Surgically staged focal liver lesions: accuracy and reproducibility of dual-phase helical CT for detection and characterization

Multi-phase features interaction transformer network for liver tumor segmentation and microvascular invasion assessment in contrast-enhanced CT

Precise segmentation of liver tumors from computed tomography (CT) scans is a prerequisite step in various clinical applications. Multi-phase CT imaging enhances tumor characterization, thereby assisting radiologists in accurate identification. However, existing automatic liver tumor segmentation models did not fully exploit multi-phase information and lacked the capability to capture global information. In this study, we developed a pioneering multi-phase feature interaction Transformer network (MI-TransSeg) for accurate liver tumor segmentation and a subsequent microvascular invasion (MVI) assessment in contrast-enhanced CT images. In the proposed network, an efficient multi-phase features interaction module was introduced to enable bi-directional feature interaction among multiple phases, thus maximally exploiting the available multi-phase information. To enhance the model's capability to extract global information, a hierarchical transformer-based encoder and decoder architecture was designed. Importantly, we devised a multi-resolution scales feature aggregation strategy (MSFA) to optimize the parameters and performance of the proposed model. Subsequent to segmentation, the liver tumor masks generated by MI-TransSeg were applied to extract radiomic features for the clinical applications of the MVI assessment. With Institutional Review Board (IRB) approval, a clinical multi-phase contrast-enhanced CT abdominal dataset was collected that included 164 patients with liver tumors. The experimental results demonstrated that the proposed MI-TransSeg was superior to various state-of-the-art methods. Additionally, we found that the tumor mask predicted by our method showed promising potential in the assessment of microvascular invasion. In conclusion, MI-TransSeg presents an innovative paradigm for the segmentation of complex liver tumors, thus underscoring the significance of multi-phase CT data exploitation. The proposed MI-TransSeg network has the potential to assist radiologists in diagnosing liver tumors and assessing microvascular invasion.

Radiomics Study for Differentiating Focal Hepatic Lesions Based on Unenhanced CT Images

Objectives

To investigate the feasibility of computer-aided discriminative diagnosis among hepatocellular carcinoma (HCC), hepatic metastasis, hepatic hemangioma, hepatic cysts, hepatic adenoma, and hepatic focal nodular hyperplasia, based on radiomics analysis of unenhanced CT images.

Methods

452 patients with 77 with HCC, 104 with hepatic metastases, 126 with hepatic hemangioma, 99 with hepatic cysts, 24 with FNH, 22 with HA, who underwent CT examination from 2016 to 2018, were included. Radcloud Platform was used to extract radiomics features from manual delineation on unenhanced CT images. Most relevant radiomic features were selected from 1409 via LASSO (least absolute shrinkage and selection operator). The whole dataset was divided into training and testing set with the ratio of 8:2 using computer-generated random numbers. Support Vector Machine (SVM) was used to establish the classifier.

Results

The computer-aided diagnosis model was established based on radiomic features of unenhanced CT images. 27 optimal discriminative features were selected to distinguish the six different histopathological types of all lesions. The classifiers had good diagnostic performance, with the area under curve (AUC) values greater than 0.900 in training and validation groups. The overall accuracy of the training and testing set about differentiating the six different histopathological types of all lesions was 0.88 and 0.76 respectively. 34 optimal discriminative were selected to distinguish the benign and malignant tumors. The overall accuracy in the training and testing set was 0.89and 0.84 respectively.

Conclusions

The computer-aided discriminative diagnosis model based on unenhanced CT images has good clinical potential in distinguishing focal hepatic lesions with noninvasive radiomic features.

Clinical added value of MRI to CT in patients scheduled for local therapy of colorectal liver metastases (CAMINO): study protocol for an international multicentre prospective diagnostic accuracy study

BACKGROUND

Abdominal computed tomography (CT) is the standard imaging method for patients with suspected colorectal liver metastases (CRLM) in the diagnostic workup for surgery or thermal ablation. Diffusion-weighted and gadoxetic-acid-enhanced magnetic resonance imaging (MRI) of the liver is increasingly used to improve the detection rate and characterization of liver lesions. MRI is superior in detection and characterization of CRLM as compared to CT. However, it is unknown how MRI actually impacts patient management. The primary aim of the CAMINO study is to evaluate whether MRI has sufficient clinical added value to be routinely added to CT in the staging of CRLM. The secondary objective is to identify subgroups who benefit the most from additional MRI.

METHODS

In this international multicentre prospective incremental diagnostic accuracy study, 298 patients with primary or recurrent CRLM scheduled for curative liver resection or thermal ablation based on CT staging will be enrolled from 17 centres across the Netherlands, Belgium, Norway, and Italy. All study participants will undergo CT and diffusion-weighted and gadoxetic-acid enhanced MRI prior to local therapy. The local multidisciplinary team will provide two local therapy plans: first, based on CT-staging and second, based on both CT and MRI. The primary outcome measure is the proportion of clinically significant CRLM (CS-CRLM) detected by MRI not visible on CT. CS-CRLM are defined as liver lesions leading to a change in local therapeutical management. If MRI detects new CRLM in segments which would have been resected in the original operative plan, these are not considered CS-CRLM. It is hypothesized that MRI will lead to the detection of CS-CRLM in ≥10% of patients which is considered the minimal clinically important difference. Furthermore, a prediction model will be developed using multivariable logistic regression modelling to evaluate the predictive value of patient, tumor and procedural variables on finding CS-CRLM on MRI.

DISCUSSION

The CAMINO study will clarify the clinical added value of MRI to CT in patients with CRLM scheduled for local therapy. This study will provide the evidence required for the implementation of additional MRI in the routine work-up of patients with primary and recurrent CRLM for local therapy.

TRIAL REGISTRATION

The CAMINO study was registered in the Netherlands National Trial Register under number NL8039 on September 20th 2019.

Disappearing liver metastases: A systematic review of the current evidence

Advances in systemic chemotherapy have resulted in a significant increase in the reported response rates of colorectal liver metastases (CRLM) over time. Although radiologic response is usually prognostic of favorable outcomes, complete shrinkage of CRLM after chemotherapy, namely "disappearing liver metastases" (DLMs) poses significant therapeutic dilemmas. A systematic review of the literature was conducted to evaluate the existing evidence on the imaging and management of patients with DLMs using the PubMed (Medline), Embase and Cochrane library through December 21st, 2018. The following algorithm was used: "(disappearing OR vanishing OR missing OR (residual tiny)) AND ((liver OR hepatic) AND (metastasis OR metastases OR metastatic OR secondary))." From the 225 records retrieved, 15 studies were finally deemed eligible. A total of 479 patients with DLMs with a median age of 59.5 years (range, 30-83) were identified. Median number of DLM per patient ranged from 1 to 8.8. Median size of LMs prior to chemotherapy was 1.07 cm (range 0.3-3.5). The systemic treatment used to achieve DLMs included systemic chemotherapy alone (only 2 studies) or in combination with targeted agents (11 studies). The median number of chemotherapy cycles in the included studies was 7.8 (range 6-12). Identified factors predisposing to the development of DLM were small size (<2 cm), increased number of treatment cycles, oxaliplatin-based therapy, increased number of CRLM (≥3) and synchronous CRLM. Baseline and preoperative MRI with iv contrast showed the highest sensitivity for DLM detection. Fiducial placement facilitated pre- and intra-operative identification of DLM. Although resection of DLM decreased the local recurrence risk, there was no clearly demonstrated survival benefit after resecting all sites of disappearing lesions. Future randomized clinical trials are highly encouraged to provide strict, evidence-based recommendations for the treatment of patients with DLM.

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.

Small intrahepatic peripheral cholangiocarcinomas as mimics of hepatocellular carcinoma in multiphasic CT

PURPOSE

Liver transplant guidelines for diagnosing hepatocellular carcinoma (HCC) do not mandate pathologic confirmation; instead, 'classic' imaging features alone are deemed satisfactory. Intrahepatic peripheral mass forming cholangiocarcinoma (IHPMCC) is a relative contraindication for transplantation due to high rate of recurrence and poor prognosis. This study examines the imaging findings of IHPMCC, to aid in the identification and differentiation from potentially confounding cases of HCC.

METHODS

After IRB approval, 43 tissue-proven cases of IHPMCC on multiphase CT were retrospectively reviewed by 2 fellowship-trained radiologists. Tumor size, presence of cirrhosis, tumor capsule, vascular invasion, tumor markers, and enhancement pattern were assessed. A grading system was assigned as determined by enhancement pattern to background liver on arterial, portal venous, and equilibrium phases, ranging from typical HCC to typical IHPMCC enhancement pattern.

RESULTS

Analysis based on our grading system shows 5 (11.6%) tumors demonstrating grade 1-2 enhancement, 9 (21%) grade 3-4 enhancement, and 29 (67.4%) grade 5 enhancement. Kruskal-Wallis test comparing CA19-9 between the five groups, Wilcoxin rank-sum test comparing tumor markers with presence or absence of tumor capsule, vascular invasion and cirrhosis, and nonparametric Pearson's correlation coefficient comparing tumor markers to tumor size were not statistically significant (p > 0.05).

CONCLUSION

Typical enhancement pattern of IHPMCC consisting of arterial phase hypoenhancement with progressive, centripetal-delayed enhancement is present in the majority of cases (68%). Five cases (11.7%) showed enhancement features potentially mimicking HCC, all of which are under 3.5 cm in size. Thus, small hyperenhancing lesions in a cirrhotic liver should be carefully scrutinized in light of differing therapy options from HCC, particularly in transplant situations.

Intraoperative ultrasonography and surgical strategy in hepatic resection: What difference does it make?

BACKGROUND

With modern advancements in preoperative imaging for liver surgery, intraoperative ultrasonography (IOUS) may be perceived as superfluous. Our aim was to determine if IOUS provides new information that changes surgical strategy in hepatic resection.

METHODS

We retrospectively analyzed 121 consecutive liver resections performed at a single institution. Preoperative computed tomography and/or magnetic resonance imaging determined the initial surgical strategy. The size, location and number of lesions were compared between IOUS and preoperative imaging. Reviewing the operative report helped determine if new IOUS findings led to changes in surgical strategy. Pathology reports were analyzed for margins.

RESULTS

Of 121 procedures analyzed, IOUS was used in 88. It changed the surgical plan in 15 (17%) cases. Additional tumours were detected in 10 (11%) patients. A change in tumour size and location were detected in 2 (2%) and 3 (4%) patients, respectively. Surgical plans were altered in 7 (8%) cases for reasons not related to IOUS. There was no significant difference (p = 0.74) in average margin length between the IOUS and non-IOUS groups (1.09 ± 1.18 cm v. 1.18 ± 1.05 cm).

CONCLUSION

Surgical strategy was altered owing to IOUS results in a substantial number of cases, and IOUS-guided resection planes resulted in R0 resections in nearly all procedures. The best operative plan in hepatic resection includes IOUS.

Comparative effectiveness in hepatic malignancies

The benefits of applying comparative effectiveness research (CER) strategies to the management of cancer are important. As the incidence of cancer increases both in the United States and worldwide, accurate analysis of which tests and treatments should be applied in which situations is critical, both in terms of measurable and meaningful clinical outcomes and health care costs. In the last 20 years alone, multiple controversies have arisen in the diagnosis and treatment of primary and metastatic tumors of the liver, making the management of liver malignancies a prime example of CER. Contributing factors to the development of these controversies include improvements in molecular characterization of these diseases and technological advances in surgery and radiology. The relative speed of these advances has outpaced data from clinical trials, in turn making robust data to inform clinical practice lacking. Indeed, many of the current treatment recommendations for the management of liver malignancies are based primarily on retrospective data. We herein review select CER issues concerning select decision-making topics in the management of liver malignancies.

Advances in understanding of colorectal liver metastasis and implications for the clinic

Colorectal cancer is one of the most common cancers in both the USA and Europe. Over the course of diagnosis, treatment and surveillance, up to 50% of these patients will develop metastases to their liver. In the past 20 years alone, there have been multiple advances in the management of these colorectal metastases to the liver. These advances have been made in characterization of these tumors, diagnosis and in treatment, both locally and systemically. Because of this progress, there are subsets of patients with this stage IV disease who are cured of their disease. While significant progress has been made, there still exist limitations in the management of metastatic colorectal cancer to the liver. This review outlines current strategies and highlights recent advances in the management of colorectal liver metastases.

Computed tomography: revolutionizing the practice of medicine for 40 years

Computed tomography (CT) has had a profound effect on the practice of medicine. Both the spectrum of clinical applications and the role that CT has played in enhancing the depth of our understanding of disease have been profound. Although almost 90 000 articles on CT have been published in peer-reviewed journals over the past 40 years, fewer than 5% of these have been published in Radiology. Nevertheless, these almost 4000 articles have provided a basis for many important medical advances. By enabling a deepened understanding of anatomy, physiology, and pathology, CT has facilitated key advances in the detection and management of disease. This article celebrates this breadth of scientific discovery and development by examining the impact that CT has had on the diagnosis, characterization, and management of a sampling of major health challenges, including stroke, vascular diseases, cancer, trauma, acute abdominal pain, and diffuse lung diseases, as related to key technical advances in CT and manifested in Radiology.

"Vanishing liver metastases"-A real challenge for liver surgeons

Expanded surgical intervention in colorectal liver metastasis (LM) and improved chemotherapy led to increasing problem of disappearing liver metastases (DLM). Treatment of those continues to evolve and poses a real challenge for HPB surgeons. This review discusses a clinical approach to DLM, emphasizing crucial steps in clinical algorithm. Particular issues such as imaging, intraoperative detection and surgical techniques are addressed. A step-by-step algorithm is suggested.

Three-dimensional spatiotemporal features for fast content-based retrieval of focal liver lesions

Content-based image retrieval systems for 3-D medical datasets still largely rely on 2-D image-based features extracted from a few representative slices of the image stack. Most 2 -D features that are currently used in the literature not only model a 3-D tumor incompletely but are also highly expensive in terms of computation time, especially for high-resolution datasets. Radiologist-specified semantic labels are sometimes used along with image-based 2-D features to improve the retrieval performance. Since radiological labels show large interuser variability, are often unstructured, and require user interaction, their use as lesion characterizing features is highly subjective, tedious, and slow. In this paper, we propose a 3-D image-based spatiotemporal feature extraction framework for fast content-based retrieval of focal liver lesions. All the features are computer generated and are extracted from four-phase abdominal CT images. Retrieval performance and query processing times for the proposed framework is evaluated on a database of 44 hepatic lesions comprising of five pathological types. Bull's eye percentage score above 85% is achieved for three out of the five lesion pathologies and for 98% of query lesions, at least one same type of lesion is ranked among the top two retrieved results. Experiments show that the proposed system's query processing is more than 20 times faster than other already published systems that use 2-D features. With fast computation time and high retrieval accuracy, the proposed system has the potential to be used as an assistant to radiologists for routine hepatic tumor diagnosis.

Content-based image retrieval of multiphase CT images for focal liver lesion characterization

PURPOSE

Characterization of focal liver lesions with various imaging modalities can be very challenging in the clinical practice and is experience-dependent. The authors' aim is to develop an automatic method to facilitate the characterization of focal liver lesions (FLLs) using multiphase computed tomography (CT) images by radiologists.

METHODS

A multiphase-image retrieval system is proposed to retrieve a preconstructed database of FLLs with confirmed diagnoses, which can assist radiologists' decision-making in FLL characterization. It first localizes the FLL on multiphase CT scans using a hybrid generative-discriminative FLL detection method and a nonrigid B-spline registration method. Then, it extracts the multiphase density and texture features to numerically represent the FLL. Next, it compares the query FLL with the model FLLs in the database in terms of the feature and measures their similarities using the L1-norm based similarity scores. The model FLLs are ranked by similarities and the top results are finally provided to the users for their evidence studies.

RESULTS

The system was tested on a database of 69 four-phase contrast-enhanced CT scans, consisting of six classes of liver lesions, and evaluated in terms of the precision-recall curve and the Bull's Eye Percentage Score (BEP). It obtained a BEP score of 78%. Compared with any single-phase based representation, the multiphase-based representation increased the BEP scores of the system, from 63%-65% to 78%. In a pilot study, two radiologists performed characterization of FLLs without and with the knowledge of the top five retrieved results. The results were evaluated in terms of the diagnostic accuracy, the receiver operating characteristic (ROC) curve and the mean diagnostic confidence. One radiologist's accuracy improved from 75% to 92%, the area under ROC curves (AUC) from 0.85 to 0.95 (p = 0.081), and the mean diagnostic confidence from 4.6 to 7.3 (p = 0.039). The second radiologist's accuracy did not change, at 75%, with AUC increasing from 0.72 to 0.75 (p = 0.709), and the mean confidence from 4.5 to 4.9 (p = 0.607).

CONCLUSIONS

Multiphase CT images can be used in content-based image retrieval for FLL's categorization and result in good performance in comparison with single-phase CT images. The proposed method has the potential to improve the radiologists' diagnostic accuracy and confidence by providing visually similar lesions with confirmed diagnoses for their interpretation of clinical studies.

Surgical management of disappearing colorectal liver metastases

BACKGROUND

Owing to expanded surgical indications for colorectal liver metastasis (CRLM) and improved systemic therapy, hepatic surgeons are increasingly faced with the problem of disappearing (no longer visible on imaging) liver metastasis (DLM).

METHODS

A review of relevant studies was performed. Studies that reported on DLM associated with preoperative chemotherapy for CRLM were identified, and data were synthesized and tabulated. The PubMed database was searched for relevant articles published between January 2000 and December 2012.

RESULTS

A complete response on imaging does not necessarily equate with a complete clinical or pathological response. Rather, residual macroscopic disease is found in about 25-45 per cent of patients at the time of operation. Even among patients with a complete pathological response, long-term remission occurs in only 20-50 per cent of those treated with systemic therapy. A durable response of DLM is more common following the use of hepatic artery infusion therapy.

CONCLUSION

Liver resection should include all original sites of disease if possible.

Evaluating agreement regarding the resectability of colorectal liver metastases: a national case-based survey of hepatic surgeons

BACKGROUND

The resectability of colorectal liver metastases is in part largely based on the surgeon's assessment of cross-sectional imaging. This process, while guided by principles, is subjective. The objective of the present study was to assess agreement between hepatic surgeons regarding the resectability of colorectal liver metastases.

METHODS

Forty-six hepatic surgeons across Canada were invited. A patient with biologically favourable disease was presented after having received neoadjuvant chemotherapy. The scenario was matched with 10 different scrollable abdominal CT scans representing a maximum response after six cycles of chemotherapy. Surgeons were asked to offer an opinion on resectability of liver metastases, and whether they would use adjunct modalities to hepatic resection.

RESULTS

Twenty-six surgeons participated. Twenty responses were complete. The median number of scenarios deemed resectable was 6/10 (range 3-8). Two control scenarios demonstrated perfect agreement. Agreement on resectability was poor for 4/8 test scenarios, of which one scenario demonstrated complete disagreement. Among resectable cases, the pattern of use of adjunct modalities was variable. A median ratio of 0.87 adjunct modality per resectable scenario per surgeon was used (range 0.25-1.75).

CONCLUSION

A significant lack of agreement was identified among surgeons on the resectability and use of adjunct modalities in the treatment of colorectal liver metastases.

Targeted MRI contrast agents for pediatric hepatobiliary disease

New options are available for the magnetic resonance imaging (MRI) assessment of pediatric hepatobiliary disease. This article describes the potential utility for MRI with contrast agents tailored for hepatobiliary imaging. MRI contrast agents that preferentially target the liver may be helpful in characterizing liver masses and bile duct abnormalities in select children. The imaging approach is noninvasive and relatively rapid to perform. It also provides anatomic and functional information and is a radiation-free alternative to other imaging strategies. This relatively new imaging procedure is placed in the context of more established imaging modalities. The pharmacokinetics, technical considerations, and potential applications of these hepatobiliary-specific contrast agents also are discussed.

Value of visual inspection, bimanual palpation, and intraoperative ultrasonography during hepatic resection for liver metastases of colorectal carcinoma

BACKGROUND

Intraoperative detection of new nodules is common in patients undergoing hepatectomy for colorectal liver metastases, although the value of intraoperative diagnosis is not well assessed.

METHODS

A prospectively collected and recorded database was retrospectively analyzed. Helical computed tomography (CT) results were correlated with those of the intraoperative diagnosis in 183 consecutive patients undergoing 254 consecutive hepatectomies, including repeated resection for colorectal liver metastases.

RESULTS

In total, 270 nodules were newly detected during 65 hepatectomies. The sensitivity of CT to detect metastatic nodules was 72.8% (722/992), but it decreased to 34.6% (125/361) for small (≤ 1 cm diameter) tumors. Intraoperative visual inspection and/or palpation detected 207 of 270 nodules. Intraoperative ultrasonography (IOUS) played an important role in identifying deep (≥ 1 cm from the surface) and comparatively small (≤ 1 cm diameter) nodules (4/9 vs. 16/18, respectively, for those >1 cm vs. ≤ 1 cm diameter). The likelihood of intraoperative detection of new nodules increased from 10 in 112 to 6 in 9 when the preoperative tumor number increased from solitary to ≥ 10, resulting in an overall likelihood of 65 in 254 (25.6%). Of 65 patients with new nodules, 21 had at least one nodule that was detected only by IOUS. Preoperatively scheduled hepatectomy was altered in 47 (72%) patients, although additional limited resection(s) were sufficient to remove these nodules in 43 (91%) of them.

CONCLUSIONS

Visual inspection, palpation, and IOUS had equally indispensable roles in detecting new nodules during hepatectomy. Detection was common and usually necessitated alteration, albeit moderately, of the surgical plan.

Correlation between CT arterial enhancement patterns and clinicopathologic findings for intrahepatic mass-forming cholangiocarcinomas

AIM: To evaluate the computed tomography (CT) imaging features of intrahepatic mass-forming cholangiocarcinomas (IMCCs), with a special emphasis on the degree and pattern of arterial enhancement, and to determine whether the clinicopathologic features of IMCCs with arterial enhancement differ from those of IMCCs with less arterial enhancement.

METHODS: Thirty-two patients with 34 pathologically confirmed IMCCs after surgical resection underwent multiphasic CT-unenhanced, hepatic arterial phase (HAP), portal venous phase, and/or equilibrium phase imaging. CT images were retrospectively evaluated for tumor morphology and enhancement features. Patients were placed into typical or atypical enhancement groups according to the presence of enhancement in the largest volume (> 50%) of the tumors during the HAP. Imaging features of IMCCs were correlated with pathologic features. The typical and atypical enhancement groups were compared with respect to disease-free survival and overall survival. Survival rates were calculated by using the Kaplan-Meier method, and differences in survival were compared by using the log-rank test. A Cox proportional hazards model was used for multivariate survival analysis.

RESULTS: Twenty-four (71%) of 34 IMCCs showed typical arterial enhancement, and 10 (29%) showed atypical enhancement. The mean diameter of atypical IMCCs was significantly smaller than that of typical IMCCs (P = 0.001). Chronic liver disease was more frequent in the group with atypical lesions (P = 0.021). During the HAP, the prevalent enhancement pattern in this group was a mixed pattern of peripheral rim and internal heterogeneous enhancement. At pathologic evaluation, atypically enhancing IMCCs showed less central stroma and necrosis and larger cellular areas and more frequently had a cholangiolocellular component than typically enhancing IMCCs. Arterial enhancement of IMCCs was found to be an independent prognostic factor for longer disease-free survival.

CONCLUSION: Arterially enhancing IMCCs are not rare; thus, enhancement pattern analysis of arterially enhancing IMCCs will be helpful in differentiating them from hepatocellular carcinomas. In addition, arterial enhancement of IMCCs appears to correlate with disease-free survival.

[Surgical treatment of liver metastasis in patients with colorectal cancer]

Half of patients with colorectal cancer have liver metastasis during their illness. Surgical resection of metastases represents the only curative treatment with prolonged survival in more than 50 % of patients. The aim of liver resection is complete excision of the lesions with histological negative margins while preserving sufficient functional liver parenchyma. In patients with diffuse liver disease, the radiofrequency ablation of metastases may be associated with surgical resection. The use of portal vein remobilization and neoadjuvant chemotherapy can also increase the number of patients for curative treatment. Despite this progress, from 50 to 60 % of patients relapse after complete resection of MHCCR. Surgical treatment of recurrent aggressive and effective chemotherapy allows the prolonged survival of these patients. The modern treatment of liver metastasis of colorectal cancers can be envisaged as part of a multidisciplinary approach to increase the number of patients for curative treatment.

Is intra-operative ultrasound still useful for the detection of a hepatic tumour in the era of modern pre-operative imaging?

BACKGROUND

The current role of intra-operative ultrasound (IOUS) is questioned because of recent progress in medical imaging. The aim of the present study was to determine the accuracy of IOUS in the detection of a hepatic tumour (HT) compared with a pre-operative multi-detector computed tomography (MDCT) scan and magnetic resonance imaging (MRI).

METHODS

This retrospective study included 418 patients evaluated using an 8-slice MDCT scan (SCAN8), 64-slice MDCT scan (SCAN64) and MRI alone or combined with a computed tomography (CT) scan. The pathological result was used as a gold standard.

RESULTS

Correlation rates for the number of detected lesions compared with pathology results were 0.627 for SCAN8, 0.785 for SCAN64, 0.657 for MRI and 0.913 for IOUS. Compared with pathology, the rate of concordance was significantly higher with IOUS (0.871) than with SCAN8 (0.736; P=0.011), SCAN64 (0.792; P<0.001) and MRI (0.742; P<0.001). IOUS was responsible for a change in operative strategy in 16.5% of patients. Surgery was extended in 12.4%, limited in 1.7% and abandoned in 2.4%.

CONCLUSIONS

Compared with cross-sectional pre-operative imaging, IOUS is still superior for the detection of HT and the planning of surgery. IOUS remains recommended as a routine procedure in patients having a hepatic resection in the era of modern pre-operative imaging.

Intrahepatic mass-forming cholangiocarcinomas: enhancement patterns at multiphasic CT, with special emphasis on arterial enhancement pattern--correlation with clinicopathologic findings

PURPOSE

To evaluate the imaging features of intrahepatic mass-forming cholangiocarcinomas (IMCCs) at computed tomography (CT), with a special emphasis on the degree and pattern of arterial enhancement, and to determine whether the clinicopathologic features of IMCCs with arterial enhancement differ from those of IMCCs with less arterial enhancement.

MATERIALS AND METHODS

The institutional review board of Seoul National University Hospital approved this retrospective study, and informed patient consent was waived. Sixty-four patients with 70 pathologically confirmed IMCCs after surgical resection underwent multiphasic CT-unenhanced, hepatic arterial phase (HAP), portal venous phase, and/or equilibrium phase imaging. CT images were retrospectively evaluated for tumor morphology and enhancement features. Patients were placed into typical or atypical enhancement groups according to the presence of enhancement in the largest volume (>50%) of the tumors during the HAP. Imaging features of IMCCs were correlated with pathologic features. The typical and atypical enhancement groups were compared with respect to disease-free survival and overall survival. Survival rates were calculated by using the Kaplan-Meier method, and differences in survival were compared by using the log-rank test. A Cox proportional hazards model was used for multivariate survival analysis.

RESULTS

Fifty (71%) of 70 IMCCs showed typical arterial enhancement, and 20 (29%) showed atypical enhancement. The mean diameter of atypical IMCCs was significantly smaller than that of typical IMCCs (P = .001). Chronic liver disease was more frequent in the group with atypical lesions (P = .021). During the HAP, the prevalent enhancement pattern in this group was a mixed pattern of peripheral rim and internal heterogeneous enhancement. At pathologic evaluation, atypically enhancing IMCCs showed less central stroma and necrosis and larger cellular areas and more frequently had a cholangiolocellular component than typically enhancing IMCCs. Arterial enhancement of IMCCs was found to be an independent prognostic factor for longer disease-free survival.

CONCLUSION

Arterially enhancing IMCCs were not rare; thus, enhancement pattern analysis of arterially enhancing IMCCs will be helpful in differentiating them from hepatocellular carcinomas. In addition, arterial enhancement of IMCCs appears to correlate with disease-free survival.

Optimizing resection for "responding" hepatic metastases after neoadjuvant chemotherapy

Fifty percent of patients with colorectal cancer will develop metastases at some time during their disease, with the liver being the most common site. Recent advances in the treatment of metastatic colorectal cancer have led to a change in treatment paradigm. What follows is a review of the surgical management of hepatic colorectal metastases responding to neoadjuvant chemotherapy. In addition, the complexity of treating patients with "disappearing" colorectal liver metastases is discussed.

Optimum imaging of colorectal metastases

Dramatic improvements in diagnostic imaging have developed with and enabled increasingly sophisticated treatments for metastatic colorectal cancer. Advances in therapeutic techniques, such as surgical resection and percutaneous therapies, demand that diagnostic imaging provide an accurate assessment of disease burden as well as precise localization. In this article, we present the current state-of-the-art of diagnostic imaging for evaluation of metastatic colorectal cancer.

Utility of preoperative imaging in evaluating colorectal liver metastases declines over time

OBJECTIVES

Reports on the sensitivity and accuracy of contrast-enhanced helical computed tomography (HCT) in the preoperative evaluation of colorectal liver metastases (CLM) have been conflicting. Few studies have controlled for and reported on the time interval between HCT and eventual surgery.

METHODS

A multi-institution, retrospective review of consecutive patients who underwent hepatic resection for CLM from January 1999 to September 2004 was conducted. Data regarding lesion characteristics and resectability were extracted from radiology reports, operative findings and histopathological records. Findings in HCT were evaluated according to their sensitivity for detecting CLM and ability to predict resectability.

RESULTS

A total of 217 consecutive patients who underwent hepatic resection for CLM were identified. The overall sensitivity of HCT for detection of CLM was 83.2%. Prolonged time between imaging and surgery was a negative predictor for HCT sensitivity in univariate and multivariate analysis (P < 0.001). In predicting resectability, preoperative HCT was accurate 77.0% of the time. The time interval to surgery was negatively correlated with HCT prediction accuracy in univariate and multivariate analyses (P < 0.001).

CONCLUSIONS

The utility of HCT as a preoperative tool to evaluate CLM is inversely proportional to the time interval between imaging and surgery. This may explain conflicting reports of the accuracy of HCT in the current literature.

Detection and characterization of focal liver lesions: a Japanese phase III, multicenter comparison between gadoxetic acid disodium-enhanced magnetic resonance imaging and contrast-enhanced computed tomography predominantly in patients with hepatocellular carcinoma and chronic liver disease

OBJECTIVES

To prospectively evaluate the safety and efficacy of combined unenhanced and gadoxetic acid disodium (Gd-EOB-DTPA)-enhanced magnetic resonance (MR) imaging compared with unenhanced MR imaging and triphasic contrast-enhanced spiral computed tomography (CT) for the detection and characterization of focal liver lesions.

MATERIALS AND METHODS

The study was reviewed and approved by the institutional review board at each of the 15 centers involved in the study, and informed written consent was given by all patients. In total, 178 patients with suspected focal hepatic lesions (based, in most patients, on CT, tumor marker and ultrasound examinations) underwent combined MR imaging with a single, rapid injection of Gd-EOB-DTPA 0.025 mmol/kg, including T1-weighted dynamic and delayed MR images 20 to 40 minutes postinjection. Triphasic contrast-enhanced CT, the comparator examination, was performed within 4 weeks of MR imaging. Standard of references (SOR) were resection histopathology and intraoperative ultrasonography, or combined CT during arterial portography and CT hepatic arteriography; in cases where, although the major lesions were treated, some lesion(s) were not treated, follow-up superparamagnetic iron oxide-enhanced MR imaging was additionally performed. All images were assessed for differences in lesion detection and characterization (specific lesion type) by on-site readers and 3, blinded (off-site) reviewers. All adverse events (AEs) occurring within 72 hours after Gd-EOB-DTPA administration were reported.

RESULTS

Overall, 9.6% of patients who received Gd-EOB-DTPA reported 21 drug-related AEs. A total of 151 patients were included in the efficacy analysis. Combined MR imaging showed statistically higher sensitivity in lesion detection (67.5%-79.5%) than unenhanced MR imaging (46.5%-59.1%; P < 0.05 for all). Combined MR imaging also showed higher sensitivity in lesion detection than CT (61.1%-73.0%), with the results being statistically significant (P < 0.05) for on-site readers and 2 of 3 blinded readers. Higher sensitivity in lesion detection with combined MR imaging compared with CT was also clearly demonstrated in the following subgroups: lesions with a diameter <or=20 mm (lesions <or=10 mm: 38.0%-55.4% vs. 26.1%-47.3%, respectively; lesions 10-20 mm: 71.1%-87.3% vs. 65.7%-78.4%, respectively); in cirrhotic patients (64.5%-75.4% vs. 54.5%-70.3%, respectively); and in patients with hepatocellular carcinoma (66.6%-78.6% vs. 59.1%-71.6%, respectively). Combined MR imaging demonstrated a higher proportion of correctly characterized lesions (50.5%-72.1%) than unenhanced MR imaging (30.2%-50.0%; P < 0.05 for all), whereas there were no significant differences compared with CT (49.0%-68.1%), except for one blinded reader (P < 0.05).

CONCLUSION

In this study, hepatocyte-specific Gd-EOB-DTPA was shown to be safe and to improve the detection and characterization of focal hepatic lesions compared with unenhanced MR imaging. When compared with spiral CT, Gd-EOB-DTPA enhanced MRI seems to be beneficial especially for the detection for smaller lesions or hepatocellular carcinoma underlying cirrhotic liver.

Is there a role for endoscopic ultrasonography in evaluation of the left liver in colorectal liver metastasis patients selected for right hepatectomy

BACKGROUND

Meticulous assessment of the left liver for patients scheduled for right hepatectomy is essential. Endoscopic ultrasonography (EUS) is frequently used for the locoregional staging or biopsy of pancreatic tumours and has shown some value in the evaluation of the left liver.

METHODS

We prospectively enrolled 24 consecutive patients who were scheduled for at least a right hepatectomy and who underwent laparotomy for colorectal liver metastasis (CLMs). The left liver was assessed preoperatively with standard techniques [computed tomography (CT) scan, percutaneous ultrasonography] and EUS. These results were compared with those of intraoperative ultrasonography (IOUS).

RESULTS

The study population consisted of 12 men and 12 women (mean age 64 years, range 47-79 years). Mean body mass index was 26 kg/m(2) (range 20-35 kg/m(2)). Standard preoperative evaluation detected 28 lesions in the left liver; EUS detected just 17 lesions, whereas IOUS detected 30 lesions in the left liver. For the left lobe of the liver (segments II and III), the standard evaluation had sensitivity of 85%, specificity of 64%, positive predictive value (PPV) of 50% and negative predictive value (NPV) of 91%; EUS had sensitivity of 55%, specificity of 86%, PPV of 71% and NPV of 76%; IOUS had sensitivity of 85.2%, specificity of 92%, PPV of 96.6% and NPV of 75%. In terms of the left liver (i.e. segments II, III and IV), the results of EUS were less good than for the left lobe of the liver.

CONCLUSION

For segments II and III, EUS had higher specificity and positive predictive value than standard evaluation, but only changed our therapeutic strategy in three cases. Even though EUS can provide some valuable information, the technique is not accurate enough to merit systematic performance as part of a standard preoperative evaluation. This study underlines the main role of IOUS in the left liver, with better sensitivity, specificity, and positive predictive value than EUS and standard evaluation.

Current management of colorectal hepatic metastasis

In the USA, cancers of the colon and rectum are the third most common site of new cancer cases and cancer deaths. With improved screening and adjuvant therapy, the survival of patients has increased substantially over the last decade. However, patients with metastatic disease often have limited survival. Hepatic metastasis is one of the most frequent sites of metastatic disease. In fact, 35-55% of patients with colorectal cancer will develop hepatic metastasis at some time during the course of their disease. Patients who are able to undergo complete resection of their hepatic metastases have the best chance of long-term survival. The goal of hepatic resection is to achieve complete resection of all metastases with microscopically negative surgical margins while preserving sufficient hepatic parenchyma. Survival following hepatic resection of colorectal metastasis now approaches 35-50%. However, approximately 65% of patients will have a recurrence at 5 years. Increasingly chemotherapeutic agents are being offered in the preoperative setting prior to operation. At the time of operation, patients with extensive hepatic disease can sometimes be offered ablative therapies combined with resection or staged approaches. Modern management of hepatic colorectal metastases necessitates a multidisciplinary approach to effectively treat these patients and increase the number of patients who will benefit from resection.

Management of hepatic metastasis from colorectal cancers: an update

Approximately 50%-60% of patients with colorectal cancers will develop liver lesions in their life span. Despite the potential of surgical resection to provide long-term survival in this subset of patients, only 15%-20% are found to be resectable. The introduction of new neoadjuvant chemotherapeutic agents and the expanding criteria of resection have enhanced the overall 5-year survival from 30% to 60% in the past decade. The use of technical innovations such as staged resection; portal vein embolization, and repeat resection have allowed higher resection rates in patients with bilobar disease. Extrahepatic primary and liver-exclusive recurrent disease no longer represent an absolute contraindication to resection. The role of regional therapy using hepatic arterial infusion is being redefined for liver-exclusive unresectable disease. Adjuvant chemotherapy in combination with regional therapies is being looked at from fresh perspectives. Ablative approaches have gained a firm role both as an adjunct to surgical resection and in the management of patients who are not surgical candidates. Overall, the management of hepatic metastasis from colorectal cancers requires a multimodal approach.

Dual energy CT: preliminary observations and potential clinical applications in the abdomen

Dual energy CT (DECT) is a new technique that allows differentiation of materials and tissues based on CT density values derived from two synchronous CT acquisitions at different tube potentials. With the introduction of a new dual source CT system, this technique can now be used routinely in abdominal imaging. Potential clinical applications include evaluation of renal masses, liver lesions, urinary calculi, small bowel, pancreas, and adrenal glands. In CT angiography of abdominal aortic aneurysms, dual energy CT techniques can be used to remove bones from the datasets, and virtual unenhanced images allow differentiation of contrast agent from calcifying thrombus in patients with endovascular stents. This review describes potential applications, practical guidelines, and limitations of dual energy CT in the abdomen.

Perioperative outcome of laparoscopic left lateral liver resection is improved by using a bioabsorbable staple line reinforcement material in a porcine model

HYPOTHESIS

Laparoscopic liver surgery is significantly limited by the technical difficulty encountered during transection of substantial liver parenchyma, with intraoperative bleeding and bile leaks. This study tested whether the use of a bioabsorble staple line reinforcement material would improve outcome during stapled laparoscopic left lateral liver resection in a porcine model.

STUDY DESIGN

A total of 20 female pigs underwent stapled laparoscopic left lateral liver resection. In group A (n = 10), the stapling devices were buttressed with a bioabsorbable staple line reinforcement material. In group B (n = 10), standard laparoscopic staplers were used. Operative data and perioperative complications were recorded. Necropsy studies and histopathological analysis were performed at 6 weeks. Data were compared between groups with the Student's t-test or the chi-square test.

RESULTS

Operating time was similar in the two groups (64 +/- 11 min in group A versus 68 +/- 9 min in group B, p = ns). Intraoperative blood loss was significantly higher in group B (185 +/- 9 mL versus 25 +/- 5 mL, p < 0.05). There was no mortality. There was no morbidity in the 6-week follow-up period; however, two animals in group B had subphrenic bilomas (20%) at necropsy. At necropsy, methylene blue injection via the main bile duct revealed leakage from the biliary tree in four animals in group B and none in group A (p < 0.05). Histopathological examination of the resection site revealed minor abnormalities in group A while animals in group B demonstrated marked fibrotic changes and damaged vascular and biliary endothelium.

CONCLUSION

Use of a bioabsorbable staple line reinforcement material reduces intraoperative bleeding and perioperative bile leaks during stapled laparoscopic left lateral liver resection in a porcine model.

Peripheral mass-forming cholangiocarcinoma in cirrhotic liver

OBJECTIVE

The purpose of this study was to determine whether particular enhancement patterns of intrahepatic cholangiocarcinoma in cirrhotic liver suggest the correct diagnosis.

MATERIALS AND METHODS

The CT findings on 28 lesions in 26 patients with underlying liver cirrhosis and pathologically proven cholangiocarcinoma were retrospectively evaluated. The CT findings of hepatocellular carcinoma (HCC) in a control group of 79 subjects also were analyzed. The relative attenuation and enhancement pattern of the lesions were evaluated by two observers in consensus. The difference between the enhancement pattern of cholangiocarcinoma and that of HCC was statistically analyzed with the Fisher's exact test.

RESULTS

The prevalent enhancement patterns of cholangiocarcinoma on enhanced CT scans differed depending on tumor size. Peripheral rimlike enhancement was the most frequent (nine of 20 cases) pattern in tumors larger than 3 cm in diameter. A washout pattern on portal venous phase scans was the most frequent (five of eight cases) in tumors smaller than 3 cm in diameter. For tumors smaller than 3 cm in diameter, there was no significant difference between the enhancement pattern of cholangiocarcinoma and that of HCC. For tumors larger than 3 cm, the presence of peripheral rimlike enhancement or centripetal enhancement and the absence of a washout pattern were significant findings for differentiating cholangiocarcinoma from HCC (p < 0.0001).

CONCLUSION

The contrast enhancement patterns of cholangiocarcinoma in cirrhotic liver on multiphasic helical CT scans were found to differ depending on tumor size. Because of the overlapping imaging findings in the two diseases, for any hypovascular lesion smaller than 3 cm in a cirrhotic liver, the diagnosis of cholangiocarcinoma should be seriously considered along with that of HCC.

Diagnostic efficacy of gadoxetic acid (Primovist)-enhanced MRI and spiral CT for a therapeutic strategy: comparison with intraoperative and histopathologic findings in focal liver lesions

A multicenter study has been employed to evaluate the diagnostic efficacy of magnetic resonance imaging (MRI) using the new liver-specific contrast agent gadoxetic acid (Gd-EOB-DTPA, Primovist), as opposed to contrast-enhanced biphasic spiral computed tomography (CT), in the diagnosis of focal liver lesions, compared with a standard of reference (SOR). One hundred and sixty-nine patients with hepatic lesions eligible for surgery underwent Gd-EOB-DTPA-enhanced MRI as well as CT within 6 weeks. Pathologic evaluation of the liver specimen combined with intraoperative ultrasound established the SOR. Data sets were evaluated on-site (14 investigators) and off-site (three independent blinded readers). Gd-EOB-DTPA was well tolerated. Three hundred and two lesions were detected in 131 patients valid for analysis by SOR. The frequency of correctly detected lesions was significantly higher on Gd-EOB-DTPA-enhanced MRI compared with CT in the clinical evaluation [10.44%; 95% confidence interval (CI): 4.88, 16.0]. In the blinded reading there was a trend towards Gd-EOB-DTPA-enhanced MRI, not reaching statistical significance (2.14%; 95% CI: -4.32, 8.6). However, the highest rate of correctly detected lesions with a diameter below 1 cm was achieved by Gd-EOB-DTPA-enhanced MRI. Differential diagnosis was superior for Gd-EOB-DTPA-enhanced MRI (82.1%) versus CT (71.0%). A change in surgical therapy was documented in 19 of 131 patients (14.5%) post Gd-EOB-DTPA-enhanced MRI. Gd-EOB-DTPA-enhanced MRI was superior in the diagnosis and therapeutic management of focal liver lesions compared with CT.

Surgical therapy for colorectal metastases to the liver

Colorectal cancer is the fourth most common type of cancer in the West and the second leading cause of cancer-related deaths in the United States. Approximately 35 to 55% of patients with colorectal cancer develop hepatic metastases during the course of their disease. Surgical resection of colorectal liver metastases represents the only chance at potential cure, and long-term survival can be achieved in 35 to 58% of patients after resection. The goal of hepatic resection should be to resect all metastases with negative histologic margins while preserving sufficient functional hepatic parenchyma. In patients with extensive metastatic disease who would otherwise be unresectable, ablative approaches can be used instead of or combined with hepatic resection. The use of portal vein embolization and preoperative chemotherapy may also expand the population of patients who are candidates for surgical treatment. Despite these advances, many patients still experience a recurrence after hepatic resection. More active systemic chemotherapy agents are now available and are being increasingly employed as adjuvant therapy either before or after surgery. Modern treatment of colorectal liver metastasis requires a multidisciplinary approach in an effort to increase the number of patients who may benefit from surgical treatment of colorectal cancer liver metastasis.

Intraoperative ultrasonography during planned liver resections: why are we still performing it?

BACKGROUND

Intraoperative ultrasonography (US) is used in many centers before oncologic liver resections to detect additional tumors and to evaluate the relationship of tumors to major vascular structures. As preoperative imaging improves, it is expected that the diagnostic yield from intraoperative US will diminish. In this study we attempt to determine if fewer unrecognized tumors were being detected and whether intraoperative US is having less impact on surgical decision making.

METHODS

We compared 50 consecutive cases (mean age = 57.2 +/- 10 years; 27 men) who underwent laparotomy for a planned resection of primary liver malignancies or metastases between September 2003 and July 2005 with 50 consecutive cases (mean age = 56.9 +/- 14 years; 25 men) between January 1999 and September 2003. Dedicated intraoperative liver US was performed or supervised by a gastrointestinal radiologist using a 5.0-MHz linear- or curvilinear-array transducer during each procedure.

RESULTS

The rate of detecting unrecognized tumors has not changed significantly (14% vs. 20%, p = 0.70). The use of US to establish the relationship between tumor and the vasculature has not changed (48% vs. 60%, p = 0.23). The percentage of cases where the US findings were responsible for altering surgical management was 20% for both groups. The resection rate was 72% for both groups. The negative resection margin rate has also not changed significantly (86% vs. 69%, p = 0.09).

CONCLUSIONS

Despite the advances in cross-sectional imaging, the frequency of unrecognized tumors found during intraoperative liver US and its use for surgical guidance has not changed significantly. Currently routine intraoperative US alters the management of approximately one fifth of our patients undergoing attempted liver resection for primary malignancies or metastases.

Characterization of focal liver lesions: comparative study of contrast-enhanced ultrasound versus spiral computed tomography

The purpose of this study was to compare the diagnostic accuracy of contrast-enhanced ultrasound (CEUS) with spiral computed tomography (SCT) for the characterization of focal liver lesions (FLL) and to determine the degree of correlation between the two techniques. Seventy-seven FLL (45 hepatocellular carcinomas; 12 metastases; ten hemangiomas; two regenerating/dysplastic nodules; eight focal nodular hyperplasias) detected with ultrasound (US) were prospectively evaluated by CEUS using a second-generation contrast agent and SCT (with an interval of no more than one month between the two techniques). Independent observers made the most probable diagnosis and the results were compared with the final diagnoses (histology n = 59; MRI n = 18). Statistical analysis was performed by the Chi-square and Kappa tests. CEUS provided a correct, specific diagnosis in 69/77 (90%) of the FLL, while SCT did so in 67/77 (87%). The sensitivity, specificity, and diagnostic accuracy for malignancy were 91%, 90%, and 91%, respectively, for CEUS and 88%, 89%, and 88%, respectively, for SCT. No statistically significant difference was found between CEUS and SCT in the characterization of FLL (p > 0.05). In addition, agreement between the two imaging techniques was good (k = 0.75). We conclude that CEUS and SCT provide a similar diagnostic accuracy in the characterization of FLL, with a good degree of correlation between the two techniques.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Positron Emission Tomography/Computed Tomography: Protocol Issues and Options

Combined positron emission tomography/computed tomography (PET/CT) became FDA-approved for clinical use in late 2001. There are several design advantages of combined PET/CT over PET and CT acquired on separate devices, including more accurate CT and PET data co-registration, improved lesion localization, consolidation of imaging studies, and reduced scan times compared to dedicated PET. There are several protocols that can used to scan patients on combined PET/CT devices. Although there is no single "correct" protocol for performing a PET/CT scan, the use of oral and intravenous contrast media may improve the diagnostic value of the CT component. Whether to utilize contrast media depends on important clinical variables, including the specific type of tumor and the likelihood of encountering viable abdominal and pelvic malignancy. This article discusses various protocols pertinent to PET/CT imaging, including how the CT portion of a PET/CT scan can be performed and optimized, as well as PET/CT interpretation and reporting issues.

Multidetector Row CT of the Liver

CT has always played a major role in the imaging of the liver despite continuous challenge by ultrasound and MR imaging. Introduction of multidetector row CT technology has helped CT to excel in its already established indications and has expanded its capabilities by adding new clinical indications, such as CT angiography or liver perfusion. This article discusses the advantages of multidetector row CT scanners in liver imaging, examines the guidelines to improve image quality by optimizing scanning protocols and contrast administration strategies, and reviews the current and potential clinical applications.

Colorectal liver metastases: CT, MR imaging, and PET for diagnosis--meta-analysis

PURPOSE

To perform a meta-analysis to obtain sensitivity estimates of computed tomography (CT), magnetic resonance (MR) imaging, and fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET) for detection of colorectal liver metastases on per-patient and per-lesion bases.

MATERIALS AND METHODS

MEDLINE, EMBASE, Web of Science, and CANCERLIT databases and Cochrane Database of Systematic Reviews were searched for relevant original articles published from January 1990 to December 2003. Criteria for inclusion of articles were as follows: Articles were reported in the English, German, or French language; CT, MR imaging, or FDG PET was performed to identify and characterize colorectal liver metastases; histopathologic analysis (surgery, biopsy, or autopsy), intraoperative observation (manual palpatation, intraoperative ultrasonography [US]), and/or follow-up US was the reference standard; and data were sufficient for calculation of true-positive or false-negative values. A random-effects linear regression model was used to obtain sensitivity estimates in assessment of liver metastases.

RESULTS

Of 165 identified relevant articles, 61 fulfilled all inclusion criteria. Sensitivity estimates on a per-patient basis for nonhelical CT, helical CT, 1.5-T MR imaging, and FDG PET were 60.2%, 64.7%, 75.8%, and 94.6%, respectively; FDG PET was the most accurate modality. On a per-lesion basis, sensitivity estimates for nonhelical CT, helical CT, 1.0-T MR imaging, 1.5-T MR imaging, and FDG PET were 52.3%, 63.8%, 66.1%, 64.4%, and 75.9%, respectively; nonhelical CT had lowest sensitivity. Estimates of gadolinium-enhanced MR imaging and superparamagnetic iron oxide (SPIO)-enhanced MR imaging were significantly better, compared with nonenhanced MR imaging (P = .019 and P < .001, respectively) and with helical CT with 45 g of iodine or less (P = .02 and P < .001, respectively). For lesions of 1 cm or larger, SPIO-enhanced MR imaging was the most accurate modality (P < .001).

CONCLUSION

FDG PET had significantly higher sensitivity on a per-patient basis, compared with that of the other modalities, but not on a per-lesion basis. Sensitivity estimates for MR imaging with contrast agent were significantly superior to those for helical CT with 45 g of iodine or less.