Hepatocellular carcinoma: detection with gadolinium- and ferumoxides-enhanced MR imaging of the liver.

PURPOSE: To test the hypothesis that the accuracy of gadolinium- and ferumoxides-enhanced magnetic resonance (MR) imaging is different in small (< or =1.5-cm) and large (>1.5-cm) hepatocellular carcinomas (HCCs). MATERIALS AND METHODS: Forty-three consecutive patients with chronic liver disease were enrolled in this study. The imaging protocol included unenhanced breath-hold T1-weighted fast field-echo sequences, unenhanced respiratory-triggered T2-weighted turbo spin-echo (SE) sequences, dynamic gadolinium-enhanced T1-weighted three-dimensional turbo field-echo sequences, and ferumoxides-enhanced T2-weighted turbo SE sequences. Images of each sequence and two sets of sequences (ferumoxides set and gadolinium set) were reviewed by four observers. The ferumoxides set included unenhanced T1- and T2-weighted images and ferumoxides-enhanced T2-weighted turbo SE MR images. The gadolinium set included unenhanced T1- and T2-weighted images and dynamic gadolinium-enhanced three-dimensional turbo field-echo MR images. In receiver operating characteristic (ROC) curve analysis, the sensitivity and accuracy of the sequences were compared in regard to the detection of all, small, and large HCCs. RESULTS: Imaging performance was different with gadolinium- and ferumoxides-enhanced images in the detection of small and large HCCs. For detection of small HCCs, the sensitivity and accuracy with unenhanced and gadolinium-enhanced imaging (gadolinium set) were significantly (P =.017) superior to those with unenhanced and ferumoxides-enhanced imaging (ferumoxides set). The area under the composite ROC curves, or A(z), for the gadolinium set and the ferumoxides set was 0.97 and 0.81, respectively. For large HCC, the ferumoxides set was superior compared with the gadolinium set, but this difference was not statistically significant. Analysis of all HCCs demonstrated no significant differences for gadolinium- and ferumoxides-enhanced imaging. CONCLUSION: For the detection of early HCC, gadolinium-enhanced MR imaging is preferred to ferumoxides-enhanced MR imaging because the former demonstrated significantly greater accuracy in the detection of small HCCs.     

Detection of liver metastases: comparison of gadobenate dimeglumine-enhanced and ferumoxides-enhanced MR imaging examinations

PURPOSE: To compare gadobenate dimeglumine (Gd-BOPTA)-enhanced magnetic resonance (MR) imaging with ferumoxides-enhanced MR imaging for detection of liver metastases. MATERIALS AND METHODS: Twenty consecutive patients known to have malignancy and suspected of having focal liver lesions at ultrasonography (US) underwent 1.0-T MR imaging with gradient-recalled-echo T1-weighted breath-hold sequences before, immediately after, and 60 minutes after Gd-BOPTA injection. Subsequently, MR imaging was performed with turbo spin-echo short inversion time inversion-recovery T2-weighted sequences before and 60 minutes after ferumoxides administration. All patients subsequently underwent intraoperative US within 15 days, and histopathologic analysis of their resected lesion-containing specimens was performed. Separate qualitative analyses were performed to assess lesion detection with each contrast agent. Quantitative analyses were performed by measuring signal-to-noise and contrast-to-noise ratios (CNRs) on pre- and postcontrast Gd-BOPTA and ferumoxides MR images. Statistical analyses were performed with Wilcoxon signed rank and Monte Carlo tests. RESULTS: Sensitivity of ferumoxides-enhanced MR imaging was superior to that of Gd-BOPTA-enhanced MR imaging for liver metastasis detection (P <.05). Ferumoxides MR images depicted 36 (97%) of 37 metastases detected at intraoperative US, whereas Gd-BOPTA MR images depicted 30 (81%) metastases during delayed phase and 20 (54%) during dynamic phase. All six metastases identified only at ferumoxides-enhanced MR imaging were 5-10 mm in diameter. There was a significant increase in CNR between the lesion and liver before and after ferumoxides administration (from 3.8 to 6.8, P <.001) but not before or after Gd-BOPTA injection (from -4.8 to -5.5, P >.05). CONCLUSION: Ferumoxides-enhanced MR imaging seems to be superior to Gd-BOPTA-enhanced MR imaging for liver metastasis detection. Copyright RSNA, 2002     

Detection of malignant hepatic lesions before orthotopic liver transplantation: accuracy of ferumoxides-enhanced MR imaging

OBJECTIVE: The purpose of this study was to evaluate the diagnostic accuracy of ferumoxides-enhanced MR imaging for screening malignant hepatic lesions before orthotopic liver transplantation. MATERIALS AND METHODS: The study comprised 48 patients who underwent MR imaging within 6 months before transplantation. Imaging techniques included unenhanced and ferumoxides-enhanced T1-weighted gradient-echo and T2-weighted fast spin-echo sequences and ferumoxides-enhanced T2(*)-weighted gradient-echo sequences. Qualitative and quantitative analyses were performed; the gold standard was the histopathologic reports of explanted livers. RESULTS: Twenty patients had malignant hepatic lesions, and 24 hepatocellular carcinomas were histopathologically proven. The mean area under the receiver operating characteristic curve and the mean sensitivity were significantly greater for the image sets with ferumoxides-enhanced gradient-echo sequences than for those without these sequences. The mean sensitivity and specificity of all sequences were 85% and 74% on a per-patient basis, respectively. The mean contrast-to-noise ratio was significantly greater for the ferumoxides-enhanced T2(*)-weighted gradient-echo sequences than for any other sequences and for the ferumoxides-enhanced T1-weighted gradient-echo sequences than for unenhanced sequences and the ferumoxides-enhanced T2-weighted fast spin-echo sequences. CONCLUSION: Ferumoxides-enhanced gradient-echo sequences improved the diagnostic accuracy and the sensitivity for detecting malignant hepatic lesions in patients with end-stage cirrhosis of the liver. However, the specificity was not improved even after the administration of ferumoxides because of the false-positive lesions that were mainly the result of fibrotic changes.     

Characterization of Focal Liver Lesions with Superparamagnetic Iron Oxide-Enhanced MR Imaging: Value of Distributional Phase T1-Weighted Imaging

Objective

To determine the potential value of distributional-phase T1-weighted ferumoxides-enhanced magnetic resonance (MR) imaging for tissue characterization of focal liver lesions.

Materials and Methods

Ferumoxides-enhanced MR imaging was performed using a 1.5-T system in 46 patients referred for evaluation of known or suspected hepatic malignancies. Seventy-three focal liver lesions (30 hepatocellular carcinomas [HCC], 12 metastases, 15 cysts, 13 hemangiomas, and three cholangiocarcinomas) were evaluated. MR imaging included T1-weighted double-echo gradient-echo (TR/TE: 150/4.2 and 2.1 msec), T2*-weighted gradient-echo (TR/TE: 180/12 msec), and T2-weighted turbo spin-echo MR imaging at 1.5 T before and after intravenous administration of ferumoxides (15 mmol/kg body weight). Postcontrast T1-weighted imaging was performed within eight minutes of infusion of the contrast medium (distributional phase). Both qualitative and quantitative analysis was performed.

Results

During the distributional phase after infusion of ferumoxides, unique enhancement patterns of focal liver lesions were observed for hemangiomas, metastases, and hepatocellular carcinomas. On T1-weighted GRE images obtained during the distributional phase, hemangiomas showed a typical positive enhancement pattern of increased signal; metastases showed ring enhancement; and hepatocellar carcinomas showed slight enhancement. Quantitatively, the signal-to-noise ratio of hemangiomas was much higher than that of other tumors (p < .05) and was similar to that of intrahepatic vessels. This finding permitted more effective differentiation between hemangiomas and other malignant tumors.

Conclusion

T1-weighted double-echo FLASH images obtained soon after the infusion of ferumoxides, show characteristic enhancement patterns and improved the differentiation of focal liver lesions.     

Dynamic gadolinium-enhanced rapid acquisition spin-echo MR imaging of the liver

Rapid acquisition spin-echo (RASE) magnetic resonance (MR) imaging allows for coverage of the entire liver with highly T1-weighted SE images during a single 23-second breath-holding period. The RASE sequence was implemented in conjunction with rapid intravenous injection of gadopentetate dimeglumine to enable performance of dynamic contrast material-enhanced MR imaging of the liver. Prospective evaluation of 24 patients with 62 liver lesions 1 cm or greater in diameter was performed. Images obtained with RASE were devoid of respiratory-related ghost artifacts or edge blurring. The dynamic contrast-enhanced RASE technique resulted in contrast-to-noise and contrast-to-artifact values and time efficiency measures significantly greater (P less than .05) than those obtained with use of conventional T1- and T2-weighted pulse sequences, indicating a higher likelihood for lesion detectability. Lesion conspicuity was maximal during or immediately following bolus administration of gadopentetate dimeglumine, with lesions often becoming obscured at delayed postcontrast imaging.     

Dynamic gadolinium-enhanced MR imaging of the spleen: normal enhancement patterns and evaluation of splenic lesions

The authors studied the ability to improve detection of splenic lesions during suspended respiration with dynamic gadolinium-enhanced T1-weighted spin-echo magnetic resonance (MR) imaging. In the first phase of the study, normal splenic contrast material enhancement patterns were assessed in 10 control patients without splenic lesions. A heterogeneous signal intensity pattern was observed in 11 patients with splenic lesions during bolus injection of gadopentetate dimeglumine, with conversion to homogeneous enhancement 1 minute later. Mean splenic enhancement was 321% during bolus injection, with a rapid return toward baseline signal intensity thereafter. In the second phase, evaluation of 18 splenic lesions detected with contrast-enhanced computed tomography in 11 patients revealed that dynamic gadolinium-enhanced MR pulse sequences significantly improved lesion conspicuity and detectability compared with conventional T1-and T2-weighted pulse sequences. Contrast-to-artifact ratio measurements were 0.5, 3.7, and 9.3 for conventional T1-weighted, T2-weighted, and dynamic gadolinium-enhanced MR images, respectively.     

Preoperative detection of hepatocellular carcinoma: ferumoxides-enhanced versus mangafodipir trisodium-enhanced MR imaging

OBJECTIVE: The purpose of our study was to compare the diagnostic accuracy and lesion conspicuity of ferumoxides-enhanced MR imaging with those of mangafodipir trisodium-enhanced MR imaging for the preoperative detection of hepatocellular carcinoma. SUBJECTS AND METHODS: Twenty-one patients with 39 hepatocellular carcinomas underwent ferumoxides-enhanced and mangafodipir trisodium-enhanced MR imaging. The diagnosis was established by pathologic examination after surgical resection in all patients. Five MR sequences were obtained 30 min after ferumoxides administration, and two MR sequences were obtained before and 15 min after mangafodipir trisodium administration. Three observers independently interpreted both MR images of all sequences on a segment-by-segment basis. The diagnostic accuracy of MR imaging was assessed using receiver operating characterizing analysis. Lesion (hepatocellular carcinoma > 10 mm in diameter)-to-liver contrast-to-noise ratio was calculated on MR images. RESULTS: Ferumoxides-enhanced MR imaging (A(z) = 0.971) was significantly more accurate (p < 0.05) than mangafodipir trisodium-enhanced MR imaging (A(z) = 0.950). The mean sensitivity of ferumoxides-enhanced MR imaging (86%) was significantly greater (p < 0.05) than that of mangafodipir trisodium-enhanced MR imaging (44%) in lesions smaller than 10 mm. The mean lesion-to-liver contrast-to-noise ratio of hepatocellular carcinoma on ferumoxides-enhanced MR imaging (13.7 +/- 8.8) was significantly greater than on mangafodipir trisodium-enhanced MR imaging (5.4 +/- 5.1) (p < 0.01). CONCLUSION: Ferumoxides-enhanced MR imaging has superior diagnostic accuracy in lesions smaller than 10 mm and superior lesion conspicuity compared with mangafodipir trisodium-enhanced MR imaging for the preoperative detection of hepatocellular carcinoma.     

Hepatic MR imaging using ferumoxides: prospective evaluation with surgical and intraoperative sonographic confirmation in 25 cases

OBJECTIVE: The purpose of our study was to evaluate the sensitivity and accuracy of ferumoxides-enhanced MR imaging in comparison with surgery and intraoperative sonography. SUBJECTS AND METHODS: We prospectively evaluated 25 consecutive studies in 24 patients who underwent ferumoxides-enhanced hepatic MR imaging before surgery and intraoperative sonography. Both 1.5-T scanners (13 cases) and 0.2-T scanners (12 cases) were used. Turbo spin-echo T2-weighted sequences were performed before and after the administration of ferumoxides and the images were compared. Lesions were classified as solid or nonsolid and tabulated on standard liver maps. The liver maps from MR imaging were compared with those from surgery and intraoperative sonography. For lesions greater than 1 cm, the regions of interest were measured and contrast-to-noise ratio was calculated. RESULTS: Of 93 solid lesions found at surgery, 69 were seen on unenhanced MR imaging (sensitivity, 74.2%) and 87 were seen on ferumoxides-enhanced MR imaging (sensitivity, 93.5%) (p < 0.05). Of the seven benign lesions (five cysts, two hemangiomas) found at surgery, all were correctly identified as benign on MR imaging. Two lesions identified as solid before surgery were not found at surgery. Mean lesion contrast-to-noise ratio for the unenhanced scans was 22.9 and 34.5 (p < 0.001) for the ferumoxides-enhanced scans. Subanalysis of 1.5- and 0.2-T MR imaging revealed similar results with significant (p < 0.05) increases in sensitivity for both. The average size of the lesions missed before surgery was 0.7 cm. CONCLUSION: Turbo spin-echo T2-weighted ferumoxides-enhanced MR imaging at either 1.5 or 0.2 T has value in preoperative liver assessment.     

Malignant hepatic tumor detection with ferumoxides-enhanced MR imaging with a 1.5-T system: comparison of four imaging pulse sequences

The purpose of our study was to compare observer performance in the detection of malignant hepatic tumors with ferumoxides-enhanced magnetic resonance (MR) images obtained with proton density-weighted spin-echo (SE), T2-weighted fast SE, T2*-weighted gradient-recalled-echo (GRE), and proton density-weighted echo-planar (EP) sequences. Ferumoxides-enhanced MR images obtained with the four sequences in 50 patients with 92 solid malignant and 64 nonsolid benign lesions were retrospectively analyzed. Image review was conducted on a segment-by-segment basis; a total of 397 liver segments was reviewed separately for solid and nonsolid lesions by three independent readers. Observer performance was evaluated with receiver operating characteristic analysis. Lesion-to-liver contrast-to-noise ratio was higher with SE and EP than with GRE and fast SE images for solid lesions (P < 0.05), and higher with fast SE and SE than with GRE images for nonsolid lesions (P < 0.01). Proton density-weighted SE and T2-weighted fast-SE images were superior to T2*-weighted GRE and proton density-weighted EP images for detection of malignant hepatic tumors. T2-weighted fast SE images were the best for detection of nonsolid lesions. T2-weighted fast SE images that were comparable to proton density-weighted SE images for solid tumor detection, that were the best for nonsolid lesion detection, and that had an acquisition time of one third to half of that of SE imaging may be able to replace SE images for ferumoxides-enhanced liver imaging.     

Nodule-in-nodule appearance of hepatocellular carcinomas: comparison of gadolinium-enhanced and ferumoxides-enhanced magnetic resonance imaging

PURPOSE: To perform comparison of gadolinium-enhanced and ferumoxides-enhanced magnetic resonance imaging (MRI) in the detection of nodule-in-nodule appearance of hepatocellular carcinomas (HCCs). MATERIALS AND METHODS: During a recent 45-month period, we had eight patients (five men and three women; age range, 63-84 years; mean, 71 years) with HCCs with nodule-in-nodule appearance who underwent gadolinium-enhanced MRI, ferumoxides-enhanced MRI, and computed tomography during arterial portography (CTAP) and computed tomography during hepatic arteriography (CTHA), combined and separately, within an interval of two weeks. Two blinded radiologists in consensus retrospectively evaluated three sets of sequences: unenhanced T1- and T2-weighted MR, gadolinium-enhanced MR, and ferumoxides-enhanced MR images in random order of patients and imaging sequences. The depiction degree of nodule-in-nodule appearance of HCC was evaluated in a semiquantitative fashion. The sensitivities of unenhanced T1- and T2-weighted, gadolinium-enhanced, and ferumoxides-enhanced MR images were compared with McNemar's test. RESULTS: The eight HCCs with nodule-in-nodule appearance ranged in size from 16-26 mm (mean, 20.0 +/- 4.0 mm), and there existed nine internal HCC foci ranging in size from 5-14 mm (mean, 7.9 +/- 3.5 mm). On gadolinium-enhanced MR images, the nodule-in-nodule appearance of HCC was typically seen as hypervascular foci in an iso- or hypovascular area: the depiction degree of nodule-in-nodule appearance was distinct in two lesions, equivocal in three, and absent in three. On ferumoxides-enhanced MR images, it was typically seen as hyperintense foci in a hypointense area: the depiction degree was distinct in four, moderate in one, and absent in three. The sensitivities for detection of nodule-in-nodule appearance were 25%, 25%, and 63% on T1- and T2-weighted, gadolinium-enhanced, and ferumoxides-enhanced MR images, respectively, but there was no significant difference in sensitivity. CONCLUSION: Nodule-in-nodule appearance of HCCs can be seen on ferumoxides-enhanced MR images, in some cases more clearly than on gadolinium-enhanced MR images, particularly when the background nodule shows hyperintensity on precontrast T1-weighted images. Ferumoxides-enhanced MRI may be considered when development of malignant foci is suspected during routine examinations.     

Renal lesions: controlled comparison between CT and 1.5-T MR imaging with nonenhanced and gadolinium-enhanced fat-suppressed spin-echo and breath-hold FLASH techniques.

Nonenhanced and gadolinium-enhanced fat-suppressed spin-echo and breath-hold fast low-angle shot (FLASH) magnetic resonance (MR) imaging techniques were compared with iodine contrast material-enhanced computed tomography (CT) for the detection and characterization of renal masses. MR studies included T1-weighted fat-suppressed spin-echo (T1FS) and FLASH images followed by rapid injection of gadopentetate dimeglumine and a repeated FLASH image obtained at 1 second, a T1FS image at 30 seconds, and a FLASH image at 10 minutes. Of 38 patients, 17 had renal cysts, 18 had solid tumors, two had cortical scarring, and one had a hypertrophied column of Bertin. With contrast-enhanced T1FS, contrast-enhanced FLASH, and CT images, 114, 110, and 109 lesions, respectively, were detected. With MR imaging and CT, cysts smaller than 5 mm in diameter and solid tumors as small as 1 cm in diameter were detected. With combined contrast-enhanced FLASH and T1FS images, 112 lesions were correctly characterized as cystic or solid; with nonenhanced T1FS images, 110; with nonenhanced FLASH images, 107; and with nonenhanced CT, 103.     

Ferumoxides-enhanced double-echo T2-weighted MR imaging in differentiating metastases from nonsolid benign lesions of the liver

PURPOSE: To investigate whether ferumoxides-enhanced double-echo T2-weighted magnetic resonance (MR) imaging alone can allow differentiation of metastases from benign lesions in the noncirrhotic liver. MATERIALS AND METHODS: At retrospective review of files and images, 60 lesions (22 metastases, 20 hemangiomas, and 18 cysts) were identified in 42 patients. All fast spin-echo T2-weighted MR images obtained before and after administration of ferumoxides with short (80-90 msec) and long (180-250 msec) echo times (TEs) were acquired with a 1.5-T system. Differences in lesion-to-liver signal intensity ratio between images obtained with long and short TEs were calculated. Data from all 60 lesions were entered into a receiver operating characteristic analysis. Three independent readers scored their observations of each lesion with a confidence level of 1-5. The diagnostic accuracy of each analysis method was determined by calculating the area under each reader-specific receiver operating characteristic curve. Interobserver agreement was calculated with the use of chance-corrected kappa statistics. Relative sensitivity, specificity, and accuracy of characterizing benign lesions with each method were calculated. RESULTS: Markedly low signal intensity and lesion-to-liver ratio on ferumoxides-enhanced images were observed with hemangioma. The difference of lesion-to-liver ratio between long and short TEs on ferumoxides-enhanced images was significantly different from that of unenhanced images and that of metastases or cysts. Interobserver agreement was good to excellent. Ferumoxides-enhanced images (with short and long TEs) showed significantly higher diagnostic accuracy than that of unenhanced images (with short or short and long TEs). Ferumoxides-enhanced images showed similar sensitivity, specificity, and accuracy when all images were reviewed together. CONCLUSION: Ferumoxides-enhanced T2-weighted MR images appear useful in differentiating metastases from benign (nonsolid) lesions in the liver.     

Focal nodular hyperplasia of the liver on ferumoxides-enhanced MR imaging: features on conventional spin-echo, fast spin-echo and gradient-echo pulse sequences

The aim of this study was to assess the efficacy of a superparamagnetic iron oxide, ferumoxides, in the detection and characterization of focal nodular hyperplasia (FNH) on MR conventional spin-echo (SE), fast spin-echo (FSE) and gradient-echo (GRE) images. Fourteen adults with 27 FNHs were evaluated at 1.5 T before and after injection of ferumoxides. T1-weighted and T2-weighted SE, T2-weighted FSE and T2^*-weighted GRE sequences were used and analysed qualitatively and quantitatively. One hundred percent of FNHs showed a significant postcontrast decrease in signal intensity on T2- and T2*-weighted images. Heavily T2-weighted SE images showed the maximum decrease in FNH signal-to-noise ratio (S/N). Postcontrast GRE T2^*-weighted images improved the detection of the central scar and the delineation of FNHs and demonstrated the best lesion-to-liver contrast-to-noise ratio (C/N). Postcontrast T1-weighted SE images showed the least lesion-to-liver C/N. Ferumoxides-enhanced MR imaging can help detect and characterize FNH. Conventional pre- and postcontrast T2-weighted SE images and postcontrast GRE T2*-weighted images should be used preferentially. Received: 30 November 1998; Revised: 5 April 1999; Accepted: 6 April 1999     

Focal liver lesions: SPIO-, gadolinium-, and ferucarbotran-enhanced dynamic T1-weighted and delayed T2-weighted MR imaging in rabbits

PURPOSE: To compare a superparamagnetic iron oxide (SPIO), VSOP-C184, with a gadopentetate dimeglumine with regard to signal-enhancing effects on T1-weighted dynamic magnetic resonance (MR) images and with another SPIO contrast medium with regard to signal-reducing effects on delayed T2-weighted MR images. MATERIALS AND METHODS: All experiments were approved by the responsible Animal Care Committee. Twenty rabbits (five for each contrast agent and dose) implanted with VX-2 carcinoma were imaged at 1.5 T. VSOP-C184 at 0.015 and 0.025 mmol Fe/kg was compared with gadopentetate dimeglumine at 0.15 mmol Gd/kg and ferucarbotran at 0.015 mmol Fe/kg. The imaging protocol comprised a T1-weighted dynamic gradient-echo (GRE) MR before injection and at 6-second intervals for up to 42 seconds after injection and a T2-weighted turbo spin-echo MR before and 5 minutes after injection. Images were evaluated quantitatively, and contrast media were compared by using nonparametric analysis of variance. RESULTS: At dynamic T1-weighted GRE MR imaging with 0.015-mmol Fe/kg VSOP-C184, 0.025-mmol Fe/kg VSOP-C184, gadopentetate dimeglumine, and ferucarbotran, the median peak contrast-to-noise ratio (CNR) was 20.7 (25th percentile, 16.3; 75th percentile, 22.6), 24.2 (25th percentile, 19.3; 75th percentile, 28.5), 16.4 (25th percentile, 13.7; 75th percentile, 20.3), and 14.0 (25th percentile, 11.4; 75th percentile, 16.8), respectively. Both doses of VSOP-C184 yielded significantly higher CNR (P < .05) than the other two agents. At T2-weighted turbo spin-echo imaging with 0.015-mmol Fe/kg VSOP-C184, 0.025-mmol Fe/kg VSOP-C184, gadopentetate dimeglumine, and ferucarbotran, the median CNR was 15.0 (25th percentile, 13.4; 75th percentile, 21.3), 15.7 (25th percentile, 14.5; 75th percentile, 19.8), 11.3 (25th percentile, 8.2; 75th percentile, 12.2), and 15.7 (25th percentile, 12.5; 75th percentile, 22.4), respectively. There was no significant difference between VSOP-C184 and ferucarbotran; both had a significantly higher CNR than did gadopentetate dimeglumine. CONCLUSION: VSOP-C184 produces higher liver-to-tumor contrast at dynamic T1-weighted imaging than does gadopentetate dimeglumine; at delayed T2-weighted imaging, the contrast is comparable to that achieved with ferucarbotran.     

Characterization of focal hepatic lesions with ferumoxides-enhanced MR imaging: utility of T1-weighted spoiled gradient recalled echo images using different echo times

PURPOSE: To evaluate the different signal characteristics of focal hepatic lesions on ferumoxides-enhanced MR imaging, including T1-weighted spoiled gradient recalled echo (GRE) images using different echo times (TE) and T2- and T2*-weighted images. MATERIALS AND METHODS: Ferumoxides-enhanced MR imaging was performed using a 1.5-T system in 46 patients who were referred for evaluation of known or suspected hepatic malignancies. One hundred and seven lesions (42 hepatocellular carcinomas [HCC], 40 metastases, 13 cysts, eight hemangiomas, three focal nodular hyperplasias [FNHs], and one cholangiocarcinoma) were evaluated. Postcontrast MR imaging included 1) T2-weighted FSE; 2) T2*-weighted GRE; 3) T1-weighted spoiled GRE using moderate (TE = 4.2-4.4 msec) TE; and 4) minimum (TE = 1.8-2.1 msec) TE. Signal intensities of the focal lesions were rated by two radiologists in conference as follows: hypointense, isointense or invisible, hyperintense, and markedly hyperintense. Lesion-to-liver contrast-to-noise ratio (C/N) was measured by one radiologist for a quantitative assessment. RESULTS: On ferumoxides-enhanced FSE images, 92% of cysts were "markedly hyperintense" and most of the other lesions were "hyperintense", and the mean C/N of cysts was significantly higher than that of other focal lesions. T2*-weighted GRE images showed most lesions with similar hyperintensities and the mean C/N was not significantly different between any two types of lesion. T1-weighted GRE images using moderate TE showed all FNHsand hemangiomas, 29 (69%) HCCs and eight (20%) metastases as "hyperintense". On T1-weighted GRE images using minimum TE, however, all HCCs and metastasis except one were iso- or hypointense, while all of the FNHs and hemangiomas were hyperintense. Ring enhancement was highly suggestive of malignant lesions, and was more commonly seen on the minimum TE images than on the moderate TE images. CONCLUSION: Addition of T1-weighted GRE images using minimum and moderate TE is helpful for characterizing focal lesions in ferumoxides-enhanced MR imaging.     

Inversion-recovery echo-planar MR in adult brain neoplasia.

PURPOSEA T1-weighted multishot inversion-recovery (IR) echo-planar MR imaging (EPI) sequence was developed to improve intracranial tissue differentiation; its diagnostic utility was compared with that of conventional axial T1-weighted spin-echo and axial T2-weighted turbo spin-echo sequences.METHODSEighteen patients with known or suspected primary or metastatic brain neoplasia were imaged in a 1.5-T unit with IR-EPI sequences. Three observers measured gray/white matter contrast-to-noise ratios and subjectively compared IR-EPI sequences with T1-weighted spin-echo and T2-weighted turbo spin-echo sequences for gray/white matter discrimination, visibility of intracranial and vascular structures, overall lesion conspicuity, size of lesion(s), and presence and severity of artifacts.RESULTSTwenty-four lesions (including neoplasia, infarction, treatment-associated encephalomalacia, nonneoplastic white matter signal abnormalities, and basilar artery dolichoectasia) were detected in 12 patients. Basilar artery dolichoectasia was not included in subsequent statistical analysis. Pulsatile flow artifacts were markedly reduced on IR-EPI sequences relative to those on T1-weighted spin-echo sequences. Gray/white matter contrast was greater on IR-EPI images than on T1-weighted spin-echo images. Periaqueductal gray matter, basal ganglia, optic tracts, cranial nerve V, and claustrum were seen better or as well on IR-EPI images as compared with T1-weighted spin-echo images. IR-EPI was more sensitive to magnetic sensitivity effects, with resultant decreased visibility of cranial nerves VII and VIII and the orbital portion of the optic nerves. For noncontrast sequences, lesion conspicuity was better on IR-EPI images than on T1-weighted spin-echo images in 16 (70%) of 23 lesions and was equal on the two sequences in seven (30%) of 23 lesions. Lesion size, including surrounding edema, was greater on IR-EPI images than on T2-weighted turbo spin-echo images in two (9%) of 23 cases and equal in 21 (91%) of 23 cases. Hyperintense foci of methemoglobin were more conspicuous on T1-weighted spin-echo images.CONCLUSIONMultishot IR-EPI is superior to conventional T1-weighted spin-echo imaging for parenchymal tissue contrast and lesion conspicuity, and is equal to T2-weighted turbo spin-echo imaging in sensitivity to pathologic entities.     

T2-weighted breath-hold MRI of the liver at 1.0 T: Comparison of turbo spin-echo and HASTE sequences with and without fat suppression

To compare the clinical usefulness of T2-weighted breath-hold sequences for imaging the liver, 33 patients with 97 focal hepatic lesions were studied with a 1.0-T scanner by using T2-weighted breath-hold turbo spin-echo (SE) sequences and T2-weighted breath-hold half-Fourier single-shot turbo SE (HASTE) sequences with and without fat suppression. Images were quantitatively analyzed for liver signal-to-noise ratio (SNR) and lesion-to-liver contrast-to-noise ratios (CNR). Qualitative analysis was performed for lesion conspicuity, motion artifacts, and anatomic sharpness of extrahepatic structures. Breath-hold turbo SE imaging with fat suppression showed the highest CNR for cystic lesions and the best lesion conspicuity for cystic and solid lesions among the four sequences. For solid lesions, there was no significant difference of lesion-to-liver CNR between them. HASTE sequence was superior to turbo SE sequences in terms of motion artifacts; however, the usefulness for evaluating focal hepatic lesions was limited compared with turbo SE sequence with fat suppression. Addition of fat suppression was not helpful for HASTE imaging because of decreased lesion conspicuity and extrahepatic details without the advantage of reducing motion artifacts. This study suggests that turbo SE sequence with fat suppression is most useful for breath-hold T2-weighted liver imaging at 1.0 T. Addition of imaging without fat suppression can be considered for evaluating extrahepatic structures. HASTE sequence may have a role for imaging uncooperative patients due to absence of motion artifacts.     

Focal liver disease: comparison of dynamic contrast-enhanced CT and T2-weighted fat-suppressed, FLASH, and dynamic gadolinium-enhanced MR imaging at 1.5 T.

Dynamic contrast medium-enhanced computed tomography (CT), T2-weighted fat-suppressed spin-echo (T2FS) magnetic resonance (MR) imaging, and breath-hold T1-weighted fast low-angle shot (FLASH) MR imaging before and after dynamic gadopentetate dimeglumine injection were compared in 73 patients with clinically suspected liver disease. Observer confidence for presence of focal lesions was determined by using receiver operating characteristic analysis. For all MR images, hepatic lesion-liver signal-to-noise ratios were evaluated qualitatively. and resolution and presence of artifacts were evaluated qualitatively. Lesion detection was greatest with T2FS (n = 272) and enhanced FLASH (n = 244) and was statistically greater with both of these than with CT (n = 220) and FLASH (n = 219) (P less than .03). Correct lesion characterization was greatest with enhanced FLASH (n = 236) (P less than .01), followed by CT (n = 199), FLASH (n = 164), and T2FS (n = 144). Enhanced FLASH was particularly successful in characterization of 5-mm- to 1.5-cm-diameter lesions as cystic or solid.     

Conspicuity of hepatocellular nodular lesions in cirrhotic livers at ferumoxides-enhanced MR imaging: importance of Kupffer cell number

PURPOSE: To correlate the conspicuity of hepatocellular carcinomas and dysplastic nodules on ferumoxides-enhanced magnetic resonance (MR) images with the number of Kupffer cells in the hepatic lesions, as compared with that in background liver in histopathologic findings. MATERIALS AND METHODS: Sixty-nine histopathologically proved moderately or poorly differentiated hepatocellular carcinomas, 10 well-differentiated hepatocellular carcinomas, and 19 dysplastic nodules were retrospectively studied in 68 patients with cirrhosis who underwent ferumoxides-enhanced MR imaging. The contrast-to-noise ratio between the nodules and surrounding parenchyma was calculated at T2-weighted fast spin-echo imaging, and the difference in the number of Kupffer cells between the nodules and surrounding hepatic tissue was calculated histopathologically. The results of MR imaging and histopathologic examination were correlated. RESULTS: All 69 moderately or poorly differentiated hepatocellular carcinomas had high contrast-to-noise ratios at MR imaging and large differences in the number of Kupffer cells. Six of the 10 well-differentiated hepatocellular carcinomas had contrast-to-noise ratios of zero or nearly zero, and five of these had little difference in the number of Kupffer cells. All 19 dysplastic nodules had contrast-to-noise ratios of zero or nearly zero, and there were virtually no differences in the number of Kupffer cells. CONCLUSION: Hepatocellular nodule conspicuity at ferumoxides-enhanced MR imaging depends on differences in the number of Kupffer cells within a nodule and the surrounding cirrhotic liver; moderately or poorly differentiated hepatocellular carcinomas can be distinguished from well-differentiated hepatocellular carcinomas and dysplastic nodules.     

Targeting of hematopoietic progenitor cells with MR contrast agents

PURPOSE: To label human hematopoietic progenitor cells with various magnetic resonance (MR) imaging contrast agents and to obtain 1.5-T MR images of them. MATERIALS AND METHODS: Hematopoietic progenitor cells, labeled with ferumoxides, ferumoxtran, magnetic polysaccharide nanoparticles-transferrin, P7228 liposomes, and gadopentetate dimeglumine liposomes underwent MR imaging with T1- and T2-weighted spin-echo and fast field-echo sequences. Data were analyzed by measuring MR signal intensities and R1 and R2* relaxation rates of labeled cells and nonlabeled control cells. Mean quantitative data for the various contrast agent groups were assessed for significant differences compared with control cells by means of the Scheffe test. As a standard of reference, MR imaging data were compared with electron microscopic and spectrometric data. RESULTS: For all contrast agents, intracellular cytoplasm uptake was demonstrated with electron microscopy and was quantified with spectrometry. When compared with nonlabeled control cells, progenitor cells labeled with iron oxides showed significantly (P <.05) increased R2*. Cells labeled with gadopentetate dimeglumine liposomes showed significantly increased R1. Detection thresholds were 5 x 10(5) cells for gadopentetate dimeglumine liposomes and ferumoxtran, 2.5 x 10(5) cells for ferumoxides and P7228 liposomes, and 1 x 10(5) cells for magnetic polysaccharide nanoparticles-transferrin. CONCLUSION: Hematopoietic progenitor cells can be labeled with MR contrast agents and can be depicted with a standard 1.5-T MR imager.