed phase were more frequently observed in cholangiocarcinoma cases than in metastatic nodule cases in which markedly high signal intensity on T2WI was common (p < 0.05). The results also revealed that in the both the portal and delayed phases, an enhanced area/nodule size >2/3 favored cholangiocarcinoma, whereas the presence of regional markedly higher SI on T2WI favored benign nodules. Furthermore, signs of peripheral washout in the delayed phase only appeared in cholangiocarcinoma cases.

An overview of imaging techniques for liver metastases management

Evaluation of liver metastases is one of the most common indications for liver imaging. Imaging plays a key role in the of assessment liver metastases. A variety of imaging techniques, including ultrasonography, computed tomography, MRI and PET combined with CT scan are available for diagnosis, planning treatment, and follow-up treatment response. In this paper, the authors present the role of imaging for the assessment of liver metastases and the contribution of each of the different imaging techniques for their evaluation and management. Following recent developments in the field of oncology, the authors also present the importance of imaging for the assessment of liver metastases response to therapy. Finally, future perspectives on imaging of liver metastases are presented.

Magnetic resonance imaging of a small vessel hepatic hemangioma in a cirrhotic patient with histopathologic correlation

The authors report and discuss a rare case of a small vessel hepatic hemangioma in a 59-year-old patient with liver cirrhosis, which was pre-procedurally characterized as indeterminate due to atypical magnetic resonance imaging (MRI) features. This manuscript reviews the MRI features with pathologic correlation, emphasizes the importance of accurate characterization of liver lesions, and discusses the role of biopsy. We believe this is the first reported case of a small vessel hemangioma in liver cirrhosis with imaging and histopathologic correlation.

DW-MRI of liver lesions: can a single ADC-value represent the entire lesion?

AIM

To evaluate whether focal liver lesions (FLLs) exhibit a homogeneous appearance on apparent diffusion coefficient (ADC) maps and whether there is inter-section variation in the calculated ADC values of FLLs (inter-section range).

MATERIALS AND METHODS

Eighty-eight patients with 128 FLLs (70 benign, 58 malignant) who underwent abdominal magnetic resonance imaging (MRI) including diffusion-weighted (DW)-MRI were included. Two observers evaluated variation of signal intensity of each FLL within each ADC map image (intra-section) and among different ADC map images through the lesion (inter-section). ADC values of each FLL and neighbouring liver parenchyma were measured on all sections. The inter-section range of FLLs was compared with the neighbouring liver parenchyma.

RESULTS

Intra-section inhomogeneity was noted in 39.8% (97/244 sections) and 38.9% (95/244) of benign lesions, and 61% (114/187 sections) and 61.5% (115/187) of malignant lesions, by observer 1 and observer 2, respectively. Inter-section inhomogeneity was noted in 25.7% (18/70) and 27.1% (19/70) of benign lesions, and 51.7% (30/58) and 50% (29/58) of malignant lesions, by observer 1 and observer 2, respectively. The inter-section range for both benign (0.28 × 10(-3) mm(2)/s) and malignant (0.25 × 10(-3) mm(2)/s) FLLs were significantly greater than that of liver parenchyma surrounding benign (0.16 × 10(-3) mm(2)/s, p < 0.001) and malignant (0.14 × 10(-3) mm(2)/s, p = 0.01) FLLs.

CONCLUSION

Due to intra-/inter-section variations in ADC values of benign and malignant FLLs, a single ADC value may not reliably represent the entire lesion.

Variability of apparent diffusion coefficients in metastatic small cell lung carcinoma: comparisons between-within normal tissue and liver metastases

In recent years, the use of diffusion weighted MRI (DW-MRI) has increased for the diagnosis of focal liver lesions (FLLs). DW-MRI may help in the differentiation of benign and malignant FLLs by measuring the apparent diffusion coefficient (ADC) values. Unfortunately, liver metastases present different histopathologic features with variable MRI signals within each lesion; this histologic variability explains the intra- and inter-lesion variations of ADC measurements. We present the case of a 64-year-old female with diagnosis of liver metastasis from small cell lung carcinoma admitted to the emergency unit due to symptoms of inappropriate antidiuretic hormone secretion. Quantitative comparison of two liver MRI, on admission and 2-months after transcatheter arterial chemoembolization showed persistence of the hyperintense metastatic lesions with significant difference in the ADC values in the with-in metastatic lesions (p = 0.001) and between normal tissue and liver metastases only at the end of treatment (p < 0.001). Several publications state that DWMRI is capable to predict the response to chemotherapy in malignant tumors, the histologic variability of liver metastasis and their response to different treatments is reflected in intra- and inter-lesion variations of ADC measurements that might delay an accurate imaging diagnosis. We present evidence of this variability, which might encourage prospective clinical trials that would define better cut-off values, would help understand the ADC biological behaviour, and would reach consensus about the best acquisition parametersfor this promising quantitative biomarker.

Selection for hepatic resection of colorectal liver metastases: expert consensus statement

Hepatic resection offers a chance of a cure in selected patients with colorectal liver metastases (CLM). To achieve adequate patient selection and curative surgery, (i) precise assessment of the extent of disease, (ii) sensitive criteria for chemotherapy effect, (iii) adequate decision making in surgical indication and (iv) an optimal surgical approach for pre-treated tumours are required. For assessment of the extent of the disease, contrast-enhanced computed tomography (CT) and/or magnetic resonance imaging (MRI) with gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) is recommended depending on the local expertise and availability. Positron emission tomography (PET) and PET/CT may offer additive information in detecting extrahepatic disease. The RECIST criteria are a reasonable method to evaluate the effect of chemotherapy. However, they are imperfect in predicting a pathological response in the era of modern systemic therapy with biological agents. The assessment of radiographical morphological changes is a better surrogate of the pathological response and survival especially in the patients treated with bevacizumab. Resectability of CLM is dependent on both anatomic and oncological factors. To decrease the surgical risk, a sufficient volume of liver remnant with adequate blood perfusion and biliary drainage is required according to the degree of histopathological injury of the underlying liver. Portal vein embolization is sometimes required to decrease the surgical risk in a patient with small future liver remnant volume. As a complete radiological response does not signify a complete pathological response, liver resection should include all the site of a tumour detected prior to systemic treatment.

Gd-EOB-DTPA-Enhanced MRI for Detection of Liver Metastases from Colorectal Cancer: A Surgeon's Perspective!

Colorectal cancer affects over one million people worldwide annually, with the liver being the most common site of metastatic spread. Adequate resection of hepatic metastases is the only chance for a cure in a subset of patients, and five-year survival increases to 35% with complete resection. Traditionally, computed tomographic imaging (CT) was utilized for staging and to evaluate metastases in the liver. Recently, the introduction of hepatobiliary contrast-enhanced magnetic resonance imaging (MRI) agents including gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Eovist in the United States, Primovist in Europe, or Gd-EOB-DTPA) has proved to be a sensitive method for detection of hepatic metastases. Accurate detection of liver metastases is critical for staging of colorectal cancer as well as preoperative planning.

Diffusion-weighted imaging of the liver: comparison of navigator triggered and breathhold acquisitions

PURPOSE

To compare a free breathing navigator triggered single shot echoplanar imaging (SS EPI) diffusion-weighted imaging (DWI) sequence with prospective acquisition correction (PACE) with a breathhold (BH) DWI sequence for liver imaging.

MATERIALS AND METHODS

Thirty-four patients were evaluated with PACE-DWI and BH DWI of the liver using b-values of 0, 50, and 500 s/mm(2). There were 29 focal liver lesions in 18 patients. Qualitative evaluation was performed on a 3-point scale (1-3) by two independent observers (maximum score 9). Quantitative evaluation included estimated SNR (signal to noise ratio), lesion-to-liver contrast ratio, liver and lesion apparent diffusion coefficients (ADCs), and coefficient of variation (CV) of ADC in liver parenchyma and focal liver lesions (estimate of noise contamination in ADC).

RESULTS

PACE-DWI showed significantly better image quality, higher SNR and lesion-to-liver contrast ratio when compared with BH DWI. ADCs of liver and focal lesions with both sequences were significantly correlated (r = 0.838 for liver parenchyma, and 0.904 for lesions, P < 0.0001), but lower with the BH sequence (P < 0.02). There was higher noise contamination in ADC measurement obtained with BH DWI (with a significantly higher SD and CV of ADC).

CONCLUSION

The use of a navigator echo to trigger SS EPI DWI improves image quality and liver to lesion contrast, and enables a more precise ADC quantification compared with BH DWI acquisition.

Focal liver lesion detection and characterization with diffusion-weighted MR imaging: comparison with standard breath-hold T2-weighted imaging

PURPOSE

To retrospectively compare diffusion-weighted (DW) magnetic resonance (MR) imaging with standard breath-hold T2-weighted MR imaging for focal liver lesion (FLL) detection and characterization, by using consensus evaluation and other findings as the reference standard.

MATERIALS AND METHODS

Approval for this retrospective HIPAA-compliant study was obtained from the institutional review board; informed consent was waived. Fifty-three consecutive patients (30 men, 23 women; mean age, 60.7 years) with at least one FLL of 1 cm or greater in diameter were evaluated. Two independent observers reviewed DW (b values of 0, 50, and 500 sec/mm(2)) and T2-weighted images for FLL detection and characterization. Reference standard for diagnosis was obtained from consensus review by the two observers of DW, T2-weighted, and dynamic contrast material-enhanced images, pathologic data, and follow-up imaging results. Apparent diffusion coefficient (ADC) was measured for FLLs identified at consensus review. DW and T2-weighted images were compared for FLL detection and characterization by using a binary logistic regression model. Receiver operating characteristic curve analyses were conducted to evaluate the utility of ADC for diagnosis of malignancy.

RESULTS

Two hundred eleven FLLs (136 malignant, 75 benign) were detected at consensus review. Overall detection rate (averaged for two observers) was significantly higher for DW (87.7%) versus T2-weighted (70.1%) imaging (P < .001). FLL characterization was not significantly different between DW (89.1%) and T2-weighted (86.8%) imaging (P = .51). ADCs of malignant FLLs were significantly lower than those of benign FLLs (P < .001). The area under the curve for diagnosis of malignancy was 0.839, with sensitivity of 74.2%, specificity of 77.3%, positive predictive value of 85.5%, negative predictive value of 62.3%, and accuracy of 75.3%, by using a threshold ADC of less than 1.60 x 10(-3) mm(2)/sec.

CONCLUSION

DW MR imaging was better than standard breath-hold T2-weighted imaging for FLL detection and was equal to breath-hold T2-weighted imaging for FLL characterization.

MR imaging in patients with suspected liver metastases: value of liver-specific contrast agent Gd-EOB-DTPA

The appropriate staging of malignant tumors is increasingly important as new therapeutic strategies develop. Because metastatic involvement of the liver in extrahepatic malignant disease may significantly change therapeutic approach, it is important to rule out such involvement with high confidence. Moreover, the differentiation between incidental benign lesions, such as hemangioma, focal nodular hyperplasia (FNH), or adenoma, is of high interest. Magnetic resonance (MR) imaging has proved reliable for diagnostic work-up of the liver. Liver-specific contrast agents have been especially helpful in detecting and precisely characterizing focal liver lesions, but the use of these agents has been limited because it has not been possible to perform both proper vascular phase and liver-specific phase within a reasonable time frame and in a single examination after a single injection of contrast agent. However, the hepatobiliary contrast agent gadolinium-ethoxybenzyl (Gd-EOB)-DTPA now allows combined dynamic imaging and hepatocyte-specific imaging in one examination. Gd-EOB-DTPA can be injected as a bolus and shows the enhancement characteristics and vascularity of liver lesions. In the delayed phase, which is acquired most appropriately 20 min after injection, Gd-EOB-DTPA is taken up selectively by functioning hepatocytes. Thus, malignant liver lesions, e.g. metastases, are spared from contrast uptake of the surrounding liver parenchyma. These lesions are hypointense in contrast to the surrounding bright liver. We review the current literature and present a practical approach to Gd-EOB-enhanced MR imaging using imaging examples of patients with liver metastases.

Focal hepatic lesions: diagnostic value of enhancement pattern approach with contrast-enhanced 3D gradient-echo MR imaging

Focal hepatic lesions constitute a daily challenge in the clinical setting. However, noninvasive methods can be useful in the detection and characterization of these lesions. The noninvasive diagnosis of liver lesions is usually achieved with contrast material-enhanced computed tomography and magnetic resonance (MR) imaging. Dynamic three-dimensional gradient-recalled-echo MR imaging provides dynamic contrast-enhanced thin-section images with fat saturation and a high signal-to-noise ratio and is excellent for the evaluation of various focal hepatic lesions. A comprehensive MR imaging examination in this setting includes T2-weighted and chemical shift T1-weighted imaging and demonstrates characteristic enhancement patterns that can be helpful in the diagnosis of most of these lesions. These enhancement patterns are seen during particular phases of contrast-enhanced imaging and include arterial phase enhancement, delayed phase enhancement, peripheral washout, ring enhancement, nodule-within-a-nodule enhancement, true central scar, pseudocentral scar, and pseudocapsule. Familiarity with these enhancement patterns can help in the identification of specific focal lesions of the liver.

Modern hepatic imaging

This article provides a brief overview of the current status of commonly employed diagnostic techniques--US, CT, MR, and PET--for the evaluation of liver metastases and HCC as well as a description of imaging in RF ablation and liver transplantation. The various advantages and limitations of the techniques have been outlined. At the present time, at our center, MRI is used most often to evaluate these liver pathologies, due to its high accuracy for lesion detection and characterization.

Percutaneous coil placement prior to radiofrequency ablation of poorly visible hepatic tumors

The aim of this study was to establish whether using a percutaneously inserted metallic coil as a target facilitates the radiofrequency (RF) ablation of tumors poorly seen on unenhanced computed tomography (CT) or ultrasound (US) studies. We inserted a metallic coil percutaneously via a 21-gauge needle under CT guidance into five tumors during the phase of contrast enhancement in five patients. The coil was subsequently used as a target to guide placement of the RF electrode under fluoroscopic guidance. The precision of position was then checked with CT or US. We also carried out a small experimental study to establish the effect of metallic coils on the pattern of coagulation induced by RF. Placement of a metallic coil into the tumor enabled rapid and accurate placement of the RF electrode. The tumors were ablated with no adverse effects. The experimental study showed that the area of coagulation extends predictably along the coil. The application of the above technique is useful when using RF to ablate tumors poorly visualized on US and unenhanced CT.

Spectrum of MRI appearances of untreated metastases of the liver

OBJECTIVE

The purpose of our study was to identify the spectrum of MRI appearances of untreated liver metastases from different primary origins.

MATERIALS AND METHODS

Over a period of 52 months, we used our clinical information system to retrospectively identify the first MRIs obtained in 165 consecutive patients who had untreated liver metastases. All patients had histologic confirmation of the primary tumor. Liver metastases were confirmed at histologic examination, on imaging, or at clinical follow-up. MR sequences used included T1-weighted spoiled gradient-echo, T2-weighted half-Fourier acquisition single-shot turbo spin-echo, and serial gadolinium-enhanced spoiled gradient-echo imaging. Size, signal intensity characteristics, and pattern of enhancement of the metastases on MRIs were evaluated by two radiologists in consensus. Lesions were categorized by size: smaller than 1.5 cm, between 1.5 and 3.0 cm, and larger than 3.0 cm.

RESULTS

A total of 516 metastases (size range, 5-120 mm; mean, 28 mm) were assessed. Fifty-nine patients had hypervascular lesions, and 106 patients had hypovascular lesions. A significant difference in proportion of tumor vascularity was observed between the primary tumors described as classically hypervascular and those described as classically hypovascular (chi-square test for proportions of 70.8, p < 0.0001). The most common pattern was peripheral ring (72% of patients) seen on the arterial dominant phase images, with incomplete central progression (63%) seen on the delayed phase images. A hypointense ring seen in the periphery of the tumor during the delayed phase was the most common appearance in hypervascular metastases (27% patients) and was particularly conspicuous in patients with neuroendocrine and carcinoid tumors. Perilesional enhancement was common (47%), mostly seen in hypovascular metastases (92%). Generally, large lesions tended to show a peripheral ring or heterogeneous enhancement, and small lesions showed homogeneous enhancement.

CONCLUSION

MRI allows the identification of a wide spectrum of appearances of untreated liver metastases. The extent and pattern of enhancement of various histologic types of tumor are depicted on MRI.