Dynamic contrast-enhanced MR imaging of the upper abdomen: Enhancement properties of gadobutrol,gadolinium-DTPA-polylysine,and gadolinium-DTPA-cascade-polymer

The enhancement properties of gadobutrol (40 and 80 μmol/kg body weight, 550 daltons), gadolinium-DTPA-polylysine (20 μmol/kg body weight, 53,000 daltons) and gadolinium-DTPA-cascade-polymer (20 μmol/kg body weight, < 30,000 Daltons) were investigated in abdominal MR imaging using a pig model (n = 24). Signal intensities before and after contrast media application were assessed using a fast single slice FLASH sequence. Measurements were made every 4 s within the first 116 s, every minute between 4 and 10 min and after 15,20,30,40, 50,60,90, and 120 min after contrast media injection. Injection of gadobutrol resulted in typical signal intensity curves characterizing it as an extracellular agent similar to gadopentetate dimeglumine. Significant enhancement was found in all tissues except the trunk muscles when the lower dose was administered. Gadolinium-DTPA-polylysine injection resulted also in significant enhancement of the liver, the pancreas, and the renal cortex, but not of the trunk muscle, reflecting its blood pool properties known also from other macromolecular contrast agents. The signal intensity curves obtained after gadolinium-DTPA-cascade-polymer injection were similar to those obtained after polylysine injection, stressing the blood pool character of this new type of blood pool agent.     

Effect of varying the molecular weight of the MR contrast agent Gd-DTPA-polylysine on blood pharmacokinetics and enhancement patterns

The effects of varying the molecular weight of gadolinium-DTPA (diethylenetriaminepentaacetic acid)—polylysine, a macromolecular magnetic resonance (MR) imaging contrast agent, on blood pharmacokinetics and dynamic tissue MR imaging signal enhancement characteristics were studied in normal rats. Blood elimination half-life, total blood clearance, volume of the central compartment (V_cc) and the steady-state distribution volume (V_ssd) were calculated for four Gd-DTPA-polylysine polymers with average molecular weights of 36, 43.9, 139, and 480 kd and compared with corresponding values for Gd-DTPA (0.57 kd) and Gd-DTPA-albumin (92 kd). Blood elimination half-life increased sevenfold with an increase in molecular weight from 36 to 480 kd. The V_cc values for all polylysine polymers did not differ significantly from the V_cc value for Gd-DTPA-albumin but were significantly smaller than the V_cc value for Gd-DTPA. The V_ssd value for Gd-DTPA did not differ significantly from the V_ssd value for the 36- and 43.9-kd polymers but was significantly larger than the V_ssd values for the 139-and 480-kd polymers and for Gd-DTPA-albumin. On T1-weighted coronal spin-echo MR images, dynamic signal enhancement profiles in liver and kidney for the 36-, 43.9-, and 480-kd Gd-DTPA-polylysine chelates corresponded to the blood pharma-cokinetic data. Increasing molecular weight of Gd-DTPA-polylysine formulations substantially slows blood clearance and produces a prolonged, almost constant tissue signal enhancement for the 60-minute observation period.     

Dynamics of tumor imaging with Gd-DTPA—polyethylene glycol polymers: Dependence on molecular weight

Macromolecular contrast media offer potential advantages over freely diffusible agents in magnetic resonance (MR) imaging outside the central nervous system. To identify an optimum molecular weight for macromolecular contrast media, the authors studied a novel macromolecular contrast agent, gadolinium diethylenetriaminepentaacetic acid polyethylene glycol (DTPA-PEG), synthesized in seven polymer (average) molecular weights ranging from 10 to 83 kd. Twenty-eight rabbits bearing V2 carcinoma in thighs underwent T1-weighted spin-echo imaging before injection and 5–60 minutes and 24 hours after injection of the Gd-DTPA-PEG polymers or Gd-DTPA at a gadolinium dose of 0.1 mmol/kg. Tumor region-of-interest measurements were obtained at each time point to determine contrast enhancement dynamics. Blood-pool enhancement dynamics were observed for the Gd-DTPA-PEG polymers larger than 20 kd. Polymers smaller than 20 kd displayed dynamics similar to those of the freely diffusible agent Gd-DTPA. Above the 20 kd threshold, tumor enhancement was more rapid for smaller polymers. The authors conclude that the 21.9-kd Gd-DTPA-PEG polymer is best suited for clinical MR imaging.     

Detection of zonal renal ischemia with contrast-enhanced MR imaging with a macromolecular blood pool contrast agent.

The potential of magnetic resonance (MR) imaging enhanced with albumin-(gadolinium diethylenetriaminepentaacetic acid [DTPA])35, a macromolecular blood pool marker, for detection of focal changes in renal perfusion was studied in a myoglobinuric acute renal failure (ARF) model in the rat. T1-weighted spin-echo postcontrast images of injured kidneys at 3 hours after glycerol injection showed three distinct zones: a strongly enhanced outer cortex, a low-intensity inner cortex, and a strongly enhanced medulla. The distinct band of low intensity in the inner cortex indicated zonal decreased blood volume, corresponding to published microsphere data showing zonal low perfusion in the inner cortex. Contrast differences between parenchymal zones were significant for at least 30 minutes. No focal ischemic changes could be delineated on nonenhanced images. Enhanced and nonenhanced images of injured kidneys obtained at 24 hours after glycerol injection revealed no zonal differentiation. Contrast-enhanced MR imaging data in this ARF model correlated well with pathologic data and microsphere perfusion results. Contrast-enhanced characterization of the ischemic phase of renal injury with MR imaging may improve specificity for the diagnosis of ARF and may serve as a marker for therapeutic intervention.     

Selective enhancement of experimental rat brain tumors with Gd-TPPS

The synthetic metalloporphyrin gadolinium (III)-tetraphenylporphine sulfonate (TPPS) was successfully used as a contrast agent for in vivo magnetic resonance (MR) imaging of rat brain glioma. After injection of Gd-TPPS, the signal intensity of experimental rat brain glioma distinctly increased on T1-weighted MR images, an effect similar to that produced by the clinically applied MR imaging contrast agent gadolinium diethylenetriaminepentaacetic acid (DTPA). In contrast to other contrast agents studied (Gd-DTPA, manganese [III]-TPPS), Gd-TPPS produced hypointensity in glioma on T2-weighted images. The tumor-selective accumulation of paramagnetic Gd-TPPS in glioma shortened T1 by 53%, from 1,315 msec ± 199 to 628 msec ± 106, and T2 by 34%, from 86 msec ± 4 to 57 msec ± 5 (2 days after injection of 0.25 mmol/kg Gd-TPPS). The relaxation times of normal cortex, striaturn, corpus callosum, and temporal muscle were not significantly affected. As a result, gliomas appeared hyperintense on T1-weighted images and hypointense on T2-weighted images. Owing to the strong effect of Gd-TPPS on the T2 of glioma, normal brain tissue, tumor, and peritumorous edema could be distinguished on T2-weighted images alone.     

Comparison of three different injection methods for arterial phase of Gd-EOB-DTPA enhanced MR imaging of the liver

Objective

To compare three different injection methods for optimizing hepatic arterial phase of gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (Gd-EOB-DTPA) enhanced MR imaging.

Methods

Arterial phase images were obtained after the injection of contrast agent at a rate of 3 mL/s with diluted Gd-EOB-DTPA (dilution method) in 27 patients, 3 mL/s with undiluted Gd-EOB-DTPA (3 mL method) in 26 patients and 1 mL/s with undiluted Gd-EOB-DTPA (1 mL method) in 28 patients. In the quantitative evaluation, signal-to-phantom ratios (SPR) of the liver parenchyma, pancreas, renal cortex, portal vein and aorta were evaluated. In the qualitative evaluation, the seven items for image quality of hepatic arterial phase were assessed, and the total score of all items in each subject was calculated.

Results

The score of enhancement of abdominal aorta and total score of seven items in 1 mL method were significantly higher than those in 3 mL method. The SPR of the liver parenchyma in 3 mL method was significantly higher than that in 1 mL method, suggesting substantial hepatic inflow from portal venous return.

Conclusion

For the optimal arterial phase imaging, injection rate of 1 mL/s with undiluted Gd-EOB-DTPA is convenient and preferable, compared with other two methods, based on our qualitative analysis.     

Long-residence-time nano-scale liposomal iohexol for X-ray-based blood pool imaging

RATIONALE AND OBJECTIVES: Although soluble nonionic iodine compounds with low systemic toxic effects have been developed for use in computed tomography (CT), they have short residence times of a few minutes or mere seconds-insufficient time for blood pool imaging, even with high-speed multi-detector row spiral CT. Moreover, potential renal toxic effects preclude repeated administration of these contrast agents during imaging, as well as their use in patients with compromised renal function. The objective of this study was to develop and evaluate a CT contrast agent for blood pool imaging that remains in the blood for more than 3 hours and that is relatively nontoxic to the kidneys. MATERIALS AND METHODS: The authors assessed a liposomal iohexol formulation for its encapsulation efficiency in terms of milligrams of iodine per milliliter of lipid formulation and for its stability in phosphate buffer solution and in human plasma in vitro. Using a rabbit model, they also assessed the formulation's in vivo stability, residence time, and enhancement of contrast on images of various organ systems. RESULTS: The formulation, which contained 34.8 mg of iodine per milliliter of liposomal iohexol solution, remained stable in blood plasma both in vitro and in vivo, after injection into rabbit vasculature. An intravenous dose of 475 mg of iodine per kilogram of body weight produced contrast enhancement in the rabbit model of approximately 130 HU in the aorta and liver cortex and approximately 100 HU in the kidney cortex. Contrast enhancement was maintained for 3 hours after injection, and minimal clearance of the contrast agent via the kidneys was observed. CONCLUSION: The liposomal iohexol formulation tested in this study had a sufficient residence time for blood pool imaging in a rabbit model. Future experiments with long-residence-time iohexol formulations may lead eventually to applications in cardiac imaging and in early tumor detection.     

Dynamic signal intensity changes in liver with superparamagnetic MR contrast agents.

The dynamic effects of three different superparamagnetic magnetic resonance (MR) contrast agents on liver signal were evaluated with an echo-planar imaging technique. The contrast agents were (a) USPIO (ultrasmall superparamagnetic iron oxide), which has a long blood half-life and was developed for MR imaging of lymph nodes and bone marrow; (b) AG (arabinogalactan)-USPIO, an asialoglycoprotein receptor--directed iron oxide with hepatocyte uptake; and (c) AMI-25, a conventional reticuloendothelial iron oxide agent. Dynamic liver signal intensity (SI) curves reflect different uptake mechanisms for the different agents. Receptor blocking experiments indicate that intracellular redistribution or clustering of the AG-USPIO (known to occur from electron microscopy studies) does not contribute to the decrease in liver SI. Monitoring liver SI over time with echo-planar imaging may provide a better understanding of the kinetics of the growing number of MR contrast agents and allow optimization of imaging protocols to exploit peak enhancement.     

Phase I clinical evaluation of a new iron oxide MR contrast agent

The safety and magnetic resonance (MR) imaging potential of BMS 180549, a new superparamagnetic iron oxide contrast agent, were evaluated in a phase I, open-label, placebo-controlled study involving 41 healthy subjects. No clinically significant postdose changes in physical examination findings, vital signs, or electrocardiogram results were reported for any of the subjects evaluated. No clinically significant changes in clinical laboratory values were noted by the investigators. Fourteen adverse events considered not serious and considered possibly or definitely related to the drug were reported, three of which required minor treatment. Relaxation time measurements in plasma samples showed a strong, dose-dependent, and persistent decrease in T1 and T2 values. Significant changes in MR signal intensity of the blood pool and wellperfused organs (liver and spleen) were noted on both T1- and T2-weighted images. Changes in signal intensity of cervical lymph nodes were also observed at the higher doses and late postdose imaging times.     

Contrast-enhanced MR imaging of diffuse and focal splenic disease with use of magnetic starch microspheres

The diagnostic value of magnetic starch microspheres (MSM), a new superparamagnetic contrast agent, was studied in experimental models of diffuse and focal splenic disease in rats by means of ex vivo relaxometry and in vivo magnetic resonance (MR) imaging. Owing to small differences in unenhanced T1 and T2 values between diffuse lymphoma and normal spleen, MR imaging failed to distinguish tumor-bearing animals from control animals by signal-to-noise ratios (SNRs) obtained with T1- and T2-weighted spin-echo sequences. One hour after injection of 20 μmol/kg MSM, lymphomatous spleen showed significantly (P <.001) reduced enhancement relative to normal splenic tissue. As a result, animals with diffuse lymphoma (SNR: 10.3 ± 1.7) could be easily differentiated from control animals (SNR: 5.5 ± 0.6) on T2-weighted (TR msec/TE msec = 2,000/45) images. In focal splenic disease, MSM produced normal enhancement of nontumorous splenic tissue, whereas relaxation times of tumors were not different before and after contrast agent injection. On T2-weighted images (2,000/45), the tumor-spleen contrast-to-noise ratio increased from (4.8 ± 1.6 to 21.8 ± 1.9 +354%), improving conspicuity of splenic tumors. The results show that MSM-enhanced MR imaging improves the detection of diffuse and focal splenic disease.     

Paramagnetic polymerized liposomes as new recirculating MR contrast agents

We describe a well-tolerated blood pool contrast agent with extended reclrculatory half-life based on paramagnetic polymerized liposomes (PPLs). PPLs were constructed from a new type of polymerizable lipid molecule that has a derivative of gadopentetate dimeghimine as the hydrophilic head group and diacetylene groups in the hydrophobia acyl chains, which cross-link when irradiated with ultraviolet (UV) light. Biodistributlon, blood pool half-life, and MR image enhancement were determined for PPLs composed of 10% of the gadopentetate dimeglumine lipid and 90% of ditricosadiynoyl tricosadiynayl phospha-tidylcholine (DAPC) at a dose of 0.015 mmnol Gd⁺³/kg in rats. In T1-weighed MR images (TR/TE = 400/18 msec), an average signal enhancement of 34% in the kidneys and 20% in the liver was observed, which persisted for at least 90 minutes after administration of the PPLs. Biodistribution studies using radiolabe-led PPLs confirmed that 80% of the injected dose remained in the blood pool after 2 hours. The half-life of elimination from the blood pool was 19 hours. The preparation was well tolerated in rats and produced similar MR contrast enhancement of the blood pool as produced by other liposome contrast agents. However, the half-life of PPL elimination from the blood pool was prolonged relative to other liposome systems.     

Three-dimensional cardiac cine magnetic resonance imaging with an ultrasmall superparamagnetic iron oxide blood pool agent (NC100150)

The purpose of this study was to assess image quality of three-dimensional (3D) cardiac cine magnetic resonance (MR) imaging before and after administration of a T1-shortening ultrasmall superparamagnetic iron oxide blood pool agent (NC100150). 3D cardiac cine MR imaging was performed in 13 volunteers using a radiofrequency-spoiled cardiac-gated 3D cine gradient-echo sequence with short repetition and echo times. Compared with precontrast images, postcontrast images showed no enhancement in fat and skeletal muscle, moderate enhancement in myocardium, and significant enhancement in ventricular cavity. After contrast injection, the signal ratio of the ventricular chamber to the myocardium significantly increased, and dramatic improvements were seen in the quality of the cineangiographic images and the depiction of cardiac valves. This quantitative study has shown that 3D cardiac cine MR imaging using a blood pool agent provided MR ventriculography and cineangiography with excellent image quality.     

Enhancement effects of a hepatocyte receptor—specific MR contrast agent in an animal model

The enhancement characteristics of the liver and spleen produced by a hepatocyte-specific magnetic resonance imaging agent, an arabinogalactan-coated ultrasmall superparamagnetic iron oxide derivative, BMS 180550, were evaluated. Both heavily T1- and T2-weighted sequences were used. Imaging was performed in the farm pig model, as a function of contrast agent concentration (5, 10, and 20 μmol of iron per kilogram) and delay (immediate, 0.5, 2.5, 5.0, 7.5, and 9.0 hours) after bolus injection of BMS 180550. BMS 180550 provided excellent contrast enhancement characteristics by producing marked positive enhancement with T1-weighted sequences and marked negative enhancement with T2-weighted sequences. The T1-weighted enhancement immediately after contrast agent injection was of greater magnitude in the spleen (329% ± 83) than in the liver (66% ± 16). Postcontrast negative enhancement with T2-weighted sequences was largely hepatocyte specific at 5 and 10 μmol/kg but was also seen within the spleen at 20 μmol/kg. The authors discuss the possible mechanisms that produce these changes and conclude that 10 μmol/kg BMS 180550 is near the optimum dose for maximizing the enhancement properties of this agent with all sequences in the farm pig.     

Preliminary clinical trial of gadodiamide injection: a new nonionic gadolinium contrast agent for MR imaging.

The safety and efficacy of a newly developed intravenous formulation of the nonionic contrast agent gadolinium diethylenetriaminepentaacetic acid-bis(methylamide), formulated as gadodiamide injection, was investigated. In 30 patients who underwent spin-echo magnetic resonance (MR) imaging before and after contrast agent enhancement, the enhanced images had characteristics judged similar to those of images enhanced by means of available gadolinium compounds. In 15 patients, contrast agent administration was of major diagnostic help, either revealing lesions not apparent without enhancement or providing important lesion characterization. In 12 patients, the lack of abnormal enhancement patterns was important in excluding the presence of disease. In three patients, the contrast agent did not provide information additional to that obtained with the unenhanced T1- and T2-weighted images. No clinically significant changes were observed in vital signs, neurologic status, or laboratory results. The authors conclude that, in this limited series, gadodiamide injection proved to be a safe and useful MR imaging contrast agent for evaluation of the central nervous system and surrounding structures.     

Prolonged positive contrast enhancement with Gd-EOB-DTPA in experimental liver tumors: Potential value in tissue characterization

To evaluate the potential of the hepatobiliary magnetic resonance (MR) imaging contrast agent gadolinium EOB-DTPA (ethoxybenzyl diethylenetria-minepentaacetic acid) for the characterization of hepatic tumors, 79 primary and six implanted hepatomas in 38 rats were studied. MR imaging findings after administration of Gd-DTPA (0.3 mmol/kg) and Gd-EOB-DTPA (30 μmol/kg) were correlated with microangiographic and histologic findings. Gd-EOB-DTPA produced a strong liver enhancement, which caused prompt negative contrast enhancement (CE) in all implanted hepatomas and in 77 of 79 primary hepatomas. A positive CE that lasted up to 2 hours was found in two of 79 primary hepatomas, both of which were highly differentiated (grade I) hepatocellular carcinomas (HCCs). The rest were moderately differentiated to undifferentiated HCCs (grades II-IV). Rim enhancement, which corresponded histologically to peritumoral malignant infiltration sequestering normal hepatocytes, was seen around all implanted and some primary hepatomas. Positive tumor CE after administration of Gd-EOB-DTPA in this study is much less frequent but much more specific in comparison with the results of previous studies with manganese-DPDP (N, N′-dipyridoxylethylenediamine-N,N′-diacetate 5,5′-bis[phosphate]). These findings may help further discriminate hepatic tumors.     

Use of superparamagnetic contrast media to suppress signal from flowing spins: Preliminary experience

The authors describe their preliminary experience with the use of superparamagnetic magnetic resonance (MR) imaging contrast media for suppression of signal from flowing blood. The goal of this work was to determine if a superparamagnetic contrast agent could successfully eliminate blood signal during cardiac-gated MR imaging, thereby eliminating or reducing flow artifacts associated with the complex and variable hemodynamics within the heart chambers. Imaging and data analysis were performed in 17 dogs subjected to experimental myocardial infarction as part of a parallel project. Six doses (0.2, 1, 2, 3.5, 4, 5, and 10 mg/kg) of AMI-25, an experimental contrast agent, were used in the study. Spin-echo imaging was performed immediately before and every 5 minutes (for an average of 25 minutes) after bolus injection of the contrast agent. Variations in the image signal-to-noise ratio relative to a baseline (before injection of contrast agent) image were assessed as a function of dose and time. Preliminary results suggest that a considerable reduction in blood flow artifacts and, hence, increases in image signal-tonoise ratio can be achieved at doses greater than or equal to 3.5 mg/kg, for approximately 20 minutes after injection. Doses equal to or less than 2 mg/kg and images obtained more than 20 minutes after injection (regardless of dose) did not reliably show hemodynamic artifact suppression.     

Contrast-enhanced MR imaging of liver and spleen: First experience in humans with a new superparamagnetic iron oxide

The aim of this prospective study was to obtain the first human safety and magnetic resonance (MR) imaging results with a new formulation of superparamagnetic iron oxide (SPIO) (SHU 555 A). The SPIO was tested at four iron doses, from 5 to 40 μmol/kg. Laboratory tests and clinical measurements were done in 32 healthy volunteers for up to 3 weeks after administration. MR imaging at 1.5 T was performed before and 8 hours to 14 days after fast intravenous injection (500 μmol Fe/min) of the SPIO (six subjects per dose). Results of this phase I study demonstrate that SHU 555 A at a concentration of 0.5 mol Fe/L was well tolerated. A dose-dependent minor increase in activated partial thromboplastin time, which remained within the normal range, was seen. All doses of SPIO caused a signal loss in both liver and spleen (P <.05) with a spin-echo sequence (TR = 2,300 msec, TE = 45 msec). The signal losses in the liver 8 hours after contrast agent injection were 58%, 79%, 82%, and 87% for the 5, 10, 20, and 40 μmol Fe/kg doses, respectively. The corresponding signal losses in the spleen were 23%, 45%, 65%, and 78%, respectively. The doses that reduced signal intensity by half were 3.1 μmol Fe/kg for the liver and 12.8 μmol Fe/kg for the spleen. The results suggest that the new SPIO formulation is a safe and efficient MR contrast agent.     

Gd-DTPA-polylysine—enhanced pulmonary time-of-flight MR angiography

The enhancing effect of gadolinium diethylenetriam-inepentaacetic acid (DTPA) polylysine (a macromolecular paramagnetic contrast agent) in time-of-flight magnetic resonance (MR) angiography of isolated perfused sheep lungs was studied. Unilateral lung damage was induced with hydrochloric acid in eight sheep. The heart and lungs were removed from the thoracic cavity, and after cannulation of the trachea and both ventricles, pulsatile perfusion and ventilation were initiated. The heart-lung preparations were placed in the head coil of a 1.5-T imager. Time-of-flight pulmonary MR angiography was performed during respiratory arrest, before and after administration of 0.02 mmol/kg Gd-DTPA-polylysine. On the postcontrast angiograms, the signal intensity increased by 120% in pulmonary arteries (P <.01). The contrast-to-noise ratio between pulmonary arteries and parenchyma increased significantly (P <.01). The number of visualized generations of pulmonary artery branches increased from four to six in normal lungs and from three to five in edematous lungs. Low-dose Gd-DTPA-polylysine significantly improves the conspicuity of the pulmonary vascular tree in time-of-flight pulmonary MR angiography.     

MR imaging of myositis ossificans: Variable patterns at different stages

Five patients with a palpable mass at presentation underwent magnetic resonance (MR) imaging. The final diagnosis was myositis ossificans (MO). MR imaging features, particularly after injection of gadopentetate dimeglumine, mimicked those of an inflammatory mass or neoplasm. The lesions were excised in three patients, and the Images were correlated with histologic findings. Three different appearances were noted on MR images, corresponding to the stages of maturation of MO. Two cases Involved early-stage lesions, and Tl-weighted MR images showed a mass with homogeneous intermediate signal intensity. Both lesions showed rim enhancement after contrast agent injection and high signal intensity on T2-weighted images. Pathologic specimens demonstrated stroma with masses of spindle cells in which osteoid production was interspersed. The enhanced rim of the lesion mimicked the expected MR appearance of an abscess or necrotic tumor. Areas of enhancement in adjacent muscle were also seen on postcontrast T1-weighted images. Intermediate-stage MO was present in one case; there was evidence of a thin rim of calcification on plain radiographs and fatty changes in the lesion on T1-weighted Images, corresponding with histologic findings. One case of a mature lesion showed a considerable degree of peripheral calcification both on MR images and at histology. MR imaging is nonspecific in the diagnosis of early-stage MO.     

超顺磁性氧化铁在大鼠诱癌模型磁共振诊断与鉴别诊断中的作用

目的研究超顺磁性氧化铁(SPIO)在大鼠诱癌模型的磁共振成像中对增生性结节与肝癌的鉴别作用，以及SPIO增强前后对各型肝癌的检出率。材料与方法42只诱发型肝癌模型鼠在肝硬化多发增生性结节基础上，共计生成379个肝癌，行平扫及SPIO增强扫描，分析增生性结节与肝癌的不同强化方式，并与病理对照统计平扫与增强扫描各型肝癌的检出率。结果增生性结节在SPIO增强扫描T2WI上信号明显降低，而肝癌的信号无明显改变；肝癌SPIO增强扫描T2WI检出率与病理接近，而平扫T2WI检出率与病理相差显著，其中平扫微癌与小癌的漏检率分别达32．9％与12．9％。结论SPIO是一种有效的检测肝癌的磁共振对比剂，不仅能提高小肝癌的检出率而且对增生性结节与肝癌的鉴别提供帮助。