Effects of iopamidol-370 versus iodixanol-320 on coronary contrast, branch depiction, and heart rate variability in dual-source coronary MDCT angiography

Efficacy and Safety of Iodixanol in Computed Coronary Tomographic Angiography and Cardiac Catheterization

Iodixanol is an iso-osmolar non-ionic dimeric hydrophilic contrast agent with a higher viscosity than the monomeric agents. It is the only Food and Drug Administration (FDA)-approved iso-osmolar agent in the United States, and it is the only contrast agent with an FDA-approved indication for use in cardiac computed tomographic angiography (CCTA), to assist in the diagnostic evaluation of patients with suspected coronary artery disease. In clinical studies, it has been noted to have fewer side effects and similar image quality when compared to low-osmolar contrast media. This can be attributed to the pharmacological properties of iodixanol. These contrast agents are used for coronary computed tomography angiography and cardiac catheterization. In this article, the use, tolerability, and efficacy of iodixanol are reviewed, specifically evaluating the use of CCTA and coronary angiography, including outcome studies, randomized trials, and comparisons to other contrast agents.

Stent evaluation by coronary computed tomography angiography: a comparison between Iopamidol-370 and Ioversol-320 hypo-osmolar iodine concentration contrasts

OBJECTIVE

Qualitative and quantitative image analysis between Iopamidol-370 and Ioversol-320 in stents´ evaluation by coronary computed tomography angiography (CTA).

METHODS

Sixty-five patients with low-risk stable angina undergoing stent follow-up with coronary CTA were assigned to Iopamidol I-370 (n = 33) or Ioversol I-320 (n = 32) in this prospective, double-blind, non-inferiority, randomized trial. Stent lumen image quality was graded by 5-point Likert Scale. Lumen mean attenuation was measured at native coronary segments: pre-stent, post-stent, distal segments and at coronary plaques. Lumen attenuation increase (LAI) ratio was calculated for all stents. Heart rate (HR) variation, premature heart beats (PHB), heat sensation (HS), blooming and beam hardening were also assessed.

RESULTS

Image quality was similar between groups, with no significant difference (Likert score 4.48 ± 0.75 vs 4.54 ± 0.65, p = 0.5). There were similarities in LAI ratio between I-370 and I-320 (0.39 ± 0.42 vs 0.48 ± 0.44 HU, p = 0.08). Regarding lumen mean attenuation at native coronary segments, a significant difference was observed, with I-320 presenting lower values, including contrast mean attenuation in distal segments. After statistical multivariate analysis, three variables correlated with stent image quality: 1) stent diameter, 2) HR variation and 3) stent lumen LAI ratio.

CONCLUSIONS

There was no significant difference between Iopamidol-370 mgI ml^-1 and Ioversol-320 mgI ml^-1 contrasts regarding overall stent lumen image quality, which was mainly influenced by stent diameter, HR and LAI ratio.Advances in knowledge:Coronary CTA allows adequate stents' visualization and image quality is influenced by stent diameter, HR variation and LAI ratio.Stents' image quality showed no difference between different concentration contrasts (I-370 vs. I-320); however, higher concentration contrasts may provide an improved overall visualization, especially regarding coronary distal segments.

Contrast enhancement efficacy of iodinated contrast media: Effect of molecular structure on contrast enhancement

Purpose

To investigate the contrast enhancement in DSA images based on the X-ray absorption characteristics of iodinated contrast media.

Methods

We have derived a new formula of predicting the pixel value ratio of two different contrast media and designate it as "Contrast Enhancement Ratio (CER)". In order to evaluate the accuracy of CER, we have evaluated the relationship between CER and pixel value ratio for all combinations of eleven iodinated contrast media. The non-ionic iodinated contrast media, iopamidol, iomeprol, iopromide, ioversol, iohexol, and iodixanol, were evaluated in this study. Each contrast medium was filled in the simulated blood vessel in our constructed anthropomorphic phantom, and DSA images were obtained using an angiographic imaging system. To evaluate the contrast enhancement of the contrast medium, the mean pixel value was calculated from all pixel values in the vascular image.

Results

CER was indicated to agree well with the pixel value ratio of two different contrast medium solutions and showed a good accuracy. CER was also shown to have a good linear relation to the pixel value ratio when the iodine concentration was constant. This means that the molecular structure of the contrast media affects contrast enhancement efficacy. Furthermore, in evaluation of contrast enhancement of iodinated contrast media by using the weight factor (that is a key factor in CER) ratio, Iodixanol, and iopamidol, and iomeprol have the same ability of contrast enhancement in DSA images, and iohexol shows the lowest ability.

Conclusions

We have derived a new formula (CER) of predicting the pixel value ratio of two different contrast medium solutions, and shown that CER agreed well with the pixel value ratio for blood vessel filled with eleven contrast media.

Subtraction CT angiography in head and neck with low radiation and contrast dose dual-energy spectral CT using rapid kV-switching technique

OBJECTIVE

To investigate the application of low radiation and contrast dose spectral CT angiology using rapid kV-switching technique in the head and neck with subtraction method for bone removal.

METHODS

This prospective study was approved by the local ethics committee. 64 cases for head and neck CT angiology were randomly divided into Groups A (n = 32) and B (n = 32). Group A underwent unenhanced CT with 100 kVp, 200 mA and contrast-enhanced CT with spectral CT mode with body mass index-dependent low dose protocols. Group B used conventional helical scanning with 120 kVp, auto mA for noise index of 12 HU (Hounsfield unit) for both the unenhanced and contrast-enhanced CT. Subtraction images were formed by subtracting the unenhanced images from enhanced images (with the 65 keV-enhanced spectral CT image in Group A). CT numbers and their standard deviations in aortic arch, carotid arteries, middle cerebral artery and air were measured in the subtraction images. The signal-to-noise ratio and contrast-to-noise ratio for the common and internal carotid arteries and middle cerebral artery were calculated. Image quality in terms of bone removal effect was evaluated by two experienced radiologists independently and blindly using a 4-point system. Radiation dose and total iodine load were recorded. Measurements were statistically compared between the two groups.

RESULTS

The two groups had same demographic results. There was no difference in the CT number, signal-to-noise and contrast-to-noise ratio values for carotid arteries and middle cerebral artery in the subtraction images between the two groups (p > 0.05). However, the bone removal effect score [median (min-max)] in Group A [4 (3-4)] was rated better than in Group B [3 (2-4)] (p < 0.001), with excellent agreement between the two observers (κ > 0.80). The radiation dose in Group A (average of 2.64 mSv) was 57% lower than the 6.18 mSv in Group B (p < 0.001). The total iodine intake in Group A was 13.5g, 36% lower than the 21g in Group B.

CONCLUSION

Spectral CT imaging with rapid kV-switching in the subtraction angiography in head and neck provides better bone removal with significantly reduced radiation and contrast dose compared with conventional subtraction method. Advances in knowledge: This novel method provides better bone removal with significant radiation and contrast dose reduction compared with the conventional subtraction CT, and maybe used clinically to protect the thyroid gland and ocular lenses from unnecessary high radiation.

Patient Comfort During Contrast Media Injection in Coronary Computed Tomographic Angiography Using Varying Contrast Media Concentrations and Flow Rates: Results From the EICAR Trial

PURPOSE

Pain sensation and extravasation are potential drawbacks of contrast media (CM) injection during computed tomographic angiography. The purpose was to evaluate safety and patient comfort of higher flow rates in different CM protocols during coronary computed tomographic angiography.

METHODS

Two hundred consecutive patients of a double-blind randomized controlled trial (NCT02462044) were analyzed. Patients were randomized to receive 94 mL of prewarmed iopromide 240 mg I/mL at 8.3 mL/s (group I), 75 mL of 300 mg I/mL at 6.7 mL/s (group II), or 61 mL of 370 mg I/mL at 5.4 mL/s (group III), respectively. Iodine delivery rate (2.0 g I/s) and total iodine load (22.5 g I) were kept identical. Outcome was defined as intravascular enhancement, patient comfort during injection, and injection safety, expressed as the occurrence of extravasation. Patients completed a questionnaire for comfort, pain, and stress during CM injection. Comfort was graded using a 5-point scale, 1 representing "very bad" and 5 "very well." Pain was graded using a 10-point scale, 0 representing "no pain" and 10 "severe pain." Stress was graded using a 5-point scale, 1 representing "no stress" and 5 "unsustainable stress."

RESULTS

Mean enhancement levels within the coronary arteries were as follows: 437 ± 104 Hounsfield units (HU) (group I), 448 ± 111 HU (group II), and 447 ± 106 HU (group III), with P ≥ 0.18. Extravasation occurred in none of the patients. Median (interquartile range) for comfort, pain, and stress was, respectively, 4 (4-5), 0 (0-0), and 1 (1-2), with P ≥ 0.68.

CONCLUSIONS

High flow rates of prewarmed CM were safely injected without discomfort, pain, or stress. Therefore, the use of high flow rates should not be considered a drawback for CM administration in clinical practice.

Iodixanol versus Iopromide at Coronary CT Angiography: Lumen Opacification and Effect on Heart Rhythm-the Randomized IsoCOR Trial

Purpose To show that equal coronary lumen opacification can be achieved with iso- and low-osmolar contrast media when it is injected at the same iodine delivery rate with contemporary cardiac computed tomographic (CT) protocols and to investigate the cardiovascular effect of iso-osmolar contrast media and the image quality achieved. Materials and Methods Institutional review board approval and written informed consent were obtained for the Effect of Iso-osmolar Contrast Medium on Coronary Opacification and Heart Rhythm in Coronary CT Angiography, or IsoCOR, trial. Between November 2015 and August 2016, 306 patients (167 [55%] women) at least 18 years old (weight range, 50-125 kg), were prospectively randomized to receive iso-osmolar iodixanol 270 or low-osmolar iopromide 300 contrast media. All coronary segments were assessed for intraluminal opacification and image quality and were compared by using the Student t test. Heart rate, arrhythmia, patient discomfort, and adverse events also were monitored. Results Mean measured coronary attenuation values ± standard deviation were comparable between the iodixanol 270 and iopromide 300 contrast media groups (469 HU ± 167 vs 447 HU ± 166, respectively [P = .241]; 95% confidence interval: -15.1, 60.0), including those from subanalyses. Adjusted for the lower iodine concentration, the mean iodixanol 270 bolus was larger compared with that of iopromide 300 (76.8 mL ± 11.6 vs 69.7 mL ± 10.8, respectively; P < .001). The higher injection rate was associated with higher pressure (777 kPa ± 308 vs 630 kPa ± 252, respectively; P < .001). Although in the iodixanol 270 group patients experienced less heat discomfort (72% vs 86%, respectively; P < .001), no differences in heart rate or rhythm were observed. Conclusion If injected at comparable iodine delivery rates, the iso-osmolar contrast medium iodixanol 270 is not inferior to low-osmolar contrast medium iopromide 300 for assessment of coronary opacification. Iodixanol 270 was associated with less heat discomfort, but did not affect heart rate differently compared with iopromide 300. ^© RSNA, 2017 Online supplemental material is available for this article.

Diagnostic Accuracy, Image Quality, and Patient Comfort for Coronary CT Angiography Performed Using Iso-Osmolar versus Low-Osmolar Iodinated Contrast: A Prospective International Multicenter Randomized Controlled Trial

RATIONALE AND OBJECTIVES

The impact of iso-osmolar versus low-osmolar iodinated contrast on diagnostic accuracy for coronary computed tomography angiography (CCTA), against the reference standard of invasive coronary angiography (ICA), has not been determined. We sought to compare in an international multicenter randomized controlled trial the impact of iso-osmolar iodixanol versus low-osmolar iopamidol on diagnostic accuracy, image quality, patient symptoms, and heart rate variability.

MATERIALS AND METHODS

Adult patients who were clinically referred for ICA were randomly assigned to receive either iodixanol (n = 133) or iopamidol (n = 133) with an investigational CCTA. CCTA stenosis and image quality were scored by consensus of independent blinded core laboratory readers. Degree of stenosis by ICA was evaluated using quantitative coronary angiography and used to calculate diagnostic accuracy. Heart rate variability and patient-reported symptom questionnaires were compared between the two groups.

RESULTS

A total of 266 subjects underwent both CCTA and ICA (57 ± 11 years, 58% male). The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy for detecting coronary artery disease were 86.8%, 93.7%, 84.6%, 94.7%, and 91.7% for iodixanol and 94.7%, 88.4%, 76.6%, 97.7%, and 90.2% for iopamidol, respectively, on a per-patient level. These values were not significantly different between the two groups. There was no significant difference in image quality and heart rate increase or variability. The majority of patients reported symptoms (59.4%), with no differences in the overall or individual rate of any or moderate to severe symptoms between the two groups. Patients receiving iodixanol reported lower incidence of moderate to severe flushing (3.0% vs. 12.8%, P = .005). Lower rates of moderate to severe symptoms were particularly evident for patients with ≥55 years receiving iodixanol versus iopamidol (8.5% vs. 24.6%, P = .01).

CONCLUSIONS

Diagnostic performance and image quality were similar for CCTA performed with iso-osmolar versus low-osmolar iodinated contrast. Indices of patient comfort were improved with iso-osmolar iodinated contrast.

Optimized heart rate for 320-row cardiac CT can be feasibly predicted from prescan parameters

To evaluate the degree of heart rate (HR) changes at rest (HRrest), during breath hold (HRtest), and during cardiac CT examinations (HRscan) in a large group of patients , and to derive and asses the feasibility of a predictive formula for HRscan. HRrest, HRtest, and HRscan were retrospectively compared in a total of 563 consecutive patients who underwent 320-row cardiac CT. Multiple regression analysis was performed to derive predictive formulae for HRscan in the entire study population and, in each group of patients with decreased (Dec) or increased (Inc) HR during breath hold. The predictive formula was evaluated as accurate when less than 5 % of the actual HRscan exceeded the predicted HRscan by ±5 beats per minute (bpm). The average values of the HRtest (65.3 ± 12.0 bpm) and HRscan (63.7 ± 11.9 bpm) significantly decreased from those of the HRrest (68.4 ± 11.9 bpm) (p < 0.0001). The predictive formula (HRscan = 3.601 + 0.113HRrest + 0.8HRtest) was determined to be accurate only in Group Dec. The HRtest significantly decreased from the HRrest, and the HRscan significantly decreased from the HRtest. An accurate predictive formula for HRscan could be built only for Group Dec.

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.

Influence of contrast media viscosity and temperature on injection pressure in computed tomographic angiography: a phantom study

PURPOSE

Iodinated contrast media (CM) in computed tomographic angiography is characterized by its concentration and, consecutively, by its viscosity. Viscosity itself is directly influenced by temperature, which will furthermore affect injection pressure. Therefore, the purposes of this study were to systematically evaluate the viscosity of different CM at different temperatures and to assess their impact on injection pressure in a circulation phantom.

MATERIALS AND METHODS

Initially, viscosity of different contrast media concentrations (240, 300, 370, and 400 mgI/mL) was measured at different temperatures (20°C-40°C) with a commercially available viscosimeter. In the next step, a circulation phantom with physical conditions was used. Contrast media were prepared at different temperatures (20°C, 30°C, 37°C) and injected through a standard 18-gauge needle. All other relevant parameters were kept constant (iodine delivery rate, 1.9 g I/s; total amount of iodine, 15 g I). Peak flow rate (in milliliter per second) and injection pressure (psi) were monitored. Differences in significance were tested using the Kruskal-Wallis test (Statistical Package for the Social Sciences).

RESULTS

Viscosities for iodinated CM of 240, 300, 370, and 400 mg I/mL at 20°C were 5.1, 9.1, 21.2, and 28.8 mPa.s, respectively, whereas, at 40°C, these were substantially lower (2.8, 4.4, 8.7, and 11.2 mPa.s). In the circulation phantom, mean (SD) peak pressures for CM of 240 mg I/mL at 20°C, 30°C, and 37°C were 107 (1.5), 95 (0.6), and 92 (2.1) psi; for CM of 300 mg I/mL, 119 (1.5), 104 (0.6), and 100 (3.6) psi; for CM of 370 mg I/mL, 150 (0.6), 133 (4.4), and 120 (3.5) psi; and for CM of 400 mg I/mL, 169 (1.0), 140 (2.1), and 135 (2.9) psi, respectively, with all P values less than 0.05.

CONCLUSIONS

Low concentration, low viscosity, and high temperatures of CM are beneficial in terms of injection pressure. This should also be considered for individually tailored contrast protocols in daily routine scanning.

Intravascular enhancement with identical iodine delivery rate using different iodine contrast media in a circulation phantom

PURPOSE

Both iodine delivery rate (IDR) and iodine concentration are decisive factors for vascular enhancement in computed tomographic angiography. It is unclear, however, whether the use of high-iodine concentration contrast media is beneficial to lower iodine concentrations when IDR is kept identical. This study evaluates the effect of using different iodine concentrations on intravascular attenuation in a circulation phantom while maintaining a constant IDR.

MATERIALS AND METHODS

A circulation phantom with a low-pressure venous compartment and a high-pressure arterial compartment simulating physiological circulation parameters was used (heart rate, 60 beats per minute; stroke volume, 60 mL; blood pressure, 120/80 mm Hg). Maintaining a constant IDR (2.0 g/s) and a constant total iodine load (20 g), prewarmed (37°C) contrast media with differing iodine concentrations (240-400 mg/mL) were injected into the phantom using a double-headed power injector. Serial computed tomographic scans at the level of the ascending aorta (AA), the descending aorta (DA), and the left main coronary artery (LM) were obtained. Total amount of contrast volume (milliliters), iodine delivery (grams of iodine), peak flow rate (milliliter per second), and intravascular pressure (pounds per square inch) were monitored using a dedicated data acquisition program. Attenuation values in the AA, the DA, and the LM were constantly measured (Hounsfield unit [HU]). In addition, time-enhancement curves, aortic peak enhancement, and time to peak were determined.

RESULTS

All contrast injection protocols resulted in similar attenuation values: the AA (516 [11] to 531 [37] HU), the DA (514 [17] to 531 [32] HU), and the LM (490 [10] to 507 [17] HU). No significant differences were found between the AA, the DA, and the LM for either peak enhancement (all P > 0.05) or mean time to peak (AA, 19.4 [0.58] to 20.1 [1.05] seconds; DA, 21.1 [1.0] to 21.4 [1.15] seconds; LM, 19.8 [0.58] to 20.1 [1.05] seconds).

CONCLUSIONS

This phantom study demonstrates that constant injection parameters (IDR, overall iodine load) lead to robust enhancement patterns, regardless of the contrast material used. Higher iodine concentration itself does not lead to higher attenuation levels. These results may stimulate a shift in paradigm toward clinical usage of contrast media with lower iodine concentrations (eg, 240 mg iodine/mL) in individual tailored contrast protocols. The use of low-iodine concentration contrast media is desirable because of the lower viscosity and the resulting lower injection pressure.

Assessment of vascular contrast and wall motion of the aortic root and ascending aorta on MDCT angiography: dual-source high-pitch vs non-gated single-source acquisition schemes

OBJECTIVES

This retrospective study assessed whether dual-source high-pitch computed tomographic angiography (CTA) offered advantages over single-source standard-pitch techniques in the evaluation of the ascending aorta.

METHODS

Twenty patients who received both thoracic dual-source high-pitch and single-source standard-pitch CTAs within 1 year were assessed. Dual-source CTAs were performed; standard-pitch imaging used dose-modulated 120 kVp/150 mAs and 0.8 pitch compared with high-pitch protocols employing dose-modulated 120 kVp/250 mAs and 2.4 target pitch. Radiation dose was documented. Contrast-to-noise ratios (CNRs) at sinuses of the Valsalva (CNRValsalva) and ascending aorta (CNRAorta) were calculated. Dose/CNR for each technique was compared with paired t-tests. Motion at aortic valve, aortic root and ascending aorta were assessed with four-point scales and Mann-Whitney U tests; longitudinal extension of motion was compared with paired t-tests.

RESULTS

Significantly lower motion scores for high-pitch, compared with standard-pitch acquisitions for aortic annulus, 0 vs. 2, aortic root, 0 vs. 3, and ascending aorta, 0 vs. 2, were achieved. Significantly reduced longitudinal extension of motion at aortic root, 4.9 mm vs 15.7 mm, and ascending aorta, 4.9 mm vs 21.6 mm, was observed. Contrast was not impacted: CNRValsalva, 45.6 vs 46.3, and CNRAorta, 45.3 vs 47.1. CTDIvol was significantly decreased for high-pitch acquisitions, 13.9 mGy vs 15.8 mGy.

CONCLUSIONS

Dual-source high-pitch CTAs significantly decreased motion artefact without negatively impacting vascular contrast and radiation dose.

KEY POINTS

• Dual-source high-pitch CTA significantly decreased motion artefact of the ascending aorta. • Dual-source high-pitch CTA did not negatively impact on vascular contrast. • Dual-source high-pitch CTA significantly decreased radiation dose compared with single-source standard-pitch acquisitions.

CT angiography of the head-and-neck vessels acquired with low tube voltage, low iodine, and iterative image reconstruction: clinical evaluation of radiation dose and image quality

Objectives

We aimed to assess the effectiveness and feasibility of head-and-neck Computed Tomography Angiography (CTA) with low tube voltage and low concentration contrast media combined with iterative reconstruction algorithm.

Methods

92 patients were randomly divided into group A and B: patients in group A received a conventional scan with 120 kVp and contrast media of 320 mgI/ml. Patients in group B, 80 kVp and contrast media of 270 mgI/ml were used along with iterative reconstruction algorithm techniques. Image quality, radiation dose and the effectively consumed iodine amount between two groups were analyzed and compared.

Results

Image quality of CTA of head-and-neck vessels obtained from patients in group B was significantly improved quantitatively and qualitatively. In addition, CT attenuation values in group B were also significantly higher than that in group A (p<0.001). Furthermore, compared with the protocol whereby 120 kVp and 320 mgI/dl were administrated, the mean radiation dose and consumed iodine amount in protocol B were also reduced by 50% and 15.6%, respectively (p<0.001).

Conclusions

With the help of iterative reconstruction algorithm techniques, the head-and-neck CTA with diagnostic quality can be adequately acquired with low tube voltage and low concentration contrast media. This method could be potentially extended to include any part of the body to reduce the risks related to ionizing radiation.