Nephrotoxicity of high-dose gadolinium compared with iodinated contrast

Understanding Contrast Media

More than 10 million radiologic examinations requiring intravascular injection of iodinated contrast media are performed in the United States each year. Iodinated contrast media are considered to be safe diagnostic drugs, and the incidence of adverse reaction is low. However, as with any drug, the administration of contrast media is not without risk. Nurses involved in patient care should have some understanding of the properties and potential effects of iodinated contrast media.

Kidney transplantation: evaluation of donors and recipients

MR imaging provides a comprehensive method for noninvasive evaluation of renal donor anatomy. Although multidetector helical CT can provide similar information, MR imaging has the advantage of avoiding exposure to ionizing radiation and potentially nephrotoxic contrast material. These are important considerations in screening a generally healthy donor population. MR imaging also can provide complete evaluation of the kidney after transplantation, where avoidance of potentially nephrotoxic agents and preservation of maximal renal function are critical.

MR imaging of cystic renal masses

MR imaging has proven to be an important imaging modality in the evaluation of cystic renal masses. Because it is becoming more widely used, it is necessary to be able to characterize cystic renal masses accurately using MR imaging alone. We review the indications for the use of MR imaging and discuss the findings present in a variety of cystic renal masses. The role of MR imaging in the characterization of cystic lesions of the kidney is summarized and compared with the CT findings in the Bosniak renal cyst classification. It is expected that the increasing experience with the use of MR imaging in cystic renal masses will add to our ability to diagnose and manage these cases successfully.

Gadolinium-based contrast media compared with iodinated media for digital subtraction angiography in azotaemic patients

BACKGROUND

To determine whether gadolinium-based contrast media (CM) could be used safely for angiographies in patients with renal dysfunction we investigated renal function after gadobutrol exposure and compared the results with standard iodinated CM (iohexol) in a randomized clinical study.

METHODS

Twenty-one patients (aged 67+/-11 years, nine female and 12 male) with severely impaired renal function [mean serum creatinine 3.2+/-1.3 mg/dl, mean glomerular filtration rate (GFR) 31+/-16 ml/min/1.73 m(2)] who needed to have angiography because of severe peripheral vascular disease, renal artery stenosis or aortic aneurysms were randomized to receive in a blinded manner either gadobutrol (Gadovist 1.0 mmol/ml) or iohexol (Omnipaque 350) as contrast agents. GFR was measured by CM clearance (Renalyzer) at baseline and 48 h after CM administration. The primary end point was the mean change of GFR from baseline at 48 h, the secondary one the incidence of CM-induced acute renal failure, defined as a decrease in GFR of >50% from baseline within 48 h of CM administration.

RESULTS

In the gadobutrol group (n = 10) we observed a statistically significant decrease in GFR of 10.6+/-13.8 ml/min/1.73 m(2) within 48 h after CM administration (P<0.05, paired t test). The incidence of CM-induced ARF amounted to 50%. In comparison, the iohexol group (n = 11) also showed a statistically significant GFR reduction of 8.7+/-8.8 ml/min/1.73 m(2) (P<0.05, paired t test), and of ARF by 45%. The percentile of differences of GFR decreases between the two groups was not significant (P = 0.70). No patient demonstrated other adverse effects of gadobutrol or iohexol administration, apart from GFR reduction. Despite the decline in GFR, no patient required haemodialysis in the 10 following days.

CONCLUSIONS

In our study, gadolinium-based angiography showed no benefit over iohexol angiography with respect to preventing GFR reduction in patients with severely impaired renal function.

Cardiovascular magnetic resonance imaging

Recent advancements in magnetic resonance imaging hardware and software permit the assessment of cardiovascular structure and function at rest and during exercise or pharmacology-induced cardiac stress. With these developments, knowledge of cardiovascular imaging protocols in the magnetic resonance imaging environment is critical for nursing personnel. The purpose of this article is to review information pertinent to working in a magnetic resonance imaging environment and to describe the requirements of nursing personnel performing cardiovascular magnetic resonance imaging examinations.

Magnetic resonance imaging for planning aortic endograft procedures

Patients with aortic aneurysms and renal insufficiency are at an increased risk when conventional imaging modalities (contrast enhancing computed tomography and arteriography) are used for aortic endograft design. Magnetic resonance imaging (MRI) provides a nonionizing, noninvasive alternative to standard measurement techniques. Reliable diameter and length measurements can be obtained with MRI at a computer workstation without the use of iodinated radiologic contrast agents. The authors describe their experience with the use of magnetic resonance angiography as the sole imaging modality for aortic endograft design. Although not without limitations, MRI can be an effective measurement tool, particularly in patients who are at high risk of complications related to conventional imaging.

Model for Predicting the Impact of Gadolinium on Plasma Calcium Measured by the o-Cresolphthalein Method

Background: Gadolinium formulations, which are administered as contrast agents in magnetic resonance imaging examinations, interfere with colorimetric serum calcium determinations.

Methods: We performed an in vitro study to determine the extent to which three gadolinium formulations—gadodiamide (Omniscan), gadopentetate dimeglumine (Magnevist), and gadoversetamide (OptiMARK)—affect measurements by two methods that use o-cresolphthalein (Dade Behring, Inc. and Roche Diagnostics) and one that uses arsenazo dye (Equal Diagnostics). We also compared values from the o-cresolphthalein methods for 116 samples from patients administered gadodiamide.

Results: Magnevist did not affect any of the methods evaluated, whereas Omniscan and OptiMARK were identical in their effects. For the Dade method, the differences from the control sample were ≤4.0 and 7.0 mg/L at 0.25 and 0.5 mmol/L gadolinium, respectively. For the Roche method, the differences were 19, 9.0, and 5.0 mg/L at 0.5, 0.25, and 0.125 mmol/L gadolinium, respectively. Falsely increased calcium values were seen when samples were measured by the arsenazo-based method: differences were 6.0 and 3.0 mg/L at 1.0 and 0.5 mmol/L gadolinium. Using patient data collected at our institution, we were able to generate a model for predicting, from a patient’s glomerular filtration rate and the time elapsed since administration, the impact of Omniscan on calcium measurements by the o-cresolphthalein method from Roche Diagnostics.

Conclusions: The predictive model can be used to calculate, in patients who have received gadodiamide, the minimum length of time to wait before blood collection to avoid pseudohypocalcemia when the Roche o-cresolphthalein method is used.

Renal Tumours, Epidemiology and Diagnostic Profile

Our understanding of the natural history of renal cell carcinoma and the possibilities of new technologies are evolving and being integrated with advances in classification and staging. In this article we reviewed the literature in order to provide an analysis of the changing epidemiology of renal cell carcinoma.

Radiological evaluation of renal masses has rapidly progressed from conventional angiography and intravenous urography to ultrasounds, CT and MRI. As more patients are imaged for many opportunities, the incidental detection has increased. This article reviews the imaging and not techniques in order to characterize these lesions accurately.

Is half-dose contrast-enhanced three-dimensional MR angiography sufficient for the abdominal aorta and pelvis?

PURPOSE

To evaluate the usefulness of half-dose contrast-enhanced magnetic resonance (MR) angiography for depicting the abdominal aorta and its major branches.

MATERIALS AND METHODS

A total of 72 consecutive patients were randomly assigned to one of four groups that underwent MR angiography after receiving different concentrations (original or diluted to 50%) and total amounts (single or half-dose) of gadolinium chelate injected at different rates (1 or 0.5 mL/second). The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the abdominal aorta and of the common and external iliac arteries were calculated, and two blinded readers rated the respective image qualities.

RESULTS

The SNR and CNR of the abdominal aorta and the common iliac artery in the 0.5 mL/second groups were statistically significantly lower than those in the 1 mL/second groups. The differences in overall image quality across the four groups were not statistically significant.

CONCLUSION

Half-dose MR angiography using diluted contrast medium injected at a rate of 1 mL/second depicted the abdominal aorta and its branches as clearly as using a full single dose.

Gadolinium-enhanced computed tomography angiography in multi-detector row computed tomography

RATIONALE AND OBJECTIVES

The feasibility of using gadolinium contrast medium for computed tomography angiography (CTA) in multi-detector row computed tomography and the effect of contrast medium dilution was investigated.

MATERIALS AND METHODS

Three pigs were each scanned in multiple sessions with injections of non-dilute and dilute contrast medium at a dose of 0.3 mmol/kg body weight. Non-spiral dynamic scanning at a fixed mid-abdominal aortic level and thoracoabdominal CTA were performed.

RESULTS

The magnitude of peak aortic enhancement was not significantly different between dilute and non-dilute contrast medium injections (P = .88), but the former showed earlier enhancement (mean of 2.3 seconds sooner, P < .01) than the latter. CT angiography with gadolinium contrast medium showed much lower enhancement than iodine contrast medium, but small vessels were readily identifiable.

CONCLUSION

Gadolinium contrast medium combined with multi-detector row computed tomography may provide clinically useful CTA. Dilution of contrast medium shortens the enhancement time but has little effect on the magnitude.

Magnetic resonance portography using contrast-enhanced fat-saturated three-dimensional steady-state free precession imaging

PURPOSE

To assess the feasibility of contrast-enhanced fat-saturated three-dimensional steady-state free precession (FIESTA) imaging for contrast-enhanced magnetic resonance (MR) portography.

MATERIALS AND METHODS

Contrast-enhanced fat-saturated three-dimensional fast spoiled gradient-echo (SPGR) and FIESTA were performed as MR portography. In 10 cases, fat-saturated three-dimensional FIESTA was first performed and followed by fast SPGR, and the order of post-contrast imaging was reversed in the other 10 cases. Signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs) were estimated for portal and visceral veins on the source images. The visualization of portal vein was scored on three-dimensional MR portography. Portal venous system disorders were assessed using three-dimensional MR portography.

RESULTS

The SNRs, CNRs, and visual assessment of portal and visceral veins were significantly higher in contrast-enhanced fat-saturated three-dimensional FIESTA than contrast-enhanced fat-saturated three-dimensional fast SPGR (P < 0.05). The contrast-enhanced fat-saturated three-dimensional FIESTA provided high venous signals even at 8 minutes after gadolinium injection. The abnormalities of portal venous system were well visualized with MR portography using contrast-enhanced fat-saturated three-dimensional FIESTA.

CONCLUSION

Contrast-enhanced fat-saturated three-dimensional FIESTA was valuable for MR portography, with flexible time window and high vascular signals. This imaging may allow for other post-contrast imaging options before portography and release patients from consecutive breath-holds.

Contrast-enhanced MR angiography of the intracranial circulation

NCE MRA can provide the authors with useful diagnostic information in patients suffering from intracranial vascular disease, often leading to improved or altered treatment decisions. Most centers have used 3D TOF for evaluation of stroke-the most common cerebral vascular disease. Because of slow and disturbed flow, conventional 3D TOF MRA tends to overestimate stenotic lesions and occluded arteries and this can confound neurovascular assessment in stroke patients. Post contrast 3D TOF techniques provide a more robust and more specific method for imaging the intracranial circulation that overcomes the drawbacks of conventional 3D TOF. In the setting of acute ischemic stroke, the authors have found that the combination of conventional and CE 3D TOF MRA improves their overall diagnostic ability. Dynamic and time-resolved CE MRA techniques have evolved rapidly. Time-resolved CE MRA, in particular, is emerging as a useful technique for imaging dynamic vascular pathologies such as AVMs. Unfortunately, time-resolved MRA of the intracranial circulation provides images with low spatial resolution and is currently limited to subsecond frame rate 2D acquisitions, and less than 2 seconds frame rates for 3D acquisitions. Nevertheless, like in other vascular regions, CE MRA represents a milestone for non-invasive intracranial vascular imaging. The continuing development of CE MRA techniques and of new contrast agents will lessen the need for intra-arterial angiography in the future.

MR imaging in abdominal emergencies

The use of MR imaging in the emergency setting is evolving. Clear indications include situations in need of contrast media when iodinated contrast cannot be administered or to facilitate assessments in pregnant patients and children when exposure to ionizing radiation is considered unacceptable. The availability of rapid, motion-immune sequences now makes MR imaging a feasible study in less cooperative patients extending the range of patients for whom a diagnostic study can be achieved. Capitalizing on the unique benefits of MR imaging there is optimism that MR imaging can eliminate test redundancy and impact patient care in a cost-effective manner. Further investigations are needed to identify the diagnostic algorithms for which this favorable use holds true.

Gadolinium-enhanced MR Angiography as First-Line Preoperative Imaging in High-Risk Patients with Lower Limb Ischemia

PURPOSE

To assess the clinical relevance of gadolinium-enhanced MR angiography (Gd-MRA) as the first-line angiographic examination for planning lower limb revascularization in patients at high risk of complications after contrast arteriography (CA).

METHOD

Forty-five consecutive patients at high risk of post-CA complications because of chronic renal insufficiency, diabetes mellitus, advanced age, or the need for brachial artery catheterization or graft puncture had Gd-MRA as first-line angiography before a surgical or endovascular procedure for lower limb ischemia.

RESULTS

After Gd-MRA, 59 procedures were performed, including 38 surgical reconstructions, 17 endovascular procedures, and four amputations. Complementary CA was only required in seven patients for whom a below-knee bypass was planned. Cumulative patency rates at 1 and 24 months were, respectively, 91% and 91% for suprainguinal bypasses, 100% and 92% for infrainguinal above-knee bypasses, 80% and 57% for below-knee bypasses, and 92% and 76% for iliofemoral angioplasties. After 24 months of follow-up, limb salvage, amputation, and mortality rates were, respectively, 86%, 3.5%, and 7% for stage II ischemia and 48%, 11%, and 30% for stages III and IV.

CONCLUSION

Gd-MRA can be proposed for first-line preoperative imaging in the management of lower limb ischemia for patients at high risk and permits the selective use of CA as a second-line examination if a below-knee bypass is required.

Safety of contrast-enhanced MR angiography employing gadobutrol 1.0 M as contrast material

Our objectives were to evaluate the safety of intravenous 1.0-M gadobutrol injections in patients with an indication for contrast-enhanced magnetic resonance angiography (CE MRA) of supra-aortal, pelvic, or peripheral arteries by examining and assessing adverse events, laboratory values, vital signs and ECG findings for clinical significance. In 435 patients, recruited in three multicenter trials for safety evaluations of the new contrast agent 1.0-M gadobutrol, CE MRA was performed with 1.0- to 1.5-T scanners using three-dimensional gradient-echo sequences and phased-array coils. The study population comprised 312 men and 123 women with a mean age of 60.9 years. Two hundred seven patients had an indication for imaging of body arteries and 228 had an indication for imaging of peripheral arteries. Blood laboratory values and urinalysis results of 124 patients as well as heart rate, blood pressure, and 12-lead-electrocardiogram readings of 93 patients obtained during a follow-up period of up to 72 h after the injection of contrast media were available for safety analysis. Contrast media application was performed as intravenous bolus injection of 1.0-M gadobutrol in fixed doses according to the patients' body weight (b.w.) and indication for CE MRA and was followed by a 20- to 40-ml saline flush. Mean dose actually applied was 0.1 0.27 mmol/kg b.w. Flow rate ranged between 0.2 and 2.0 ml/s. Safety evaluations found a good tolerability with only 4.6% of at least "possibly related" adverse reactions and no clinically relevant changes in blood and urine samples including no transmetallation effect on serum zinc values. Analysis of renal tolerance showed no influence on renal function irrespective of preexisting renal impairment. The ECG analysis (rhythm analysis, pace-setting disturbances, conduction disturbances, and time interval measurements, including uncorrected and corrected QT) showed no clinically relevant effect of the injection of 1.0-M gadobutrol on the cardiac conduction system. Intravenous injection of 1.0-M gadobutrol at a dose of up to 0.1 0.27 mmol/kg b.w. in the indication CE MRA is safe and causes no clinically relevant changes in safety parameters such as heart rate, blood pressure, blood and urine laboratory values, and cardiac conduction system.

Helical computed tomography and magnet resonance imaging: diagnosis of pulmonary embolism in symptomatic patients

The diagnosis of pulmonary embolism is challenging because lung scanning is nondiagnostic in most patients and because pulmonary angiography is invasive. Advancements in computed tomography and magnetic resonance imaging have enabled visualization of pulmonary emboli. Studies using each of these modalities have demonstrated high sensitivity for lobar and segmental emboli and lower sensitivity for subsegmental emboli. A recent study of a management approach using spiral computed tomography combined with testing for deep vein thrombosis using compression ultrasonography was found to have high clinical validity. A number of different magnetic resonance imaging techniques have been used to identify pulmonary emboli, and no single technique has been shown to be superior. Further studies are needed to delineate the role of magnetic resonance imaging in the management of patients with suspected pulmonary embolism.

MR techniques for renal imaging

This article describes the principles, attributes, and pitfalls of the many MR imaging approaches available for assessment of renal-related disorders. Tables 1 and 2 summarize the specific approach and rationale.

Safety of gadolinium contrast angiography in patients with chronic renal insufficiency

OBJECTIVE

To prevent iodinated contrast medium-induced nephrotoxicity, gadolinium has been used increasingly for magnetic resonance angiography (MRA) or conventional digital subtraction angiography (DSA) to visualize arterial anatomy in patients undergoing vascular surgery who are considered at high risk because of chronic renal insufficiency. We assessed the safety of gadolinium-based contrast medium as a substitute for iodinated contrast medium-enhanced examinations. We determined the incidence of gadolinium-induced nephrotoxicity in a clinical setting and searched for contributing risk factors. Patients and methods In a single-center retrospective study from December 1999 to January 2001, 218 inpatients underwent MRA and 42 inpatients underwent DSA, with gadolinium as the sole contrast agent. Patient comorbid conditions, indications for vascular imaging, contrast dose, urine output, baseline and post-procedure serum creatinine concentration (SCr), and outcome were recorded for all patients in whom gadolinium-induced renal failure developed.

RESULTS

Of 260 patients who received gadolinium-based contrast agents, at a dose of 0.25 mmol/kg or more, 195 patients (75%) had pre-test baseline chronic renal insufficiency. In 7 of 195 patients (3.5%) acute renal failure developed after gadolinium-based contrast medium administration, for MRA (n = 153) in 3 patients (1.9%) and DSA (n = 42) in 4 patients (9.5%). Average baseline SCr in the 195 patients with chronic renal insufficiency was 38.2 +/- 1.6 mL/min/1.73 m(2), and in the 7 patients in whom acute renal failure developed, baseline SCr was 32.5 +/- 7.8 mL/min/1.73 m(2) (P =.33). Respective intravenous and intra-arterial gadolinium doses in these 7 patients ranged from 0.31 to 0.41 mmol/kg for MRA and 0.27 to 0.42 mmol/kg for DSA. Acute renal failure did not develop in any of 65 patients with normal baseline SCr.

CONCLUSION

Despite reports of negligible nephrotoxicity, rarely gadolinium-based contrast agents can cause acute renal failure in patients with underlying chronic renal insufficiency. Estimation of creatinine clearance alone does not enable prediction of which patients are likely to have acute renal failure. Patients at high-risk should be identified, and prophylactic measures should be taken to reduce the risk for nephrotoxicity.

Renal imaging for diagnosis and staging of renal cell carcinoma

The development and expansion of CT and MRI technology have enhanced the detection and characterization of renal lesions. Although these advancements should lead to earlier diagnosis of renal cell carcinoma with subsequent improved cure rates, the increased imaging has also uncovered many cases that are problematic not only in diagnosis but in management as well. The performance of high-quality examinations combined with growing experience should improve the ability to diagnose and manage these cases successfully. Continued advances in CT and MR technology combined with the current trend toward minimally invasive surgery will continue to expand the role of preoperative imaging and, it is hoped, improve the cure rate of renal cancer.

Virtual magnetic resonance colonography

Colorectal cancer screening has vast potential. Beyond considerations for cost and diagnostic accuracy, the effectiveness of any colorectal screening strategy will be dependent on the degree of patient acceptance. Magnetic resonance (MR) colonography has been shown to be accurate regarding the detection of clinically relevant colonic polyps exceeding 10 mm in size, with reported sensitivity and specificity values exceeding 95%. To further increase patient acceptance, strategies for fecal tagging have recently been developed. By modulating the signal of fecal material to be identical to the signal characteristics of the enema applied to distend the colon, fecal tagging in conjunction with MR colonography obviates the need for bowel cleansing. The review will describe the techniques underlying MR colonography and describe early clinical experience with fecal tagging techniques.

Gadodiamide administration causes spurious hypocalcemia

PURPOSE

To evaluate the prevalence of spurious hypocalcemia after gadodiamide-enhanced magnetic resonance (MR) imaging.

MATERIALS AND METHODS

Eight hundred ninety-six inpatients with available serum calcium data obtained before and after gadodiamide-enhanced MR imaging were identified. Changes in serum calcium measurements following gadodiamide administration in 1,049 MR imaging examinations performed in these patients were correlated with gadodiamide dose, renal function, and time between gadodiamide administration and phlebotomy.

RESULTS

Following 42 gadodiamide-enhanced examinations, serum calcium measurements spuriously decreased by more than 2 mg/dL (0.5 mmol/L), resulting in laboratory reports of "critical" hypocalcemia (ie, calcium level < 6 mg/dL [1.5 mmol/L]) in 25 examinations. These reduced calcium measurements were correlated with serum creatinine level (r = 0.39, P <.001), gadodiamide dose (r = 0.37, P <.001), and time between gadodiamide injection and phlebotomy (r = -0.28, P <.001). Spurious reductions in calcium measurements after administration of 0.1 mmol of gadodiamide per kilogram of body weight were greater in patients with renal insufficiency (0.6 mg/dL [0.15 mmol/L] +/- 0.5 [0.125, SD]) than in those with normal renal function (0.14 mg/dL [0.035 mmol/L] +/- 0.4 [0.1]) (P <.001). After administration of more than 0.2 mmol/kg of gadodiamide, spurious calcium measurement decreases were greater in patients with renal insufficiency (2.4 mg/dL [0.6 mmol/L] +/- 3.6 [0.9]) than in those with normal renal function (0.4 mg/dL [0.1 mmol/L] +/- 0.7 [0.175]) (P <.001). Patients with renal insufficiency had spuriously low calcium measurements up to 4(1/2) days after gadodiamide administration. Seven patients were inappropriately treated with intravenous calcium and eleven with oral calcium in response to false-positive laboratory reports of critical hypocalcemia. No patient had characteristic symptoms of hypocalcemia or injuries attributed to the inappropriate medical treatment.

CONCLUSION

Gadodiamide administration causes spurious hypocalcemia, particularly at doses of 0.2 mmol/kg or higher and in patients with renal insufficiency.

Using a 1 M Gd-chelate (gadobutrol) for total-body three-dimensional MR angiography: preliminary experience

PURPOSE

To determine whether higher concentrated gadolinium chelates are advantageous for the recently introduced concept of total-body magnetic resonance angiography (MRA), allowing whole-body coverage, extending from the carotid arteries to the runoff vessels, in merely 72 seconds.

MATERIALS AND METHODS

Total-body three-dimensional (3D) MRA using a 1 M Gd-chelate (gadobutrol, Gadovist, Schering, Berlin, Germany) at a dosage of 0.2 mmol/kg body-weight (biphasic injection protocol: 1.3 mL/second and 0.7 mL/second) was performed on three healthy volunteers and ten consecutive patients with DSA-documented peripheral vascular disease. Separated by at least 72 hours, the three healthy volunteers also underwent the same MRA-protocol, using gadopentetate dimeglumine in equimolar dosages.

RESULTS

Compared to equimolar dosages, mean signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) values in the three volunteers were significantly higher (up to 32.5% for the arteries of the thighs and calves) using gadobutrol. In the ten patients, gadobutrol-based total-body MRA accurately assessed significant stenoses (luminal narrowing > 50%) with sensitivities and specificities of 96.2% (95% CI 0.83-0.97) and 95.7% (95% CI 0.84-0.96), respectively, compared to digital subtraction angiography.

CONCLUSION

The MRA image quality for total-body MRA provided by the administration of gadobutrol is superior to that obtained following administration of an identical dose of gadopentetate dimeglumine, and therefore shows promise for use as a comprehensive single exam assessing the entire arterial system for the presence of atherosclerotic disease manifestations.

1-molar gadobutrol as a contrast agent for computed tomography: results from a comparative porcine study

RATIONALE AND OBJECTIVES

To evaluate prospectively the efficacy of gadobutrol as contrast agent for computed tomography (CT) compared with iodinated contrast media in a porcine animal model.

METHODS

In 8 domestic pigs (35 +/- 4 kg body weight [BW]), continuous spiral CTs of the chest and abdomen were performed using either 2 mmol/kg BW Gadovist 1.0 (1 mol/L gadobutrol) intravenously or Ultravist (300 mg I/mL iopromide) (slice 5 mm, table feed 7.5 mm, reconstruction increment 5 mm). One week later, the same animals were examined using the same protocol with the other contrast agent. In 2 additional animals, serial CTs were performed at the same level using gadobutrol or iopromide on day 1 and the alternate agent on day 8 inches order to determine contrast media kinetics, peak enhancement, and time enhancement-product in important vascular regions and parenchymal organs (abdominal aorta, inferior vena cava, liver, and renal parenchyma). Peak enhancement (net increase compared with nonenhanced baseline values) was measured in Hounsfield units (HU) in defined regions of interest.

RESULTS

In vivo, the mean peak enhancement 5, 15, 30, and 120 seconds in the abdominal aorta after injection of 2 mL/kg BW gadobutrol and iopromide was 200 +/- 11, 224 +/- 10, 261 +/- 13, and 95 +/- 9 HU versus 232 +/- 10, 298 +/- 10, 152 +/- 11, and 123 +/- 10 HU, respectively. Differences in enhancement of vascular structures was statistically significant (P < 0.05) in carotid arteries (235 +/- 20 HU for gadobutrol and 264 +/- 19 HU for iopromide) and the aortic arch (261 +/- 14 HU for gadobutrol and 279 HU +/- 13 HU for iopromide). No statistical significance was seen in all other measured vascular structures and parenchymal organs.

CONCLUSION

Contrast-enhanced CT with 1 mol/L gadobutrol in a dose of 2 mmol/kg BW resulted in an excellent vascular and parenchymal enhancement in most vascular regions and parenchymal organs similar to an equivalent volume of 300 mg/mL iodinated contrast media.

Stenosis detection in forearm hemodialysis arteriovenous fistulae by multiphase contrast-enhanced magnetic resonance angiography: preliminary experience

PURPOSE

To assess the feasibility and accuracy of multiphase contrast-enhanced magnetic resonance angiography (CE-MRA) in patients with dysfunctioning hemodialysis arteriovenous fistulae (AVF), using digital subtraction angiography (DSA) as the standard of reference.

MATERIALS AND METHODS

Fifteen patients with dysfunctioning AVF (eight radiocephalic and seven graft AVF) underwent CE-MRA. Dysfunction was defined as a flow decline of more than 25% in 1 month measured by dilutional flow measurements. CE-MRA was performed during injection of 35 mL of gadolinium-DTPA. The CE-MRA sequence consisted of a time-resolved series of 10 scans, each lasting approximately 10 seconds. The technical parameters were TR/TE/FA/voxel = 5.4/1.6/40/3.1 mm(3), and a rectangular surface reception coil was used. All patients were scheduled to undergo DSA at which an intervention was carried out when a stenosis >or=50% was seen. Two observers, unaware of each other's findings and the findings at DSA, quantified the number and degree of stenosis in the failing AVF. Image quality for CE-MRA and DSA was scored on a 3-point scale. The diagnostic performance of CE-MRA was analyzed with receiver-operator characteristic (ROC) analysis.

RESULTS

CE-MRA and DSA examinations were performed without side effects in all 15 patients. Image quality was scored significantly better on CE-MRA (observer 1: CE-MRA, 2.0; DSA, 1.3; P =.001; observer 2: CE-MRA, 2.0; DSA, 1.4; P =.002). Interobserver agreement for detection of >or=50% stenosis was 0.81 (95% confidence interval (CI) = 0.71-0.92) for CE-MRA and 0.69 (95% CI = 0.55-0.84) for DSA. ROC analysis revealed a mean area under the curve of 0.78. On the patient level, at the >or=50% threshold, mean sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were 100% (95% CI = 69%-100%), 10% (95% CI = 0%-78%), 70% (95% CI = 38%-92%), and 100% (95% CI = 50%-100%), respectively. At the >or=75% threshold, mean sensitivity, specificity, PPV, and NPV were 75% (95% CI = 20%-99%), 78% (95% CI = 39%-98%), 55% (95% CI = 12%-96%), and 89% (95% CI = 52%-100%), respectively.

CONCLUSION

CE-MRA is a useful diagnostic tool for detecting stenoses in flow-declined hemodialysis AVF prior to interventional DSA.

MR imaging of the kidneys and adrenal glands

By performing a comprehensive MR imaging examination, it is not only possible accurately to characterize and stage cystic and solid lesions of the kidney, but also to provide important preoperative information to the surgeon. In addition, MR imaging can characterize many adrenal lesions and frequently can obviate the need to obtain biopsies. The continued development and growth of MR technology combined with the current trend toward minimally invasive surgery will expand the role of MR imaging in the future.

Fat-suppressed three-dimensional MR angiography technique with elliptical centric view order and no prolonged breath-holding time

PURPOSE

To determine the appropriate rate of fat-suppression pulses (using spec IR-spectral selective inversion recovery) for fat-suppressed 3D magnetic resonance angiography (MRA) with an elliptical centric view order.

MATERIALS AND METHODS

In abdominal 3D fast spoiled gradient echo (fast SPGR) with an elliptical centric view order, the spec IR pulse rate was changed from zero to one every 15 repetitions (in nine steps) in eight volunteers. In the equilibrium phase, abdominal contrast-enhanced 3D MRA was obtained by 3D fast SPGR using an elliptical centric view order without fat-suppression and with two spec IR, and by fat-suppressed 3D fast SPGR with a sequential-centric view order (efgre3D) in 18 cases. Fat and vascular signals were estimated.

RESULTS

Although 3D fast SPGR using an elliptical centric view order with spec IR placed every 15 TR and efgre3D effectively decreased fat signals, these sequences lengthened the breath-hold by 4-6 seconds compared with non-fat-suppressed sequence. 3D fast SPGR using an elliptical centric view order and two spec IR reduced the fat signal by 30% and provided good 3D MR angiography without substantial prolongation of breath-hold.

CONCLUSION

Two spec IR can be used for generation of partially fat-suppressed abdominal 3D MRA without prolongation of the breath-hold when performing 3D fast SPGR using an elliptical centric view order.

Hemodialysis access imaging: comparison of flow-interrupted contrast-enhanced MR angiography and digital subtraction angiography

PURPOSE

To compare flow-interrupted contrast material-enhanced magnetic resonance (MR) angiography with conventional digital subtraction angiography (DSA) for hemodialysis access imaging.

MATERIALS AND METHODS

Twenty-two accesses (14 arteriovenous grafts [AVGs], eight arteriovenous fistulas [AVFs]) in 18 consecutive patients were imaged with flow-interrupted contrast-enhanced MR angiography and subsequent conventional DSA. MR image quality was assessed as excellent, good, or nondiagnostic. Anastomotic diameters in AVGs and postanastomotic diameters in AVFs were measured in consideration of an adjacent normal segment. Reductions in the diameter of the lumen and interobserver differences were analyzed with method comparison as described by Bland and Altman and expressed as the mean difference with its 95% confidence limits (CLs) (mean +/- 2 SDs).

RESULTS

Image quality obtained with flow-interrupted contrast-enhanced MR angiography was considered excellent in 73% (16 of 22) and good in 23% (5 of 22). Method comparison analysis between MR angiography and DSA indicated a mean difference of 3.2% (95% CLs: -26.7%, 33.1%) for observer 1 and 4.1% (95% CLs: -23.8%, 32.1%) for observer 2. Interobserver analysis at MR angiography indicated a mean difference of 3.2% (95% CLs: -28.8%, 35.2%), and that at DSA indicated a mean difference of 3.6% (95% CLs: -9.4%, 16.7%).

CONCLUSION

Image quality and anatomic depiction with flow-interrupted contrast-enhanced MR angiography and with DSA were comparable.

Gadolinium-enhanced multidetector CT angiography of the thoracoabdominal aorta

A 93-year-old patient with a cardiac pacemaker and biochemical renal failure presented with back pain suspicious for dissection. We performed gadolinium-enhanced thoracoabdominal multidetector CT angiography using eight-channel multidetector CT. Uniform aortic enhancement of 140 HU was sufficient to exclude aortic dissection and defined an unruptured infrarenal abdominal aortic aneurysm.

Gadolinium-enhanced digital subtraction angiography of hemodialysis fistulas: a diagnostic and therapeutic approach

OBJECTIVE

The aim of our study was to evaluate the feasibility, safety, and potential role of the contrast agent gadoterate meglumine for digital subtraction angiography as a single diagnostic procedure or before percutaneous transluminal angioplasty of malfunctioning native dialysis fistulas.

MATERIALS AND METHODS

Over a 20-month period, 23 patients (15 women, eight men) with an age range of 42-87 years (mean, 63 years) having end-stage renal insufficiency and with recent hemodialysis fistula surgical placement underwent gadoterate-enhanced digital subtraction angiography with a digital 1024 x 1024 matrix. Opacification was performed on the forearm, arm, and chest with the patient in the supine position using an injection (retrograde, n = 14; anterograde, n = 8; arterial, n = 1) of gadoterate meglumine into the perianastomotic fistula segment at a rate of 3 mL/sec for a total volume ranging from 24 to 32 mL. Percutaneous transluminal angioplasty was performed in three patients and required an additional 8 mL per procedure. Examinations were compared using a 3-step confidence scale and a two-radiologist agreement (Cohen's kappa statistic) for diagnostic and opacification quality. Tolerability was evaluated on the basis of serum creatinine levels and the development of complications.

RESULTS

No impairment of renal function was found in the 15 patients who were not treated with hemodialysis. Serum creatinine level change varied from -11.9% to 11.6%. All studies were of diagnostic quality. The presence of stenosis (n = 14) or thrombosis (n = 3) in arteriovenous fistulas was shown with good interobserver agreement (kappa = 0.71-0.80) in relation to opacification quality (kappa = 0.59-0.84). No pain, neurologic complications, or allergiclike reactions occurred. Three percutaneous transluminal angioplasty procedures (brachiocephalic, n = 2; radiocephalic, n = 1) were successfully performed.

CONCLUSION

Gadoterate-enhanced digital subtraction angiography is an effective and safe method to assess causes of malfunction of hemodialysis fistulas. It can also be used to plan and perform percutaneous transluminal angioplasty.

Endovascular aortic aneurysm repair in patients with renal dysfunction or severe contrast allergy: utility of imaging modalities without iodinated contrast

Contrast-enhanced imaging studies are required for preoperative evaluation in patients undergoing endovascular aortic aneurysm repair; however, the use of iodinated contrast agents may not be suitable in patients with renal dysfunction or severe contrast allergy. The objective of this study was to evaluate the utility of imaging modalities without iodinated contrast in patients undergoing endovascular aortic aneurysm repair. A total of 297 patients underwent endo vascular repair of abdominal aortic aneurysms during a 6-year period ending in August 2001. Among them, 20 patients (6.2%), who underwent imaging studies without iodinated contrast because of either renal dysfunction or severe contrast allergy formed the basis of this study. Multiple non-iodinated contrast imaging studies were used, including gadolinium-enhanced magnetic resonance angiography (MRA), non-contrast computed tomography (CT), gadolinium or carbon dioxide (CO2) aortography, and intravascular ultrasound (IVUS). Hospital records were reviewed to evaluate the imaging study, renal function, perioperative morbidity, and clinical outcome of endo vascular aortic aneurysm repair. From the results of our study we concluded that endovascular aortic aneurysm repair can be performed safely in patients with renal dysfunction or severe contrast allergy utilizing non-iodinated contrast-based imaging modalities. IVUS is a useful intraoperative imaging modality, and postoperative endoleak surveillance can be performed using duplex ultrasound scanning to avoid risk of iodinated contrast exposure.

MR angiography of the renal arteries

During, the past decade. MRA has evolved from an cxperimental technique into the modality of choice for the noninvasive evaluation of renovascular disease. The recent widespread application of MRA for these indications has been driven primarily by the advent of 3D contrast-enhanced MRA. which provides a fast, reliable technique for imaging large vascular territories and generates images, after postprocessing, similar in appearance to digital subtraction angiography. The cross-sectional volumetric nature of contrast-enhanced MRA affords some advantages over conventional catheter angiography. Although 3D contrast-enhanced MRA forms the backbone of vascular MR studies, several adjunctive sequences are employed to maximize the diagnostic yield of the examination. For example. flow-dependant imaging is used to complement the morphologic images of contrast-enhanced MRA by providing hemodynamic information. As such, MRA is unique among noninvasive imaging modalities in that it offers a comprehensive evaluation of anatomy and function. The availability and reliability of MRA extend renal artery screening to a wider spectrum of patients. Current applications of renal MRA range from detection of renal artery stenosis to evaluation for renal transplant donors.

Imaging of aortic stent-grafts and endoleaks

Although the technical success of stent-graft implantation is established and relatively safe, data on the long-term safety and efficacy of endovascular repair are just emerging. Because several late complications of aortic stent-graft placement have been observed, life-long follow-up remains essential. Imaging methods form an integral part of every stage of endovascular aortic aneurysm repair. The current imaging strategy should include initial plain films, CT angiography, and color-coded Duplex sonography. Plain films are an excellent means to detect migration, angulation, kinking, and structural changes of the stent mesh, including material fatigue, at follow-up. Helical CT angiography is considered a potentially revolutionary method for the noninvasive complete postprocedural assessment of aortic sten-grafting. Current data justify the use of biphasic C angiography as the postprocedural imaging technique of choice in most patients [118]. Ultrasound offers the advantages of low cost and lack of radiation exposure. High-quality ultrasound reliably excludes endoleaks in patients after stent-grafting of AAAs. There is a substantial variability, however, in measuring the diameter of aneurysm sacs; thus, confirmation using an alternative study is prudent in cases that demonstrate a significant change in size during follow-up. MR angiography serves as an attractive alternative to CT angiography in patients with impaired renal function or known allergic reaction to iodinated contrast media. With current techniques, the visualization of aortic stent-grafts (with the exception of stainless-steel-based devices) is sufficient with MR angiography. There is evidence that MR imaging is superior to CT angiography in detecting small type 2 endoleaks or for excluding retrograde perfusion in patients with suspected endotension. The role of diagnostic catheter angiography is limited to assessment of vascular pathways in equivocal cases or for suspected endotension. Currently, a consensus view about postprocedural management after aortic stent-graft implantation is lacking. The authors propose performing a baseline CT angiography at discharge and a biphasic CT angiography and Duplex ultrasound scan at three months. In patients with no evidence of an endoleak, CT angiography, plain film and Duplex sonography (abdomen) should be repeated every year after endovascular repair. If an endoleak is present at follow-up, immediate appropriate treatment should be initiated.

Gadolinium-based contrast agents in angiography and interventional radiology

Gadolinium is useful as an alternative contrast agent for diagnostic angiographic and interventional procedures in patients with renal insufficiency or a history of a severe reaction to iodinated contrast material. Gadolinium usually is used as a "problem solver" to answer specific diagnostic questions or guide interventional procedures that cannot adequately be defined with CO2 angiography. Because of dose limitations with Gd, careful planning is required prior to its use with angiography or interventional procedures.

Magnetic resonance imaging of the multiple-ligament injured knee

OBJECTIVE

To evaluate magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) in detecting soft tissue, neurovascular, and bony injury after multiple ligament knee injury, including knee dislocation.

MATERIALS AND METHODS

A retrospective search was performed for patients presenting with reported knee dislocation from May 1993 through May 2000 who underwent both MRI and surgical reconstruction. Twenty-one patients met these criteria (15 men and six women; age range 14 to 75 years; mean 32.6 years). Magnetic resonance diagnoses of soft tissue and bony injury were compared with the patients' operative findings. MRA of the popliteal vessels was performed in seventeen of our twenty-one patients, and the results of these studies are described.

RESULTS

Multiple ligamentous, tendinous, meniscal, chondral, osseous, and neural injuries were seen. There was excellent correlation (kappa > 0.8) between the magnetic resonance and operative findings with regard to the size and location of tears. Regarding meniscal tears, the type (e.g., bucket, radial split, meniscocapsular separation) and location correlated well with surgery. All ten nerve injuries noted on magnetic resonance were confirmed at surgery. Six of our patients had both conventional angiograms and MRAs with 100 percent agreement between the studies. In one patient an intimal flap in the popliteal artery was seen on MRA and confirmed on conventional angiographic images.

CONCLUSION

MRI is an accurate method of assessing soft tissue, osseous, and neural damage after knee dislocation. Our early experience with popliteal fossa MRA is encouraging with complete agreement between the MRA and conventional angiography in patients who had both studies.

Are gadolinium-based contrast media really safer than iodinated media for digital subtraction angiography in patients with azotemia?

Gadolinium chelates, intended as intravenous contrast media for magnetic resonance imaging, have been regarded as nonnephrotoxic and recommended to replace iodinated contrast media in patients with azotemia who are undergoing digital subtraction angiography (DSA). High intraarterial doses (up to 220 mmol of gadodiamide) have been used, with a 40% incidence of nephropathy. The authors discourage the use of gadolinium for DSA for several reasons. (a) There exist no randomized studies comparing the nephrotoxic effects of gadolinium-based and iodinated media at equal-attenuating concentrations and doses. (b) Gadolinium-based media are hypertonic, a pathogenetic factor in contrast medium-induced nephropathy after renal angiography, with an osmolality two to seven times that of plasma. Iodinated media in concentrations that are equally attenuating with gadolinium-based media can be made isotonic. (c) In vitro measurements indicate that 0.5 mol/L gadolinium chelates are equally attenuating with 60-80 mg iodine per milliliter at the commonly used 70-90-kV range used for DSA. Thus, 50 mL of 0.5 mol/L gadolinium chelate ( approximately 0.3 mmol/kg in an 80-kg person) would be equally attenuating with a dose of 3-4 g of iodine in an iodinated medium (eg, 50 mL iohexol at 60-80 mg I/mL or 10-13 mL at 300 mg I/mL). (d) By combining these data on attenuation and results of toxicity studies in mice, the general toxicity of gadolinium chelates may be six to 25 times higher than that of equal-attenuating doses of iodinated media at 70-kV DSA. Thus, the authors believe that at equal-attenuating doses for DSA, modern iodinated contrast media should result in a lower toxic load on the body than with presently available gadolinium chelates.

Gadolinium chelates in angiography and interventional radiology: a useful alternative to iodinated contrast media for angiography

Gadolinium has physical properties that are well suited for radiographic imaging. Digital subtraction angiography with a gadolinium chelate as contrast medium can provide images of suitable quality for diagnosis and intervention. The overall safety profile of gadolinium-based contrast media is excellent. In particular, these contrast media are well tolerated in patients with renal insufficiency when administered intraarterially in doses of less than 0.3-0.4 mmol per kilogram body weight, with a decreased incidence of contrast medium-induced nephropathy, as compared with similar volumes of iodinated contrast material. The currently available formulations of gadolinium chelates can be injected safely into every arterial and venous structure. However, substantial data are lacking on the intraarterial use of gadolinium in patients with renal insufficiency, particularly at doses that exceed those routinely used in magnetic resonance angiography. Gadolinium chelates in appropriate volumes are useful alternative contrast media in selected high-risk patients undergoing angiographic studies.

MR colonography with barium-based fecal tagging: initial clinical experience

PURPOSE

To assess a strategy for fecal tagging with barium sulfate as an inexpensive tagging agent in conjunction with magnetic resonance (MR) colonography in patients suspected of having colorectal lesions.

MATERIALS AND METHODS

Twenty-four patients suspected of having colonic lesions because of rectal bleeding, positive fecal occult blood test results, or altered bowel habits underwent MR colonography and subsequent conventional colonoscopy. A 200-mL dose of a barium sulfate-containing contrast agent was ingested with each of four low-fiber meals, beginning 36 hours before the examination. For MR colonography, the colon was filled with tap water. Gadobenate dimeglumine was injected intravenously. Images were acquired 75 seconds after gadobenate dimeglumine administration by using only a T1-weighted three-dimensional gradient-echo sequence. Images were reviewed by two radiologists blinded to conventional colonoscopic data. By using colonoscopy as the reference standard, sensitivity and specificity of MR colonography were determined for detecting colorectal masses.

RESULTS

On the basis of MR colonography, 15 polyps of 5-20 mm and 10 carcinomas were detected and later confirmed with conventional colonoscopy. Conventional colonoscopy depicted three additional lesions less than 8 mm in diameter. Thus, sensitivity of MR colonography was 89.3% (25 of 28) for lesions and 91.7% (22 of 24) for patients.

CONCLUSION

Barium-tagged MR colonography obviates bowel cleansing and depicts all lesions exceeding 8 mm in diameter.

Right-lobe living related liver transplantation: evaluation of a comprehensive magnetic resonance imaging protocol for assessing potential donors

The purpose of this study was to determine the practicability and diagnostic accuracy of a magnetic resonance (MR) protocol capable of replacing computed tomography, catheter angiography, and endoscopic retrograde cholangiopancreatography for the presurgical evaluation of potential liver donors before right hepatectomy. MR imaging (MRI) was performed on a 1.5 T scanner using a phased-array torso surface coil for signal reception. The following image sets were collected: axial two-dimensional (2D) T1-weighted fast low angle shot (FLASH), axial 2D T2-weighted half-Fourier acquisition single-shot turbo-spin-echo (HASTE) with fat saturation, coronal MR cholangio-pancreatography (MRCP) based on 2D multisection HASTE and single-section single-shot rapid acquisition with relaxation enhancement (RARE) imaging, dynamic contrast-enhanced three-dimensional (3D) FLASH, and contrast-enhanced T1-weighted FLASH. 3D FLASH data sets were collected before and after an intravenous administration of Multihance (gadobenate dimeglumine, Gd-BOPTA; Bracco, Milano, Italy), 0.2 mmol/kg of body weight. Thirty-eight potential liver donors were assessed by means of MRI. Twenty patients also underwent digital subtraction angiography (DSA). Of these, 16 patients underwent liver harvesting. MR angiography (MRA) data sets correlated with DSA results, and MRCP results correlated with intraoperative findings. Patients were excluded as potential donors based on insufficient liver mass of the left hepatic lobe (n = 5) or presence of hepatic pathological states (n = 9) seen at MRI, such as hemangiomas, focal nodular hyperplasias, or hepatic steatosis. MRCP showed the biliary system to the level of the first hepatic side branch. Dilated ducts were present in 4 patients. MRA depiction of hepatic arterial morphological characteristics correlated with catheter angiography results in all 20 patients: Three left hepatic arteries originating from the left gastric artery, three aberrant right hepatic arteries originating from the superior mesenteric artery, and two aberrant origins of both hepatic arteries and one common hepatic artery originating from the superior mesenteric artery were correctly identified on MRA. Similarly, the portal venous system was fully assessed on MRA. A comprehensive assessment of the hepatic parenchyma, biliary and pancreatic ductal system, and hepatic arterial, portal, and venous systems can be accomplished using the outlined protocol.

Using highly concentrated gadobutrol as an MR contrast agent in patients also requiring hemodialysis: safety and dialysability

OBJECTIVE

The purpose of our study was to assess the safety and dialysability of gadobutrol, a new, electrically neutral, and highly concentrated MR contrast agent, in patients who require hemodialysis.

SUBJECTS AND METHODS

Eleven patients with end-stage renal failure who required ongoing hemodialysis were enrolled in our prospective study. Gadobutrol (1 mol/L) was injected IV at randomly assigned doses of either 0.1 or 0.3 mmol of gadolinium per kilogram of body weight for contrast-enhanced MR imaging. Hematology, clinical chemistry, and vital signs were closely monitored at baseline and during an observation period of 120 hr after the IV injection of gadobutrol. To calculate the dialysability, blood samples were drawn before and after each of three hemodialysis sessions. Additional arterial and venous blood sampling was performed during the first hemodialysis session after 30 and 90 min.

RESULTS

No gadobutrol-related changes in hematology, clinical chemistry, or vital signs were detected at either dose level during the observation period. The mean and the standard deviation for the eliminated fraction of gadobutrol was 68.2% +/- 12.7% after a 3-hr hemodialysis session using a 1.2 m(2) low-flux polysulfone membrane. After three consecutive hemodialysis sessions, the total amount of gadobutrol eliminated increased to 98.0% +/- 1.8%. The mean clearance rates of gadobutrol were 126.1 +/- 17.8 mL/min and 126.6 +/- 24.5 mL/min at 30 and 90 min, respectively.

CONCLUSION

Gadobutrol is effectively removed by three hemodialysis sessions using a low-flux polysulfone membrane. Our study documents initial evidence that gadobutrol can be used safely in hemodialysis patients.

Use of gadolinium-based contrast agent for renal angiography: case report and review of the literature

A 67-year-old woman suffering from chronic renal failure (Creatinine 480 micromol/L) underwent a gadolinium renal angiography, which visualized a stenosis of the right renal artery. There was no deterioration of renal function after the arteriography. A review of the literature is presented which show the efficiency of this technique to visualize the renal arteries, and the absence of nephrotoxicity after the use of gadolinium as a based contrast agent in high risk patients.

0.5 M Gd chelate (Magnevist) versus 1.0 M Gd chelate (Gadovist): dose-independent effect on image quality of pelvic three-dimensional MR-angiography

To compare the effect on image quality of a 1.0 M gadolinium (Gd) chelate to that of a conventional 0.5 M Gd chelate, five healthy volunteers and seven patients with angiographically documented aorto-iliac disease underwent a mono-station three-dimensional magnetic resonance angiography (MRA) exam (Siemens SONATA, Erlangen, Germany) twice, once using Gadovist 1.0 and the other time using Magnevist as the contrast agent. All subjects received a fixed volume of Gadovist 1.0, corresponding to a dose between 0.1 and 0.15 mmol/kg body weight followed by a saline flush. For the Magnevist exam, the contrast agent volumes and flow rates were doubled. For both quantitative and qualitative analysis of the angiographic data sets, the arterial tree was divided into nine segments. 1 M Gadovist 1.0-enhanced three-dimensional MRA data sets were characterized by significantly higher signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) values compared to 0.5 M Magnevist-enhanced images. The data revealed mean SNR/CNR increases exceeding 70% (P < 0.01). Although there was no statistically significant difference in the rating of image quality (P > 0.05), the Gadovist 1.0 exam led to better delineation of the arterial morphology, especially of small vessels.

Peripheral vascular surgery and magnetic resonance arteriography--a review

OBJECTIVES

to review the current status of lower limb MRA.

DESIGN

a literature review based predominantly on a MEDLINE database search of English-language publications from January 1991 to October 2000.

MATERIALS AND METHODS

twenty-eight articles, concerning non-enhanced MRA (13), gadolinium-enhanced MRA (14) or both (1), met the predefined requirement for quality. Results gadolinium-enhanced MRA (CE-MRA) seems to be more accurate, quicker and associated with fewer problems than non-enhanced (TOF) MRA. TOF-MRA has a sensitivity and specificity of 93% (range 64-100%) and 88% (range 57-100%) respectively, and CE-MRA presents values of 96% (range 71-100%) and 96% (63-100%), respectively, using conventional arteriography as the gold standard. Some articles report a substantial incidence of runoff vessels suitable for distal bypass visible on MRA but invisible on conventional arteriography. Gadolinium contrast is given intravenously and is generally well tolerated and has no known nephrotoxicity.

CONCLUSION

CE-MRA is accurate compared to conventional arteriography, has the potential to increase the limb salvage rate for selected patients, is non-invasive and well tolerated.