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Gastrointestinal Imaging |
1 MRI Unit, Lincoln Wing, St James's University Hospital, Beckett St, Leeds LS9 7TF, England.
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Abstract |
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 TOP Abstract IntroductionMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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MATERIALS AND METHODS: Fifty-one hepatic resection candidates with known colorectal metastases were examined. MR imaging comprised fast spin-echo (SE) T2-weighted imaging, T1-weighted gradient-echo (GRE) fast low-angle shot imaging before SPIO enhancement, dual-echo SE imaging, T2-weighted fast low-angle shot imaging, and T1-weighted GRE imaging after SPIO enhancement. CT was performed with 8-mm collimation and 1:1 pitch; imaging commenced 20 seconds and 65–70 seconds after injection of 150 mL of contrast medium. All images were reviewed independently by four blinded observers. The alternative–free response receiver operating characteristic (ROC) method was used to analyze the results, which were correlated with findings from surgery, intraoperative ultrasonography, and histopathologic studies in 31 patients and with consensus review together with all other imaging and clinical follow-up in 20 patients. Sensitivities were also calculated.
RESULTS: The mean sensitivity of MR was significantly higher than that of CT (P < .02): 79.8% for MR and 75.3% for CT for all lesions, and 80.6% for MR and 73.5% for CT for malignant lesions. The mean areas under the alternative–free response ROC curves were 0.83 for MR and 0.78 for CT (difference not significant).
CONCLUSION: SPIO-enhanced MR imaging was more sensitive than dual-phase CT in the depiction of colorectal metastases.
Index terms: Colon, neoplasms, 75.32 • Iron, 761.12143 • Liver neoplasms, CT, 761.12114, 761.12115 • Liver neoplasms, metastases, 761.3327 • Liver neoplasms, MR, 761.121411, 761.121412, 761.12143 • Magnetic resonance (MR), comparative studies • Receiver operating characteristic curve (ROC)
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Introduction |
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TOPAbstractIntroductionMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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While computed tomography (CT) is used to exclude pulmonary deposits and extra-hepatic abdominal disease, conventional dynamic CT is limited in the depiction of liver lesions because of the time taken to scan the entire liver. With the introduction of helical CT, the depiction of liver lesions is thought to be improved because misregistration artifacts are eliminated, and the use of a dual-phase technique with imaging at both the arterial and portal venous phases of enhancement improves the depiction of hypervascular lesions (1–4). Currently, the most sensitive preoperative imaging modality for the depiction of focal liver lesions is CT during arterial portography (CTAP) (5–7); however, it is an invasive procedure with an established risk of false-positive results.
Superparamagnetic iron oxide (SPIO) has recently been developed as a liver-specific particulate magnetic resonance (MR) imaging contrast agent that is taken up by the Kupffer cells of the liver. Early results have suggested that SPIO-enhanced MR imaging is more accurate than unenhanced MR imaging and contrast-enhanced CT in the depiction of focal liver lesions (8). However, to our knowledge, there are no published studies comparing SPIO-enhanced MR imaging with dual-phase helical CT. The purpose of this study was to compare the accuracy of SPIO-enhanced MR imaging with that of dual-phase helical CT in the preoperative depiction of hepatic metastases by using alternative–free response receiver operating characteristic (ROC) analysis with multiple observers.
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MATERIALS AND METHODS |
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TOPAbstractIntroductionMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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Local ethical committee approval was granted. Informed consent was obtained from each patient before entry into the study.
MR Imaging
All MR imaging was performed on a Magnetom 42SP (Siemens, Erlangen, Germany) 1.0-T system with use of the body coil for transmission and reception of the signal. Before the intravenous injection of SPIO, fast spin-echo (SE; 4,000/91 [repetition time msec/echo time msec]) images with an echo train length of eight, two signals acquired, and a matrix size of 192 x 256, and T1-weighted gradient echo (GRE) in-phase (156/6; flip angle, 80°) and opposed-phase (135/4; flip angle, 80°) images with one signal acquired and a matrix size of 128 x 256 were obtained. After SPIO enhancement, a dual-echo (2,000–2,500/45, 2,000–2,500/90) sequence with two signals acquired and a matrix size of 192 x 256 and a T2-weighted GRE fast low-angle shot (150/10; flip angle, 15°) sequence with one signal acquired and a matrix size of 128 x 256 were performed. Opposed-phase T1-weighted images were also obtained in 33 patients after SPIO injection. For all sequences, an 8–10-mm section thickness was used with a 10%–30% gap and a field of view 35–40 cm, depending on the size of the liver. A rectangular field of view was used in all patients.
In 33 patients, AMI-25 (Endorem; Guerbet, Aulnay-sous-Bois, France) was administered at a dose of 15 µmol of iron per kilogram of body weight, diluted in 100 mL of 5% glucose and infused over 30 minutes; imaging commenced 30–60 minutes from the end of intravenous infusion. In 18 patients, SH U 555A (Resovist; Schering, Berlin, Germany) was injected as a rapid bolus immediately followed by a saline solution flush at a dose of 7.0–12.9 µmol of iron per kilogram of body weight, and imaging commenced 10 minutes from the end of injection. The injection procedure was performed in approximately 5 seconds.
CT Examination
CT was performed on a Somatom Plus S (Siemens) helical scanner. Scanning parameters were 120 kVp, 210 mA, 8–10-mm section collimation, and 8–10 mm/sec table incrementation. Images were reconstructed every 8 mm to provide contiguous or overlapping sections, and the helical acquisition time was 20–24 seconds, depending on liver size. Arterial-phase and portal venous–phase images were obtained starting 20 and 65–70 seconds, respectively, after the start of the injection of 150 mL of nonionic contrast medium (iopromide [Ultravist 300; Schering] or iohexol [Omnipaque 300; Nycomed Imaging, Princeton, NJ]) injected at a rate of 5 mL/sec with a power injector.
CT and MR examinations were performed within 1 day in 34 patients, 1 week in 12 patients, and 1 month in five patients. Surgery was performed 1–10 weeks (mean, 4 weeks) after imaging.
Image Analysis
The images of 51 patients were analyzed. Images from the combined MR sequences (before and after SPIO enhancement) and the combined CT images (arterial and portal venous phases) were viewed independently by four blinded observers (J.W., K.S.N., J.A.G., P.J.R.). The MR and CT images were viewed at separate sessions. Each observer recorded the presence and location of one or more lesions, assigning each one a confidence rating on a four-point scale: "1" was defined as probably not a lesion; "2," as a possible lesion; "3," as a probable lesion; "4," as a definite lesion. At the time of scoring, the observers were aware that sensitivity calculations were made on the basis of only those lesions awarded a confidence rating of 3 or 4. In 31 patients, the results were correlated with findings from surgery, intraoperative US, and histopathologic studies.
To achieve an accurate correlation between the scored lesions and those found at surgery, each observer recorded the individual image number, segmental location, and size of each lesion. If multiple lesions with the same identification parameters were scored, the observers added further comments to distinguish the lesions. At the time of surgery, all of the lesions identified at surgical inspection and intraoperative US were exactly correlated with the CT and MR images by one of the authors (J.W.); histopathologic correlation of the resected specimen was also performed. In 20 patients who did not undergo hepatic resection because of either disease extent or poor cardiac status, the results were correlated with a four-reviewer consensus review (J.W., K.S.N., J.A.G., P.J.R.) together with all other imaging and clinical follow-up data.
Alternative–free response ROC curves produced by using the ROCKIT 0.9B program (courtesy of Metz CE, University of Chicago, 1998) were calculated for each observer and for each examination by plotting the true-positive fraction against the likelihood of obtaining a false-positive image (an image with one or more false-positive lesions) at each confidence level (9). The conventional ROC method does not allow the recording of multiple responses per image or differentiation between images. The alternative–free response ROC is a modified ROC technique that allows multiple responses, thus enabling all of the observers' responses to be correlated with the actual lesions present (10). As with the ROC method, the area under each alternative–free response ROC curve was used to indicate overall performance of both sequences and observers.
The sensitivity for each observer and each modality was also assessed by using only those lesions allocated a confidence rating of 3 or 4. The sensitivity derived from the mean of the results of all four observers was calculated, and the statistical significance of any differences between CT and MR was assessed by using the Student t test. The Student t test was also used to assess any statistically significant intraobserver difference and any statistically significant difference between the means of all four observers in the areas under the alternative–free response ROC curves for each examination. In addition, studies on the surgically confirmed malignant lesions were analyzed separately to rule out possible bias in the consensus review. Statistical significance was associated with a P value less than .05.
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RESULTS |
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TOPAbstractIntroductionMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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One hundred eighty-seven lesions were present in 51 patients, 100 confirmed by surgery and 87 by consensus review. At least one malignant lesion was present in every patient; the maximum number of malignant lesions in any one patient was 11. One hundred sixty-four lesions were malignant, and 23 were benign. One hundred seven of the 164 malignant lesions (65%) were larger than 1 cm, whereas 19 of the 23 benign lesions (83%) were smaller than 1 cm (Table 1). Twenty-one of 35 malignant lesions in five patients were hypervascular at dual-phase CT. Six of these 21 lesions were visible on arterial-phase CT images but not on portal venous–phase CT images (Fig 1). Four of six were scored by all observers on MR images; two more lesions in one patient who had 11 lesions were not detected at initial scoring but were detected at consensus review.
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Surgically Confirmed Malignant Lesions
One hundred surgically confirmed lesions (81, malignant; 19, benign) were present in 31 patients. The numbers of malignant lesions detected by each observer were 67, 63, 67, and 64 for MR and 61, 58, 59, and 60 for CT. The mean sensitivity for malignant lesions was significantly higher for MR (81%) than for CT (74%; P = .007). Although the mean Az for MR imaging (0.84) was greater than the mean Az for CT (0.77), the difference did not reach statistical significance (P = .06). MR was significantly more accurate than CT only for observer 3 (Az for MR, 0.88; Az for CT, 0.75; P < .02)
Eight lesions in three patients were not detected by any observer with either modality. In two other patients, one lesion in each was not scored by any observer at CT and was scored by only one observer and at a low confidence level at MR. The other 71 lesions were each detected by at least one observer at either CT or MR. All 10 false-negative lesions were smaller than 1 cm (six, <5 mm); four of the lesions smaller than 5 mm were on the surface of the liver, and one other 5-mm lesion was identified only at histopathologic examination. In four patients, surgical management was unaltered because the location of the lesions did not alter the surgical approach. A solitary lesion replacing segments 2, 3, and 4 was detected preoperatively in a fourth patient scheduled to undergo a left trisegmentectomy. This was changed to a left hepatectomy with multiple metastasectomies after three additional lesions were found during surgery in the right lobe segments. In one more patient with a single large metastasis, preoperative imaging led to underestimation of the involvement of the diaphragm and the right and middle hepatic veins, and this precluded resection.
Ten lesions in six patients were depicted at MR but not at CT (three, 1–2 cm; seven, <1 cm).
In one patient with four malignant lesions depicted at CT, MR did not show a 1-cm lesion, and a lesion smaller than 1 cm was scored by only two observers at a low confidence level.
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DISCUSSION |
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TOPAbstractIntroductionMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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Recent studies have shown MR imaging with SPIO enhancement to be considerably more sensitive than conventional contrast-enhanced CT (8) and unenhanced MR imaging (13–21) and at least as accurate as CTAP (22) in the depiction of liver lesions. In a recent study by Seneterre et al (22), SPIO-enhanced MR imaging was more accurate than CTAP, because, although both modalities had similar sensitivities, MR had a higher specificity than CTAP, which was associated with a large number of false-positive results. However, CTAP is particularly sensitive in the depiction of small lesions (23,24), and because Seneterre et al (22) used the conventional ROC method, which allows only one response per image, they excluded 10 of 15 small lesions from their analysis. This may have caused bias in favor of SPIO-enhanced MR, because in an earlier study by Hagspiel et al (8), which included an analysis of small lesions (17 of 41 lesions smaller than 1 cm), SPIO-enhanced MR imaging had a sensitivity of only 56%.
By using the alternative–free response ROC method, which allows an observer response for all of the lesions present, we were able to analyze all the lesions in our study. We also used four blinded and independent observers to increase the validity of our findings. Despite the high sensitivity of CTAP, it was not included in our study protocol because it is highly invasive and carries a considerable risk of false-positive results (25). Reliance on an imaging modality with such a low specificity is of some concern when patients may be denied potentially curative surgery on the basis of a false-positive finding. Instead, we compared MR with dual-phase CT because it provides imaging of all extrahepatic sites of spread, it is widely available, and imaging at both the arterial and portal phases of enhancement has the potential to depict additional liver lesions.
The accuracy achieved in our current study (mean Az, 0.82) is less than that of the study by Seneterre et al (22) and that of our previous study (26), which achieved higher accuracy for SPIO-enhanced MR imaging (mean Az, 0.95 and 0.85, respectively). Increasingly aggressive surgery has resulted in referral of patients with multiple small lesions for surgical consideration, and this is reflected in the patient population in our study. More than one-third (57 of 164) of the malignant lesions in our study were smaller than 1 cm.
All preoperative imaging is limited in the depiction of lesions smaller than 1 cm, and this is again demonstrated in our study. When only those lesions larger than 1 cm were analyzed, MR and CT achieved sensitivities of 99% and 94%, respectively. All of the lesions missed at MR were 1 cm or smaller, and in our surgical group, only one 1-cm lesion depicted at CT was missed at MR. MR showed three lesions 1–2 cm and seven smaller than 1 cm that were not depicted at CT (Figs 2, 3).
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Although MR was significantly more sensitive than CT and our results showed an increase in the mean Az for MR imaging compared with that for dual-phase CT, the improvement in the accuracy of MR reached statistical significance for only one observer. Two other studies (28,29) have shown a general trend toward the superiority of MR imaging without statistical significance; however, technical improvements in MR imaging will almost certainly lead to a significant difference between the two modalities in the future.
In this study, although CT was performed on state-of-the-art equipment, MR was not. Three true-positive lesions (two confirmed at intraoperative US and one at follow-up CT) that were not scored by any observer at CT were scored by multiple observers but at a low confidence level at MR. While further developments in helical CT are unlikely to lead to much improvement in the sensitivity of the modality, the introduction of high-performance gradients and phased-array coils that result in increased contrast-to-noise ratio and spatial resolution are likely to result in substantial increases in the sensitivity of MR imaging.
The sensitivity of dual-phase CT in this study was superior to that reported by other authors for conventional dynamic CT (7,8,30). This can be explained by the number of hypervascular lesions in the patient population in our study and by the inherent advantages of helical CT, which improves the detection of small lesions. Six of 21 hypervascular lesions were visible only on arterial-phase images (Fig 1). Although this improved the sensitivity of dual-phase CT, none of the six lesions was influential in disease management because their location did not alter the surgical approach, and in all patients, other lesions were present on portal venous–phase images. Several small benign lesions were clearly seen at CT by all four observers but scored at MR by only two observers because the lesions were difficult to distinguish from vessels. However, only one 5-mm benign lesion seen at CT was not scored by any observer at MR.
Fretz et al (16) have described difficulty in distinguishing small lesions from peripheral vessels that are more conspicuous after SPIO enhancement. Currently, contrast-enhanced CT or gadolinium-enhanced MR is required to distinguish the two; however, dynamic imaging during the injection of SPIO may overcome this problem in the future.
In patients being considered for hepatic resection, although failure to detect small benign lesions does not alter patient treatment, small cysts are still problematic because they are a potential source of false-positive results. At a field strength of 1.5 T, Oudkerk et al (31) recommended T1-weighted breath-hold GRE imaging after SPIO enhancement to detect and characterize focal liver lesions. In their study (31), because susceptibility increases with increasing field strength, the loss of signal from normal liver was sufficient for metastases to be depicted as hyperintense lesions relative to background liver because of paradoxic enhancement. Cysts, on the other hand, were isointense with the adjacent liver and thus eliminated as a cause of false-positive lesions because they have a longer T1 than metastases. At a field strength of 1.0 T, signal loss produced by SPIO enhancement in normal liver is less than that at 1.5 T. In our study, T1-weighted GRE images obtained after SPIO enhancement were particularly insensitive because both cysts and metastases were typically isointense with background liver.
The high signal intensity of vascular structures was also the most frequent cause of false-positive lesions at MR. However, unenhanced images were often helpful in distinguishing vessels from lesions; consequently, false-positive findings were rare (2.6%), and only two were scored by more than one observer (two observers in each case). False-positive findings were also infrequent at CT. Mostly attributed to artifact from perfusion (n = 6) and partial volume averaging (n = 6; three additional false-positive findings attributed to focal fatty change, a dilated duct, and flow artifact in the inferior vena cava), they were never scored by more than one observer. Perfusion-related artifacts at arterial-phase CT are well recognized and in most cases can be identified by their peripheral location and linear, well-defined margins. The elimination of misregistration artifacts with helical CT is likely to have reduced the number of false-positive findings.
Compared with results from MR alone, the combined results from MR and CT showed additional malignant lesions in four patients (confirmed at surgery in one patient and at consensus review in three). However, the increased yield did not alter the management in any of these patients. One additional lesion depicted at CT in a patient to undergo surgery was located in a segment that did not alter the surgical approach; and in three patients with five additional lesions depicted at CT, multiple lesions already shown at MR precluded resection.
Our choice of MR pulse sequences before and after SPIO enhancement requires explanation. Unenhanced images are helpful in distinguishing small lesions from vessels, in the characterization of lesions, and in the distinction of the liver and lung bases superiorly and liver and bowel inferiorly. For T2-weighted images, we used a fast SE sequence before the administration of contrast medium because in a recent study (26) comparing fast SE, fat-suppressed T2-weighted SE, dynamic gadolinium-enhanced fast low-angle shot, and fast SE after SPIO enhancement, fast SE was the most sensitive of the unenhanced sequences. Fast SE images require shorter acquisition times, and as a result, motion artifact is decreased, whereas fat-suppressed T2-weighted SE images were frequently degraded by motion artifact because of an acquisition time greater than 11 minutes. Unenhanced, breath-hold, T1-weighted, fast low-angle shot images are useful for both the detection and characterization of lesions. They add little to the overall examination time, and because the whole of the liver is imaged in a single breath hold, consistently high-quality images free of misregistration and motion artifact are obtained. Both in-phase and opposed-phase images are required to demonstrate focal lesions in a fatty liver, which was present in 8% of the patients in our study.
After the SPIO-enhanced sequence, we used a conventional dual-echo sequence on the basis of the preliminary results of an ongoing study (32) to determine the optimum sequence to use after a SPIO-enhanced sequence at a field strength of 1.0 T. Other studies (33,34) have shown conflicting results with regard to this issue, although it is clear that field strength is influential. In our study, conventional dual-echo images with echo times of 45 and 90 msec were more sensitive than fast SE or GRE images, although the improvement reached statistical significance only in the comparison with GRE imaging. Compared with conventional SE images, fast SE images have inferior lesion sharpness because of inherent blurring due to a reduction in the signal contribution of late echoes. Although this effect was minimal in the fast SE sequence used in this study as a result of a relatively short echo train length and reduced echo spacing, blurring is increased after SPIO enhancement because the liver signal from late echoes is reduced further.
Despite the lower sensitivity of T2-weighted GRE images, they were also included in our imaging protocol because as breath-hold images, they are free of motion artifact, and when combined with the dual-echo sequence may be helpful in increasing confidence in diagnosing possible lesions (Fig 4). Because GRE images are much more sensitive to susceptibility, the loss of signal intensity from background liver is greater than that on SE images. Along with Van Beers et al (35), we found GRE images useful in the segmental localization of lesions because of the high contrast between liver and vessel. However, we also found that small lesions may be obscured by a blooming effect due to the profound loss of signal from the iron in the adjacent liver parenchyma, and we would not recommend the use of GRE images in isolation. SPIO-enhanced T1-weighted images were included to improve the characterization of hemangiomas, which typically become hyperintense on SPIO-enhanced T1-weighted images.
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In summary, SPIO-enhanced MR imaging is more sensitive than dual-phase CT in the depiction of colorectal metastases. Because CT is superior in screening for extrahepatic disease, we would recommend that all patients being considered for segmental hepatic resection undergo SPIO-enhanced MR imaging of the liver and CT of the chest and abdomen. Further studies should focus on improvements in the accuracy of SPIO enhancement for the depiction of malignant lesions smaller than 1 cm.
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Acknowledgments |
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Footnotes |
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From the 1997 RSNA scientific assembly.
Abbreviations: CTAP = CT during arterial portography GRE = gradient echo ROC = receiver operating characteristic SE = spin echo SPIO = superparamagnetic iron oxide
Author contributions: Guarantors of integrity of entire study, P.J.R., J.W.; study concepts, J.W., P.J.R.; study design, J.A.G., J.W., P.J.R., D.W.; definition of intellectual content, J.W., P.J.R., J.A.G.; literature research, J.W.; clinical studies, J.W., P.J.R., K.S.N., J.A.G.; data acquisition, J.W., P.J.R., K.S.N., J.A.G.; data analysis, J.W.; statistical analysis, D.W.; manuscript preparation, J.W.; manuscript editing, P.J.R., K.S.N., J.A.G., D.W.; manuscript review, J.W., P.J.R.
Received March 19, 1998;
revision requested June 5, 1998; revision received July 17, 1998;
accepted September 23, 1998.
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References |
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TOPAbstractIntroductionMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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1.5 cm) malignant hepatic neoplasms. AJR 1995; 164:879-884.This article has been cited by other articles:
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C. D. Frate, C. Zuiani, V. Londero, G. Como, M. Bazzocchi, K. Mortele, and P. R. Ros Comparing Levovist-Enhanced Pulse Inversion Harmonic Imaging and Ferumoxides-Enhanced MR Imaging of Hepatic Metastases Am. J. Roentgenol., May 1, 2003; 180(5): 1339 - 1346. [Abstract] [Full Text] [PDF]
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B. K. Kang, J. H. Lim, S. H. Kim, D. Choi, H. K. Lim, W. J. Lee, and S. J. Lee Preoperative Depiction of Hepatocellular Carcinoma: Ferumoxides-enhanced MR Imaging versus Triple-Phase Helical CT Radiology, January 1, 2003; 226(1): 79 - 85. [Abstract] [Full Text] [PDF]
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K. Mori, J. Scheidler, T. Helmberger, N. Holzknecht, R. Schauer, C. A. Schirren, I. Bittmann, M. Dugas, and M. Reiser Detection of Malignant Hepatic Lesions Before Orthotopic Liver Transplantation: Accuracy of Ferumoxides-Enhanced MR Imaging Am. J. Roentgenol., October 1, 2002; 179(4): 1045 - 1051. [Abstract] [Full Text] [PDF]
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M. A. Haider, M. M. Amitai, D. C. Rappaport, M. E. O'Malley, A. E. Hanbidge, M. Redston, G. A. Lockwood, and S. Gallinger Multi-Detector Row Helical CT in Preoperative Assessment of Small (<=1.5 cm) Liver Metastases: Is Thinner Collimation Better? Radiology, October 1, 2002; 225(1): 137 - 142. [Abstract] [Full Text] [PDF]
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S. K. Kim, S. H. Kim, W. J. Lee, H. Kim, J. W. Seo, D. Choi, H. K. Lim, S. J. Lee, and J. H. Lim Preoperative Detection of Hepatocellular Carcinoma: Ferumoxides-Enhanced Versus Mangafodipir Trisodium--Enhanced MR Imaging Am. J. Roentgenol., September 1, 2002; 179(3): 741 - 750. [Abstract] [Full Text] [PDF]
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K. Kinkel, Y. Lu, M. Both, R. S. Warren, and R. F. Thoeni Detection of Hepatic Metastases from Cancers of the Gastrointestinal Tract by Using Noninvasive Imaging Methods (US, CT, MR Imaging, PET): A Meta-Analysis Radiology, September 1, 2002; 224(3): 748 - 756. [Abstract] [Full Text] [PDF]
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H. J. V. Braga, M. A. Choti, V. S. Lee, E. K. Paulson, E. S. Siegelman, and D. A. Bluemke Liver Lesions: Manganese-enhanced MR and Dual-Phase Helical CT for Preoperative Detection and Characterization—Comparison with Receiver Operating Characteristic Analysis Radiology, May 1, 2002; 223(2): 525 - 531. [Abstract] [Full Text] [PDF]
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S. S. Raman, D. S. K. Lu, S. C. Chen, J. Sayre, F. Eilber, and J. Economou Hepatic MR Imaging Using Ferumoxides: Prospective Evaluation with Surgical and Intraoperative Sonographic Confirmation in 25 Cases Am. J. Roentgenol., October 1, 2001; 177(4): 807 - 812. [Abstract] [Full Text] [PDF]
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J. H. Lim, D. Choi, S. K. Cho, S. H. Kim, W. J. Lee, H. K. Lim, C. K. Park, S. W. Paik, and Y. I. Kim Conspicuity of Hepatocellular Nodular Lesions in Cirrhotic Livers at Ferumoxides-enhanced MR Imaging: Importance of Kupffer Cell Number Radiology, September 1, 2001; 220(3): 669 - 676. [Abstract] [Full Text] [PDF]
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H. J. V. Braga, K. Imam, and D. A. Bluemke MR Imaging of Intrahepatic Cholangiocarcinoma: Use of Ferumoxides for Lesion Localization and Extension Am. J. Roentgenol., July 1, 2001; 177(1): 111 - 114. [Abstract] [Full Text] [PDF]
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Y. Maetani, K. Itoh, C. Watanabe, T. Shibata, F. Ametani, H. Yamabe, and J. Konishi MR Imaging of Intrahepatic Cholangiocarcinoma with Pathologic Correlation Am. J. Roentgenol., June 1, 2001; 176(6): 1499 - 1507. [Abstract] [Full Text] [PDF]
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D. Choi, S. H. Kim, J. H. Lim, W. J. Lee, H.-J. Jang, S. J. Lee, and H. K. Lim Preoperative Detection of Hepatocellular Carcinoma: Ferumoxides-Enhanced MR Imaging Versus Combined Helical CT During Arterial Portography and CT Hepatic Arteriography Am. J. Roentgenol., February 1, 2001; 176(2): 475 - 482. [Abstract] [Full Text] [PDF]
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R. C. Semelka and T. K. G. Helmberger Contrast Agents for MR Imaging of the Liver Radiology, January 1, 2001; 218(1): 27 - 38. [Abstract] [Full Text]
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C. Valls, E. Andía, A. Sánchez, A. Gumà, J. Figueras, J. Torras, and T. Serrano Hepatic Metastases from Colorectal Cancer: Preoperative Detection and Assessment of Resectability with Helical CT Radiology, January 1, 2001; 218(1): 55 - 60. [Abstract] [Full Text]
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S. C. H. Yu, C. T. Liew, W. Y. Lau, T. W. Leung, and C. Metreweli US-guided Percutaneous Biopsy of Small ({<=}1-cm) Hepatic Lesions Radiology, January 1, 2001; 218(1): 195 - 199. [Abstract] [Full Text]
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D. A. Bluemke, E. K. Paulson, M. A. Choti, S. DeSena, and P. A. Clavien Detection of Hepatic Lesions in Candidates for Surgery: Comparison of Ferumoxides-Enhanced MR Imaging and Dual-Phase Helical CT Am. J. Roentgenol., December 1, 2000; 175(6): 1653 - 1658. [Abstract] [Full Text] [PDF]
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K. Mori, H. Yoshioka, Y. Itai, Y. Okamoto, H. Mori, N. Takahashi, and Y. Saida Arterioportal Shunts in Cirrhotic Patients: Evaluation of the Difference Between Tumorous and Nontumorous Arterioportal Shunts on MR Imaging with Superparamagnetic Iron Oxide Am. J. Roentgenol., December 1, 2000; 175(6): 1659 - 1664. [Abstract] [Full Text] [PDF]
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P. Reimer, N. Jähnke, M. Fiebich, W. Schima, F. Deckers, C. Marx, N. Holzknecht, and S. Saini Hepatic Lesion Detection and Characterization: Value of Nonenhanced MR Imaging, Superparamagnetic Iron Oxide-enhanced MR Imaging, and Spiral CT-ROC Analysis Radiology, October 1, 2000; 217(1): 152 - 158. [Abstract] [Full Text]
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J. Ward, J. A. Guthrie, D. J. Scott, J. Atchley, D. Wilson, M. H. Davies, J. I. Wyatt, and P. J. Robinson Hepatocellular Carcinoma in the Cirrhotic Liver: Double-Contrast MR Imaging for Diagnosis Radiology, July 1, 2000; 216(1): 154 - 162. [Abstract] [Full Text]
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C. M. C. Tempany, K. H. Zou, S. G. Silverman, D. L. Brown, A. B. Kurtz, and B. J. McNeil Staging of Advanced Ovarian Cancer: Comparison of Imaging Modalities-Report from the Radiological Diagnostic Oncology Group Radiology, June 1, 2000; 215(3): 761 - 767. [Abstract] [Full Text]
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H. Kondo, M. Kanematsu, H. Hoshi, T. Murakami, T. Kim, M. Hori, M. Matsuo, and H. Nakamura Preoperative Detection of Malignant Hepatic Tumors: Comparison of Combined Methods of MR Imaging with Combined Methods of CT Am. J. Roentgenol., April 1, 2000; 174(4): 947 - 954. [Abstract] [Full Text] [PDF]
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J. Ward, F. Chen, J. A. Guthrie, D. Wilson, J. P. A. Lodge, J. I. Wyatt, and P. J. Robinson Hepatic Lesion Detection after Superparamagnetic Iron Oxide Enhancement: Comparison of Five T2-weighted Sequences at 1.0 T by Using Alternative-Free Response Receiver Operating Characteristic Analysis1 Radiology, January 1, 2000; 214(1): 159 - 166. [Abstract] [Full Text]
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