Enhancement of hepatic parenchyma, aorta, and portal vein in helical CT: comparison of iodixanol and iopromide

Comparison of allergic adverse effects and contrast enhancement between iodixanol and iopromide

Background

Iodinated X-ray contrast media are the most commonly used contrast agents in the world with an annual application of 40-50 million. New non-ionic contrast agents are subdivided into low osmolar agents such as iopromide and iso-osmolar agents such as iodixanol. Regarding different biochemical characteristics, these agents are different in the allergic reactions and contrast enhancement and final lesion conspicuity.

Objectives

This study was carried out to compare allergic adverse effects and contrast enhancement between iodixanol and iopromide.

Patients and Methods

One-hundred and twenty patients who were referred for abdominal CT scan to Besat Hospital were included in this study. Patients were randomly divided into two groups (A and B). Group A received 100 cc iodixanol (300 mgI/mL) and group B received 100 cc iopromide (300 mgI/ml) by power injector. CT examination was performed using Helical CT Scanner (Somatom, Siemens, Germany). Sixty seconds after injection, images were obtained and enhancement of port, liver and aorta were determined. Allergic adverse effects were recorded one hour and up to one week after injection.

Results

Iodixanol produced a significantly greater enhancement of the hepatic, aorta and portal vein than iopromide (P < 0.01). Sixty seconds after injection, associated pain and heat sensation were less frequent in iodixanol in comparison with iopromide (P = 0.03). Immediate reactions such as nausea and vomiting were less frequent in iodixanol (P = 0.01). Late skin reactions such as rash was more frequent in iodixanol (P < 0.01).

Conclusions

Iodixanol is safe and is better tolerated in the early phase of injection with better contrast enhancement and lesion conspicuity. Mild late skin rash is its disadvantage.

Optimal contrast agents for vascular imaging on computed tomography: iodixanol versus iohexol

RATIONALE AND OBJECTIVES

Dimeric nonionic iodinated contrast has a lower osmolality than monomeric nonionic iodinated contrast but is available at lower iodine concentrations. Less dilution of intravascular fluid by influx from the extravascular space is proposed to occur with decreasing osmolality. The purpose of this study was to determine if a dimeric nonionic iso-osmolar contrast agent (iodixanol) gives equal vascular enhancement compared with a monomeric nonionic hyperosmolar contrast agent (iohexol).

MATERIALS AND METHODS

A dynamic single-level computed tomography (CT) scan was performed of the abdominal aorta of 12 sedated rabbits using a four-row multidetector CT scanner following injection of 1.5 mL contrast/kg body weight at 2 mL/sec. The rabbits were injected with the dimeric contrast agent iodixanol (Visipaque 320; Amersham Health) or the monomeric contrast agent iohexol (Omnipaque 350; Amersham Health). The order of the type of contrast media injected was randomized for each rabbit, and the interval between injections was 2 weeks. Using the 2.5-mm detectors, four contiguous 3-mm contrast-enhanced scans were obtained at a single level every 5 seconds for 120 seconds (total of 24 scans) with a kVp of 120, mA.s of 110, field of view of 106 mm, and soft tissue reconstruction algorithm. A single level was chosen to measure the attenuation of the abdominal aorta at 5-second intervals. The mean attenuation and standard deviation values were recorded for the whole aorta, for the central half of the vessel, and for the peripheral half of the vessel. A log-log transformation of the data was performed and regression analysis was done on the outcomes of interest (e.g., mean, standard deviation) on time for each region.

RESULTS

There was no statistically significant difference in mean attenuation for the whole aorta for iodixanol and iohexol (P = .918) even though the iodine content was 9.3% less with the dimeric iodixanol. The time-attenuation curve of iodixanol paralleled that of iohexol for all time points. The mean attenuation values of the central half of the aorta (P = .354) and peripheral half of the aorta (P = .758) were also not statistically different for the two contrast agents.

CONCLUSION

The vascular attenuation provided by a 9.3% lower iodine concentration of iso-osmolar iodixanol is equal to that given by hyperosmolar iohexol. This suggests that there is less intravascular dilution of iso-osmolar contrast. The enhancement across the cross section of the vessel is also similar for both contrast agents. This suggests the vascular studies with iodixanol and iohexol are of equal quality even when a lower dose of iodine is given with iodixanol. It is relevant for patients with borderline or diminished renal function in whom less volume of contrast may be administered.

Comparison of Iodixanol with Iohexol for Delayed Pelvic Venous Opacification:A Preliminary Study of Potential Use for CT Venography

OBJECTIVE

The goal of this prospective randomized study was to determine whether isosmolar contrast material offers an advantage over low-osmolar contrast material for delayed venous opacification in CT venography. SUBJECTS AND METHODS. We prospectively enrolled 200 adult outpatients. Patients were randomized to receive either the low-osmolar (hyperosmolar to blood) nonionic contrast medium, iohexol, or the nonionic isosmolar contrast medium, iodixanol. Images were obtained before contrast administration and 180 sec after contrast administration through the pelvis at the level of the external iliac vessels. Opacification of the external iliac vessels was assessed both objectively and subjectively.

RESULTS

The arterial and venous densities before contrast administration were approximately 45 H for both groups. On delayed images obtained after contrast administration, the mean venous density was 95.2 H for iohexol and 101.4 H for iodixanol. Changes in venous density due to administration of iohexol and iodixanol were 49.8 and 56.1 H, respectively. This 12.5% difference was highly significant (p = 0.002). Sixty-six percent of the images in the iodixanol group were rated either 4 (good) or 5 (excellent), whereas only 36% of the iohexol group achieved a similar rating on our subjective rating scale. This difference was statistically significant (chi(2) = 16.4, p < 0.001, df = 1).

CONCLUSION

Our study shows that isosmolar contrast material provides significant improvement in delayed opacification of the external iliac vessels in comparison with conventional low-osmolar contrast medium (hyperosmolar to blood).

Intra-articular ganglion arising from the meniscofemoral ligament of Humphrey

We present a case of an intra-articular ganglion of the knee arising from the anterior meniscofemoral ligament of Humphrey. The MR imaging and arthroscopic appearance of the lesion are illustrated.

Optimization of contrast agent volume for helical CT in the diagnostic assessment of patients with severe and multiple injuries

PURPOSE

The aim of this study was to determine the optimal amount of contrast agent for helical CT of the trunk during primary radiologic evaluation of polytraumatized patients.

METHOD

Eighty-three patients with severe and multiple injuries (mean age 36.2 years) underwent standardized helical CT examination with administration of a single contrast agent bolus of iohexol (Accupaque 300) at volumes of 120, 150, and 180 ml. Image quality was estimated by two blinded radiologists using a visual analogue scale. Analysis further included density measurements in regions of interest (ROIs) placed in the ascending, descending, and abdominal aorta as well as in the liver and spleen.

RESULTS

The qualitative rating of the contrast agent effect after administration of 150 and 180 ml was significantly better compared with 120 ml [odds ratio (OR) 12.05, 95% confidence interval (CI) 3.50-41.52 and OR 12.14, 95% CI 3.36-43.85, respectively]. A dose increase from 120 to 150 ml resulted in a significantly better enhancement of the abdominal aorta (p = 0.006). The highest dose of 180 ml was not associated with a diagnostic gain in the other ROIs.

CONCLUSION

We recommend administration of 150 ml of iohexol as the optimal amount of contrast material for single phase bolus administration in emergency helical CT examination of the chest and abdomen.

Safety and pharmacokinetics of a new liposomal liver-specific contrast agent for CT: results of clinical testing in nonpatient volunteers

RATIONALE AND OBJECTIVES

To evaluate the safety and pharmacokinetics of BR21, a liposome-encapsulated iomeprol formulation, in nonpatient volunteers.

METHODS

This was a single-blind, placebo-controlled, ascending dose study in 30 adult, male nonpatient volunteers, randomized to receive a single intravenous bolus (2 mL/s) of BR21 (0.5, 1.0, 1.5, 2.0, and 2.5 mL/kg, four volunteers per dose level) or matched volumes of placebo (0.9% saline, 10 volunteers). The safety controls performed consisted of preand postdose complete physical examinations, measurement of vital signs, electrocardiographic controls, clinical laboratory investigations (hematology, serum chemistry, and urinalysis), and monitoring of adverse events. The safety controls and monitoring of subjects for adverse events continued up to 7 days after the dose. For pharmacokinetic analysis, the determination of total iomeprol content was performed by a high-performance liquid chromatography assay procedure in blood, urine, and fecal samples collected before the dose and serially after the dose, up to 120 hours.

RESULTS

No serious adverse events occurred throughout the study. All nonserious adverse events were minor and mild in intensity and rapidly resolved without treatment. No difference in the incidence of adverse events was observed among the various doses of BR21 and between BR21 and placebo. There were no clinically significant changes in vital signs, electrocardiographic parameters, or clinical laboratory findings. Iomeprol blood level decay can be described by a three-exponential function, consistent with a distribution phase (range, t1/2 0.12-0.21 hours), a fast elimination phase (range, t1/2 1.2-1.5 hours), and a slow elimination phase from a deep compartment (range, t1/2 3.3-4.5 hours). There was an apparent linearity in the relation between the area under the curve and the dose. Urinary elimination of unchanged iomeprol accounted for 89% to 90% of injected dose within 24 hours.

CONCLUSIONS

BR21 appeared to be safe and well tolerated in nonpatient subjects. Its pharmacokinetic profile was compatible with nonspecific distribution into the extracellular fluid space and specific distribution into a deep compartment.

Effective contrast use in CT angiography and dual-phase hepatic CT performed with a subsecond scanner

OBJECTIVE

To deduce an optimal injection protocol for CT angiography and fast dual-phase hepatic CT.

METHODS

Fifty-two patients underwent fast dual-phase hepatic CT using one of three different injection protocols: A (0.9 g/sec iodine injection rate, 36 g dose); B (1.35 g/sec, 30 g); C (1.6 g/sec, 40 g). Aortic attenuation time curves as well as aorta-to-liver contrast and hepatic enhancement time curves obtained by region of interest measurements along the helical axis were analyzed.

RESULTS

Protocol C revealed a significantly higher peak in aortic attenuation and hepatic enhancement than the other protocols. Approximately 50 seconds after the bolus injection, hepatic enhancement declined to a plateau similar to that seen with the other protocols. In terms of the areas under the curves of the aorta-to-liver contrast and hepatic enhancement dynamics, protocol C was significantly superior to the other protocols.

CONCLUSIONS

A high iodine injection rate realized by a high iodine concentration in conjunction with fast dual-phase scanning (total scan time < 50 seconds) promises to enhance CT angiography and contrast of liver lesions.

Spiral CT angiography of the abdominal aorta. Comparison of iodixanol and ioversol

RATIONALE AND OBJECTIVES

Enhancement characteristics of a nonionic, dimeric, isotonic contrast medium (iodixanol [Visipaque]) were compared with a nonionic, monomeric contrast medium (ioversol [Optiray]) of the same iodine concentration in spiral computed tomography angiography (CTA) of the abdominal aorta.

METHODS

Spiral CTA was performed in 78 patients referred for suspected renal artery stenosis (n = 35) and abdominal aortic aneurysm (n = 43). A test bolus was used to time the scan delay, and all patients were injected with 150 ml contrast medium (320 mgI/ml) of either iodixanol (n = 40) or ioversol (n = 38). Contrast enhancement was measured in the aorta, renal arteries, and renal parenchyma.

RESULTS

All mean aortic enhancement was slightly higher with iodixanol than ioversol, measured at three different levels (celiac trunk 315 Hounsfield units [HU] versus 300 HU, renal arteries 325 HU versus 312 HU, aortic bifurcation 276 HU versus 266 HU). However, none of them were statistically significant (e.g., P = 0.26 at the celiac trunk level). Similar results were observed in renal artery and parenchyma enhancements.

CONCLUSIONS

Iodixanol and ioversol had similar enhancement characteristics in the early arterial phase. Both substances were well tolerated and seem to be well suited for spiral CTA.