Low-dose gadobenate dimeglumine versus standard dose gadopentetate dimeglumine for contrast-enhanced magnetic resonance imaging of the liver: an intra-individual crossover comparison

RATIONALE AND OBJECTIVES: Gadobenate dimeglumine (Gd-BOPTA) has a two-fold higher T1 relaxivity compared with gadopentetate dimeglumine (Gd-DTPA) and can be used for both dynamic and delayed liver MRI. This intraindividual, crossover study was conducted to compare 0.05 mmol/kg Gd-BOPTA with 0.1 mmol/kg Gd-DTPA for liver MRI. MATERIALS AND METHODS: Forty-one patients underwent two identical MR examinations separated by >or= 72 hours. Precontrast T1-FLASH-2D and T2-TSE sequences and postcontrast T1-FLASH-2D sequences were acquired during the dynamic and delayed (1-2 hours) phases after each contrast injection. Images were evaluated on-site by two independent, blinded off-site readers in terms of confidence for lesion detection, lesion number, character and diagnosis, enhancement pattern, lesion-to-liver contrast, and benefit of dynamic and delayed scans. Additional on-site evaluation was performed of the overall diagnostic value of each agent. RESULTS: Superior diagnostic confidence was noted by on-site investigators and off-site assessors 1 and 2 for 6, 4 and 2 patients with Gd-BOPTA, and for 3, 1 and 2 patients with Gd-DTPA, respectively. No consistent differences were noted for other parameters on dynamic phase images whereas greater lesion-to-liver contrast was noted for more patients on delayed images after Gd-BOPTA. More correct diagnoses of histologically confirmed lesions (n = 26) were made with the complete Gd-BOPTA image set than with the complete Gd-DTPA set (reader 1: 68% vs. 59%; reader 2: 78% vs. 68%). The overall diagnostic value was considered superior after Gd-BOPTA in seven patients and after Gd-DTPA in one patient. CONCLUSION: The additional diagnostic information on delayed imaging, combined with the possibility to use a lower overall dose to obtain similar diagnostic information on dynamic imaging, offers a distinct clinical advantage for Gd-BOPTA for liver MRI.     

High-dose Gd-DTPA vs. Bis-Gd-mesoporphyrin for monitoring laser-induced tissue necrosis

PURPOSE: To compare Bis-Gd-mesoporphyrin (Bis-Gd-MP), a contrast agent with a reported high affinity to necrotic tissue, with high-dose gadopentate dimeglumin (Gd-DTPA) for defining laser-induced muscle and liver necrosis by contrast-enhanced (CE) MRI. MATERIALS AND METHODS: Laser-induced interstitial thermotherapy (LITT) was performed in the muscle and liver tissue of New Zealand White rabbits (1500 J and 2100 J; n=80 lesions). The animals were randomly assigned to a group that received 0.3 mmol/kg bw Gd-DTPA or a group that received 0.05 mmol/kg bw Bis-Gd-MP. Following contrast injection, dynamic MRI was performed on muscle lesions with a T1-weighted, two-dimensional, fast low-angle shot (FLASH) sequence. The liver and muscle lesions were then repeatedly imaged for six hours after contrast injection using a T1-weighted spin-echo (SE) sequence. Central and peripheral lesion enhancement was determined and correlated with gross pathology and microscopy findings. RESULTS: Both contrast agents allowed precise determination of lesion diameters with an average accuracy of 6.8%+/-1.3%. Rim enhancement during dynamic MRI was superior for Gd-DTPA (P<0.001) and revealed slightly higher lesion diameters compared to the results of follow-up MR studies. A persistent enhancement of necrotic liver and muscle tissue was observed for both contrast agents throughout the observation period, suggesting that simple diffusion-type processes may underlie the supposed affinity of Bis-Gd-MP for tissue necrosis. CONCLUSION: Bis-Gd-MP and Gd-DTPA are equally well suited for postinterventional lesion assessment in LITT.     

Comparison of gadobenate dimeglumine with gadopentetate dimeglumine for magnetic resonance imaging of liver tumors

RATIONALE AND OBJECTIVES: To compare gadobenate dimeglumine (Gd-BOPTA) with gadopentetate dimeglumine (Gd-DTPA) for magnetic resonance imaging of the liver. METHODS: The contrast agent Gd-BOPTA or Gd-DTPA was administered at a dose of 0.1 mmol/kg to 257 patients suspected of having malignant liver tumors. Dynamic phase images, spin-echo images obtained within 10 minutes of injection, and delayed images obtained 40 to 120 minutes after injection were acquired. All postcontrast images were compared with unenhanced T1-weighted and T2-weighted images obtained immediately before injection. A full safety assessment was performed. RESULTS: The contrast efficacy for dynamic phase imaging was moderately or markedly improved in 90.9% (110/121) and 87.9% (109/124) of patients for Gd-BOPTA and Gd-DTPA, respectively. At 40 to 120 minutes after injection, the cor- responding improvements were 21.7% (26/120) and 11.6% (14/121) for spin-echo sequences and 44.5% (53/119) and 19.0% (23/121) for breath-hold gradient-echo sequences, respectively. The differences at 40 to 120 minutes after injection were statistically significant (P < 0.02). Increased information at 40 to 120 minutes after injection compared with information acquired within 10 minutes of injection was available for 24.0% (29/121) of patients with Gd-BOPTA and for 14.5% (18/124) of patients with Gd-DTPA (P < 0.03). Adverse events were seen in 4.7% (6/128) and 1.6% (2/127) of patients receiving Gd-BOPTA and Gd-DTPA, respectively. The difference was not statistically significant. CONCLUSIONS: The efficacy of Gd-BOPTA is equivalent to that of Gd-DTPA for liver imaging during the dynamic phase and superior during the delayed (40-120 minutes) phase of contrast enhancement. Both agents are safe for use in magnetic resonance imaging of the liver.     

Dynamic MR imaging of the liver with Gd-DTPA: initial clinical results

Gd-DTPA was evaluated as a hepatic contrast agent for MR imaging. Twenty-six consecutive patients referred for suspected masses in the liver were studied at 1.5 T. Fourteen patients had hepatic metastases and one patient each had cholangiocarcinoma and multicentric hepatocellular carcinoma. Four patients had cavernous hemangiomas and the remainder had other benign lesions. Diagnoses were proved by biopsy, sonography, or radionuclide scintigraphy in 23 cases and by autopsy in one case. Precontrast scans were obtained by using standard pulse sequences. In addition, breath-hold scans were obtained before and after bolus administration of 0.1 mmol/kg Gd-DTPA by using a multislice T1-weighted gradient-echo pulse sequence with an ultrashort echo time. Mean lesion-liver signal difference/noise increased by 50% (p less than .01) in the immediate postcontrast phase. In two of 26 cases, multiple additional lesions as small as 3 mm were detected after contrast administration that were not seen before contrast administration. In no case was lesion-liver contrast worsened on scans obtained immediately after administration of contrast material. However, on delayed scans, detection of lesions worsened in some cases because of equilibration of contrast material between liver and lesion. These initial clinical results suggest that enhancement with Gd-DTPA is a practical method for improving lesion-liver contrast and has the potential to improve the accuracy of MR imaging in the liver. However, optimized fast imaging techniques are required for best results.     

常规SE序列和动态增强MRI诊断肝局灶性病变的比较

目的比较常规SE序列与动态Gd-U．----x增强扫描对肝局灶病变的诊断价值。方法对34例肝局灶病变做了常规SE平扫和动态Gd-U．---A增强及延迟万WI增强扫描；就各序列对肝局灶病变的检出率、病变的信噪比（C／N）值和图像质展进行定员和定性分析。结果36例共142个病灶，动态Gd-lyl？l？A检出率（138／142，958％）明st高于IFZWI和延迟TW［增强（128／14，叨％；119／142，838％）（P＜005）：动态Gd-IJ：1713A增强的C／N值高于TZWI和TIWI延迟增强（P＜0．05）；动态增强的伪影较L们少（P＜0．01），而病灶清晰度各序列之间无明显差别（P＞0．历）。结论动态u-ly：1717A增强扫描在病灶检出率、图像质显反C／N值方面均优于IWI，对肝局灶病变的诊断是一种有价值的方法，     

Prediction of subtle thermal histopathological change using a novel analysis of Gd-DTPA kinetics

PURPOSE: To investigate Gd-DTPA kinetics as predictors of histopathological changes following focused ultrasound (FUS) thermal ablation for improved planning and assessment. MATERIALS AND METHODS: Twenty-nine FUS lesions were created in the thigh muscle of eight rabbits under MR-guidance at 1.5 Tesla. Three rabbits were killed at four hours; and 11 lesions were analyzed with histopathology. Temperature-sensitive MRI using proton-resonant frequency-shift was used for time-dependent temperature measurements. Analysis of the uptake kinetics of Gd-DTPA was performed after Gd-DTPA injection, within 20 minutes after heating and again at two hours after heating. The resulting kinetic maps, permeability (K(trans)) and leakage space (v(e)), were correlated to peak temperatures, T(2)-weighted MR, and histopathology. RESULTS: Images of K(trans) and v(e) reveal regions of histopathological change not visible on conventional post-therapy MR. At early times after heating, v(e) predicts the area of injury more accurately than T(2) (7 +/- 2% vs. 25 +/- 6% underestimation). A circular region of extensive structural/vascular disruption is indicated only on K(trans) maps. The sharp decrease in K(trans) at the boundary of this region occurs at 47.5 +/- 0.5 degrees C, and may be a better estimate of cell death than the conventional method of temperature threshold (55 degrees C for coagulation) used in therapy planning. CONCLUSION: Our results suggest Gd-DTPA kinetics can predict different histopathological changes following FUS ablation and may be valuable for early prediction.     

Hepatic excretion of urographic contrast medium: use in delineating intrahepatic cholangiocarcinoma on scans delayed for 2 hours

Vicarious excretion of urographic contrast media by the liver has been detected by conventional radiographic methods in patients with renal impairment or unilateral obstruction. It occurs in patients with normal renal function, however, and can be detected by delayed postcontrast computed tomography scans. A case is presented in which an intrahepatic cholangiocarcinoma was best depicted on scans delayed for 2 hours. After 2 hours, the contrast medium remained within hepatic parenchyma but was virtually cleared from the vascular and interstitial spaces.     

Superparamagnetic iron oxide-enhanced MRI of atherosclerotic plaques in Watanabe hereditable hyperlipidemic rabbits

RATIONALE AND OBJECTIVES: Inflammatory atherosclerotic plaques are characterized by increased endothelial permeability and multiple macrophages. Blood-pool MRI contrast agents like superparamagnetic iron oxide (SPIO) have an affinity for the monocyte-macrophage system and thus, may label inflammatory plaques. The objective was to demonstrate SPIO uptake in plaques of atherosclerotic rabbits by MRI and histology. METHODS: Aortas of anesthetized Watanabe hereditable hyperlipidemic rabbits were studied with a moderately T2*-weighted gradient-echo sequence at 1.5 T. Four groups of five animals each were studied: (1) without ultrasmall SPIO (carboxydextran coating; particle size, 25 nm; estimated plasma half-life, 6 hours) or with imaging after intravenous injection of SPIO at a dose (micromol Fe/kg) and postcontrast time delay (hours) of 50/8 (2), 50/24 (3), or 200/48 (4). In vivo MRI was compared with corresponding ex vivo histological iron stains. RESULTS: Animals receiving 200 micromol Fe/kg demonstrated areas of focal signal loss clearly confined to the aortic wall on a mean of 24 +/- 9 (31% +/- 11%) of 76 +/- 5 images compared with 0 +/- 0 of 76 +/- 5 images in controls (P = 0.009). The number of images with this finding in groups 2 and 3 was not significantly different compared with controls. By microscopy, SPIO-iron was seen in the endothelial cells and subendothelial intimal macrophages of atherosclerosis-prone aortic wall segments. Atherosclerotic lesions demonstrating iron uptake also showed a high macrophage content. CONCLUSIONS: SPIO accumulates in aortic plaques of atherosclerotic rabbits, producing a characteristic MRI finding. As SPIO accumulates in plaques with increased endothelial permeability and a high macrophage content, two established features of plaque inflammation, it may have a potential for noninvasive assessment of inflammatory atherosclerotic plaques.     

Capillarization of the sinusoids in liver fibrosis: noninvasive assessment with contrast-enhanced MRI in the rabbit.

Sinusoidal capillarization induces microcirculatory changes in liver cirrhosis and fibrosis. The purpose of this study was to assess whether contrast-enhanced MRI can be used to demonstrate the effects of sinusoidal capillarization in liver fibrosis. Dynamic MRI after injection of a low-molecular-weight contrast agent of 0.56 kDa (Gd-DOTA), and two high-molecular-weight contrast agents of 6.47 kDa and 52 kDa (P792 and P717) was performed in rabbits with liver fibrosis induced by cholesterol and diethylstilbestrol. The hepatic distribution volume accessible to the high-molecular-weight agents decreased in the rabbits with liver fibrosis (P792: 7.8% +/- 1.7% vs. 10.1% +/- 1.8% in normal rabbits, P =.038; P717: 6.2% +/- 2.1% vs. 9.7% +/- 1.6% in normal rabbits, P =.007), whereas the hepatic mean transit time (MTT) of the low-molecular-weight agent was increased (15.9 +/- 8.0 s vs. 8.8 +/- 2.6 s in normal rabbits, P =.015). In rabbits with liver fibrosis, the clearance of indocyanine green (ICG) was correlated with the volume accessible to the high-molecular-weight agents (P792: r = 0.810, P =.015; P717: r = 0.857, P =.007). The collagen content of the liver was inversely correlated with the distribution volume of P717 (r = -.833, P =.010) and with the ICG clearance (r = -.810, P =.015). It was concluded that the microcirculatory changes induced by sinusoidal capillarization in liver fibrosis can be demonstrated noninvasively with MRI.     

Comparison of Gd-BOPTA with Gd-DTPA in MR imaging of rat liver

A new lipophilic compound, gadolinium benzyloxypropionictetraacetate (BOPTA), with a high rate of biliary excretion was assessed as a magnetic resonance (MR) hepatospecific contrast-enhancing agent and compared with Gd-DTPA (diethylenetriaminepentaacetic acid) in MR imaging of normal rats. T1-weighted spin-echo images obtained before and after administration of each contrast agent at doses of 0.25, 0.5, and 1.0 mmol/kg showed greater enhancement of the liver with Gd-BOPTA than with Gd-DTPA, with the advantage more evident at lower doses. Images obtained with an inversion recovery sequence at the null value of rat liver parenchyma after injection of 0.1- and 0.5-mmol/kg doses of the contrast agent provided better evidence of the greater and longer-lasting hepatic enhancement due to Gd-BOPTA when compared with that of Gd-DTPA. Gd-BOPTA is a potentially good contrast agent for obtaining prolonged enhancement of the liver, permitting studies during the long time needed to acquire conventional T1-weighted images.     

Coronary magnetic resonance angiography: experimental evaluation of the new rapid clearance blood pool contrast medium P792.

The signal-enhancing characteristics of a new monodisperse monogadolinated macromolecular MR contrast medium (P792) were evaluated for magnetic resonance angiography (MRA) of the coronary arteries. A total of 15 cardiac examinations were performed in pigs at 1.5 T using a 3D gradient-echo sequence. Images were acquired during breath-hold before and up to 35 min after IV injection of Gd-DTPA (0.3 mmol Gd/kg), Gd-BOPTA (0.2 mmol Gd/kg), and P792 (13 micromol Gd/kg). An increase in the signal-to-noise ratio (SNR) of 97% +/- 17%, 108% +/- 37%, and 109% +/- 31% in coronary arteries and of 82% +/- 19%, 82% +/- 24%, and 28% +/- 18% in myocardium, respectively, was measured during the first postcontrast acquisition. The blood-to-myocardium signal-difference-to-noise ratio (SDNR) was significantly higher for P792 than for the other Gd compounds (P <.05) for up to 15 min after injection. Qualitative assessment showed that visualization of the coronary arteries and their branches was significantly better for P792 compared to the low-molecular Gd compounds (P <.05). The blood pool contrast medium P792 is well suited for MRA of the coronary arteries.     

Renal tolerance of gadolinium-DTPA/dimeglumine in patients with chronic renal failure.

Safety data for renal tolerance of gadolinium-DTPA(Gd-DTPA)/dimeglumine were evaluated in 21 patients (age: mean +/- standard deviation [SD], 58 +/- 12 years) with impaired renal function. The mean +/- SD serum creatinine level at baseline was 213 +/- 101 mumol/L (range, 89.2-551 mumol/L). Creatinine clearance at baseline averaged 34.5 +/- 19.2 mL/minute (range, 7.2-70 mL/minute). Gd-DTPA was injected at a dose of 0.1 mmol/kg body weight. Serum parameters (creatinine, sodium, and potassium) were determined before and 6, 24, 48, and 120 hours after administration of Gd-DTPA. Urinary parameters (N-acetyl-beta-D-glucosaminidase [beta-NAG], protein, and albumin) were determined before (spot urine sample) and after treatment for collection periods 0 to 3, 3 to 6, 6 to 12, 12 to 24, and 24 to 48 hours. A final spot urine sample was taken at 120 hours. There was no significant statistical change of serum creatinine level within the observation period, and there was no single patient matching the criteria of acute renal failure (increase of serum creatinine level of 88.4 mumol/L [1 mg/dL] or more within 48 hours after injection). Serum values of sodium and potassium levels remained unchanged. Beta-NAG was slightly increased 0 to 3 hours after injection, but returned to baseline values during the collection periods up to 120 hours. There was no increase of protein or albumin excretion. These preliminary results suggest Gd-DTPA has good renal tolerance in patients with pre-existing chronic renal failure.     

Biodistribution and clearance of liposomal gadolinium-DTPA

Gadolinium-DTPA (Gd-DTPA) liposomes have been studied previously as liver contrast agents and have been shown to improve the detection of hepatic metastases in rats. We synthesized 100-nm and 50-nm liposomes that encapsulated Gd-DTPA and did biodistribution and clearance studies in rats. Parallel magnetic resonance imaging (MRI) studies were also done. Biodistribution showed a prolonged blood pool phase for Gd-DTPA liposomes with a blood pool half-life of approximately 4 hours for the 100-nm liposomes. The highest uptake per gram of tissue was achieved by the spleen. Clearance of gadolinium from the liver and spleen showed a half-life of 3 to 4 days. The smaller 50-nm Gd-DTPA liposomes resulted in a longer blood pool phase and a higher delivery of gadolinium to the liver, bone marrow, and spleen. Imaging studies after intravenous (IV) administration of liposomal Gd-DTPA showed organ enhancement that paralleled the data on biodistribution studies, with appreciable hepatic enhancement at doses as low as 0.025 mm/kg of liposomal Gd-DTPA.     

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.     

经动脉磁共振门静脉成像的实验研究

目的在犬模型上评价不同的造影动脉、对比剂剂量及血管扩张剂应用与否对经动脉磁共振门静脉成像(MR imaging during arterial portography,MRAP)图像的影响,总结出MRAP的最佳技术参数,为下一步的临床应用做准备.方法健康成犬16条,通过随机化分组表法分配到造影动脉、对比剂剂量及有无血管扩张剂3个研究组中.每条犬行腹腔麻醉后,在X线监视下经股动脉穿刺插管至肠系膜上动脉或脾动脉,行MRAP检查.计算增强前后肝实质信号强度的相对增强值,比较各因素不同水平间的相对增强值之间差异有无统计学意义.分析时间-增强曲线,总结MRAP的最佳技术参数.结果在16条犬上均获得了较为理想的MRAP图像.肠系膜上动脉组肝实质相对增强峰值为29.3%～106.0%,脾动脉组为29.5%～105.0%,肠系膜上动脉组达到肝实质相对增强峰值的时间为24～27 s,而脾动脉组为24～28 s,两组间差异无显著性意义(F=0.03,P>0.05).0.025 mmol/kg组的相对增强峰值为29.3%～30.9%,与0.050 mmol/kg组的95.5%～98.8%,0.100 mmol/kg组的102.0%～106.0%和0.200 mmol/kg组的104.0%～105.0%比较,除后两组之间差异无显著性意义(P>0.05)外,其他各组间差异均有非常显著性意义(P<0.01).有血管扩张剂组达到肝实质相对增强峰值的时间为21～27 s,早于无血管扩张剂组的24～28 s(P<0.05),但两组肝实质相对增强峰值差异无显著性意义(P>0.05).结论 (1)MRAP是一项新的安全可行的肝脏影像学检查技术,20 ml 钆喷替酸葡甲胺(Gd-DTPA)混合液(0.050～0.100 mmol/kg)以1 ml/s注射速度经造影动脉注入,在注射开始后21～28 s即可获得实验动物肝实质的最佳门静脉增强MRAP图像.(2)肠系膜上动脉或脾动脉作为造影动脉,在MRAP影像和时间-增强曲线上无差别.(3)0.050～0.100 mmol/kg的Gd-DTPA剂量完全可以引起肝实质足够的增强(95.5%～106.0%).(4)血管扩张剂的应用并不影响MRAP图像肝实质增强峰值达到的时间和峰值的大小.     

A feasibility study of contrast enhancement of acute myocardial infarction in multislice computed tomography: comparison with magnetic resonance imaging and gross morphology in pigs

INTRODUCTION: Late enhancement magnetic resonance imaging (MRI) of myocardial infarction (MI) is clinically established. There are no reports on MI assessment using state-of-the-art multislice CT technology. For this reason, animal experiments were conducted to examine the applicability of contrast-enhanced ECG-gated multislice computed tomography (MSCT) for the detection of acute MI. The results were correlated with MRI and postmortem tissue staining. MATERIAL AND METHODS: Acute MI was induced in 14 pigs by balloon occlusion of the LAD. In 8 animals, the LAD was reperfused after 45 minutes. In 6 animals, the LAD was permanently blocked. MR imaging was performed 15 minutes after the administration of 0.2 mmol Gd-DTPA/kg/bodyweight. Subsequently, 16-slice MSCT was performed at various timepoints after injecting 120 mL of iodinated contrast medium. 2,3,5-Triphenyltetrazolin-chloride (TTC) staining was acquired for all hearts investigated. Correlation analysis was applied to compare the area of MI derived from MRI, MSCT, and TTC. The reperfused infarcts were compared with the nonreperfused infarcts using an unpaired t test. RESULTS:: Mean infarct area as measured by TTC staining was 18.3% +/- 7.8% of the left ventricular area. Good correlation of the spatial extent of the infarcted area was found for TTC and MRI as well as for TTC and MSCT data obtained 5 minutes postcontrast injection. MSCT imaging demonstrated a significant difference in density (P < 0.001) between nonreperfused (47.0 +/- 6.6 HU) and reperfused (116.4 +/- 19.8 HU) infarction. CONCLUSION: In our pilot study, contrast-enhanced MSCT was feasible to assess myocardial viability in pigs. MSCT also affords differentiation of nonreperfused and reperfused acute MI. MI sizes derived from MSCT imaging correlate well to those obtained with MRI and TTC.     

New generation of monomer-stabilized very small superparamagnetic iron oxide particles (VSOP) as contrast medium for MR angiography: preclinical results in rats and rabbits

The purpose of this study was to evaluate the signal enhancement characteristics of very small superparamagnetic iron oxide particles (VSOP)-C63, a new monomer-coated, iron oxide-based magnetic resonance (MR) blood pool contrast medium with a very small particle size and optimized physical properties. Equilibrium MR angiography (MRA) of rats (thoracic and abdominal vessels) was performed at 1.5 T with a three-dimensional gradient-recalled echo (3D GRE) technique (TR/TE 6.6/2.3 msec, flip angle 25 degrees ) before and after (every 3-5 minutes up to 50 minutes) i.v. injection of VSOP-C63 [dosages: 15, 30, 45, 60, 75, and 90 micromol Fe/kg; diameter: 8 nm; relaxivities at 0.47 T: R1 = 30 l/(mmol * s); R2 = 39 l/(mmol * s)]. First-pass MRA images (3D-GRE, TR/TE 4.5/1.7 msec, flip angle 25 degrees ) were obtained with 45 micromol Fe/kg VSOP-C63 in comparison with 0.2 mmol Gd/kg of gadolinium diethylene triamine pentaacetic acid (Gd DTPA; before and every 5 seconds p.i.). MRA (3D GRE, TR/TE 4.5/1.7 msec, flip angle 25 degrees) of coronary vessels in rabbits was performed after i.v. injection of 45 micromol Fe/kg of VSOP-C63. In rats maximal S/N ratio in thoracic and abdominal arteries directly after i.v. injection of VSOP-C63 was 25 +/- 1, 43 +/- 2, 49 +/- 4, 57 +/- 3, 64 +/- 3, and 63 +/- 3 for the different dosages. Blood half-life was dose dependent (15 +/- 2, 20 +/- 3, 29 +/- 6, 37 +/- 5, 61 +/- 16, and 86 +/- 21 minutes). At a dose of 30 micromol Fe/kg even small intrarenal arteries were sharply delineated. First-pass MRA showed no significant difference in the S/N ratio between Gd-DTPA (71.5 +/- 11.5) and VSOP-C63 (65.1 +/- 18. 3). The proximal segments of the coronary arteries in rabbits were clearly depicted at a dose of 45 micromol Fe/kg. The monomer-coated, iron oxide-based contrast medium VSOP-C63 exhibits favorable properties as a blood pool agent for both equilibrium and first-pass MRA. J. Magn. Reson. Imaging 2000;12:905-911.     

肝脏MR动态增强扫描：Gd-EOB-DTPA与Gd-DTPA的个体内对照研究

目的：比较钆塞酸二钠（Gd-EOB-DTPA）及钆喷酸葡胺（Gd-DTPA）肝脏 MR动态增强扫描腹腔脏器及血管的强化特点,重点比较Gd-EOB-DTPA移行期与Gd-DTPA平衡期的图像特点。方法：本研究为前瞻性、个体内随机对照研究。25例病理证实为原发直肠癌或结肠癌、怀疑肝转移的患者,3天内行2次肝脏 MR 动态增强检查,分别使用 Gd-EOB-DTPA及Gd-DTPA两种对比剂。动态增强扫描的序列相同,包括平扫、动脉期、门静脉期、平衡期（Gd-DTPA）／移行期（Gd-EOB-DTPA）。图像客观评估中,测量各期相图像上血管及肝脾实质的信号强度。以椎旁肌肉的信号为参考,计算相对信号强度（RS）并比较两组间的差异,以及不同期相时肝实质RS的差异。主观评估：读片者主观评价增强扫描各期相图像上,主动脉、门静脉及肝静脉与肝实质的相对信号强度。结果：肝实质的RS：在动脉期Gd-DTPA 组明显高于Gd-EOB-DTPA组（t＝3．006,P＝0．005）;在门静脉期及平衡期／移行期,两组检查的差异无统计学意义（t＝1．788,P＝0．086;t＝0．781,P＝0．442）。Gd-EOB-DTPA检查时,门静脉期肝实质RS明显高于动脉期（t＝－3．014,P＝0．006）,移行期RS与门静脉期的差异无统计学意义。Gd-DTPA检查时,平衡期肝实质RS明显低于门静脉期（t＝5．827,P＝0．000）。主观评估：Gd-DTPA增强扫描平衡期图像上所有患者的主动脉、门静脉、肝静脉均为高信号（100％）;Gd-EOB-DTPA 增强扫描移行期图像上主动脉、门静脉、肝静脉均以低或等信号为主（84％,92％,92％）。结论：Gd-EOB-DTPA动态增强 MR 检查,肝脏实质在门静脉期及移行期呈持续强化,其移行期的图像特征与Gd-DTPA平衡期的图像特征有明显不同,在影像诊断时应予以关注。     

Differentiation of hepatic hemangiomas from metastases by dynamic contrast-enhanced MR imaging

Twenty-nine patients with hepatic hemangiomas (n = 14) and hepatic metastases (n = 15) underwent magnetic resonance (MR) imaging prior to and after an intravenous bolus injection of Gd-diethylenetriamine pentaacetic acid (0.2 mmol/kg). Before contrast application, a T2-weighted spin echo sequence (SE 1,600/105) and a T1-weighted gradient echo sequence (GE 315/14/90 degrees pulse angle) were performed. Beginning with injection of the contrast agent, a dynamic study was conducted for 10 min using a moderately T1-weighted gradient echo sequence (GE 40/14/40 degrees) with an acquisition time of 10.2 s per image. Delayed (11 min) and late (60 min) postcontrast images were obtained using a T1-weighted sequence (GE 315/14/90 degrees). In the dynamic study (0-10 min) the hemangiomas were characterized by peripheral contrast enhancement and a subsequent hyperintense fill-in. The metastases showed very mixed patterns of enhancement after contrast administration, and their signal intensity remained low compared with that of the hepatic tissue. In the delayed postcontrast examination (11 min) the hemangiomas had a very high and homogeneous signal intensity and the metastases were characterized by an inhomogeneous, hypointense to isointense signal. The contrast between tumor and liver [signal-difference-to-noise ratio (SD/N)] was higher for all hemangiomas than it was for the metastases. In the T2-weighted precontrast examination, on the other hand, five hemangiomas and seven metastases showed an overlap in the SD/N. The late postcontrast images (60 min) did not yield any further diagnostic information. We conclude that the combination of a dynamic MR study with delayed postcontrast T1-weighted imaging is a useful method of diagnosing hepatic hemangiomas.     

Opacification of the urinary tract in portal venous spiral CT without delayed scans

In portal venous spiral CT there is no visible renal contrast excretion within the usual period of scanning. To opacify collecting systems additional delayed scanning is required. We administered an extra pre-dose of contrast medium before the main portal venous bolus in order to opacify the urinary tract and studied its effects on liver attenuation. In 32 patients examined first by non-contrast spiral CT 20 ml of a non-ionic IV CM were injected. Five minutes later, orientating cuts in the liver and along the urinary tract were obtained. Immediately thereafter, a 120-ml bolus was administered at 3 ml/s for portal venous phase helical CT (60-s delay craniocaudad). The quality of renal excretion was graded visually (excellent, fair, poor, none). Hepatic attenuation measurements were performed at comparable regions of interest. In all patients 20 ml CM opacified the renal pelvis after 5 min. Depiction of the ureters was excellent in 14, fair in 11 and poor or none in 7 cases. There was little effect on mean hepatic attenuation by the 20-ml pre-bolus after 5 min: mean enhancement 2.3 HU (range –0.6 to 7.8 HU). Mean hepatic enhancement after the 120-ml portal venous bolus ranged between 23.6 and 74.1 HU (mean 51.5 HU). When opacification of the urinary tract is necessary, pre-administration of a 20-ml bolus 5 min before portal venous scanning may save an extra delayed spiral. The effects on hepatic enhancement are negligible. Received: 29 October 1998; Revision received: 6 January 1999; Accepted: 1 February 1999