Extravascular toxicity of two magnetic resonance contrast agents. Preliminary experience in the rat

Intravenous contrast medium extravasation: systematic review and updated ESUR Contrast Media Safety Committee Guidelines

NEED FOR A REVIEW

Guidelines for management and prevention of contrast media extravasation have not been updated recently. In view of emerging research and changing working practices, this review aims to inform update on the current guidelines.

AREAS COVERED

In this paper, we review the literature pertaining to the pathophysiology, diagnosis, risk factors and treatments of contrast media extravasation. A suggested protocol and guidelines are recommended based upon the available literature.

KEY POINTS

• Risk of extravasation is dependent on scanning technique and patient risk factors. • Diagnosis is mostly clinical, and outcomes are mostly favourable. • Referral to surgery should be based on clinical severity rather than extravasated volume.

Albumin-based nanoparticles as contrast medium for MRI: vascular imaging, tissue and cell interactions, and pharmacokinetics of second-generation nanoparticles

This multidisciplinary study examined the pharmacokinetics of nanoparticles based on albumin-DTPA-gadolinium chelates, testing the hypothesis that these nanoparticles create a stronger vessel signal than conventional gadolinium-based contrast agents and exploring if they are safe for clinical use. Nanoparticles based on human serum albumin, bearing gadolinium and designed for use in magnetic resonance imaging, were used to generate magnet resonance images (MRI) of the vascular system in rats ("blood pool imaging"). At the low nanoparticle doses used for radionuclide imaging, nanoparticle-associated metals were cleared from the blood into the liver during the first 4 h after nanoparticle application. At the higher doses required for MRI, the liver became saturated and kidney and spleen acted as additional sinks for the metals, and accounted for most processing of the nanoparticles. The multiple components of the nanoparticles were cleared independently of one another. Albumin was detected in liver, spleen, and kidneys for up to 2 days after intravenous injection. Gadolinium was retained in the liver, kidneys, and spleen in significant concentrations for much longer. Gadolinium was present as significant fractions of initial dose for longer than 2 weeks after application, and gadolinium clearance was only complete after 6 weeks. Our analysis could not account quantitatively for the full dose of gadolinium that was applied, but numerous organs were found to contain gadolinium in the collagen of their connective tissues. Multiple lines of evidence indicated intracellular processing opening the DTPA chelates and leading to gadolinium long-term storage, in particular inside lysosomes. Turnover of the stored gadolinium was found to occur in soluble form in the kidneys, the liver, and the colon for up to 3 weeks after application. Gadolinium overload poses a significant hazard due to the high toxicity of free gadolinium ions. We discuss the relevance of our findings to gadolinium-deposition diseases.

Magnetic Resonance Lymphography of Lymphatic Vessels in Upper Extremity With Breast Cancer-Related Lymphedema

BACKGROUND

Magnetic resonance lymphangiography (MRL) has been proven to be able to visualize pathological lymphatic networks and accompanying complications through subcutaneous injection of commonly used contrast agents. However, no comprehensive prior studies have previously been reported regarding MRL for the evaluation of upper extremity lymphedema in patients with breast cancer-related lymphedema (BCRL). In this study, we establish a novel MRL protocol to characterize the normal and abnormal characteristics of different clinical stages of BCRL in patients using high-spatial-resolution MRL.

METHODS

Fifty females with unilateral upper extremity BCRL underwent MRL. Lymphatic vessel morphology in normal and affected limbs was compared. The appearance, distribution pattern, morphologic characteristics, and maximum transversal diameter of the lymphatic vessels, dermal backflow, and regeneration of lymphatic vessels were analyzed.

RESULTS

Lymph fluid was retained in the subcutis of the affected limbs, and no edema was observed in the subfascial compartment. In stage 1, tortuous and dilated lymphatic vessels exhibited a beaded appearance, and their diameters were larger than those in the contralateral forearm (P < 0.05). In stage 2, the dilated lymphatic vessels exhibited larger diameters. "Dermal backflow" and tiny regenerated lymphatic vessels appeared. The thickened subcutaneous tissue showed a honeycomb pattern induced by soft tissue fibrosis and adipose hypertrophy. In stage 3, disordered and unrecognizable affected lymphatic vessels were observed with many small regenerated lymphatics and confluent dermal backflow; the tissue fibrosis was more serious.

CONCLUSIONS

Each stage presents different characteristics, and the deformity degree of the lymphatic network is consistent with the severity of the disease. Magnetic resonance lymphangiography could provide adequate information for clinical staging in patients with BCRL.

Gadolinium complexes of diethylenetriamine-N-oxide pentaacetic acid-bisamide: a new class of highly stable MRI contrast agents with a hydration number of 3

Diethylenetriamine-N-oxide pentaacetic acid-bisamide-based Gd(iii) complexes with 3 coordinated water molecules have been synthesized to achieve high stability and over three times of the relaxivities of commercial MRI contrast agents.

MR Lymphangiography: A Practical Guide to Perform It and a Brief Review of the Literature from a Technical Point of View

We propose a practical approach for performing high-resolution MR lymphangiography (MRL). We shall discuss and illustrate the technical approach for the visualization of lymphatic vessels in patients suffering from lymphedema, how to distinguish lymphatic vessels from veins, and MRL role in supermicrosurgery treatment planning. A brief review of literature, from a technical point of view, is also reported.

Magnetic resonance imaging versus lymphoscintigraphy for the assessment of focal lymphatic transport disorders of the lower limb: first experiences

PURPOSE

To compare the diagnostic accuracy of magnetic resonance imaging (MR-lymphangiography) and lymphoscintigraphy for assessment of focal lesions of the peripheral lymphatic system. Patients with focal lymphatic transport disorders might benefit from surgi-cal interventions.

PATIENTS, METHODS

We examined by lymphoscintigraphy and MR-lymphangiography a total of 85 lower limbs in 46 consecutive patients (33 women; mean age 41 years; range 9-79 years) presenting with uni- or bilateral lymphedema. MR-lymphangiographies were obtained at isotropic sub-millimeter resolution with a 3.0 Tesla magnet after injection of gadolinium contrast medium. MR-lymphangiography was reviewed by radiologists, whereas lymphoscintigraphy was reviewed by nuclear medicine physicians. The images were examined for localization and distribution of any focal lesions of the lymphatic vessel system. Diagnostic accuracy of the MR-approach was calculated relative to the lymphoscintigraphy gold standard.

RESULTS

There was substantial correlation of results by the two modalities (κ = 0.62). MR-lymphangiography had sensitivity of 68%, specificity of 91%, positive predictive value of 82%, and negative predictive value of 83%.

CONCLUSIONS

Imaging findings of both lymphoscintigraphy and MR-lymphangiography showed good diagnostic accuracy. MR-lymphangiography proved more information about anatomic location of focal lesions of the lymphatic vessels, but use of MR-lymphangiography is currently constrained due to the requirement for off-label subcutaneous injection of gadolinium chelates. Consequently, and due to its superior sensitivity lymphoscintigraphy remains the most common imaging method to assess functional lymphatic disorders of the lower limb.

Imaging lymphatic system in breast cancer patients with magnetic resonance lymphangiography

Objective

To investigate the feasibility of gadolinium (Gd) contrast-enhanced magnetic resonance lymphangiography (MRL) in breast cancer patients within a typical clinical setting, and to establish a Gd-MRL protocol and identify potential MRL biomarkers for differentiating metastatic from non-metastatic lymph nodes.

Materials and Methods

32 patients with unilateral breast cancer were enrolled and divided into 4 groups of 8 patients. Groups I, II, and III received 1.0, 0.5, and 0.3 ml of intradermal contrast; group IV received two 0.5 ml doses of intradermal contrast. MRL images were acquired on a 3.0 T system and evaluated independently by two radiologists for the number and size of enhancing lymph nodes, lymph node contrast uptake kinetics, lymph vessel size, and contrast enhancement patterns within lymph nodes.

Results

Group III patients had a statistically significant decrease in the total number of enhancing axillary lymph nodes and lymphatic vessels compared to all other groups. While group IV patients had a statistically significant faster time to reach the maximum peak enhancement over group I and II (by 3 minutes), there was no other statistically significant difference between imaging results between groups I, II, and IV. 27 out of 128 lymphatic vessels (21%) showed dilatation, and all patients with dilated lymphatic vessels were pathologically proven to have metastases. Using the pattern of enhancement defects as the sole criterion for identifying metastatic lymph nodes during Gd-MRL interpretation, and using histopathology as the gold standard, the sensitivity and specificity were estimated to be 86% and 95%, respectively.

Conclusion

Gd-MRL can adequately depict the lymphatic system, can define sentinel lymph nodes, and has the potential to differentiate between metastatic and non-metastatic lymph nodes in breast cancer patients.

MR lymphangiography at 3.0 T: correlation with lymphoscintigraphy

PURPOSE

To prospectively compare findings of magnetic resonance (MR) lymphangiography with those of lymphoscintigraphy, evaluate the pattern and delay of lymphatic drainage, compare typical findings, and investigate discrepancies between the techniques.

MATERIALS AND METHODS

This prospective study was performed according to the Declaration of Helsinki and was approved by the local ethics committee. Thirty consecutive patients with uni- or bilateral lymphedema and lymph vessel transplants of the lower extremities were examined with 3.0-T fat-saturated three-dimensional gradient-echo MR after gadopentetate dimeglumine injection. Results of all examinations were correlated with corresponding results of lymphoscintigraphy examinations. Results of both techniques were separately reviewed in consensus by a radiologist and a nuclear physician, who rated delay and pattern of drainage, number of enhancing levels, and quality of conspicuity of the depiction of lymph nodes and lymph vessels. Sensitivity and specificity were calculated by using combined results of both techniques and clinical presentation findings as reference standard. Correlation was calculated with weighted k coefficients.

RESULTS

Weak lymphatic drainage at lymphoscintigraphy correlated with lymphangiectasia at MR lymphangiography (13 of 33 affected extremities). Lymph vessels were clearly visualized with MR lymphangiography (five of 24 affected extremities), while they were not detectable with lymphoscintigraphy. Depiction of inguinal lymph nodes was clearer with lymphoscintigraphy (five of 60 extremities). Correlation of both techniques was excellent for delay (κ=0.93) and pattern (κ=0.84) of drainage, good for depiction of lymph nodes (κ=0.67) and number of enhancing levels (κ=0.77), and moderate for depiction of lymph vessels (κ=0.50). Sensitivity and specificity for delay and pattern of drainage were concordant, whereas MR lymphangiography showed a higher sensitivity for lymph vessel abnormalities (100% vs 79%) and lower specificity for lymph node abnormalities (78% vs 100%).

CONCLUSION

Imaging findings of MR lymphangiography and lymphoscintigraphy show a clear concordance. With lymphoscintigraphy, better visualization of inguinal lymph nodes was achieved, whereas with MR lymphangiography, better depiction of lymph vessels and morphologic features of lymph vessel abnormalities were achieved.

Extracellular gadolinium-based contrast media: an overview

Increasing use is made of extracellular MRI contrast agents that alter the image contrast following intravenous administration; they predominantly shorten the T1 relaxation time of tissues. The degree and location of these changes provide substantial diagnostic information. However gadolinium-based contrast agents (Gd-CA) are not inert drugs. They may cause acute non-renal adverse reactions (e.g. anaphylactoid reactions), acute renal adverse reactions (e.g. contrast induced nephropathy), delayed adverse reactions (nephrogenic systemic fibrosis) and problems at the site of injection (e.g. local necrosis). This review describes the current status of Gd-CA, their mechanism of action, chemical structure, pharmacokinetics, dosage, elimination, nephrotoxicity and adverse events.

Efficiency, thermodynamic and kinetic stability of marketed gadolinium chelates and their possible clinical consequences: a critical review

Gadolinium-based contrast agents are widely used to enhance image contrast in magnetic resonance imaging (MRI) procedures. Over recent years, there has been a renewed interest in the physicochemical properties of gadolinium chelates used as contrast agents for MRI procedures, as it has been suggested that dechelation of these molecules could be involved in the mechanism of a recently described disease, namely nephrogenic systemic fibrosis (NSF). The aim of this paper is to discuss the structure-physicochemical properties relationships of marketed gadolinium chelates in regards to their biological consequences. Marketed gadolinium chelates can be classified according to key molecular design parameters: (a) nature of the chelating moiety: macrocyclic molecules in which Gd3+ is caged in the pre-organized cavity of the ligand, or linear open-chain molecules, (b) ionicity: the ionicity of the complex varies from neutral to tri-anionic agents, and (c) the presence or absence of an aromatic lipophilic residue responsible for protein binding. All these molecular characteristics have a profound impact on the physicochemical characteristics of the pharmaceutical solution such as osmolality, viscosity but also on their efficiency in relaxing water protons (relaxivity) and their biodistribution. These key molecular parameters can also explain why gadolinium chelates differ in terms of their thermodynamic stability constants and kinetic stability, as demonstrated by numerous in vitro and in vivo studies, resulting in various formulations of pharmaceutical solutions of marketed contrast agents. The concept of kinetic and thermodynamic stability is critically discussed as it remains a somewhat controversial topic, especially in predicting the amount of free gadolinium which may result from dechelation of chelates in physiological or pathological situations. A high kinetic stability provided by the macrocyclic structure combined with a high thermodynamic stability (reinforced by ionicity for macrocyclic chelates) will minimize the amount of free gadolinium released in tissue parenchymas.

Interstitial MR lymphangiography - a diagnostic imaging method for the evaluation of patients with clinically advanced stages of lymphedema

BACKGROUND

To assess the feasibility of interstitial magnetic resonance lymphangiography with intracutaneous injection of a commercially available, non-ionic, extracellular paramagnetic contrast agent, to visualize lymphatic vessels in patients with clinically advanced stages of primary lymphedema.

METHODS

Sixteen lower extremities in 8 patients with clinically advanced stages of primary lymphedema were examined with magnetic resonance lymphangiography. A 18 mL of gadodiamide and 2 mL of mepivacainhydrochloride 1% were subdivided into 10 portions and injected intracutaneously into the dorsal aspect of both feet. For MRL, a 3D spoiled gradient-echo sequence (Volumetric Interpolated Breathold Examination, VIBE) was performed.

RESULTS

The beaded appearance of lymphatic vessels extending from the injection site was detected in all 16 lower extremities (100%). In 10 lower extremities (63%), lymphatic vessels of the upper leg could be visualized. A contrast enhancement was observed in 10/16 inguinal lymph node groups (63%). In 12 lower extremities (75%) collateral vessels with dermal back-flow areas between lymphatic vessels were seen.

CONCLUSION

Magnetic resonance lymphangiography is safe, technically feasible, and assists the clinician in the therapeutic planning of patients with clinically advanced stages of primary lymphedema by imaging the pathologically modified lymphatic vessels and accompanying complications non-invasively.

Gadoteridol for MR imaging of lymphatic vessels in lymphoedematous patients: initial experience after intracutaneous injection

The aim of this study was to evaluate the feasibility of gadoteridol in visualizing lymphatic vessels of lymphoedematous patients after intracutaneous injection. 20 lower extremities in 10 lymphoedematous patients were examined. Gadoteridol (9 ml) was subdivided into five portions and injected intracutaneously into the dorsal aspect of each foot. For MRI, a three-dimensional spoiled gradient echo sequence was performed. No complications were observed during or after intracutaneous injection of gadoteridol. The lymphoedema was bilateral in seven and unilateral in three of the examined patients. Contrast enhancement of gadoteridol was detected in lymphatic vessels at the level of the lower leg in 17 lower extremities (85%). Enhancing lymphatic vessels of the upper leg were observed in 11 lower extremities (55%). Furthermore, gadoteridol enhanced 10 out of 20 inguinal lymph node groups (50%). No external iliac lymph nodes were observed in any of the patients. Regions of dermal backflow, indicating proximal lymphatic obstruction, were seen in 13 lower extremities (65%). As soon as 15 min after gadoteridol injection, accompanying venous enhancement was detected in all lower extremities (100%). MRI of lymphatic vessels in lymphoedematous patients is safe and feasible after intracutaneous injection of gadoteridol if the diagnosis of lymphoedema necessitates a better definition for optimal therapeutic planning or an objective, diagnostic baseline is required. The proposed technique represents a minimally invasive imaging method of identifying anatomical and physiological derangements in lymphatic vessels.

Magnetic resonance imaging of lymphatic vessels without image subtraction: a practicable imaging method for routine clinical practice?

OBJECTIVE

To assess the feasibility of a time-efficient, high-resolution magnetic resonance lymphangiography (HR MRL) protocol without image subtraction for the detection of lymphatic vessels in patients with primary and secondary lymphedema.

METHODS

Three consecutive patients with lymphedema of the lower extremities (2 primary bilateral, 1 secondary unilateral) underwent HR MRL without image subtraction. An amount of 9 mL of gadodiamide and 1 mL of mepivacaine hydrochloride 1% were subdivided into 5 portions and injected intracutaneously into the dorsal aspect of each foot outside the scanner before image acquisition. Magnetic resonance imaging was performed with a 1.5-T system equipped with high-performance gradients. For HR MRL, a 3-dimensional, spoiled gradient-echo sequence (Volumetric Interpolated Breath-hold Examination) was used. The extent and distribution of the lymphedema was evaluated using a heavily T2-weighted, 3-dimensional turbo-spin echo sequence.

RESULTS

The HR MRL bilaterally detected the inguinal lymph nodes and the lymphatic vessels in the lower and upper leg in the 2 patients with primary lymphedema. In the patient with left-sided secondary lymphedema, the inguinal lymph nodes and the lymphatic vessels in the lower and upper leg were depicted on the right side. The diameter of the displayed lymphatic vessels varied between 1 and 5 mm. Three-dimensional, maximum-intensity projection images of different angles of view provided detailed outlining of the lymphatic vessels and differentiation from veins, which showed a lower signal intensity.

CONCLUSION

The HR MRL without image subtraction is safe, technically feasible, and has the potential to become a diagnostic imaging tool in daily clinical practice because of its time efficiency.

High-resolution MR lymphangiography in patients with primary and secondary lymphedema

OBJECTIVE

The objective of our study was to evaluate the feasibility of high-resolution MR lymphangiography with intracutaneous injection of gadodiamide, a commercially available, nonionic, extracellular paramagnetic contrast agent, for the visualization of lymphatic vessels in patients with primary and secondary lymphedema.

CONCLUSION

High-resolution MR lymphangiography is safe, is technically feasible, and has the potential to become a diagnostic imaging tool for patients with lymphedema.

Assessment of Utilization and Pharmacovigilance Based on Spontaneous Adverse Event Reporting of Gadopentetate Dimeglumine as a Magnetic Resonance Contrast Agent After 45 Million Administrations and 15 Years of Clinical Use

PURPOSE

Although contrast agents have become indispensable tools in magnetic resonance and their safe and effective use the foundation of many essential diagnostic procedures, only limited summary information on their utilization and pharmacovigilance is available to the community. After voluntary access to the manufacturer spontaneous adverse event database, we assessed the available data for gadopentetate dimeglumine.

MATERIAL AND METHODS

Gadopentetate dimeglumine (Gd-DTPA, Magnevist; Berlex/Schering AG, Berlin, Germany) became commercially available in 1988 and is currently marketed in 101 countries. Using the manufacturer's continuous and cumulative database on product distribution and spontaneous adverse event (AE) reporting, we categorized AEs and assessed their cumulative occurrence after 10, 20, and 45 million applications that occurred in 1993, 1997, and 2002, respectively. Furthermore, we reviewed publications in Medline to assess prevalence of the 4 most common MR contrast agents in the indexed literature.

RESULTS

Gd-DTPA has been used in more than 45 million magnetic resonance imaging procedures since 1988 and is currently used globally in more than 5 million applications annually. The broadest category of spontaneously reported AEs, subjective symptoms, occurs in less than 0.01% of procedures. Within the total AEs reported, the distribution of serious and nonserious reports was 9.3% and 90.7%, respectively. The rates of AE reporting have changed over time, with increased rates in the second reporting period (1993 to 1997), followed by substantially lower rates in subsequent years. AE reporting rates are the most comprehensive data available; however, there will always be some underestimation of the true event rates. Although no substantial differences were noted among major age groups, substantial differences in reporting frequency were found among regions, with the United States reporting nearly twice as many AEs as Europe in the postmarketing phase.

CONCLUSION

The postmarketing utilization and pharmacovigilance analysis of Gd-DTPA has revealed temporal changes and regional differences, overall with an excellent safety profile. Its extensive utilization and safety information have firmly established it as highly used and safe magnetic resonance imaging agent.

Postoperative Lymphoceles: Detection with High-resolution MR Lymphangiography

Lymphoceles that do not resolve spontaneously or with treatment may be a major problem associated with a high degree of morbidity. Several imaging studies, including ultrasonography, computed tomography, magnetic resonance (MR) imaging, lymphography, lymphoscintigraphy, and intraoperative lymphatic mapping have been proposed to delineate lymphoceles before treatment. The present report describes the successful detection of three lymphoceles of the inguinal region with leaking lymphatic vessels by means of high-resolution MR lymphangiography.

Indirect magnetic resonance lymphangiography in patients with lymphedema preliminary results in humans

PURPOSE

To assess the feasibility of indirect magnetic resonance (MR) lymphangiography with intracutaneous injection of gadodiamide, a commercially available, non-ionic, extracellular paramagnetic contrast agent for the detection of lymphatic vessels in patients with lymphedema.

MATERIALS AND METHODS

In 2005, three patients with lymphedema of the lower extremities (1 primary, 2 secondary) were referred by the Foeldi Clinic for Lymphology for indirect magnetic resonance lymphangiography. 4.5 mL of gadodiamide and 0.5 mL of mepivacainhydrochloride 1% were injected intracutaneously into the dorsal aspect of each foot. MR imaging was performed with a 1.5-T system equipped with high-performance gradients. For indirect magnetic resonance lymphangiography, a 3D Fast Low Angle Shot (FLASH) sequence (TR/TE: 5.1/1.23; flip angle: 25; matrix: 448 x 448; bandwidth: 330 Hz/pixel; 6/8 rectangular field of view with a maximum dimension of 500 mm; slices: 88; voxel size: 2.0 mm x 1.0 mm x 1.0mm; acquisition time: 0 min 31 s) was used.

RESULTS

Indirect magnetic resonance lymphangiography depicted lymphatic vessels of the lower and upper leg, and inguinal lymph nodes in all three patients. After 5 min of contrast material application, concomitant venous enhancement was detected. Collateral vessels with dermal back-flow were seen in two patients. A lymphocele in the inguinal region with the afferent lymphatic vessel was depicted in one patient.

CONCLUSION

In the presented small study group, indirect magnetic resonance lymphangiography was technically feasible, and no complications were observed after intracutaneous injection of gadodiamide. Visualizing the lymphatic vessels and accompanying complications non-invasively and without the use of radiation, the presented method has the capability to become a routine diagnostic imaging tool in patients with primary and secondary lymphedema. The method is not able to characterize lymph node morphology, but could provide additional information about the lymphatic vessels when lymph nodes are examined, e.g. with super-paramagnetic iron oxide particles.

Currently used non-specific extracellular MR contrast media

Magnetic resonance contrast agents have demonstrated their clinical usefulness in a variety of organs for improved detection of various neoplastic, inflammatory and functional abnormalities. Gadolinium chelates are the most widely used. They are extracellular, non-specific contrast agents. Their use in many clinical indications is justified because, in conjunction with improved imaging techniques, these safe and image-enhancing contrast agents add morphologic and functional information compared with unenhanced MR images. This article describes the commercially available compounds, and summarizes their approval status on the international market regarding indications and doses. Their mechanisms of action, biodistributions, toxicities and tolerance profiles in normal and high-risk patient populations are described. Additionally, this article reviews the specific recommendations by the manufacturers for patients at risk. Finally, their main clinical applications are reviewed.

Assessment of normal, inflammatory, and tumor-bearing lymph nodes with contrast-enhanced interstitial magnetic resonance lymphography: preliminary results in rabbits

PURPOSE

To assess different gadolinium (Gd)-based contrast agents for interstitial magnetic resonance (MR) lymphography in normal, inflammatory, and tumor-bearing lymph nodes in rabbits.

MATERIALS AND METHODS

Three paramagnetic contrast agents were assessed: a standard extracellular 0.5 M Gd-chelate, gadoterate meglumine (Gd-DOTA), and two macromolecular agents, P792 and P760 (all Guerbet, Aulnay-sous-Bois, France). A volume of 0.5 mL of each agent were injected subcutaneously into the dorsal footpads of six rabbits (three groups, 18 rabbits). Imaging was performed prior to as well as two weeks following induction of either reactive (complete Freund adjuvant) or tumorous (VX2 tumor) lymph nodes. T1-weighted three-dimensional gradient-echo and maximum intensity projection (MIP) images were obtained up to 120 minutes as well as 24 hours after administration of the different compounds. Signal-to-noise ratios (SNRs) of enhancing lymph nodes were calculated. The different compounds were compared regarding nodal enhancement over time, depiction of regional nodes, and lymphatic vessels. Furthermore, enhancement patterns were compared between normal, inflammatory, and metastasized nodes.

RESULTS

Inguinal and iliac lymph nodes and lymph vessels revealed enhancement following interstitial injection of all evaluated compounds. For all agents, inflammatory lymph nodes revealed no significantly different SNRs compared to normal nodes (P > 0.2), whereas tumorous nodes showed signal voids and significantly lower SNRs (P < 0.05). Compared to P760 and P792, depiction of tumor-bearing nodes with Gd-DOTA was less reliable.

CONCLUSION

Interstitial MR lymphography with P760 and P792 allows differentiation of tumor-bearing lymph nodes from reactive inflammatory and normal nodes based on a contrast uptake pattern assessed qualitatively as well as quantitatively.

Local tissue toxicity in response to extravascular extravasation of magnetic resonance contrast media

RATIONALE AND OBJECTIVES

The relative toxicities of the gadolinium chelates currently available in the United States were compared when extravasated in soft tissue. The increasing use of these contrast agents in higher volumes and at faster injection rates, often with a power injector, was a principal motivation for this research.

METHODS

Gadopentetate dimeglumine (Magnevist), gadoteridol (ProHance), gadodiamide (Omniscan), and gadoversetamide (Optimark) were evaluated at standard concentration and compared with a control (physiologic saline) and the conventional ionic radiographic contrast medium meglumine diatrizoate (Renografin 60). Each mouse received a subcutaneous injection in the hindlimb of 0.3 mL of contrast or saline. There were 6 experimental groups, with 15 animals in each group. The individual performing the injection was blinded to the identity of the contrast agent used in each mouse. After 48 hours, the mice were killed and tissue samples obtained for histopathology. A veterinary pathologist, also blinded to the agent injected, graded the degree of damage seen on microscopic examination.

RESULTS

Of the four MR contrast agents, gadopentetate dimeglumine caused the greatest tissue damage, and gadoteridol and gadodiamide-the two lowest osmolar agents-the least. The difference was statistically significant in terms of both inflammation (P = 0.0008 for gadoteridol, and P = 0.006 for gadodiamide) and necrosis (P = 0.0067 for gadoteridol, and P = 0.031 for gadodiamide), when these agents were compared with gadopentetate dimeglumine. In regard to the control experiments, for all three variables (necrosis, edema, and inflammation), there was no statistically significant difference between the results with gadoteridol or gadodiamide and those with saline. In terms of both edema and inflammation, the effect of gadopentetate dimeglumine, although less, could not be differentiated with any statistical significance from that of meglumine diatrizoate. Gadoversetamide, which has an osmolality between the ionic agent (gadopentetate dimeglumine) and the other two nonionic agents, caused a reaction that could not be differentiated from that seen with gadopentetate dimeglumine for both necrosis and edema. Only in the scoring of inflammation was the effect less using gadoversetamide compared to gadopentetate dimeglumine with any statistical significance (P = 0.021).

CONCLUSIONS

The risk of tissue damage due to extravasation is not widely appreciated for the gadolinium chelates. Care should be exercised during contrast injection, to avoid inadvertent extravasation and its deleterious consequences, in particular with the two higher osmolar agents (gadopentetate dimeglumine and gadoversetamide).

Safety issues in magnetic resonance imaging

Although generally considered safe, magnetic resonance imaging (MRI) has a number of safety issues, including the effects of high magnetic fields and radiofrequency pulses on the body, and on implanted devices, the side effects of contrast agents, toxicity during pregnancy, claustrophobia, and hearing loss.

Interstitial MR lymphography with gadoterate meglumine: initial experience in humans

Magnetic resonance (MR) lymphography was performed in five healthy volunteers and three patients (two adults and one infant). Subcutaneous administration of gadoterate meglumine in the foot allowed visualization of draining lymph vessels and nodes. In one patient, an inguinal fluid collection could be characterized as a lymphocele. In the infant, a chylothorax was diagnosed. The authors conclude that interstitial MR lymphography with commercially available compounds is feasible.

Interstitial MR lymphography with a conventional extracellular gadolinium-based agent: assessment in rabbits

PURPOSE

To evaluate gadoterate meglumine as a contrast agent for interstitial magnetic resonance (MR) lymphography in combination with an adapted fast three-dimensional (3D) MR sequence.

MATERIALS AND METHODS

In 12 New Zealand White rabbits, 0.5 mL of undiluted gadoterate meglumine was injected subcutaneously into the dorsal foot pad (n = 9) or the foreleg (n = 3) bilaterally. Immediately after administration, a slight massage was performed at the injection site. Imaging was performed with a 3D spoiled gradient-recalled echo sequence (6.7/1.6 [repetition time msec/echo time msec]; field of view, 28.0 x 19.6; two signals acquired) similar to that used for 3D MR angiography. Thus, 3D maximum intensity projection images could be obtained. Images were obtained before injection and 5, 15, 30, 60, and 120 minutes after injection.

RESULTS

In the hind legs, as many as four successive lymph node groups were depicted with maximum enhancement after 5-15 minutes for the popliteal lymph node group, 15-30 minutes for the inguinal lymph group, and 30-60 minutes for the iliac-paraaortal lymph node group; the iliac-paraaortal lymph node group was not consistently enhanced. In the forelegs, four successive lymph node groups, including axillary and mediastinal lymph node groups, showed marked gadolinium uptake, with maximum enhancement 5-15 minutes after injection.

CONCLUSION

As a widely tested positive-enhancing T1 contrast agent with favorable safety features, gadoterate meglumine allows the depiction of three to four successive lymph node groups early after subcutaneous injection. With the sequence used, 3D MR lymphangiograms can be obtained.

Safety of approved MR contrast media for intravenous injection

In the last 10 years, the use of intravenous contrast media in magnetic resonance (MR) has become well-established clinical practice. Contrast media provide critical additional diagnostic information in many instances. The gadolinium chelates constitute the largest group of MR contrast media and are considered to be very safe. These agents are thought to be safer than nonionic iodinated contrast agents. Unlike x-ray agents, the gadolinium chelates are not nephrotoxic. Minor adverse reactions, including nausea (1%-2% for all agents) and hives (<1% for all agents), occur in a very low percent of cases. Health care personnel should be aware of the (extremely uncommon) potential for severe anaphylactoid reactions in association with the use of MR contrast media and be prepared should complications arise. The four gadolinium chelates currently available worldwide, gadopentetate dimeglumine, gadoteridol, gadodiamide, and gadoterate meglumine, cannot be differentiated on the basis of adverse reactions. Far fewer patients have been examined to date with the two other agents that have widespread approval, mangafodipir trisodium and ferumoxides. These latter two agents are considered to be very safe but have a higher percentage of associated adverse reactions (7%-17% with mangafodipir trisodium and 15% with ferumoxides). This review discusses the safety issues involved with administration of intravenous contrast media in MR imaging, focusing on the six agents (four gadolinium chelates, one manganese chelate, and the last a large iron particle) with widespread use world-wide.

Sequential fast 3D MRI following oral ingestion of Gd-DOTA: A new means to assess intestinal transit time

A magnetic resonance image (MRI)-based method to determine the colonic transit time is described. It is based on the oral ingestion of a single dose of 4 ml Gd-DOTA following an overnight fast and the subsequent acquisition of fast three-dimensional (3D) gradient-echo sequences under apnea conditions. The technique was successfully evaluated in three healthy volunteers. Transit of the contrast agent through the small and large intestines was easily followed. Thus, MRI-based colonic transit time determinations are feasible.

Safety of magnetic resonance imaging contrast agents

Many of the MR examinations performed in the world each year are accompanied by administration of one of these frequently used intravenous contrast agents: Magnevist, Omniscan, and ProHance. Accordingly, MR practitioners must understand the basic pharmacokinetics, side effects, and the potential for adverse events for these contrast agents. Additionally, MR practitioners must know how to manage side effects and adverse events that may occur in association with the administration of contrast agents. Notably, the use of MR imaging contrast agents in special patient populations must be understood. This article discusses each of these important issues.

Multinuclear magnetic resonance characterization of paramagnetic contrast agents. The manifold effects of concentration and counterions

RATIONALE AND OBJECTIVES

Proper fitting of the nuclear magnetic resonance dispersion (NMRD) profiles to the numerous factors governing nuclear relaxation in paramagnetic systems requires knowledge of some parameters usually obtained by other techniques. The rotational correlation time (tau R) for example can be measured by carbon-13, hydrogen-2, or oxygen-17 NMR. Discrepancies between values reported in the literature might be attributed to the different concentration ranges used so far in these modalities. In the present work focussing on commercial nonspecific contrast agents, the influence of the solution composition (type and concentration of the complexes and of the counterions) has been examined with regard to the water proton relaxation enhancement and molecular dynamics.

METHODS

The proton relaxation rate enhancement of Magnevist, Dotarem, Omniscan, and ProHance was measured in aqueous solution up to a concentration of 0.5 M. In the same concentration window, the rotational correlation times were obtained from the study of deuterium relaxation rates of the diamagnetic deuterated analogs (lanthanum complexes) of the gadolinium chelates.

RESULTS

Above 50 mM, the relaxation rate enhancement versus concentrations strongly deviates from linearity. Magnevist, a clinical formulation containing two meglumine counterions per molecule of paramagnetic complex, exhibits the largest concentration effect. A slowing down of the molecular dynamics accounts for this behavior as confirmed by the analysis of the rotational correlation times obtained by deuterium relaxometry. At low concentrations (< or = 50 mM), tau R values obtained by proton NMRD analysis and by deuterium relaxation are in very good agreement.

CONCLUSIONS

This study shows that NMR analyses of small molecular weight complexes should be carried out on solutions containing no more than 50 mM to avoid the biaising effects of concentration. On the other hand, the benefitting relaxivity enhancement induced by highly concentrated solutions has to be taken into account in the context of bolus injection or vesicular entrapment.

Preliminary assessment of three-dimensional magnetic resonance imaging for various colonic disorders

BACKGROUND

Improvements in magnetic resonance imaging (MRI) technology have enabled the acquisition of three-dimensional MRI datasets in a single breath hold. We adopted this technique to make a three dimensional intraluminal and extraluminal assessment of the colon in three patients with various colonic disorders.

METHODS

One patient was studied after having a double-contrast barium enema. Two patients had MRI scans after colonoscopy, which showed three colonic tumours in one and multiple polyps in the ascending colon of the other. The process of rectal filling with 1.5-2.0 L water mixed with 15-20 mL 0.5 mol/L gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) was monitored with MR fluoroscopic sequence. Three-dimensional datasets of the contrast-filled colon were taken with patients in prone (before and after intravenous administration of 0.1 mmol/kg bodyweight Gd-DTPA) and supine positions. 64 sections with a voxel-resolution of 2.0 x 2.0 x 1.25 mm3-were taken during a 28 s breath hold. Three-dimensional maximum intensity projection, multiplanar reconstruction, and virtual colonoscopic images of the colon were created from these.

FINDINGS

Analysis of the coronal source images in conjunction with multiplanar reconstructions revealed all relevant abnormalities, including diverticula, carcinomas, and polyps. Three dimensional maximum-intensity projections gave a morphological overview of the whole colon. Targeted projections, made up of a limited number of coronal source images, showed diverticula and smaller polyps more clearly. After patients were given intravenous contrast all colonic mass lesions were enhanced. Datasets obtained in prone patients gave the best intraluminal views of the colon. Virtual magnetic resonance colonoscopy showed colonic haustra as well as the ileocaecal valve, but did not show clearly the diverticula. All intraluminal mass lesions, on the other hand, were easy to see.

INTERPRETATION

The potential of three-dimensional colonic MRI to provide accurate, minimally invasive, cost-effective polyp screening, as well as comprehensive colonic tumour staging, warrants further investigation.

Pre-clinical evaluation of gadobutrol: a new, neutral, extracellular contrast agent for magnetic resonance imaging

The Gd(3+)-complex of 10-(2,3-dihydroxy-1-hydroxymethylpropyl)-1,4,7,10-tetraazacyclo dodecane-1,4,7-triacetic acid(gadobutrol) is a new, neutral Gd-chelate for use as an extracellular contrast agent in magnetic resonance imaging (MRI). The blood level in dogs after intravenous (i.v.) injection decreased with a terminal half-life of about 45 min, the clearance was about 3.75 ml/min per kg and the distribution volume of 0.23 l/kg suggested an extracellular distribution. Biodistribution experiments in rats revealed that only a very small amount (0.16%) of the dose was left in the body 7 days after i.v. injection. Measurable amounts of Gd could be detected only in the liver, kidneys and bones. The osmolality (0.57 osmol/kg at 0.5 mol/l and 1.39 osmol/kg at 1 mol/l) is in the range of other low osmolality contrast media for MRI. Only very little interaction with biologically relevant molecules was suggested by a histamine release test and a lysozyme inhibition test. An i.v.-LD50 of 23 mmol/kg in mice combined with a comparatively high T1-relaxivity (5.6 l/mmol per s at 0.47 T and 6.1 l/mmol per s at 2 T) in plasma promises a high margin of safety. In preliminary imaging experiments, gadobutrol caused high enhancement in different lesions (cerebral infarct, brain tumor) of the rat. Tripling of the typical clinical dose of 0.1 mmol/kg was shown to provide additional diagnostic gain in lesions of this type.

Urine profiles and kidney histology after ionic and nonionic radiologic and magnetic resonance contrast media in rats with cisplatin nephropathy

RATIONALE AND OBJECTIVES

The nephrotoxic drug cisplatin has been used successfully in treating some cancers. Patients with suspected carcinoma frequently undergo examinations with contrast media. We examined whether ionic and nonionic radiologic and magnetic resonance contrast media would have any effect on cisplatin nephropathy in rats.

METHODS

Urine and serum profiles were monitored for 24 days after intravenous (i.v.) injections of saline, diatrizoate, iohexol, gadopentetate dimeglumine, and gadodiamide in high doses (4.59 mmol/kg body weight) in rats that received a weekly intraperitoneal (i.p.) injection of cisplatin (1 mg/kg) for 10 weeks. There were 10 rats in each group. Another 10 rats injected with both i.p. and i.v. saline served as control subjects. After euthanization, rats' kidneys were removed for examination by light microscopy and electron microscopy.

RESULTS

Light and electron microscopy showed severe morphologic changes, including tubular dilatation, atrophy, and necrosis induced by cisplatin; however, the contrast media did not induce any additional morphologic changes. Gadopentetate dimeglumine, diatrizoate, and iohexol significantly increased (3-20 times) albuminuria compared with i.v. saline in cisplatin nephropathy, whereas gadodiamide did not. Albuminuria was highest after diatrizoate injection. All four contrast media caused an immediate and transient significant increase in the excretion of the brush border enzymes alkaline phosphatase and gamma-glutamyltransferase (125-500 times) and the cytoplasmatic enzymes alanine aminopeptidase and lactate dehydrogenase (16-100 times). Compared with saline, the ionic agents significantly increased the excretion of both glucose (two times) and sodium (three to five times), whereas the nonionic agents did not.

CONCLUSION

High doses of radiologic and magnetic resonance contrast agents cause temporary dysfunction in rats with cisplatin nephropathy. Gadodiamide caused the least dysfunction and diatrizoate the most.

Invited review: biophysical properties and clinical applications of magnetic resonance imaging contrast agents

Contrast enhanced magnetic resonance imaging (MRI) is a very versatile and effective technique for detecting and characterizing lesions, for identifying a variety of patho-physiological abnormalities, and for providing perfusion and functional information. The application of contrast enhanced MRI to many clinical and research indications has emerged because of the rapid evolution in imaging techniques, improved methodology, and the development of efficient and specific contrast agents. Problems related to optimizing parameters and dosage have been due to complex interplay of relaxation times, biophysical mechanisms and acquisition parameters. A knowledge of basic biophysical aspects is therefore essential for a full understanding of the results obtained for different organs under different conditions, and for optimizing the image parameters and dosage of contrast agents. This article underlines the biophysical basis of the effects of contrast agents in MRI, identifies the problems involved in optimizing the parameters for maximum efficiency, and presents a general overview of the clinical studies and research applications in the central nervous system, perfusion abnormalities, hepatobiliary system, musculoskeletal system and the gastrointestinal tract. The section on perfusion studies includes a discussion of quantitative analysis and kinetic models describing the effects of contrast agents. Finally, a critical evaluation of the scope and limitations of contrast enhanced MRI is presented.

Safety of gadoteridol injection: U.S. clinical trial experience

As part of the clinical evaluation of gadoteridol injection, intravenous doses ranging from 0.05 to 0.3 mmol/kg were administered to 1,709 patients and volunteers. Safety monitoring included pre- and postdose physical examinations, vital signs, and clinical laboratory values. Adverse event recording included occurrence, duration, severity, relationship to injection, and clinical importance. No clinically important changes in physical examination results, electrocardiograms, or vital signs were attributed to gadoteridol injection except for one case of hypotension. Four clinically important changes in laboratory values possibly or definitely related to the contrast agent were noted in two patients (0.1%). Adverse events were recorded in 118 subjects (6.9%), including nausea in 24 subjects (1.4%) and taste perversion in 22 subjects (1.3%). All other adverse events occurred with a frequency of less than 1%. Adverse events related to contrast agent administration occurred in 79 subjects (4.6%). Gadoteridol injection demonstrated excellent clinical safety and patient tolerance at various doses and injection rates.

Improved cine MR imaging of left ventricular wall motion with gadopentetate dimeglumine

The assessment of left ventricular wall motion with cine magnetic resonance imaging in the cardiac long axes is useful; however, image quality is limited by reduced signal intensity due to saturation of blood flowing predominantly in plane. Twenty subjects were studied to evaluate the effects of gadopentetate dimeglumine on contrast between blood and myocardium. Contrast improved significantly on contrast agent-enhanced images in the long axes, at both end-systole (vertical axis, +62%, P < .0001; horizontal axis, +67%, P < .0001) and end-diastole (vertical axis, +50%, P < .0001; horizontal axis, +26%, P < .004). The increase in the short axis was less and significant only at end-systole (+25%, P < .0001). Subjective scoring of the cines also showed a significant and clinically useful improvement in the long axes (P < .0001 for both) on contrast-enhanced images. Improved contrast was most evident for 10 minutes after injection, but persisted for up to 20 minutes at end-systole in the long axes. Gadopentetate dimeglumine is useful for cine imaging of left ventricular wall motion when saturation effects prevent adequate clinical assessment.

Phase III clinical evaluation of gadoteridol injection: experience in pediatric neuro-oncologic MR imaging

Twenty-two pediatric patients with known CNS neoplasms underwent magnetic resonance (MR) imaging before and after intravenous injection of 0.1 mmol/kg gadoteridol injection as part of a Phase IIIB open label multicenter clinical trial. Intravenous administration of this neutral, nonionic contrast agent was found to be safe in children. No clinically relevant changes in vital signs or laboratory values (including complete blood count, blood chemistry, serum electrolytes, thyroid and metabolic panel and clotting function) were attributed to the administration of gadoteridol injection. There were no systemic complaints. The imaging characteristics of gadoteridol in pediatric CNS disease appeared similar to those of gadopentetate dimeglumine. Contrast enhancement was present in 17 of 22 patients (77%). The administration of gadoteridol injection provided additional clinically relevant information including improved visualization and delineation of the primary lesion, detection of additional lesions, determination of tumor recurrence and narrowing the list of differential considerations in all 17 enhancing studies as well as in 2 of 5 studies without signal intensity enhancement. The very low toxicity, inherent to this nonionic low osmolal paramagnetic contrast formulation may allow administration of increased doses at increased infusion rates for an increased number of indications with improved sensitivity.