Nephrotoxicity of high-dose gadolinium compared with iodinated contrast

Multistation Whole-Body High-Spatial-Resolution MR Angiography Using a 32-Channel MR System

OBJECTIVE

The objective of our study was to investigate a multistation whole-body MR angiography (MRA) protocol using a 32-channel MR system with multicoil technology in a population of patients with suspected peripheral vascular disease (PVD).

SUBJECTS AND METHODS

Fifty consecutive patients with suspected PVD (31 men, 19 women; age range, 46-91 years) underwent multistation whole-body contrast-enhanced MR angiography (CE-MRA) on a 32-channel 1.5-T MR system equipped with multicoil technology. A two-step contrast injection protocol was used: After the first injection, images of the most proximal station (station I, head and neck) were acquired, followed by the most distal station (station IV, calves). Images of the intermediate two stations (station II, chest and abdomen; station III, pelvis and thighs) were acquired during the second injection. Conventional catheter angiography was performed for symptomatic vascular regions in 30 patients. The image quality of the arterial segments and the presence and degree of the arterial stenosis were evaluated by two radiologists. The interobserver variability was calculated by kappa statistics, and comparative analysis between CE-MRA and catheter angiography was performed by means of the Spearman's rank correlation coefficient.

RESULTS

Most of the vascular segments (1,912/1,976 [97%]) were visualized on wholebody CE-MRA with diagnostic image quality. Significant arterial disease (> or = 50%) was detected in 167 (observer 1) and 177 (observer 2) segments with excellent interobserver agreement (kappa = 0.84). There was a significant correlation between CE-MRA and conventional angiography for the degree of stenosis (R = 0.92 and 0.89 for observers 1 and 2, respectively). The sensitivity and specificity of CE-MRA for the detection of arterial stenoses 50% or greater were 92% and 96% for observer 1 and 93% and 97% for observer 2, respectively, compared with those of conventional angiography.

CONCLUSION

Using a multichannel radiofrequency system with multicoil technology, the whole-body CE-MRA approach outlined in this article is able to provide high-spatial-resolution data sets with high diagnostic image quality for evaluation of arterial occlusive disease in most vascular territories.

Gadodiamide-Associated Nephrogenic Systemic Fibrosis: Why Radiologists Should Be Concerned

OBJECTIVE

Nephrogenic systemic fibrosis (NSF) is a rare multisystemic fibrosing disorder that principally affects the skin but may affect other organs of patients with renal insufficiency. The purpose of our study was to identify any common risk factors and determine whether i.v. gadodiamide is associated with the development of NSF.

MATERIALS AND METHODS

A retrospective chart review was performed for all 12 patients diagnosed with NSF at our institution between 2000 and 2006 to identify the clinical manifestations, timing, and dose of gadodiamide administration; dialysis records; concurrent medications; comorbid conditions and surgeries; laboratory findings; imaging findings; and clinical outcome. A review of the dialysis and MR records between 2000 and 2006 showed 559 MRI examinations on 168 dialysis patients (including 301 contrast-enhanced examinations).

RESULTS

NSF was diagnosed by clinical findings and tissue diagnosis. All 12 patients had renal insufficiency--eight with dialysis-dependent chronic renal insufficiency and four with acute hepatorenal syndrome. All 12 patients developed skin fibrosis within 2-11 weeks after gadodiamide administration. The odds ratio for development of NSF after gadodiamide exposure was 22.3. No other common event or exposure could be found. Four patients had abnormal scintigraphic bone scans with skin and muscle uptake and lower-extremity MRI finding of edema in the muscles, intermuscular fascia, and skin. Despite the fact that 10 patients were dialyzed within 2 days of gadodiamide administration, this did not prevent the development of NSF.

CONCLUSION

Development of NSF was strongly associated with gadodiamide administration in the setting of either acute hepatorenal syndrome or dialysis-dependent chronic renal insufficiency.

MRI of the kidney and urinary tract

MRI of the kidney and urinary tract has evolved with advancements in MR technology combined with further radiologic experience. A combination of simple pulse sequences and the use of gadolinium (Gd) allow a comprehensive evaluation of the genitourinary system and facilitate the detection and accurate characterization of renal and urinary tract masses. In this review an MRI technique used to evaluate the kidneys and urinary tract is presented with an emphasis on the characterization of renal masses.

3D excretory MR urography: Improved image quality with intravenous saline and diuretic administration

PURPOSE

To assess the effect of diuretic administration on the image quality of excretory magnetic resonance urography (MRU) obtained following intravenous hydration, and to determine whether intravenous hydration alone is sufficient to produce diagnostic quality studies of nondilated upper tracts.

MATERIALS AND METHODS

A total of 22 patients with nondilated upper tracts were evaluated with contrast-enhanced MRU. All patients received 250 mL of saline intravenously immediately prior to the examination. A total of 11 patients received 10-20 mg furosemide in addition to saline. Imaging was performed with a three-dimensional (3D) and two-dimensional (2D) breathhold spoiled gradient-echo sequences. Excretory MRU images were acquired five minutes after the administration of 0.1 mmol/kg gadolinium and were independently reviewed by two radiologists, who were blinded to the MRU technique. Readers evaluated the calyces, renal pelvis, and ureters qualitatively for degree of opacification, distention, and artifacts on a four-point scale. Statistical analysis was performed using a permutation test.

RESULTS

There was no significant disagreement between the two readers (P=0.14). Furosemide resulted in significant improvement in calyceal and renal pelvis distention (P<0.005), and significant artifact reduction in all upper tract segments (P<0.001) compared to the effect of saline alone.

CONCLUSION

Intravenous furosemide significantly improves the image quality of excretory MRU studies obtained following intravenous hydration. Intravenous saline alone is insufficient to produce diagnostic quality studies of the non-dilated upper tracts.

Utilizing generalized autocalibrating partial parallel acquisition (GRAPPA) to achieve high-resolution contrast-enhanced MR angiography of hepatic artery: initial experience in orthotopic liver transplantation candidates

OBJECTIVE

To evaluate feasibility of using GRAPPA to acquire high-resolution 3D contrast-enhanced MR angiography (CE-MRA) of hepatic artery and value of GRAPPA for displaying vessels anatomy.

MATERIALS AND METHODS

High-resolution CE-MRA using GRAPPA was performed in 67 orthotopic liver transplantation recipient candidates. Signal intensity (SI) and relative SI, i.e., Cv-ro (vessel-to-liver contrast) of the aorta and the hepatic common artery (HCA), were measured. The SI and the relative SI were compared and analyzed using T-test. For purpose of qualitative evaluation, the vessel visualization quality and the order of depicted hepatic artery branches were evaluated by two radiologists independently and assessed by weighted kappa analysis. The depiction of hepatic arterial anatomy and variations was evaluated, and results were correlated with the findings in surgery.

RESULTS

The mean SI values were 283.29+/-65.07 (mean+/-S.D.) for aorta and 283.16+/-64.07 for HCA, respectively. The mean relative SI values were 0.698+/-0.09 for aorta and 0.696+/-0.09 for HCA, respectively. Homogeneous enhancement between aorta and HCA was confirmed by statistically insignificant differences (p-values were 0.89 for mean SI values and 0.12 for mean relative SI values, respectively). The average score for vessel visualization ranged from good to excellent for different artery segments. Overall interobserver agreement in the visualization of different artery segments was excellent (kappa value>0.80). The distal intrahepatic segmental arteries were well delineated for majority of patients with excellent interobserver agreement. Normal hepatic arterial anatomy was correctly demonstrated in 53 patients, and arterial anomalies were accurately detected on high-resolution MRA image of all 14 patients.

CONCLUSION

High-resolution hepatic artery MRA acquired using GRAPPA in a reproducible manner excellently depicts and delineates small vessels and can be routinely used for evaluating OLT candidates.

Gadobenate dimeglumine-enhanced liver MRI as the sole preoperative imaging technique: a prospective study of living liver donors

OBJECTIVE

The objective of our study was to determine whether gadobenate dimeglumine-enhanced MRI is practical as the sole preoperative imaging technique for the examination of living liver donors.

SUBJECTS AND METHODS

Forty-four consecutive living donor candidates underwent liver MRI on a 1.5-T MR unit. The MR examination included in- and opposed-phase T1-weighted gradient-echo imaging, T2-weighted MR cholangiography, MR angiography (MRA) and parenchymal phase imaging after the administration of gadobenate dimeglumine, and 60-minute delayed T1-weighted MR cholangiography. Two abdominal radiologists analyzed the images regarding the depiction of the biliary duct anatomy and the hepatic vascular anatomy and for the presence of focal or diffuse liver disease. The findings were compared with intraoperative cholangiographic and surgical findings in 24 patients who underwent partial hepatectomy.

RESULTS

In the 24 patients who underwent liver harvesting, 10 had biliary anatomic variants confirmed by intraoperative cholangiography. T2-weighted MR cholangiography allowed a correct diagnosis in 75% (n = 18/24) and T1-weighted MR cholangiography in 79% (n = 19/24) of these patients. When we evaluated the bile duct anatomy using the combined findings of T2- and T1-weighted MR cholangiographic images, the diagnostic accuracy increased to 92% (n = 22/24), but the difference was not statistically significant (p > 0.05). MRA showed a diagnostic accuracy of 79% (n = 19/24) for the hepatic arterial anatomy, 100% (n = 24/24) for the portal venous anatomy, and 96% (n = 23/24) for the hepatic venous anatomy.

CONCLUSION

Gadobenate dimeglumine-enhanced MRI allows comprehensive assessment of the biliary and hepatic vascular systems and the hepatic parenchyma and can serve as the sole preoperative imaging test for living liver donor candidates.

Tratamento endovascular do aneurisma da aorta abdominal em paciente com insuficiência renal crônica

A insuficiência renal crônica não-dialítica é uma contra-indicação relativa ao tratamento endovascular dos aneurismas da aorta abdominal. O uso de contrastes alternativos, como o gadolínio, além de fornecer imagens de baixa qualidade, está relacionado à nefrotoxicidade. Relatamos um caso de tratamento endovascular de aneurisma da aorta abdominal guiado por eco-Doppler colorido. Um paciente masculino de 82 anos, com aneurisma da aorta abdominal de 55 mm de diâmetro e clearance de creatinina de 17 ml/min, recebeu implante de endoprótese aórtica modular bifurcada, utilizando este método de imagem associado à radioscopia. Não foi empregado contraste iodado. O resultado imediato e os controles de 1 e 6 meses revelam completa exclusão do aneurisma. A função renal permanece inalterada. Concluímos que o implante de endoprótese guiado por eco-Doppler colorido em pacientes com insuficiência renal crônica não terminal e com anatomia favorável é um método factível e seguro.

Detection of Colorectal Polyps: Comparison of Multi–Detector Row CT and MR Colonography in a Colon Phantom

PURPOSE

To compare multi-detector row (four- and 16-section) computed tomography (CT), including a low-dose protocol, with high-field-strength (1.5- and 3.0-T) magnetic resonance (MR) imaging for reader detection of colorectal polyps in a colon phantom.

MATERIALS AND METHODS

A colon phantom with simulated haustral folds and 10 polyps of varying size (2.0-8.0 mm) was imaged at four- and 16-section CT (section thicknesses of 1.25 and 0.75 mm, reconstruction increments of 0.8 and 0.7 mm, and 100 and 10 mAs, respectively, and 120 kV for both) and at 1.5- and 3.0-T MR imaging (three-dimensional gradient-recalled echo sequence, section thickness of 1.4 mm). Three-dimensional endoluminal images were assessed by 10 reviewers for each modality regarding polyp detection. Comparisons of sensitivities were performed by using logistic regression.

RESULTS

Overall, polyps were detected with a sensitivity of 87% (95% confidence interval [CI]: 80%, 94%) at four-section CT, 92% (95% CI: 87%, 97%) at 16-section CT, 56% (95% CI: 46%, 66%) at 1.5-T MR imaging, and 55% (95% CI: 45%, 65%) at 3.0-T MR imaging. The detection of polyps at least 4 mm in diameter was not influenced by the modality or radiation dose (sensitivity of 100%). CT performed in low-dose mode depicted all polyps with a diameter of at least 3 mm. Polyps smaller than 3 mm in diameter were detected with a sensitivity of 7.5% (1.5-T MR imaging), 22.5% (3.0-T MR imaging), and 20% (low-dose CT); detection rates were significantly greater (P < .001) with normal-dose CT (four section, 67.5%; 16 section, 82.5%). Increased spatial resolution (with CT) and higher field strength (with MR imaging) had no significant effect on polyp detection.

CONCLUSION

With both multi-detector row CT and MR imaging, readers detected polyps above the clinically relevant threshold diameter of 6 mm, with similar sensitivities.

Contrast medium use

Various properties of iodinated contrast media (osmolality, ionic versus nonionic, and viscosity) may contribute to contrast-induced nephropathy (CIN). Therefore, the choice of contrast medium affects the risk for CIN. There is good evidence that low-osmolar contrast media are less nephrotoxic than high-osmolar contrast media in patients at increased risk for CIN who receive intra-arterial iodinated contrast. Current evidence suggests that nonionic isosmolar contrast presents the lowest risk for CIN in patients with chronic kidney disease (CKD), particularly in those patients with diabetes mellitus. Intra-arterial administration of contrast media may be associated with a greater risk for CIN above that observed with intravenous administration. The use of gadolinium or CO(2) as alternative contrast media to avoid the risk of nephrotoxicity cannot be substantiated by clinical trials and therefore cannot be recommended. Most studies show that, within a class, higher volumes (>100 mL) of iodinated contrast medium are associated with a higher risk for CIN. However, in patients at high risk, such as those with CKD and diabetes, even small volumes of contrast medium can have adverse effects on renal function.

Are Gadolinium-Based Contrast Media Nephrotoxic?: A Renal Biopsy Study

Gadolinium-based contrast media were originally introduced as alternatives to iodinated media for magnetic resonance imaging. Although originally thought to be nonnephrotoxic, gadolinium-based contrast media have recently been reported to be associated with acute renal failure; the mechanism and the underlying renal injury are not completely understood. We report what is, to our knowledge, the first renal biopsy in this context. A 56-year-old patient underwent 2 consecutive vascular imaging procedures in conjunction with gadolinium-based contrast medium administration. A few days later, the patient developed acute renal failure. A renal biopsy showed acute tubular cell injury including patchy tubular cell necrosis, tubular cell degeneration, and marked proliferation of tubular cells, together with mild interstitial edema and interstitial inflammation, but without significant glomerular or vascular changes. During supportive therapy, renal function was partially regained. This case emphasizes the potential nephrotoxicity of gadolinium-based contrast media and suggests that the nephrotoxicity is related to potentially reversible acute tubular cell injury.

High-spatial-resolution contrast-enhanced MR angiography of abdominal arteries with parallel acquisition at 3.0 T: initial experience in 32 patients

OBJECTIVE

The objective of our study was to evaluate an isotropic high-spatial-resolution 3D contrast-enhanced MR angiography (CE-MRA) protocol with high acceleration parallel acquisition at 3.0 T for the display of the abdominal vasculature.

SUBJECTS AND METHODS

Thirty-two consecutive patients (13 men, 19 women; age range, 28-88 years) with suspected abdominal arterial disease underwent abdominal 3D CE-MRA on a 3.0-T MR system, using a high-spatial-resolution (0.7 x 0.82 x 0.8 mm3) 3D gradient-refocused echo (GRE) sequence, integrated with a generalized autocalibrating partially parallel acquisitions (GRAPPA) technique with an acceleration factor of 3. Two vascular radiologists evaluated image quality and the presence and degree of arterial stenoses. Interobserver variability was calculated, using the kappa coefficient. The sensitivity and specificity of the technique were calculated and comparative analysis was performed with those of conventional catheter angiography (in eight patients) as the standard of reference.

RESULTS

The abdominal arterial vasculature was visualized with diagnostic image quality in all subjects. Arterial stenoses were detected in 148 and 142 arterial segments by observer 1 and observer 2, respectively, with good interobserver agreement (kappa = 0.75; 95% confidence interval [CI]: 0.69-0.81). The sensitivity and specificity values for CE-MRA for the detection of significant (> 50%) arterial stenoses were 100% and 96% for observer 1 and 100% and 92% for observer 2, respectively. There was a significant correlation between CE-MRA and conventional angiography (R = 0.96 and 0.93 for observers 1 and 2, respectively) for the assessment of the degree of stenosis.

CONCLUSION

The outlined MR angiography protocol at 3.0 T combined with parallel acquisition technique renders highly reliable and isotropic high-spatial-resolution imaging of the abdominal vasculature.

Real-time magnetic resonance-guided placement of retrievable inferior vena cava filters: comparison with fluoroscopic guidance with use of in vitro and animal models

PURPOSE

To compare the precision of magnetic resonance (MR)-guided versus fluoroscopy-guided placement of retrievable inferior vena cava (IVC) filters with use of real-time MR imaging strategies optimized for each device in an in vitro model and in an animal model.

MATERIALS AND METHODS

Three different retrievable IVC filters were used in this study, including the Recovery, Günther Tulip, and OptEase devices. Experiments were performed on a 1.5 T-MR system with pre-release interactive MR software. For each device, high-resolution real-time MR imaging was optimized with use of steady-state free precession and fast low-angle shot sequences with radial and cartesian trajectories and varying flip angles (10 degrees -70 degrees ) and a frame rate of 2 per second. A custom-built IVC phantom was filled with dilute gadolinium contrast agent at a concentration of 0.05 mmol/L simulating a blood T1 of 8 msec and T2 of 6 msec. Signal intensities were measured in regions of interest at the filter, the IVC lumen, and the background. The contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) were calculated. The sequence suited best for each device was chosen for in vitro filter placement in a custom-made IVC phantom. Each device was deployed five times each under MR and fluoroscopic guidance with use of identical techniques. Accuracy was measured as absolute deviation of the filter tip in millimeters from a target landing zone. Differences were assessed statistically with use of the paired t test. Each device was also placed in vivo in a swine model under MR guidance.

RESULTS

All three IVC filters could be clearly identified and positioned under fluoroscopic and MR imaging control. A cartesian true fast imaging sequence with steady-state precession with a flip angle of 30 degrees or 50 degrees resulted in optimal SNR and CNR for all three filters. The Tulip filter created more susceptibility artifacts than the other two. Filter placement accuracy was similar with MR and fluoroscopy whether comparing devices individually (P=NS) or as a group (P=NS). The mean absolute differences between MR and fluoroscopy were 0.088 mm for the OptEase filter, 0.41 mm for the Bard Recovery filter, and 0.34 mm for the Günther Tulip filter.

CONCLUSIONS

MR-guided placement of retrievable IVC filters is feasible and as accurate as fluoroscopy-guided placement in an in vitro model. With optimized sequences, real-time MR has the potential to develop as a reasonable alternative to fluoroscopy.

Selection of contrast media

The pathophysiologic mechanisms of contrast-induced nephropathy (CIN) have been reviewed by Persson and Tepel. They focus on the renal response to contrast media (CM). In this section, we focus on the CM itself. Aspects of importance with regard to CIN include the route of administration, the volume of CM, the manner of X-ray attenuation, and the specific chemical structure of the CM.

High spatial-resolution CE-MRA of the carotid circulation with parallel imaging: comparison of image quality between 2 different acceleration factors at 3.0 Tesla

PURPOSE

We sought to evaluate and compare the image quality and vessel delineation of the carotid arteries with high spatial-resolution contrast-enhanced MRA (CE-MRA) at 3.0 T using integrated parallel acquisition (iPAT) with acceleration factors of 2 and 4.

MATERIALS AND METHODS

Using an 8-channel neurovascular array coil, we performed prospective high-spatial resolution CE-MRA at 3.0 T of the head and neck on 24 patients (11 men, 13 women, ages 37-89) with suspected arterio-occlusive disease who were assigned randomly to 2 groups. Twelve patients (group A) were examined with a 3D-GRE sequence using iPAT with acceleration factor of 2. For the next 12 patients (group B) a near-identical sequence with an acceleration factor of 4 was applied. Higher iPAT factors were used to increase the spatial-resolution while keeping scan time unchanged. Two volunteers were scanned by both protocols. Phantom measurements were performed to assess the signal-to-noise ratio (SNR). The presence of artifact, noise, image quality of the arterial segments, and the presence and degree of arterial stenosis were evaluated independently by 2 radiologists. Statistical analysis of data was performed by using Wilcoxon rank sum test and 2-sample Student t test (P < 0.05 was indicative a statistically significant difference). The interobserver variability was tested by kappa coefficient.

RESULTS

SNR values were significantly lower when iPAT with acceleration factor of 4 was used (P < 0.001). There was no significant difference between 2 groups in regards to image noise (P = 0.67) and artifact (P = 0.8). Both readers visualized the majority of carotid circulation with good image quality in both groups. For smaller intracranial arteries, such as the second-division of anterior and middle cerebral artery, anterior communicating artery, and superior cerebellar artery, the image quality and vessel delineation was significantly better at an iPAT factor of 4 (P < 0.01). The overall interobserver agreement for both the vessel depiction, and detection of arterial stenoses was higher in group B compared with group A.

CONCLUSION

Use of parallel acquisition techniques with a high acceleration factor (iPAT-4) results in superior depiction of small intracranial arterial segments. Imaging at higher magnetic field strength, in addition to the use of an optimized 8-channel array coil, provides sufficient SNR to support faster parallel acquisition protocols, leading to improved spatial-resolution. More extensive clinical studies are warranted to establish the range of applications and confirm the accuracy of the technique.

Noninvasive gadolinium-enhanced three dimensional computed tomography coronary angiography

RATIONALE AND OBJECTIVES

Although the use of gadolinium (Gd)-based contrast agents for angiographic studies of abdominal aorta, renal vasculature, and digital subtraction angiography has been reported, no studies have shown their diagnostic efficacy and image quality in coronary computed tomography angiography (CTA). The aim of this study is to evaluate the image quality of Gd-based contrast agents during coronary CTA.

MATERIALS AND METHODS

A phantom study was done to evaluate the attenuation of serial dilutions of Gd and iodinated agents. This study was done on a 64-slice multirow detector CT (MDCT) scanner and e-speed scanner and CT attenuation Hounsfield units (CTHU) were compared. We evaluated 35 consecutive patients who underwent Gd-enhanced CTA. CTHU of aorta was measured at first, mid, and lowest slice levels with and without contrast administration. The image quality was graded on the basis of visualization of the coronary arteries (scale I-III; III demonstrating diagnostic image quality of the distal-most vessels). In a substudy, four patients with borderline renal insufficiency underwent CTA using Gd and iodinated contrast agents admixed in a 50:50 ratio.

RESULTS

The phantom study showed that enhancement of various dilutions of Gd and iodine resulted in near identical CTHU with both e-speed and 64-slice scanners (r(2) > or = 0.997). Mean CTHU with contrast at the top slice was 116 HU, at middle slice was 125 HU, and at the lower slice was 93 (111.14 +/- 22). Quality evaluation showed 2 grade III, 9 grade II, and 24 grade I images (average quality of images 1.35). Mean CTHU was 222.

CONCLUSION

Gd-enhanced contrast medium provides adequate enhancement of coronary vasculature, allowing for diagnostic evaluation of coronary arteries with new CT systems. Use of newer generations of multirow detector CT scanners should further enhance the quality of images.

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.

MR colonography: current status

Magnetic resonance colonography (MRC) has gained access into clinical routine as a means for the assessment of the large bowel. There are widely accepted indications for MRC, especially in patients with incomplete conventional colonoscopy. Furthermore, virtual MRC is more and more propagated as a screening tool, with advantages especially inherent to the non-invasive character of this procedure and the lack of ionizing radiation exposition. Beyond a sufficiently high diagnostic accuracy, outstanding patient acceptance is a major advantage of MRC as a diagnostic modality. This review article describes indications, techniques and clinical outcome of current MRC approaches. Furthermore, the impact of fecal tagging concepts is discussed.

Takayasu arteritis: Role of cardiovascular magnetic imaging

Takayasu arteritis (TA) is a primary arteritis of unknown cause that commonly affects the aorta and its main branches. Traditionally, X-ray contrast angiography has been the gold standard for diagnosis and review of this chronic disease but recent developments suggest that non-invasive imaging with multiplanar cardiovascular magnetic resonance imaging (CMR) and magnetic resonance angiography (MRA) have a number of advantages for use in routine care. This review utilises a series of cases referred for imaging at the Royal Brompton Hospital, London to illustrate these points of development.

Multi–Detector Row CT Angiography of Pulmonary Circulation with Gadolinium-based Contrast Agents: Prospective Evaluation in 60 Patients

PURPOSE

To prospectively evaluate gadolinium dose safety and effectiveness for 16-detector pulmonary computed tomographic (CT) angiography.

MATERIALS AND METHODS

Ethics committee approval and informed consent were obtained. Sixty patients with contraindications to iodine underwent CT of the pulmonary circulation with 0.5 mmol/L gadolinium chelate given at either 0.3 (n = 29, group A) or 0.4 (n = 31, group B) mmol/kg; clinical and biologic tolerances were evaluated. Enhancement of central and segmental pulmonary arteries was measured (poor enhancement, <100 HU; good, 100-150 HU; excellent, >150 HU). Subsegmental artery enhancement was assessed as similar or inferior to that of segmental arteries. Confidence in analysis of the pulmonary arterial bed was graded according to arterial enhancement: Grades 1-3, diagnostic images; grade 4, nondiagnostic. The main effectiveness parameter for comparison between groups A and B was diagnostic value of CT angiograms. Nonparametric statistics were used to analyze results.

RESULTS

The mean (+/- standard deviation) contrast material volume was 50.09 mL +/- 8.45 (all patients: range, 30-64 mL; group A: 46.54 mL +/- 8.59; group B: 53.42 mL +/- 6.92). Diagnostic images were obtained in 55 (92%) patients, and confident analysis of pulmonary arteries to the subsegmental level was achieved in 26 (grade 1, 44%) and to the segmental level, in 21 (grade 2, 35%). Mean attenuation was higher in group B than in group A in central (180.61 HU +/- 53.85 vs 148.14 HU +/- 52.61; P = .04) and segmental (201.59 HU +/- 54.70 vs 164.73 HU +/- 59.26; P = .03) arteries. Number of diagnostic CT angiograms was higher (P = .02) in group B (n = 31 [100%]) than in group A (n = 24 [83%]). In both groups, mean enhancement of pulmonary arteries was significantly higher at 80 or 100 kV than at 120 kV. Renal function was impaired in two group A patients.

CONCLUSION

Gadolinium chelates may be used as an alternative CT contrast agent in patients who cannot receive iodine.

Time-Resolved Contrast Enhanced Magnetic Resonance Angiography of the Head and Neck at 3.0 Tesla

OBJECTIVES

We sought to implement and evaluate a high-performance, extended field of view protocol for time-resolved contrast-enhanced magnetic resonance imaging (CEMRA) of the carotid circulation by using a dedicated neurovascular (NV) array coil.

MATERIALS AND METHODS

A total of 16 adult volunteers and 20 clinical patients with suspected cerebrovascular disease (15 male, 21 female, 25-82 years of age) were scanned with a fast 3D MRA sequence (TR/TE: 2.16/1 milliseconds, sampling BW: 1090 Hz/pixel), with echo-sharing and parallel acquisition. All studies were performed on a 3.0 T MR system using an 8-channel neurovascular array coil. After injection of 6 mL of gadodiamide at 3 mL/s, a coronal 3D data set with in-plane resolution of 1 x 1.3 was implemented for 10 consecutive measurements each 1.8 seconds apart. The subjects subsequently underwent high spatial-resolution (in-plane: 0.8 x 0.9) CEMRA for comparative analysis. The quality of segmental arterial anatomy and the presence and degree of the arterial stenosis were evaluated by 2 neuroradiologists. The interobserver variability was tested by kappa statistics and comparative analysis between the TR-CEMRA and high spatial-resolution CEMRA was evaluated by mean of the Spearman rank correlation coefficient.

RESULTS

Craniocervical arteries were visualized with good image quality and definition in the diagnostic range. Occlusive disease was detected in 42 (reader A) and 44 (reader B) arterial segments with excellent interobserver agreement (kappa =0.89; 95% confidence interval 0.82-0.96). There was a significant correlation between the TR-CEMRA and high spatial-resolution CEMRA (Rs = 0.91 and 0.93, for readers A and B, respectively) for the degree of stenosis. Three aneurysms, 3 AVMs, 1 AV-fistula, and 2 subclavian steals were detected by both observers and were confirmed by correlative imaging.

CONCLUSION

Time-resolved CEMRA at 3.0 T is reliable and versatile, providing 3-dimensional time-resolved data sets with high spatial (in plane: 1.3 x 1 mm2) and temporal (1.8 seconds) resolution over a large field of view. The higher signal-to-noise ratio gain at 3.0 T can be used effectively to improve performance of fast imaging and to support aggressive parallel acquisition protocols, as in the present study. Further clinical studies are required to establish the range of applications and the accuracy of the technique.

Effects of gadopentetate dimeglumine and gadodiamide on serum calcium, magnesium, and creatinine measurements

PURPOSE

To investigate the in vivo effects of gadodiamide (Gd-DTPA-BMA) and gadopentetate dimeglumine (Gd-DTPA) on the laboratory measurements of serum calcium, magnesium, and creatinine.

MATERIALS AND METHODS

Medical records from 1993 to 2004 were reviewed to identify inpatients for whom laboratory data were available regarding serum calcium, creatinine, and magnesium levels before and within one day after gadodiamide and gadopentetate dimeglumine enhanced MRI. Patients who underwent both gadolinium (Gd)-enhanced MRI and iodinated contrast-enhanced examinations on separate days within a six-month period were also identified to compare changes in serum creatinine.

RESULTS

Serum creatinine did not increase in 2788 cases following gadopentetate dimeglumine and gadodiamide injection. By comparison, serum creatinine increased from 1.21 to 1.28 mg/dL following iodinated contrast, and there were 20 cases (2.6%) of contrast-induced nephrotoxicity (P < 0.01). Gadopentetate dimeglumine did not affect serum calcium or magnesium measurements. Following 1157 gadodiamide-enhanced examinations, measured serum calcium spuriously dropped from 8.65 to 8.33 mg/dL (P < 0.0001) and 34 patients had spurious critical hypocalcemia (<6 mg/dL). Of 60 patients with high-dose gadodiamide injection and renal insufficiency, 36.7% (N = 22) had spurious critical hypocalcemia immediately post MRI. In 216 patients with renal insufficiency, the mean serum magnesium level increased slightly from 1.69 to 1.77 mEq/L following gadodiamide injection (P < 0.0001).

CONCLUSION

Gd-based contrast agents are safe for MRI and MR angiography (MRA), and do not induce nephrotoxicity. However, gadodiamide interferes with serum calcium and magnesium measurements-particularly at high doses and/or with renal insufficiency.

Gadolinium-based contrast agents and nephrotoxicity in patients undergoing coronary artery procedures

OBJECTIVE

We tested whether gadolinium-based contrast agent is less nephrotoxic than iodinated-contrast media.

BACKGROUND

Iodinated contrast agents are nephrotoxic. Some data suggest that gadolinium-based contrast agent may be less nephrotoxic than iodinated-contrast media.

METHODS

Twenty-five consecutive patients with chronic renal insufficiency (creatinine concentration > or = 2.0 mg/dl and/or clearance < or = 40 ml/min), referred to our institution for coronary procedures, were assigned to receive gadolinium-based contrast agents, a solution of gadolinium chelates diluted 3:1 by iso-osmolality contrast media (Gadolinium-based group). A control group of 32 patients with comparable clinical characteristics and treated with iodinated iso-osmolality contrast agent alone (Iodinated-based group) was selected from our database and compared with the Gadolinium-based group. In all cases, prophylactic administration of 0.45% saline intravenously and NAC (1200 mg orally twice daily) was used.

RESULTS

Baseline creatinine levels and creatinine clearance were similar in the 2 groups (Gadolinium-based group = 2.30 [IQR: 2.01-2.68] mg/dl and 33 +/- 13 ml/min; Iodinated-based group = 2.24 [IQR: 2.05-2.65] mg/dl and 30 +/- 10 ml/min; P > 0.05 for all). Increase of at least 0.5 mg/dl of the creatinine concentration 48 hr after the procedure occurred in 7/25 (28%) patients in the Gadolinium-based group and in 2/32 (6.5%) patients in the Iodinated-based group (P = 0.034; OR = 4.48; 95% CI = 1.01-19.17). Renal failure requiring temporary dialysis occurred in 2 (8%) patients in the Gadolinium-based group and in none in the Iodinated-based group (P = 0.19).

CONCLUSIONS

The strategy of gadolinium-based contrast agent administration does not seem to reduce the rate of CAN, as compared to the iodinated iso-osmolality contrast agent in patients with chronic renal insufficiency.

Renal artery stenting in solitary functioning kidneys: Technical and clinical results

OBJECTIVE

To evaluate the clinical and technical results of renal artery stenting for the treatment of renovascular hypertension and renal failure in patients with solitary functioning kidney.

MATERIALS AND METHODS

Fifteen patients with solitary functioning kidney underwent renal artery stenting and were followed up for 12-60 months. Before the procedures, systolic and diastolic blood pressures and serum creatinine levels were measured and the number of antihypertensive drugs was recorded and followed up after stenting. In case of restenosis, either in-stent percutaneous transluminal renal angioplasty or stent-in-stent placement was performed.

RESULTS

Primary technical success rate was 100%. One lesion was nonostial while 14 were ostial. Primary patency rates were 100% for 6 months, 92.3% for 12 months, and 69.2% for 24 months. The secondary patency rate at 24 months was 100%. The differences between the baseline and postprocedural values of systolic blood pressures, diastolic blood pressures and the number of antihypertensive drug were statistically significant (P < 0.05), except the values of serum creatinine. Hypertension was cured in 1 (6.7%) patient, improved in 4 (26.6%) and stabilized in 10 (66.7%) patients. Renal function improved in 9 (60%), stabilized in 4 (26.6%), and deteriorated in 2 (13.4%) patients. Minor complication rate was 13.4% and major complication rate was 13.4%.

CONCLUSION

Revascularization of renal artery stenosis using stent in solitary functioning kidneys is a safe and efficient procedure with high primary technical results, low restenosis rates and acceptable complication rates. It has an improving and controlling effect on blood pressure and renal functions.

Gadolinium-Enhanced Computed Tomographic Angiography: Current Status

This article reviews the research to date, as well as our clinical experience from two institutions, on gadolinium-enhanced computed tomographic angiography (gCTA) for imaging the body. gCTA may be an appropriate examination for the small percentage of patients who would benefit from noninvasive vascular imaging, but who have contraindications to both iodinated contrast and magnetic resonance imaging. gCTA is more expensive than CTA with iodinated contrast, due to the dose of gadolinium administered, and gCTA has limitations compared with CTA with iodinated contrast, in that parenchymal organs are not optimally enhanced at doses of 0.5 mmol/kg or lower. However, in our experience, gCTA has been a very useful problem-solving examination in carefully selected patients. With the advent of 16-64 detector CT, in combination with bolus tracking, we believe that the overall dose of gadolinium needed for diagnostic CTA examinations, while relatively high, can be safely administered.

Prospective study comparing three-dimensional computed tomography and magnetic resonance imaging for evaluating the renal vascular anatomy in potential living renal donors

OBJECTIVE

To prospectively compare the accuracy of multislice spiral computed tomographic angiography (CTA) and magnetic resonance angiography (MRA) in evaluating the renal vascular anatomy in potential living renal donors.

SUBJECTS AND METHODS

Thirty-one donors underwent multislice spiral CTA and gadolinium-enhanced MRA. In addition to axial images, multiplanar reconstruction and maximum intensity projections were used to display the renal vascular anatomy. Twenty-four donors had a left laparoscopic donor nephrectomy (LDN), whereas seven had right open donor nephrectomy (ODN); LDN was only considered if the renal vascular anatomy was favourable on the left. CTA and MRA images were analysed by two radiologists independently. The radiological and surgical findings were correlated after the surgery.

RESULTS

CTA showed 33 arteries and 32 veins (100% sensitivity) whereas MRA showed 32 arteries and 31 veins (97% sensitivity). CTA detected all five accessory renal arteries whereas MRA only detected one. CTA also identified all three accessory renal veins whereas MRA identified two. CTA had a sensitivity of 97% and 47% for left lumbar and left gonadal veins, whereas MRA had a sensitivity of 74% and 46%, respectively.

CONCLUSION

Multislice spiral CTA with three-dimensional reconstruction was more accurate than MRA for both renal arterial and venous anatomy.

Uroangiographic Contrast Media-Induced Nephropathy: Correlations between Their Physicochemical Properties and Renal Damage

Contrast media-induced nephropathy (CN) is an important cause of hospital-acquired acute renal failure. Patients with both diabetes mellitus and renal impairment are at high risk. CN pathophysiology involves activation of the tubulo-glomerular feedback and vasoactive mediators such as renin-angiotensin 2, endothelin, adenosine, ADH, etc. The risk of CN can be minimized by the use of non-ionic, low or isoosmolar, contrast material, adequate hydration and prophylactic pharmacological measures. In patients with chronic renal failure who are undergoing arteriography (e.g. coronary angiography and angioplasty), periprocedural hemofiltration appears effective in preventing further renal damage due to contrast agents.

Virtual colonoscopy by MRI: state-of-the-art and future directions

MR colonography has been shown to be an appropriate diagnostic tool for the detection of colorectal lesions. The technique is based on the acquisition of T1-weighted sequences after the administration of water enema and the intravenous administration of paramagnetic contrast. This article describes the technical requirements for MR colonoscopy and the procedures of data acquisition and image interpretation. The advantages and drawbacks of MR colonoscopy also are outlined.

MR Angiography of Aortoiliac Occlusive Disease: A Phase III Study of the Safety and Effectiveness of the Blood-Pool Contrast Agent MS-325

PURPOSE

To evaluate prospectively the safety and effectiveness of aortoiliac magnetic resonance (MR) angiography enhanced with MS-325 (gadofosveset trisodium) at a dose of 0.03 mmol/kg; effectiveness was defined as accuracy relative to the reference standard, conventional angiography.

MATERIALS AND METHODS

Study was approved by institutional review boards of participating institutions, and required national approvals were obtained. Study protocol conformed to Good Clinical Practice guidelines, and informed patient consent was obtained. Patients with known or suspected peripheral vascular disease received 0.03 mmol/kg MS-325 for aortoiliac MR angiography. They were also examined with conventional angiography. MS-325-enhanced MR was evaluated for safety and effectiveness. Along with unenhanced two-dimensional time-of-flight MR angiography, it was compared with conventional angiography for presence of vascular stenosis. Student t tests were used to identify significant improvement in diagnostic sensitivity, specificity, and accuracy, as well as quantitative characterization of stenoses by three blinded readers. Correlations between readers of conventional angiograms were calculated and compared with MR results.

RESULTS

In 174 patients, MS-325-enhanced MR angiography showed significant improvement (P < or = .001) in sensitivity, specificity, and accuracy for diagnosis of clinically significant (> or =50%) stenosis, compared with unenhanced MR. For all readers, areas under the receiver operating characteristic curve for both quantitative and qualitative measures of significant disease increased (P < .001) for MS-325-enhanced MR compared with time-of-flight MR. All readers also expressed higher confidence in diagnosis (P < .001) and found fewer images uninterpretable with MS-325 enhancement. All measures of interpretation accuracy approached corresponding measures of correlation between readers of conventional angiograms. Incidence of severe and serious adverse events with MS-325 was low. No patients were withdrawn from study due to adverse events or abnormalities in laboratory results. There were no clinically important trends in findings at hematology, blood chemistry, urinalysis, electrocardiography, or physical examination.

CONCLUSION

MR angiography with MS-325 provides significant improvement in effectiveness over unenhanced MR (and minimal and transient side effects) at a dose of 0.03 mmol/kg and was safe and effective for MR evaluation of patients with aortoiliac occlusive disease.

"All-in-one" imaging protocols for the evaluation of potential living liver donors: comparison of magnetic resonance imaging and multidetector computed tomography

In order to compare the performance of "all-in-one" magnetic resonance imaging (MRI) and "all-in-one" multidetector computed tomography (MDCT) in the preharvest evaluation 25 potential living donors underwent both MRI and MDCT. MRI was performed on a high-performance 1.5-T scanner, computed tomography (CT) on a 4-row multidetector-scanner. Both scan protocols included angiography of the arterial and venous hepatic systems. CT additionally included infusion of a biliary contrast agent. Data analysis was performed by 4 reviewers, based on source images, multiplanar reformats, and three-dimensional (3D) postprocessing. Determination of image quality was based on a 4-point image quality rating (IQR) scale, ranging from 1 = nondiagnostic to 4 = excellent. Preoperative and intraoperative (n = 13) findings were correlated. Magnetic resonance (MR) examinations were generally well tolerated. Within the CT scan, 2 candidates presented moderate adverse reaction to the biliary contrast agent. MRI and CT showed the same benign parenchymal lesions (IQR MR: 3.7; IQR CT: 3.4). Determination of liver volumes was easier based on CT (IQR MR: 3.3; IQR CT: 3.6). Magnetic resonance angiography (MRA) revealed 10 variants of the arterial liver supply (IQR: 3.0) and computed tomographic angiography (CTA) revealed 13 variants (IQR: 3.5). Magnetic resonance cholangiopancreatography (MRCP) identified 4 biliary variants (IQR: 1.3) and CT cholangiography identified 17 (IQR: 3.5). MRI and CT each showed 4 hepatic and portal venous variants (IQR MR: 3.4, CT: 2.8). CT and MR findings correlated well with intraoperative findings. In conclusion, both techniques proved to be efficient to evaluate potential living liver donors' anatomy in a single diagnostic step. The main advantage of CT lies in the ability to accurately assess the biliary anatomy.

Magnetic Resonance Imaging of the Kidney

High tissue contrast, multiplanar image capabilities, and tissue characterization render MR into an ideal imaging modality for effective evaluation of a wide range of renal disorders. It provides high details of anatomy and can suggest the composition of lesions. Improvements of MRI technology during the last years have made MRI increasingly attractive for body imaging. Fast imaging sequences and parallel imaging techniques have proved to be useful in minimizing artifacts from respiratory motion and magnetic susceptibility differences providing superior imaging quality. Additionally, the use of renally eliminated paramagnetic contrast agents permits assessment of parenchymal perfusion and visualization of the excretion of the contrast medium providing information on renal function.

Safety and Effectiveness of Gadolinium-enhanced Multi–Detector Row Spiral CT Angiography of the Chest: Preliminary Results in 37 Patients with Contraindications to Iodinated Contrast Agents

PURPOSE

To prospectively evaluate the safety and effectiveness of gadolinium-enhanced multi-detector row spiral computed tomographic (CT) angiography of the pulmonary circulation by using two gadolinium doses in patients with contraindications to iodinated contrast agents.

MATERIALS AND METHODS

Study was approved by the Ethics Committee, and written informed consent was obtained. Thirty-seven patients (20 men, 17 women) with contraindications to iodinated contrast agents (allergic reactions, n = 27; impaired renal function, n = 10) underwent CT angiography of the pulmonary circulation in search of acute pulmonary embolism (n = 28) or for management of tumoral disease (n = 9). CT angiography was performed (a) with four-detector row (n = 19) or 16-detector row (n = 18) scanners; (b) at randomly assigned gadolinium doses of either 0.3 mmol per kilogram of body weight (n = 19) or 0.4 mmol/kg (n = 18); and (c) with a systematic evaluation of clinical and biologic tolerance of gadolinium. Comparison of percentages between group 1 and group 2 scans was performed with the chi2 or the Fisher exact test. An unpaired Wilcoxon rank sum test was used for numeric variables. P < .05 was considered to indicate a significant difference.

RESULTS

The mean (+/- standard deviation) volume of gadopentetate dimeglumine administered in the overall study group was 48 mL +/- 9.6 (range, 29-65 mL). The level of maximal enhancement in the pulmonary arteries was significantly higher in group 2 than in group 1 (215.8 HU +/- 95 vs 141.3 HU +/- 44) (P = .02) and was maintained throughout the entire region of interest in a greater number of examinations in group 2 than in group 1 (n = 16 [89%] vs n = 2 [10.5%]) (P < .0001). The number of diagnostic CT angiograms was significantly higher in group 2 than in group 1 (n = 17 [94%] vs n = 13 [68%]) (P = .007). Significant but transient reduction of creatinine clearance was observed in one patient with preexisting moderate chronic renal failure (0.3 mmol/kg gadolinium dose).

CONCLUSION

High-quality gadolinium-enhanced CT angiograms require the use of 16-detector row CT technology; the doses administered did not alter the renal function except transiently in one patient.

Preliminary experience with contrast-enhanced MR angiography in patients with end-stage renal failure

RATIONALE AND OBJECTIVES

The purpose of this study was to evaluate our preliminary experience with routine contrast-enhanced magnetic resonance angiography (CE-MRA) of the lower limb arteries in patients with end-stage renal failure.

MATERIALS AND METHODS

A retrospective analysis was performed on clinical, physiological, and imaging data for 104 patients with end-stage renal failure. Patients were considered to be in end-stage renal failure if they were on renal replacement therapy (peritoneal or hemodialysis) or were being evaluated as part of a pretransplant workup. CE-MRA was carried out on a 1.5-T scanner using a single-injection, three-station moving table technique.

RESULTS

Eleven percent of asymptomatic patients with normal ankle/brachial pressure indexes (ABPI) were found to have severe arterial disease on CE-MRA, and in 30% of asymptomatic patients with abnormal ABPI, CE-MRA showed mild or no disease. Moreover two of three symptomatic patients with normal ABPI were shown to have severe disease. Two patients on peritoneal dialysis had to be switched to hemodialysis. No other adverse events were revealed.

CONCLUSION

CE-MRA is a useful adjunct to clinical and physiological examination for the evaluation of the lower limb arteries in a group of patients who have a higher-than-average incidence of peripheral vascular disease, yet have previously been severely restricted from traditional angiography because of contrast-medium-induced nephrotoxicity.

Perfusion imaging of the liver: current challenges and future goals

Improved therapeutic options for hepatocellular carcinoma and metastatic disease place greater demands on diagnostic and surveillance tests for liver disease. Existing diagnostic imaging techniques provide limited evaluation of tissue characteristics beyond morphology; perfusion imaging of the liver has potential to improve this shortcoming. The ability to resolve hepatic arterial and portal venous components of blood flow on a global and regional basis constitutes the primary goal of liver perfusion imaging. Earlier detection of primary and metastatic hepatic malignancies and cirrhosis may be possible on the basis of relative increases in hepatic arterial blood flow associated with these diseases. To date, liver flow scintigraphy and flow quantification at Doppler ultrasonography have focused on characterization of global abnormalities. Computed tomography (CT) and magnetic resonance (MR) imaging can provide regional and global parameters, a critical goal for tumor surveillance. Several challenges remain: reduced radiation doses associated with CT perfusion imaging, improved spatial and temporal resolution at MR imaging, accurate quantification of tissue contrast material at MR imaging, and validation of parameters obtained from fitting enhancement curves to biokinetic models, applicable to all perfusion methods. Continued progress in this new field of liver imaging may have profound implications for large patient groups at risk for liver disease.

Decreases in free cholesterol and fatty acid unsaturation in renal cell carcinoma demonstrated by breath-hold magnetic resonance spectroscopy

Increased utilization of cross-sectional imaging has resulted in increased detection of incidental renal tumors. The noninvasive characterization of renal tissue has important implications for the diagnosis of renal malignancies and treatment monitoring. Recently, multiple breath-hold averaged proton magnetic resonance spectroscopy (1H-MRS) performed at high field has enabled the use of this noninvasive metabolic profiling technique for the investigation of the abdomen. Multiple breath-hold averaged 1H-MRS at high field (3T) was obtained in the kidneys of 10 healthy volunteers and in renal cell carcinoma tumors of 14 patients. The spectra of normal kidneys showed four main groups of resonances: 1) at 5.4–5.6 ppm, attributed to C6 of cholesterol and the unsaturated parts of the olefinic region of fatty acids; 2) at 4.7 ppm, attributed to the residual water signal; 3) at 3.2 ppm, attributed to trimethylamine moiety of choline metabolites; and 4) at 1.3 and 0.9 ppm, attributed to the methylenes and terminal methyls of lipids. The ratio of the signal at 5.4 ppm to that of 1.3 ppm was 19-fold lower in renal cell carcinomas than in healthy kidneys, tied P = 0.0003 Mann-Whitney U-test, suggesting a decrease in both free cholesterol and the degree of unsaturation of fatty acids in the malignant tissue. This metabolic shift is in agreement with previous ex vivo studies of human renal cell carcinoma. The ability to detect renal metabolic shifts noninvasively may improve the specificity of preoperative renal tissue characterization and may provide a new modality for treatment monitoring.

MR peritoneography in complications of continuous ambulatory peritoneal dialysis

BACKGROUND

We evaluated the usefulness of magnetic resonance (MR) peritoneography for the examination of complications from continuous ambulatory peritoneal dialysis (CAPD).

METHODS

MR peritoneography was performed in 20 patients who had suspected CAPD-related complications. Patients who had active peritonitis were not included in the study. Before MR imaging, a mixture of 2000 mL of peritoneal dialysis solution and 20 mL of gadopentetate dimeglumine was instilled into the peritoneal cavity. MR imaging was performed on a 1.0-Tesla system using a body coil. Axial, coronal, and sagittal fat-saturated fast spoiled gradient echo (repetition/echo times, 100/6.3 ms; flip angle, 90 degrees), axial fat-saturated T2-weighted fast spin echo (repetition/echo times, 6000/107 ms), and coronal fat-saturated T2-weighted fast spin echo (repetition/echo times, 3000/96.2 ms) images of the abdomen and the pelvis were obtained. After drain-age, triplanar fat-saturated fast spoiled gradient echo images were repeated with the same parameters.

RESULTS

Homogeneous distribution of the dialysate in the peritoneal cavity was detected in 18 patients (90%). In 12 patients (60%), fluid leaks were discovered peripheral to the exit site, tunnel, and site of peritoneal entrance of the catheter. Fluid leaks through the abdominal wall in five patients (25%), retroperitoneum in one patient (5%), and a previous operation site in one patient (5%) were demonstrated. No abnormal finding was detected in three patients (15%) who had clinically suspected complications, whereas a dialysate leak was found in two patients (10%) who had no significant finding at physical examination.

CONCLUSIONS

MR peritoneography provides detailed information about the anatomic distribution of dialysate leaks in patients treated with CAPD and poses no risks associated with ionizing radiation and nephrotoxic contrast medium.

Full-Body Cardiovascular and Tumor MRI for Early Detection of Disease: Feasibility and Initial Experience in 298 Subjects

OBJECTIVE

High diagnostic accuracy, emerging whole-body concepts, and lack of side effects combine to render MRI a natural candidate for screening purposes. The aim of this study was to evaluate the technical feasibility of a comprehensive multiorgan-targeting MRI examination and determine the frequency of findings in subjects without a history of serious disease.

SUBJECTS AND METHODS

The study group was composed of 331 subjects. The MRI protocol (mean examination time, 63 min) encompassed the target organs: the brain, arterial system, heart, and colon. Diagnoses were deemed relevant if the physician had to inform the subject about the findings. Subjects with a history of serious illnesses were excluded from subsequent analysis (n=33). All analyses were performed for the resulting subgroup of 298 subjects (247 men, 51 women; mean age, 49.7 years).

RESULTS

All 298 examinations were diagnostic excluding eight MR colonography components in which remaining stool hampered reliable diagnosis. Follow-up or radiologic confirmation could be obtained in 75% of all cases with relevant findings (128/169); only one false-positive result was encountered. Of the study group, 21% exhibited signs of atherosclerotic disease. Two cerebral infarctions and one myocardial infarction, previously unknown, were encountered; 12% had peripheral vascular disease. Twelve colonic polyps and nine pulmonary lesions were correctly detected. Of all MRI examinations, 29% revealed relevant additional findings in nontargeted organs. Only one minor allergoid reaction was encountered.

CONCLUSION

The presented data point toward an increased use of MRI for screening in the future, but to date screening MRI should not be performed outside a research setting because the cost-benefit relation is unclear.

Gadolinium-based balloon angioplasty for pulmonary artery stenosis in an infant with a right isomerism

We report here the first described case of utilizing gadolinium-based contrast material as the contrast agent during a catheter intervention treatment for pulmonary artery stenosis. The patient, a male infant with complex heart disease associated with a right isomerism, had a history of severe allergic reaction to iodine-containing contrast agents. A combination of digital subtraction angiography and a gadolinium contrast agent, however, provided us with good-quality images both before and after balloon angioplasty without any associated complications. This method should therefore be considered as an alternative angiographic procedure in children with a high risk of iodine-related allergic complications.

3D contrast-enhanced MR angiography of the abdominal aorta and its distal branches: Interobserver agreement of radiologists in a routine examination

RATIONALE AND OBJECTIVES

To evaluate the quality of images of the aorta and visceral arteries made at a high level of spatial resolution with thin slices and an optimized acquisition time by three-dimensional contrast-enhanced magnetic resonance angiography (3D CE-MRA).

MATERIALS AND METHODS

3D CE-MRA with a 1.4-mm slice thickness and 512-pixel base matrix was done on 62 consecutive patients with a 1.5-T magnetic resonance imaging MRI unit. A bolus test with a power injector was used to calculate the optimal scan delay time. For quantitative evaluation, the signal-to-noise ratio (SNR) was measured in 3 regions of interest. Qualitative image analysis was evaluated independently by two radiologists and graded on a scale of 0-3. Separate analyses were done for the aorta and distal visceral arterial branches.

RESULTS

The means SNR values were respectively 56.2 +/- 15.2 (mean +/- SD) for the aorta, 59.2 +/- 15.1 for the celiac trunk, and 57 +/- 15.2 for the superior mesenteric artery, with a homogeneous distribution (P = .99). Consistent enhancement was confirmed by the lack of statistically significant differences between the SNR values. The average score for vessel visualization on source images ranged from good to excellent for different segments. After post-processing of images, the average score for distal arterial segments was significantly improved. The overall agreement between the 2 reviewers in the visualization of definite artery segments was excellent (k = .91).

CONCLUSION

3D CE-MRA with a 512-pixel base matrix and thin slices can be applied in a reproducible way with excellent depiction and delineation of small vessels. Such a protocol could be used routinely.

Prevention of Contrast Media–induced Nephrotoxicity after Angiographic Procedures

Contrast medium-induced nephrotoxicity (ie, contrast nephrotoxicity [CN]) remains an important complication of angiographic procedures. If administration of iodinated contrast medium is deemed necessary in patients at high risk of CN, volume expansion should be offered and the lowest possible dose of nonionic isosmolar dimeric or nonionic low-osmolar monomeric contrast medium should be used. Prophylactic administration of fenoldopam or acetylcysteine has not offered consistent protection against CN. Intravenous acetylcysteine could be considered in emergency situations. Recently, sodium bicarbonate infusion has been shown to reduce the risk of CN. Hemofiltration for several hours before and after contrast medium injection may offer good protection against CN in patients with advanced renal disease. Prophylactic hemodialysis does not offer any protection against CN.

La perspective d’une étude dynamique des artères des membres inférieurs en IRM grâce à la séquence ECTRICKS

PURPOSE

This article presents a new MR angiography technique, Elliptic Centric Time Resolved Imaging on Contrast KineticS (ECTRICKS), which allows dynamic evaluation of the lower limb arteries opacification when venous return prevents adequate diagnostic evaluation of calf arteries.

PATIENTS AND METHODS

Comparative examinations could be compared. Additional arteries in 59 patients using a standard MRA technique and the ECTRICKS technique.

RESULTS

A total of 33 examinations could be compared. Additional arteries could be evaluated in 10% of our patient population using the ECTRICKS technique, and in 20% for our diabetic population. Arterial evaluation was better with the ECTRICKS technique in patients with diabetes and venous insufficiency.

CONCLUSION

ECTRICKS is a good complementary sequence for evaluation the calf arteries in patients with diabetes or early venous return.

Gadolinium contrast media are more nephrotoxic than a low osmolar iodine medium employing doses with equal X-ray attenuation in renal arteriography: an experimental study in pigs

RATIONALE AND OBJECTIVES

To investigate in a unilaterally nephrectomized porcine model whether gadolinium contrast media (Gd-CM) are less nephrotoxic than iodine media (I-CM) in x-ray arteriography of a kidney made temporarily ischemic by arterial balloon occlusion.

MATERIALS AND METHODS

In a noncrossover design, 3 mL of each test solution were injected in eight pigs (mean weight 19 kg) at a rate of 20 mL/min into the right renal artery at the start of a 10-minute period of ischemia. In group 1 (40 pigs) we injected 0.5 M gadopentetate, 0.5 M gadodiamide, 0.5 M iohexol (190 mg I/mL), 0.18 M iohexol (70 mg I/mL; with an x-ray attenuation equal to that of 0.5 M Gd-CM at 80 kV), and saline. In group 2 (24 pigs), we tested 0.18 M iohexol with ischemia and saline with and without ischemia. Gd- and iodine contrast media functioned as markers of glomerular filtration rate (GFR). When saline was tested, a low dose of iohexol (3 mL per pig; 300 mg I/mL) was injected as GFR marker intravenously in group 1 and into the renal artery in group 2. The plasma half-life elimination times of the CM 1-3 hours after injection were used to compare the effects of the different test solutions on GFR. Longer half-life means lower GFR.

RESULTS

Group 1: median plasma half-life elimination time of the GFR marker was 3 340 minutes after injection of 0.5 M gadopentetate, 256 after 0.5 M gadodiamide, 179 after 0.5 M iohexol, 143 after 0.18 M iohexol, and 133 minutes after saline. All differences except that between 0.18 M iohexol and saline were statistically significant (P < .01). Group 2: median plasma half-life was 174 minutes after 0.18 M iohexol with ischemia, 196 minutes after saline with ischemia, and 195 minutes after saline without ischemia. There were no significant differences between the test solutions in group 2 (P > .05).

CONCLUSION

In pigs, 0.5 M Gd-CM were more nephrotoxic than both equal-attenuating (70 mg I/mL) and equimolar (190 mg I/mL) concentrations of the I-CM iohexol. These results do not support the "off-label" use of Gd-CM for renal x-ray arteriography in man instead of commercially available concentrations of iodine contrast media at 140, 150 and 180 mg I/mL or diluted to 70 mg I/mL.

Magnetic resonance imaging of the peripheral vasculature

BACKGROUND

Atherosclerotic disease of the peripheral vasculature is a prevalent condition for which catheter-based techniques have been considered to be the gold standard for diagnosis. However, because of their invasive nature, these techniques inherently have the potential for complications. Non-invasive diagnostic techniques have historically been limited by low accuracy and high operator dependence. Magnetic resonance angiography (MRA) is a new approach that has diagnostic accuracy comparable with invasive angiography.

METHODS

The literature on MRA for evaluation of carotid, mesenteric, renal, and lower-extremity arterial disease was extensively reviewed. Helpful diagnostic algorithms on the basis of the literature are also provided.

RESULTS

MRA is both sensitive and specific when compared with invasive angiography for the evaluation of peripheral arterial disease and avoids the potential for complications resulting from arterial puncture and use of iodinated contrast.

CONCLUSION

Current MRA techniques are diagnostically robust and have proven to be a highly accurate, safe, and convenient means of diagnosing atherosclerotic disease of the peripheral vascular system.