Optimization of cardiac MSCT contrast injection protocols: dependency of the main bolus contrast density on test bolus parameters and patients' body weight

Double ROI Timing Bolus Technique to Perform Aortic CT Angiography With a 9-Second Contrast Injection Duration

OBJECTIVE. The purpose of this study was to investigate the feasibility of a double ROI timing bolus technique for performing aortic CT angiography (CTA) with 40 mL of contrast medium over 9 seconds. SUBJECTS AND METHODS. A prospective study from February to July 2018 included 106 patients with clinical indications for evaluation of aortic aneurysm or dissection or suspected aortic disease. Forty-seven of these patients had undergone prior aortic CTA by the conventional method. The scanning speed for the double ROI timing bolus technique was calculated from the time-attenuation curves of the ascending and descending aorta by use of the timing bolus data to synchronize aortic flow. The conventional scan was obtained by injection of 1.7 mL of contrast medium per kilogram of body weight for 25 seconds. Enhancement of six points on the aortoiliac arteries and superior vena cava was measured. The t test was used to compare the values. RESULTS. Use of the double ROI timing bolus method significantly reduced the amount of contrast medium injected compared with the amount for the conventional method (40.0 mL vs 88.0 ± 9.4 mL, p < 0.001). Use of the method significantly increased aortoiliac enhancement (403.3 ± 76.0 HU vs 359.7 ± 61.5 HU, p < 0.001) and significantly decreased enhancement of the superior vena cava (118.9 ± 46.2 HU vs 239.2 ± 130.5 HU, p < 0.001) compared with the conventional method. In the group with prior CTA images available, the effective dose was significantly lower with the double ROI timing bolus than with the conventional method (8.3 ± 1.7 mSv vs 12.4 ± 3.2 mSv, p < 0.01). CONCLUSION. Use of the double ROI timing bolus method can dramatically reduce the amount of contrast medium used during aortic CTA while improving aortic enhancement and reducing radiation dose.

Minimizing individual variations in arterial enhancement on coronary CT angiographs using "contrast enhancement optimizer": a prospective randomized single-center study

OBJECTIVES

To investigate the clinical utility of our newly developed contrast enhancement optimizer (CEO) software for coronary CT angiography (CCTA).

METHODS

We randomly assigned 295 patients (168 males, 127 females, median age 71 years) undergoing CCTA to one of two contrast media injection protocols. Group A (n = 150) was injected with a CEO-selected iodine dose based on patient factors. In group B (n = 145), we used our standard protocol (245 mg I/kg). We recorded the CT number in the ascending aorta and determined whether the CT number was equivalent in groups A and B. For the equivalence test, we adopted 75 Hounsfield units (HU) as the equivalence margin. The standard deviation in the CT number and the rate of patients with an acceptable CT number were compared using the F test and the chi-square test, respectively.

RESULTS

The iodine dose in group A was significantly smaller than that in group B (235.7 vs. 253.6 mg I/kg, p < 0.001). The CT number of the ascending aorta was 428.6 ± 55.5 HU in group A and 436.1 ± 68.7 HU in group B; the 95% confidence interval for the difference between the groups was -4.3 HU to 16.9 HU and within the range of the predetermined equivalence margins. In group A, the variance was significantly smaller than that in group B (p = 0.009). The number of patients with an acceptable CT number was significantly higher in group A than in group B (84.7% vs. 71.7%, p = 0.007).

CONCLUSIONS

The use of our CEO for CCTA studies yielded optimal aortic contrast enhancement in significantly more patients than the standard protocol based on the body weight.

KEY POINTS

• With our contrast enhancement optimizer (CEO) software, optimal and stable aortic enhancement can be obtained on coronary CT angiography scans irrespective of patient factors. • Management of contrast media becomes more appropriate by the CEO software. • The CEO software can control contrast enhancement at different tube voltage levels.

Coronary angiography using second-generation dual source computed tomography: Feasibility of low dose and low flow rate to achieve appropriate individual contrast enhancement using a test bolus-based contrast medium protocol-A CONSORT compliant article

Improved contrast enhancement consistency can be achieved using an individualized contrast media (CM) protocol. This study aimed to assess the feasibility of a low-dose, low-flow rate CM protocol to achieve appropriate individual contrast enhancement using a newly advocated individualized test bolus-based protocol for second-generation dual-source computed tomography angiography.CM containing iodine (370 mg I/mL) was used in this study. A CM flow rate of 3.5 mL/s for patients with a body mass index (BMI) <25.0 kg/m, and 4.5 mL/s for those with BMI ≥25.0 kg/m was used in group 1 (n = 189). An individualized test-bolus based contrast injection protocol was then derived from the information gained from the test bolus and coronary enhancements in group 1. The proposed individualized test-bolus based CM injection protocol was applied in group 2 (n = 219). Ascending aortic attenuations (AAo) were measured and compared with both groups.The contrast enhancement consistency of AAo in group 2 improved significantly (31.8 vs 56.3 Hounsfield units [HU]; P < .001). The number of patients in group 2 with a contrast flow rate ≤3 mL/s was 63 (28.8%), with 77 (35.2%) using a contrast dose ≤40 mL. In group 2, no significant differences in mean AAo were found among subgroups with contrast flow rates ≤3.0, 3.1 to 4.0, 4.1 to 5.0 and >5.0 mL/s (351, 344, 346, and 348 HU, respectively), nor among subgroups with contrast doses ≤40, 41 to 50, 51 to 60, and >60 mL (349, 345, 344, and 350 HU, respectively).Improved individual contrast enhancement uniformity can be achieved using an individualized CM protocol tailored to a test bolus. Approximately, one-third of patients received CM at a flow rate of no more than 3 mL/s and a total dose of no more than 40 mL.

Improved image-quality consistency in coronary CT angiography using a test-bolus-based individually tailored contrast medium injection protocol

AIM

To develop and validate a test bolus (TB)-based quantitative model to create an individualised contrast medium injection protocol for use at coronary computed tomography angiography (CCTA) to improve patient-to-patient uniformity of intracoronary attenuation.

MATERIALS AND METHODS

In the model-building phase, 175 patients who underwent CCTA using a traditional contrast medium injection protocol were recruited. A personalised injection equation was proposed according to the relationship between aortic enhancement and the haemodynamic parameters obtained from the TB. In the model-validation phase, a target aortic enhancement of 350 HU was set. Two hundred and fifteen additional CCTA examinations were performed using the proposed personalised injection model. Comparisons of inter-individual variability between the traditional and the proposed personalised injection protocol were performed.

RESULTS

In the model-building phase, a high positive correlation between aortic enhancement and the haemodynamic parameters obtained from the TB was found. As a result, a personalised injection equation was determined using linear regression. In the model-validation phase, the average aortic enhancement was 350.5 HU, without significant differences from the preset level. Using the TB-based personalised injection protocol, inter-individual variability of aortic enhancement was significantly reduced (71.8 versus 38.9 HU, p<0.001) and patients who were scanned at 100 kVp had a reduction in the average contrast medium flow rate from 4.1 to 3.2 ml/s (p<0.001).

CONCLUSIONS

The proposed TB-based injection protocol can achieve a desired preset and stable aortic enhancement.

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.

Cardiac output obtained from test bolus injections as a factor in contrast injection rate revision of following coronary CT angiography

BACKGROUND

Optimal contrast enhancement is crucial for the detection of coronary artery stenoses and atherosclerotic changes in coronary CT angiography (CTA).

PURPOSE

To demonstrate the feasibility of using the cardiac output (CO) obtained from the test bolus injection data-set (COtest) as a factor in contrast injection rate revision of the following coronary CTA.

MATERIAL AND METHODS

The test bolus injection data-sets of 52 consecutive coronary CTAs were examined. COtest was calculated from the test bolus data-set. Aortic peak enhancement (APE) was measured on the following coronary CTA. We simulated the APE at a fixed contrast injection rate of 4 mL/s (simAPE) in each patient.

RESULTS

The ranges of COtest and simAPE were 2.82-7.56 L/min and 194-527 Hounsfield Units, respectively. There was a significant negative correlation (R = -0.802, P < 0.001) between simAPE and COtest.

CONCLUSION

COtest can be used for injection rate revision on coronary CTA.

Prediction of the attenuation of the ascending aorta using bolus-tracking parameters and heart rate in coronary computed tomography angiography

OBJECTIVE

The purpose of this study was to evaluate the correlation between bolus-tracking parameters and heart rate (HR) with attenuation of the ascending aorta and create a linear regression model for predicting coronary attenuation in coronary computed tomography angiography (CCTA).

METHODS

A total of 50 patients (31 men, 19 women; mean age, 67.2±10.8 y) underwent CCTA using a 320-detector CT scanner. A bolus-tracking scan was performed to optimize the scan timing. The average HR under normal breathing for 10s was recorded just before the bolus-tracking scan started. Attenuation values of the pulmonary artery at 7s (PA7) and 10s (PA10) after the beginning of the injection were recorded during the bolus-tracking scan and the ascending aortic attenuation (CEAAo) was measured during the diagnostic scan.

RESULTS

A positive correlation was observed between PA7 and CEAAo (r=0.41, P=0.003) and PA10 and CEAAo (r=0.66, P<0.0001), and weak negative correlation was observed between HR and CEAAo (r=-0.46, P=0.15). A multivariable linear regression model for predicting CEAAo was evaluated, and the residual error between the predicted and the measured CEAAo was within approximately ±100 HU.

CONCLUSIONS

Coronary attenuation could be predicted using HR and pulmonary artery attenuation during the bolus-tracking method.

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.

Triple-rule-out CT angiography for evaluation of acute chest pain and possible acute coronary syndrome

Triple-rule-out (TRO) computed tomographic (CT) angiography can provide a cost-effective evaluation of the coronary arteries, aorta, pulmonary arteries, and adjacent intrathoracic structures for the patient with acute chest pain. TRO CT is most appropriate for the patient who is judged to be at low to intermediate risk for acute coronary syndrome (ACS) and whose symptoms may also be attributed to acute pathologic conditions of the aorta or pulmonary arteries. Although a regular cardiac rhythm remains an important factor in coronary CT image quality, newer CT scanners with 64 or more detector rows afford rapid electrocardiographically (ECG) gated imaging to provide high-quality TRO CT studies in patients with a heart rate of up to 80 beats per minute. Injection of iodinated contrast material (< or = 100 mL) is tailored to provide simultaneous high levels of arterial enhancement in the coronary arteries and aorta (> 300 HU) and in the pulmonary arteries (> 200 HU). To limit radiation exposure, the TRO CT examination does not include the entire chest but is constrained to incorporate the aortic arch down through the heart. Scanning parameters, including prospective ECG tube current modulation and prospective ECG gating with the "step-and-shoot" technique, are tailored to reduce radiation exposure (optimally, 5-9 mSv). When performed with appropriate attention to timing and technique, TRO CT provides coronary image quality equal to that of dedicated coronary CT angiography and pulmonary arterial images that are free of motion artifact related to cardiac pulsation. In an appropriately selected emergency department patient population, TRO CT can safely eliminate the need for further diagnostic testing in over 75% of patients.

[Optimization of contrast injection protocol for coronary CTA: adjustment of injection iodine volume on test bolus parameters and patients' sex and BSA]

The purpose of this study was to correlate test bolus (TB) parameters and patient information and cardiac function with main bolus (MB) contrast density for 64-slice computed tomography, and to evaluate MB contrast density on a fixed injection rate, in comparison with an injection rate adjusted with TB parameters and patient information. A total of 256 patients underwent coronary CT angiography. In 126 patients (group 1), contrast material was administered at a flow rate of 4 ml/sec. The peak enhancement, the time needed to reach the peak of the TB and cardiac function of the MB were calculated for each patient in this group. The dependency of MB contrast attenuation on these parameters was evaluated. Significant correlations were obtained between the peak density of the TB and the patient's body surface area (BSA) with the enhancement of MB. Furthermore, females showed a higher peak enhancement of MB than males. In view of the results of group 1, in the other 130 patients (group 2) injection protocols were computed by using regression analysis of each patient's attenuation response to a TB and patient sex and BSA. Compared with group 1, the variations of MB contrast density of group 2 were reduced. Optimized contrast injection protocols are useful to reduce variations of MB contrast density, by taking these TB parameters and patient sex and BSA into account.