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.     

Gd-DTPA: a bowel contrast agent for magnetic resonance imaging of the abdomen

Forty patients with suspected pathology in the abdomen and pelvis have been investigated with MRI before and after administration of Gd-DTPA as an oral or rectal resolution. The findings are analysed with respect to (a) filling of the GI tract; (b) contrast in the region of interest, surrounding fat and vessels; (c) diagnostic yield in comparison to non-enhanced MRI and contrast CT. At a concentration of 1 mmol/l Gd-DTPA provided consistent positive contrast in the stomach achieved complete filling of the GI tract. The opacification in the region of interest was good or satisfactory in 90% of cases. The diagnostic value of contrast MRI was better in 93% of cases than the non-enhanced MRI of the abdomen. In comparison with contrast CT, the contrast MRI was better or of the same value in 92% of cases. Despite the disadvantages of poor fat-to-bowel contrast (35% of cases were classified as poor), it is concluded that Gd-DTPA-enhanced MRI provides good delineation of organs adjacent to the bowels so this contrast agent has potential for a future role in abdominal MRI. Correspondence to: L. Vlahos     

Multiphasic MR angiography as an intra-individual comparison between the contrast agents Gd-DTPA,Gd-BOPTA,and Gd-BT-DO3A

QUESTION: The availability of new MR contrast agents having either a protein binding effect or higher concentration leads to the question if they differ from standard compounds in their vascular contrasting properties. METHODS: By intraindividual comparison five volunteers were examined (1.5 T MR system) with a multi-phasic MRA of the abdomen each receiving three different contrast agents (gadopentetate dimeglumine 0.5 M; gadobenate dimeglumine 0.5 M, and gadobutrol 1.0 M).The dose (0.15 mmol/kg body weight) and flow rate (3.0 ml/s) were kept identical. All images were quantitatively and qualitatively evaluated by blinded assessment. RESULTS: Significantly higher maximum signal intensity was found in the arteries for the protein interacting gadobenate dimeglumine (p = 0.05). No significant difference in vascular enhancement was demonstrated in the comparison of gadobutrol to gadopentetate dimeglumine. CONCLUSION: Gadobenate dimeglumine was shown to be a favorable contrast agent for multi-phasic MRA. A higher concentrated Gd-chelate does not automatically lead to improved vascular contrast if standard imaging protocols are used.     

Evaluation of a novel time-efficient protocol for gadobenate dimeglumine (Gd-BOPTA)-enhanced liver magnetic resonance imaging

OBJECTIVE: We sought to evaluate gadobenate dimeglumine for the detection and characterization of focal liver lesions in the unenhanced and already pre-enhanced liver. MATERIALS AND METHODS: Sixty patients were evaluated prospectively. Unenhanced T1-weighted gradient echo (T1wGRE) and T2-weighted turbo spin echo (T2wTSE) images were acquired followed by contrast-enhanced T1wGRE images during the dynamic, equilibrium, and delayed phases after the bolus injection of 0.05 mmol/kg gadobenate dimeglumine. An identical series of dynamic images was then acquired after the delayed scan following a second 0.05 mmol/kg bolus of gadobenate dimeglumine. Images were evaluated randomly in 2 sessions by 3 independent blinded readers. Evaluated images in the first session comprised the unenhanced images, the first or second set of dynamic images, and the delayed images. The second session included the unenhanced images, the dynamic images not yet evaluated in the first session, and the delayed images. The 2 reading sessions were compared for lesion characterization and diagnosis, and kappa (kappa) values for interobserver agreement were determined. Quantitative evaluation of lesion contrast enhancement was also performed. RESULTS: The enhancement behavior in the second dynamic series was similar to that in the first series, although pre-enhancement of the normal liver resulted in reduced lesion-liver contrast-to-noise ratios and the visualization of some lesions only on arterial phase images. Typical imaging features for the lesions included in the study were visualized clearly in both series. Strong agreement (kappa=0.56-0.89; all evaluations) between the 2 images sets was noted by all readers for differentiation of benign from malignant lesions and for definition of specific diagnosis, and between readers for diagnoses established based on images acquired in the unenhanced and pre-enhanced liver. CONCLUSION: Dynamic imaging in the hepatobiliary phase gives similar information as dynamic imaging of the unenhanced liver. This might prove advantageous for screening protocols involving same session imaging of primary extrahepatic tumors and liver.     

钆塞酸二钠和钆喷酸葡胺肝脏多期动态增强呼吸伪影对比研究

目的:比较静脉注射钆塞酸二钠(Gd-EOB-DTPA)和钆喷酸葡胺(Gd-DTPA)的动脉期呼吸伪影,寻求减少Gd-EOB-DTPA动脉期呼吸伪影的可能方案.方法:搜集在1年内行Gd-EOB-DTPA和Gd-DTPA磁共振动态增强扫描的患者75例,由两位有经验的磁共振医师采用盲法对两种对比剂扫描方案的动脉期、门脉期及延迟期图像采用5分法评分,以≤3分定义为中重度伪影.两种对比剂扫描方案的呼吸伪影比较采用Wilcoxon秩和检验和配对卡方检验.结果:Gd-EOB-DTPA组发生动脉晚期呼吸伪影的比例明显高于Gd-DTPA组(分别为49.3％和6.7％,Z=-5.058,P＜0.001),其中中重度伪影的比例亦明显高于Gd-DTPA(分别为33.33％和2.67％,x2=21.04,P＜0.001);而Gd-EOB-DT-PA组动脉早期出现呼吸伪影和中重度呼吸伪影的比例与Gd-DTPA组差异无统计学意义(Z=-1.513,P=0.130;x2=0.25,P=0.625).结论:静脉注射Gd-EOB-DTPA较Gd-DTPA更易引起动脉期伪影,减少单期屏气时间和采用动脉期监测技术可能提高Gd-EOB-DTPA动脉期采集的图像质量.     

Yb-DTPA, a novel contrast agent in magnetic resonance imaging: application to rat kidney

We have developed a novel contrast agent, ytterbium-diethylenetriamine pentaacetic acid (Yb-DTPA), for magnetic resonance imaging (MRI) and its mechanism of action is predominantly by the susceptibility mechanism. We have applied this contrast agent for renal MRI studies. We also demonstrate that Yb-DTPA has a renal clearance similar to that of inulin in rats and may therefore be useful for the estimation of glomerular filtration rate.     

Effect of superparamagnetic particles as oral contrast medium at magnetic resonance imaging. A phase I clinical study

Non-biodegradable superparamagnetic particles were used as an oral contrast medium in different concentrations, and evaluated in 25 human volunteers. The aim of the study was to determine the most appropriate concentration of the contrast medium, and to evaluate the effect, distribution, safety and tolerance. With the concentration of 1.0 g/l a substantial reduction of the signal intensity in the bowel was achieved in both T1 and T2 weighted images. The intraabdominal structures were well differentiated from the bowels containing contrast medium. 'Metal' artifacts and blurring of adjacent structures, probably due to an increased local concentration, were observed at higher dosages. The distribution of the preparation in the gastrointestinal tract varied between individuals. As a rule a good contrast effect was achieved in the small bowel with the exception of the duodenum. The contrast medium was well accepted and did not cause any side effects of clinical importance. The results suggest that the preparation is well tolerated by humans and may be a useful contrast medium for abdominal MR imaging.     

Magnetic resonance imaging of myocardial infarction using albumin-(Gd-DTPA), a macromolecular blood-volume contrast agent in a rat model

Magnetic resonance (MR) contrast enhancement of acute myocardial infarction was studied in rats using albumin-(Gd-DTPA), a paramagnetic macromolecule with prolonged intravascular retention after intravenous injection. Histologic examination and distribution measurements of radiolabeled microspheres confirmed induction of regional myocardial infarction after ligation of the left coronary artery. ECG-gated spin-echo images at 2.0 Tesla, employing short, T1-weighted pulse sequence settings, demonstrated time-persistent and significant (P less than .05) enhancement of normal myocardium (66%) and an even greater enhancement of the infarcted area (100%), for as long as 60 minutes after injection of 160 mg/kg albumin-(Gd-DTPA). The contrast difference between normal and infarcted myocardium was increased significantly (P less than .05) after administration of albumin-(Gd-DTPA). The prolonged enhancing effects of albumin-(Gd-DTPA) on MR images are useful for evaluating regional differences in blood volume and capillary integrity between normal and infarcted myocardium.     

Magnesium sulfate as an oral contrast medium in magnetic resonance imaging of the small intestine

Background

To explore the use of magnesium sulfate (MgSO₄) as an oral contrast medium (CM) in MRI of the small intestine.

Methods

By comparing MgSO₄ SNRs at different concentrations, we determined that 2.5% MgSO₄ is the ideal concentration for small bowel MRI. Twenty volunteers underwent MRI after drinking 2.5% MgSO₄. Thirty-one patients with clinical suspicion of small intestinal pathology underwent both MRI and the air-barium contrast examination. The patient's tolerance, side effects and complications were noted.

Results

2.5% MgSO₄ can decrease the absorption of water and fully fill the enteric cavity, thereby increasing the contrast between the intestinal wall and lumen and facilitating radiographic examination of the small bowel. The mean diameter of the small intestine was 19.8 ± 1.21 mm in the 20 volunteers consuming 2.5% MgSO₄ and 12.7 ± 0.84 mm in the 20 volunteers given water. There was a significant difference (P < 0.05) between the diameters of the small intestine of the two groups. But there were no significant differences (P > 0.05) in side effects between MgSO₄ and water groups. Small intestinal MRI was successfully performed in all 31 patients, who were also examined by the double contrast barium, which gave almost identical diagnoses to MRI in all cases except for 1 patient with small intestinal hemorrhage.

Conclusions

MRI with 2.5% MgSO₄ can demonstrate intestinal abnormalities. Therefore, 2.5% MgSO₄ solution is an ideal oral CM for small bowel MRI.     

A comparative study of magnetic resonance imaging and computed tomography in the evaluation of migraine

Seventy-four patients with classic migraine were examined by magnetic resonance imaging (MRI) and contrast enhanced head CT scanning. Patients chosen for the study ranged in age from 9 to 39 years with a mean age of 28 years. All had documented symptoms of classic migraine for over two years. Nineteen of the seventy-four patients (26%) had multiple foci of bright signal in the brain on T2 weighted MRI. None of these parenchymal abnormalities were detected on CT scans. Twenty-six patients (35%) had both MRI and CT demonstration of focal or generalized ventricular enlargement or sulcal prominence. These atrophic findings were shown equally well by both modalities. Ten patients (14%) with atrophic changes showed concomitant small bright foci of T2 signal abnormality. An additional migraine patient with homonymous hemianopsia had a large occipital lobe infarct which was seen as a region of bright T2 signal abnormality on MRI. Typical CT characteristics of an acute infarct were demonstrated.     

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.     

Evaluation of a nitroxyl fatty acid as liver contrast agent for magnetic resonance imaging

In this study, we report the synthesis and the evaluation as MRI contrast agent of a new compound (nitroxyl fatty acid, NFA), where a pyrrolidinoxyl radical (3-carboxy-proxyl, PCA) is linked to a fatty acid moiety. Fatty acids were selected as vector because they present a high affinity for the liver, their efficient cellular uptake being the result of a specific interaction with a transmembrane transporter (liver plasma membrane-fatty acid binding protein). The uptake of ³H-oleic acid is inhibited after the injection of 1 mmol/kg of NFA, suggesting that INFA recognizes the same transmembrane transporter as the natural fatty acids. The higher relaxivity R₁ of NFA in albumin solutions, compared with PCA, was explained by the immobilization of the nitroxyl radical in the protein. MR imaging was performed using T₁-weighted images on mice in order to compare the contrast effect obtained after the injection of 1 mmol/kg of radical. The % signal enhancement in the liver 5 min after intravenous injection was 49 ± 4 and 14 ± 5 for NFA and PCA, respectively. NFA allowed a better delimitation of some necrotic tumors (Novikoff hepatocarcinoma) due to its preferential uptake by the nontumorous tissue.     

A comparative study of magnetic resonance imaging and computed tomography-assisted myelography in spinal dysraphism

Thirty-seven patients with a wide spectrum of spinal dysraphic lesions were studied by both magnetic resonance imaging (MRI) and myelography complemented by computed tomography (CT). Magnetic resonance imaging proved to be superior for tissue characterization, overall anatomical definition, topographical relationships of the cranio-cervical junction and demonstration of the presence and extent of hydrosyringomyelia. Demonstration by CT myelography of fine neural structures such as the filum terminale and nerve roots remains the superior technique; however, with constantly improving spatial resolution and thinner-slice imaging, MRI will become increasingly competitive in this respect. The osseous component of these lesions was best demonstrated by CT myelography. A high incidence of associated syrinx (8/15 cases) was found in the diastematomyelia group, with an overall incidence of 15 cases in all the dysraphic patients studied. The use of both T1- and T2-weighted sequences is required for tissue characterization. Whilst both imaging modalities proved complementary in the investigation of spinal dysraphism, we suggest that, with its superior tissue characterization and anatomical display of these lesions. MRI should be the primary imaging technique. Avoidance of an invasive procedure and use of ionizing radiation confers additional benefits upon MRI. The relative ease and shorter examination time of MRI makes this technique ideal for pre- and post-operative monitoring and assessment.     

Ferromagnetic particles as contrast agents for magnetic resonance imaging of liver and spleen

Particles of magnetite, Fe3O4, accumulate preferentially in the liver and spleen after intravenous injection. Their magnetic fields drastically decrease echo intensities in spin-echo proton magnetic resonance imaging sequences, as demonstrated by experiments on dogs injected with 10 mg/kg of 0.05-micron particles.