Small colorectal liver metastases: detection with SPIO-enhanced MRI in comparison with gadobenate dimeglumine-enhanced MRI and CT imaging

The Management of Oligometastatic Disease in Colorectal Cancer: Present Strategies and Future Perspectives

Oligometastatic disease has been described as an intermediate clinical state between localized cancer and systemically metastasized disease. Recent clinical studies have shown prolonged survival when aggressive locoregional approaches are added to systemic therapies in patients with oligometastases. The aim of this review is to outline the newest options to treat oligometastatic colorectal cancer (CRC), also considering its molecular patterns. We present an overview of the available local treatment strategies, including surgical procedures, stereotactic body radiation therapy (SBRT), thermal ablation, as well as trans-arterial chemoembolization (TACE) and selective internal radiotherapy (SIRT). Moreover, since imaging methods provide crucial information for the early diagnosis and management of oligometastatic CRC, we discuss the role of modern radiologic techniques in selecting patients that are amenable to potentially curative locoregional treatments.

Colorectal Cancer Liver Metastases: Multimodal Therapy

Despite a steady decline in incidence and mortality rates, colorectal cancer (CRC) remains the second most common cancer diagnosis in women and the third most common in men worldwide. Notably, the liver is recognized as the most common site of CRC metastasis, and metastases to the liver remain the primary driver of disease-specific mortality for patients with CRC. Although hepatic resection is the backbone of curative-intent treatment, management of CRLM has become increasingly multimodal during the last decade and includes the use of downstaging chemotherapy, ablation techniques, and locoregional therapy, each of which are reviewed herein.

Comparison of contrast-enhanced transabdominal ultrasonography following endoscopic ultrasonography with GD-EOB-DTPA-enhanced MRI for the sequential diagnosis of liver metastasis in patients with pancreatic cancer

PURPOSE

To compare contrast-enhanced transabdominal ultrasonography (CE-US) following contrast-enhanced harmonic endoscopic ultrasonography (CH-EUS) with enhanced magnetic resonance imaging using gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (EOB-MRI) in the diagnosis of liver metastases in patients with pancreatic cancer.

METHODS

Patients who underwent contrast-enhanced computed tomography for possible pancreatic cancer and required further evaluation with CH-EUS were enrolled in this study, and the diagnostic performance of CE-US following CH-EUS for liver metastasis was compared with that of EOB-MRI.

RESULTS

A total of 228 patients were included in the final analysis. Two hundred thirty-four hepatic lesions were found in 81 patients, and 178 lesions were finally diagnosed as metastases. EOB-MRI had a higher sensitivity (0.837 vs 0.949), while CE-US had a higher specificity and positive predictive value (PPV) (0.982 and 0.993 vs 0.911 and 0.971, respectively) in the diagnosis of liver metastasis. CE-US with defect reperfusion imaging had a higher diagnostic performance than EOB-MRI (0.866 vs 0.667) in the differentiation between liver metastasis and abscess.

CONCLUSION

EOB-MRI had a higher sensitivity than CE-US for diagnosing liver metastasis in patients with pancreatic cancer, but CE-US following CH-EUS demonstrated a higher specificity and PPV than EOB-MRI and was especially useful in the differentiation between liver metastasis and abscess.

Quantitative diffusion MRI of the abdomen and pelvis

Diffusion MRI has enormous potential and utility in the evaluation of various abdominal and pelvic disease processes including cancer and noncancer imaging of the liver, prostate, and other organs. Quantitative diffusion MRI is based on acquisitions with multiple diffusion encodings followed by quantitative mapping of diffusion parameters that are sensitive to tissue microstructure. Compared to qualitative diffusion-weighted MRI, quantitative diffusion MRI can improve standardization of tissue characterization as needed for disease detection, staging, and treatment monitoring. However, similar to many other quantitative MRI methods, diffusion MRI faces multiple challenges including acquisition artifacts, signal modeling limitations, and biological variability. In abdominal and pelvic diffusion MRI, technical acquisition challenges include physiologic motion (respiratory, peristaltic, and pulsatile), image distortions, and low signal-to-noise ratio. If unaddressed, these challenges lead to poor technical performance (bias and precision) and clinical outcomes of quantitative diffusion MRI. Emerging and novel technical developments seek to address these challenges and may enable reliable quantitative diffusion MRI of the abdomen and pelvis. Through systematic validation in phantoms, volunteers, and patients, including multicenter studies to assess reproducibility, these emerging techniques may finally demonstrate the potential of quantitative diffusion MRI for abdominal and pelvic imaging applications.

Imaging and its Impact on Defining the Oligometastatic State

Successful treatment of oligometastatic disease (OMD) is facilitated through timely detection and localization of disease, both at the time of initial diagnosis (synchronous OMD) and following the initial therapy (metachronous OMD). Hence, imaging plays an indispensable role in management of patients with OMD. However, the challenges and complexities of OMD management are also reflected in the imaging of this entity. While innovations and advances in imaging technology have made a tremendous impact in disease detection and management, there remain substantial and unaddressed challenges for earlier and more accurate establishment of OMD state. This review will provide an overview of the available imaging modalities and their inherent strengths and weaknesses, with a focus on their role and potential in detection and evaluation of OMD in different organ systems. Furthermore, we will review the role of imaging in evaluation of OMD for malignancies of various primary organs, such as the lung, prostate, colon/rectum, breast, kidney, as well as neuroendocrine tumors and gynecologic malignancies. We aim to provide a practical overview about the utilization of imaging for clinicians who play a role in the care of those with, or at risk for OMD.

Comparison of ferumoxytol- and gadolinium chelate-enhanced MRI for assessment of sarcomas in children and adolescents

OBJECTIVES

We compared the value of ferumoxytol (FMX)- and gadolinium (Gd)-enhanced MRI for assessment of sarcomas in paediatric/adolescent patients and hypothesised that tumour size and morphological features can be equally well assessed with both protocols.

METHODS

We conducted a retrospective study of paediatric/adolescent patients with newly diagnosed bone or soft tissue sarcomas and both pre-treatment FMX- and Gd-MRI scans, which were maximal 4 weeks apart. Both protocols included T1- and T2-weighted sequences. One reader assessed tumour volumes, signal-to-noise ratios (SNR) of the primary tumour and adjacent tissues and contrast-to-noise ratios (CNR) of FMX- and Gd-MRI scans. Additionally, four readers scored FMX- and Gd-MRI scans according to 15 diagnostic parameters, using a Likert scale. The results were pooled across readers and compared between FMX- and Gd-MRI scans. Statistical methods included multivariate analyses with different models.

RESULTS

Twenty-two patients met inclusion criteria (16 males, 6 females; mean age 15.3 ± 5.0). Tumour volume was not significantly different on T1-LAVA (p = 0.721), T1-SE (p = 0.290) and T2-FSE (p = 0.609) sequences. Compared to Gd-MRI, FMX-MRI demonstrated significantly lower tumour SNR on T1-LAVA (p < 0.001), equal tumour SNR on T1-SE (p = 0.104) and T2-FSE (p = 0.305), significantly higher tumour-to-marrow CNR (p < 0.001) on T2-FSE as well as significantly higher tumour-to-liver (p = 0.021) and tumour-to-vessel (p = 0.003) CNR on T1-LAVA images. Peritumoural and marrow oedema enhanced significantly more on Gd-MRI compared to FMX-MRI (p < 0.001/p = 0.002, respectively). Tumour thrombi and neurovascular bundle involvement were assessed with a significantly higher confidence on FMX-MRI (both p < 0.001).

CONCLUSIONS

FMX-MRI provides equal assessment of the extent of bone and soft tissue sarcomas compared to Gd-MRI with improved tumour delineation and improved evaluation of neurovascular involvement and tumour thrombi. Therefore, FMX-MRI is a possible alternative to Gd-MRI for tumour staging in paediatric/adolescent sarcoma patients.

KEY POINTS

• Ferumoxytol can be used as an alterative to gadolinium chelates for MRI staging ofpaediatric sarcomas. • Ferumoxytol-enhanced MRI provides equal assessment of tumour size and other diagnostic parameters compared to gadolinium chelate-enhanced MRI. • Ferumoxytol-enhanced MRI provides improved delineation of sarcomas from bone marrow, liver and vessels compared to gadolinium chelate-enhanced MRI.

Diagnostic performance of contrast-enhanced ultrasound and magnetic resonance imaging for detecting colorectal liver metastases: A systematic review and meta-analysis

OBJECTIVES

To determine the diagnostic performance of contrast-enhanced ultrasound, diffusion-weighted magnetic resonance imaging and contrast-enhanced magnetic resonance imaging for detecting colorectal liver metastases.

METHODS

We performed comprehensive searches of the MEDLINE, EMBASE, and Cochrane Library databases to identify studies reporting the per-lesion diagnostic accuracy of contrast-enhanced ultrasound, diffusion-weighted magnetic resonance imaging, and contrast-enhanced magnetic resonance imaging for detecting colorectal liver metastases. Studies published between January 2003 and December 2018 with reference standards, including histopathology and intraoperative observation, and/or follow-up, were included. Sources of bias were assessed using the QUADAS-2 tool. A linear mixed-effects regression model was used to determine sensitivity estimates.

RESULTS

Overall, 47 articles were included. The sensitivity estimates for contrast-enhanced ultrasound, diffusion-weighted magnetic resonance imaging, and contrast-enhanced magnetic resonance imaging for detecting colorectal liver metastases were 85.3%, 83.0%, and 90.1%, respectively. For lesions ≥10 mm in diameter, the sensitivities were 93.1%, 92.9%, and 94.5%, respectively. In 21 articles using histopathology as the only reference standard, the sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and diagnostic odds ratio for contrast-enhanced ultrasound/contrast-enhanced magnetic resonance imaging were 86%/91%, 91%/95%, 9.2/16.6, 0.15/0.10, and 61/170, respectively.

CONCLUSIONS

CEUS showed a diagnostic ability comparable to that of DWI and CEMRI, particularly for lesions ≥10 mm in diameter.

Detection of liver metastases on gadobenate dimeglumine-enhanced MRI: systematic review, meta-analysis, and similarities with gadoxetate-enhanced MRI

OBJECTIVES

To determine the sensitivity and positive predictive value (PPV) of gadobenate-enhanced MR imaging for the detection of liver metastases.

METHODS

This systematic review and meta-analysis was conducted according to PRISMA guidelines. A comprehensive search (EMBASE, PubMed) was performed to identify relevant articles up to December 2017. Studies eligible for inclusion were performed using appropriate methodology with complete verification by means of histopathology, intraoperative observation and/or follow-up, and sufficient information to permit determination of true-positive (TP), false-negative (FN), and false-positive (FP) values. Sources of bias were assessed using the QUADAS-2 tool. An inverse variance-weighted random-effects model was used to obtain sensitivity and PPV estimates. Information was analyzed and presented using Cochran's Q statistic, funnel plots, and modified Deeks' analysis.

RESULTS

Ten articles (256 patients, 562 metastases) were included. Sensitivity estimates for pre-contrast (unenhanced) imaging, gadobenate-enhanced dynamic imaging, and combined unenhanced, dynamic, and delayed hepatobiliary phase imaging for detecting liver metastases on a per-lesion basis were 77.8% (95% CI 71.4-84.3%, 7 assessments), 88.1% (95% CI, 84.0-92.2%, 13 assessments), and 95.1% (95% CI 93.1-97.1%, 15 assessments), respectively. The addition of hepatobiliary phase images significantly improved the detection of liver metastases. The overall PPV was 90.9% (95% CI 86.6-95.1%, 11 assessments). Deeks' funnel analysis revealed no association between sample size and sensitivity (β = 0.02, p = 0.814) indicating no significant publication bias.

CONCLUSIONS

Gadobenate-enhanced MR imaging has high sensitivity and PPV for the detection of liver metastases on a per-lesion basis. The sensitivity and PPV for detection is comparable to reported values for the pure liver-specific agent gadoxetate.

KEY POINTS

• Gadobenate dimeglumine is a hepatobiliary MR contrast agent that permits acquisition of contrast-enhanced liver images during the immediate post-injection dynamic phase, like any extracellular agent, and in the delayed hepatobiliary phase, after specific uptake by the hepatocytes. • The hepatobiliary phase improves detection of liver metastases when compared either to pre-contrast unenhanced images alone or to pre-contrast + gadobenate-enhanced dynamic phase images. • The meta-analysis showed an overall sensitivity of 95.1% and PPV of 90.9% of gadobenate-enhanced MRI for the detection of metastases, when based on the evaluation of all available acquisitions.

Is MRI of the Liver Needed During Routine Preoperative Workup for Colorectal Cancer?

BACKGROUND

The clinical efficacy of gadoxetic acid-enhanced liver MRI as a routine preoperative procedure for all patients with colorectal cancer remains unclear.

OBJECTIVE

The purpose of this study was to evaluate the efficacy of preoperative gadoxetic acid-enhanced liver MRI for the diagnosis of liver metastasis in patients with colorectal cancer.

DESIGN

This was a retrospective analysis from a prospective cohort database.

SETTINGS

All of the patients were from a subspecialty practice at a tertiary referral hospital.

PATIENTS

Patients who received preoperative gadoxetic acid-enhanced liver MRI after CT and attempted curative surgery for colorectal cancer were included.

MAIN OUTCOME MEASURES

The number of equivocal hepatic lesions based on CT and gadoxetic acid-enhanced liver MRI and diagnostic use of the gadoxetic acid-enhanced liver MRI were measured.

RESULTS

We reviewed the records of 690 patients with colorectal cancer. Equivocal hepatic lesions were present in 17.2% of patients based on CT and in 4.5% based on gadoxetic acid-enhanced liver MRI. Among 496 patients with no liver metastasis based on CT, gadoxetic acid-enhanced liver MRI detected equivocal lesions in 15 patients and metastasis in 3 patients. Among 119 patients who had equivocal liver lesions on CT, gadoxetic acid-enhanced liver MRI indicated hepatic lesions in 103 patients (86.6%), including 90 with no metastasis and 13 with metastasis. Among 75 patients who had liver metastasis on CT, gadoxetic acid-enhanced liver MRI indicated that the hepatic lesions in 2 patients were benign, in contrast to CT findings. The initial surgical plans for hepatic lesions according to CT were changed in 17 patients (3%) after gadoxetic acid-enhanced liver MRI.

LIMITATIONS

This study was limited by its retrospective design.

CONCLUSIONS

The clinical efficacy of gadoxetic acid-enhanced liver MRI as a routine preoperative procedure for all patients with colorectal cancer is low, in spite of its high diagnostic value for detecting liver metastasis. However, this study showed gadoxetic acid-enhanced liver MRI was helpful in characterizing equivocal hepatic lesions identified in CT and could lead to change in treatment plans for some patients. See Video Abstract at http://links.lww.com/DCR/A420.

Accuracy of Whole-Body DWI for Metastases Screening in a Diverse Group of Malignancies: Comparison With Conventional Cross-Sectional Imaging and Nuclear Scintigraphy

OBJECTIVE

The purpose of this study is to assess the role of whole-body (WB) DWI as a screening modality for the detection of metastases and to compare it to conventional cross-sectional imaging modalities or nuclear scintigraphy in a population with various histopathologic malignancies.

SUBJECTS AND METHODS

WB DWI and conventional imaging (CT, MRI, or scintigraphy) were performed for patients with known malignancies for metastatic workup, and these patients were followed up for a period of 1 year. Two radiologists assessed WB DW images separately, and conventional images were assessed by the senior radiologist. The metastatic lesions were classified into four regions: liver, lung, skeletal system, and lymph nodes. The reference standard was considered on the basis of histopathologic confirmation or clinical follow-up of the metastatic lesions.

RESULTS

WB DWI was slightly inferior to conventional imaging modalities for the detection of hepatic metastases (sensitivity, 86.6% vs 93.3%; specificity, 91.6% vs 95.8%; and accuracy, 89.7% vs 94.8%) and skeletal metastases (sensitivity, 81.8% vs 89.4%; specificity, 86.4% vs 94.3%; and accuracy, 85.2% vs 93.0%); however, the differences were not statistically significant (p = 0.625 for hepatic metastases and p = 0.0953 for skeletal metastases, McNemar test). WB DWI was statistically significantly inferior to conventional imaging for the detection of lymph node metastases (sensitivity, 74.0% vs 81.5%; specificity, 87.9% vs 90.1%; accuracy, 81.4% vs 86.0%; p = 0.0389). WB DWI was statistically significantly inferior to conventional imaging for the detection of pulmonary metastases (sensitivity, 33.3% vs 100.0%; specificity, 90.9% vs 100.0%; accuracy, 60.8% vs 100.0%; p = 0.045).

CONCLUSION

WB DWI can be used for screening hepatic and skeletal metastases, but its reliability as the sole imaging sequence for the detection of lymph nodal and pulmonary metastases is poor and, at present, it cannot replace conventional imaging modalities.

Nanomaterials for In Vivo Imaging

In vivo imaging, which enables us to peer deeply within living subjects, is producing tremendous opportunities both for clinical diagnostics and as a research tool. Contrast material is often required to clearly visualize the functional architecture of physiological structures. Recent advances in nanomaterials are becoming pivotal to generate the high-resolution, high-contrast images needed for accurate, precision diagnostics. Nanomaterials are playing major roles in imaging by delivering large imaging payloads, yielding improved sensitivity, multiplexing capacity, and modularity of design. Indeed, for several imaging modalities, nanomaterials are now not simply ancillary contrast entities, but are instead the original and sole source of image signal that make possible the modality's existence. We address the physicochemical makeup/design of nanomaterials through the lens of the physical properties that produce contrast signal for the cognate imaging modality-we stratify nanomaterials on the basis of their (i) magnetic, (ii) optical, (iii) acoustic, and/or (iv) nuclear properties. We evaluate them for their ability to provide relevant information under preclinical and clinical circumstances, their in vivo safety profiles (which are being incorporated into their chemical design), their modularity in being fused to create multimodal nanomaterials (spanning multiple different physical imaging modalities and therapeutic/theranostic capabilities), their key properties, and critically their likelihood to be clinically translated.

Imaging oligometastatic cancer before local treatment

With the advent of novel treatment strategies to help widen the therapeutic window for patients with oligometastatic cancer, improved biomarkers are needed to reliably define patients who can benefit from these treatments. Multimodal imaging is one such option and should be optimised to comprehensively assess metastatic sites, disease burden, and response to neoadjuvant treatment in each disease setting. These features will probably remain important prognostic biomarkers, and are crucial in planning multidisciplinary treatment. There are opportunities to extract additional phenotypic information from conventional imaging, while novel imaging techniques can also reveal specific aspects of tumour biology. Imaging can both characterise and localise the phenotypic heterogeneity of multiple tumour sites. Novel approaches to existing imaging datasets and correlation with tumour biology will be important in realising the potential of imaging to guide treatment in the oligometastatic setting. In this Personal View, we discuss the current status and future directions of imaging before treatment in patients with extracranial oligometastases.

Imaging of Liver Tumors Using Surface-Enhanced Raman Scattering Nanoparticles

Complete surgical resection is the ideal first-line treatment for most liver malignancies. This goal would be facilitated by an intraoperative imaging method that enables more precise visualization of tumor margins and detection of otherwise invisible microscopic lesions. To this end, we synthesized silica-encapsulated surface-enhanced Raman scattering (SERS) nanoparticles (NPs) that act as a molecular imaging agent for liver malignancies. We hypothesized that, after intravenous administration, SERS NPs would avidly home to healthy liver tissue but not to intrahepatic malignancies. We tested these SERS NPs in genetically engineered mouse models of hepatocellular carcinoma and histiocytic sarcoma. After intravenous injection, liver tumors in both models were readily identifiable with Raman imaging. In addition, Raman imaging using SERS NPs enabled detection of microscopic lesions in liver and spleen. We compared the performance of SERS NPs to fluorescence imaging using indocyanine green (ICG). We found that SERS NPs delineate tumors more accurately and are less susceptible to photobleaching. Given the known advantages of SERS imaging, namely, high sensitivity and specific spectroscopic detection, these findings hold promise for improved resection of liver cancer.

Current status of imaging and emerging techniques to evaluate liver metastases from colorectal carcinoma

Colorectal cancer is the third most common cancer diagnosed in both men and women in the United States. Liver is a common site of tumor spread and in approximately 30% of the cases; synchronous liver disease is present at the time of diagnosis. Early detection of liver metastases is crucial to appropriately select patients who may benefit from hepatic resection among those needing chemotherapy, to improve 5-year survival. Advances in imaging techniques have contributed greatly to the management of these patients. Multidetector computed tomography is the most useful test for initial staging and in posttreatment surveillance settings. Magnetic resonance imaging is considered superior to multidetector computed tomography and positron emission tomography for the detection and characterization of small lesions and for liver evaluation in the presence of background fatty liver changes. Positron emission tomography-computed tomography has a problem-solving role in the detection of distant metastasis and in posttreatment evaluation. The advanced imaging methods also serve a role in selecting appropriate patients for radiologically targeted therapies and in monitoring response to conventional and novel therapies.

Preoperative evaluation of colorectal liver metastases: comparison between gadoxetic acid-enhanced 3.0-T MRI and contrast-enhanced MDCT with histopathological correlation

OBJECTIVES

The aim of this prospective study was to compare the diagnostic performance of 64-row MDCT and gadoxetic-acid-enhanced MRI at 3.0 T in patients with colorectal liver metastases in correlation with histopathological findings.

METHODS

Lesions detected at MDCT and MRI were interpreted by three blinded readers and compared with histopathological workup as the term of reference. Two subgroups of lesions were additionally evaluated: (1) metastases smaller than 10 mm and (2) lesions in patients with and without steatosis of the liver, assessed histopathologically.

RESULTS

Surgery and histopathological workup revealed 81 colorectal liver metastases in 35 patients and diffuse metastatic involvement in 3 patients. In a lesion-by-lesion analysis, significant sensitivity differences could only be found for reader 1 (P = 0.035) and reader 3 (P = 0.003). For segment-based evaluation, MRI was more sensitive only for reader 3 (P = 0.012). The number of false-positive results ranged from 3 to 12 for MDCT and 8 to 11 for MRI evaluation. In the group of small lesions, the sensitivity differed significantly between both methods (P = 0.003). In patients with hepatic steatosis, MRI showed a trend toward better performance than MDCT, but without statistical performance.

CONCLUSIONS

The 3.0-T MRI with liver-specific contrast agents is the preferred investigation in the preoperative setting, especially for the assessment of small colorectal liver metastases.

KEY POINTS

• Potential surgical treatment requires accurate radiological assessment of colorectal liver metastases • Magnetic resonance imaging with gadoxetic acid is the preferred imaging investigation. • MRI is better than multidetector CT for detecting small liver metastases.

Negatively charged superparamagnetic iron oxide nanoparticles: a new blood-pooling magnetic resonance contrast agent

PURPOSE

Our purpose was to investigate the utility of superparamagnetic iron-oxide nanoparticles (SPIO) as a blood-pooling contrast agent at magnetic resonance imaging (MRI).

MATERIALS AND METHODS

We studied four contrast agents: carboxymethyl-diethylaminoethyl dextran magnetite SPIO (CMEADM-S, diameter 54 nm), negatively charged CMEADM ultrasmall SPIO (CMEADM-U, 32 nm), alkali-treated dextran magnetite SPIO (ATDM-S, 55 nm), and ATDM ultrasmall SPIO (ATDM-U, 28 nm) carrying a neutral charge. Each contrast agent (80 μmol/kg) was injected intraperitoneally into apolipoprotein E (apoE) mice and the tissue iron concentration was measured 30-, 60-, 180-, and 300-min later by nuclear MR. For MR angiographic (MRA) evaluation, we injected the agents into the auricular vein of four groups of 15 rabbits. Immediately and 30-, 60-, 180-, and 300-min later, three rabbits from each group were subjected to MRI. The organ/background signal ratio (SR) was calculated. Statistical analyses were performed with Tukey's honestly significant difference (HSD) test.

RESULTS

At 60 and 180 min, blood-iron concentration of CMEADM-U was significantly different from other contrast agents. In the abdominal aorta and inferior vena cava, SR of CMEADM-U was higher at 180 and 300 min than of the other contrast agents. In the thoracic aorta, there was no difference in SR at 300 min between CMEADM-U and CMEADM-S.

CONCLUSION

Negatively charged SPIO nanoparticles may be useful as a blood-pooling contrast agent.

Can diffusion-weighted magnetic resonance imaging (DW-MRI) alone be used as a reliable sequence for the preoperative detection and characterisation of hepatic metastases? A meta-analysis

PURPOSE

To perform a meta-analysis of all available studies of the diagnostic performance of diffusion-weighted magnetic resonance imaging (DW-MRI) in patients with hepatic metastases.

METHODS

Databases including MEDLINE and EMBASE were searched for relevant original articles published from January 2000 to February 2012. We determined sensitivities and specificities across studies, calculated positive and negative likelihood ratios (LR+ and LR-), diagnostic odds ratio (DOR) and constructed summary receiver operating characteristic curves using hierarchical regression models.

RESULTS

Across 11 studies (537 patients), DW-MRI sensitivity was 0.87 (95%confidence interval (CI), 0.80, 0.91) and specificity was 0.90 (95%CI, 0.86, 0.93). Overall, LR+ was 8.52 (95%CI, 6.17, 11.77), LR- was 0.15 (95%CI, 0.10, 0.22) and DOR was 57.36 (95%CI, 38.29, 85.93). In studies in which both DW-MRI and contrast-enhanced magnetic resonance imaging (CE-MRI) were performed, the comparison of DW-MRI performance with that of CE-MRI suggested no major differences against these two methods (p>0.05). DW-MRI combined CE-MRI had higher sensitivity and specificity than DW-MRI alone (97% versus 86% and 91% versus 90%, respectively) (p<0.05). The subgroup in which DW-MRI examinations were performed with a 3.0 Tesla (T) device had higher pooled specificity (0.91, 95%CI, 0.88-0.95) than the subgroup of DW-MRI with 1.5 T device (0.81, 95%CI, 0.67, 0.94) (p<0.05). Average lesion size (≤ 1.5 cm versus >1.5cm) did not influence the diagnostic accuracy of the test (p>0.05).

CONCLUSION

Our results demonstrate DW-MRI has good diagnostic performance in the overall evaluation of hepatic metastases and equivalent to CE-MRI. Combination of CE-MRI and DW-MRI can improve the diagnostic accuracy of magnetic resonance (MR) imaging. Our study further confirms that DW-MRI can accurately detect hepatic metastases regardless of the lesion size. It is suggested to perform DW-MRI by 3.0 T devices, which might have high specificity to identify liver metastases.

Imaging diagnosis of colorectal liver metastases

Rapid advances in imaging technology have improved the detection, characterization and staging of colorectal liver metastases. Multi-modality imaging approach is usually the more useful in diagnosis colorectal liver metastases. It is well established that hepatic resection improves the long-term prognosis of many patients with liver metastases. However, incomplete resection does not prolong survival, so knowledge of the exact extent of intra-hepatic disease is crucially important in determining patient management and outcome. The diagnosis of liver metastases relies first and totally on imaging to decide which patients may be surgical candidates. This review will discuss the imaging options and their appropriate indications. Imaging and evaluating of colorectal liver metastases (CRLM) have been performed with contrast-enhanced ultrasound, multi-detector computed tomography, magnetic resonance imaging (MRI) with extra-cellular contrast media and liver-specific contrast media MRI, and positron emission tomography/computed tomography. This review will concentrate on the imaging approach of CRLM, and also discuss certain characteristics of some liver lesions. We aim to highlight the advantages of each imaging technique, as well as underscoring potential pitfalls and limitations.

Comparison of gadoxetic acid-enhanced dynamic imaging and diffusion-weighted imaging for the preoperative evaluation of colorectal liver metastases

PURPOSE

To retrospectively compare the diagnostic accuracy for the detection of colorectal liver metastases between gadoxetic acid-enhanced MRI (EOB-MRI) and diffusion-weighted imaging (DWI) on 3.0 Tesla (T) system, and then to determine whether a combination of the two techniques may improve the diagnostic performance.

MATERIALS AND METHODS

Forty-seven patients underwent MR imaging at 3.0T, including DWI (DWI set) and dynamic and hepatobiliary phase EOB-MRI (EOB set) for the preoperative evaluation of colorectal liver metastases. All suspicious metastases were confirmed by hepatic surgery. Two blinded readers independently reviewed three different image sets, which consisted of DWI set, EOB set, and combined set. The accuracy was assessed by the area (Az) under the alternative-free response receiver operating characteristic curve, and the sensitivity and positive predictive value (PPV) were calculated.

RESULTS

We found a total of 78 confirmed colorectal liver metastases in 42 of 47 patients. Each reader noted higher diagnostic accuracy of combined set of EOB-MRI and DWI than DWI set and EOB set, without statistical significance. Regardless of the size of colorectal liver metastasis, each reader detected significantly more metastases on combined set than on DWI set, and PPV was significantly higher with DWI set than with EOB set or with combined set for one reader.

CONCLUSION

EOB-MRI was more useful for the detection of colorectal liver metastases, while DWI was more useful for their characterization. The combination of EOB-MRI and DWI showed significantly higher accuracy and sensitivity for the preoperative detection of small colorectal liver metastases than DWI.