MR IMAGING IN THE EVALUATION OF HEPATIC METASTASES

Apparent Variation in Measurement Size of Colorectal Cancer Metastases to the Liver on Dual Contrast MRI

PURPOSE

The aim of this study was to formally investigate the apparent variation in lesion size of hepatic metastatic lesions from colorectal cancer on hepatobiliary phase (HBP) and dual contrast images of magnetic resonance imaging performed with both hepatobiliary and extracellular contrast agents.

METHODS

Patients with known colorectal carcinoma who had undergone dual contrast liver magnetic resonance imaging were identified in our institutional database. Metastatic lesions were measured semiautomatically on both HBP and dual contrast images with a custom software tool that automatically identifies the lesion edge and thereby the lesion diameter. Lesion measurements from both sets of images were compared with a Student t test and Bland-Altman analysis. Lesions were also measured on both HBP and dual contrast images by 2 fellowship-trained abdominal radiologists. Measurements from the software and radiologists were compared with a Student t test and Bland-Altman analysis; interreader agreement was evaluated with the intraclass correlation coefficient.

RESULTS

A total of 70 liver lesions in 39 patients was identified. Software-based measurements were significantly larger on HBP than dual contrast images ( P < 0.001), with a mean lesion size of 10.9 ± 4.2 mm for HBP and 10.5 ± 4.2 mm for dual contrast measurements. Radiologist-based measurements showed a similar trend, with HBP measurements being significantly larger than dual contrast measurements ( P < 0.001). Bland-Altman analysis indicated a mean bias ± 2 SD of +0.4 ± 1.6 mm for software-based measurements and +0.9 ± 2.9 mm and +0.7 ± 2.1 mm for readers 1 and 2, respectively. The intraclass correlation coefficient for interreader agreement was 0.9.

CONCLUSIONS

Both software-based and radiologist-based measurements of colorectal cancer liver metastases are significantly larger on HBP than dual contrast images. Based on these findings, we recommend that longitudinal assessment be performed consistently on either HBP or dual contrast phases to avoid introduction of avoidable variability.

Liver metastases: The role of magnetic resonance imaging

The liver is one of the organs most commonly involved in metastatic disease, especially due to its unique vascularization. It's well known that liver metastases represent the most common hepatic malignant tumors. From a practical point of view, it's of utmost importance to evaluate the presence of liver metastases when staging oncologic patients, to select the best treatment possible, and finally to predict the overall prognosis. In the past few years, imaging techniques have gained a central role in identifying liver metastases, thanks to ultrasonography, contrast-enhanced computed tomography (CT), and magnetic resonance imaging (MRI). All these techniques, especially CT and MRI, can be considered the non-invasive reference standard techniques for the assessment of liver involvement by metastases. On the other hand, the liver can be affected by different focal lesions, sometimes benign, and sometimes malignant. On these bases, radiologists should face the differential diagnosis between benign and secondary lesions to correctly allocate patients to the best management. Considering the above-mentioned principles, it's extremely important to underline and refresh the broad spectrum of liver metastases features that can occur in everyday clinical practice. This review aims to summarize the most common imaging features of liver metastases, with a special focus on typical and atypical appearance, by using MRI.

Focal Lesions of the Liver and Radiomics: What Do We Know?

Despite differences in pathological analysis, focal liver lesions are not always distinguishable in contrast-enhanced magnetic resonance imaging (MRI), contrast-enhanced computed tomography (CT), and positron emission tomography (PET). This issue can cause problems of differential diagnosis, treatment, and follow-up, especially in patients affected by HBV/HCV chronic liver disease or fatty liver disease. Radiomics is an innovative imaging approach that extracts and analyzes non-visible quantitative imaging features, supporting the radiologist in the most challenging differential diagnosis when the best-known methods are not conclusive. The purpose of this review is to evaluate the most significant CT and MRI texture features, which can discriminate between the main benign and malignant focal liver lesions and can be helpful to predict the response to pharmacological or surgical therapy and the patient's prognosis.

Whole‑body MRI for metastatic workup in patients diagnosed with cancer

Early diagnosis and appropriate staging workup are crucial for cancer patients. Whole-body magnetic resonance imaging (WB-MRI) has been proposed as another practical whole-body approach for assessing local invasiveness and distant metastases in patients newly diagnosed with cancer. The current study aimed to evaluate the efficacy of WB-MRI in assessing metastasis in patients newly diagnosed with cancer using histopathologic data as the reference method. A prospective observational study was performed from April 2018 to July 2020. MRI sequences were utilized to acquire anatomical and functional images in three orthogonal planes. The discovery was classified as nodal, skeletal and visceral metastases. Patient-based analysis was used for visceral metastasis and region-based for skeletal, systemic and lymph node metastases. A total of 43 consecutive patients (mean age, 56±15.2 years) were assessed successively. In 41 patients, there was a concordance between the WB-MRI and histological confirmation. The most prevalent site of metastasis was the skeletal system (18 patients). There were 12 individuals with liver metastasis, 10 with lung metastasis and 4 with peritoneal metastasis, with just one brain metastatic lesion found. On WB-MRI, 38 lymph node groups were deemed positive. Out of the total, 66 skeletal locations contained metastases. The accuracy of WB-MRI for nodal, skeletal and visceral metastases was (98.45, 100 and 100%, respectively). In conclusion, WB-MRI in three orthogonal planes, including the diffusion-weighted MRI with background body signal suppression sequence, may be utilized efficiently and accurately for assessing metastasis staging and may thus be utilized in patients with newly diagnosed cancer.

Imaging of calcified hepatic lesions: spectrum of diseases

Hepatic calcifications have been increasingly identified over the past decade due to the widespread use of high-resolution Computed Tomography (CT) imaging. Calcifications can be seen in a vast spectrum of common and uncommon diseases, from benign to malignant, including cystic lesions, solid neoplastic masses, and inflammatory focal lesions. The purpose of this paper is to present an updated review of CT imaging findings of a wide range of calcified hepatic focal lesions, which can help radiologists to narrow the differential diagnosis.

Differentiation of hepatic abscess from metastasis on contrast-enhanced dynamic computed tomography in patients with a history of extrahepatic malignancy: emphasis on dynamic change of arterial rim enhancement

OBJECTIVES

The objective of the study is to identify computed tomography (CT) findings that differentiate hepatic abscess from hepatic metastasis in a patient with a history of extrahepatic malignancy.

MATERIALS AND METHODS

This retrospective study included 30 patients with 93 hepatic abscesses and 40 patients with 125 hepatic metastases who had a history of extrahepatic malignancy and underwent contrast-enhanced dynamic CT with arterial phase (AP) and portal venous phase (PVP). The diagnosis of hepatic abscess and hepatic metastasis was made using pathological confirmation or clinical diagnosis. Margin, patchy parenchymal enhancement, arterial rim enhancement, dynamic change of arterial rim enhancement, size discrepancy of lesions between arterial and portal phases, bile duct dilatation, perilesional hyperemia, and perilesional low density were evaluated by two radiologists independently. Significant findings for differentiating two groups were identified at univariate and multivariate analysis with nomogram for predicting hepatic abscess. Interobserver agreement was also analyzed for each variable.

RESULTS

Multivariate analysis revealed that patchy parenchymal enhancement (P < 0.001), arterial rim enhancement persistent through PVP (P < 0.001), and perilesional hyperemia (P = 0.013) were independent significant findings to predict hepatic abscess than metastasis. Among them, arterial rim enhancement persistent through PVP showed a highest odds ratio (OR 33.73) on multivariate analysis and a highest predictor point on a nomogram for predicting hepatic abscess. When two of these three criteria were combined, 80.7% (75/93) of hepatic abscess were correctly identified, with a specificity of 85.6% (107/125). When all three criteria were satisfied, specificity was up to 100% (125/125).

CONCLUSIONS

At contrast-enhanced dynamic CT, patchy parenchymal enhancement, arterial rim enhancement persistent through PVP, perilesional hyperemia, and their combinations may be reliable CT features for differentiating hepatic abscess from metastasis in patients with a history of primary extrahepatic malignancy.

Combined chemoembolization and thermal ablation for the treatment of metastases to the liver

PURPOSE

The purpose of the study was to evaluate safety, time to recurrence, and overall survival (OS) in patients with liver metastases (LM), treated with transarterial chemoembolization (TACE) followed by ablation.

MATERIALS AND METHODS

This retrospective study included all patients with LM treated with combined TACE and ablation from August 1998 to September 2015. Forty-two patients (12 women, 30 men; age 62.9 ± 11.9 years) were treated for 44 LMs. Tumor characteristics, imaging response to treatment, recurrence, and OS data were reviewed. Statistical analysis included Kaplan-Meier estimation, Cox regression and Fisher's exact, Wilcoxon rank sum, or log rank tests.

RESULTS

Median follow-up was 10.3 months. Eighteen patients had 1 hepatic lesion, 16 had 2-5, and 8 had > 5. Median index lesion size was 4.7 cm (range 1.5-8 .0 cm). Tumor response (mRECIST) was available for 41/44 treated lesions, with CR in 32 (78.0%), PR in 8 (19.5%), and PD in 1 (2.4%). Long-term imaging follow-up was available for 38 patients. Freedom from local recurrence was 61% at 1 year and 50% at 2 years. OS was 55% at 1 year and 30% at 2 years (median OS, 14.5 months). Tumor size and histology were not predictors of time to progression or OS. Complications occurred in 19 patients (45%). Major complications occurred in 19% of patients and included hospitalization for fever (n = 2), hepatic abscess (n = 3) and fall requiring transfusion, portal vein thrombus causing lobar infarct, biliary fistula, and retroperitoneal hematoma (n = 1 each).

CONCLUSIONS

Combined TACE and ablation is effective for local tumor control of liver metastases up to 8 cm when part of a multidisciplinary treatment strategy. Major complications occurred in 19% of patients.

Liver metastases: Detection and staging

The liver is more often involved with metastatic disease than primary liver tumors. The accurate detection and characterization of liver metastases are crucial since patient management depends on it. The imaging options, mainly consisting of contrast-enhanced ultrasound (CEUS), multidetector computed tomography (CT), magnetic resonance imaging (MRI) with diffusion-weighted imaging (DWI), extra-cellular contrast media and liver-specific contrast media as well as positron emission tomography/computed tomography (PET/CT), are constantly evolving. PET/MRI is a more recent hybrid method and a topic of major interest concerning liver metastases detection and characterization. This review gives a brief overview about the spectrum of imaging findings and focus on an update about the performance, advantages and potential limitations of each modality as well as current developments and innovations.

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.

18 F-FDG PET/MR imaging in patients with suspected liver lesions: Value of liver-specific contrast agent Gadobenate dimeglumine

OBJECTIVES

To evaluate the added value of the application of the liver-specific contrast phase of Gadobenate dimeglumine (Gd-BOPTA) for detection and characterization of liver lesions in 18F-FDG PET/MRI.

METHODS

41 patients with histologically confirmed solid tumors and known / suspected liver metastases or not classifiable lesions in 18F-FDG PET/CT were included in this study. All patients underwent a subsequent Gd-BOPTA enhanced 18F-FDG PET/MRI examination. MRI without liver-specific contrast phase (MRI1), MRI with liver-specific contrast phase (MRI2), 18F-FDG PET/MRI without liver-specific contrast phase (PET/MRI1) and with liver-specific contrast phase (PET/MRI2) were separately evaluated for suspect lesions regarding lesion dignity, characterization, conspicuity and confidence.

RESULTS

PET/MRI datasets enabled correct identification of 18/18 patients with malignant lesions; MRI datasets correctly identified 17/18 patients. On a lesion-based analysis PET/MRI2 provided highest accuracy for differentiation of lesions into malignant and benign lesions of 98% and 100%. Respective values were 95% and 100% for PET/MRI1, 93% and 96% for MRI2 and 91% and 93% for MRI1. Statistically significant higher diagnostic confidence was found for PET/MRI2 and MRI2 datasets compared to PET/MRI1 and MRI1, respectively (p < 0.001).

CONCLUSION

The application of the liver-specific contrast phase in 18F-FDG PET/MRI further increases the diagnostic accuracy and diagnostic confidence for correct assessment of benign and malignant liver lesions.

Use of hepatobiliary phase images in Gd-EOB-DTPA-enhanced MRI of breast cancer hepatic metastasis to predict response to chemotherapy

OBJECTIVES

To determine the prognostic value of Gd-EOB-DTPA MRI findings of liver metastasis from breast cancer.

METHODS

29 metastatic lesions from 12 breast cancer patients who received chemotherapy were retrospectively reviewed. We evaluated hepatobiliary phase of the lesions and classified them as a "target" or "non-target" appearance. The relationship of appearance or SI ratio with tumor response was analyzed.

RESULTS

A non-target appearance was more frequent in disease control group than in non-control group [14/18 (77.8%) vs. 4/18 (22.2%)], and it was associated with a better response [p=0.048].

CONCLUSION

HBP analysis may be useful to predict the response to chemotherapy and survival.

Hypo-Vascular Liver Metastases Treated with Transarterial chemoembolization: Assessment of Early Response by Volumetric Contrast-Enhanced and Diffusion-Weighted Magnetic Resonance Imaging

OBJECTIVE: To evaluate the value of anatomic and volumetric functional magnetic resonance imaging (MRI) in early assessment of response to trans-arterial chemoembolization (TACE) in hypovascular liver metastases. METHODS: This retrospective study included 52 metastatic lesions (42 targeted and 10 non-targeted) in 17 patients who underwent MRI before and early after TACE. Two reviewers reported response by anatomic criteria (Response Evaluation Criteria in Solid Tumor [RECIST], modified RECIST [mRECIST], and European Association for the Study of Liver Disease [EASL]) and functional criteria (volumetric apparent diffusion coefficient and contrast enhancement). Treatment endpoint was RECIST at 6 months. A 2-sample paired t test was used to compare the mean changes after intra-arterial therapy. P < .05 was considered statistically significant. RESULTS: Reduction in mRECIST and EASL at 1 month was significant in the whole cohort as well as in responders by RECIST at 6 months, and the changes fulfilled partial response criteria for both metrics in responders. Responders also had significant changes in volumetric apparent diffusion coefficient (P = .01 and P = .03) and contrast enhancement (P < .0001 and P < .0001) at 1 month for both readers, respectively. CONCLUSION: At 1 month post treatment, responders did not fulfill RECIST criteria but fulfilled mRECIST and EASL criteria. In addition, volumetric contrast-enhanced and diffusion-weighted MRI may be helpful in evaluating early treatment response after TACE in hypovascular liver metastases in patients who have failed to respond to initial chemotherapy.

Improved Visibility of Metastatic Disease in the Liver During Intra-Arterial Therapy Using Delayed Arterial Phase Cone-Beam CT

Purpose

To compare the visibility of liver metastases on dual-phase cone-beam CT (DP-CBCT) and digital subtraction angiography (DSA), with reference to preinterventional contrast-enhanced magnetic resonance imaging (CE-MRI) of the liver.

Methods

This IRB-approved, retrospective study included 28 patients with neuroendocrine (NELM), colorectal (CRCLM), or sarcoma (SLM) liver metastases who underwent DP-CBCT during intra-arterial therapy (IAT) between 01/2010 and 10/2014. DP-CBCT was acquired after a single contrast agent injection in the tumor-feeding arteries at early and delayed arterial phases (EAP and DAP). The visibility of each lesion was graded by two radiologists in consensus on a three-rank scale (complete, partial, none) on DP-CBCT and DSA images using CE-MRI as reference.

Results

47 NELM, 43 CRCLM, and 16 SLM were included. On DSA 85.1, 44.1, and 37.5 % of NELM, CRCLM, and SLM, were at least partially depicted, respectively. EAP-CBCT yielded significantly higher sensitivities of 88.3 and 87.5 % for CRCLM and SLM, respectively (p < 0.01), but not for NELM (89.4 %; p = 1.0). On DAP-CBCT all NELM, CRCLM, and SLM were visible (p < 0.001). Complete depiction was achieved on DSA for 59.6, 16.3, and 18.8 % of NELM, CRCLM, and SLM, respectively. The complete depiction rate on EAP-CBCT was significantly higher for CRCLM (46.5 %; p < 0.001), lower for NELM (40.4 %; p = 0.592), and similar for SLM (25 %, p = 0.399). On DAP-CBCT however, the highest rates of complete depiction were found—NELM (97.8 %; p = 0.008), CRCLM (95.3 %; p = 0.008), and SLM (100 %; p < 0.001).

Conclusion

DAP-CBCT substantially improved the visibility of liver metastases during IAT. Future studies need to evaluate the clinical impact.

Combined gadoxetic acid and gadofosveset enhanced liver MRI for detection and characterization of liver metastases

PURPOSE

To compare gadoxetic acid alone and combined gadoxetic acid/gadofosveset trisodium-enhanced liver MRI for detection of metastases and differentiation of metastases from haemangiomas.

METHODS

Ninety-one patients underwent gadoxetic acid-enhanced liver MRI before and after additional injection of gadofosveset. First, two readers retrospectively identified metastases on gadoxetic acid alone enhanced delayed hepatobiliary phase T1-weighted images together with all other MR images (dynamic images, T2-weighted images, diffusion-weighted images). Second, readers assessed additional T1-weighted images obtained after administration of gadofosveset trisodium. For both interpretations, readers rated lesion conspicuity and confidence in differentiating metastases from haemangiomas. Results were compared using alternative free-response receiver-operating characteristic (AFROC) and conventional ROC methods. Histology and follow-up served as reference standard.

RESULTS

There were 145 metastases and 16 haemangiomas. Both readers detected more metastases using combined gadoxetic acid/gadofosveset (reader 1 = 130; reader 2 = 124) compared to gadoxetic acid alone (reader 1 = 104; reader 2 = 103). Sensitivity of combined gadoxetic acid/gadofosveset (reader 1 = 90 %; reader 2 = 86 %) was higher than that of gadoxetic acid alone (reader 1 = 72 %; reader 2 = 71 %, both P < 0.01). AFROC-AUC was higher for the combined technique (0.92 vs. 0.86, P < 0.001). Sensitivity for correct differentiation of metastases from haemangiomas was higher for the combined technique (reader 1 = 98 %; reader 2 = 99 % vs. reader 1 = 86 %; reader 2 = 91 %, both P < 0.01). ROC-AUC was significantly higher for the combined technique (reader 1 = 1.00; reader 2 = 1.00 vs. reader 1 = 0.87; reader 2 = 0.92, both P < 0.01).

CONCLUSION

Combined gadoxetic acid/gadofosveset-enhanced MRI improves detection and characterization of liver metastases compared to gadoxetic acid alone.

KEY POINTS

• Combined gadoxetic acid and gadofosveset-enhanced liver MRI significantly improves detection of metastases. • The combined enhancement technique improves the accuracy to differentiate metastases from haemangiomas. • Prospective studies need to determine the clinical impact of the combined technique.

[Modern imaging of liver metastases]

CLINICAL/METHODICAL ISSUE

The liver is the second most common location of metastases following the lymph nodes. The accurate characterization of focal liver lesions in oncology patients is especially important because of the high prevalence of benign liver lesions and the possibility of co-existing benign and malignant lesions. The exact interpretation of these lesions is crucial for therapeutic decisions and thus for the prognosis of the patient.

STANDARD RADIOLOGICAL METHODS

It is essential to detect all focal liver lesions and to distinguish benign from malignant lesions, especially in the management of oncology patients. Numerous imaging modalities are available for these challenges in the daily routine. An extensive understanding of the advantages and limitations of the various imaging modalities and knowledge of the morphology and the typical and atypical appearances of the different metastases is important.

METHODICAL INNOVATIONS

This review explains the radiological criteria for various metastases in different modalities. To evaluate the individual prognosis and risk assessment preoperatively, functional imaging is necessary. These personalized pretherapeutic diagnostics are discussed.

Hepatocellular carcinoma and other hepatic malignancies: MR imaging

Magnetic resonance (MR) imaging surpasses all other imaging modalities in characterizing liver lesions by virtue of the exquisite tissue contrast, specificity for various tissue types, and extreme sensitivity to contrast enhancement. In addition to differentiating benign from malignant lesions, MR imaging generally discriminates between the various malignant liver lesions. Hepatocellular carcinoma constitutes most primary malignant liver lesions and usually arises in the setting of cirrhosis. Intrahepatic cholangiocarcinoma is a distant second and features distinctly different imaging features. Overall, metastases are the most common malignant liver lesions and arise from several primary neoplasms; most commonly gastrointestinal, lung, breast, and genitourinary.

Magnetic resonance nanoparticles for cardiovascular molecular imaging and therapy

Molecular vascular imaging represents a novel tool that promises to change the current medical paradigm of 'see and treat' to a 'detect and prevent' strategy. Nanoparticle agents, such as superparamagnetic nanoparticles and perfluorocarbon nanoparticle emulsions, have been developed for noninvasive imaging, particularly for magnetic resonance imaging. Designed to target specific epitopes in tissues, these agents are beginning to enter clinical trials for cardiovascular applications. The delivery of local therapy with these nanoparticles, using mechanisms such as contact-facilitated drug delivery, is in the advanced stages of preclinical research. Ultimately, combined diagnostic and therapeutic nanoparticle formulations may allow patients to be characterized noninvasively and segmented to receive custom-tailored therapy. This review focuses on recent developments of nanoparticle technologies with an emphasis on cardiovascular applications of magnetic resonance imaging.

Paradoxical uptake of Gd-EOB-DTPA on the hepatobiliary phase in the evaluation of hepatic metastasis from breast cancer: is the "target sign" a common finding?

PURPOSE

The purpose was to describe magnetic resonance imaging (MRI) findings of breast cancer liver metastasis using gadoxetic acid (Gd-EOB-DTPA) with an emphasis on the added value of the hepatobiliary phase (HBP).

MATERIAL AND METHODS

Nine patients with 13 liver metastases were included in the study after the medical records of 29 breast cancer patients who underwent Gd-EOB-DTPA-enhanced MRI between February 2008 and June 2010 were reviewed. The diagnoses of liver metastasis were established by percutaneous liver biopsy or surgery and on the basis of image findings. Two radiologists retrospectively evaluated signal intensity (SI) and sizes of metastases and patterns of enhancement in an HBP. The SI ratio was calculated as the SI of the central hyperintense portion in "target" lesions divided by the SI of nearby normal liver parenchyma on the HBP. We also measured apparent diffusion coefficient (ADC) values from Diffusion Weighted Image (DWI).

RESULTS

Liver metastases were all hypointense [n=13/13 (100%)] on T1-weighted imaging (WI), and many lesions had a "target" appearance with a central high SI and a peripheral low SI rim (47%) on T2WI. Dynamic study showed rim enhancement on the arterial phase (85%) and a "target" appearance, consisting of a central enhancing portion with peripheral washout or hypointense rim, on the HBP (62%). The mean SI ratio was 0.7. The mean ADC value of "target" appearing metastases was 1.25 (×10(-3) mm(2)/s; range 1.3-1.6) compared with a mean value of 0.8 (×10(-3) mm(2)/s; range 0.8-1.4) in homogeneous defect on the HBP. There was statistically significant difference (P<.05).

CONCLUSION

Breast cancer liver metastases commonly demonstrated as a peripheral ring enhancement on arterial dominant phase and a target sign with a central round enhancing portion and a peripheral hypointense rim on the HBP.

Is hepatotropic contrast enhanced MR a more effective method in differential diagnosis of hemangioma than multi-phase CT and unenhanced MR?

BACKGROUND

Cavernous hemangiomas are the most frequent neoplasms of the liver and in routine clinical practice they often need to be differentiated from malignant tumors and other benign focal lesions. The purpose of this study is to evaluate whether diagnostic accuracy of magnetic resonance imaging (MRI) of hepatic hemangiomas, showing atypical pattern on US, improves with the use of Gd-BOPTA in comparison with contrast-enhanced multi-phase computed tomography (CT).

METHODS

178 consecutive patients with ambiguous hepatic masses showing atypical hyperechoic pattern on grey-scale US, underwent unenhanced and contrast-enhanced multi-phase multi-detector CT and MR (1.5T) with the use of liver-specific contrast medium gadobenate dimeglumine (Gd-BOPTA). After intravenous contrast administration arterial (HAP), venous-portal (PVP), equilibrium phases (EP) both in CT and MR and additionally hepatobiliary phase (HBP) in MR were obtained. 398 lesions have been detected including 99 hemangiomas and 299 other lesions.

RESULTS

In non-enhanced MDCT examination detection of hemangiomas was characterized by sensitivity of 76%, specificity of 90%, PPV of 71%, NPV of 92% and accuracy of 86%.Non-enhanced MR examination showed sensitivity of 98%, specificity of 99%, PPV of 99%, NPV of 99% and accuracy of 99%.After intravenous administration of contrast medium in MR the mentioned above parameters did not increase significantly.

CONCLUSION

Gd-BOPTA-enhanced MR in comparison with unenhanced MRI does not improve diagnostic accuracy in discriminating hemangiomas that show non-specific appearance in ultrasound examination. Unenhanced MR as a method of choice should directly follow US in course of diagnostic algorithm in differentiation of hemangiomas from other liver tumors.

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.

Normal dynamic MRI enhancement patterns of the upper abdominal organs: gadoxetic acid compared with gadobutrol

OBJECTIVE

The purpose of this study was to investigate whether, at dynamic MRI of the upper abdominal organs, contrast enhancement with gadoxetic acid, a hepatobiliary contrast agent, is comparable with that achieved with an extracellular contrast agent.

SUBJECTS AND METHODS

Dynamic gadoxetic acid-enhanced MRI of the pancreas, spleen, kidney, liver, and abdominal aorta was performed on 50 patients; dynamic gadobutrol-enhanced MRI was performed on a control group of 50 patients; and the images were compared. Dynamic imaging with a T1-weighted volumetric interpolated breath-hold examination gradient-echo sequence (TR/TE, 3.35/1.35; flip angle, 12 degrees ) was performed before and 20 (arterial phase), 55 (portal venous phase), and 90 (hepatic venous phase) seconds after bolus injection of gadoxetic acid (0.25 mmol/mL) or gadobutrol (1.0 mmol/mL). Signal-to-noise ratios and enhancement indexes were calculated for each organ and time.

RESULTS

All MR images in both groups were of diagnostic quality. During the early dynamic phases, significantly lower mean enhancement indexes were found in the gadoxetic acid group than in the gadobutrol group in the pancreas (portal venous phase, 0.66, 1.39, p <or= 0.001; hepatic venous phase, 0.51, 1.36, p <or= 0.001), spleen (portal venous phase, 1.54, 2.41, p <or= 0.001; hepatic venous phase, 1.19, 2.23, p <or= 0.001), renal cortex (portal venous phase, 1.76, 2.63, p <or= 0.001; hepatic venous phase, 1.60, 2.63, p <or= 0.001), and liver (portal venous phase, 0.76, 0.94, p = 0.016; hepatic venous phase, 0.76, 1.04, p <or= 0.001). In the abdominal aorta, the mean enhancement index was greater after bolus injection of gadoxetic acid (arterial phase, 3.33, 2.24, p <or= 0.005).

CONCLUSION

Early dynamic MRI of the upper abdominal organs, especially the spleen, pancreas, and kidney, benefits from the higher gadolinium concentration of gadobutrol than in the organ-specific contrast agent gadoxetic acid. Higher protein binding resulting in increased relaxivity of gadoxetic acid compensates for the low gadolinium concentration in the abdominal aorta.

Preoperative imaging staging of rectal cancer

Carcinomas of the rectum are associated with a significant local and distant recurrence rate. Not all patients are appropriate candidates for preoperative radiation therapy. Preoperative identification of those most likely to benefit from neoadjuvant therapy is important. There is no general consensus on the role of endorectal ultrasonography, computed tomography (CT), and magnetic resonance imaging (MRI) in staging patients with rectal cancer. Although the tumor stage is an important prognostic factor, preoperative assessment is associated with prediction of the circumferential resection margin. Newer developments such as coils, sequences and gradients in MRI, evolution of multidetector CT and new contrast media, allow for an algorithm selection aiming at the best diagnostic options for patients. The present review will discuss the current role of the various imaging modalities in staging carcinomas of the rectum.

Detection of hepatic metastasis: manganese- and ferucarbotran-enhanced MR imaging

PURPOSE

To compare the mangafodipir trisodium (MnDPDP)-enhanced and ferucarbotran-enhanced magnetic resonance imaging (MRI) for the detection of hepatic metastases.

MATERIAL AND METHODS

Twenty patients with known hepatic metastasis underwent MR imaging using mangafodipir trisodium and ferucarbotran in at least 1-day intervals. Thirty-eight metastases were confirmed either histologically or clinically. Two radiologists independently reviewed the MnDPDP-enhanced and ferucarbotran-enhanced sets in a random order. The sensitivity and accuracy of lesion detection and the ability to distinguish a benign lesion from a malignant lesion were compared by the areas (Az) under the receiver operating characteristic (ROC) curve. The lesion-liver contrast-to-noise ratios (CNR) were compared by paired t-test.

RESULTS

The overall accuracy for detecting metastases was not significantly different between the MnDPDP set (Az=0.912 and 0.913 for reader 1 and 2, respectively) and the SPIO set (Az=0.920 and 0.950). The CNR at the MnDPDP-enhanced images and the SPIO-enhanced images were not significantly different (P=0.146).

CONCLUSION

Both MnDPDP- and ferucarbotran-enhanced MRI have a comparable accuracy in detecting hepatic metastasis.

Diagnostic accuracy of portal-phase CT and MRI with mangafodipir trisodium in detecting liver metastases from colorectal carcinoma

AIM

To compare the diagnostic accuracy of single section spiral computed tomography (CT) and magnetic resonance imaging (MRI) with tissue-specific contrast agent mangafodipir trisodium (MnDPDP) in the detection of colorectal liver metastases.

MATERIAL AND METHODS

One hundred and twenty-five consecutive patients undergoing surgery for primary and/or metastatic disease were evaluated using CT (5 mm collimation and reconstruction interval, pitch 2), two-dimensional fast spoiled gradient echo (2D FSPGR) T1 and single shot fast-spin echo (SSFSE) T2 weighted breath-hold MRI sequences, performed before and after intravenous administration of MnDPDP. The reference standards were intraoperative ultrasound and histology.

RESULTS

The per-patient accuracy of CT was 72.8 versus 78.4% for unenhanced MRI (p = 0.071) and 82.4% for MnDPDP-enhanced MRI (p = 0.005). MnDPDP-enhanced MRI appeared to be more accurate than unenhanced MRI but this was not significant (p = 0.059). The sensitivity of CT was 48.4% versus 58.1% for unenhanced MRI (p = 0.083) and 66.1% for MnDPDP-enhanced MRI (p = 0.004). The difference in specificity between procedures was not significant. The per-lesion sensitivity was 71.7, 74.9 and 82.7% for CT, unenhanced MRI, and MnDPDP-enhanced MRI, respectively; the positive predictive value of the procedures was respectively 84.0, 96.0 and 95.8%. MnDPDP-enhanced MRI provided a high level diagnostic confidence in 92.5% of the cases versus 82.5% for both unenhanced MRI and CT. The kappa value for inter-observer variability was >0.75 for all procedures.

CONCLUSIONS

The diagnostic accuracy and sensitivity of MnDPDP-enhanced MRI is significantly higher than single section spiral CT in the detection of colorectal cancer liver metastases; no significant difference in diagnostic accuracy was observed between unenhanced MRI and MnDPDP-enhanced MRI.

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.

MR imaging of the liver

MR imaging is establishing a role as a primary diagnostic technique, with increasing evidence showing MR imaging to have advantages over CT regarding diagnostic sensitivity and specificity for many pathologies of solid organs, bile and pancreatic ducts, bowel, peritoneum, and retroperitoneum. In addition, there are increasing concerns regarding the risks of radiation and iodinated contrast associated with CT imaging of the abdomen. The incidence of contrast-induced nephropathy associated with iodinated contrast used for CT scanning is difficult to ascertain because reporting is spurious and variable in interpretation.

Magnetic resonance molecular imaging with nanoparticles

Molecular imaging agents are extending the potential of noninvasive medical diagnosis from basic gross anatomic descriptions to complicated phenotypic characterizations based on the recognition of unique cell surface biochemical signatures. Although originally the purview of nuclear medicine, molecular imaging is now a prominent feature of most clinically relevant imaging modalities, in particular magnetic resonance (MR) imaging. MR nanoparticulate agents afford the opportunity not only for targeted diagnostic studies but also for image-monitored site-specific therapeutic delivery, much like the "magic bullet" envisioned by Paul Erhlich 100 years ago. Combining high-resolution MR molecular imaging with drug delivery will facilitate verification and quantification of treatment (ie, rational targeted therapy) and will offer new clinical approaches to many diseases.

Small (≤ 2 cm) Hepatic Lesions in Colorectal Cancer Patients:Detection and Characterization on Mangafodipir Trisodium–Enhanced MRI

OBJECTIVE

The purpose of this study was to evaluate whether mangafodipir trisodium (MnDPDP)-enhanced MRI improves the detection and characterization of small (<or= 2 cm) hepatic lesions in patients with colorectal carcinoma, compared with helical CT. SUBJECTS AND METHODS. Sixty-nine patients who had or were suspected of having focal liver lesions underwent helical CT and MnDPDP-enhanced MRI and constituted the study population. Two experienced radiologists independently reviewed CT and MR images for the number of hepatic lesions seen and whether the lesion appeared to be benign or metastatic; their interpretations were correlated with the reference diagnoses, including histopathologic diagnoses in 35 patients. The lesions were categorized as small (<or= 2.0 cm in diameter) or large (> 2.0 cm). The differences between MnDPDP-enhanced MRI and helical CT with regard to the detection rates for hepatic lesions and metastases and with regard to the false-positive rates for hepatic metastases were analyzed using the McNemar test. The performances of MnDPDP-enhanced MRI and helical CT in indicating metastases of focal liver lesions were analyzed using receiver operating characteristic curves.

RESULTS

No statistically significant differences were seen between MnDPDP-enhanced MRI and helical CT in the detection of all hepatic lesions (p = 0.383) and small lesions (p = 0.210). However, concerning the differentiation between benign and metastatic lesions, MnDPDP-enhanced MRI was superior to helical CT both for all hepatic lesions (p = 0.023) and for small lesions (p = 0.015), and remained better when the analyses were restricted to patients with histopathologic confirmation (p = 0.023 for both). MnDPDP-enhanced MRI changed the diagnosis of hepatic metastasis in nine (13.0%) of 69 patients. Of 12 metastases that were found on MnDPDP-enhanced MRI and missed on helical CT, 11 lesions (91.7%) were small. MnDPDP-enhanced MRI showed a significantly greater detection rate than helical CT for small hepatic metastases (p = 0.022). MnDPDP-enhanced MRI was better when the analyses were restricted to patients with histopathologic confirmation (p = 0.043).

CONCLUSION

Although MnDPDP-enhanced MRI is equal to helical CT in detection of both all hepatic lesions and small lesions in patients with colorectal carcinoma, it is superior to CT in characterization of the lesions.

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.

MR imaging of liver tumors

The article reviews the current MR imaging techniques commonly utilized for imaging liver tumors. Breath-hold T1-weighted GRE sequences, FSE T2-weighted sequences, and properly timed contrast-enhanced 3D SGE are important for lesion characterization. New liver-specific contrast agents improve lesion detection and are useful in lesion characterization.

MR imaging of hepatic metastases

MR imaging is an excellent diagnostic tool for the detection and characterization of liver metastases. The most characteristic finding is peripheral ring enhancement on immediate postgadolinium images.

Magnetic resonance imaging. Liver-specific contrast agents

MR imaging with new liver-specific contrast agents will probably be the imaging modality used in the future to detect focal liver lesions. The detection of HCC will probably be improved by using specific hepatobiliary agents, but the exact technique remains to be determined. New liver-specific contrast can differentiate some benign lesions from malignant ones and can assist in making a final diagnosis. In certain circumstances, liver-specific contrast agents can be used to evaluate hepatic vessels, the biliary tract, and hepatic function. New applications are also expected.