IV Contrast Infusion for Coronary Artery CT Angiography: Literature Review and Results of a Nationwide Survey

Contrast Kinetics in CT Coronary Angiography

Computed tomography coronary angiography (CTCA) is a technically demanding radiological investigation that requires adequate opacification of coronary arteries at peak aortic enhancement phase, with minimal or no contrast in the superior vena cava and right-sided cardiac chambers to avoid streak artifacts of dense contrast. Therefore, it is prudent to know about contrast media, contrast kinetics, and contrast injection protocols. This article attempts to describe the essentials of various aspects of contrast media that should be considered for CTCA along with an in-depth analysis of contrast kinetics that every radiologist should know for obtaining adequate opacification of coronary arteries.

Tricuspid Valve Imaging and Right Ventricular Function Analysis Using Cardiac CT and MRI

Cardiac computed tomography (CT) and cardiac magnetic resonance imaging (CMR) can reveal the detailed anatomy and function of the tricuspid valve and right ventricle (RV). Quantification of tricuspid regurgitation (TR) and analysis of RV function have prognostic implications. With the recently available transcatheter treatment options for diseases of the tricuspid valve, evaluation of the tricuspid valve using CT and CMR has become important in terms of patient selection and procedural guidance. Moreover, CT enables post-procedural investigation of the causes of valve dysfunction, such as pannus or thrombus. This review describes the anatomy of the tricuspid valve and CT and CMR imaging protocols for right heart evaluation, including RV function and TR analyses. We also demonstrate the pre-procedural planning for transcatheter treatment of TR and imaging of postoperative complications using CT.

Coronary Computer Tomography Angiography in 2021-Acquisition Protocols, Tips and Tricks and Heading beyond the Possible

Recent technological advances, together with an increasing body of evidence from randomized trials, have placed coronary computer tomography angiography (CCTA) in the center of the diagnostic workup of patients with coronary artery disease. The method was proven reliable in the diagnosis of relevant coronary artery stenosis. Furthermore, it can identify different stages of the atherosclerotic process, including early atherosclerotic changes of the coronary vessel wall, a quality not met by other non-invasive tests. In addition, newer computational software can measure the hemodynamic relevance (fractional flow reserve) of a certain stenosis. In addition, if required, information related to cardiac and valvular function can be provided with specific protocols. Importantly, recent trials have highlighted the prognostic relevance of CCTA in patients with coronary artery disease, which helped establishing CCTA as the first-line method for the diagnostic work-up of such patients in current guidelines. All this can be gathered in one relatively fast examination with minimal discomfort for the patient and, with newer machines, with very low radiation exposure. Herein, we provide an overview of the current technical aspects, indications, pitfalls, and new horizons with CCTA, providing examples from our own clinical practice.

The Incremental Role of Coronary Computed Tomography in Chronic Coronary Syndromes

In the context of chronic coronary syndromes (CCS), coronary computed tomography angiography (CCTA) has gained broad acceptance as a noninvasive anatomical imaging tool with ability of excluding coronary stenosis with strong negative predictive value. Atherosclerotic plaque lesions are independent predictors of cardiovascular outcomes in high risk patients with known coronary artery disease (CAD). Calcium detection is commonly expressed through the coronary artery calcium score (CACS), but further research is warranted to confirm the powerness of a CACS-only strategy in both diagnosis and prognosis assessment. Recent studies evidence how defined plaque composition characteristics effectively relate to the risk of plaque instabilization and the overall ischemic burden. Fractional flow reserve from CCTA (FFR-CT) has been demonstrated as a reliable method for noninvasive functional evaluation of coronary lesions severity, while the assessment of perfusion imaging under stress conditions is growing as a useful tool for assessment of myocardial ischemia. Moreover, specific applications in procedural planning of transcatheter valve substitution and follow-up of heart transplantation have gained recent importance. This review illustrates the incremental role of CCTA, which can potentially revolutionize the diagnosis and management pathway within the wide clinical spectrum of CCS.

Clinical Applications of Wide-Detector CT Scanners for Cardiothoracic Imaging: An Update

Technical developments in multidetector computed tomography (CT) have increased the number of detector rows on the z-axis, and 16-cm wide-area-coverage CT scanners have enabled volumetric scanning of the entire heart. Beyond coronary arterial imaging, such innovations offer several advantages during clinical imaging in the cardiothoracic area. The wide-detector CT scanner markedly reduces the image acquisition time to less than 1 second for coronary CT angiography, thereby decreasing the volume of contrast material and radiation dose required for the examination. It also eliminates stair-step artifacts, allowing robust improvements in myocardial function and perfusion imaging. Additionally, new imaging techniques for the cardiothoracic area, including subtraction imaging and free-breathing scans, have been developed and further improved by using the wide-detector CT scanner. This article investigates the technical developments in wide-detector CT scanners, summarizes their clinical applications in the cardiothoracic area, and provides a review of the recent literature.

An Optimized Test Bolus Contrast Injection Protocol for Consistent Coronary Artery Luminal Enhancement for Coronary CT Angiography

OBJECTIVES

Consistent levels of coronary artery enhancement are essential for quantitative analysis of coronary artery plaque. We studied three contrast injection protocols for coronary CT angiography (CCTA) and compared mean attenuation level and consistency of vascular contrast enhancement. We hypothesized that test bolus adjusted protocols will have a superior consistency of coronary attenuation compared to a weight-based protocol.

MATERIALS AND METHODS

We prospectively evaluated a standard test bolus injection protocol (protocol 1, 32 subjects) and an optimized test bolus injection protocol (protocol 2, 59 subjects) in comparison to a body weight-based injection protocol (60 subjects). The test bolus was diluted contrast (20%-30% iopamidol 370 mixed with normal saline); peak aortic attenuation was measured and used to calculate a specific water/contrast mixture for the CCTA. The mean attenuation of the coronary lumen was measured on CCTA. Metrics of optimum arterial enhancement included the percentage of patients within a predetermined range for coronary attenuation (325-500 HU) and optimal timing with maximal ascending aortic attenuation. In addition, interpatient variation in coronary enhancement was quantified as percentage standard deviation of the attenuation.

RESULTS

The mean attenuation of the coronary arteries was similar in all protocols (362, 364, and 375 HU for the weight-based, test bolus 1 and 2 protocols, respectively). The percentage standard deviations of the weight-based, test bolus 1 and 2 protocols for coronary attenuation were 25.3%, 27.1%, and 10.5%, respectively (p < 0.0001). Test optimized bolus protocol 2 yielded the highest percentage of scans within the preferred coronary attenuation range (88%, p = 0.002). In test bolus protocol 2, the contrast timing was optimal in 73% of cases compared to only 22% of cases in the body mass guided injection protocol (protocol 1, p < 0.0001).

CONCLUSION

An optimized test bolus guided injection protocol resulted in a marked reduction in variation in coronary enhancement for CCTA compared to a body weight-based injection protocol.

Coronary CT Angiography Using Low Iodine Delivery Rate and Tube Voltage Determined by Body Mass Index: Superiority in Clinical Practice

To explore the feasibility and superiority of iodine delivery rate (IDR) and tube voltage determined by patients' body mass index (BMI) in coronary CT angiography (CCTA), a total of 1567 patients undertaking CCTA during Feb. and Dec. 2016 were enrolled and divided into two groups. In the control group, the IDR and tube voltage were fixed, while in the experimental group, the IDR and tube voltage were determined by patients' BMI. The volume of iodinated contrast media (ICM), extravasation rate, extravasation volume, extravasation recovery interval, incidence rate of adverse reactions, effective dose (ED) and image quality of the two groups were compared. The experiments demonstrated that the ICM volume, extravasation rate, extravasation volume, extravasation recovery interval, incidence of adverse reactions and ED were lower or shorter in the experimental group than in the control group, and the differences were statistically significant (all P<0.05). However, there were no significant differences in the mean CT value, image noise, signal to noise ratio and contrast to noise ratio between the two groups (all P<0.05), which were consistent with the diagnosticians' subjective evaluation outcomes. Our findings suggested that in CCTA, it is feasible to determine the IDR and tube voltage based on patients' BMI; low tube voltage and IDR are superior to the fixed tube voltage and IDR and are worthy of clinical promotion.

[Usefulness of Fenestrated Catheters for i.v. Contrast Infusion Cardiac CT Angiography for Newborn Patients during the Congenital Heart Disease]

PURPOSE

A three-dimensional (3D) image from computed tomography (CT) angiography is a useful method for evaluation of complex anatomy such as congenital heart disease. However, 3D imaging requires high contrast enhancement for distinguishing between blood vessels and soft tissue. To improve the contrast enhancement, many are increasing the injection rate. However, one method is the use of fenestrated catheters, it allows use of a smaller gauge catheter for high-flow protocols. The purpose of this study was to compare the pressure of injection rate and CT number of a 24-gauge fenestrated catheter with an 22-gauge non-fenestrated catheter for i.v. contrast infusion during CT.

METHODS

Between December 2014 and March 2015, 50 newborn patients were randomly divided into two protocols; 22-gauge conventional non-fenestrated catheter (24 newborn; age range 0.25-8 months, body weight 3.6±1.2 kg) and 24-gauge new fenestrated catheter (22 newborn; age range 0.25-12 months, body weight 3.3±0.9 kg). Helical scan of the heart was performed using a 64-detector CT (LightSpeed VCT, GE Healthcare) (tube voltage 80 kV; detector configuration 64×0.625 mm, rotation time 0.4 s/rot, helical pitch 1.375, preset noise index for automatic tube current modulation 40 at 0.625 mm slice thickness).

RESULTS

We compared the maximum pressure of injection rate, CT number of aortic enhancement, and CT number of pulmonary artery enhancement between both protocols. The median injection rate, CT number of aortic enhancement, and CT number of pulmonary artery enhancement were 0.9 (0.5-3.4) ml/s, 455.5 (398-659) HU, and 500.0 (437-701) HU in 22-gauge conventional non-fenestrated catheter and 0.9 (0.5-2.0) ml/s, 436.5 (406-632) HU, and 479.5 (445-695) HU in the 24-gauge fenestrated catheter, respectively. There are no significantly different between a 24-gauge fenestrated catheter and 22-gauge non-fenestrated catheters at injection rate and CT number. Maximum pressure of injection rate was lower with 24-gauge non-fenestrated catheters (0.33 kg/cm²) than 22-gauge non-fenestrated catheters (0.55 kg/cm²) (p<0.01Conclusion: A 24-gauge fenestrated catheter performs similarly to an 22-gauge non-fenestrated catheter with respect to i.v. contrast infusion and aortic enhancement levels and can be placed in most subjects whose veins are deemed insufficient for an 22-gauge catheter.

The Usefulness of Fenestrated Intravenous Catheters Compared With Nonfenestrated Catheter for Cardiac Multidetector Computed Tomography

PURPOSE

To compare the fenestrated intravenous (IV) catheter and nonfenestrated conventional IV catheter in terms of contrast enhancement and injection pressure for coronary computed tomography angiography.

METHODS

Three hundred patients were prospectively and consecutively enrolled to either the 20-gauge nonfenestrated conventional (group 1) IV catheter group or the 20-gauge fenestrated (group 2) or 22-gauge fenestrated (group 3) IV catheter groups. We analyzed mean vascular attenuations in the ascending aorta, left main coronary artery, left ventricular (LV) cavity, and descending aorta. Injection pressure using pound-force per square inch (PSI) and extravasation of contrast media were recorded.

RESULTS

Mean attenuations of the left main coronary artery, LV cavity, and descending aorta were significantly higher in group 2 than in group 1 (P ≤ 0.001, P ≤ 0.001, P ≤ 0.001, respectively). Moreover, injection pressure was significantly lower in group 2 than in group 1 (208.3 vs 216.9 PSI, P = 0.006). Mean vascular attenuations of the left main coronary artery, LV cavity, and descending aorta were significantly higher in group 3 than in group 1 (P = 0.016, P = 0.029, P = 0.001, respectively). However, injection pressure was not statistically significant between group 3 and group 1 (213.6 vs 216.9 PSI, P = 0.355). No extravasation occurred in any patient groups during the study.

CONCLUSIONS

We suggest that fenestrated IV catheter is useful in terms of higher vascular attenuation and lower injection pressure for coronary computed tomography angiography. It has a potential merit in patients with fragile and small veins.

Radiation Dose Reduction with a Low-Tube Voltage Technique for Pediatric Chest Computed Tomographic Angiography Based on the Contrast-to-Noise Ratio Index

Introduction

The aim of this study was to evaluate the radiation dose and image quality at low tube-voltage pediatric chest computed tomographic angiography (CTA) that applies the same contrast-to-noise ratio (CNR) index as the standard tube voltage technique.

Materials and Methods

Contrast-enhanced chest CTA scans of 100 infants were acquired on a 64-row multidetector computed tomography (MDCT) scanner. In the retrospective study, we evaluated 50 images acquired at 120 kVp; the image noise level was set at 25 Hounsfield units. In the prospective study, we used an 80-kVp protocol; the image noise level was 40 Hounsfield units because the iodine contrast was 1.6 times higher than on 120-kVp scans; the CNR was as in the 120-kVp protocol. We compared the CT number, image noise, CT dose index volume (CTDIvol), and the dose-length product on scans acquired with the 2 protocols. A diagnostic radiologist and a pediatric cardiologist visually evaluated all CTA images.

Results

The mean CTDIvol and the mean dose-length product were 0.5 mGy and 7.8 mGy-cm for 80- and 1.2 mGy and 20.8 mGy-cm for 120-kVp scans, respectively ( P < .001). The mean CTDIvol was 42% lower at 80 kVp than at 120 kVp, and there was no significant difference in the visual scores assigned to the CTA images ( P = .28).

Conclusions

With the CNR index being the same at 80-kVp and 120-kVp imaging, the radiation dose delivered to infants subjected to chest CTA can be reduced without degradation of the image quality.

Image Quality, Overall Evaluability, and Effective Radiation Dose of Coronary Computed Tomography Angiography With Prospective Electrocardiographic Triggering Plus Intracycle Motion Correction Algorithm in Patients With a Heart Rate Over 65 Beats Per Minute

PURPOSE

Recently, a new intracycle motion correction algorithm (MCA) was introduced to reduce motion artifacts from heart rate (HR) in coronary computed tomography angiography (cCTA). The aim of the study was to evaluate the image quality, overall evaluability, and effective radiation dose (ED) of cCTA with prospective electrocardiographic (ECG) triggering plus MCA as compared with standard protocol with retrospective ECG triggering in patients with HR≥65 bpm.

MATERIALS AND METHODS

One hundred consecutive patients (67±10 y) scheduled for cCTA with 65<HR<80 bpm were retrospectively analyzed. The patients were assigned to 2 groups undergoing prospective (group 1) or retrospective (group 2) triggered cCTA. The study protocol was approved by the Institutional Ethics Committee and a written informed consent was obtained from all patients. Image noise, signal to noise ratio, contrast to noise ratio, Likert image quality score (score 1, nondiagnostic; score 2, adequate; score 3, good; score 4, excellent), overall image evaluability, and ED were measured and compared between the 2 groups. Both vessel-based and patient-based analyses were evaluated. Student test or Wilcoxon test were used to evaluate differences of continuous variables, whereas the χ test was used to study differences with regard to categorical data. A P-value <0.05 was considered statistically significant.

RESULTS

cCTA was successfully performed in all patients. In a segment-based model, group 1 compared with group 2 showed a lower rate of overall artifacts (67% vs. 83%; P<0.001) and motion artifacts (49% vs. 66%; P<0.001), resulting in a better Likert image quality score (2.83±1.03 vs. 2.37±1.02; P<0.01) and overall evaluability (85% vs. 75%; P<0.01). Group 1 showed a lower ED as compared with group 2 (3.1±1.9 vs. 11.9±3.3 mSv; P<0.01).

CONCLUSION

MCA and cCTA with prospective ECG-triggering acquisition in patients with high HR improves image quality and overall evaluability compared with cCTA with standard retrospective ECG triggering.

Evaluation of individually body weight adapted contrast media injection in coronary CT-angiography

OBJECTIVES

Contrast media (CM) injection protocols should be customized to the individual patient. Aim of this study was to determine if software tailored CM injections result in diagnostic enhancement of the coronary arteries in computed tomography angiography (CTA) and if attenuation values were comparable between different weight categories.

MATERIALS AND METHODS

265 consecutive patients referred for routine coronary CTA were scanned on a 2nd generation dual-source CT. Group 1 (n=141) received an individual CM bolus based on weight categories (39-59 kg; 60-74 kg; 75-94 kg; 95-109 kg) and scan duration ('high-pitch: 1s; "dual-step prospective triggering": 7s), as determined by contrast injection software (Certegra™ P3T, Bayer, Berlin, Germany). Group 2 (n=124) received a standard fixed CM bolus; Iopromide 300 mgI/ml; volume: 75 ml; flow rate: 7.2 ml/s. Contrast enhancement was measured in all proximal and distal coronary segments. Subjective and objective image quality was evaluated. Statistical analysis was performed using SPSS (IBM, version 20.0).

RESULTS

For group 1, mean attenuation values of all segments were diagnostic (>325 HU) without statistical significant differences between different weight categories (p>0.17), proximal vs. distal: 449 ± 65-373 ± 58 HU (39-59 kg); 443 ± 69-367 ± 81 HU (60-74 kg); 427 ± 59-370 ± 61 HU (75-94 kg); 427 ± 73-347 ± 61 HU (95-109 kg). Mean CM volumes were: 55 ± 6 ml (39-59 kg); 61 ± 7 ml (60-74 kg); 71 ± 8 ml (75-94 kg); 84 ± 9 ml (95-109 kg). For group 2, mean attenuation values were not all diagnostic with differences between weight categories (p<0.01), proximal vs. distal: 611 ± 142-408 ± 69 HU (39-59 kg); 562 ± 135-389 ± 98 HU (60-74 kg); 481 ± 83-329 ± 81 HU (75-94 kg); 420 ± 73-305 ± 35 HU (95-109 kg). Comparable image noise and image quality were found between groups (p ≥ 0.330).

CONCLUSIONS

Individually tailored CM injection protocols yield diagnostic attenuation and a more homogeneous enhancement pattern between different weight groups. CM volumes could be reduced for the majority of patients utilizing individualized CM bolus application.

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.

Application of 270 mgI/mL Iodinated Contrast Media in Dual-Source Computed Tomography Coronary Artery Imaging

BACKGROUND

This study aimed to explore the application of 270 mg I/mL iodinated contrast agent with a tube voltage of 100 kV scanning in coronary computed tomography angiography (CCTA).

METHODS

This CCTA study was a prospective observational study. The two radiologists were blinded to both patient information and image date arrangement. One-hundred twenty patients (body mass index < 25.0 kg/m(2)) were randomly divided into three groups based on contrast agent concentrations of 370, 320, and 270 mg I/mL, scanning at an injection rate of 5 ml/s. Then, the coronary artery branches of the three groups were compared, and the display rate, mean computed tomography (CT) value, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), image noise, and radiation dose were analyzed.

RESULTS

The artery display rates of the four main branches of coronaries in the three groups were all 100%, and the difference in the display rates of the remaining small branches in the three groups exhibited no statistical significance (p > 0.05). A comparison of the mean CT value of the coronary artery of three groups in the ascending aorta, descending aorta, left main, left ventricular wall, right coronary artery, left anterior descending, and left circumflex showed a statistically significant difference (p < 0.05). A comparison of the SNR, CNR, image noise, and radiation dose showed no statistically significant difference (p > 0.05).

CONCLUSIONS

Using a tube voltage of 100 kV combined with 270 mg I/mL iodinated contrast media in CCTA examination can achieve the "double low dose" effect while ensuring image quality.

KEY WORDS

Contrast agent; Contrast to noise ratio; Coronary angiography; Signal noise ratio.

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.

CT number-controlling system for reproducibility of intracoronary CT number on follow-up coronary CT angiography

BACKGROUND

Coronary computed tomography angiography (CCTA) may be useful for noninvasive follow-up; however, evaluation of coronary stenosis and CT number of plaque may be inaccurate under different vessel enhancement of contrast media. We examined the reproducibility of the CT number of repeat CCTA using our original CT number-controlling system (CTN-CS), which selects contrast level by a multiple regression equation using body surface area and peak CT number and peak time on timing bolus and during CCTA.

METHODS AND RESULTS

One hundred seventy-two patients who underwent serial CCTA were prospectively and randomly assigned to 3 groups. In the first group, Group A, the amount of contrast for the second CCTA was determined by CTN-CS to match the intracoronary CT number of the first CCTA. In Group B, each patient received the same amount of intravenous contrast in both CCTA examinations. In Group C, 0.7 mL/mg body weight (BW) of contrast medium (350 mgI/mL) was used for baseline and follow-up CCTAs. The regression of repeated CCTAs was the best in Group A (r=0.85, p<0.001) vs. Group B (r=0.52, p<0.001), and Group C (r=0.61, p<0.001). The absolute difference between intracoronary CT numbers of the second and first CCTA was the lowest in Group A (24.8 ± 21.8HU), followed by Group B (37.6 ± 26.2 HU; p<0.05) and Group C (46.5 ± 34.4HU; p<0.001).

CONCLUSIONS

Using CTN-CS, the difference of intracoronary CT numbers of the second and first CCTA was the smallest when compared to CCTAs using the same contrast volumes or constant volumes per body weight.

Optimizing contrast medium injection protocol individually with body weight for high-pitch prospective ECG-triggering coronary CT angiography

To individually optimize contrast medium protocol for high-pitch prospective ECG-triggering coronary CT angiography using body weight. Ninety patients undergoing high-pitch coronary CT angiography were randomly assigned to 3 contrast medium injection protocols with bolus tracking technique: Group A, 0.7 ml CM per kg patient weight (ml/kg); Group B, 0.6 ml/kg; Group C, 0.5 ml/kg. Each group had 30 patients. The CT values of superior vena cava (SVC), pulmonary artery (PA), ascending aorta (AA), left atrium (LA), left ventricle (LV), left main artery (LM) and proximal segment of right coronary artery (RCA) were measured. The image quality of coronary artery was evaluated on per-segment basis using a 4-point scale (1-excellent, 4-non-diagnosis). The CT value was not significantly different on AA (p = 0.735), LM (p = 0.764), and proximal segment of RCA (p = 0.991). The CT value was significantly different on SVC, PA, LA and LV (all p < 0.05). The mean image quality score was 1.6 ± 0.1, 1.6 ± 0.1 and 1.6 ± 0.1 (p = 0.217). The volume of CM was 47 ± 8, 44 ± 8 and 36 ± 6 ml for 3 groups (p < 0.001). The effective radiation dose was 0.88 ± 0.04, 0.87 ± 0.06, and 0.85 ± 0.07 mSv for 3 groups. Contrast medium could be reduced to 0.5 ml/kg for high-pitch coronary CT angiography without compromising diagnostic image quality, which associated ~50 % reduction of total contrast volume compared with standard contrast protocol with test bolus technique.

Controlling intracoronary CT number for coronary CT angiography

BACKGROUND

Controlling intracoronary computed tomography (CT) number for coronary CT angiography (CCTA) has been difficult.

OBJECTIVE

The study assessed whether intracoronary CT number of CCTA could be estimated.

METHODS

One hundred twenty six patients were randomly assigned to either CCTA with 30 mL of contrast media (CM) following 5 mL of CM at timing bolus or CCTA with 50 mL of CM following 10 mL of CM at timing bolus. The relationships between intracoronary CT number and patients' characteristics and peak time and peak CT number at timing bolus in patients who showed valid time-density curve were analyzed in both groups. Then, the multiple regression equation best described was made. The prediction system was validated by 112 patients randomly targeted between 250 HU and 430 HU of CT number.

RESULTS

In group 5/30, intracoronary CT number was positively correlated with peak CT number at timing bolus (correlation coefficient, 1.42, p<0.001), negatively correlated with body surface area (-109.19, p<0.001) and peak time (-6.93, p<0.001). Whereas, intracoronary CT number was positively correlated with only peak CT number at timing bolus (1.33, p<0.001) in group 10/50. Then, CT number-controlling system using the simple equation best described CT number was established for CCTA following 5 mL of CM at timing bolus. Of 112 patients, there was good correlation between target CT number and measured CT number (r=0.85, p<0.0001) in 96 patients (85.7%), having valid time-density curve at timing bolus.

CONCLUSIONS

Controlling CT number may be enabled by CT number-controlling system following 5 mL of CM at timing bolus.

Cardiothoracic CT angiography: current contrast medium delivery strategies

OBJECTIVE

Over the last decade, rapid technologic evolution in CT has resulted in improved spatial and temporal resolution and acquisition speed, enabling cardiothoracic CT angiography to become a viable and effective noninvasive alternative in the diagnostic algorithm. These new technologic advances have imposed new challenges for the optimization of contrast medium delivery and image acquisition strategies.

CONCLUSION

Thorough understanding of contrast medium dynamics is essential for the design of effective acquisition and injection protocols. This article provides an overview of the fundamentals affecting contrast enhancement, emphasizing the modifications to contrast material delivery protocols required to optimize cardiothoracic CT angiography.

[Oral versus intravenous beta-blockers for computed tomography coronary angiography? A randomized controlled trial]

OBJECTIVES

To determine whether the time employed in the radiological management of outpatients undergoing computed tomography (CT) coronary angiography varies in function of whether oral or intravenous beta-blockers are administered.

MATERIAL AND METHODS

This was a prospective, analytical, randomized controlled trial. A total of 40 patients with heart rates greater than 65 beats per minute were randomly assigned to one of two groups. Patients in group 1 were administered oral beta-blockers and patients in group 2 were administered intravenous beta-blockers. We measured the overall time from entry to the radiology department to exit from the CT examination room. We also measured heart rate, blood pressure, and the number of conclusive studies.

RESULTS

The median (interquartile range) overall time was 120 (100-150) minutes in the 19 patients who received oral beta-blockers compared to 35 (27.5-67.5) minutes in the 21 patients who received intravenous beta-blockers (p<0.001). The median time that patients were in the CT examination room was 10 (6-15) minutes in Group 1 and 10 (9-20) minutes in Group 2 (p = 0.57). The decrease in mean arterial pressure was 10 mmHg after the administration of intravenous beta-blockers compared to 3.3 mmHg after the administration of oral beta-blockers (p = 0.01). No significant differences were found in the diagnostic quality of the examinations.

CONCLUSIONS

The time employed in the radiological management of patients undergoing CT coronary angiography is significantly lower when beta-blockers are administered intravenously. There was no difference in the time patients were in the CT examination room or in the diagnostic quality of the examinations.

Current contrast media delivery strategies for cardiac and pulmonary multidetector-row computed tomography angiography

Recent advances in multidetector-row computed tomography (MDCT) have led to substantial improvements in coverage area, acquisition speed, and temporal/spatial resolution, which have strengthened the performance of thoracic and cardiac MDCT angiography but have also imposed new challenges for optimization of contrast medium enhancement and scan acquisition strategies. Understanding contrast media dynamics is fundamental for the design of scan acquisition and injection protocols. This article examines the fundamentals of the physiological and contrast delivery factors that determine the quality of contrast enhancement, emphasizing the modifications required in contrast delivery protocols for optimizing cardiothoracic MDCT angiography with modern-era MDCT scanners.

320-row CT coronary angiography: effect of 100-kV tube voltages on image quality, contrast volume, and radiation dose

To prospectively evaluate image quality parameters, contrast volume and radiation dose at the 100-kilovolt (kV) setting during coronary computed tomographic angiography (CCTA) on a 320-row computed tomography scanner. We enrolled 107 consecutive patients with a heart rate <65 beats per minute (bpm) undergoing prospective electrocardiogram (ECG)-triggered CCTA. Forty patients with a body mass index (BMI) <25 kg/m(2) were scanned using 100-kV tube voltage settings, while 67 patients were scanned using 120-kV protocols. Image quality was assessed by two readers unaware of patient information and scan parameters. Attenuation in the aorta and perivascular fat tissue and image noise were measured. Contrast-to-noise ratios (CNRs) and contrast material volumes were calculated. The effective radiation doses were estimated using a chest conversion coefficient (0.017). Diagnostic image quality was achieved in 98.2% of coronary segments with 100-kV CCTA and 98.6% of coronary segments with 120-kV CCTA, with no significant differences in image quality scores for each coronary segment. Vessel attenuation, image noise, and CNR were not significantly different between the 100- and 120-kV protocols. Mean contrast injection rate and mean material volume were significantly lower for the 100-kV CCTA (4.35 ± 0.28 ml/s and 53.13 ± 3.77 ml, respectively) than for the 120-kV CCTA (5.16 ± 0.21 ml/s and 62.40 ± 3.66 ml respectively; P < 0.001). The effective radiation dose was 2.12 ± 0.19 mSv for 100-kV CCTA, a reduction of 54% compared to 4.61 ± 0.82 mSv for 120-kV CCTA. A 100-kV CCTA can be implemented in patients with a BMI < 25 kg/m(2). The 100-kV setting allows significant reductions in contrast material volume and effective radiation dose while maintaining adequate diagnostic image quality.

Strategies for radiation-dose reduction and image-quality optimization in multidetector computed tomographic coronary angiography

The technological evolution of computed tomography (CT) in the last decade has placed CT coronary angiography (CTCA) in the spotlight of imaging modalities available to evaluate patients with coronary artery disease. Widespread utilisation of CTCA has generated concern from the medical community regarding potential health issues related to the significant radiation exposure associated with this method, and several modifications of the CTCA technique have been proposed to reduce the radiation exposure without affecting the diagnostic image quality. This review will discuss a practical approach to performing CTCA to ensure that the radiation dose is minimized while maintaining diagnostic image quality.

X-ray computed tomography of the heart

INTRODUCTION

Cardiac imaging is an emerging application of multidetector computed tomography (MDCT). This review summarizes the current capabilities, possible applications, limitations and developments of cardiac CT.

SOURCES OF DATA

Relevant publications in peer reviewed literature and national and international guidelines are used to discuss important issues in cardiac CT imaging.

AREAS OF AGREEMENT AND CONTROVERSY

There is broad consensus that coronary CT angiography is indicated in patients with an intermediate pre-test probability of coronary artery disease (CAD) when other non-invasive tests have been equivocal. In this context, CT can reliably exclude significant CAD. Cardiac CT also has an established role in the evaluation of bypass grafts and suspected coronary anomalies. Radiation exposure from CT procedures remains a concern, although techniques are now available to reduce the X-ray dosage without significantly compromising the image quality. However, with the current level of knowledge, the cardiac CT examinations are not justified to screen for CAD in asymptomatic individuals. Neither is it considered appropriate in patients with a high pre-test probability of CAD, for whom invasive catheter coronary angiography is usually of more benefit.

GROWING POINTS AND AREAS TIMELY FOR DEVELOPING RESEARCH

The ability to reconstruct the volumetric cardiac CT data set opens up avenues for advanced physiological analyses of the heart. For example, if CT myocardial perfusion assessment becomes a reality, there is potential to revolutionize the practice of MDCT imaging. Research is also ongoing to investigate whether cardiac CT has a role in the appropriate triage of patients with chest pain in the emergency department.

Feasibility of contrast material volume reduction in coronary artery imaging using 320-slice volume CT

OBJECTIVE

To assess reduced volumes of contrast agent on image quality for coronary computed tomography angiography (CCTA) by using single-beat cardiac imaging with 320-slice CT.

MATERIALS AND METHODS

Forty consecutive male patients (mean age: 55.8 years) undergoing CCTA with body weight <or=85 kg, heart rate <or=65 bpm, and ejection fraction >or=55% were included. Image acquisition protocol was standardized (120 kV, 400 mA, and prospective ECG-triggered single-beat nonspiral CCTA). Patients were randomly assigned to one of four groups (G1: received 40 ml, G2: 50 ml, G3: 60 ml, G4: 70 ml). Groups were compared with respect to aortic attenuation, image noise, and image quality.

RESULTS

CT values (mean +/- standard deviation) in the aortic root were measured as 423 +/- 38 HU in G1, and 471 +/- 68, 463 +/- 60, and 476 +/- 78 HU in G2-4, respectively. There were no statistically significant differences in attenuation among the groups (P > 0.068). All 40 CT datasets were rated diagnostic, and image noise and image quality were not statistically different among groups.

CONCLUSION

Using 320-slice volume CT, diagnostic image quality can be achieved with 40 ml of contrast material in CCTA in patients with normal body weight, cardiac function, and low heart rate.