Imaging quality evaluation of low tube voltage coronary CT angiography using low concentration contrast medium

Personalization of CM Injection Protocols in Coronary Computed Tomographic Angiography (People CT Trial)

Aim

To evaluate the performance of three contrast media (CM) injection protocols for cardiac computed tomography angiography (CCTA) based on body weight (BW), lean BW (LBW), and cardiac output (CO). Materials and methods. A total of 327 consecutive patients referred for CCTA were randomized into one of the three CM injection protocols, where CM injection was based on either BW (112 patients), LBW (108 patients), or CO (107 patients). LBW and CO were calculated via formulas. All scans were ECG-gated and performed on a third-generation dual-source CT with 70-120 kV (automated tube voltage selection) and 100 kV_qual.ref/330 mAs_qual.ref. CM injection protocols were also adapted to scan time and tube voltage. The primary outcome was the proportion of patients with optimal intravascular attenuation (325-500 HU). Secondary outcomes were mean and standard deviation of intravascular attenuation values (HU), contrast-to-noise ratio (CNR), and subjective image quality with a 4-point Likert scale (1 = poor/2 = sufficient/3 = good/4 = excellent). The t-test for independent samples was used for pairwise comparisons between groups, and a chi-square test (χ2) was used to compare categorical variables between groups. All p values were 2-sided, and a p < 0.05 was considered statistically significant.

Results

Mean overall HU and CNR were 423 ± 60HU/14 ± 3 (BW), 404 ± 62HU/14 ± 3 (LBW), and 413 ± 63HU/14 ± 3 (CO) with a significant difference between groups BW and LBW (p=0.024). The proportion of patients with optimal intravascular attenuation (325-500 HU) was 83.9%, 84.3%, and 86.9% for groups BW, LBW, and CO, respectively, and between-group differences were small and nonsignificant. Mean CNR was diagnostic (≥10) in all groups. The proportion of scans with good-excellent image quality was 94.6%, 86.1%, and 90.7% in the BW, LBW, and CO groups, respectively. The difference between proportions was significant between the BW and LBW groups.

Conclusion

Personalization of CM injection protocols based on BW, LBW, and CO, and scan time and tube voltage in CCTA resulted in low variation between patients in terms of intravascular attenuation and a high proportion of scans with an optimal intravascular attenuation. The results suggest that personalized CM injection protocols based on LBW or CO have no additional benefit when compared with CM injection protocols based on BW.

Application of Low Tube Voltage, Low-concentration Contrast Agent Using a 320-row CT in Coronary CT Angiography: Evaluation of Image Quality, Radiation Dose and Iodine Intake

The effect of low voltage and low concentration contrast agent on image quality of coronary CT angiography, radiation dose and iodine intake was evaluated. A total of 121 patients with body mass index (BMI) <26 kg/m² and heart rate (HR) <70 beats/min were randomly divided into four groups: group A (n=31, 80 kVp, 270 mgI/mL); group B (n=33, 100 kVp, 270 mgI/mL); group C (n=30, 100 kVp, 320 mgI/mL); group D (n=27, 100 kVp, 400 mgI/mL). The automatic current modulation system and the iterative algorithm for reconstruction were adopted in each group. The CT values and SD values of the aortic root (AR), subcutaneous fat, left coronary artery opening (LCA), and right coronary artery opening (RCA) were measured in all groups, the signal-to-noise ratio (SNR) and contrast noise ratio (CNR) were calculated, and effective radiation dose and iodine intake were recorded. The subjective assessment for image quality was performed by two physicians using a 4-point scale. The results were compared using the one-way ANOVA and rank sum tests. The image quality of the four groups met the clinical diagnostic requirements. The CT values of AR in groups A, B, C, and D were 537.6±71.4, 447.2±81.9, 445.2±64.9 and 518.5±94.9 Hu, respectively, with no significant difference between group A and group D, or between group B and group C, while CT values in groups B and C were significantly lower than those in groups A and D (P<0.05). In groups A, B, C, and D, the LCA SNR values were 22.7±9.1, 23.3±9.1, 23.3±7.7 and 26.6±8.9, and the RCA CNR values were 26.9±9.8, 28.5±11.4, 27.7±8.8 and 32.1±10.6, respectively. The AR visual scores in groups A, B, C and D were 3.8±0.2, 3.9±0.3, 3.9±0.3 and 4.0±0.3, respectively. There were no significant differences in SNR, CNR and visual score among the four groups (P>0.05). The radiation doses in groups A, B, C and D were 2.6±1.4, 3.6±1.8, 4.9±3.5 and 4.9±2.8 mSv, respectively. The radiation dose in group A was significantly less than that in the rest three groups (P<0.05). The iodine intakes in groups A, B, C and D were 14.9±1.5, 15.0±1.5, 17.7±2.0 and 18.1±2.5 g, respectively. There was no significant difference in the intake of iodine between groups C and D, or between groups A and B, while iodine intake in groups A and B were significantly reduced as compared with that in groups C and D (P<0.05). It was concluded that for patients with low BMI and controlled HR, compared to 100 kVp tube voltage combined with multiple concentration contrast agents, 80 kVp combined with 270 mgI/mL contrast agent is enough to ensure the quality of the images, and can reduce the radiation dose significantly, while reducing the amount of iodine intake notably, thus reducing the incidence of adverse reaction.

Diagnosis of coronary artery disease in patients with atrial fibrillation using low tube voltage coronary CT angiography with isotonic low-concentration contrast agent

This prospective study evaluated the image quality and accuracy of coronary computed tomography angiography (CCTA) for diagnosing coronary artery disease (CAD) in patients with atrial fibrillation (AF), in which CCTA used adaptive iterative dose reduction (AIDR) with a low tube voltage and low concentration of isotonic contrast agent. Sixty-eight consecutive patients with AF and suspected CAD were equally and randomly apportioned to two groups and underwent CCTA. In the experimental group, the contrast agent was iodixanol (270 mg I/mL), patients were scanned with 100 kV, and reconstruction was by AIDR. In the conventional scanning (control) group, the contrast agent was iopromide (370 mg I/mL), patients were scanned with 120 kV, and reconstruction was by filtered back projection. The image quality, effective radiation dose (E), and total iodine intake of the groups were compared. Thirty-nine patients with coronary artery stenosis later were given invasive coronary angiography (ICA). The groups were similar with regard to mean CT value, noise, and signal-to-noise and contrast-to-noise ratios. The figure of merit of the experimental group was significantly higher than that of the control group, while the E and total iodine were significantly lower. Using ICA as the diagnostic reference, the groups shared similar sensitivity, specificity, and false positive and false negative rates for diagnosing coronary artery stenosis. For determining CAD in patients with AF, CCTA with isotonic low-concentration contrast agent and low-voltage scanning is a feasible alternative that improves accuracy and reduces radiation dose and iodine intake.

Personalized administration of contrast medium with high delivery rate in low tube voltage coronary computed tomography angiography

Background

High delivery rate is an important factor in optimizing contrast medium administration in coronary computed tomography angiography (CCTA). A personalized contrast volume calculation algorithm incorporating high iodine delivery rate (IDR) can reduce total iodine dose (TID) and produce optimal vessel contrast enhancement (VCE) in low tube voltage CCTA. In this study, we developed and validated an algorithm for calculating the volume of contrast medium delivered at a high rate for patients undergoing retrospectively ECG-gated CCTA with low tube voltage protocol.

Methods

The algorithm for an IDR of 2.22 gI·s^-1 was developed based on the relationship between VCE and contrast volume in 141 patients; test bolus parameters and characteristics in 75 patients; and, tube voltage in a phantom study. The algorithm was retrospectively tested in 45 patients who underwent retrospectively ECG-gated CCTA with a 100 kVp protocol. Image quality, TID and radiation dose exposure were compared with those produced using the 120 kVp and routine contrast protocols.

Results

Age, sex, body surface area (BSA) and peak contrast enhancement (PCE) were significant predictors for VCE (P<0.05). A strong linear correlation was observed between VCE and contrast volume (r=0.97, P<0.05). The 100-to-120 kVp contrast enhancement conversion factor (E_c) was calculated at 0.81. Optimal VCE (250 to 450 HU) and diagnostic image quality were obtained with significant reductions in TID (32.1%) and radiation dose (38.5%) when using 100 kVp and personalized contrast volume calculation algorithm compared with 120 kVp and routine contrast protocols (P<0.05).

Conclusions

The proposed algorithm could significantly reduce TID and radiation exposure while maintaining optimal VCE and image quality in CCTA with 100 kVp protocol.

Assessment of an advanced virtual monoenergetic reconstruction technique in cerebral and cervical angiography with third-generation dual-source CT: Feasibility of using low-concentration contrast medium

OBJECTIVES

To investigate the feasibility of low-concentration contrast media (LC-CM) in cerebral and cervical dual-energy CT angiography (DE-CTA) using an advanced monoenergetic (Mono+) reconstruction technique.

METHODS

Sixty-five consecutive patients prospectively selected to undergo cerebral and cervical DE-CTA were randomised into two groups: 32 patients (63.7 ± 9.7 years) in the high-concentration contrast medium (HC-CM) group with iopromide 370 and 33 patients (60.7 ± 10.8 years) in the low-concentration contrast medium (LC-CM) group with iodixanol 270. Traditional monoenergetic (Mono) and Mono+ images from 40 to 100 keV levels (at 10-keV intervals) and the standard mixed (Mixed, 120 kVp equivalent) images were reconstructed. Subjective image quality parameters included the contrast-to-noise ratio (CNR) and objective image quality parameters were evaluated and compared between the two groups.

RESULTS

The 40-keV Mono+ images in the LC-CM group showed comparable objective CNR (common carotid arteries: 83.7 ± 24.5 vs. 78.1 ± 23.2; internal carotid arteries: 82.2 ± 26.8 vs. 76.8 ± 24.1; middle cerebral arteries: 72.5 ± 24.6 vs. 70.6 ± 19.2; all p > 0.05) and subjective image scores (3.95 ± 0.19 vs. 3.83 ± 0.35; p > 0.05) compared with Mixed images in the HC-CM group.

CONCLUSION

The Mono+ reconstruction technique could reduce the concentration of iodinated CM in the diagnosis of cerebral and cervical angiography.

KEY POINTS

• Mono+ shows decreased noise and superior CNR compared with Mono. • The 40-keV Mono+ images show the highest CNR in the LC-CM group. • The Mono+ reconstruction technique could reduce the concentration of iodinated CM.

Automatic spectral imaging protocol selection combined with iterative reconstruction can enhance image quality and decrease radiation and contrast dosage in abdominal CT angiography

PURPOSE

To investigate the effect of automatic spectral imaging protocol selection (ASIS) and adaptive statistical iterative reconstruction (ASIR) technology in reducing radiation and contrast dosage.

METHODS

Sixty-four patients were randomly divided into two groups for abdominal computed tomography (CT): the experiment group with ASIS plus 50% ASIR and the control with 120 kVp voltage.

RESULTS

The CT dose-index volume decreased by 23.68 and 23.57% and the dose-length product dropped by 25.59 and 18.45% in the arterial and portal venous phases, respectively, in the experiment than control group. The contrast dose was reduced by 16.86% in the experiment group. In the 55 keV + 50% ASIR group, the arterial contrast-to-noise ratio and scores were significantly (P < 0.05) higher than in the control group in the arterial phase while the portal contrast-to-noise ratio and scores were not significantly different between the two groups (P > 0.05).

CONCLUSION

The ASIS technique plus 50% ASIR can enhance image quality of the abdominal structures while decreasing the radiation and contrast dosage compared with the conventional scan mode.

Low tube voltage prospectively ECG-triggered coronary CT angiography: a systematic review of image quality and radiation dose

OBJECTIVE

This study aimed (1) to perform a systematic review on scanning parameters and contrast medium (CM) reduction methods used in prospectively electrocardiography (ECG-triggered low tube voltage coronary CT angiography (CCTA), (2) to compare the achievable dose reduction and image quality and (3) to propose appropriate scanning techniques and CM administration methods.

METHODS

A systematic search was performed in PubMed, the Cochrane library, CINAHL, Web of Science, ScienceDirect and Scopus, where 20 studies were selected for analysis of scanning parameters and CM reduction methods.

RESULTS

The mean effective dose (H_E) ranged from 0.31 to 2.75 mSv at 80 kVp, 0.69 to 6.29 mSv at 100 kVp and 1.53 to 10.7 mSv at 120 kVp. Radiation dose reductions of 38 to 83% at 80 kVp and 3 to 80% at 100 kVp could be achieved with preserved image quality. Similar vessel contrast enhancement to 120 kVp could be obtained by applying iodine delivery rate (IDR) of 1.35 to 1.45 g s^-1 with total iodine dose (TID) of between 10.9 and 16.2 g at 80 kVp and IDR of 1.08 to 1.70 g s^-1 with TID of between 18.9 and 20.9 g at 100 kVp.

CONCLUSION

This systematic review found that radiation doses could be reduced to a rate of 38 to 83% at 80 kVp, and 3 to 80% at 100 kVp without compromising the image quality. Advances in knowledge: The suggested appropriate scanning parameters and CM reduction methods can be used to help users in achieving diagnostic image quality with reduced radiation dose.

Coronary Computed Tomographic Angiography at Low Concentration of Contrast Agent and Low Tube Voltage in Patients with Obesity:: A Feasibility Study

RATIONALE AND OBJECTIVES

Using lower tube voltage can reduce the exposure to radiation and the dose of contrast agent. However, lower tube voltage is often linked to more noise and poor image quality, which create a need for more effective technology to resolve this problem. To explore the feasibility of coronary computed tomographic angiography (CCTA) in patients with obesity at low tube voltage (100 kV) and low contrast agent concentration (270 mg/mL) using iterative reconstruction.

MATERIALS AND METHODS

A total of 48 patients with body mass index greater than 30 kg/m(2) were included and randomly divided into two groups. Group A received a traditional protocol (iopromide 370 mg/mL + 120 kV); group B received a protocol with low tube voltage (100 kV), low contrast agent concentration (270 mg/mL), and iterative reconstruction. The effective dose (ED), average attenuation values, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), the figure of merit (FOM), image quality scores, and the total iodine intake were compared.

RESULTS

No significant differences in average CT attenuations, SNR, CNR, and subjective scores were noticed between the two groups (P > 0.05), whereas the FOM of group B was significantly higher than that of group A. Effective radiation dose, total iodine, and iodine injection rate in group B were lower than those of group A (P <0.01).

CONCLUSIONS

In patients with obesity, isotonic contrast agent with low iodine concentration and low-dose CCTA were feasible. Substantial reduction in radiation dose and the iodine intake could be achieved without compromising the image quality.