***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: 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 prospect ively 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 BACKGROUND / AIMS We prospect ively evaluated whether fluorine-18 deoxyglucose ( FDG ) positron coincidence detection ( PCD ) or FDG single-photon emission computed tomography ( SPECT ) provides additional benefits to our conventional preoperative evaluation of lesion detection in patients suspected to have hepatocellular carcinoma ( HCC ) . METHODS Thirteen consecutive patients with a suspected HCC underwent conventional preoperative evaluation with ultrasonography ( US ) , triple-phase helical computed tomography ( CT ) , superparamagnetic iron oxides ( SPIO ) enhanced magnetic resonance imaging ( MRI ) and serum alpha-fetoprotein ( AFP ) level . All 13 patients had an FDG-PCD and SPECT . These results were evaluated to assess the value of FDG-PCD and SPECT in addition to US , SPIO-enhanced MRI and triple-phase helical CT . RESULTS Ten of the 13 ( 77 % ) patients had at least one histologically confirmed HCC without extrahepatic abdominal spread . The tumors ranged in size from 1 to 8 cm and the serum AFP ranged from 3 to 30 000 microg/l . Of these 10 patients , two patients had an increased tumor F-FDG uptake ( sensitivity of 20 % ) ; one patient with an AFP of 5 microg/l and a tumor size of maximum 4.5 cm and one patient with an AFP of 249 microg/l and a tumor size of maximum 2 cm . In three patients with a benign liver mass , FDG imaging with either PCD or SPECT was negative . There was no false positive finding . CONCLUSIONS We found poor sensitivity of  FDG-PCD and FDG-SPECT for the detection of HCC . There were no clear relations between AFP or tumor size and FDG uptake . Therefore , we conclude that FDG imaging with PCD or SPECT has no value in the preoperative work-up for HCC in patients with cirrhosis The aim of this study was to assess the added diagnostic value of contrast-enhanced US ( CEUS ) combined with 64-row multidetector CT ( CT ) in the assessment of hepatocellular nodule vascularity in patients with liver cirrhosis . One hundred and six cirrhotic patients ( 68 male , 38 female ; mean age ± SD , 70 ± 7 years ) with 121 biopsy-proven hepatocellular nodules ( 72 hepatocellular carcinomas , 10 dysplastic and 15 regenerative nodules , 12 hemangiomas , and 12 other benignancies ) detected during US surveillance were prospect ively recruited . Each nodule was scanned by CEUS during the arterial ( 10–40 s ) , portal venous ( 45–90 s ) , and delayed sinusoidal phase ( from 100 s after microbubble injection to microbubble disappearance ) . Nodule vascularity  at CEUS , CT , and combined CEUS/CT was evaluated side-by-side by two independent blinded readers who classified nodules as benign or malignant according to reference diagnostic criteria . The combined assessment of CEUS/CT  provided higher sensitivity ( 97 % , both readers ) than did separate assessment of CEUS ( 88 % reader 1 ; 87 % reader 2 ) and CT ( 74 % reader 1 ; 71 % reader 2 ; P < 0.05 ) , while no change in specificity was provided by combined analysis . The combined assessment of hepatocellular nodule vascularity at CT and CEUS improved sensitivity in the diagnosis of malignancy in patients with liver cirrhosis Objective To determine the real value of liver imaging in cirrhosis by macro- and histomorphologic examination of the entire organ after orthotopic liver transplantation for hepatocellular carcinoma ( HCC ) . Summary Background Data In comparative studies , a virtual sensitivity of up to 94 % is described for helical computed tomography in HCC staging . The tumor detection rate of intraoperative ultrasonography ( IOUS ) is reported to be almost 100 % . Methods This prospect i ve observational study comprised 23 patients with HCC in cirrhosis admitted for orthotopic liver transplantation . Results of preoperative triphasic helical computed tomography ( HCT ) and IOUS were correlated with histopathologic results after 3-mm-slicing of the explanted liver . Results Overall , 179 liver segments were examined by HCT , IOUS , and MHM . Fifty-two malignant lesions and 10 dysplastic nodules were revealed by MHM . Using HCT , 13 HCCs could not be identified in 8 patients and 15 results were falsely positive in 10 patients . The detection rate of dysplastic nodes was 40 % for HCT and 60 % for IOUS . IOUS  missed four HCCs in four patients and had six false-positive results in six patients . In a segment-based analysis , the overall accuracy of IOUS  was significantly higher for IOUS ( 95.5 % ) versus HCT ( 89.9 % ) . In the lesion-by-lesion analysis , the sensitivity was 92.3 % for IOUS and 75.0 % for HCT , with a significant difference . Conclusions Correlation of explanted liver pathologic results offers precise evaluation of imaging modalities . The data of this histopathologically based study confirm that IOUS is significantly superior in staging HCC in cirrhosis versus CT , even after technical refinements through enhanced multiphasic high-velocity helical scanning PURPOSE To determine the prevalence of clinical ly unsuspected hepatocellular carcinoma ( HCC ) with advanced cirrhosis and assess the sensitivity of helical computed tomographic ( CT ) surveillance for tumor detection in these patients . MATERIAL S AND METHODS Prospect i ve direct correlation of CT findings with explanted liver specimen findings was performed in 430 transplant recipients with cirrhosis . The prevalence of clinical ly unsuspected HCC according to liver disease cause was evaluated . Serum alpha-fetoprotein ( AFP ) values in patients with and those without tumor were recorded . Prospect i ve and retrospective CT tumor detection was evaluated with respect to CT technique and time from CT to transplantation . RESULTS HCC was found in 59 ( 14 % ) of 430 transplant recipients without suspicion of tumor before referral for transplantation .  HCC was most prevalent with hepatitis B ( 27 % ) and hepatitis C ( 22 % ) . Serum AFP values were not sensitive for detection of most small tumors . With triphasic helical CT , the prospect i ve and retrospective rates of identifying patients with tumor were 59 % and 68 % , respectively ; the prospect i ve and retrospective tumor nodule detection rates were 37 % and 44 % , respectively . Tumor detection rates were highest with CT performed within 67 days before transplantation . CONCLUSION Clinical ly unsuspected HCC is most prevalent with cirrhosis secondary to hepatitis B or C , and , when evaluated at CT , is best detected with triphasic contrast material -enhanced helical imaging performed within 67 days before transplantation OBJECTIVE The purpose of this study was to evaluate the diagnostic efficacy of three-phase helical dynamic CT in the detection and characterization of  hepatocellular carcinomas and dysplastic nodules in cirrhotic livers . SUBJECTS AND METHODS Three-phase helical dynamic CT in 41 patients with liver cirrhosis was evaluated prospect ively before  orthotopic liver transplantation .  The numbers of hepatocellular carcinomas and dysplastic nodules were assessed in the explanted livers and compared with pretransplantation CT findings . RESULTS Examination of the explanted livers revealed 21 hepatocellular carcinomas in 15 patients and 23 dysplastic nodules in 10 patients . The size of the hepatocellular carcinomas was 0.6 - 5 . 0 cm ( mean , 1.9 cm ) , and that of the dysplastic nodules was 0.7 - 2.0 cm ( mean , 1.0 cm ) . The use of helical dynamic CT enabled detection of 15 of 21 hepatocellular carcinomas ( sensitivity , 71 % ) and nine of 23 dysplastic nodules ( sensitivity , 39 % ) . Patient sensitivity and specificity in the detection of hepatocellular carcinomas were 80 % ( 12/15 ) and 96 % ( 25/26 ) , respectively , and for dysplastic nodules , 50 % ( 5/10 ) and 97 % ( 30/31 ) , respectively . CONCLUSION Three-phase helical dynamic CT is relatively insensitive for detection of hepatocellular carcinomas and dysplastic nodules in cirrhotic livers , especially for dysplastic nodules and hepatocellular carcinomas smaller than 2 cm OBJECTIVE The purpose of this study was to evaluate prospect ively acquired institutional results to determine the accuracy of gadolinium-enhanced MRI in liver tumor surveillance before transplantation . SUBJECTS AND METHODS One hundred fifteen patients underwent MRI of the abdomen within 90 days before liver transplantation . Images were acquired with gadolinium-enhanced 3D gradient-echo sequences in the arterial , venous , and delayed phases . Detection of hepatocellular carcinoma ( HCC ) was based on the imaging criteria arterial phase enhancement , delayed phase hypointensity , and development of an enhancing outer margin capsule . Imaging findings were compared with findings at histopathologic evaluation of the explanted liver . RESULTS Thirty-six HCCs in 27 patients were detected at histopathologic evaluation . Patient-based analysis showed the sensitivity of MRI was 88.9 % ( 24/27 ) ; specificity , 97.7 % ( false-positive findings in two patients ) ; and accuracy , 95.7 % . MRI depicted 28 of 36 HCCs , result ing in a lesion-based sensitivity of 77.8 % . Although all 18 HCCs 2 cm or larger were depicted with MRI , only 10 of 18 HCCs smaller than 2 cm were correctly diagnosed . However , two HCCs measuring smaller than 2 cm at pathologic examination were rated as dysplastic nodules on MRI . CONCLUSION Contrast-enhanced MRI can be used as a primary diagnostic method for accurate detection and characterization of HCC 2 cm or larger as required by the criteria of the Model for End-Stage Liver Disease used by the United Network for Organ Sharing . MRI can be considered a st and ard tool for surveillance before liver transplantation . Reduction in cost and risk may be derived from the diminished need for other diagnostic imaging studies and biopsy and the avoidance of use of iodinated contrast agents in imaging of patients with cirrhosis , many of whom have impaired renal function Hepatocellular carcinogenesis in cirrhosis is a multistage process that includes large regenerative nodules , dysplastic nodules , and hepatocarcinoma . The aim of this study was to establish whether contrast-enhanced Doppler ultrasonography ( US ) is able to distinguish between early hepatocellular carcinoma ( HCC ) and small nonmalignant nodules in cirrhosis . Between January 1998 and December 1999 , 500 cirrhotic patients with no previous history of HCC or evidence of hepatic focal lesions were enrolled and prospect ively followed-up with US every 6 months until December 2000 . Sixty-one patients developed focal lesions , 12 multifocal , and 49 monofocal . Biopsy of focal lesions , contrast-enhanced Doppler US , and spiral computed tomography ( CT ) were performed in 41 consecutive patients with small ( <3 cm ) monofocal lesions . Twenty nodules were diagnosed as HCC and 21 as nonmalignant ( 14 large regenerative nodules , 3 low- grade , and 4 high- 
    Output:
    
The present systematic review did not show an obvious superiority of one imaging method .