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

An Image-Based Prior Knowledge-Free Approach for a Multi-Material Decomposition in Photon-Counting Computed Tomography

Photon-counting CT systems generally allow for acquiring multiple spectral datasets and thus for decomposing CT images into multiple materials. We introduce a prior knowledge-free deterministic material decomposition approach for quantifying three material concentrations on a commercial photon-counting CT system based on a single CT scan. We acquired two phantom measurement series: one to calibrate and one to test the algorithm. For evaluation, we used an anthropomorphic abdominal phantom with inserts of either aqueous iodine solution, aqueous tungsten solution, or water. Material CT numbers were predicted based on a polynomial in the following parameters: Water-equivalent object diameter, object center-to-isocenter distance, voxel-to-isocenter distance, voxel-to-object center distance, and X-ray tube current. The material decomposition was performed as a generalized least-squares estimation. The algorithm provided material maps of iodine, tungsten, and water with average estimation errors of 4% in the contrast agent maps and 1% in the water map with respect to the material concentrations in the inserts. The contrast-to-noise ratio in the iodine and tungsten map was 36% and 16% compared to the noise-minimal threshold image. We were able to decompose four spectral images into iodine, tungsten, and water.

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.

Evaluation of myocardial viability in patients with myocardial ischemia reperfusion injury using the dual-energy CT myocardial blood pool imaging

OBJECTIVES

To evaluate myocardial viability in patients with myocardial ischemia reperfusion injury (MIRI) via dual-energy computed tomography myocardial blood pool imaging (DECT MBPI).

METHODS

Between September 2017 and January 2019, we prospectively recruited 59 patients with acute myocardial infarction (AMI) who developed MIRI after revascularization during invasive coronary angiography (ICA). Then, they received DECT MBPI, SPECT, and PET sequentially within 1 week after the onset of MIRI. A total of 1003 myocardial segments of 59 patients were recruited for this study. The iodine reduction areas and delayed enhancement areas were calculated by cardiac iodine map with SPECT rest myocardial perfusion imaging (MPI) + PET myocardial metabolism imaging (MMI) as reference criteria. The paired sample t-test was used to measure the difference of the myocardial iodine value. Cohen's Kappa analysis was used to test the consistency among different observers. ROC analysis was used to calculate the myocardial viability of DECT MBPI.

RESULTS

ROC showed the AUCs of DECT MBPI iodine value to identify a normal myocardium, an ischemic myocardium, and an infarcted myocardium were 0.957, 0.900, and 0.906 (p < 0.001). The sensitivity, specificity, and accuracy of DECT MBPI in identifying an ischemic myocardium were 87.6%, 89.3%, and 97.9% (p < 0.001). The sensitivity, specificity, and accuracy of DECT MBPI in identifying an infarcted myocardium were 88.9%, 92.2%, and 98.6% (p < 0.001). The cutoff value for DECT MBPI to differentiate between an ischemic and a normal myocardium was 0.84 mg I/mL. The cutoff value for DECT MBPI to differentiate between an infarct and a normal myocardium was 2.01 mg I/mL.

CONCLUSION

DECT MBPI can be used to assess myocardial viability in patients with MIRI with high sensitivity and specificity.

KEY POINTS

• Dual-energy computed tomography myocardial blood pool imaging (DECT MBPI) can evaluate myocardial viability of myocardial ischemia-reperfusion injury (MIRI). • DECT MBPI is a non-invasive and timesaving method for evaluation on myocardial ischemia-reperfusion injury in patients with acute myocardial infarction after coronary intervention.

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.

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.

Computed tomography of cardiomyopathies

Cardiac computed tomography (CT) is increasingly used in the evaluation of cardiomyopathies, particularly in patients who are not able to undergo other non-invasive imaging tests such as magnetic resonance imaging (MRI) due to the presence of MRI-incompatible pacemakers/defibrillators or other contraindications or due to extensive artifacts from indwelling metallic devices. Advances in scanner technology enable acquisition of CT images with high spatial resolution, good temporal resolution, wide field of view and multi-planar reconstruction capabilities. CT is useful in cardiomyopathies in several ways, particularly in the evaluation of coronary arteries, characterization of cardiomyopathy phenotype, quantification of cardiac volumes and function, treatment-planning, and post-treatment evaluation. In this article, we review the imaging techniques and specific applications of CT in the evaluation of cardiomyopathies.

Diagnostic accuracy of coronary CT angiography combined with dual-energy myocardial perfusion imaging for detection of myocardial infarction

The aim of the present study was to evaluate the diagnostic accuracy of second generation dual-energy computed tomography (DECT) myocardial perfusion imaging for the detection of myocardial infarction (MI) in patients with suspected MI. In total, 56 patients underwent DECT. Among those, 40 patients had MI that was detected by catheter coronary angiography and cardiac troponin I elevation and evolution of acute MI detected by electrocardiogram changes. The diagnostic accuracy, including the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for the detection of MI were evaluated, as well as the coronary image quality of coronary artery and radiation dose. The sensitivity, specificity, PPV and NPV for the detection of MI were 95.0, 97.0, 86.4 and 98.9%, respectively. Moreover, the image quality was rated excellent (score 1) in 90.2% (515/571), good (score 2) in 6.5% (37/571), adequate (score 3) in 1.9% (11/571) and non-diagnostic (score 4) in 1.4% (8/571) of the coronary segments. The effective radiation dose was on average 6.1±1.5 mSv (3.1–10.9 mSv). Therefore, combined DE iodine maps and coronary CT angiography using the DECT may provide a high diagnostic accuracy for detecting MI with lower radiation exposure in patients with suspected MI.

Spectral detector CT for cardiovascular applications

Spectral detector computed tomography (SDCT) is a novel technology that uses two layers of detectors to simultaneously collect low and high energy data. Spectral data is used to generate conventional polyenergetic images as well as dedicated spectral images including virtual monoenergetic and material composition (iodine-only, virtual unenhanced, effective atomic number) images. This paper provides an overview of SDCT technology and a description of some spectral image types. The potential utility of SDCT for cardiovascular imaging and the impact of this new technology on radiation and contrast dose are discussed through presentation of initial patient studies performed on a SDCT scanner. The value of SDCT for salvaging suboptimal studies including those with poor contrast-enhancement or beam hardening artifacts through retrospective reconstruction of spectral data is discussed. Additionally, examples of specific benefits for the evaluation of aortic disease, imaging before transcatheter aortic valve implantation, evaluation of pulmonary veins pre- and post-pulmonary radiofrequency ablation, evaluation of coronary artery lumen, assessment of myocardial perfusion, detection of pulmonary embolism, and characterization of incidental findings are presented.

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.

Dual-energy computed tomography for detection of coronary artery disease

Recent technological advances in computed tomography (CT) technology have fulfilled the prerequisites for the cardiac application of dual-energy CT (DECT) imaging. By exploiting the unique characteristics of materials when exposed to two different x-ray energies, DECT holds great promise for the diagnosis and management of coronary artery disease. It allows for the assessment of myocardial perfusion to discern the hemodynamic significance of coronary disease and possesses high accuracy for the detection and characterization of coronary plaques, while facilitating reductions in radiation dose. As such, DECT enabled cardiac CT to advance beyond the mere detection of coronary stenosis expanding its role in the evaluation and management of coronary atherosclerosis.

Beam hardening artifact reduction using dual energy computed tomography: implications for myocardial perfusion studies

BACKGROUND

Myocardial computed tomography perfusion (CTP) using conventional single energy (SE) imaging is influenced by the presence of beam hardening artifacts (BHA), occasionally resembling perfusion defects and commonly observed at the left ventricular posterobasal wall (PB). We therefore sought to explore the ability of dual energy (DE) CTP to attenuate the presence of BHA.

METHODS

Consecutive patients without history of coronary artery disease who were referred for computed tomography coronary angiography (CTCA) due to atypical chest pain and a normal stress-rest SPECT and had absence or mild coronary atherosclerosis constituted the study population. The study group was acquired using DE and the control group using SE imaging.

RESULTS

Demographical characteristics were similar between groups, as well as the heart rate and the effective radiation dose. Myocardial signal density (SD) levels were evaluated in 280 basal segments among the DE group (140 PB segments for each energy level from 40 to 100 keV; and 140 reference segments), and in 40 basal segments (at the same locations) among the SE group. Among the DE group, myocardial SD levels and myocardial SD ratio evaluated at the reference segment were higher at low energy levels, with significantly lower SD levels at increasing energy levels. Myocardial signal-to-noise ratio was not significantly influenced by the energy level applied, although 70 keV was identified as the energy level with the best overall signal-to-noise ratio. Significant differences were identified between the PB segment and the reference segment among the lower energy levels, whereas at ≥70 keV myocardial SD levels were similar. Compared to DE reconstructions at the best energy level (70 keV), SE acquisitions showed no significant differences overall regarding myocardial SD levels among the reference segments.

CONCLUSIONS

BHA that influence the assessment of myocardial perfusion can be attenuated using DE at 70 keV or higher.

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.

Adenosine triphosphate stress dual-source computed tomography to identify myocardial ischemia: comparison with invasive coronary angiography

PURPOSE

The purpose of this study was to investigate the utility incremental diagnostic value of combined assessment with coronary CT angiography (CCTA) and myocardial CT perfusion imaging (CTP) using dual-energy technology with an Adenosine Triphosphate (ATP) load technique.

MATERIALS AND METHODS

Twenty-one patients underwent ATP-provocation dual-energy CT and CAG. We compared the diagnostic accuracy with CAG, for ischemic region due coronary stenosis by CCTA alone and CCTA combined with CTP (Combined CCTA/CTP).

RESULTS

All of 21 patients CTP images could be evaluated, however 8 CCTA images could not be evaluated by calcification and motion artifact, so assessability was 61.9% (13/21) for CCTA alone, and 100% for Combined CCTA/CTP. With CAG results as a comparison, the sensitivity, specificity, positive predictive value, and negative predictive value were, respectively, 83.3% (20/24), 74.4% (29/39), 66.7% (20/30), and 87.8% (29/33) for CCTA alone, and 66.7% (16/24), 92.3% (36/39), 84.2% (16/19), and 81.8% (36/44) for combined CCTA/CTP. The diagnostic accuracy of the two methods were 77.8% (49/63) and 82.5% (52/63).

CONCLUSION

Dual-energy CT may be a useful modality for perfusion assessment and correlated well with the severity of stenosis on CAG. This technique may even be of use in cases of severe calcification in the coronary artery wall.

Acute myocardial infarct detection with dual energy CT: correlation with single photon emission computed tomography myocardial scintigraphy in a canine model

BACKGROUND

Dual-energy CT (DECT) has been used to detect myocardial infarct. However, few comparable studies with histopathological findings as gold standard have been published.

PURPOSE

To investigate the accuracy of DECT iodine maps for detecting acute myocardial infarction compared with single photon emission computed tomography (SPECT) in a canine model using histopathological findings as the reference standard.

MATERIAL AND METHODS

A model of myocardial ischemia was created by ligating the left anterior descending (LAD) coronary artery after thoracotomy in six dogs, while another three dogs undergoing thoracotomy without LAD ligature served as a control group. Contrast-enhanced DECT scans of the heart were performed, followed by resting 99mTc-MIBI SPECT myocardial perfusion imaging in all nine dogs before and 3 h after the procedure. Triphenyltetrazolium chloride (TTC) staining was performed and analyzed. In the short axis of the left ventricle, the wall surface was divided into 17 segments, which were assessed for infarcted myocardium on conventional CT from average-weighted data, DECT myocardial iodine maps, conventional CT plus DECT, SPECT, and histopathology. Inter-observer and inter-modality agreement for conventional CT, DECT myocardial iodine maps, and SPECT were calculated. CT value of infracted and non-infracted areas was measured.

RESULTS

With the histopathological results as the reference standard, the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were 75.0% (30/40), 92.0% (104/113), 76.9% (30/39), 91.2% (104/114), 87.6% (134/153) for conventional CT, 85.0% (34/40), 84.1% (95/113), 65.4% (34/52), 94.1% (95/101), 84.3% (129/153) for DECT myocardial iodine maps; 87.5% (35/40), 92.9% (105/113), 81.4% (35/43), 95.5% (105/110), 91.5% (140/153) for conventional CT plus DECT; 82.5% (33/40), 90.3% (102/113), 75.0% (33/44), and 93.6% (102/109), 88.2% (135/153) for SPECT, respectively. Excellent inter-observer agreement (Kappa value >0.8) and good inter-modality agreement (Kappa value >0.6) for each modality were found. CT values of infarcted myocardium (26 ± 22 HU, 36 ± 33 HU, 34 ± 16 HU) were lower than those of non-infarcted myocardium (115 ± 16 HU, 121 ± 28 HU, 123 ± 11 HU) on images of 140 kVp, 80 kVp, and average-weighted 120 kVp images (all P < 0.05).

CONCLUSION

With histopathology as the reference standard, DECT myocardial iodine maps can detect acute myocardial infarction with diagnostic accuracy comparable to resting SPECT myocardial perfusion imaging in a canine model. DECT plus conventional CT had a potential to improve the detection of acute myocardial infarction.

Dual-energy CT imaging of thoracic malignancies

Computed tomography (CT) plays a pivotal role in the detection, characterization, and staging of lung cancer and other thoracic malignancies. Since the introduction of clinically viable dual-energy CT techniques, substantial evidence has accumulated on the use of this modality for imaging chest malignancies. This article describes the principles of dual-energy CT along with suitable image acquisition, reconstruction, and postprocessing strategies for oncologic applications in the chest. The potential of dual-energy CT techniques for the detection, characterization, staging, and surveillance of chest malignancy, as well as the limitations of this modality are discussed.

Dual-energy CT of the heart

OBJECTIVE

Interest in dual-energy CT (DECT) for evaluating the myocardial blood supply, as an addition to coronary artery assessment, is increasing. Although it is still in the early clinical phase, assessment of myocardial ischemia and infarction by DECT constitutes a promising step toward comprehensive evaluation of coronary artery disease with a single noninvasive modality.

CONCLUSION

Compared with dynamic CT approaches, DECT has advantages regarding radiation dose and clinical applicability. In this review, the literature on DECT of the heart is discussed.

Dual-energy CT: radiation dose aspects

OBJECTIVE

Various applications for dual-energy CT (DECT) have been investigated and have shown substantial clinical benefits. However, only limited data are available regarding the radiation dose associated with DECT imaging. The purpose of this article is to review the available literature regarding the radiation dose associated with DECT imaging applications in comparison with conventional single-energy CT techniques.

CONCLUSION

The rediscovery of DECT and the increasing availability of this technique on clinical CT systems have opened new dimensions for CT. The advanced spectral differentiation of materials within the human body as well as the selective visualization or subtraction of iodinated contrast material or xenon provides both advanced visualization of disease-specific molecular substrates as well as additional functional information within a single scan.

Dual-energy CT of the brain and intracranial vessels

OBJECTIVE

The purpose of this review is to summarize the principles and applications of dual-energy CT in evaluation of the brain and the intracranial blood vessels.

CONCLUSION

One major advantage of dual-energy CT is the capability of material differentiation. In general, this property can be applied to bone removal in CT angiography for easier and faster postprocessing. In neuroradiology, material decomposition allows detection of hemorrhage on contrast-enhanced CT scans and facilitates the search for the underlying pathologic mechanism of hematomas. The combination of low radiation dose and advantageous spectral information (blood vs contrast) from these datasets justifies broad clinical implementation of dual-energy CT in neuroradiology.

[Dual-energy computed tomography: what is it useful for?]

Dual-energy CT is one of the newest and most attractive fields in radiology today. New generation scanners can acquire datasets with different X-ray spectra, which facilitates the characterization of certain chemical elements, making it possible to detect functional alterations in the absence of morphologic or densitometric anomalies. The capability of characterizing these elements is enabling new applications to be developed for clinical practice and changing the way we work. The aim of this article is to explain what dual-energy CT studies are, the techniques available for performing them, the advantages and disadvantages of these studies, and what we might expect from this field in the future.

Diagnostic performance of combined noninvasive anatomic and functional assessment with dual-source CT and adenosine-induced stress dual-energy CT for detection of significant coronary stenosis

OBJECTIVE

The purpose of our study was to prospectively evaluate the incremental diagnostic value of combined dual-source coronary CT angiography (CTA) and CT myocardial perfusion imaging (MPI) for the detection of significant coronary stenoses.

SUBJECTS AND METHODS

Forty-five patients with known coronary artery disease detected by dual-source coronary CTA were investigated by adenosine-induced stress dual-source CTA and conventional coronary angiography. Analysis was performed in three steps: classification of coronary stenosis severity using dual-source coronary CTA, identification of myocardial perfusion defects using rest and stress CT MPI, and reclassification of coronary stenosis severity according to combined dual-source coronary CTA and CT MPI. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of dual-source coronary CTA before and after CT MPI were calculated on a per-vessel basis compared with conventional coronary angiography as the standard of reference.

RESULTS

Dual-source coronary CTA revealed 87 significantly stenotic vessels in 45 patients. Conventional coronary angiography revealed significant stenoses in 73 vessels in 42 patients. CT MPI showed myocardial perfusion defects in 81 vessel territories in 43 patients. After the CT MPI analysis, dual-source coronary CTA identified significant stenoses in 77 coronary vessels in 42 patients. Sensitivity, specificity, PPV, and NPV of the dual-source coronary CTA on a per-vessel basis before CT MPI were 91.8%, 67.7%, 73.6%, and 87.5%, respectively, and after CT MPI were 93.2%, 85.5%, 88.3%, and 91.4%, respectively. The area under the receiver operating characteristic curve increased significantly from 0.798 to 0.893 (p = 0.004).

CONCLUSION

Combined dual-source coronary CTA and CT MPI provides incremental diagnostic value compared with dual-source coronary CTA alone for the detection of significant coronary stenoses.

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.

Quantitative myocardial CT perfusion: a pictorial review and the current state of technology development

Coronary artery disease (CAD) is one of the leading causes of morbidity and mortality, and is associated with substantial and increasing resource burden. A combined physiologic and anatomic assessment may improve identification of patients with CAD who would benefit from revascularization and reduce unnecessary diagnostic and interventional procedures. Cardiovascular computed tomography (CT) has the potential to provide a comprehensive evaluation of CAD in a single setting. Although coronary CT angiography has been widely implemented for clinical use, the application of myocardial CT perfusion (CTP) has been relatively restricted because of a few limitations, such as beam hardening and the high radiation dose delivered. In this article, we first review the fundamental basis of the qualitative, semiquantitative, and quantitative techniques for myocardial CTP and discussed the strength and weakness of each approach. Beam-hardening correction for myocardial CTP with image-based method and dual-energy CT are then discussed with example cases demonstrating the effectiveness of each method. Initial experiences suggest both techniques can reduce beam-hardening artifact to a satisfactory extent. An overview on dose reduction technologies, such as prospective ECG triggering and iterative reconstruction for myocardial CTP, is also provided. Preclinical studies suggest it is feasible to perform low-dose quantitative myocardial CTP without affecting perfusion measurement. Finally, the impact of scan length on myocardial CTP is addressed.

Computed tomography imaging in myocardial infarction

Over recent decades, noninvasive imaging has become well established in the diagnostic work-up of patients suffering from myocardial infarction. It provides insights into the individual patient's prognosis and guides therapeutic decisions. MRI has long been considered the standard of reference in the noninvasive imaging of myocardial infarction. Only recently have different multidetector-row spiral computed tomography (MDCT) techniques successfully been evaluated for the visualization of myocardial infarction. This article describes different concepts of cardiac MDCT imaging in acute and chronic myocardial infarction. MDCT assessment of myocardial edema, myocardial perfusion and delayed myocardial contrast enhancement are introduced, with the latter evolving as key concept of viability imaging by means of MDCT. The current status of MDCT in the diagnostic work-up of myocardial infarction is reviewed.

Feasibility and accuracy of tissue characterization with dual source computed tomography

PURPOSE

To evaluate the feasibility and accuracy of a model for tissue characterization with dual source computed tomography (DSCT).

METHODS AND MATERIALS

A model for tissue characterization in CT was used with a parameterization of linear attenuation coefficients. Sixteen chemical substances with effective atomic numbers between 5.21 and 13.08 and electron densities between 2.20 and 4.12 x10(23) electrons/cm(3) were scanned at energies of 80 and 140 kV on a DSCT. From the reconstructed dual energy data sets, effective atomic numbers and electron densities of the substances were calculated.

RESULTS

Our presented model using DSCT approximated the effective atomic numbers and effective electron densities of 16 substances very well. The measured effective atomic numbers deviated 3.4 ± 6.8% (R(2) = 0.994) from theoretical effective atomic numbers. In addition, measured effective electron densities deviated -0.6 ± 2.2% (R(2) = 0.999) from theoretical effective electron densities.

CONCLUSION

Effective atomic numbers and effective electron densities can be determined with a high accuracy with DSCT. Therefore the model can be of potential benefit for clinical applications of quantitative tissue characterization with DSCT.