Combined assessment of coronary anatomy and myocardial perfusion using multidetector computed tomography for the evaluation of 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.

Static CT myocardial perfusion imaging: image quality, artifacts including distribution and diagnostic performance compared to 82Rb PET

Background

Rubidium-82 positron emission tomography (⁸²Rb PET) MPI is considered a noninvasive reference standard for the assessment of myocardial perfusion in coronary artery disease (CAD) patients. Our main goal was to compare the diagnostic performance of static rest/ vasodilator stress CT myocardial perfusion imaging (CT-MPI) to stress/ rest ⁸²Rb PET-MPI for the identification of myocardial ischemia.

Methods

Forty-four patients with suspected or diagnosed CAD underwent both static CT-MPI and ⁸²Rb PET-MPI at rest and during pharmacological stress. The extent and severity of perfusion defects on PET-MPI were assessed to obtain summed stress score, summed rest score, and summed difference score. The extent and severity of perfusion defects on CT-MPI was visually assessed using the same grading scale. CT-MPI was compared with PET-MPI as the gold standard on a per-territory and a per-patient basis.

Results

On a per-patient basis, there was moderate agreement between CT-MPI and PET-MPI with a weighted 0.49 for detection of stress induced perfusion abnormalities. Using PET-MPI as a reference, static CT-MPI had 89% sensitivity (SS), 58% specificity (SP), 71% accuracy (AC), 88% negative predictive value (NPV), and 59% positive predictive value (PPV) to diagnose stress-rest perfusion deficits on a per-patient basis. On a per-territory analysis, CT-MPI had 73% SS, 65% SP, 67% AC, 90.8% NPV, and 34% PPV to diagnose perfusion deficits.

Conclusions

CT-MPI has high sensitivity and good overall accuracy for the diagnosis of functionally significant CAD using ⁸²Rb PET-MPI as the reference standard. CT-MPI may play an important role in assessing the functional significance of CAD especially in combination with CCTA.

Narrative review of cardiac computed tomography perfusion: insights into static rest perfusion

Cardiac or left ventricular perfusion performed with cardiac computed tomography (CCT) is a developing method that may have the potential to complete in a very straight forward way the assessment of ischemic heart disease by means of CT. Myocardial CT perfusion (CTP) can be achieved with a single static scan during the first-pass of the iodinate contrast agent, with the monoenergetic or dual-energy acquisition, or as a dynamic, time-resolved scan during stress by using coronary vasodilator agents. Several methods can be performed, and we focused on static perfusion. CTP may serve as a useful adjunct to coronary CT angiography (CTA) to improve specificity of detecting myocardial ischemia. Technological advances will reduce the radiation dose of myocardial CTP, such as low tube voltage imaging or new reconstruction algorithms, making it a more viable clinical option. The advantages of static first-pass non-stress perfusion are several; the main one is that it can be done to each and every patient who undergoes CCT for the assessment of coronary artery tree. Future advances in CTP will likely improve the diagnostic accuracy of CTP + CTA, and will better estimate the severity of ischemia Therefore, it is simple and comprehensive. However, it has several limitations. In this review we will discuss the technique with its advantages and limitations.

Normal patterns of left ventricle rest myocardial perfusion assessed by third-generation cardiac computed tomography

PURPOSE

To investigate diastolic and systolic patterns of segmental and transmural rest perfusion of the left ventricle (LV) in normal subjects (NS) undergoing third-generation dual-source cardiac computed tomography (CCT).

METHODS

Forty consecutive NS, with normal coronary arteries and cardiac chambers both anatomically and functionally on the basis of CCT, were retrospectively enrolled in the study. Relative normalized myocardial attenuation density (rnMAD) and transmural perfusion ratio (TPR) were calculated in diastole and systole for each segment and layer of the LV and then pooled into territories.

RESULTS

Statistical analysis showed that sub-endocardial rnMAD was significantly higher than intra-myocardial and sub-epicardial for all myocardial territories both in systolic and diastolic phases (P<0·001). Basal and mid-ventricular rnMAD were higher than apical for all myocardial layers (P<0·001). Septum displayed higher rnMAD in intra-myocardium and sub-epicardium (179 ± 61 and 170 ± 59 in diastole and 172 ± 60 and 166 ± 58 in systole, respectively) than the anterior, lateral and inferior wall (P<0·001). Diastolic and systolic TPR were significantly different for the anterior and lateral wall (P<0·001), while septal TPR (1·06 ± 0·06 in diastole and 1·05 ± 0·06 in systole, respectively) was the lowest as compared to other territories' TPR. Finally, basal, mid-ventricular and apical TPR showed a significant linear trend with basal lower than mid-ventricular and apical values.

CONCLUSION

Inter-territory and inter-layer myocardial perfusion differences can be accurately assessed with CCT in NS. This assessment is the basic step to further evaluate abnormal rest perfusion patterns in ischaemic and non-ischaemic diseases.

Myocardial Assessment with Cardiac CT: Ischemic Heart Disease and Beyond

PURPOSE OF REVIEW

The aim of this review is to highlight recent advancements, current trends, and the expanding role for cardiac CT (CCT) in the evaluation of ischemic heart disease, nonischemic cardiomyopathies, and some specific congenital myocardial disease states.

RECENT FINDINGS

CCT is a highly versatile imaging modality for the assessment of numerous cardiovascular disease states. Coronary CT angiography (CCTA) is now a well-established first-line imaging modality for the exclusion of significant coronary artery disease (CAD); however, CCTA has modest positive predictive value and specificity for diagnosing obstructive CAD in addition to limited capability to evaluate myocardial tissue characteristics.

SUMMARY

CTP, when combined with CCTA, presents the potential for full functional and anatomic assessment with a single modality. CCT is a useful adjunct in select patients to both TTE and CMR in the evaluation of ventricular volumes and systolic function. Newer applications, such as dynamic CTP and DECT, are promising diagnostic tools offering the possibility of more quantitative assessment of ischemia. The superior spatial resolution and volumetric acquisition of CCT has an important role in the diagnosis of other nonischemic causes of cardiomyopathies.

Imaging the myocardial ischemic cascade

Non-invasive imaging plays a growing role in the diagnosis and management of ischemic heart disease from its earliest manifestations of endothelial dysfunction to myocardial infarction along the myocardial ischemic cascade. Experts representing the North American Society for Cardiovascular Imaging and the European Society of Cardiac Radiology have worked together to organize the role of non-invasive imaging along the framework of the ischemic cascade. The current status of non-invasive imaging for ischemic heart disease is reviewed along with the role of imaging for guiding surgical planning. The issue of cost effectiveness is also considered. Preclinical disease is primarily assessed through the coronary artery calcium score and used for risk assessment. Once the patient becomes symptomatic, other imaging tests including echocardiography, CCTA, SPECT, PET and CMR may be useful. CCTA appears to be a cost-effective gatekeeper. Post infarction CMR and PET are the preferred modalities. Imaging is increasingly used for surgical planning of patients who may require coronary artery bypass.

Myocardial ischemia testing with computed tomography: emerging strategies

Although cardiac computed tomography (CT) has high negative predictive value to exclude obstructive coronary artery disease (CAD), particularly in the low to intermediate risk population, it has low specificity in the diagnosis of ischemia-inducing lesions. This inability to predict hemodynamically significant stenosis hampers the ability of CT to be an effective gatekeeper for invasive angiography and to guide appropriate revascularization. Recent advances in CT technology have resulted in the development of multiple techniques to provide hemodynamic information and detect lesion-specific ischemia, namely CT perfusion (CTP), CT-derived fractional flow reserve (CT-FFR) and coronary transluminal attenuation gradient (TAG). In this article, we provide a perspective on these emerging CT techniques in the evaluation of myocardial ischemia.

Myocardial computed tomography perfusion

Despite having excellent diagnostic accuracy to detect anatomical coronary stenosis, coronary CT angiography (CTA) has a limited specificity to detect myocardial ischemia. CT perfusion (CTP) can identify myocardial perfusion defects during vasodilator stress, and when added to coronary CTA, improves the specificity of detecting hemodynamically significant stenosis. A CTP protocol typically involves the acquisition of two separate data sets: (I) a rest scan that can be used as both a coronary CTA and for evaluating rest myocardial perfusion, and (II) a stress CTP scan acquired during vasodilator stress testing. This review summarizes some the techniques, strengths, and limitations of CTP, and provides an overview of the recent evidence supporting the potential use of CTP in clinical practice.

Infarct characterization using CT

Myocardial infarction (MI) is a major cause of death and disability worldwide. The incidence is not expected to diminish, despite better prevention, diagnosis and treatment, because of the ageing population in industrialized countries and unhealthy lifestyles in developing countries. Nowadays it is highly requested an imaging tool able to evaluate MI and viability. Technology improvements determined an expansion of clinical indications from coronary plaque evaluation to functional applications (perfusion, ischemia and viability after MI) integrating additional phases and information in the mainstream examination. Cardiac computed tomography (CCT) and cardiac MR (CMR) employ different contrast media, but may characterize MI with overlapping imaging findings due to the similar kinetics and tissue distribution of gadolinium and iodinated contrast media. CCT may detect first-pass perfusion defects, dynamic perfusion after pharmacological stress, and delayed enhancement (DE) of non-viable territories.

Update on Computed Tomography Myocardial Perfusion Imaging

PURPOSE OF REVIEW

Computed tomography (CT) coronary angiography is a well-validated non-invasive technique for accurate and expedient diagnosis of coronary artery disease (CAD). However, a limitation of coronary CT angiography (CCTA) is its limited capability to identify physiologically significant stenoses, which may eventuate the need for further functional testing. Stress CT myocardial perfusion imaging (CT-MPI) is an emerging technique that has the ability to identify flow-limiting stenoses.

RECENT FINDINGS

The combination of CCTA coronary and CT-MPI has transformed the modality from a tool to assess anatomy and morphology to a modality capable of simultaneous assessment of coronary stenoses and their physiologic significance. A growing number of studies have demonstrated the feasibility and diagnostic accuracy of CT-MPI in comparison to a number of reference standard modalities for CAD diagnosis, including single-photon emission CT, cardiovascular magnetic resonance imaging, and invasive coronary angiography with and without fractional flow-reserve testing.

SUMMARY

While there is still a need for consensus regarding acquisition techniques as well as analysis and interpretation of CT-MPI, with further validation, it is likely to become a powerful adjunctive tool to CCTA in the management of patients with suspected coronary disease.

Cardiovascular Imaging: The Past and the Future, Perspectives in Computed Tomography and Magnetic Resonance Imaging

Today's noninvasive imaging of the cardiovascular system has revolutionized the approach to various diseases and has substantially affected prognostic information. Cardiovascular magnetic resonance (MR) and computed tomographic (CT) imaging are at center stage of these approaches, although 5 decades ago, these technologies were unheard of. Both modalities had their inception in the 1970s with a primary focus on noncardiovascular applications. The technical development of the various decades, however, substantially pushed the envelope for cardiovascular MR and CT applications. Within the past 10-15 years, MR and CT technologies have pushed each other in cardiac applications; and without the "rival" modality, neither one would likely not have reached its potential today. This view on the history of MR and CT in the field of cardiovascular applications provides insight into the story of success of applications that once have been ideas only but are at prime time today.

Three-dimensional quantification of myocardial perfusion during regadenoson stress computed tomography

BACKGROUND

There is no accepted methodology for CT-based vasodilator stress myocardial perfusion imaging and analysis. We developed a technique for quantitative 3D analysis of CT images, which provides several indices of myocardial perfusion. We sought to determine the ability of these indices during vasodilator stress to identify segments supplied by coronary arteries with obstructive disease and to test the accuracy of the detection of perfusion abnormalities against SPECT.

METHODS

We studied 93 patients referred for CT coronary angiography (CTCA) who underwent regadenoson stress. 3D analysis of stress CT images yielded segmental perfusion indices: mean X-ray attenuation, severity of defect and relative defect volume. Each index was averaged for myocardial segments, grouped by severity of stenosis: 0%, <50%, 50-70%, and >70%. Objective detection of perfusion abnormalities was optimized in 47 patients and then independently tested in the remaining 46 patients.

RESULTS

CTCA depicted normal coronary arteries or non-obstructive disease in 62 patients and stenosis of >50% in 31. With increasing stenosis, segmental attenuation showed a 7% decrease, defect severity increased 11%, but relative defect volume was 7-fold higher in segments with obstructive disease (p<0.001). In the test group, detection of perfusion abnormalities associated with stenosis >50% showed sensitivity 0.78, specificity 0.54, accuracy 0.59. When compared to SPECT in a subset of 21 patients (14 with abnormal SPECT), stress CT perfusion analysis showed sensitivity 0.79, specificity 0.71, accuracy 0.76.

CONCLUSIONS

3D analysis of vasodilator stress CT images provides quantitative indices of myocardial perfusion, of which relative defect volume was most robust in identifying segments supplied by arteries with obstructive disease. This study may have implications on how CT stress perfusion imaging is performed and analyzed.

Technical prerequisites and imaging protocols for dynamic and dual energy myocardial perfusion imaging

Coronary CT angiography (CCTA) is an established imaging technique used for the non-invasive morphological assessment of coronary artery disease. As in invasive coronary angiography, CCTA anatomical assessment of coronary stenosis does not adequately predict hemodynamic relevance. However, recent technical improvements provide the possibility of CT myocardial perfusion imaging (CTMPI). Two distinct CT techniques are currently available for myocardial perfusion assessment: static CT myocardial perfusion imaging (sCTMPI), with single- or dual-energy modality, and dynamic CT myocardial perfusion imaging (dCTMPI). The combination of CCTA morphological assessment and CTMPI functional evaluation holds promise for achieving a comprehensive assessment of coronary artery anatomy and myocardial perfusion using a single image modality.

Beyond stenosis detection: computed tomography approaches for determining the functional relevance of coronary artery disease

Coronary computed tomography angiography (CCTA) is an established imaging technique for the noninvasive assessment of coronary arteries. However, CCTA remains a morphologic technique with the same limitations as invasive coronary angiography in evaluating the hemodynamic significance of coronary stenosis. Different computed tomography (CT) techniques for the functional analysis of coronary lesions have recently emerged, including static and dynamic CT myocardial perfusion imaging and CT-based fractional flow reserve and transluminal attenuation gradient methods. These techniques hold promise for achieving a comprehensive appraisal of anatomic and functional aspects of coronary heart disease with a single modality.

Cardiac CT for myocardial ischaemia detection and characterization--comparative analysis

The assessment of patients presenting with symptoms of myocardial ischaemia remains one of the most common and challenging clinical scenarios faced by physicians. Current imaging modalities are capable of three-dimensional, functional and anatomical views of the heart and as such offer a unique contribution to understanding and managing the pathology involved. Evidence has accumulated that visual anatomical coronary evaluation does not adequately predict haemodynamic relevance and should be complemented by physiological evaluation, highlighting the importance of functional assessment. Technical advances in CT technology over the past decade have progressively moved cardiac CT imaging into the clinical workflow. In addition to anatomical evaluation, cardiac CT is capable of providing myocardial perfusion parameters. A variety of CT techniques can be used to assess the myocardial perfusion. The single energy first-pass CT and dual energy first-pass CT allow static assessment of myocardial blood pool. Dynamic cardiac CT imaging allows quantification of myocardial perfusion through time-resolved attenuation data. CT-based myocardial perfusion imaging (MPI) is showing promising diagnostic accuracy compared with the current reference modalities. The aim of this review is to present currently available myocardial perfusion techniques with a focus on CT imaging in light of recent clinical investigations. This article provides a comprehensive overview of currently available CT approaches of static and dynamic MPI and presents the results of corresponding clinical trials.

Diagnostic value of Flash dual-source CT coronary artery imaging combined with dual-energy myocardial perfusion imaging for coronary heart disease

The present study aimed to investigate the diagnostic value of Flash dual-source CT coronary angiography (DS-CTA) combined with dual-energy myocardial perfusion imaging (DS-CTP) for coronary heart disease (CHD), as a single-stage examination. A total of 60 patients with CHD underwent DS-CT examination, as well as coronary angiography (CAG), as the reference standard. The patients were divided into <50% and ≥50% stenosis groups based on their coronary angiograms. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of the method for diagnosing stenosis of ≥50% were evaluated via DS-CTA combined with DS-CTP. Of the 60 patients, 59 showed satisfactory results that conformed to the diagnostic requirements. Using CAG as the reference standard, the sensitivity, specificity and positive and negative predictive values of the Flash DS-CT results in the ≥50% vascular stenosis group were 83.7, 92.7, 88.9 and 89.1%, respectively. The respective values for DS-CTA combined with DS-CTP for diagnosing CHD were 94.2, 91.1, 88.0 and 95.8%. Therefore, the results obtained indicate that DS-CTA combined with DS-CTP has a high diagnostic value for CHD. DS-CT is advantageous for diagnosing and prognosticating CHD.

Myocardial perfusion imaging with cardiac computed tomography: state of the art

Cardiac computed tomography (CCT) has become an important tool for the anatomic assessment of patients with suspected coronary disease. Its diagnostic accuracy for detecting the presence of underlying coronary artery disease and ability to risk stratify patients are well documented. However, the role of CCT for the physiologic assessment of myocardial perfusion during resting and stress conditions is only now emerging. With the addition of myocardial perfusion imaging to coronary imaging, CCT has the potential to assess both coronary anatomy and its functional significance with a single non-invasive test. In this review, we discuss the current state of CCT myocardial perfusion imaging for the detection of myocardial ischemia and myocardial infarction and examine its complementary role to CCT coronary imaging.

Quantitative three-dimensional evaluation of myocardial perfusion during regadenoson stress using multidetector computed tomography

OBJECTIVE

The ability of multidetector computed tomography (MDCT) to detect stress-induced myocardial perfusion abnormalities is of great clinical interest as a potential tool for the combined evaluation of coronary stenosis and its hemodynamic significance. We tested the hypothesis that quantitative 3-dimensional (3D) analysis of myocardial perfusion from MDCT images obtained during regadenoson stress would more accurately detect the presence of significant coronary artery disease (CAD) than identical analysis when performed on resting MDCT images.

METHODS

We prospectively studied 50 consecutive patients referred for CT coronary angiography (CTCA) who agreed to undergo additional imaging with regadenoson (0.4 mg; Astellas). Images were acquired using prospective gating (256-channel; Philips). Custom analysis software was used to define 3D myocardial segments, and calculate for each segment an index of severity and extent of perfusion abnormality, Qh, which was compared with perfusion defects predicted by the presence and severity of coronary stenosis on CTCA.

RESULTS

Three patients were excluded because of image artifacts. In the remaining 47 patients, CTCA depicted stenosis more than 50% in 23 patients in 37 of 141 coronary arteries. In segments supplied by the obstructed arteries, myocardial attenuation was slightly reduced compared with normally perfused segments at rest (mean [SD], 91 [21] vs 93 [26] Hounsfield units, not significant) and, to a larger extent, at peak stress (102 [21] vs 112 [20] Hounsfield units, P < 0.05). In contrast, index Qh was significantly increased at rest (0.40 [0.48] vs 0.26 [0.41], P < 0.05) and reached a nearly 3-fold difference at peak stress (0.66 [0.74] vs 0.28 [0.51], P < 0.05). The addition of regadenoson improved the diagnosis of CAD, as reflected by an increase in sensitivity (from 0.57 to 0.91) and improvement in accuracy (from 0.65 to 0.77).

CONCLUSIONS

Quantitative 3D analysis of MDCT images allows objective detection of CAD, the accuracy of which is improved by regadenoson stress.

Noise spatial nonuniformity and the impact of statistical image reconstruction in CT myocardial perfusion imaging

PURPOSE

To achieve high temporal resolution in CT myocardial perfusion imaging (MPI), images are often reconstructed using filtered backprojection (FBP) algorithms from data acquired within a short-scan angular range. However, the variation in the central angle from one time frame to the next in gated short scans has been shown to create detrimental partial scan artifacts when performing quantitative MPI measurements. This study has two main purposes. (1) To demonstrate the existence of a distinct detrimental effect in short-scan FBP, i.e., the introduction of a nonuniform spatial image noise distribution; this nonuniformity can lead to unexpectedly high image noise and streaking artifacts, which may affect CT MPI quantification. (2) To demonstrate that statistical image reconstruction (SIR) algorithms can be a potential solution to address the nonuniform spatial noise distribution problem and can also lead to radiation dose reduction in the context of CT MPI.

METHODS

Projection datasets from a numerically simulated perfusion phantom and an in vivo animal myocardial perfusion CT scan were used in this study. In the numerical phantom, multiple realizations of Poisson noise were added to projection data at each time frame to investigate the spatial distribution of noise. Images from all datasets were reconstructed using both FBP and SIR reconstruction algorithms. To quantify the spatial distribution of noise, the mean and standard deviation were measured in several regions of interest (ROIs) and analyzed across time frames. In the in vivo study, two low-dose scans at tube currents of 25 and 50 mA were reconstructed using FBP and SIR. Quantitative perfusion metrics, namely, the normalized upslope (NUS), myocardial blood volume (MBV), and first moment transit time (FMT), were measured for two ROIs and compared to reference values obtained from a high-dose scan performed at 500 mA.

RESULTS

Images reconstructed using FBP showed a highly nonuniform spatial distribution of noise. This spatial nonuniformity led to large fluctuations in the temporal direction. In the numerical phantom study, the level of noise was shown to vary by as much as 87% within a given image, and as much as 110% between different time frames for a ROI far from isocenter. The spatially nonuniform noise pattern was shown to correlate with the source trajectory and the object structure. In contrast, images reconstructed using SIR showed a highly uniform spatial distribution of noise, leading to smaller unexpected noise fluctuations in the temporal direction when a short scan angular range was used. In the numerical phantom study, the noise varied by less than 37% within a given image, and by less than 20% between different time frames. Also, the noise standard deviation in SIR images was on average half of that of FBP images. In the in vivo studies, the deviation observed between quantitative perfusion metrics measured from low-dose scans and high-dose scans was mitigated when SIR was used instead of FBP to reconstruct images.

CONCLUSIONS

(1) Images reconstructed using FBP suffered from nonuniform spatial noise levels. This nonuniformity is another manifestation of the detrimental effects caused by short-scan reconstruction in CT MPI. (2) Images reconstructed using SIR had a much lower and more uniform noise level and thus can be used as a potential solution to address the FBP nonuniformity. (3) Given the improvement in the accuracy of the perfusion metrics when using SIR, it may be desirable to use a statistical reconstruction framework to perform low-dose dynamic CT MPI.

CT of coronary heart disease: Part 1, CT of myocardial infarction, ischemia, and viability

OBJECTIVE

This article reviews the CT-based approaches aimed at the assessment of myocardial infarction, ischemia, and viability described in the recent literature.

CONCLUSION

Rapid advances in CT technology not only have improved visualization of coronary arteries but also increasingly enable noncoronary myocardial applications, including analysis of wall motion and the state of the myocardial blood supply. These advancements hold promise for eventually accomplishing the goal of comprehensively evaluating coronary heart disease with a single noninvasive modality.

Myocardial hypo-enhancement on resting computed tomography angiography images accurately identifies myocardial hypoperfusion

OBJECTIVE

The objective of this study was to test the diagnostic accuracy of myocardial CT perfusion (CTP) imaging using color and gray-scale image analysis.

BACKGROUND

Current myocardial CTP techniques have varying diagnostic accuracy and are prone to artifacts that impair detection. This study evaluated the diagnostic accuracy of color and/or gray-scale CTP and the application of artifact criteria to detect hypoperfusion.

METHODS

Fifty-nine prospectively enrolled patients with abnormal single-photon emission computed tomography (SPECT) studies were analyzed. True hypoperfusion was defined if SPECT hypoperfusion corresponded to obstructive coronary stenoses on CT angiography (CTA). CTP applied color and gray-scale myocardial perfusion maps to resting CTA images. Criteria for identifying artifacts were also applied during interpretation.

RESULTS

Using combined SPECT plus CTA as the diagnostic standard, abnormal myocardial CTP was present in 33 (56%) patients, 19 suggesting infarction and 14 suggesting ischemia. Patient-level color and gray-scale myocardial CTP sensitivity to detect infarction was 90%, with specificity 80%, and negative and positive predictive value of 94% and 68%. To detect ischemia or infarction, CTP specificity and positive predictive value were 92% whereas sensitivity was 70%. Gray-scale myocardial CTP had slightly lower specificity but similar sensitivity. Myocardial CTP artifacts were present in 88% of studies and were identified using our criteria.

CONCLUSIONS

Color and gray-scale myocardial CTP using resting CTA images identified myocardial infarction with high sensitivity as well as infarction or ischemia with high specificity and positive predictive value without additional testing or radiation. Color and gray-scale CTP had slightly better specificity than gray-scale alone.

Incremental value of myocardial perfusion over regional left ventricular function and coronary stenosis by cardiac CT for the detection of acute coronary syndromes in high-risk patients: a subgroup analysis of the ROMICAT trial

OBJECTIVES

To determine the incremental benefit of assessing myocardial perfusion defects (MPD) for acute coronary syndromes (ACS) over coronary and functional assessment by rest cardiac computed tomography (CT) in patients with acute chest pain.

BACKGROUND

Assessment of myocardial perfusion is feasible with cardiac CT; however, the diagnostic value of this assessment in patients at risk for ACS has not been demonstrated.

METHODS

The study included patients who presented to the emergency department with acute chest pain, nonischemic initial electrocardiogram (ECG), and negative cardiac biomarkers but had clinical suspicion for ACS and underwent invasive coronary angiography (ICA). Results were blinded to caregivers and patients. CT data sets were independently assessed for the presence of coronary plaque and stenosis, regional left ventricular function, and myocardial perfusion deficits by 2 blinded observers. Coronary angiography was assessed for the presence of stenosis, TIMI myocardial perfusion grade, and corrected TIMI frame count. The endpoint was ACS during index hospitalization.

RESULTS

We analyzed data from 35 subjects (69% male, mean age 58 ± 9 years) of whom 22 (63%) had ACS. The sensitivity and specificity of MPD for ACS were 86% (95% CI: 64%-96%) and 62% (95% CI: 32%-85%), respectively. Combined, MPD and RWMA assessment resulted in specificity and sensitivity of 86% (95% CI: 64%-96%) and 85% (95% CI: 54%-97%), respectively. Adding MPD and RWMA to the assessment for significant stenosis (>50%) resulted in a higher sensitivity of 91% (69-98%) and specificity of 85% (54-97%) and a significantly increased overall diagnostic accuracy when compared with assessment for stenosis (AUC: 0.88 vs 0.79; respectively, P = 0.02). Diagnostic accuracy of CT was not associated with impaired CTFC >40 or myocardial TIMI perfusion grade < 3.

CONCLUSIONS

Assessment of myocardial perfusion and regional wall motion abnormalities may enhance the ability of CT to detect ACS in patients with acute chest pain.

Detection of myocardial perfusion abnormalities using ultra-low radiation dose regadenoson stress multidetector computed tomography

BACKGROUND

The ability of multidetector computed tomography (MDCT) to detect stress-induced myocardial perfusion abnormalities is of great clinical interest as a potential tool for the combined evaluation of coronary stenosis and its significance. However, stress testing requires repeated scanning that is associated with additional radiation exposure and iodine contrast.

OBJECTIVE

Our goal was to determine the effects of reduced tube voltage and contrast dose on the ability to detect perfusion abnormalities.

METHODS

We studied 40 patients referred for coronary CT angiography (CTA) who agreed to undergo additional imaging after administration of an A(2A)-agonist (regadenoson 0.4 mg). Images were acquired at rest and during hyperemia with prospective gating with 120 kV tube voltage with 80-90 mL of contrast in 20 patients (group 1) and 100 kV with 55-70 mL of contrast in the remaining 20 patients (group 2). Custom 3D analysis software was used to define 3D myocardial segments and measure x-ray attenuation in each segment. In each group of patients, myocardial attenuation was averaged for segments supplied by coronary arteries with stenosis causing >50% luminal narrowing on coronary CTA and separately for segments supplied by arteries without significant stenosis.

RESULTS

Coronary CTA detected stenosis >50% in 23 of 120 coronary arteries in 16 of 40 patients. In all patients combined, myocardial attenuation increased from 86 ± 9 at rest to 110 ± 17 HU with stress, reflecting an increase in tissue blood flow, despite the decrease in left ventricular cavity attenuation (347 ± 72 to 281 ± 55 HU), reflecting an increase in cardiac output. Importantly, in both groups, myocardial attenuation was equally reduced in segments supplied by diseased arteries (group 1: 119 ± 19 vs 103 ± 14 HU, P < 0.05; group 2: 108 ± 20 vs 97 ± 16 HU, P < 0.05), despite the 74% reduction in radiation (from 7.4 ± 2.8 to 1.9 ± 0.45 mSv) and the 28% reduction in contrast dose (from 84 ± 7 to 60 ±7 mL) (both P < 0.05).

CONCLUSIONS

Regadenoson stress MDCT imaging can detect hypoperfused myocardium even when imaging settings are optimized to provide a significant reduction in radiation and contrast doses.

Myocardial perfusion defect in patients with coronary artery disease demonstrated by 64-multidetector computed tomography at rest

BACKGROUND

The first-pass imaging of 64-multidetector computed tomography (MDCT) using pharmacological stress has been used to assess myocardial perfusion. However, detection of myocardial ischemia at rest using MDCT has yet to be elucidated. We studied the incidence of myocardial perfusion defect (MPD) by 64-MDCT at rest and the effect of coronary revascularization therapy on MPD in patients with coronary artery disease.

HYPOTHESIS

MPD by 64-MDCT at rest indicates myocardial ischemia.

METHODS

We studied 76 patients with coronary artery disease who underwent 64-MDCT before and after revascularization therapy and 55 patients who did not undergo revascularization therapy. According to percent diameter stenosis, we defined group A, B, C, and D to have stenosis between 70% and 90%, 50% and 69%, 30% and 49%, and 10% and 29%, respectively. We evaluated regional myocardial contrast enhancement by long and short axis planes. MPD was defined as hypoenhancement area of some extent with CT value <50 HU during diastole.

RESULTS

MPD was found in 60.0% and 32.4% of group A and B patients, respectively (P = 0.0176). The incidence was 4.8% and 0% in group C and D patients, respectively (P<0.0001 compared with group A and B). All patients in group A and B and 2 patients with MPD in group C underwent coronary revascularization therapy. MPD disappeared after revascularization therapy in all but 3 group A patients. No patients showed new MPD after revascularization therapy.

CONCLUSIONS

Our results demonstrate that a significant percentage of patients with significant coronary artery stenosis show MPD by 64-MDCT at rest, and these MPDs may represent myocardial ischemia.

Incremental value of dual-energy CT to coronary CT angiography for the detection of significant coronary stenosis: comparison with quantitative coronary angiography and single photon emission computed tomography

To determine the value of dual-energy CT (DECT) and combined information of perfusion and angiography in diagnosing coronary artery disease (CAD), with single photon emission computed tomography (SPECT) and quantitative coronary angiography (QCA) as a reference standard. Thirty-four patients were enrolled in this study. DECT was used as a contrast-enhanced retrospectively ECG-gated scan protocol during the rest state and tubes were set at 140/100 kV. DECT angiography (DE-CTA) and DECT perfusion (DE-CTP) were calculated from two kV images. DE-CTP results were compared with SPECT and DE-CTA with QCA, respectively. The combined DE-CTP with DE-CTA data were compared to QCA in diagnosis of obstructive CAD (stenosis ≥ 50%). DECT showed diagnostic image quality in 31 patients. Using SPECT as a reference, DE-CTP had sensitivity of 68%, specificity of 93%, and sensitivity of 81%, and specificity of 92% for identifying any type of perfusion deficits on the segment- and territory-based analysis, respectively. Using QCA as a reference standard, DE-CTA showed sensitivity of 82%, specificity of 91% and accuracy of 86% for detecting ≥50% coronary stenosis on the vessel-based analysis, whereas the combination of DE-CTA and DE-CTP gave sensitivity of 90%, specificity of 86% and accuracy of 88% for detecting ≥50% coronary stenosis, respectively. Combination of DE-CTP and DE-CTA may improve diagnostic performance compared to CTA alone for the diagnosis of significant coronary stenosis.

Dual-energy computed tomography for integrative imaging of coronary artery disease: principles and clinical applications

The introduction of coronary CT angiography (cCTA) has reinvigorated the debate whether management of patients with suspected coronary artery disease (CAD) should be primarily based on physiological, functional versus anatomical testing. Anatomical testing (i.e., cCTA or invasive catheterization) enables direct visualization and grading of coronary artery stenoses but has shortcomings for gauging the hemodynamic significance of lesions for myocardial perfusion. Rest/stress myocardial perfusion imaging (MPI) has been extensively validated for assessing the clinical significance of CAD by demonstrating fixed or reversible perfusion defects but has only limited anatomical information. There is growing evidence that contrast medium enhanced dual-energy cCTA (DECT) has potential for the comprehensive analysis of coronary artery morphology as well as changes in myocardial perfusion. DECT exploits the fact that tissues in the human body and iodine-based contrast media have unique absorption characteristics when penetrated with different X-ray energy levels, which enables mapping the iodine (and thus blood) distribution within the myocardium. The purpose of this communication is to describe the practical application of this technology for the comprehensive diagnosis of ischemic heart disease. We examine recent scientific findings in the context of current pivotal transitions in cardiovascular disease management and demonstrate the potential of cardiac DECT for the integrative assessment of patients with known or suspected CAD within a single CT-based protocol.

Assessment of acute myocardial infarction: current status and recommendations from the North American society for Cardiovascular Imaging and the European Society of Cardiac Radiology

There are a number of imaging tests that are used in the setting of acute myocardial infarction and acute coronary syndrome. Each has their strengths and limitations. Experts from the European Society of Cardiac Radiology and the North American Society for Cardiovascular Imaging together with other prominent imagers reviewed the literature. It is clear that there is a definite role for imaging in these patients. While comparative accuracy, convenience and cost have largely guided test decisions in the past, the introduction of newer tests is being held to a higher standard which compares patient outcomes. Multicenter randomized comparative effectiveness trials with outcome measures are required.

Volumetric quantification of myocardial perfusion using analysis of multi-detector computed tomography 3D datasets: comparison with nuclear perfusion imaging

BACKGROUND

Although the ability of multi-detector computed tomography (MDCT) to detect perfusion abnormalities associated with acute and chronic myocardial infarction (MI) has been demonstrated, this methodology is based on visual interpretation of selected 2D slices.

OBJECTIVES

We sought to develop a new technique for quantitative volumetric analysis of myocardial perfusion from 3D datasets and test it against resting nuclear myocardial perfusion imaging (NMPI) reference.

METHODS

We studied 44 patients undergoing CTCA: a control group of 15 patients and a study group of 29 patients. MDCT datasets acquired for CTCA were analyzed using custom software designed to: (1) generate bull's eye display of myocardial perfusion and (2) calculate a quantitative index of extent and severity of perfusion abnormality, Q(H), for 16 volumetric myocardial segments. Visual interpretation of MDCT-derived bull's eyes was compared with rest NMPI scores using kappa statistics of agreement on a coronary territory and patient basis. Quantitative MDCT perfusion data were correlated with rest NMPI summed scores and used for objective detection of perfusion defects.

RESULTS

Visual analysis of MDCT-derived bull's eyes accurately detected perfusion defects in agreement with NMPI (kappa = 0.70 by territory; 0.79 by patient). Quantitative data were in good agreement with NMPI, as reflected by: (1) correlation of 0.87 (territory) and 0.84 (patient) between summed Q(H) and NMPI scores, (2) area under ROC curve 0.87 with sensitivity of 0.79-0.92, specificity 0.83-0.91, and accuracy 0.83-0.89 for objective detection of abnormalities.

CONCLUSIONS

Our new technique for volumetric analysis of 3D MDCT images allows accurate objective detection of perfusion defects. This perfusion information can be obtained without additional radiation or contrast load, and may aid in elucidating the significance of coronary lesions.