| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Original Research |
1 Department of Diagnostic Radiology, University Hospital RWTH Aachen,
Pauwelsstraße 30, 52057 Aachen, Germany.
2 Institute of Medical Statistics, University Hospital RWTH Aachen, Aachen,
Germany.
3 Bayer Schering Pharma, Berlin, Germany.
4 Medical Clinic IV, University Hospital RWTH Aachen, Aachen, Germany.
Received September 19, 2007;
accepted after revision January 8, 2008.
The employment status of P. Seidensticker at Bayer Schering Pharma did not
influence the data in this study.
Abstract
 Top Abstract IntroductionSubjects and MethodsResultsDiscussionReferences |
|---|
SUBJECTS AND METHODS. Seventy-five patients underwent baseline and
follow-up MDCT of the chest and abdomen with contrast media containing a high
concentration of iodine (iopromide 370 mg I/mL) and standard iodine
concentration (iopromide 300 mg I/mL). The total iodine load (37 g) and the
iodine delivery rate (1.29 g/s) were identical for the two protocols. Contrast
enhancement in the chest (right and left ventricles, pulmonary trunk,
descending aorta) and the abdomen (aorta, inferior vena cava, portal vein, and
liver) was determined. Results were compared by use of paired Student's
t tests, and p was adjusted with Bonferroni correction for
multiple comparisons (p 
0.0056).
RESULTS. Contrast enhancement was significantly higher for the 300 mg I/mL protocol than for the 370 mg I/mL protocol at all anatomic sites in the chest except the left ventricle (right ventricle, 359 ± 100 H vs 320 ± 102 H, p = 0.003; pulmonary trunk, 334 ± 96 H vs 303 ± 89 H, p = 0.003; left ventricle, 310 ± 54 H vs 300 ± 51 H, p = 0.036; descending aorta, 300 ± 63 H vs 277 ± 57 H, p = 0.0002). No statistically significant differences were found in the abdomen (all p > 0.0056).
CONCLUSION. Given equivalent iodine load and delivery rate, the use of 300 mg I/mL contrast medium results in better contrast enhancement than use of 370 mg I/mL contrast medium in CT of the chest. For the portal venous phase of CT of the abdomen, there was no significant difference in contrast enhancement for the two concentrations of iodine.
Keywords: contrast administration • contrast dosage • contrast media • reproducibility • x-ray CT
|
TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
|---|
Awai et al. [12] found that median abdominal aortic enhancement was higher with a lower than with a higher concentration of contrast medium when the total iodine dose was adapted to body weight and when a fixed injection duration was used. Com parable results were reported in an animal study by Han et al. [7], who found increased contrast enhancement with a contrast medium with a lower concentration (150 mg I/mL) than with a higher concentration (300 mg I/mL) given the same total iodine dose and iodine delivery rate.
The aim of this study was an intraindividual comparison of degrees of contrast enhancement achieved with media containing 300 and 370 mg I/mL at identical iodine delivery rates and identical total iodine doses in MDCT examinations of the chest and abdomen. Paired comparison of the two scanning protocols between baseline and follow-up scans of the same patients was used to minimize the effect of interpatient variability.
|
TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
|---|
Injection and Scan Protocol
All patients were examined at least twice with contrast media in two iodine
concentrations. The initial examination was performed with a high iodine
concentration of 370 mg I/mL (iopromide, Ultravist 370, Bayer HealthCare). The
second CT examination was performed with a standard iodine concentration of
300 mg I/mL (iopromide, Ultravist 300, Bayer HealthCare). Preheated contrast
medium (37°C) was administered IV with a power injector (CT2, MediTron)
into an antecubital vein through a 20-gauge access. The total iodine dose (37
g) and the iodine delivery rate (1.29 g/s) were kept constant for the two
protocols. However, the flow rate and total volume had to be adapted to ensure
a constant total iodine dose and iodine delivery rate over time (370 mg I/mL
protocol, 100 mL at 3.5 mL/s; 300 mg I/mL protocol, 123 mL at 4.3 mL/s).
Injection of contrast medium was followed by a saline chaser (50 mL of 0.9%
saline solution) administered with flow rates of 3.5 mL/s (370 mg I/mL
protocol) and 4.3 mL/s (300 mg I/mL protocol).
All studies were performed with a 16-MDCT scanner (Somatom Sensation 16, Siemens Medical Solutions). Scanning was performed in the craniocaudal orientation. Scan parameters were as follows: collimation, 16 x 1.5 mm; table feed, 24 mm/rotation; rotation time, 0.5 second. Effective tube current–time products of 120 mAs for the chest and 160 mAs for the abdomen were chosen at a tube voltage of 120 kVp. Image reconstruction was performed with a medium-smooth soft-tissue kernel (B30) at a slice thickness of 5 mm with an overlapping increment of 4 mm.
|
Quantitative Analysis
Contrast enhancement was measured in the chest (right and left ventricles,
pulmonary trunk, descending aorta) and the abdomen (descending aorta and
inferior vena cava at the level of the renal artery origin, portal vein, liver
parenchyma) by placement of a circular region of interest at each anatomic
site. Attenuation was assessed in three adjacent slices, and the attenuation
values were averaged for the vessels and the cardiac chambers. For the liver,
contrast enhancement was measured in three homogeneous areas of the right
liver lobe at the level of the portal vein. Visible hepatic blood vessels,
bile ducts, and artifacts were excluded from the measurements. At all anatomic
sites, a constant region of interest measuring approximately 1.0
cm2 was maintained. All measurements were performed by an
experienced radiologist.
Statistical Analysis
Contrast enhancement values obtained with the 370 and 300 mg I/mL protocols
at each anatomic site were summarized in arithmetic means and corresponding
SD. Arithmetic means and corresponding SD of contrast enhancement were
compared graphically between the 370 and 300 mg I/mL protocols for each of the
eight anatomic sites. The paired Student's t test was used to compare
contrast enhancement values between the 370 and 300 mg I/mL protocols and for
comparison of body weights between baseline and follow-up. The Bonferroni
method was used to adjust the significance alpha level to correct for the
problem of multiple comparisons. Specifically, the usual significance level
(
= 0.05) was divided by 9 to account for nine comparisons. Thus only
p 0.0056 was considered statistically significant in this study.
All statistical analyses were conducted with a statistical analysis software
package (SAS version 9.1, SAS Institute). Graphic representations were made
with the R statistical analysis system (R Foundation).
|
TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
|---|
|
|
|
|
|
|
|
|
TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
|---|
Our results showed that at identical iodine delivery rates, contrast enhancement was statistically significantly higher in all anatomic sites in the chest except for the left ventricle with use of contrast medium containing 300 mg I/mL than with use of an agent containing 370 mg I/mL. In the left ventricle, the mean attenuation was higher for the 300 mg I/mL contrast medium than for the 370 mg I/mL agent, though the difference was not statistically significant (p = 0.0364). The quality of CT angiography is influenced mainly by intravascular contrast enhancement, and high blood attenuation is crucial for reliable evaluation of small vessels on CT angiography. Therefore, in adapted injection protocols, the use of 300 mg I/mL contrast medium may improve visualization of small structures and pathologic changes, thereby improving diagnostic value, for example, in evaluation of peripheral pulmonary arteries. Further investigations are needed for more detailed evaluation.
In an animal study with meglumine ioglicate (Rayvist, Bayer Schering Pharma) in an injection protocol with identical total iodine loads and injection durations, Han et al. [7] found greater peak enhancement of the aorta and liver at a low concentration (150 mg I/mL) of contrast medium than with a high concentration (300 mg I/mL). Awai et al. [12] compared the aortic and hepatic enhancement of iohexol 300 (300 mg iodine/mL) and iohexol 350 (350 mg I/mL) administered in the same total iodine load and injection duration. The study showed greater aortic enhancement with iohexol 300 than with iohexol 350 during the early phases of CT. Unlike our method, injection of contrast medium was not followed by a saline chaser. However, the findings of the two studies were comparable to our findings.
A possible explanation for the higher mean attenuation with contrast media at low iodine concentration in the early phase of CT is viscosity. Viscosity increases with higher concentrations of iodine and decreasing temperatures of contrast medium. The viscosity of iopromide 370 is more than double that of iopromide 300 at both 20°C and 37°C. The viscosity of iopromide 370 is 20.1 mPa·s at 20°C and 9.5 mPa·s at 37°C with an osmolality of 0.77 osm/kg H2O, and the viscosity of iopromide 300 is 8.7 mPa·s at 20°C and 4.6 mPa·s at 37°C with an osmolality of 0.61 osm/kg H2O (data from Bayer Schering Pharma). A fluid with lower viscosity can be injected at lower pressure and may become distributed more easily and more evenly in the vessels. This phenomenon would explain the greater contrast enhancement in the early phase after contrast administration.
In abdominal imaging, we did not find statistically significant differences in mean attenuation values for intraluminal vessel enhancement or liver parenchymal enhancement with high and standard iodine concentrations. The results show that in the portal venous phase, contrast enhancement is not influenced by the iodine concentration of the contrast medium but is determined by the total amount of iodine. Our results are comparable with the findings of Sandstede et al. [16], who found no statistically significant effect of different iodine concentrations on contrast enhancement of the liver, pancreas, or spleen. Those investigators compared iopromide at three iodine concentrations (240, 300, and 370 mg I/mL) and used an injection protocol with a constant iodine load and constant iodine delivery rate. Similar results were described by Suzuki et al. [26], who compared contrast media with iodine concentrations of 300 and 370 mg I/mL using injection protocols with identical iodine doses and injection durations. Their results showed no statistically significant differences in enhancement of the aorta, portal vein, or liver parenchyma in the portal venous phase for the two contrast media.
Awai et al. [12] reported no statistically significant difference in hepatic enhancement in the portal venous phase using the contrast media iohexol 300 and 350 (300 and 350 mg I/mL). In that study the total iodine dose was adapted to body weight, and the injection duration was kept constant. Unlike our finding, mean aortic attenuation in the portal venous phase was statistically significantly higher with iohexol 300 than with iohexol 350. However, several methodologic differ ences between the study by Awai at al. and our study preclude direct comparison of the two setups. First, the studies were performed with different contrast media (iohexol and iopromide). Second, in the study by Awai et al., the total iodine dose was adapted to body weight and was not kept constant, as it was in our study. Third, in our study contrast administration was followed by a saline chaser. In addition, and this is the main difference, our study was an intraindividual comparison.
In other studies, contrast enhancement has been compared in different patient groups. The limitation of that type of study is the interpatient variability of contrast enhancement due to differences in age, body mass index, cardiac output, and circulation time. In our study, contrast enhancement at baseline MDCT was compared with enhancement at follow-up MDCT of the same patient; therefore, all patients were their own controls [27]. The results show that suitable contrast enhancement can be achieved with both standard and high iodine concentrations of contrast medium in examinations of the chest and abdomen performed with an adapted injection protocol.
The advantage of use of contrast media with a lower iodine concentration is the lower osmolarity and viscosity than those of high-iodine-concentration contrast media. Both chemical properties, especially viscosity, of contrast media have been associated with toxic side effects, such as nephrotoxicity [28, 29]. Seeliger et al. [30] found that the viscosity of contrast media may play an important role in contrast-induced nephrop athy by decreas ing glomerular filtration rate and renal medullary blood flow. Admin istration of contrast medium with moderate iodine concentration has the potential to decrease these toxic side effects. Because of the results of our study and the lower viscosity and possibly lower incidence of contrast-induced nephropathy, 300 mg I/mL contrast medium is now used in clinical routine at our institution.
To obtain the same iodine delivery rate with standard and high iodine concentrations, contrast medium with the standard concentration has to be administered at a faster injection rate. In previous studies [31, 32], the increased injection rate was discussed as a potential disadvantage because of a higher risk of extravasation. To our knowledge, however, no correlation between injection rate and the frequency of extravasation has been re ported in the literature. In addition, the substantial effect of viscosity on volume flow during injection, in accordance with the Hagen-Poiseuille law, must be taken into account.
Our study had minor limitations. First, the design as an intraindividual analysis of baseline and follow-up examinations necessi tated a time interval between the two exami nations. During this period, values such as cardiac output and body weight might have changed. However, we found no significant difference in body mass index between base line and follow-up examinations. Sec ond, the abdomen was scanned only during the portal venous phase; abdominal contrast enhancement in the arterial phase was not assessed.
Intraindividual comparison showed better chest attenuation values in the arterial phase with use of a contrast medium containing 300 mg I/mL than with an agent containing 370 mg I/mL. In portal venous phase imaging of the abdomen, there was no statistically significant difference in attenuation at stand ard or high iodine concentration in any ana tomic site.
|
TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
|---|
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
