Jodeinbringungsgeschwindigkeit verschieden konzentrierter Röntgenkontrastmittel bei schneller intravenöser Injektion

Clinical evaluation of a novel multibolus contrast agent injection protocol for thoraco-abdominal CT angiography: Assessment of homogeneity of arterial contrast enhancement

PURPOSE

To evaluate the in vivo feasibility of a multibolus contrast agent (CA) injection protocol with a reduced CA volume for thoraco-abdominal CT angiography (CTA) and to compare it to a single-bolus CA injection protocol.

METHOD

63 patients who underwent CTA with the multibolus protocol (60 ml CA) were divided in two groups either without (group 1, n = 48) or with (group 2, n = 15) aortic dissection. The aortic contrast enhancement was measured in group 1 using manual ROI analysis (10 segments), as well as semi-automated linear attenuation profiles. A subgroup (n = 18) of group 1, who also underwent imaging with the single-bolus protocol (94 ml CA), was used to compare both protocols. In group 2, differences in attenuation of the true and the false lumen for both the single- and the multibolus protocol were assessed with ROI attenuation measurements in both lumina. Comparisons were made using Wilcoxon test.

RESULTS

Average attenuation was above 200 HU for 98 % of cases using the multibolus protocol. There was superior contrast homogeneity for the multibolus protocol with a lower standard deviation of attenuation values along the length of the scan (p = 0.003), while average attenuation was higher for the single-bolus protocol (p = 0.002). Prolonged enhancement plateau lead to a more uniform opacification of the true and the false lumen in patients with aortic dissection using the multibolus protocol (p = 0.012).

CONCLUSIONS

The multibolus protocol in thoraco-abdominal CTA is feasible in patients. It shows consistently high arterial enhancement with superior contrast homogeneity compared to a single-bolus protocol in patients with and without aortic dissection.

Low radiation dose in computed tomography: the role of iodine

Recent approaches to reducing radiation exposure during CT examinations typically utilize automated dose modulation strategies on the basis of lower tube voltage combined with iterative reconstruction and other dose-saving techniques. Less clearly appreciated is the potentially substantial role that iodinated contrast media (CM) can play in low-radiation-dose CT examinations. Herein we discuss the role of iodinated CM in low-radiation-dose examinations and describe approaches for the optimization of CM administration protocols to further reduce radiation dose and/or CM dose while maintaining image quality for accurate diagnosis. Similar to the higher iodine attenuation obtained at low-tube-voltage settings, high-iodine-signal protocols may permit radiation dose reduction by permitting a lowering of mAs while maintaining the signal-to-noise ratio. This is particularly feasible in first pass examinations where high iodine signal can be achieved by injecting iodine more rapidly. The combination of low kV and IR can also be used to reduce the iodine dose. Here, in optimum contrast injection protocols, the volume of CM administered rather than the iodine concentration should be reduced, since with high-iodine-concentration CM further reductions of iodine dose are achievable for modern first pass examinations. Moreover, higher concentrations of CM more readily allow reductions of both flow rate and volume, thereby improving the tolerability of contrast administration.

Coronary CT angiography using low concentrated contrast media injected with high flow rates: Feasible in clinical practice

PURPOSE

Aim of this study was to test the hypothesis that peak injection pressures and image quality using low concentrated contrast media (CM) (240 mg/mL) injected with high flow rates will be comparable to a standard injection protocol (CM: 300 mg/mL) in coronary computed tomographic angiography (CCTA).

MATERIAL AND METHODS

One hundred consecutive patients were scanned on a 2nd generation dual-source CT scanner. Group 1 (n=50) received prewarmed Iopromide 240 mg/mL at an injection rate of 9 mL/s, followed by a saline chaser. Group 2 (n=50) received the standard injection protocol: prewarmed Iopromide 300 mg/mL; flow rate: 7.2 mL/s. For both protocols, the iodine delivery rate (IDR, 2.16 gI/s) and the total iodine load (22.5 gI) were kept identical. Injection pressure (psi) was continuously monitored by a data acquisition program. Contrast enhancement was measured in the thoracic aorta and all proximal and distal coronary segments. Subjective and objective image quality was evaluated between both groups.

RESULTS

No significant differences in peak injection pressures were found between both CM groups (121 ± 5.6 psi vs. 120 ± 5.3 psi, p=0.54). Flow rates of 9 mL/s were safely injected without any complications. No significant differences in contrast-to-noise ratio, signal-to-noise ratio and subjective image quality were found (all p>0.05). No significant differences in attenuation levels were found in the thoracic aorta and all segments of the coronary arteries (all p>0.05).

CONCLUSION

Usage of low iodine concentration CM and injection with high flow rates is feasible. High flow rates (9 mL/s) of Iopromide 240 were safely injected without complications and should not be considered a drawback in clinical practice. No significant differences in peak pressure and image quality were found. This creates a doorway towards applicability of a broad variety in flow rates and IDRs and subsequently more individually tailored injection protocols.

Intravenous contrast medium administration and scan timing at CT: considerations and approaches

The continuing advances in computed tomographic (CT) technology in the past decades have provided ongoing opportunities to improve CT image quality and clinical practice and discover new clinical CT imaging applications. New CT technology, however, has introduced new challenges in clinical radiology practice. One of the challenges is with intravenous contrast medium administration and scan timing. In this article, contrast medium pharmacokinetics and patient, contrast medium, and CT scanning factors associated with contrast enhancement and scan timing are presented and discussed. Published data from clinical studies of contrast medium and physiology are reviewed and interpreted. Computer simulation data are analyzed to provide an in-depth analysis of various factors associated with contrast enhancement and scan timing. On the basis of basic principles and analysis of the factors, clinical considerations and modifications to protocol design that are necessary to optimize contrast enhancement for common clinical CT applications are proposed.

Biphasic contrast medium injection in cardiac CT: moderate versus high concentration contrast material at identical iodine flux and iodine dose

Objective

To prospectively investigate the influence of contrast material concentration on enhancement in cardiac CT by using a biphasic single-injection protocol.

Methods

Sixty-four-row multidetector cardiac CT angiography was performed in 159 patients randomised to a moderate or high contrast medium concentration. Contrast material injection included a first phase for enhancement of the coronary arteries and a second phase, at half the iodine flux, targeted at enhancement of the right ventricle. Contrast medium injection was followed by a saline flush. For both concentrations, injection duration (and thus total iodine dose) was adapted to the duration of the CT data acquisition and iodine flux was adjusted to patient weight. Attenuation was measured at various levels in the heart and vessels and the two concentrations compared, overall and per weight group.

Results

Enhancement of the aorta and left ventricle was significantly greater with the moderate than with the high concentration contrast medium. This remained true for the two higher weight groups. No difference was found in the lowest weight group or in the right ventricle and pulmonary outflow tract.

Conclusion

With a biphasic injection protocol, enhancement of the aorta and left ventricle was weaker with the higher concentration of contrast material.

Peripheral intravenous power injection of iodinated contrast media: the impact of temperature on maximum injection pressures at different cannula sizes

RATIONALE AND OBJECTIVES

Modern computed tomographic scanners and examination protocols often require high injection rates of iodinated contrast media (CM). The purpose of this study was to investigate the maximum injection pressures (MIPs) with different CM at different temperatures in the most common intravenous cannula (IVC) sizes.

MATERIALS AND METHODS

Three IVC sizes, 22, 20, and 18 gauge, were evaluated. All examinations were performed with a pressure-limited (300 psi) power injector. The MIPs of three different CM (Solutrast 300, Imeron 350, and Imeron 400) were measured at room temperature (20 degrees C) and at 37 degrees C using increasing flow rates (1-9 mL/s). The intactness of the IVCs was checked after injection.

RESULTS

Heating the CM led to reductions in injection pressures (P < .001). Using constant flow rates, the difference in MIP between 20-gauge and 22-gauge IVCs was higher than that between 20-gauge and 18-gauge IVCs. By heating the CM, the manufacturer's suggested operating pressure limit was exceeded at higher flow rates, such as with an 18-gauge cannula at 8 mL/s instead of 6 mL/s using warmed iomeprol 400. Even with pressures of up to 159.7 psi, none of the IVCs ruptured.

CONCLUSIONS

Heating of CM effectively reduces MIPs using power injection in common IVCs. Although the manufacturer's suggested MIP was exceeded at higher flow rates, safe CM injection seems to be possible even in small cannulas using power injection. The compilation of the obtained data is meant to serve as guidance for future decisions on parameters of the power injection of iodinated CM.

The impact of warmed intravenous contrast material on the bolus geometry of coronary CT angiography applications

Objective

This study was designed to investigate the effect of administration of warmed contrast material (CM) on the bolus geometry and enhancement as depicted on coronary CT angiography.

Materials and Methods

A total of 64 patients (42 men, 22 women; mean age, 56 years) were randomly divided into two groups. Group 1 included 32 patients administered CM (Omnipaque [Iohexol] 350 mg I/ mL; Nycomed, Princeton, NJ) saline solutions kept in an incubator at a constant temperature (37℃). Group 2 included 32 patients administered the CM saline solutions kept at constant room temperature (24℃). Cardiac CT scans were performed with a dual source computed tomography (DSCT) scanner. For each group, region of interest curves were plotted inside the ascending aorta, main pulmonary artery and descending aorta on test bolus images. Using enhancement values, time/enhancement diagrams were produced for each vessel. On diagrams, basal Hounsfield unit (HU) values were subtracted from sequentially obtained values. A value of 100 HU was accepted as a cut-off value for the beginning of opacification. The time to peak, the time required to reach 100 HU opacification, maximum enhancement and duration of enhancement above 100 HU were noted. DSCT angiography studies were evaluated for coronary vessel enhancement.

Results

Maximum enhancement values in the ascending aorta, descending aorta and main pulmonary artery were significantly higher in group 1 subjects. In the ascending aorta, the median time required to reach 100 HU opacification during the test bolus analysis was significantly shorter for group 2 subjects than for group 1 subjects. In the ascending aorta, the descending aorta and main pulmonary artery, for group 1 subjects, the bolus geometry curve shifted to the left and upwards as compared with the bolus geometry curve for group 2 subjects.

Conclusion

The use of warmed CM yields higher enhancement values and a shorter time to reach maximum enhancement duration, resulting in a shift of the bolus geometry curve to the left that may provide optimized image quality.

Comparison of different iodine concentration contrast media in perfusion computed tomography of the brain: is high iodine concentration useful?

OBJECTIVES

To investigate maximum enhancement and visual map quality in cerebral perfusion computed tomography (PCT) with variation of iodine concentration of contrast media (CM).

MATERIALS AND METHODS

Two groups of 45 patients each, underwent PCT with either 370 mg iodine/mL (30 mL; 6 mL/s) or 300 mg iodine/mL (40 mL; 8 mL/s) CM, respectively, and similar total iodine dose. Parenchymal and vascular enhancement as well as contrast-to-noise ratio of superior sagittal sinus was measured on PCT source images. PCT maps were rated visually with dichotomized scale for diagnostic quality.

RESULTS

Enhancement and contrast-to-noise ratio of the superior sagittal sinus was significantly higher for the 370 mg iodine/mL protocol (P < 0.0002 and P < 0.007), whereas parenchymal enhancement was not significantly different. Diagnostic quality of PCT maps did not differ between both protocols (P < 0.557).

CONCLUSIONS

PCT using 370 mg iodine/mL CM can be reliably performed with reduced injection rate and less total volume enabling smaller diameter of intravenous canula compared with 300 mg iodine/mL CM.

Coronary computed tomography angiography: principles of contrast material administration

A conceptual framework to approach the application of contrast media in computed tomography angiography (CTA) is discussed. With an adequate conceptual framework, the physician or technologist should be able to modify or create CTA protocols to address specific clinical and patient circumstances. The focus of this review is coronary CTA, but the basic principles are applicable to CTA in any arterial system.

Optimization of contrast material administration for electrocardiogram-gated computed tomographic angiography of the chest

OBJECTIVE

Electrocardiogram-gated computed tomographic angiography is increasingly used in the differential diagnosis of acute chest pain. We studied the optimal timing of contrast material injection using a test bolus and a bolus-tracking technique.

MATERIALS AND METHODS

Thirty patients were prospectively included in the study. Volume and flow of high concentration contrast material were adapted to body weight. The scan delay was determined using either a test bolus or a bolus-tracking technique. Attenuation profiles of the different vascular districts were measured to evaluate the timing techniques.

RESULTS

In all the patients except for one, an adequate and homogeneous contrast enhancement of more than 200 Hounsfield units (HU) was achieved (285 +/- 45 HU) in the different vascular districts. The pulmonary transit time in the test bolus group was 7 seconds (range, 4-11 seconds). Differences and variability of pulmonary and aortic enhancement were small in both groups (13 +/- 48 HU vs -9 +/- 21 HU), with differences of less than 70 HU over the craniocaudal range and very small intraindividual differences between pulmonary attenuation and systemic attenuation.

CONCLUSIONS

Contrast administration regimens for electrocardiogramgated computed tomographic angiography of the chest can be optimized using the bolus-tracking method in the ascending aorta, with a short delay after trigger. Body weight adaptation of volume and injection rate of the contrast material results in a reliable simultaneous opacification of the pulmonary and systemic vasculature.

A prospective study comparing different iodine concentrations for triphasic multidetector row CT of the upper abdomen

OBJECTIVES

To investigate the effect of different iodine concentrations at either constant injection or iodine administration rates but constant total iodine load on contrast enhancement of liver, pancreas and spleen by multidetector row CT.

MATERIALS AND METHODS

One hundred and twenty consecutive patients (70+/-6 years) underwent triphasic liver CT at a four-channel multidetector-row CT using the non-ionic contrast medium iopromide. Patients were divided into six equal groups-I: 150 ml, 240 mg/ml at 4 ml/s; II: 120 ml, 300 mg/ml at 4 ml/s; III: 97.3 ml, 370 mg/ml at 4 ml/s; IV: 150 ml, 240 mg/ml at 5 ml/s; V: 120 ml, 300 mg/ml, 60 ml at 6 ml/s, 60 ml at 3 ml/s; VI: 97.3 ml, 370 mg/ml at 3.3 ml/s. ROIs were measured in the liver, the pancreas, and the spleen in unenhanced, arterial, portal venous, and equilibrium phase.

RESULTS

At a constant injection rate of 4 ml/s, pancreatic enhancement over baseline only in the arterial phase was significantly higher at 370 mg/ml (58+/-15 HU versus 59+/-18 HU versus 74+/-20 HU for groups I-III, respectively (p<0.02)). Comparison of different iodine concentrations at constant iodine administration rate (groups II, IV and VI) and of all six protocols revealed no significant differences at either phase.

CONCLUSIONS

At a constant iodine load and constant injection rates, the high-iodinated contrast agent iopromide at 370 mg/ml improves pancreatic enhancement in the arterial phase. At constant iodine load and constant iodine administration rates, there is no significant effect of different iodine concentrations.

Comparison of different iodine concentrations for multidetector row computed tomography angiography of segmental renal arteries

The aims of this study were (1) to assess the diagnostic performance of multidetector row computed tomography angiography (CTA) on imaging of renal artery branches and (2) to investigate the effect of different iodine concentrations at constant total iodine load and either constant injection rates or constant iodine administration rates. A number of 120 consecutive patients (71+/-6 years of age) underwent CTA of renal arteries (collimation 4 x 1 mm) using the nonionic contrast medium iopromide, and were divided into six equal groups: 1: 150 ml, 240 mg/ml at 4 ml/s; 2: 120 ml, 300 mg/ml at 4 ml/s; 3: 97.3 ml, 370 mg/ml at 4 ml/s; 4: 150 ml, 240 mg/ml at 5 ml/s; 5: 120 ml, 300 mg/ml, 60 ml at 6 ml/s, 60 ml at 3 ml/s; 6: 97.3 ml, 370 mg/ml at 3.3 ml/s. The image quality of the main renal arteries (n=240) and their first-order to fourth-order branches was scored as 0 for no visualization, 1 for only visualization, and 2 for diagnostic. All main renal arteries were diagnostic. First-order branches had score 2 in 38/40, 40/40, 37/40, 38/40, 39/40, and 40/40 patients for groups 1-6, respectively (p=0.34). Second-order branches were imaged best in group 2 (p<0.002)). Third-order branches had score 2 in only 1/40, 5/40, 1/40, 2/40, 0/40, and 2/40 renal arteries. Fourth-order branches were not imaged diagnostically. At a constant total iodine load, the main renal arteries and their first-order branches achieved diagnostic image quality at all iodine concentrations in four-channel multidetector row CTA for the protocols tested. Second-order renal artery branches were imaged best at 120 ml contrast medium with an iodine concentration of 300 mg/ml at 4 ml/s.