Contrast-enhanced MR imaging of the liver: Comparison between Gd-BOPTA and mangafodipir

The purpose of the study was to evaluate the MR contrast agents gadolinium benzyloxypropionictetro-acetate (Gd-BOPTA) and Mangafodipir for liver enhancement and the lesion-liver contrast on T1W spin-echo (SE) and gradient-recalled-echo (GRE) images. Fifty-one patients (three groups of 17 patients each) with known or suspected liver lesions were evaluated with T1W SE (300/12) and GRE (77-80/2.3-2.5/80°) images before and after intravenous (IV) Gd-BOPTA (0.1 or 0.05 mmol/kg) or Mangafodipir (5 μmol/kg) in phase II to III clinical trials. Quantitative analysis by calculating liver signal-to-noise ratio (SNR), lesion-liver contrast-to-noise ratio (CNR), and spleen-liver CNR was performed. Liver SNR and spleen-liver CNR were always significantly increased postcontrast. SNR was highest after application of 0.1 mmol/kg Gd-BOPTA (51.3 ± 3.6, P < .05). CNR was highest after Mangafodipir (?22.6 ± 2.7), but this was not significantly different from others (P = .07). Overall, GRE images were superior to SE images for SNR and CNR. Mangafodipir and Gd-BOPTA (0.1 mmol/kg) provide equal liver enhancement and lesion conspicuity postcontrast. By all criteria, contrast-enhanced T1-weighted GRE were comparable to SE images.     

MR imaging of liver metastases at 1.5 T: similar contrast discrimination with T1- and T2-weighted pulse sequences

The authors evaluated soft-tissue contrast on spin-echo (SE) proton density-weighted, SE T2-weighted, SE short-echo-time (TE) T1-weighted, and gradient-echo (GRE) images of 34 patients with known hepatic tumors who underwent high-field-strength (1.5-T) magnetic resonance imaging. For solid liver tumors, the difference in the mean lesion-liver contrast-to-noise ratios (C/Ns) with T1- (GRE and SE) and T2-weighted pulse sequences was not statistically significant (P greater than .05). For nonsolid liver tumors, the T2-weighted images provided significantly greater (P less than .05) mean lesion-liver C/N than T1-weighted GRE images. Mean liver signal-to-noise ratio was significantly greater on T1-weighted GRE (P less than .0001) and T1-weighted SE (P less than .05) images than on T2- and proton density-weighted images. Qualitative analysis of T1-weighted (SE and GRE) images and proton density- plus T2-weighted images showed that lesion conspicuity was similar in 25 of 32 patients (78%). The results suggest that liver tumor imaging at high field strength can be performed with short-TE T1-weighted (SE or GRE) or conventional T2-weighted pulse sequences.     

Delayed MR imaging of hepatocellular carcinoma enhanced by gadobenate dimeglumine (Gd-BOPTA).

The purpose of this study was to determine the efficacy of gadobenate dimeglumine (Gd-BOPTA)-enhanced magnetic resonance (MR) imaging for evaluation of hepatocellular carcinoma HCC. MR images were obtained in 14 patients with 31 HCC nodules as a part of a phase III clinical trial. T1- and T2-weighted images were obtained before and after iv administration of 0.1 mmol/kg of Gd-BOPTA. Two blinded readers evaluated pre- and delayed postcontrast images separately for detection of tumor nodules. Quantitative measurements of signal-to-noise (SNR) and tumor/liver contrast-to-noise (CNR) ratios were also performed. A signal/intensity ratio was calculated. Tumor enhancement was correlated with histologic findings. Consensus agreement of precontrast T1- and T2-weighted images revealed 23/31 HCC nodules in 14 patients; postcontrast T1-weighted images demonstrated 24/31 HCC nodules in the same number of patients. Combining both pre- and postcontrast images, 27/31 lesions were detected. Four patients had four well-differentiated HCC nodules detected only on postcontrast images, while three well-differentiated lesions in two patients were only seen on precontrast images. Quantitative evaluation showed an SNR ratio increase in both liver parenchyma and HCC nodules, as well as a significant increase in the absolute CNR ratio on postcontrast T1-weighted gradient-recalled images (P < 0.05). Well-differentiated HCC lesions showed a greater enhancement than poorly differentiated HCC lesions.     

A comparative study between Gd-BOPTA, a biliary excretion contrast medium, and Gd-DTPA in the magnetic resonance imaging of the rat liver

A new lipophilic compound, Gd-BOPTA, presenting a high rate (38.6%) of biliary excretion was tested as an hepato-specific MR contrast agent. Its adequacy was compared to that of Gd-DTPA in laboratory animals. T1-weighted spin-echo sequences (TR 220 ms, TE 20 ms) both before and after the administration of the 2 contrast agents (doses: 0.25, 0.5, and 1.0 mmol/kg) showed better liver enhancement with Gd-BOPTA than with Gd-DTPA. Gd-BOPTA superiority was more evident at lower doses, while at 1.0 mmol/kg a comparable enhancement was achieved. Inversion recovery sequence at the T-null of liver parenchyma before contrast (TR 800 ms, TE 30 ms, TI 100 ms) was performed after the injection of 0.1 and 0.5 mmol/kg of Gd-DTPA and Gd-BOPTA. This sequence allowed the good and long-lasting liver enhancement achieved with Gd-BOPTA to be even better demonstrated, while Gd-DTPA provided only a slight and early enhancement with 0.1 mmol/kg and returned to baseline values 60' after the injection of the highest dose (0.5 mmol/kg). Gd-BOPTA proved to be a good contrast agent to obtain prolonged liver enhancement, thus providing the radiologist with the long time needed to acquire conventional T1-weighted pulse sequences.     

Evaluation of three-dimensional fast spoiled gradient recalled acquisition in the steady state (FSPGR) using ultra magnetic field 3-Tesla MRI for optimal pulse sequences of T1-weighted imaging

The advantage of the higher signal-to-noise ratio (SNR) of 3-Tesla magnetic resonance imaging (3TMRI) contributes to the improvement of spatial and temporal resolution. However, T1-weighted images of the brain obtained by the spin-echo (SE) method at 3T MR are not satisfactory for clinical use because of radiofrequency (RF) field inhomogeneity and prolongation of the longitudinal relaxation time (T1) of most tissues. We evaluated optimal pulse sequences to obtain adequate T1 contrast, high gray matter/white matter contrast, and suitable postcontrast T1-weighted images using the three-dimentional (3D) fast spoiled gradient recalled acquisition in the steady state (FSPGR) method instead of the SE method. For the optimization of T1 contrast, the Ernst angle of the optimal flip angle (FA) was obtained from the T1 value of cerebral white matter with the shortest TR and TE. Then the most appropriate FA, showing the maximum contrast-to-noise ratio (CNR) and SNR, was obtained by changing the FA every 5 degrees at about the level of the Ernst angle. Image uniformity was evaluated by a phantom showing similar T1 and T2 values of cerebral white matter. In order to evaluate the effect of the contrast enhancement, signal intensity was compared by the same method using a phantom filled with various dilutions of contrast media. Moreover, clinical studies using full (0.1 mmol/kg) and half (0.05 mmol/kg) doses of Gd-DTPA were carried out with the most appropriate parameters of the 3D-FSPGR method. These studies indicated that the optimal pulse sequences for obtaining an adequate T1-weighted image of the brain using 3D-FSPGR are 9/2 msec (TR/TE) and 13 degrees (FA).     

Conventional and rapid MR imaging of the liver with Gd-DTPA

Twenty-three patients with malignant hepatic tumors underwent magnetic resonance (MR) imaging before and after intravenous administration of gadolinium-diethylene-triaminepentaacetic acid (DTPA). Two different doses were used, 0.1 mmol/kg and 0.2 mmol/kg. The larger dose proved to be more effective than the smaller dose. The signal-enhancement-to-noise ratio was significantly larger in the tumor than in the liver (2 alpha less than or equal to .05). In a moderately T1-weighted spin echo (SE) sequence (SE 400/30) (repetition time [TR] msec/echo time [TE] msec), the tumor was better defined 6 minutes after administration of Gd-DTPA. More strongly T1-weighted sequences--that is, SE 200/20 and inversion recovery 1,500/35/400 (TR msec/TE msec/inversion time, msec)--showed significantly worse contrast between tumor and liver (signal-difference-to-noise ratio [SD/N]) 10 and 15 minutes after administration (2 alpha less than or equal to .05). On the other hand, the low SD/N in the rapid MR imaging sequence was significantly improved (2 alpha less than or equal to .05). The most important indications for administration of Gd-DTPA in diagnosing hepatic tumors are the presentation of perfusion conditions and contrast optimization in rapid MR images.     

Focal liver lesions: whether a standard dose (0.05 mmol/kg) gadobenate dimeglumine can provide the same diagnostic data as the 0.1 mmol/kg dose

Objective

Gadobenate dimeglumine (Gd-BOPTA) is a liver-specific contrast agent also showing a distribution in the extracellular compartment which is recommended to be used at standard dose (0.05 mmol/kg) in magnetic resonance imaging (MRI) of liver lesions. However, its use at 0.1 mmol/kg is gradually increasing in recent clinical practice. Which dose should we use in routine MRI of liver lesions from now on? This study investigated the efficacy of Gd-BOPTA at a standard dose versus 0.1 mmol/kg dose in demonstrating diagnostic data in MRI of focal liver lesions.

Materials and methods

The study included 47 patients with focal liver lesions. Twenty-two patients received standard dose and 25 patients received 0.1 mmol/kg dose Gd-BOPTA intravenously. MRI of both groups was carried out with T1-A FLASH-2D and T2-A TURBO spin echo before contrast injection and T1-A FLASH-2D sequences in dynamic and late phase (90th minute) after the contrast injection. The lesion conspicuity for each image was evaluated qualitatively. Liver signal to noise ratio (SNR), absolute lesion-liver contrast to noise ratio (CNR), mean lesion-liver CNR and contrast enhancement rate of the liver obtained from both groups were compared quantitatively.

Results

While liver contrast enhancement rate in the group receiving standard dose Gd-BOPTA were 41% ± 42 in the arterial phase, 66% ± 58 in the portal phase, 45% ± 45 in the venous phase and 42% ± 88 in the late phase, these values were 43% ± 59, 86% ± 73, 63% ± 75 and 61% ± 105, respectively, in the group receiving the dose of 0.1 mmol/kg. There were no statistically significant differences between the means of both groups. While the absolute lesion-liver CNR values were 18 ± 15 precontrast, 22 ± 18 in the arterial phase, 19 ± 17 in the portal phase, 15 ± 10 in the venous phase and 24 ± 26 in the late phase in the group receiving the standard dose Gd-BOPTA, these values were 13 ± 11, 18 ± 15, 15 ± 15, 13 ± 13 and 19 ± 21, respectively, in the group receiving the 0.1 mmol/kg dose. There were no statistically significant differences between the means of both groups (p > 0.05). However, when the mean lesion-liver CNR values were compared, there was statistically significant difference between each arterial and portal phases of metastases in both groups (p < 0.05). There was no statistical difference found in other lesions. When lesion conspicuity scores were compared, there were no significant differences between the two groups.

Conclusion

In liver lesions, similar diagnostic data are obtained in dynamic and late phase MRI with either standard dose Gd-BOPTA or with a dose of 0.1 mmol/kg. Because there was a difference in only metastases in both groups, in oncological patients who are being investigated for liver metastasis, it is expedient to use a dose of 0.1 mmol/kg.     

Evaluation of gadobenate dimeglumine in hepatocellular carcinoma: results from phase II and phase III clinical trials in Japan.

To evaluate the clinical efficacy of gadobenate dimeglumine (Gd-BOPTA)-enhanced magnetic resonance imaging for hepatocellular carcinoma (HCC), we reviewed the results of clinical phase II and III trials in Japan. Gd-BOPTA was administered at a dose of 0.1 mmol/kg to 139 patients who were suspected to have HCC. Dynamic phase images [breath-hold T1-weighted gradient echo (GRE)], spin-echo (SE) images obtained within 10 minutes of injection, and delayed breath-hold GRE images obtained 40-120 minutes after injection were evaluated. All post-contrast images were compared with T1- and T2-weighted pre-contrast images. The contrast efficacy for the dynamic study was classified as ( ) or (++) in 92.1% (128/139), in 43.1% (59/137) with SE within 10 minutes of injection, and in 43.2% (60/139) with breath-hold GRE at delayed phase. The increase in lesion-liver contrast-to-noise ratio was best at the arterial phase of dynamic breath-hold GRE. Liver signal-to-noise ratio showed a mean 52.3% increase in delayed phase. Additional information at delayed phase compared with images acquired within 10 minutes of injection (including the dynamic study) was classified as ( ) or (++) in 28.1% (39/139). With regard to safety, the overall incidence of adverse reactions was 5.0% (7/141) of the patients who were suspected to have HCC, all of whom recovered within 12 hours without any sequelae. No clinically important changes were observed in the blood and urine laboratory tests. It was concluded that Gd-BOPTA was well tolerated and effective in both dynamic study and delayed static imaging for the diagnosis of HCC.     

Evaluation of turbo spin echo sequences for MRI of focal liver lesions at 0.5 T

To determine whether turbo spin echo (TSE) sequences can replace conventional T2-weighted spin echo (SE) sequences in MRI of the liver, 40 patients with focal liver lesions were imaged at 0.5 T. A T2-weighted SE sequences (TR/TE 1800/90 ms, number of signals averaged [NEX]=2, scan time=7:16 min), a TSE sequence (TR/TE 1800/90 ms, NEX=4, number of echos per excitation=13, echo spacing=12.9 ms, scan time=4:16 min) and a T1-weighted SE sequence (TR/TE 350/15 ms, NEX=2, scan time=4:21 min) were obtained and image quality, lesion detectability and lesion differentiation were evaluated qualitatively by subjective assessment using scores and quantitatively by lesion-liver contrast-to-noise (CNR) and tumour/liver signal intensity (SI) ratios. The image quality of the TSE sequence was substantially better compared with the T2-weighted SE sequence due to a reduction in motion artefacts and better delineation of anatomical details. Of a total of 158 visible lesions the T1-weighted SE, TSE, and T2-weighted SE sequences showed 91%, 81% and 65% of the lesions, respectively. Thus the TSE sequence depicted 24% (P< 0.001) more lesions than the T2-weighted SE sequence. In all types of pathology the lesion-liver CNR of the TSE sequence was significantly (P< 0.001) higher compared to the CNR of the T2-weighted SE sequence (+ 55–65%), indicating superior lesion conspicuity. Lesion characterization was equally good on the two T2-weighted sequences with no difference in the tumour/liver SI ratio. Using a criterion of tumour/liver SI ratio equal to or higher than 2, haemangiomas larger than 1 cm in diameter could be differentiated from other lesions with a sensitivity and specificity of 95% and 96%, respectively. Our results indicate that the TSE sequence is suitable for replacing the conventional T2-weighted SE sequence in MRI of focal liver lesions.This paper was presented at ECR 1993 Correspondence to: B. Kreft     

MR imaging of the wrist in rheumatoid arthritis using gadobenate dimeglumine

Objective. To determine the dosage of gadobenate dimeglumine (Gd-BOPTA) necessary for MRI of rheumatoid arthritis of the wrist. Design and patients. Seven wrists inflamed with rheumatoid arthritis were imaged using a dedicated 0.2-T MR unit. Four cumulative dosages of 0.0125, 0.025, 0.05 and 0.1 mmol/kg body weight (BW) Gd-BOPTA were tested. Three-dimensional T1-weighted gradient-recalled echo sequences (GRE; TR: 100 ms, TE: 18 ms, flip angle 90°, 4:55 min) were acquired prior to an intravenous injection and after each additional dosage of Gd-BOPTA. Relative enhancement, signal-difference-to-noise ratios (SDNRs) and the size of the inflamed tissue were quantified. Three radiologists independently evaluated the image quality, the size and the contrast of the enhancing tissue. Results. The readers agreed on a dose of 0.05 mmol/kg BW as satisfactory for the evaluation of the size of the inflammatory tissue and for determination of bone involvement (κ=0.9, P<0.001). Highly inflammatory pannus was depicted with adequate image contrast using 0.025 mmol/kg BW Gd-BOPTA. According to the SDNR and relative enhancement findings, a dose of 0.05 mmol/kg BW suffices for both off-center and centered regions of tissue inflammation (t-test, P<0.05). Conclusion. Gadolinium-BOPTA is an alternative contrast agent for MRI of rheumatoid disease. This study shows that a dose of 0.05 mmol/kg BW suffices at low field strength. Received: 7 June 2000 Revision requested: 22 August 2000 Revision received: 8 September 2000 Accepted: 21 September 2000     

Detection of hepatocellular carcinoma using double-echo FLASH sequence during the hepatic arterial phase.

PURPOSE: The purpose of this study was to compare the performance of in-phase and opposed-phase gradient-recalled echo (GRE) pulse sequences in paramagnetic contrast-enhanced magnetic resonance (MR) imaging of hepatocellular carcinomas (HCCs) during the hepatic arterial phase. MATERIAL AND METHODS: Thirty-four patients with 84 lesions with known or suspected HCCs, nine of whom had a fatty liver, were examined with double-echo GRE techniques under 1.5T before and 30 s after injection of gadopentenate dimeglumine at a dose of 0.1 mmol/kg. Echo times were 2.4 ms (opposed phase) and 5.0 ms (in phase). Contrast enhancement of the HCC detected in both in-phase and opposed-phase images was evaluated. The liver signal-to-noise ratio (SNR), lesion-liver contrast-to-noise ratio (CNR), and enhancement ratio (ER) were calculated for the largest lesion of each patient. RESULTS: In dynamic gadolinium-enhanced images of the 84 HCCs, 81 (96.4%) were detected in both in-phase and opposed-phase images, two (2.4%) were detected in only in-phase images, and one (1.2%) was detected only in opposed-phase images. The liver SNR, CNR, and ER were 46.7+/-16.1, 15.2+/-10.3, and 0.637+/-0.268 for in-phase images, and 48.9+/-16.9, 16.3+/-11.8, and 0.647+/-0.309 for opposed-phase images, respectively. In patients with a fatty liver, the SNR, CNR, and ER were 46.0+/-18.1, 21.7+/-17.9, and 0.525+/-0.231 for in-phase images, and 44.3+/-18.7, 26.0+/-21.3, and 0.793+/-0.124 for opposed-phase images, respectively. No significant statistical differences were found between the in-phase and opposed-phase images. CONCLUSION: Opposed-phase GRE imaging is equivalent to in-phase GRE sequences in patients with or without fatty liver for detection of HCC in dynamic gadolinium-enhanced images.     

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.     

A comparison of Gd-BOPTA and Gd-DOTA for contrast-enhanced MRI of intracranial tumours

A two-centre intra-individual crossover study was performed in 23 patients with suspected high-grade glioma or metastases to assess and compare the safety and enhancement characteristics of two different MRI contrast media (gadobenate dimeglumine, Gd-BOPTA and gadoterate meglumine, Gd-DOTA) at equivalent doses of 0.1 mmol/kg body weight. T1-weighted spin-echo (SE) and T2-weighted fast SE images were obtained before and T1-weighted images 0, 2, 4, 6, 8 and 15 min after injection. T1-weighted images with magnetisation transfer contrast were acquired 12 min after injection. Qualitative assessment by blinded, off-site readers (reader 1: 19 patients; reader 2: 21) and on-site investigators (23) revealed significant (P 0.005) overall preference for Gd-BOPTA over Gd-DOTA for contrast enhancement (Gd-BOPTA preferred in 18, 15 and 18 cases; Gd-DOTA in 0, 1 and 1 and no preference in 1, 5 and 4; off-site readers 1 and 2, and on-site investigators, respectively). A similar significant preference for Gd-BOPTA was expressed by off-site readers and on-site investigators for lesion-to-brain contrast, lesion delineation, internal lesion structure, and overall image preference. Quantitative assessment by off-site readers revealed significantly (p<0.05) greater lesion enhancement with Gd-BOPTA than with Gd-DOTA at all times from 2 min after injection.     

Gadobenate dimeglumine (BOPTA) enhanced MR imaging: Patterns of enhancement in normal liver and cirrhosis

To determine whether gadobenate dimeglumine (BOPTA) will adequately enhance cirrhotic liver parenchyma, and to document the enhancement patterns in cirrhosis, 14 cirrhotic and 20 non-cirrhotic patients were evaluated before and 60–120 minutes after gadolinium-BOPTA. Proof of liver cirrhosis was biopsy (6), surgical resection (3), and clinical follow-up (5). Enhancement effects were compared quantitatively by determining the liver signal-to-noise ratio (SNR) and signal enhancement in both populations. Qualitatively assessment of the liver enhancement was performed and classified as homogeneous or heterogeneous. Quantitative analysis: cirrhotic liver parenchyma presented a higher increase in SNR values, relative to noncirrhotic liver parenchyma, on postcontrast images. Likewise the signal enhancement of cirrhotic liver parenchyma was superior to non-cirrhotic liver on T1-weighted SE images (P = .02) and in-phase GRE images (P < .001). There was no statistical difference on out-of-phase GRE images. Qualitative analysis: on T1-weighted SE postcontrast images, cirrhotic liver parenchyma showed a homogeneous enhancement in 7 patients and heterogeneous in 7. Whereas on GRE images, cirrhotic parenchyma showed heterogeneous enhancement in 9 patients and homogeneous in 5 patients. The heterogeneous enhancement was due to the presence of hypointense nodules in 7 patients and hyperintense nodules in 2 patients. In conclusion, our study has shown that the hepatobiliary contrast agent Gd-BOPTA is effective in the cirrhotic liver, demonstrating an increased liver enhancement compared with non-cirrhotic patients.     

Short TI inversion-recovery imaging of the liver: pulse-sequence optimization and comparison with spin-echo imaging

Magnitude-reconstructed short inversion-time (TI) inversion-recovery (IR) sequences have the advantage of reducing the signal of fat while providing additive T1 and T2 contrast. A double-echo short TI IR sequence was implemented to offer different degrees of T1- and T2-dependent image contrast. In 50 consecutive patients with proved liver tumors (30 metastases, 13 hemangiomas, seven other primary liver tumors), images obtained with a double-echo IR sequence at a repetition time (TR) of 1,500 msec, echo time (TE) of 30 and 60 msec, and TI of 80 msec (TR/TE/TI = 1,500/30, 60/80) were compared with those obtained with spin-echo (SE) sequences at a TR of 275 msec and a TE of 14 msec (TR/TE = 275/14) and 2,350/60, 120, 180. Metastases-liver contrast-to-noise ratios were highest at SE 275/14, followed by IR 1,500/30/80 and SE 2,350/180. IR 1,500/30/80 and SE 275/14 sequences consistently showed higher sensitivity for the detection of metastases than T2-weighted SE sequences. Differential diagnosis of benign and malignant lesions was more reliable with T2-weighted SE sequences than T2-weighted short TI IR sequences.     

Fast MR imaging of liver metastasis using FLASH and FISP--optimal sequences for T1- and T2*-weighted images

This paper deals with a study to obtain the optimal sequence of gradient echo (GE) for T1- and T2*-weighted images similar to T1- and T2-weighted images of spin echo (SE). Two GE sequences, fast low angle shot (FLASH) and fast imaging with steady-state precession (FISP), were performed in 15 cases of liver metastasis in various combination of flip angle (FA), repetition time (TR), and echo time (TE). The optimal combinations were summarized as follows: 1) T1-weighted FLASH image with FA of 40 degrees, TR of 22 msec and TE of 10 msec, 2) T1-weighted FISP image with FA of 70 degrees, TR of 100 msec, TE of 10 msec, 3) both T2*-weighted FLASH and FISP images with FA of 10 degrees, TR of 100 msec and TE of 30 msec. Not only to provide the adequate T1- and T2*-weighted images but also to enable breath-holding MR imaging, GE sequences can optionally take place SE in cases of deteriorated images caused by moving artifacts. Other applications support the re-examination and further detailing when required, conveniently rather in short time.     

Gadobenate dimeglumine-enhanced liver MR imaging: value of dynamic and delayed imaging for the characterization and detection of focal liver lesions

The aim of this study was to determine the value of delayed-phase imaging (DPI) of gadobenate dimeglumine (Gd-BOPTA)-enhanced MR imaging for the evaluation of focal hepatic tumors compared with precontrast imaging and early dynamic phase imaging. The MR images were obtained in 48 patients with 98 focal hepatic tumors. Three-dimensional gradient-echo (GRE) imaging obtained before and 30, 60, and 1 h after administration of 0.1 mmol/kg of gadobenate dimeglumine. Each image set was analyzed qualitatively (lesion detection, conspicuity, delineation, and enhancement pattern on DPI) and quantitatively [signal-to-noise ratio (SNR), tumor–liver contrast-to-noise ratio (CNR)]. Improved lesion-to-liver contrast during the dynamic phase imaging was observed compared with precontrast images. The DPI showed a homogeneous enhancement of liver parenchyma and distinctive enhancement features of focal liver lesions: metastases (85%) showed a target shaped enhancement, and hepatocellular carcinomas (HCCs) showed an inhomogeneous (58%) or homogeneous enhancement (21%). The DPI showed better performance for the detection of metastases than other images by increasing lesion delineation (p<0.05). The absolute CNR of metastasis measured from periphery of the tumors on DPI was greater than precontrast and arterial phase imaging (p<0.05). The Gd-BOPTA during both dynamic and delayed phases provides valuable information for the characterization of focal liver lesions, and furthermore, Gd-BOPTA-enhanced DPI contributed to the improved detection of liver metastasis compared to precontrast and early dynamic imaging.     

Time-resolved contrast-enhanced three-dimensional pulmonary MR-angiography: 1.0 M gadobutrol vs. 0.5 M gadopentetate dimeglumine

PURPOSE: To compare contrast characteristics and image quality of 1.0 M gadobutrol with 0.5 M Gd-DTPA for time-resolved three-dimensional pulmonary magnetic resonance angiography (MRA). MATERIALS AND METHODS: Thirty-one patients and five healthy volunteers were examined with a contrast-enhanced time-resolved pulmonary MRA protocol (fast low-angle shot [FLASH] three-dimensional, TR/TE = 2.2/1.0 msec, flip angle: 25 degrees, scan time per three-dimensional data set = 5.6 seconds). Patients were randomized to receive either 0.1 mmol/kg body weight (bw) or 0.2 mmol/kg bw gadobutrol, or 0.2 mmol/kg bw Gd-DTPA. Volunteers were examined three times, twice with 0.2 mmol/kg bw gadobutrol using two different flip angles and once with 0.2 mmol/kg bw Gd-DTPA. All contrast injections were performed at a rate of 5 mL/second. Image analysis included signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) measurements in lung arteries and veins, as well as a subjective analysis of image quality. RESULTS: In patients, significantly higher SNR and CNR were observed with Gd-DTPA compared to both doses of gadobutrol (SNR: 35-42 vs.17-25; CNR 33-39 vs. 16-23; P < or = 0.05). No relevant differences were observed between 0.1 mmol/kg bw and 0.2 mmol/kg bw gadobutrol. In volunteers, gadobutrol and Gd-DTPA achieved similar SNR and CNR. A significantly higher SNR and CNR was observed for gadobutrol-enhanced MRA with an increased flip angle of 40 degrees. Image quality was rated equal for both contrast agents. CONCLUSION: No relevant advantages of 1.0 M gadobutrol over 0.5 M Gd-DTPA were observed for time-resolved pulmonary MRA in this study. Potential explanations are T2/T2*-effects caused by the high intravascular concentration when using high injection rates.     

Detection of hepatic metastases: analysis of pulse sequence performance in MR imaging

Forty-three patients with liver metastases were imaged using 14 different pulse sequences (average, 7.5 sequences per patient) to allow direct comparison of their performance. "T2-weighted" spin-echo (SE) images, "T1-weighted" inversion recovery (IR) images, and "T1-weighted" SE images were obtained using a wide range of timing parameters. Pulse sequence performance was quantitated by measuring liver signal-to-noise (S/N) ratios and cancer-liver signal difference-to-noise (SD/N) ratios. Data were standardized to reflect a constant imaging time of 9 minutes for all pulse sequences. The SE 2,000/120 (TR [repetition time]/TE [echo time]) sequence resulted in the greatest SD/N ratio of the T2-weighted SE sequences but also yielded the low S/N ratios, poor anatomic resolution, and motion artifacts common to all T2-weighted SE images. IR sequence images were also sensitive to motion artifacts because of the use of a long TR (1,500 msec). Short TR/TE T1-weighted SE sequences (SE 260/18) had the greatest SD/N ratio (P less than .05), S/N ratio, and anatomic resolution. Furthermore, extensive signal averaging appears to be a powerful solution to all types of motion artifacts in the abdomen.     

Gadolinium-DOTA enhanced fast imaging of liver tumors at 1.5 T

Twenty patients [15 men, 5 women, 19-71 years old (mean 52 years)] highly suspected of having tumoral liver pathology were prospectively studied with motion compensated T2-weighted spin echo (SE) [repetition time (TR) 2,200 ms, echo time (TE) 90 ms] and Gd-DOTA enhanced gradient echo fast low angle shot [TR 60 ms, TE 10 ms, angle 30 degrees) sequences. The final diagnoses were hemangioma (five), hepatocellular carcinoma (four), focal nodular hyperplasia (one), adenoma (one), metastasis (two), abscess (two), echinococcal cyst (one), tumor of unknown origin (three), cirrhosis (one). Contrast enhanced images were obtained during the early vascular phases after intravenous bolus injection of Gd-DOTA at a dose of 0.1 mmol/kg (0.2 ml/kg). After Gd-DOTA, positive contrast enhancement was seen in 11 cases, negative enhancement in 4, and nonenhancement in 6. Contrast patterns were similar to contrast enhanced CT. In terms of visibility of lesions, the unenhanced motion-compensated T2 SE sequences were superior to the nonenhanced gradient echo sequences in 12 patients and equal in 8. After gadolinium enhancement, T2-weighted SE images were superior to the postcontrast gradient echo images in eight cases, equal in eight and inferior in four cases.