Image quality and diagnostic value of ultra low-voltage, ultra low-contrast coronary CT angiography

Influencing factors and improvement methods of coronary artery plaque evaluation in CT

Accurate evaluation of the nature and composition of coronary plaque involves clinical follow-up and prognosis. Coronary CT angiography is the most commonly non-invasive method for plaque evaluation, however, the qualitative and quantitative evaluation of plaque based on CT value is inaccurate, due to the influence of luminal attenuation, tube voltage, parameter setting and the subjectivity.

Evaluation of image quality on low contrast media with deep learning image reconstruction algorithm in prospective ECG-triggering coronary CT angiography

To assess the impact of low-dose contrast media (CM) injection protocol with deep learning image reconstruction (DLIR) algorithm on image quality in coronary CT angiography (CCTA). In this prospective study, patients underwent CCTA were prospectively and randomly assigned to three groups with different contrast volume protocols (at 320mgI/mL concentration and constant flow rate of 5ml/s). After pairing basic information, 210 patients were enrolled in this study: Group A, 0.7mL/kg (n = 70); Group B, 0.6mL/kg (n = 70); Group C, 0.5mL/kg (n = 70). All patients were examined via a prospective ECG-triggered scan protocol within one heartbeat. A high level DLIR (DLIR-H) algorithm was used for image reconstruction with a thickness and interval of 0.625mm. The CT values of ascending aorta (AA), descending aorta (DA), three main coronary arteries, pulmonary artery (PA), and superior vena cava (SVC) were measured and analyzed for objective assessment. Two radiologists assessed the image quality and diagnostic confidence using a 5-point Likert scale. The CM doses were 46.81 ± 6.41mL, 41.96 ± 7.51mL and 34.65 ± 5.38mL for Group A, B and C, respectively. The objective assessments on AA, DA and the three main coronary arteries and the overall subjective scoring showed no significant difference among the three groups (all p > 0.05). The subjective assessment proved that excellent CCTA images can be obtained from the three different contrast media protocols. There were no significant differences in intracoronary attenuation values between the higher HR subgroup and the lower HR subgroup among three groups. CCTA reconstructed with DLIR could be realized with adequate enhancement in coronary arteries, excellent image quality and diagnostic confidence at low contrast dose of a 0.5mL/kg. The use of lower tube voltages may further reduce the contrast dose requirement.

Effects of low-tube voltage coronary CT angiography on plaque and pericoronary fat assessment: intraindividual comparison

OBJECTIVES

To investigate the effects of low tube voltage on coronary plaques and pericoronary fat assessment, and to compare their extent among various levels of low voltage.

MATERIALS AND METHODS

Patients were recommended for high-pitch low-tube voltage coronary computed tomography angiography (CCTA), and they were included if they had poor image quality and were referred to a conventional CCTA. The patients were classified into a low-voltage group (with 70-kV, 80-kV, and 90-kV subgroups) and a conventional group (100/120 kV). Their total plaque and subcomponent volumes and pericoronary fat attenuation index (FAI) were measured.

RESULTS

A total of 1002 image slices (from 65 patients and 74 plaques) were included, including 21, 31, 13, 4, and 61 patients in the 70-kV, 80-kV, 90-kV, 100-kV, and 120-kV groups respectively. The CT values of noncalcified plaques in the conventional and low-voltage groups were 54.6 ± 21.3 HU and 31.5 ± 22.6 HU, respectively (p < 0.05). Compared with the conventional group, the necrotic core and calcification volume were increased, and the fibrolipid volume, periplaque, and right coronary artery FAI were decreased in the low-voltage group and its subgroups (p < 0.001). The magnitude of changes in fibrous and calcification volumes increased in the 70-kV subgroup compared with that in the 90-kV subgroup (p < 0.05).

CONCLUSION

Low tube voltages, particularly of 70 kV, have a significant effect on coronary plaque and FAI. The effect of low voltage on plaque composition is characterized by a polarization pattern, i.e., a decrease in fibrolipid (medium density) and an increase in necrotic core (low density) and calcification (high density).

CLINICAL RELEVANCE STATEMENT

Our results highlight the comparability and repeatability of plaque and pericoronary fat assessments facilitated by the same or a similar tube voltage. It is necessary to carry out studies on the specificity threshold of low tube voltage at each level.

KEY POINTS

• Low tube voltage had a significant effect on coronary plaque and pericoronary fat, particularly 70 kV. • The effect of low tube voltage on plaque composition shows the shift from medium-density mixed components to low- and high-density components. • It is necessary to correct the specificity threshold or attenuation difference for low tube voltage at each level.

Computed tomography and nuclear medicine for the assessment of coronary inflammation: clinical applications and perspectives

There is increasing evidence that in patients with atherosclerotic cardiovascular disease (ASCVD) under optimal medical therapy, a persisting dysregulation of the lipid and glucose metabolism, associated with adipose tissue dysfunction and inflammation, predicts a substantial residual risk of disease progression and cardiovascular events. Despite the inflammatory nature of ASCVD, circulating biomarkers such as high-sensitivity C-reactive protein and interleukins may lack specificity for vascular inflammation. As known, dysfunctional epicardial adipose tissue (EAT) and pericoronary adipose tissue (PCAT) produce pro-inflammatory mediators and promote cellular tissue infiltration triggering further pro-inflammatory mechanisms. The consequent tissue modifications determine the attenuation of PCAT as assessed and measured by coronary computed tomography angiography (CCTA). Recently, relevant studies have demonstrated a correlation between EAT and PCAT and obstructive coronary artery disease, inflammatory plaque status and coronary flow reserve (CFR). In parallel, CFR is well recognized as a marker of coronary vasomotor function that incorporates the haemodynamic effects of epicardial, diffuse and small-vessel disease on myocardial tissue perfusion. An inverse relationship between EAT volume and coronary vascular function and the association of PCAT attenuation and impaired CFR have already been reported. Moreover, many studies demonstrated that 18F-FDG PET is able to detect PCAT inflammation in patients with coronary atherosclerosis. Importantly, the perivascular FAI (fat attenuation index) showed incremental value for the prediction of adverse clinical events beyond traditional risk factors and CCTA indices by providing a quantitative measure of coronary inflammation. As an indicator of increased cardiac mortality, it could guide early targeted primary prevention in a wide spectrum of patients. In this review, we summarize the current evidence regarding the clinical applications and perspectives of EAT and PCAT assessment performed by CCTA and the prognostic information derived by nuclear medicine.

Comparison of Coronary Computed Tomography Angiography Image Quality With High-concentration and Low-concentration Contrast Agents: The Randomized CONCENTRATE Trial

PURPOSE

To confirm that the image quality of coronary computed tomography (CT) angiography with a low tube voltage (80 to 100 kVp), iterative reconstruction, and low-concentration contrast agents (iodixanol 270 to 320 mgI/mL) was not inferior to that with conventional high tube voltage (120 kVp) and high-concentration contrast agent (iopamidol 370 mgI/mL).

MATERIALS AND METHODS

This prospective, multicenter, noninferiority, randomized trial enrolled a total of 318 patients from 8 clinical sites. All patients were randomly assigned 1: 1: 1 for each contrast medium of 270, 320, and 370 mgI/mL. CT scans were taken with a standard protocol in the high-concentration group (370 mgI/mL) and with 20 kVp lower protocol in the low-concentration group (270 or 320 mgI/mL). Image quality and radiation dose were compared between the groups. Image quality was evaluated with a score of 1 to 4 as subject image quality.

RESULTS

The mean HU, signal-to-noise ratio, and contrast-to-noise ratio of the 3 groups were significantly different (all P<0.0001). The signal-to-noise ratio and contrast-to-noise ratio of the low-concentration groups were significantly lower than those of the high-concentration group (P<0.05). However, the image quality scores were not significantly different among the 3 groups (P=0.745). The dose length product and effective dose of the high-concentration group were significantly higher than those of the low-concentration group (P<0.0001 and 0.003, respectively).

CONCLUSIONS

The CT protocol with iterative reconstruction and lower tube voltage for low-concentration contrast agents significantly reduced the effective radiation dose (mean: 3.7±2.7 to 4.1±3.1 mSv) while keeping the subjective image quality as good as the standard protocol (mean: 5.7±3.4 mSv).

Effects of combining multiple dose reduction techniques on coronary computed tomography angiography

BACKGROUND

Coronary computed tomography angiography (CCTA) is the preferred non-invasive examination method for coronary heart disease. However, the radiation from computed tomography has become a concern since public awareness of radiation hazards continue to increase.

AIM

To explore the value of multiple dose reduction techniques for CCTA.

METHODS

Consecutive normal and overweight patients were prospectively divided into two groups: Group A₁, patients who received multiple dose reduction scans (n = 82); and group A₂, patients who received conventional scans (n = 39). The scan parameters for group A₁ were as follows: Isocentric scan, tube voltage = 80 kV, and tube current control using 80% smart milliampere. The scan parameters for group A₂ were as follows: Normal position, tube voltage = 100 kV, and smart milliampere.

RESULTS

The average effective doses (EDs) for groups A₁ and A₂ were 1.13 ± 0.35 and 3.36 ± 1.30 mSv, respectively. There was a statistically significant difference in ED between the two groups (P < 0.01). Furthermore, noise was significantly lower, and both signal-to-noise ratio and contrast signal-to-noise ratio were higher in group A₂ when compared to group A₁ (P < 0.01). Moreover, the subjective image quality (IQ) scores were excellent in both groups, in which there was no significant difference in subjective IQ score between the two groups (P = 0.12).

CONCLUSION

Multiple dose reduction scan techniques can significantly decrease the ED of patients receiving CCTA examinations for clinical diagnosis.

Progress of CT aortic angiography combined with coronary artery in the evaluation of acute aortic syndrome

Acute aortic syndrome (AAS) is a group of cardiovascular diseases that seriously threaten human life and health. AAS patients are often complicated with coronary artery disease and other related diseases, which require rapid and clear clinical diagnosis to avoid serious adverse events. In recent years, with the progress of science and technology, a variety of computer tomography (CT) angiography techniques have been applied in the clinic, and the diagnosis rate of AAS with coronary heart disease (CAD) has greatly increased. At the same time, the development of surgical technology and endovascular repair technology has significantly reduced the mortality and complication rate of AAS surgery. In the clinical diagnosis of AAS and related diseases, CT aortic angiography (CTA) combined with coronary CTA is increasingly applied to identify related diseases. Here, the current research progress on the technique of aortic CTA combined with coronary CTA is reviewed.

Intraindividual evaluation of effects of image filter function on image quality in coronary computed tomography angiography

Objectives

To evaluate whether applying image filters (smooth 3D+ and edge-2) improves image quality in coronary CT angiography (CCTA).

Methods

Ninety patients (routine group) with suspected coronary artery diseases based on 16-cm wide coverage detector CT findings were retrospectively enrolled at a chest pain center from December 2019 to September 2021. Two image filters, smooth 3D+ and edge-2 available on the Advantage Workstation (AW) were subsequently applied to the images to generate the research group (SE group). Quantitative parameters, including CT value, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR), image sharpness and image quality score, and diagnostic accuracy were compared between the two groups.

Results

A total of 900 segments from 270 coronary arteries in 90 patients were analyzed. SNR, CNR, and image sharpness for vessels and image quality scores in the SE group were significantly better than those in the routine group (all p < 0.001). The SE group showed a slightly higher negative predictive value (NPV) on the left anterior descending artery and right coronary artery (RCA) stenosis evaluations, as well as total NPV. The SE group also showed slightly higher sensitivity and accuracy than the routine group on RCA stenosis evaluation.

Conclusion

The use of an image filter combining smooth 3D+ and edge-2 on an AW could improve the image quality of CCTA and increase radiologists' diagnostic confidence.

Comparing feasibility of different tube voltages and different concentrations of contrast medium in coronary CT angiography of overweight patients

OBJECTIVES

To compare image quality, radiation dose, and iodine intake of coronary computed tomography angiography (CCTA) acquired by wide-detector using different tube voltages and different concentrations of contrast medium (CM) for overweight patients.

MATERIALS AND METHODS

A total of 150 overweight patients (body mass index≥25 kg/m2) who underwent CCTA are enrolled and divided into three groups according to scan protocols namely, group A (120 kVp, 370 mgI/ml CM); group B (100 kVp, 350 mgI/ml CM); and group C (80 kVp, 320 mgI/ml CM). The CT values, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and figure-of-merit (FOM) of all images are calculated. Images are subjectively assessed using a 5-point scale. In addition, the CT dose index volume (CTDIvol) and dose length product (DLP) of each patient are recorded. The effective radiation dose (ED) is also calculated. Above data are then statistically analyzed.

RESULTS

The mean CT values, SNR, CNR, and subjective image quality of group A are significantly lower than those of groups B and C (P < 0.001), but there is no significant difference between groups B and C (P > 0.05). FOMs show a significantly increase trend from group A to C (P < 0.001). The ED values and total iodine intake in groups B and C are 30.34% and 68.53% and 10.22% and 16.85% lower than those in group A, respectively (P < 0.001).

CONCLUSION

The lower tube voltage and lower concentration of CM based on wide-detector allows for significant reduction in iodine load and radiation dose in CCTA for overweight patients comparing to routine scan protocols. It also enhances signal intensity of CCTA and maintains image quality.

The ultrafast, high-pitch turbo FLASH mode of third-generation dual-source CT: Effect of different pitch and corresponding SFOV on image quality in a phantom study

PURPOSE

To investigate the effect of different pitches and corresponding scan fields of view (SFOVs) on the image quality in the ultrafast, high-pitch turbo FLASH mode of the third-generation dual-source CT using an anthropomorphic phantom.

METHODS

The phantom was scanned using the ultrafast, high-pitch turbo FLASH protocols of the third-generation dual-source CT with the different pitches and corresponding SFOVs (pitches: 1.55 to 3.2 with increments of 0.1, SFOVs: 50 cm to 35.4 cm). The objective parameters such as the CT number, image noises, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and artifacts index (AI), and image features from the head, chest, and abdomen were compared between the CT images with a pitch of 1.55 and SFOV of Ø 50 cm and a pitch of 3.2 and SFOV of Ø 35.4 cm. Then, the 18 series of CT images of the head, chest, and abdomen were evaluated by three radiologists independently.

RESULTS

The differences in the CT numbers were not statically significant between the CT images with a pitch of 1.55 and SFOV of Ø 50 cm and a pitch of 3.2 and SFOV of Ø 35.4 cm from most body parts and potential combinations (p > 0.05), Most of the image noises and the AI from the images with the pitch of 1.55 were significantly lower than those with the pitch of 3.2 (p < 0.05), and the SNR and CNR from the images with the pitch of 1.55 were higher than those with the pitch of 3.2. There were significant differences in the first-order features and texture features of the head (59.3%, 28.3%), chest (66%, 35.7%), and abdomen (71.6%, 64.7%) (p < 0.05). The subjective image quality was excellent when the pitch was less than 2.0 and gradually decreased with the increasing pitch. In addition, the image quality decreased significantly when the pitch was higher than 3.0 (all k≥0.69), especially in the head and chest.

CONCLUSIONS

In the ultrafast, high-pitch turbo FLASH mode of the third-generation DSCT, increasing the pitch and lowering the corresponding SFOV will change the image features and cause more artifacts degrading the image quality. Specific to the clinical needs, decreasing the pitch not only can expand the SFOV but also can improve the image quality.

Low dose contrast media in step-and-shoot coronary angiography with third-generation dual-source computed tomography: feasibility of using 30 mL of contrast media in patients with body surface area <1.7 m2

Background

Reducing contrast media volume in coronary computed tomography angiography minimizes the risk of adverse events but may compromise diagnostic image quality. We aimed to evaluate coronary computed tomography angiography's diagnostic image quality while using 30 mL of contrast media in patients with a body surface area <1.7 m².

Methods

This prospective study included patients who underwent coronary computed tomography angiography from May 2018 to June 2019. The patients were divided into a low-dose group, who received 30 mL of contrast media, and a routine-dose group, who received contrast media based on body weight. Patient characteristics, coronary computed tomography angiography results, and quantitative and qualitative image results were assessed and compared.

Results

In total, 103 patients with a body surface area <1.7 m² were 53 in the low-dose group and 50 in the routine-dose group. Sex, age, body surface area, body weight, and heart rate were similar between the groups (P>0.05). A contrast media volume of 30±0 mL was used for the low-dose group, and 41.62±4.59 mL was used for the routine-dose group. The low-dose group's computed tomography values were significantly different from those of the routine-dose group (P<0.05). The radiologists demonstrated agreement regarding diagnostic image quality and accuracy (kappa =0.91 and 0.85, respectively).

Conclusions

Using 30 mL of contrast media for coronary computed tomography angiography in patients with a body surface area <1.7 m² provided a suitable diagnostic image quality for coronary artery disease diagnosis. Although radiation doses were similar between the groups, the decreased contrast media volume was likely beneficial for the patients.

Can the Coronary Artery Calcium Score Scan Reduce the Radiation Dose in Coronary Computed Tomography Angiography?

RATIONALE AND OBJECTIVES

Radiation exposure from coronary computed tomography angiography (CCTA) remains a cause for concern. The objective of this study was to investigate whether using the coronary artery calcium score scan (CACS) would reduce the radiation dose for CCTA scanning and the overall radiation exposure (ORE).

MATERIALS AND METHODS

In total, 256 patients were examined with a third-generation dual-source CT (n = 200) or 256-row CT (n = 56), among whom 105 (Group A) and 28 patients (Group B), respectively, underwent CCTA with CACS for field of view planning. The remaining patients, with the scout view for field of view planning, constituted Group A1 and B1. The scanning parameter settings were standardized between groups.

RESULTS

Shorter scan lengths were observed in Group A (9.98 ± 0.79 cm) compared to Group A1 (13.64 ± 1.79 cm; p < 0.001), which also resulted in a lower dose-length product (DLP) in Group A (115.04 ± 64.13) relative to Group A1 (138.67 ± 68.87; p < 0.05). Similarly, shorter scan lengths were found in Group B (14.92 ± 1.17 cm) compared to Group B1 (15.79 ± 0.63 cm; p = 0.001); this resulted in a lower DLP (322.07 ± 45.39) compared to Group B1 (354.34 ± 65.27; p = 0.036). The CACS resulted in an increase in ORE in both groups.

CONCLUSION

CACS may have a critical role in the reduction of radiation dose in CCTA scanning, but the potential effectiveness of CACS in reducing ORE is weak.

Cardiac CT perfusion and FFRCTA: pathophysiological features in ischemic heart disease

Cardiac computed tomography (CCT) has rapidly evolved, becoming a powerful integrated tool for the evaluation of coronary artery disease (CAD), and being superior to other noninvasive methods due to its high accuracy and ability to simultaneously assess both lumen stenosis and atherosclerotic plaque burden. Furthermore, CCT is regarded as an effective gatekeeper for coronary angiography, and carries independent important prognostic information. In the last decade, the introduction of new functional CCT applications, namely CCT perfusion (CCTP) imaging and CT-derived fractional flow reserve (FFR_CTA), has opened the door for accurate assessment of the haemodynamic significance of stenoses. These new CCT technologies, thus, share the unique advantage of assessing both myocardial ischemia and patient-specific coronary artery anatomy, providing an integrated anatomical/functional analysis. In the present review, starting from the pathophysiology of myocardial ischemia, we evaluate the existing evidence for functional CCT imaging and its value in relation to alternative, well-established, non-invasive imaging modalities and invasive indices of ischemia (currently the gold-standard). The knowledge of clinical applications, benefits, and limitations of these new CCT technologies will allow efficient and optimal use in clinical practice in the near future.