Assessment of image quality of 64-row Dual Source versus Single Source CT coronary angiography on heart rate: A phantom study

Stable patients with suspected myocardial ischemia: comparison of machine-learning computed tomography-based fractional flow reserve and stress perfusion cardiovascular magnetic resonance imaging to detect myocardial ischemia

BACKGROUND

Machine-Learning Computed Tomography-Based Fractional Flow Reserve (CT-FFR_ML) is a novel tool for the assessment of hemodynamic relevance of coronary artery stenoses. We examined the diagnostic performance of CT-FFR_ML compared to stress perfusion cardiovascular magnetic resonance (CMR) and tested if there is an additional value of CT-FFR_ML over coronary computed tomography angiography (cCTA).

METHODS

Our retrospective analysis included 269 vessels in 141 patients (mean age 67 ± 9 years, 78% males) who underwent clinically indicated cCTA and subsequent stress perfusion CMR within a period of 2 months. CT-FFR_ML values were calculated from standard cCTA.

RESULTS

CT-FFR_ML revealed no hemodynamic significance in 79% of the patients having ≥ 50% stenosis in cCTA. Chi² values for the statistical relationship between CT-FFR_ML and stress perfusion CMR was significant (p < 0.0001). CT-FFR_ML and cCTA (≥ 70% stenosis) provided a per patient sensitivity of 88% (95%CI 64-99%) and 59% (95%CI 33-82%); specificity of 90% (95%CI 84-95%) and 85% (95%CI 78-91%); positive predictive value of 56% (95%CI 42-69%) and 36% (95%CI 24-50%); negative predictive value of 98% (95%CI 94-100%) and 94% (95%CI 90-96%); accuracy of 90% (95%CI 84-94%) and 82% (95%CI 75-88%) when compared to stress perfusion CMR. The accuracy of cCTA (≥ 50% stenosis) was 19% (95%CI 13-27%). The AUCs were 0.89 for CT-FFR_ML and 0.74 for cCTA (≥ 70% stenosis) and therefore significantly different (p < 0.05).

CONCLUSION

CT-FFR_ML compared to stress perfusion CMR as the reference standard shows high diagnostic power in the identification of patients with hemodynamically significant coronary artery stenosis. This could support the role of cCTA as gatekeeper for further downstream testing and may reduce the number of patients undergoing unnecessary invasive workup.

Suspicious breast lesions incidentally detected on chest computer tomography with histopathological correlation

OBJECTIVE

To evaluate incidental breast lesions on chest computed tomography with histopathological correlation. It is important for general radiologist to characterize a breast lesion as benign, indetermined, or sufficiently suspicious to warrant further work-up.

METHODS

A total of 35.000 chest CT examinations were performed between January 2016 and December 2020. 27 patients (mean age 70 years, age range 48-87 years) with incidental breast lesions were identified in this retrospective study. Two radiologists scored incidental breast lesions independently regarding their morphology, and the results were compared to histopathology which was obtained by an ultrasound-guided core needle biopsy or a surgical excision.

RESULTS

Out of 35.000 chest CT examinations, a total of 31 incidental breast lesions in 27 patients were detected. Among the 31 lesions, 23 were malignant and 8 benign. The malignant lesions included 17 carcinomas and 6 metastases (4 lymphomas and 2 melanomas). The benign lesions contained 2 hematomas, 4 fat necrosis, and 2 fibrosis lumps.

CONCLUSION

Chest computed tomography as a standard imaging technique is helpful for evaluation of suspicious breast lesions. This may ultimately influence patient management and lead to further imaging.

Protocol Optimization and Implementation of Dual-Energy and Dual-Source Computed Tomography in Clinical Practice: Field of View, Speed, or Material Separation?

Clinical use of dual-energy computed tomography (DECT) and dual-source computed tomography (DSCT) has been well established for more than a decade. Improved software and decreased postprocessing time have increased the advantages and availability of DECT and DSCT imaging. In this article, we will provide a practical guide for implementation of DECT and DSCT in clinical practice and discuss automated processing and selection of CT protocols in neurologic, cardiothoracic, vascular, body, and musculoskeletal imaging.

A Magnetically Controlled Soft Microrobot Steering a Guidewire in a Three-Dimensional Phantom Vascular Network

Magnetically actuated soft robots may improve the treatment of disseminated intravascular coagulation. Significant progress has been made in the development of soft robotic systems that steer catheters. A more challenging task, however, is the development of systems that steer sub-millimeter-diameter guidewires during intravascular treatments; a novel microrobotic approach is required for steering. In this article, we develop a novel, magnetically actuated, soft microrobotic system, increasing the steerability of a conventional guidewire. The soft microrobot is attached to the tip of the guidewire, and it is magnetically steered by changing the direction and intensity of an external magnetic field. The microrobot is fabricated via replica molding and features a soft body made of polydimethylsiloxane, two permanent magnets, and a microspring. We developed a mathematical model mapping deformation of the soft microrobot using a feed-forward approach toward steering. Then, we used the model to steer a guidewire. The angulation of the microrobot can be controlled from 21.1° to 132.7° by using a magnetic field of an intensity of 15 mT. Steerability was confirmed by two-dimensional in vitro tracking. Finally, a guidewire with the soft microrobot was tested by using a three-dimensional (3D) phantom of the coronary artery to verify steerability in 3D space.

Dual-source CT coronary angiography: effectiveness of radiation dose reduction with lower tube voltage

This study was conducted to investigate the effectiveness of dose-saving protocols in dual-source computed tomography (CT) coronary angiography compared with invasive coronary angiography (ICA). On 50 patients who underwent coronary CT angiography was performed dual-source CT (DSCT) and compared with ICA procedures. Entrance skin dose (ESD), which was measured at the thyroid gland, and effective dose (E) were assessed for both imaging modalities. The mean ESD measured at the thyroid gland was the highest at 120 kVp, followed by the 100 kVp DSCT and the ICA protocols with 4.0±1.8, 2.7±1.0 and 1.1±1.2 mGy, respectively. The mean E was estimated to be 10.3±2.1, 6.2±2.3 and 5.3±3.4 mSv corresponding to the 120-kVp, 100-kVp DSCT and ICA protocols, respectively. The application of 100 kVp in DSCT coronary angiography is feasible only in patients with a low body mass index of <25 kg m(-2), which leads to a significant dose reduction with the radiation dose being equivalent to that of ICA.

Coronary CT angiography with single-source and dual-source CT: comparison of image quality and radiation dose between prospective ECG-triggered and retrospective ECG-gated protocols

BACKGROUND

This study is conducted to investigate and compare image quality and radiation dose between prospective ECG-triggered and retrospective ECG-gated coronary CT angiography (CCTA) with the use of single-source CT (SSCT) and dual-source CT (DSCT).

METHODS

A total of 209 patients who underwent CCTA with suspected coronary artery disease scanned with SSCT (n=95) and DSCT (n=114) scanners using prospective ECG-triggered and retrospective ECG-gated protocols were recruited from two institutions. The image was assessed by two experienced observers, while quantitative assessment was performed by measuring the image noise, the signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR). Effective dose was calculated using the latest published conversion coefficient factor.

RESULTS

A total of 2087 out of 2880 coronary artery segments were assessable, with 98.0% classified as of sufficient and 2.0% as of insufficient image quality for clinical diagnosis. There was no significant difference in overall image quality between prospective ECG-triggered and retrospective gated protocols, whether it was performed with DSCT or SSCT scanners. Prospective ECG-triggered protocol was compared in terms of radiation dose calculation between DSCT (6.5 ± 2.9 mSv) and SSCT (6.2 ± 1.0 mSv) scanners and no significant difference was noted (p=0.99). However, the effective dose was significantly lower with DSCT (18.2 ± 8.3 mSv) than with SSCT (28.3 ± 7.0 mSv) in the retrospective gated protocol.

CONCLUSIONS

Prospective ECG-triggered CCTA reduces radiation dose significantly compared to retrospective ECG-gated CCTA, while maintaining good image quality.

[Radiologists in the emergency department: when and how to use multislice CT]

Chest pain is a challenging clinical problem in the emergency department. Despite advances in clinical diagnosis, many patients with atypical chest pain are needlessly hospitalized and others are mistakenly discharged. Faced with the specific clinical situation in which a patient has chest pain, an initially normal or inconclusive electrocardiogram, and normal cardiac biomarkers, multislice CT has proven useful for ruling out the conditions that involve the greatest morbidity and mortality and for establishing the cause of pain. This article reviews the current usefulness of multislice CT in the diagnostic workup of patients presenting at the emergency department with chest pain. We review the technique, define the most appropriate population, describe the acquisition protocols, and discuss the advantages and disadvantages of each study protocol.

Radiation dose considerations by intra-individual Monte Carlo simulations in dual source spiral coronary computed tomography angiography with electrocardiogram-triggered tube current modulation and adaptive pitch

OBJECTIVES

To evaluate radiation dose levels in patients undergoing spiral coronary computed tomography angiography (CTA) on a dual-source system in clinical routine.

METHODS

Coronary CTA was performed for 56 patients with electrocardiogram-triggered tube current modulation (TCM) and heart-rate (HR) dependent pitch adaptation. Individual Monte Carlo (MC) simulations were performed for dose assessment. Retrospective simulations with constant tube current (CTC) served as reference. Lung tissue was segmented and used for organ and effective dose (ED) calculation.

RESULTS

Estimates for mean relative ED was 7.1 ± 2.1 mSv/100 mAs for TCM and 12.5 ± 5.3 mSv/100 mAs for CTC (P < 0.001). Relative dose reduction at low HR (≤60 bpm) was highest (49 ± 5%) compared to intermediate (60-70 bpm, 33 ± 12%) and high HR (>70 bpm, 29 ± 12%). However lowest ED is achieved at high HR (5.2 ± 1.5 mSv/100 mAs), compared with intermediate (6.7 ± 1.6 mSv/100 mAs) and low (8.3 ± 2.1 mSv/100 mAs) HR when automated pitch adaptation is applied.

CONCLUSIONS

Radiation dose savings up to 52% are achievable by TCM at low and regular HR. However lowest ED is attained at high HR by pitch adaptation despite inferior radiation dose reduction by TCM.

KEY POINTS

• Monte Carlo simulations allow for individual radiation dose calculations. • ECG-triggered tube current modulation (TCM) can effectively reduce radiation dose. • Slow and regular heart rates allow for highest dose reductions by TCM. • Adaptive pitch accounts for lowest radiation dose at high heart rates. • Women receive higher effective dose than men undergoing spiral coronary CT-angiography.

The effect of heart rhythm on patient radiation dose with dual-source cardiac computed tomography

BACKGROUND

To lower the radiation exposure associated with cardiac CT, it is essential to identify all factors that influence radiation dose.

OBJECTIVES

We explored the effect of heart rhythm during scan acquisition on radiation dose with a 64-slice dual-source cardiac CT.

METHODS

Patient and scan data were collected prospectively in 302 consecutive patients referred for a clinical dual-source cardiac CT. Electrocardiograms recorded during acquisition were interpreted by a cardiologist and categorized as (1) normal sinus rhythm (NSR), (2) premature atrial contraction (PAC) or premature ventricular contraction (PVC), or (3) atrial fibrillation or flutter.

RESULTS

Of the 302 patients, 227 (75.2%) were in NSR and had no ectopy, 55 (18.2%) had PAC/PVC, and 20 (6.6%) had atrial fibrillation or flutter during the scan. Patients with irregular rhythm (PAC/PVC and atrial fibrillation or flutter) were older than patients with regular rhythm (61.0 vs 54.8 years; P = 0.006). Patients with NSR had the lowest estimated radiation dose, followed by PAC/PVC and atrial fibrillation/flutter (9.4, 14.5, 20.9 mSv; P < 0.001). The difference remained significant after adjustments for differences in examination type, tube current and voltage, scan length, pitch, and use of tube current modulation (9.8, 14.1, 17.9 mSv; P < 0.001). No significant association was observed between heart rhythm and subjective image quality although scans with regular rhythm and no ectopy had higher signal-to-noise and contrast-to-noise ratios (P < 0.01).

CONCLUSION

Compared to patients with NSR, patients with atrial fibrillation/flutter had the highest radiation exposure, followed by those with PAC/PVC. Even after adjustment for factors associated with radiation exposure, a significant difference in radiation dose persisted. These findings can be used to identify patients who are more likely to receive higher radiation dose when undergoing cardiac CT and to develop future more-efficient scanner algorithms for use in patients with arrhythmias.

Safety, efficacy, and indications of beta-adrenergic receptor blockade to reduce heart rate prior to coronary CT angiography

For selected indications, coronary computed tomographic (CT) angiography is an established clinical technology for evaluation in patients suspected of having or known to have coronary artery disease. In coronary CT angiography, image quality is highly dependent on heart rate, with heart rate reduction to less than 60 beats per minute being important for both image quality and radiation dose reduction, especially when single-source CT scanners are used. β-Blockers are the first-line option for short-term reduction of heart rate prior to coronary CT angiography. In recent years, multiple β-blocker administration protocols with oral and/or intravenous application have been proposed. This review article provides an overview of the indications, efficacy, and safety of β-blockade protocols prior to coronary CT angiography with respect to different scanner techniques. Moreover, implications for radiation exposure and left ventricular function analysis are discussed.

A model for quantitative correction of coronary calcium scores on multidetector, dual source, and electron beam computed tomography for influences of linear motion, calcification density, and temporal resolution: a cardiac phantom study

PURPOSE

The objective of this study is to quantify the influence of linear motion, calcification density, and temporal resolution on coronary calcium determination using multidetector computed tomography (MDCT), dual source CT (DSCT), and electron beam tomography (EBT) and to find a quantitative method which corrects for the influences of these parameters using a linear moving cardiac phantom.

METHODS

On a robotic arm with artificial arteries with four calcifications of increasing density, a linear movement was applied between 0 and 120 mm/s (step of 10 mm/s). The phantom was scanned five times on 64-slice MDCT, DSCT, and EBT using a standard acquisition protocol. The average Agatston, volume, and mass scores were determined for each velocity, calcification, and scanner. Susceptibility to motion was quantified using a cardiac motion susceptibility (CMS) index. Resemblance to EBT and physical volume and mass was quantified using a Delta index.

RESULTS

Increasing motion artifacts were observed at increasing velocities on all scanners, with increasing severity from EBT to DSCT to 64-slice MDCT. The calcium score showed a linear dependency on motion from which a correction factor could be derived. This correction factor showed a linear dependency on the mean calcification density with a good fit for all three scoring methods and all three scanners (0.73 < or = R2 < or = 0.95). The slope and offset of this correction factor showed a linear dependency on temporal resolution with a good fit for all three scoring methods and all three scanners (0.83 < or = R2 < or = 0.98). CMS was minimal for EBT and increasing values were observed for DSCT and highest values for 64-slice MDCT. CMS was minimal for mass score and increasing values were observed for volume score and highest values for Agatston score. For all densities and scoring methods DSCT showed on average the closest resemblance to EBT calcium scores. When using the correction factor, CMS index decreased on average by 15% and Delta index decreased by 35%.

CONCLUSIONS

Calcium scores determined on DSCT and 64-slice MDCT are highly susceptible to motion as compared to EBT. The mass score is less susceptible to motion compared to volume and Agatston score. Calcium scores determined on DSCT bear a closer resemblance to EBT obtained calcium scores than 64-slice MDCT. In addition, the calcium score is highly dependent on the average density of individual calcifications and the dependency of the calcium score on motion showed a linear behavior on calcification density. From these relations, a quantitative method could be derived which corrects the measured calcium score for the influence of linear motion, mean calcification density, and temporal resolution.

Quantitative image analysis for the detection of motion artefacts in coronary artery computed tomography

Multi detector-row CT (MDCT), the current preferred method for coronary artery disease assessment, is still affected by motion artefacts. To rule out motion artefacts, qualitative image analysis is usually performed. Our study aimed to develop a quantitative image analysis for motion artefacts detection as an added value to the qualitative analysis. An anthropomorphic moving heart phantom with adjustable heart-rate was scanned on 64-MDCT and dual-source-CT. A new software technique was developed which detected motion artefacts in the coronaries and also in the myocardium, where motion artefacts are more apparent; with direct association to the qualitative analysis. The new quantitative analysis managed to detect motion artefacts in phantom scans and relate them to artefact-induced vessel stenoses. Quantifying these artefacts at corresponding locations in the myocardium, artefact-induced vessel stenosis findings could be avoided. In conclusion, the quantitative analysis together with the qualitative analysis rules out artefact-induced stenosis.

Incidental breast lesions detected on CT: what is their significance?

An increasing number of breast lesions are being detected incidentally on CT. The aim of this study was to investigate the rate of referrals to the breast unit for assessment of lesions identified on CT and the resulting yield of previously undiagnosed breast malignancies from this pathway. A retrospective review was undertaken of CT examinations conducted over a period of 14 years. All patients (with no previous history of breast cancer) whose report contained the keyword "breast" and who were referred to a specialist breast unit for assessment were reviewed. CT lesion morphology and enhancement pattern were identified and compared with the final diagnostic outcome. 70 patients were identified by retrospective analysis, yielding 78 incidental breast lesions, of which 22 (28.2%) were malignant (category B5). This gave a positive predictive value (PPV) for malignancy of 28.2%. The best morphological predictor of malignancy was spiculation (PPV, 76%) and irregularity (PPV, 58%), whereas calcification patterns (PPV, 36%) were diagnostically unhelpful. Malignant lesions were likely to be larger (mean, 28.5 mm) than benign lesions (mean, 20.2 mm; p<0.05). In conclusion, 30% of incidental breast lesions in this large series of patients proved to be unsuspected breast cancers, particularly irregular spiculated masses. Referral for formal triple assessment of CT-diagnosed breast lesions is worthwhile, and careful examination of the breast should be a routine part of CT examinations.