Dynamic stress computed tomography myocardial perfusion for detecting myocardial ischemia: A systematic review and meta-analysis

Imaging biomarkers in cardiac CT: moving beyond simple coronary anatomical assessment

Cardiac computed tomography angiography (CCTA) is considered the standard non-invasive tool to rule-out obstructive coronary artery disease (CAD). Moreover, several imaging biomarkers have been developed on cardiac-CT imaging to assess global CAD severity and atherosclerotic burden, including coronary calcium scoring, the segment involvement score, segment stenosis score and the Leaman-score. Myocardial perfusion imaging enables the diagnosis of myocardial ischemia and microvascular damage, and the CT-based fractional flow reserve quantification allows to evaluate non-invasively hemodynamic impact of the coronary stenosis. The texture and density of the epicardial and perivascular adipose tissue, the hypodense plaque burden, the radiomic phenotyping of coronary plaques or the fat radiomic profile are novel CT imaging features emerging as biomarkers of inflammation and plaque instability, which may implement the risk stratification strategies. The ability to perform myocardial tissue characterization by extracellular volume fraction and radiomic features appears promising in predicting arrhythmogenic risk and cardiovascular events. New imaging biomarkers are expanding the potential of cardiac CT for phenotyping the individual profile of CAD involvement and opening new frontiers for the practice of more personalized medicine.

Advanced CT measures of coronary artery disease with intermediate stenosis in patients with severe aortic valve stenosis

BACKGROUND

Coronary artery disease (CAD) and severe aortic valve stenosis (AS) frequently coexist. While pre-transcatheter aortic valve replacement (TAVR) computed tomography angiography (CTA) allows to rule out obstructive CAD, interpreting hemodynamic significance of intermediate stenoses is challenging. This study investigates the incremental value of CT-derived fractional flow reserve (CT-FFR), quantitative coronary plaque characteristics (e.g., stenosis degree, plaque volume, and composition), and peri-coronary adipose tissue (PCAT) density to detect hemodynamically significant lesions among those with AS and CAD.

MATERIALS AND METHODS

We included patients with severe AS and intermediate coronary lesions (20-80% diameter stenosis) who underwent pre-TAVR CTA and invasive coronary angiogram (ICA) with resting full-cycle ratio (RFR) assessment between 08/16 and 04/22. CTA image analysis included assessment of CT-FFR, quantitative coronary plaque analysis, and PCAT density. Coronary lesions with RFR ≤ 0.89 indicated hemodynamic significance as reference standard.

RESULTS

Overall, 87 patients (age 77.9 ± 7.4 years, 38% female) with 95 intermediate coronary artery lesions were included. CT-FFR showed good discriminatory capacity (area under receiver operator curve (AUC) = 0.89, 95% confidence interval (CI) 0.81-0.96, p < 0.001) to identify hemodynamically significant lesions, superior to anatomical assessment, plaque morphology, and PCAT density. Plaque composition and PCAT density did not differ between lesions with and without hemodynamic significance. Univariable and multivariable analyses revealed CT-FFR as the only predictor for functionally significant lesions (odds ratio 1.28 (95% CI 1.17-1.43), p < 0.001). Overall, CT-FFR ≤ 0.80 showed diagnostic accuracy, sensitivity, and specificity of 88.4% (95%CI 80.2-94.1), 78.5% (95%CI 63.2-89.7), and 96.2% (95%CI 87.0-99.5), respectively.

CONCLUSION

CT-FFR was superior to CT anatomical, plaque morphology, and PCAT assessment to detect functionally significant stenoses in patients with severe AS.

CLINICAL RELEVANCE STATEMENT

CT-derived fractional flow reserve in patients with severe aortic valve stenosis may be a useful tool for non-invasive hemodynamic assessment of intermediate coronary lesions, while CT anatomical, plaque morphology, and peri-coronary adipose tissue assessment have no incremental or additional benefit. These findings might help to reduce pre-transcatheter aortic valve replacement invasive coronary angiogram.

KEY POINTS

• Interpreting the hemodynamic significance of intermediate coronary stenoses is challenging in pre-transcatheter aortic valve replacement CT. • CT-derived fractional flow reserve (CT-FFR) has a good discriminatory capacity in the identification of hemodynamically significant coronary lesions. • CT-derived anatomical, plaque morphology, and peri-coronary adipose tissue assessment did not improve the diagnostic capability of CT-FFR in the hemodynamic assessment of intermediate coronary stenoses.

Feasibility of four-dimensional similarity filter for radiation dose reduction in dynamic myocardial computed tomography perfusion imaging

Rationale and objectives

We aimed to evaluate the impact of four-dimensional noise reduction filtering using a four-dimensional similarity filter (4D-SF) on radiation dose reduction in dynamic myocardial computed tomography perfusion (CTP).

Materials and methods

Forty-three patients who underwent dynamic myocardial CTP using 320-row computed tomography (CT) were included in the study. The original images were reconstructed using iterative reconstruction (IR). Three different CTP datasets with simulated noise, corresponding to 25%, 50%, and 75% reduction of the original dose (300 mA), were reconstructed using a combination of IR and 4D-SF. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were assessed, and CT-derived myocardial blood flow (CT-MBF) was quantified. The results were compared between the original and simulated images with radiation dose reduction.

Results

The median SNR (first quartile-third quartile) at the original, 25%-, 50%-, and 75%-dose reduced-simulated images with 4D-SF was 8.3 (6.5-10.2), 16.5 (11.9-21.7), 15.6 (11.0-20.1), and 12.8 (8.8-18.1) and that of CNR was 4.4 (3.2-5.8), 6.7 (4.6-10.3), 6.6 (4.3-10.1), and 5.5 (3.5-9.1), respectively. All the dose-reduced-simulated CTPs with 4D-SF had significantly higher image quality scores in SNR and CNR than the original ones (25%-, 50%-, and 75%-dose reduced vs. original images, p < 0.05, in each). The CT-MBF in 75%-dose reduced-simulated CTP was significantly lower than 25%-, 50%- dose-reduced-simulated, and original CTPs (vs. 75%-dose reduced-simulated images, p < 0.05, in each).

Conclusion

4D-SF has the potential to reduce the radiation dose associated with dynamic myocardial CTP imaging by half, without impairing the robustness of MBF quantification.

Stress-only dynamic computed tomography perfusion protocol (CTP) alone without computed tomography coronary angiography (CCTA) has limited specificity to diagnose ischemia: A retrospective two-center study

PURPOSE

To investigate diagnostic performance of stress-only dynamic myocardial computed tomography perfusion (CTP) without computed tomography coronary angiography (CCTA) to diagnose ischemia with invasive fractional flow reserve (FFR) as a reference standard.

METHOD

135 datasets (68 positive for ischemia with invasive FFR < 0.8) acquired with a 256-slice CT system (Revolution, GE Healthcare, Chicago, IL, USA) were retrieved, postprocessed with a deep learning-based algorithm (Advanced intelligent Clear-IQ Engine (AiCE), Canon Medical Systems, Otawara, Japan) (FC03/cardiac kernel, 8 mm slice thickness), analyzed using a dedicated workstation (Vitrea research 7.11.0. Vital Images, Minnetonka, MN, USA), and loaded into a clinical workstation (CardIQ, GE Healthcare, Chicago, IL, USA) for review. Ten observers with various experience from two research sites evaluated the post-processed images, perfusion slices and maps to indicate presence vs absence of perfusion defect and its probability (five-point Likert scale). Binary decisions and probability scores were used to calculate sensitivity and specificity for each reader, and to create receiver operating characteristics (ROC) curves, respectively. Furthermore, the correlation coefficient (ICC) was computed. ROC AUC of a purely quantitative analysis was obtained thanks to a color-coded map with a fixed scale superimposed on myocardial walls displaying myocardial blood flow (MBF) values.

RESULTS

The overall case-based sensitivity and specificity for the detection of perfusion deficit were 0.79 and 0.30, respectively. No significant differences were detected in the AUC across readers (p value = 0.66). The AUC values were 0.50, 0.58, 0.63, 0.59, 0.45, 0.60, 0.56, 0.61, 0.52, 0.61. Absolute reader agreement ICC was 0.60 (good agreement) for an average case.

CONCLUSION

Dynamic CTP alone has good sensitivity, but low specificity when analyzed without CCTA. These findings reinforce the need to guide the interpretation functional test with the knowledge of coronary artery anatomy.

Dynamic CT Myocardial Perfusion: The Role of Functional Evaluation in the Diagnosis of Coronary Artery Disease

Coronary computed tomography angiography (CTA) is a widely accepted, non-invasive diagnostic modality for the evaluation of patients with suspected coronary artery disease (CAD). However, a limitation of CTA is its inability to provide information on the hemodynamic significance of the coronary lesion. The recently developed stress dynamic CT perfusion technique has emerged as a potential solution to this diagnostic challenge. Dynamic CT myocardial perfusion provides information on the hemodynamic consequences of coronary stenosis and is used to detect myocardial ischemia. The combination of stress dynamic CT myocardial perfusion with CTA provides a comprehensive assessment that integrates anatomical and functional information. CT myocardial perfusion has been validated in several clinical studies and has shown comparable accuracy to Positron Emission Tomography (PET) and stress magnetic resonance imaging (MRI) in the diagnosis of hemodynamically significant coronary stenosis and superior performance to Single Photon Emission Computed Tomography (SPECT). More importantly, CTP-derived myocardial perfusion has been shown to have a strong correlation with FFR, and the use of CTP results in a reduction of negative catheterizations. In the context of suspected stable coronary artery disease, the CT protocol with dynamic perfusion imaging combined with CTA eliminates the need for additional testing, making it a convenient "one-stop-shop" method and an effective gatekeeper to an invasive approach.

Dynamic myocardial CT perfusion imaging-state of the art

In patients with suspected coronary artery disease (CAD), dynamic myocardial computed tomography perfusion (CTP) imaging combined with coronary CT angiography (CTA) has become a comprehensive diagnostic examination technique resulting in both anatomical and quantitative functional information on myocardial blood flow, and the presence and grading of stenosis. Recently, CTP imaging has been proven to have good diagnostic accuracy for detecting myocardial ischemia, comparable to stress magnetic resonance imaging and positron emission tomography perfusion, while being superior to single photon emission computed tomography. Dynamic CTP accompanied by coronary CTA can serve as a gatekeeper for invasive workup, as it reduces unnecessary diagnostic invasive coronary angiography. Dynamic CTP also has good prognostic value for the prediction of major adverse cardiovascular events. In this article, we will provide an overview of dynamic CTP, including the basics of coronary blood flow physiology, applications and technical aspects including protocols, image acquisition and reconstruction, future perspectives, and scientific challenges. KEY POINTS: • Stress dynamic myocardial CT perfusion combined with coronary CTA is a comprehensive diagnostic examination technique resulting in both anatomical and quantitative functional information. • Dynamic CTP imaging has good diagnostic accuracy for detecting myocardial ischemia comparable to stress MRI and PET perfusion. • Dynamic CTP accompanied by coronary CTA may serve as a gatekeeper for invasive workup and can guide treatment in obstructive coronary artery disease.

Comprehensive Computed Tomography Imaging of Vessel-specific and Lesion-specific Myocardial Ischemia

Coronary computed tomographic angiography (CCTA) has emerged as a fast and robust tool with high sensitivity and excellent negative predictive value for the evaluation of coronary artery disease, but is unable to estimate the hemodynamic significance of a lesion. Advances in computed tomography (CT)-based diagnostic techniques, for example, CT-derived fractional flow reserve and CT perfusion, have helped transform CCTA primarily from an anatomic assessment tool to a technique that is able to provide both anatomic and functional information for a stenosis. With the results of the ISCHEMIA trial published in 2019, these advanced techniques can elevate CCTA into the role of a better gatekeeper for decision-making and can help guide referral for invasive management. In this article, we review the principles, limitations, diagnostic performance, and clinical utility of these 2 functional CT-based techniques in the evaluation of vessel-specific and lesion-specific ischemia.

Non-Contrast and Contrast-Enhanced Cardiac Computed Tomography Imaging in the Diagnostic and Prognostic Evaluation of Coronary Artery Disease

In recent decades, cardiac computed tomography (CT) has emerged as a powerful non-invasive tool for risk stratification, as well as the detection and characterization of coronary artery disease (CAD), which remains the main cause of morbidity and mortality in the world. Advances in technology have favored the increasing use of cardiac CT by allowing better performance with lower radiation doses. Coronary artery calcium, as assessed by non-contrast CT, is considered to be the best marker of subclinical atherosclerosis, and its use is recommended for the refinement of risk assessment in low-to-intermediate risk individuals. In addition, coronary CT angiography (CCTA) has become a gate-keeper to invasive coronary angiography (ICA) and revascularization in patients with acute chest pain by allowing the assessment not only of the extent of lumen stenosis, but also of its hemodynamic significance if combined with the measurement of fractional flow reserve or perfusion imaging. Moreover, CCTA provides a unique incremental value over functional testing and ICA by imaging the vessel wall, thus allowing the assessment of plaque burden, composition, and instability features, in addition to perivascular adipose tissue attenuation, which is a marker of vascular inflammation. There exists the potential to identify the non-obstructive lesions at high risk of progression to plaque rupture by combining all of these measures.

Technical Considerations for Dynamic Myocardial Computed Tomography Perfusion as Part of a Comprehensive Evaluation of Coronary Artery Disease Using Computed Tomography

Dynamic myocardial computed tomography perfusion (DM-CTP) has good diagnostic accuracy for identifying myocardial ischemia as compared with both invasive and noninvasive reference standards. However, DM-CTP has not yet been implemented in the routine clinical examination of patients with suspected or known coronary artery disease. An important hurdle in the clinical dissemination of the method is the development of the DM-CTP acquisition protocol and image analysis. Therefore, the aim of this article is to provide a review of critical parameters in the design and execution of DM-CTP to optimize each step of the examination and avoid common mistakes. We aim to support potential users in the successful implementation and performance of DM-CTP in daily practice. When performed appropriately, DM-CTP may support clinical decision making. In addition, when combined with coronary computed tomography angiography, it has the potential to shorten the time to diagnosis by providing immediate visualization of both coronary atherosclerosis and its functional relevance using one single modality.

Coronary Computed Tomography vs. Cardiac Magnetic Resonance Imaging in the Evaluation of Coronary Artery Disease

Coronary artery disease (CAD) represents a widespread burden to both individual and public health, steadily rising across the globe. The current guidelines recommend non-invasive anatomical or functional testing prior to invasive procedures. Both coronary computed tomography angiography (cCTA) and stress cardiac magnetic resonance imaging (CMR) are appropriate imaging modalities, which are increasingly used in these patients. Both exhibit excellent safety profiles and high diagnostic accuracy. In the last decade, cCTA image quality has improved, radiation exposure has decreased and functional information such as CT-derived fractional flow reserve or perfusion can complement anatomic evaluation. CMR has become more robust and faster, and advances have been made in functional assessment and tissue characterization allowing for earlier and better risk stratification. This review compares both imaging modalities regarding their strengths and weaknesses in the assessment of CAD and aims to give physicians rationales to select the most appropriate modality for individual patients.

The chronic coronary syndrome—Heart failure roundabout: A multimodality imaging workflow approach

Heart failure (HF) is a complex syndrome of considerable burden with high mortality and hospitalization rates. Approximately two-thirds of patients with HF have ischemic etiology, which makes crucial the identification of relevant coronary artery disease (CAD). Moreover, patients with chronic coronary syndrome (CCS) can first show signs of dyspnea and left ventricular (LV) dysfunction. If establishing a diagnosis of HF and consequent management is clear enough, it will not be the same when it comes to recommendations for etiology assessment. Ischemic heart disease is the most studied disease by cardiac multimodality imaging with excellent diagnostic performance. Based on this aspect, the high prevalence of CAD, the worst outcome—HF patients should undergo a diagnostic work-up using these multimodality imaging techniques. The aim of this mini-review is to provide insights on multimodality imaging for diagnosing CCS in patients with new onset of HF and propose a diagnostic work-up based on current international studies and guidelines.

Comparison of diagnostic performance between dynamic versus static adenosine-stress myocardial CT perfusion to detect hemodynamically significant coronary artery stenosis: A prospective multicenter study

Myocardial computed tomography perfusion (CTP) imaging is a noninvasive method for detecting myocardial ischemia. This study aimed to compare the diagnostic performance of dynamic and static adenosine-stress CTPs for detecting hemodynamically significant coronary stenosis. We prospectively enrolled 42 patients (mean age, 59.7 ± 8.8 years; 31 males) with ≥40% coronary artery stenosis. All patients underwent dynamic CTP for adenosine stress. The static CTP was simulated by choosing the seventh dynamic dataset after the initiation of the contrast injection. Diagnostic performance was compared with invasive fractional flow reserve (FFR) <0.8 as the reference. Of the 125 coronary vessels in 42 patients, 20 (16.0%) in 16 (38.1%) patients were categorized as hemodynamically significant. Dynamic and static CTP yielded similar diagnostic accuracy (90.4% vs 88.8% using visual analysis, P = .558; 77.6% vs 80.8% using quantitative analysis, P = .534; 78.4% vs 82.4% using combined visual and quantitative analyses, P = .426). The diagnostic accuracy of combined coronary computed tomography angiography (CCTA) and dynamic CTP (89.6% using visual analysis, P = .011; 88.8% using quantitative analysis, P = .018; 89.6% using combined visual and quantitative analyses, P = .011) and that of combined CCTA and static CTP (88.8% using visual analysis, P = .018; 90.4% using quantitative analysis, P = .006; 91.2% using combined visual and quantitative analyses, P = .003) were significantly higher than that of CCTA alone (77.6%). Dynamic CTP and static CTP showed similar diagnostic performance in the detection of hemodynamically significant stenosis.

Dose Reduction of Dynamic Computed Tomography Myocardial Perfusion Imaging by Tube Voltage Change: Investigation in a Swine Model

Background

It is unclear whether tube voltage influences the measurement of perfusion parameters. The present study sought to evaluate the influence of tube voltage change on myocardial blood flow (MBF) measurements in dynamic computed tomography myocardial perfusion imaging (CTP).

Methods and Results

Seven swine [mean weight 55.8 kg ± 1.6 (standard deviation)] underwent rest and stress dynamic CTP with tube voltages of 100 and 70 kV. The image noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), radiation dose and MBF value were compared. The 70 kV images had higher CT attenuation and higher image noise (27.9 ± 2.4 vs. 21.5 ± 1.9, P < 0.001) than the 100 kV images, resulting in a higher SNR (20.5 ± 1.6 vs. 15.6 ± 1.8, P < 0.001) and CNR (17.6 ± 1.5 vs. 12.4 ± 1.7, P < 0.001). Compared to the use of conventional 100 kV, 70 kV yielded an approximately 64.6% radiation dose reduction while generating comparable MBF values, both at rest (88.3 ± 14.9 ml/100 g/min vs. 85.6 ± 17.4 ml/100 g/min, P = 0.21) and stress (101.4 ± 21.5 ml/100 g/min vs. 99.6 ± 21.4 ml/100 g/min, P = 0.58) states.

Conclusion

Dynamic CTP using 70 kV instead of 100 kV does not substantially influence the MBF value but significantly reduces the radiation dose. Additional research is required to investigate the clinical significance of this change.

Cardiac Imaging Trends from 2010 to 2019 in the Medicare Population

Purpose

To evaluate changes in utilization of cardiac imaging-transthoracic, transesophageal, and stress echocardiography (TTE, TEE, and SE), coronary CT angiography (cCTA), cardiac MRI (cMRI), myocardial perfusion imaging (MPI), and cardiac positron emission tomography (cPET).

Materials and Methods

The 2010-2019 Physician/Supplier Procedure Summary files were used to find imaging utilization per 100 000 Medicare beneficiaries. Global and professional claims were aggregated, representing total interpretive services. Specialty codes identified provider specialty. Results were stratified by physician offices, hospital outpatient departments (HOPDs), inpatient setting, and the emergency department.

Results

From 2010 to 2019, there was a partial shift from cardiologist offices to the HOPD for TTE (office: -23%; HOPD: +107%) and SE (office: -44%; HOPD: +11%). Cardiologist cCTA also shifted from the office (-57%) to the HOPD (+211%). Radiologist-performed cCTA grew in all locations but most in the HOPD (+355%), with radiologists performing more cCTA than cardiologists in all settings. cMRI rates remain low but rose in the HOPD for both cardiologists (+209%) and radiologists (+207%). Cardiologist MPI rates dropped dramatically in the office (-52%), with a smaller absolute rate increase in the HOPD (+71%). cPET nearly tripled in the cardiology office (+193%), but rates remained steady for radiologists.

Conclusion

While most cardiologist in-office imaging has shifted to the HOPD, there has been an increase in in-office cPET, likely due to a combination of technological advances, interpretation familiarity, and financial incentives. Radiologist cCTA rates continue to increase, representing a growing opportunity for radiologists to collaborate in cardiac imaging.Keywords: CT Angiography, Echocardiography, MR Imaging, PET, Radionuclide Studies, SPECT, Cardiac, Work Force Issues Supplemental material is available for this article. © RSNA, 2021.

Dynamic Myocardial Perfusion CT for the Detection of Hemodynamically Significant Coronary Artery Disease

OBJECTIVES

In this international, multicenter study, using third-generation dual-source computed tomography (CT), we investigated the diagnostic performance of dynamic stress CT myocardial perfusion imaging (CT-MPI) in addition to coronary CT angiography (CTA) compared to invasive coronary angiography (ICA) and invasive fractional flow reserve (FFR).

BACKGROUND

CT-MPI combined with coronary CTA integrates coronary artery anatomy with inducible myocardial ischemia, showing promising results for the diagnosis of hemodynamically significant coronary artery disease in single-center studies.

METHODS

At 9 centers in Europe, Japan, and the United States, 132 patients scheduled for ICA were enrolled; 114 patients successfully completed coronary CTA, adenosine-stress dynamic CT-MPI, and ICA. Invasive FFR was performed in vessels with 25% to 90% stenosis. Data were analyzed by independent core laboratories. For the primary analysis, for each coronary artery the presence of hemodynamically significant obstruction was interpreted by coronary CTA with CT-MPI compared to coronary CTA alone, using an FFR of ≤0.80 and angiographic severity as reference. Territorial absolute myocardial blood flow (MBF) and relative MBF were compared using C-statistics.

RESULTS

ICA and FFR identified hemodynamically significant stenoses in 74 of 289 coronary vessels (26%). Coronary CTA with ≥50% stenosis demonstrated a per-vessel sensitivity, specificity, and accuracy for the detection of hemodynamically significant stenosis of 96% (95% CI: 91–100), 72% (95% CI: 66–78), and 78% (95% CI: 73–83), respectively. Coronary CTA with CT-MPI showed a lower sensitivity (84%; 95% CI: 75–92) but higher specificity (89%; 95% CI: 85–93) and accuracy (88%; 95% CI: 84–92). The areas under the receiver-operating characteristic curve of absolute MBF and relative MBF were 0.79 (95% CI: 0.71–0.86) and 0.82 (95% CI: 0.74–0.88), respectively. The median dose-length product of CT-MPI and coronary CTA were 313 mGy·cm and 138 mGy·cm, respectively.

CONCLUSIONS

Dynamic CT-MPI offers incremental diagnostic value over coronary CTA alone for the identification of hemodynamically significant coronary artery disease. Generalized results from this multicenter study encourage broader consideration of dynamic CT-MPI in clinical practice. (Dynamic Stress Perfusion CT for Detection of Inducible Myocardial Ischemia [SPECIFIC]; NCT02810795)

The Incremental Role of Coronary Computed Tomography in Chronic Coronary Syndromes

In the context of chronic coronary syndromes (CCS), coronary computed tomography angiography (CCTA) has gained broad acceptance as a noninvasive anatomical imaging tool with ability of excluding coronary stenosis with strong negative predictive value. Atherosclerotic plaque lesions are independent predictors of cardiovascular outcomes in high risk patients with known coronary artery disease (CAD). Calcium detection is commonly expressed through the coronary artery calcium score (CACS), but further research is warranted to confirm the powerness of a CACS-only strategy in both diagnosis and prognosis assessment. Recent studies evidence how defined plaque composition characteristics effectively relate to the risk of plaque instabilization and the overall ischemic burden. Fractional flow reserve from CCTA (FFR-CT) has been demonstrated as a reliable method for noninvasive functional evaluation of coronary lesions severity, while the assessment of perfusion imaging under stress conditions is growing as a useful tool for assessment of myocardial ischemia. Moreover, specific applications in procedural planning of transcatheter valve substitution and follow-up of heart transplantation have gained recent importance. This review illustrates the incremental role of CCTA, which can potentially revolutionize the diagnosis and management pathway within the wide clinical spectrum of CCS.

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.

Impact of Abnormal Remote Stress Myocardial Blood Flow by Dynamic CT Perfusion on Clinical Outcomes

The objective of this study was to investigate the incremental prognostic value for adverse events of myocardial blood flow (MBF) derived from stress computed tomography perfusion (CTP) at remote myocardium over cardiac risk factors and ischemia. We prospectively analyzed 242 patients who underwent dynamic CTP and CT angiography. Adverse events were defined as a composite of all-cause mortality, non-fatal myocardial infarction, unstable angina, heart failure requiring hospitalization, peripheral artery disease, and stroke. MBF value was calculated in each myocardial segment and ischemia was defined as mild decrease in MBF in two consecutive segments or moderate decrease in a single segment accompanied with a coronary stenosis ≥50%. The mean MBF of the non-ischemic segments was defined as remote MBF. We divided the patients into two groups by median MBF value of 1.15 ml/min/g. During a median follow-up of 18 months, 18 patients had adverse events. Annual event rate showed a significant difference between patients with low (≤1.15 ml/min/g) and high (>1.15 ml/min/g) MBF (6.1% vs 1.8%, p = 0.02). Univariate analysis showed that low MBF was a significant predictor of events (hazard ratio (HR): 3.4; 95% confidence interval (CI): 1.2 to 12.0; p = 0.02). This relationship maintained significant after adjusted for the presence of ischemia and cardiac risk factors (HR: 3.0; 95%CI: 1.1 to 11.1; p = 0.04). In conclusion, MBF value ≤1.15 ml/min/g derived from dynamic CTP in remote myocardium is significantly related with poor outcome and this relationship was independent of myocardial ischemia and cardiac risk factors.

Low-dose CT perfusion with combined use of CTP and CTP-derived coronary CT angiography at 70 kVp: validation with invasive fractional flow reserve

OBJECTIVES

To investigate the diagnostic performance of 70-kVp stress dynamic myocardial CT perfusion (CTP) as a low-dose, one-stop cardiac CT examination in clinical application.

MATERIALS AND METHODS

Consecutive symptomatic patients were prospectively recruited and scanned with stress dynamic myocardial CTP. The CTP phase with the best enhancement of the coronary arteries was selected and extracted as the CTP-derived single-phase coronary CT angiography (SP-CTA). The diagnostic performance of CTP and CTP+SP-CTA for functionally significant CAD was assessed. Invasive coronary angiography and fractional flow reserve were used as the reference standard for the myocardial ischemia evaluation.

RESULTS

In total, 71 patients (43 men and 28 women; 63.6 ± 8.8 years old) underwent the stress dynamic myocardial CTP; 63 vessels (36.2%) from 42 of the patients (59.2%) were identified as causing ischemia. On a per-vessel basis, the sensitivity, specificity, PPV, NPV, and diagnostic accuracy for CTP and CTP+SP-CTA were 77.8%, 93.7%, 87.5%, 88.1%, and 87.9% and 84.1%, 93.7%, 88.3%, 91.2%, and 90.2%, respectively. The area under the curve (AUC) of CTP+SP-CTA (AUC = 0.963; 95%CI, 0.938-0.989) was significantly superior to that of CTP (AUC = 0.922; 95%CI, 0.880-0.964) and that of SP-CTA (AUC = 0.833; 95%CI, 0.765-0.900) alone (all p < 0.01). The mean radiation dose of the CTP examination was 3.8 ± 1.4 mSv.

CONCLUSION

CTP-derived SP-CTA improved the diagnostic value of CTP. With a promising performance of myocardial ischemia detection and low radiation dose, the innovative low-dose, one-stop CTP examination is clinically feasible for patients who need to receive a myocardial perfusion assessment.

KEY POINTS

• Myocardial CTP performed well in the evaluation of hemodynamically significant CAD. • CTP-derived single-phase CCTA improved the diagnostic value of CTP. • The combined use of low-dose CTP and CTP-derived CCTA at 70 kVp is clinically feasible for CAD patients who need to receive a myocardial perfusion assessment.

Clinical application of four-dimensional noise reduction filtering with a similarity algorithm in dynamic myocardial computed tomography perfusion imaging

We aimed to evaluate the effects of four-dimensional noise reduction filtering using a similarity algorithm (4D-SF) on the image quality and hemodynamic parameter of dynamic myocardial computed tomography perfusion (CTP). Sixty-eight patients who underwent dynamic myocardial CTP for the assessment of coronary artery disease were enrolled. Dynamic CTP was performed using a 320-row CT with low tube voltage scan (80 kVp). Two different datasets of dynamic CTP were reconstructed using iterative reconstruction (IR) alone and a combination of IR and 4D-SF. Qualitative (5-grade scale) and quantitative image quality scores were assessed, and the CT-derived myocardial blood flow (CT-MBF) was quantified. These results were compared between the two different CTP images. The qualitative image quality in CTP images reconstructed with IR and 4D-SF was significantly higher than that with IR alone (noise score: 4.7 vs. 3.4, p < 0.05). The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) in CTP images reconstructed with IR and 4D-SF were significantly higher than those with IR alone (SNR: 20.6 vs. 9.7; CNR: 7.9 vs. 3.9, respectively; p < 0.05). There was no significant difference in mean CT-MBF between the two sets of CTP images (3.01 vs. 3.03 mL/g/min, p = 0.1081). 4D-SF showed incremental value in improving image quality in combination with IR without altering CT-MBF quantification in dynamic myocardial CTP imaging with a low tube potential.

Computed tomographic evaluation of myocardial ischemia

Myocardial ischemia is caused by a mismatch between myocardial oxygen consumption and oxygen delivery in coronary artery disease (CAD). Stratification and decision-making based on ischemia improves the prognosis in patients with CAD. Non-invasive tests used to evaluate myocardial ischemia include stress electrocardiography, echocardiography, single-photon emission computed tomography, and magnetic resonance imaging. Invasive fractional flow reserve is considered the reference standard for assessment of the hemodynamic significance of CAD. Computed tomography (CT) angiography has emerged as a first-line imaging modality for evaluation of CAD, particularly in the population at low to intermediate risk, because of its high negative predictive value; however, CT angiography does not provide information on the hemodynamic significance of stenosis, which lowers its specificity. Emerging techniques, e.g., CT perfusion and CT-fractional flow reserve, help to address this limitation of CT, by determining the hemodynamic significance of coronary artery stenosis. CT perfusion involves acquisition during the first pass of contrast medium through the myocardium following pharmacological stress. CT-fractional flow reserve uses computational fluid dynamics to model coronary flow, pressure, and resistance. In this article, we review these two functional CT techniques in the evaluation of myocardial ischemia, including their principles, technology, advantages, limitations, pitfalls, and the current evidence.

Combined assessment of subtended myocardial volume and myocardial blood flow for diagnosis of obstructive coronary artery disease using cardiac computed tomography: A feasibility study

BACKGROUND

This study aimed to evaluate the combined diagnostic performance of coronary artery stenosis-subtended myocardial volume (V_sub) and myocardial blood flow (MBFsub) on computed tomography (CT) for detecting obstructive coronary artery disease (CAD) assessed by invasive coronary angiography (ICA) and fractional flow reserve (FFR).

METHODS

Thirty-nine patients who underwent coronary CT angiography (CTA) and stress dynamic myocardial CT perfusion (CTP) prior to ICA were enrolled. Obstructive CAD was defined as severe (≥70%) or moderate (30-69%) stenosis with FFR ≤0.8 on ICA. The V_sub was semi-automatically calculated from coronary CTA data using Voronoi diagram-based myocardial segmentation. The standard CT-MBF based on the 17-segment model was calculated using dynamic stress CTP data and deconvolution analysis. The CT-MBFsub was automatically analyzed by integrating the CT-MBF and Voronoi diagram-based myocardial segmentation analyses. The diagnostic performance of combined CT-MBFsub and V_sub assessment was determined using receiver operating characteristic analysis and compared with standard CT-MBF and CT-MBFsub.

RESULTS

Of 117 vessels in 39 patients, 72 vessels were suspected of significant stenosis on CTA and 33 vessels had obstructive CAD on ICA and FFR. The sensitivity and specificity for identifying obstructive CAD were 67% and 82% for standard CT-MBF, 70% and 77% for CT-MBFsub, and 85% and 82% for combined CT-MBFsub and V_sub assessment. The area under the receiver operating characteristic curve of the combined CT-MBFsub and V_sub assessment was significantly higher than those of standard CT-MBF and CT-MBFsub (0.89 vs. 0.75, 0.77; p<0.05).

CONCLUSIONS

The V_sub may aid in increasing the diagnostic performance of CT-MBFsub for detecting obstructive CAD.

Diagnostic accuracy of stress myocardial computed tomography perfusion imaging to detect myocardial ischemia: a comparison with coronary flow velocity reserve derived from transthoracic Doppler echocardiography

BACKGROUND

Our aim was to evaluate the ability of adenosine triphosphate (ATP)-stress myocardial computed tomography perfusion (CTP) imaging to detect myocardial ischemia in the left anterior descending artery (LAD) territory, and to compare this method with coronary flow velocity reserve (CFVR) measured by transthoracic Doppler echocardiography (TTDE).

METHODS

ATP-stress CTP and CFVR were performed in 50 patients with stable angina pectoris. Myocardial ischemia assessed from CTP imaging was defined as qualitative visual perfusion defects and reduced myocardial blood flow (MBF) based on quantitative assessment. A cut-off value of CFVR of 2.0 was used.

RESULTS

The mean CFVR was 1.9 ± 0.6 in ischemic regions by CTP, whereas it was 2.9 ± 0.8 in non-ischemic regions (p < 0.001). CTP imaging could accurately predict CFVR <2.0 with 84.0% diagnostic accuracy (94.7% sensitivity, 77.4% specificity, 72.0% positive predictive value, and 96.0% negative predictive value). When receiver operating characteristic curve analysis of the MBF data was performed to detect CFVR <2.0, the area under the curve was 0.89, and the optimal MBF cut-off value was 1.43 mL/g/min.

CONCLUSIONS

This study suggests that qualitative and quantitative assessment of ATP-stress CTP exhibits a good correlation with CFVR for evaluation of myocardial ischemia.

Diagnostic Accuracy of Perfusional Computed Tomography in Moderate Coronary Stenosis: Comparison With Fractional Flow Reserve

Coronary computed tomography with myocardial perfusion imaging (CCTA-MPI) provides data on coronary anatomy and perfusion and may be useful in the assessment of ischemic coronary artery disease (CAD). Management of angiographically intermediate coronary lesions is challenging, and coronary fractional flow reserve (FFR) evaluation is recommended to assess whether these lesions are functionally significant. Our aim was to evaluate the diagnostic accuracy of CCTA-MPI in patients with stable CAD and at least 1 angiographically intermediate coronary lesion submitted to FFR. In this single-center prospective study, patients with stable CAD and at least 1 moderate coronary stenosis (50%-70% by visual estimation) were referred for CCTA-MPI (64-row multidetector) assessment before coronary FFR evaluation. Patients with severe coronary obstructions (≥70%) were excluded. The significance level adopted for all tests was 5%. Twenty-eight patients (mean age 60 ± SD years, 54% women) with 33 intermediate coronary obstructions were enrolled. Ten patients (30%) had functionally significant coronary obstructions characterized by FFR ≤0.8. The sensitivity, specificity, and accuracy of CCTA-MPI for the detection of functionally significant coronary obstructions were 30%, 100%, and 78.8%, respectively. CCTA-MPI positive predictive value was 100%, whereas negative predictive value was 76.7%. Correlation coefficient between tests was 0.48 (P = 0.005). On a novel approach to evaluate intermediate coronary lesions, accuracy of CCTA-MPI was 78.8%. The positive predictive value of an abnormal CCTA-MPI on this population was 100%, suggesting that CCTA-MPI may have a role in the assessment of patients with anatomically identified intermediate coronary lesions.

Evaluation of Myocardial Ischemia Using Coronary Computed Tomography Angiography in Patients with Stable Angina

안정형 협심증 환자에서 관상동맥질환의 치료 여부를 결정하고 임상 결과를 예측하기 위해서는 심근허혈의 평가가 중요하다. 현재 심근허혈 진단의 표준검사법으로 분획혈류예비력 검사법이 인정되나 침습적 검사라는 제한점이 있다. 또한, 관상동맥 전산화단층촬영은 형태적인 관상동맥질환 진단에 유용한 방법으로 정립되었지만, 혈역학적으로 유의한 협착에 의한 심근허혈 진단에는 한계가 있다. 최근 이러한 문제를 해결하고자 관상동맥 전산화단층촬영 영상을 기반으로 측정한 관상동맥 죽상경화판의 정량화, 심근관류, 그리고 심근 분획혈류예비력을 이용한 연구들이 진행되어 왔고, 그 진단적 가치를 점차 인정받고 있다. 본 종설에서는 심근허혈진단과 관련된 관상동맥 전산화단층촬영 혈관조영술의 여러 영상기법들에 대해서 알아보고자 한다.

Coronary artery stenosis-related perfusion ratio using dynamic computed tomography myocardial perfusion imaging: a pilot for identification of hemodynamically significant coronary artery disease

The purpose of this study was to evaluate the feasibility of the stenosis-related quantitative perfusion ratio (QPR) for detecting hemodynamically significant coronary artery disease (CAD). Twenty-seven patients were retrospectively enrolled. All patients underwent dynamic myocardial computed tomography perfusion (CTP) and coronary computed tomography angiography (CTA) before invasive coronary angiography (ICA) measuring the fractional flow reserve (FFR). Coronary lesions with FFR ≤ 0.8 were defined as hemodynamically significant CAD. The myocardial blood flow (MBF) was calculated using dynamic CTP data, and CT-QPR was calculated as the CT-MBF relative to the reference CT-MBF. The stenosis-related CT-MBF and QPR were calculated using Voronoi diagram-based myocardial segmentation from coronary CTA data. The relationships between FFR and stenosis-related CT-MBF or QPR and the diagnostic performance of the stenosis-related CT-MBF and QPR were evaluated. Of 81 vessels, FFR was measured in 39 vessels, and 20 vessels (51%) in 15 patients were diagnosed as hemodynamically significant CAD. The stenosis-related CT-QPR showed better correlation (r = 0.70, p < 0.05) than CT-MBF (r = 0.56, p < 0.05). Sensitivity and specificity for detecting hemodynamically significant CAD were 95% and 58% for CT-MBF, and 95% and 90% for CT-QPR, respectively. The area under the receiver operating characteristic curve for the CT-QPR was significantly higher than that for the CT-MBF (0.94 vs. 0.79; p < 0.05). The stenosis-related CT-QPR derived from dynamic myocardial CTP and coronary CTA showed a better correlation with FFR and a higher diagnostic performance for detecting hemodynamically significant CAD than the stenosis-related CT-MBF.

Myocardial Perfusion by Coronary Computed Tomography in the Evaluation of Myocardial Ischemia: Simultaneous Stress Protocol with SPECT

BACKGROUND

Functional assessment to rule out myocardial ischemia using coronary computed tomography angiography (CCTA) is extremely important and data on the Brazilian population are still limited.

OBJECTIVE

To assess the diagnostic performance of myocardial perfusion by CCTA in the detection of severe obstructive coronary artery disease (CAD) compared with single-photon emission computerized tomography (SPECT). To analyze the importance of anatomical knowledge to understand the presence of myocardial perfusion defects on SPECT imaging that is not identified on computed tomography (CT) scan.

METHOD

A total of 35 patients were evaluated by a simultaneous pharmacologic stress protocol. Fisher's exact test was used to compare proportions. The patients were grouped according to the presence or absence of significant CAD. The area under the ROC curve was used to identify the diagnostic performance of CCTA and SPECT in perfusion assessment. P < 0.05 values were considered statistically significant.

RESULTS

For detection of obstructive CAD, CT myocardial perfusion analysis yielded an area under the ROC curve of 0.84 [a 95% confidence interval (CI95%): 0.67-0.94, p < 0.001]. SPECT myocardial perfusion imaging, on the other hand, showed an AUC of 0.58 (95% CI 0.40 - 0.74, p < 0.001). In this study, false-positive results with SPECT are described.

CONCLUSION

Myocardial perfusion analysis by CTA displays satisfactory results compared to SPECT in the detection of obstructive CAD. CCTA can rule out false-positive results of SPECT.

Dynamic CT myocardial perfusion imaging

Cardiac CT offers several approaches to establish the hemodynamic severity of coronary artery obstructions. Dynamic myocardial perfusion CT (MPI_CT) is based on serial CT imaging to measure the inflow of contrast medium into the myocardium and calculate absolute measures of myocardial perfusion. This review describes the MPI_CT acquisition protocol, post-image acquisition processing and calculation of quantitative parameters, the diagnostic performance of MPI_CT and the potential incremental value of this technique in comparison to alternative approaches. Further technical innovation using different scanner platforms and establishment of reproducible diagnostic thresholds to differentiate significant coronary artery disease will be crucial in the path to broader clinical implementation.

Impact of Knowledge-Based Iterative Model Reconstruction on Image Quality and Hemodynamic Parameters in Dynamic Myocardial Computed Tomography Perfusion Using Low-Tube-Voltage Scan: A Feasibility Study

OBJECTIVE

Knowledge-based iterative model reconstruction (IMR) yields diagnostically acceptable image quality in low-dose static computed tomography (CT). We aimed to evaluate the feasibility of IMR in dynamic myocardial computed tomography perfusion (CTP).

METHODS

We enrolled 24 patients who underwent stress dynamic CTP using a 256-slice CT. Images were reconstructed using filtered back projection (FBP), hybrid IR, and IMR. Image quality and hemodynamic parameters were compared among three algorithms.

RESULTS

Qualitative image quality and contrast-to-noise ratio were significantly higher by IMR than by FBP or hybrid IR (visual score: 4.1 vs. 3.0 and 3.5; contrast-to-noise ratio: 12.4 vs. 6.6 and 8.4; P < 0.05). No significant difference was observed among algorithms in CTP-derived myocardial blood flow (1.68 vs. 1.73 and 1.70 mL/g/min).

CONCLUSIONS

The use of knowledge-based iterative model reconstruction improves image quality without altering hemodynamic parameters in low-dose dynamic CTP, compared with FBP or hybrid IR.

FFRCT and CT perfusion: A review on the evaluation of functional impact of coronary artery stenosis by cardiac CT

Coronary computed tomography angiography (CCTA) is at the frontline of the diagnostic strategies to detect coronary artery disease (CAD). Anatomical information have proven to be insufficient to detect hemodynamic significant epicardial stenosis. In the present invited review we discuss on FFR_CT and stress CTP, emerging technologies for an accurate and comprehensive evaluation of patients with suspected CAD, offering both anatomical (i.e. luminal and plaque) and functional assessment in one single technique.

Accuracy of Myocardial Blood Flow Estimation From Dynamic Contrast-Enhanced Cardiac CT Compared With PET

Background The accuracy of absolute myocardial blood flow (MBF) from dynamic contrast-enhanced cardiac computed tomography acquisitions has not been fully characterized. We evaluate computed tomography (CT) compared with rubidium-82 positron emission tomography (PET) MBF estimates in a high-risk population. Methods In a prospective trial, patients receiving clinically indicated rubidium-82 PET exams were recruited to receive a dynamic contrast-enhanced cardiac computed tomography exam. The CT protocol included a rest and stress dynamic portion each acquiring 12 to 18 cardiac-gated frames. The global MBF was estimated from the PET and CT exam. Results Thirty-four patients referred for cardiac rest-stress PET were recruited. Of the 68 dynamic contrast-enhanced cardiac computed tomography scans, 5 were excluded because of injection errors or mismatched hemodynamics. The CT-derived global MBF was highly correlated with the PET MBF (r=0.92; P<0.001) with a mean difference of 0.7±26.4%. The CT MBF estimates were within 20% of PET estimates ( P<0.02) with a mean of (1) MBF for resting flow of PET versus CT of 0.9±0.3 versus 1.0±0.2 mL/min per gram and (2) MBF for stress flow of 2.1±0.7 versus 2.0±0.8 mL/min per gram. Myocardial flow reserve was -14±28% underestimated with CT (PET versus CT myocardial flow reserve, 2.5±0.6 versus 2.2±0.6). The proposed rest+stress+computed tomography angiography protocol had a dose length product of 598±76 mGy×cm resulting in an approximate effective dose of 8.4±1.1 mSv. Conclusions In a high-risk clinical population, a clinically practical dynamic contrast-enhanced cardiac computed tomography provided unbiased MBF estimates within 20% of rubidium-82 PET. Although unbiased, the CT estimates contain substantial variance with an standard error of the estimate of 0.44 mL/min per gram. Myocardial flow reserve estimation was not as accurate as individual MBF estimates.

Hybrid anatomo-functional imaging of coronary artery disease: Beneficial irrespective of its core components

Coronary artery disease (CAD) is the most common and important cause of ischemic heart disease, with major implications on global morbidity and mortality. Non-invasive testing is crucial in the diagnostic and prognostic work-up of patients with or at risk of CAD, and also to guide decision making in terms of pharmacologic and revascularization therapy. The traditional paradigm is to view anatomic (i.e., coronary computed tomography) and functional imaging (e.g., myocardial perfusion scintigraphy) tests as opposing alternatives. Such approach is too reductionist and does not capitalize on the strengths of each type of test while risking to overlook the inherent limitations. The combination of anatomic and functional tests in a logic of hybrid imaging holds the promise of overcoming the limitations inherent to anatomic and functional testing, enabling more accurate diagnosis, prognosis, and guidance for revascularization in patients with CAD.

Dynamic Stress Computed Tomography Perfusion With a Whole-Heart Coverage Scanner in Addition to Coronary Computed Tomography Angiography and Fractional Flow Reserve Computed Tomography Derived

OBJECTIVES

The aims of the study were to test the diagnostic accuracy of integrated evaluation of dynamic myocardial computed tomography perfusion (CTP) on top of coronary computed tomography angiography (cCTA) plus fractional flow reserve computed tomography derived (FFR_CT) by using a whole-heart coverage computed tomography (CT) scanner as compared with clinically indicated invasive coronary angiography (ICA) and invasive fractional flow reserve (FFR).

BACKGROUND

Recently, new techniques such as dynamic stress computed tomography perfusion (stress-CTP) emerged as potential strategies to combine anatomical and functional evaluation in a one-shot scan. However, previous experiences with this technique were associated with high radiation exposure.

METHODS

Eighty-five consecutive symptomatic patients scheduled for ICA were prospectively enrolled. All patients underwent rest cCTA followed by stress dynamic CTP with a whole-heart coverage CT scanner (Revolution CT, GE Healthcare, Milwaukee, Wisconsin). FFR_CT was also measured by using the rest cCTA dataset. The diagnostic accuracy to detect functionally significant coronary artery disease (CAD) in a vessel-based model of cCTA alone, cCTA+FFR_CT, cCTA+CTP, or cCTA+FFR_CT+CTP were assessed and compared by using ICA and invasive FFR as reference. The overall effective dose of dynamic CTP was also measured.

RESULTS

The prevalence of obstructive CAD and functionally significant CAD was 77% and 57%, respectively. The sensitivity and specificity of cCTA alone, cCTA+FFR_CT, and cCTA+CTP were 83% and 66%, 86% and 75%, and 73% and 86%, respectively. Both the addition of FFR_CT and CTP improves the area under the curve (AUC: 0.876 and 0.878, respectively) as compared with cCTA alone (0.826; p < 0.05). The sequential strategy of cCTA+FFR_CT+CTP showed the highest AUC (0.919; p < 0.05) as compared with all other strategies. The mean effective radiation dose (ED) for cCTA and stress CTP was 2.8 ± 1.2 mSv and 5.3 ± 0.7 mSv, respectively.

CONCLUSIONS

The addition of dynamic stress CTP on top of cCTA and FFR_CT provides additional diagnostic accuracy with acceptable radiation exposure.