Coronary calcium scoring using virtual non-contrast reconstructions on a dual-layer spectral CT system: Feasibility in the clinical practice

PURPOSE

To evaluate the clinical applicability of a prototype virtual non-contrast (VNC) reconstruction algorithm based on coronary CT angiography (cCTA) to assess calcified coronary plaques by calcium scoring (CACS).

METHODS

Eighty consecutive patients suspected of coronary artery disease were retrospectively included. All patients underwent a cardiac CT using a dual-layer spectral-detector CT system. The standardized acquisition protocol included unenhanced CACS and cCTA. Datasets were acquired using 120 keV. VNC-reconstructions were calculated from the cCTA images at 2.5 mm (VNC group 1), 2.5 of 0.9 mm (group 2), and 0.9 mm (group 3) slice thickness. We compared the Agatston score and Coronary Artery Calcium Data and Reporting System (CAC-DRS) of all VNC reconstructions with the true non-contrast (TNC)-dataset as the gold standard.

RESULTS

In total, 73 patients were evaluated. Fifty patients (68.5 %) had a CACS > 0 based on TNC. We found a significant difference in the Agatston score comparing all VNC-reconstructions (1: 1.35, 2: 3.7, 3: 10.4) with the TNC dataset (3.8) (p < 0.001). Correlation analysis of the datasets showed an excellent correlation of the TNC results with the different VNC-reconstructions (r = 0.904-0.974, p < 0.001) with a slope of 1.89-2.53. Mean differences and limits of agreement by Bland-Altman analysis between TNC and group 1 were 83 and -196 to 362, respectively. By using the VNC-reconstructions, in group 1 23 patients (31.5 %), in group 2 10 (13.7 %), and in group 3 23 (31.5 %) were reclassified according to CAC-DRS compared to TNC. Classification according to CAC-DRS revealed a significant difference between TNC and group 1 (p = 0.024) and no significance compared to groups 2 and 3 (p = 0.670 and 0.273).

CONCLUSION

The investigated VNC reconstruction algorithm of routine cCTA allows the detection and evaluation of coronary calcium burden without the requirement for an additional acquisition of an unenhanced CT scan for CACS and, therefore, a reduction of radiation exposure.

Pericoronary adipose tissue attenuation leads to improved prognostication beyond atherosclerotic burden and high-risk plaques in patients with suspected coronary artery disease

Funding Acknowledgements

Type of funding sources: None.

Background

Inflammation is a key component in the atherosclerotic process, initiating and sustaining plaques and serving as a trigger for plaque rupture leading to myocardial infarction. Coronary computed tomography angiography (CCTA) derived pericoronary adipose tissue attenuation (PCATa) has been proposed as surrogate marker for coronary inflammation and might improve risk assessment on top of CCTA derived cardiovascular risk-factors: atherosclerotic burden and plaque vulnerability.

Purpose

To assess the prognostic value of PCATa beyond atherosclerotic burden and high-risk plaques (HRPs).

Methods

A total of 543 patients who underwent CCTA because of suspected CAD were included. CCTA assessment comprised coronary artery calcium score (CACS), presence of obstructive CAD (≥50% stenosis) and HRPs, total plaque volume (TPV), non-calcified plaque volume (NCPV), and PCATa. The endpoint was a composite of death and non-fatal myocardial infarction (MI). Prognostic thresholds were determined for quantitative CCTA variables.

Results

During a median follow-up of 6.6 [interquartile range: 4.7-7.8] years, the endpoint was observed in 42 (20 MI/22 death) patients. CACS &gt;83, obstructive CAD, HRPs, TPV &gt;269mm3, and NCPV &gt;83mm3 were associated with shorter time to the endpoint with unadujsted hazard ratio’s (HR) of 5.37 (95% confidence interval (CI): 2.56-11.29), 5.70 (95% CI: 2.40-13.55), 3.31 (95% CI: 1.80-6.07), 7.76 (95% CI: 3.59-16.81), and 6.77 (95% CI: 3.24-14.16), respectively (p &lt; 0.001 for all). PCATa of the RCA &gt;-74.4 Hounsfield units was associated with worse prognosis (unadjusted HR: 1.99, 95% CI: 1.04-3.79, p = 0.037), whereas PCATa of the LAD and Cx were not associated with prognosis. PCATa of the RCA remained a significant predictor of death and non-fatal MI corrected for CCTA variables and clincal chacteristics associated with the endpoint (adjusted HR: 2.11, 95% CI: 1.11-4.04, p = 0.024).

Conclusion

Coronary inflammation determined by PCATa of the RCA provides incremental prognostic value beyond clinical characteristics and comprehensive CCTA assessment.

Abstract Figure. Take-home figure

Incremental prognostic value of pericoronary adipose tissue attenuation on top of comprehensive CCTA assessment

Background

Coronary computed tomography angiography (CCTA) derived parameters linked to severity and extent of atherosclerosis are associated with prognosis in patients with coronary artery disease (CAD). Furthermore, coronary inflammation, by determining pericoronary adipose tissue CT-attenuation (PCATa), can be assessed on CCTA as well and has been proposed as promising prognostic marker.

Objective

To assess the prognostic value of PCATa on top of traditional CCTA derived atherosclerotic parameters.

Methods

A total of 543 patients who underwent CCTA because of suspected CAD and in whom follow-up was obtained were included. CCTA assessment comprised; coronary artery calcium score (CACS), presence of obstructive CAD (≥50% stenosis) and high-risk plaques (HRP), total plaque volume (TPV), non-calcified plaque volume (NCPV), and PCATa. The endpoint was a composite of death and non-fatal myocardial infarction (MI). Optimal prognostic thresholds were determined for quantitative CCTA variables. Univariable Cox regression analyses were performed to determine clinical characteristics and CCTA variables associated with the endpoint, a subsequent multivariable Cox regression analysis that included variables associated with the endpoint was used to determine independent predictors of the endpoint. An additional Cox regression analysis was performed to test the incremental prognostic value of CCTA variables over clinical characteristics, significance of each sequentially added variable was tested using the likelihood ratio test.

Results

During a median follow-up time of 6.6 [interquartile range: 4.7–7.8] years, a total of 42 (20 MI/22 death) (8%) patients suffered an endpoint. CACS &gt;83.2, obstructive CAD, HRP, TPV &gt;269mm3, and NCPV &gt;83mm3 were all associated with occurrence of the endpoint with unadujsted hazard ratio's (HR) of; 5.37, 5.70, 3.31, 7.76, and 6.77, respectively (p&lt;0.001 for all). PCATa of the RCA above −74.4 Hounsfield units (HU) had a detrimental effect on prognosis (unadjusted HR: 1.99, p=0.037), while PCATa of the LAD nor Cx was associated with outcome (Log-rank p-value 0.255 and 0.218, respectively). PCATa of the RCA remained an independent predictor of death and MI when incorporated in a multivariable analysis inlcuding all CCTA variables and clincal chacteristics associated with the endpoint (adjusted HR: 2.11, p=0.024). Furthermore, adding PCATa of the RCA to a model that included clinical characteristics and all CCTA parameters led to an improvement of the prognostic value of the model (change in Chi-square = 4.45, p=0.035) (figure).

Conclusion

Coronary inflammation of the RCA determined by PCATa provides incremental prognostic value on top of traditional CCTA parameters linked to extent and severity of CAD.

Figure 1. Cox regression analysis demonstrating the incremental prognostic value of sequentially added CCTA variables over clinical characteristics tested for significance using the likelihood ratio test.

Funding Acknowledgement

Type of funding source: None

Muscle force augmentation by low-intensity electrical stimulation

In cases of muscle partial deficiency, force augmentation can be achieved by hybrid activation, i.e., by combining electrical stimulation (ES) with volitional activation. In the present study the volitional and electrically-induced torque components are resolved under visual-feedback activation. Isometric contraction of the tibialis anterior (TA) muscle was studied on 5 healthy subjects, using an activation protocol combining ES alone, volitional activation alone and hybrid activation. Ankle torque and TA EMG were measured. A computational algorithm was developed to dissociate the volitional from the overall torque, based on EMG filtering and on pre-measured calibration curves of volitional torque versus EMG. Based on a defined facilitation factor, the results indicate that within the range of stimulation intensities, there exist regions of increased facilitation of the volitional activation of the TA muscle, in which the torque contribution due to the induced activation is higher compared that of the recruitment curve.

Muscle enhancement using closed-loop electrical stimulation: volitional versus induced torque

In cases of partial deficiency of muscle activation capacity, force augmentation can be achieved by hybrid activation, i.e., by combining electrical stimulation (ES) with volitional activation. In this activation modality the shares of the volitional and induced torques within the overall hybrid torque are unknown. The purpose of this study was to suggest a computational approach to parcel out the volitional and stimulation induced components of joint torque generated during combined voluntary and electrical activation of the Tibialis Anterior muscle (TA). For this purpose, isometric contraction of the TA was studied on 5 healthy subjects, using an activation protocol involving ES alone, volitional activation alone and hybrid activation. Ankle torque and TA EMG were measured. A computational algorithm was developed to dissociate the volitional from the overall torque, based on EMG filtering and on pre-measured calibration curves of volitional torque versus EMG. The results indicated that for a certain hybrid torque there is a linear decaying relationship between the induced torque and the volitional torque shares. Moreover, based on a defined enhancement ratio, the results indicate that within the range of stimulation intensities, there exist regions of increased facilitation, in which the stimulation efficiency is higher under combined compared to isolated conditions.