Comparison of multislice computed tomography with intravascular ultrasound for detection and characterization of coronary artery plaques: A systematic review

Assessment of Dynamic Change of Coronary Artery Geometry and Its Relationship to Coronary Artery Disease, Based on Coronary CT Angiography

To investigate the relationship between dynamic changes of coronary artery geometry and coronary artery disease (CAD) using computed tomography (CT). Seventy-one patients underwent coronary CT angiography with retrospective electrocardiographic gating. End-systolic (ES) and end-diastolic (ED) phases were automatically determined by dedicated software. Centerlines were extracted for the right and left coronary artery. Differences between ES and ED curvature and tortuosity were determined. Associations of change in geometrical parameters with plaque types and degree of stenosis were investigated using linear mixed models. The differences in number of inflection points were analyzed using Wilcoxon signed-rank tests. Tests were done on artery and segment level. One hundred thirty-seven arteries (64.3%) and 456 (71.4%) segments were included. Curvature was significantly higher in ES than in ED phase for arteries (p = 0.002) and segments (p < 0.001). The difference was significant only at segment level for tortuosity (p = 0.005). Number of inflection points was significantly higher in ES phase on both artery and segment level (p < 0.001). No significant relationships were found between degree of stenosis and plaque types and dynamic change in geometrical parameters. Non-invasive imaging by cardiac CT can quantify change in geometrical parameters of the coronary arteries during the cardiac cycle. Dynamic change of vessel geometry through the cardiac cycle was not found to be related to the presence of CAD.

Extraction of Coronary Atherosclerotic Plaques From Computed Tomography Imaging: A Review of Recent Methods

Background: Atherosclerotic plaques are the major cause of coronary artery disease (CAD). Currently, computed tomography (CT) is the most commonly applied imaging technique in the diagnosis of CAD. However, the accurate extraction of coronary plaque geometry from CT images is still challenging.

Summary of Review: In this review, we focused on the methods in recent studies on the CT-based coronary plaque extraction. According to the dimension of plaque extraction method, the studies were categorized into two-dimensional (2D) and three-dimensional (3D) ones. In each category, the studies were analyzed in terms of data, methods, and evaluation. We summarized the merits and limitations of current methods, as well as the future directions for efficient and accurate extraction of coronary plaques using CT imaging.

Conclusion: The methodological innovations are important for more accurate CT-based assessment of coronary plaques in clinical applications. The large-scale studies, de-blooming algorithms, more standardized datasets, and more detailed classification of non-calcified plaques could improve the accuracy of coronary plaque extraction from CT images. More multidimensional geometric parameters can be derived from the 3D geometry of coronary plaques. Additionally, machine learning and automatic 3D reconstruction could improve the efficiency of coronary plaque extraction in future studies.

High-Risk Coronary Plaque Regression After Intensive Lifestyle Intervention in Nonobstructive Coronary Disease: A Randomized Study

OBJECTIVES

The authors sought to study the impact of diet and lifestyle intervention on changes in atherosclerotic plaque volume and composition.

BACKGROUND

Lifestyle and diet modification are the leading strategies to manage coronary artery disease; however, their direct impact on atherosclerosis remains unknown. Coronary plaque composition is related to the risk of future cardiovascular events independent of stenosis severity and can be conveniently evaluated with computed tomography angiography (CTA).

METHODS

We enrolled 92 patients (41% women; mean age 60 ± 7.7 years) with nonobstructive (<70% stenosis) coronary atherosclerosis identified by CTA. Participants were randomized (1:1) to either the DISCO (Dietary Intervention to Stop Coronary Atherosclerosis in Computed Tomography) intervention group (systematic follow-up by a dietitian to adhere to the Dietary Approaches to Stop Hypertension nutrition model together with optimal medical therapy [OMT]) or the control group (OMT alone). In all patients, CTA was repeated after 66.9 ± 13.7 weeks. The outcome was change (Δ) in atheroma volume and plaque composition. Based on atherosclerotic tissue attenuation ranges in Hounsfield units (HU), the following components of coronary plaque were distinguished: dense calcium (>351 HU), fibrous plaque (151 to 350 HU), and fibrofatty plaque combined with necrotic core (-30 to 150 HU), referred to as noncalcified plaque.

RESULTS

Percent atheroma volume increased in the control arm (Δ = +1.1 ± 3.4%; p = 0.033) versus no significant change in the experimental arm (Δ = +1.0% ± 4.2%; p = 0.127; intergroup p = 0.851). There was a reduction in noncalcified plaque in both the experimental arm (Δ = -51.3 ± 79.5 mm³ [-1.7 ± 2.7%]; p < 0.001) and the control arm (Δ = -21.3 ± 57.7 [-0.7 ± 1.9%]; p = 0.018), which was greater in the DISCO intervention group (intergroup p = 0.045). No differences in fibrous component or dense calcium changes were observed between the groups.

CONCLUSIONS

Controlled diet and lifestyle intervention together with OMT may slow the progression of atherosclerosis and reduce noncalcified plaque volume compared to OMT alone. (Dietary Intervention to Stop Coronary Atherosclerosis in Computed Tomography [DISCO-CT]; NCT02571803).

Progression of coronary artery disease. Experience with computed tomography

Coronary artery disease (CAD) begins with asymptomatic atherosclerotic changes in the vessel wall. Gradual or abrupt progression of some of these early lesions eventually leads to symptomatic luminal narrowing. Coronary computed tomography angiography (CTA) allows for a minimally invasive assessment of these wall changes and of the severity of luminal narrowing, and is thus an attractive method for assessing progression/regression. However, because of the associated radiation exposure and concern about false-positive findings, CTA is not recommended as a clinical screening test. Owing to the significantly lower spatial resolution compared with invasive modalities, its application as a tool for clinical progression/regression trials is limited. Therefore, while there are extensive data from both CT coronary artery calcium scoring and CTA studies demonstrating the prognostic value of luminal stenosis as well as the extent and characteristics of plaque, data describing progression/regression are limited.

Effects of intensive lipid-lowering therapy on coronary plaques composition in patients with acute myocardial infarction: Assessment with serial coronary CT angiography

BACKGROUND

Statins have been shown to possess favourable effects on the cardiovascular system with stabilization of the vulnerable plaque. We sought to assess the effects of early aggressive statin treatment on plaque composition in patients with acute myocardial infarction (AMI), using serial assessment with coronary CT-angiography (CTA).

METHODS

In a prospective randomized blinded endpoint trial patients with AMI were randomized to an intensive lipid lowering treatment receiving statin loading with 80 mg rosuvastatin followed by 40 mg daily or standard statin therapy according to current guidelines. Patients were assessed with CTA at baseline and after 12 months with evaluation of plaque volume and composition.

RESULTS

In total, 140 patients with AMI were randomized and plaque composition was assessed in 96 patients. In the intensive care group LDL-level was median 1.3 [0.9; 1.5] mmol/l at 12 months follow-up and 2.0 [1.7; 2.4] mmol/l in the usual care group, p < 0.001. Plaque volume increased over 12 months with 43.5 (±225.8) mm(3) in the intensive care group and 19.1 (±190.2) mm(3) in the usual care group, p = 0.57. Plaque composition changed over 12 months with an increase in total dense calcium volume by 11.1 (±39.6) mm(3), corresponding to a 23% increase, in the intensive care group and a decreased by -0.4 (±26.6) mm(3) in the usual care group, p < 0.001. Necrotic core volume increased 26.8 (±122.1) mm(3) in the intensive care group and 25.2 (±80.1) mm(3) in the usual care group, p = 0.94.

CONCLUSIONS

Early aggressive lipid lowering therapy significantly increases dense calcium volume in patients with AMI.

Value of Hybrid Imaging with PET/CT to Guide Percutaneous Revascularization of Chronic Total Coronary Occlusion

Chronic total coronary occlusions (CTO) are documented in approximately one fifth of diagnostic invasive coronary angiographies (ICA). Percutaneous coronary interventions (PCI) of CTO are challenging and are accompanied by higher complication and lower success rates in comparison with non-CTO PCI. Scrutinous evaluation of ischemia and viability to justify percutaneous revascularization is therefore of importance to select eligible patients for such a procedure. Furthermore, knowledge of the anatomical features of the occlusion may predict the chances of success of PCI CTO and could even guide the procedural strategy to augment the likelihood of recanalization. Positron emission tomography (PET) is unequivocally accepted as the reference standard for ischemia and viability testing, whereas coronary computed tomography angiography (CCTA) currently allows for non-invasive detailed three-dimensional imaging of the coronary anatomy that adds morphological information over two-dimensional ICA. Hybrid PET/CT could therefore be useful for optimal patient selection as well as procedural planning. This review discusses the potential value of PET/CT to guide PCI in CTOs.

Comparison between MDCT and Grayscale IVUS in a Quantitative Analysis of Coronary Lumen in Segments with or without Atherosclerotic Plaques

Background

The diagnostic accuracy of 64-slice MDCT in comparison with IVUS has been poorly described and is mainly restricted to reports analyzing segments with documented atherosclerotic plaques.

Objectives

We compared 64-slice multidetector computed tomography (MDCT) with gray scale intravascular ultrasound (IVUS) for the evaluation of coronary lumen dimensions in the context of a comprehensive analysis, including segments with absent or mild disease.

Methods

The 64-slice MDCT was performed within 72 h before the IVUS imaging, which was obtained for at least one coronary, regardless of the presence of luminal stenosis at angiography. A total of 21 patients were included, with 70 imaged vessels (total length 114.6 ± 38.3 mm per patient). A coronary plaque was diagnosed in segments with plaque burden > 40%.

Results

At patient, vessel, and segment levels, average lumen area, minimal lumen area, and minimal lumen diameter were highly correlated between IVUS and 64-slice MDCT (p < 0.01). However, 64-slice MDCT tended to underestimate the lumen size with a relatively wide dispersion of the differences. The comparison between 64-slice MDCT and IVUS lumen measurements was not substantially affected by the presence or absence of an underlying plaque. In addition, 64-slice MDCT showed good global accuracy for the detection of IVUS parameters associated with flow-limiting lesions.

Conclusions

In a comprehensive, multi-territory, and whole-artery analysis, the assessment of coronary lumen by 64-slice MDCT compared with coronary IVUS showed a good overall diagnostic ability, regardless of the presence or absence of underlying atherosclerotic plaques.

Is quality and completeness of reporting of systematic reviews and meta-analyses published in high impact radiology journals associated with citation rates?

Purpose

The purpose of this study is to determine whether study quality and completeness of reporting of systematic reviews (SR) and meta-analyses (MA) published in high impact factor (IF) radiology journals is associated with citation rates.

Methods

All SR and MA published in English between Jan 2007–Dec 2011, in radiology journals with an IF >2.75, were identified on Ovid MEDLINE. The Assessing the Methodologic Quality of Systematic Reviews (AMSTAR) checklist for study quality, and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist for study completeness, was applied to each SR & MA. Each SR & MA was then searched in Google Scholar to yield a citation rate. Spearman correlation coefficients were used to assess the relationship between AMSTAR and PRISMA results with citation rate. Multivariate analyses were performed to account for the effect of journal IF and journal 5-year IF on correlation with citation rate. Values were reported as medians with interquartile range (IQR) provided.

Results

129 studies from 11 journals were included (50 SR and 79 MA). Median AMSTAR result was 8.0/11 (IQR: 5–9) and median PRISMA result was 23.0/27 (IQR: 21–25). The median citation rate for SR & MA was 0.73 citations/month post-publication (IQR: 0.40–1.17). There was a positive correlation between both AMSTAR and PRISMA results and SR & MA citation rate; ρ=0.323 (P=0.0002) and ρ=0.327 (P=0.0002) respectively. Positive correlation persisted for AMSTAR and PRISMA results after journal IF was partialed out; ρ=0.243 (P=0.006) and ρ=0.256 (P=0.004), and after journal 5-year IF was partialed out; ρ=0.235 (P=0.008) and ρ=0.243 (P=0.006) respectively.

Conclusion

There is a positive correlation between the quality and the completeness of a reported SR or MA with citation rate which persists when adjusted for journal IF and journal 5-year IF.

Coronary CT angiography in the quantitative assessment of coronary plaques

Coronary computed tomography angiography (CCTA) has been recently evaluated for its ability to assess coronary plaque characteristics, including plaque composition. Identification of the relationship between plaque composition by CCTA and patient clinical presentations may provide insight into the pathophysiology of coronary artery plaque, thus assisting identification of vulnerable plaques which are associated with the development of acute coronary syndrome. CCTA-generated 3D visualizations allow evaluation of both coronary lesions and lumen changes, which are considered to enhance the diagnostic performance of CCTA. The purpose of this review is to discuss the recent developments that have occurred in the field of CCTA with regard to its diagnostic accuracy in the quantitative assessment of coronary plaques, with a focus on the characterization of plaque components and identification of vulnerable plaques.

A meta analysis and hierarchical classification of HU-based atherosclerotic plaque characterization criteria

Background

Many computed tomography (CT) studies have reported that lipid-rich, presumably rupture-prone atherosclerotic plaques can be characterized according to their Hounsfield Unit (HU) value. However, the published HU-based characterization criteria vary considerably. The present study aims to systematically analyze these values and empirically derive a hierarchical classification of the HU-based criteria which can be referred in clinical situation.

Material and Methods

A systematic search in PubMed and Embase for publications with HU-criteria to characterize lipid-rich and fibrous atherosclerotic plaques resulted in 36 publications, published between 1998 and 2011. The HU-criteria were systematically analyzed based on the characteristics of the reporting study. Significant differences between HU-criteria were checked using Student’s t-test. Subsequently, a hierarchical classification of HU-criteria was developed based on the respective study characteristics.

Results

No correlation was found between HU-criteria and the reported lumen contrast-enhancement. Significant differences were found for HU-criteria when pooled according to the respective study characteristics: examination type, vessel type, CT-vendor, detector-rows, voltage-setting, and collimation-width. The hierarchical classification resulted in 21 and 22 CT attenuation value categories, for lipid-rich and fibrous plaque, respectively. More than 50% of the hierarchically classified HU-criteria were significantly different.

Conclusion

In conclusion, variations in the reported CT attenuation values for lipid-rich and fibrous plaque are so large that generalized values are unreliable for clinical use. The proposed hierarchical classification can be used to determine reference CT attenuation values of lipid-rich and fibrous plaques for the local setting.

Non-invasive imaging in coronary artery disease including anatomical and functional evaluation of ischaemia and viability assessment

Coronary artery disease has an important impact on the morbidity and mortality statistics and health economics worldwide. Diagnosis of coronary artery disease is important in risk stratification and guides further management. Invasive coronary angiography is the traditional method of imaging the coronary arteries and remains the gold standard. It detects luminal stenosis but provides little information about the vessel wall or plaques. Besides, not all anatomical lesions are functionally significant. This has lent itself to a wide variety of imaging techniques to identify and assess a flow-limiting stenosis. The approach to diagnosis of coronary artery disease is broadly based on anatomical and functional imaging. Coronary CT and MRI of coronary arteries provide an anatomical assessment of coronary stenosis. Coronary calcium score and coronary CT assess subclinical atherosclerosis by assessing the atherosclerotic plaque burden. The haemodynamic significance of a coronary artery stenosis can be assessed by stress radioisotope studies, stress echocardiography and stress MRI. The more recent literature also focuses on plaque assessment and identification of plaques that are likely to give rise to an acute coronary syndrome. There is an explosion of literature on the merits and limitations of the different imaging modalities. This review article will provide an overview of all the imaging modalities in the diagnosis of coronary artery disease.

Assessment of coronary heart disease by CT angiography: current and evolving applications

Computed tomography angiography (CTA) of the heart is a rapidly evolving application for comprehensive assessment of coronary arterial anatomy, myocardial function, perfusion, and myocardial viability. Thus, cardiac CTA is capable of retrieving the most critical information for guiding the management of patients with suspected coronary heart disease (CHD). Ongoing technologic advancements have allowed acquiring such information within minutes, at radiation doses that are lower than those from conventional computed tomography imaging or common nuclear imaging techniques. Cardiac CTA has positioned itself as an imaging modality that may be well suited to fulfill central needs of cardiovascular medicine. This article reviews the evidence for the clinical utility of cardiac CTA in patients with suspected CHD.

Plaque imaging with CT coronary angiography: Effect of intra-vascular attenuation on plaque type classification

AIM: To assess the attenuation of non-calcified atherosclerotic coronary artery plaques with computed tomography coronary angiography (CTCA).

METHODS: Four hundred consecutive patients underwent CTCA (Group 1: 200 patients, Sensation 64 Cardiac, Siemens; Group 2: 200 patients, VCT GE Healthcare, with either Iomeprol 400 or Iodixanol 320, respectively) for suspected coronary artery disease (CAD). CTCA was performed using standard protocols. Image quality (score 0-3), plaque (within the accessible non-calcified component of each non-calcified/mixed plaque) and coronary lumen attenuation were measured. Data were compared on a per-segment/per-plaque basis. Plaques were classified as fibrous vs lipid rich based on different attenuation thresholds. A P < 0.05 was considered significant.

RESULTS: In 468 atherosclerotic plaques in Group 1 and 644 in Group 2, average image quality was 2.96 ± 0.19 in Group 1 and 2.93 ± 0.25 in Group 2 (P≥ 0.05). Coronary lumen attenuation was 367 ± 85 Hounsfield units (HU) in Group 1 and 327 ± 73 HU in Group 2 (P < 0.05); non-calcified plaque attenuation was 48 ± 23 HU in Group 1 and 39 ± 21 HU in Group 2 (P < 0.05). Overall signal to noise ratio was 15.6 ± 4.7 in Group 1 and 21.2 ± 7.7 in Group 2 (P < 0.01).

CONCLUSION: Higher intra-vascular attenuation modifies significantly the attenuation of non-calcified coronary plaques. This results in a more difficult characterization between lipid rich vs fibrous type.

Coronary CT angiography in Takayasu arteritis

OBJECTIVES

The aim of this study was to use coronary computed tomographic (CT) angiography to characterize coronary artery involvement in patients with known Takayasu arteritis who present with anginal chest pain or shortness of breath.

BACKGROUND

Takayasu arteritis is a primary vasculitis of the large vessels, which mainly affects the aorta and its branches but can also involve the coronary arteries. Coronary CT angiography allows visualization of the coronary vessels and can be used to detect both stenotic and nonstenotic coronary artery lesions.

METHODS

Eighteen consecutive patients with Takayasu arteritis and angina (typical or atypical) and/or dyspnea underwent contrast-enhanced 64-slice coronary CT angiography. The arterial injury was classified according to the Numano classification. Three patients had prior known coronary artery disease. Coronary arteries were evaluated concerning the presence of obstructive and nonobstructive lesions, and differences between the clinical presentations of patients with and without coronary artery involvement on CT angiography were analyzed.

RESULTS

Coronary artery involvement was found in 8 patients (44.4%), 3 of them with clinical activity. A total of 19 coronary lesions were present (13 in ostial locations, 5 in proximal coronary artery segments, and 1 in a mid segment). Eight lesions exceeded 50% diameter reduction (2 in ostial locations and 6 in proximal coronary artery segments). Median disease duration was significantly different between patients with coronary artery involvement (176 months; range 13 to 282 months) compared with those without (21 months; range 1 to 142 months) (p = 0.013).

CONCLUSIONS

Coronary CT angiography allows the assessment of coronary artery involvement in patients with Takayasu arteritis. These data confirm prior observations that most coronary lesions are in ostial or proximal coronary artery locations. Disease duration in patients with coronary artery involvement is longer than in patients without.

Evaluation of coronary allograft vasculopathy using multi-detector row computed tomography: a systematic review

Coronary allograft vasculopathy (CAV) is a significant cause of morbidity and mortality after cardiac transplantation and requires frequent surveillance with catheter-based coronary angiography (CCA). Multi-detector row computed tomography (MDCT) has been shown to be effective in assessing atherosclerosis in native coronary arteries. This article systematically reviews the literature to determine the accuracy of MDCT in CAV assessment. An English-language literature search was performed using EMBASE, OVID, PubMed, and Cochrane Library databases. Studies that directly compared MDCT with CCA and/or IVUS for the detection of coronary artery stenosis or significant intimal thickening in cardiac transplant patients were analyzed. Data were pooled to obtain weighted sensitivities, specificities, and diagnostic accuracies. Negative and positive predictive values (NPV/PPV) were calculated. A total of seven studies with a sum of 272 patients were included in this review. There were three studies examining 16-slice MDCT and four studies looking at 64-slice MDCT in CAV. Using per-segment analysis, MDCT assessed between 91% and 96% of all coronary segments when evaluating for stenosis. Pooled estimates for sensitivity and specificity for MDCT ranged from 82% to 89% and 89% to 99%, respectively, while NPV was 99%. Per-patient analysis revealed a sensitivity of 87-100% and NPV of 96-100%. PPV was less than 50% for 64-slice MDCT in both per-segment and per-patient analysis. When compared with IVUS, MDCT had a sensitivity of 74-96% and specificity of 88-92% in assessment of intimal thickening. NPV and PPV were 80-81% and 84-98%, respectively. The high sensitivity and NPV of MDCT suggest that it may be a useful, noninvasive screening tool to rule out CAV.

Classification of noncalcified coronary atherosclerotic plaque components on CT coronary angiography: impact of vascular attenuation and density thresholds

PURPOSE

The authors assessed the effect of vascular attenuation and density thresholds on the classification of noncalcified plaque by computed tomography coronary angiography (CTCA).

MATERIALS AND METHODS

Thirty patients (men 25; age 59 ± 8 years) with stable angina underwent arterial and delayed CTCA. At sites of atherosclerotic plaque, attenuation values (HU) were measured within the coronary lumen, noncalcified and calcified plaque material and the surrounding epicardial fat. Based on the measured CT attenuation values, coronary plaques were classified as lipid rich (attenuation value below the threshold) or fibrous (attenuation value above the threshold) using 30-HU, 50-HU and 70-HU density thresholds.

RESULTS

One hundred and sixty-seven plaques (117 mixed and 50 noncalcified) were detected and assessed. The attenuation values of mixed plaques were higher than those of exclusively noncalcified plaques in both the arterial (148.3 ± 73.1 HU vs. 106.2 ± 57.9 HU) and delayed (111.4 ± 50.5 HU vs. 64.4 ± 43.4 HU) phases (p<0.01). Using a 50-HU threshold, 12 (7.2%) plaques would be classified as lipid rich on arterial scan compared with 28 (17%) on the delayed-phase scan. Reclassification of these 16 (9.6%) plaques from fibrous to lipid rich involved 4/30 (13%) patients.

CONCLUSIONS

Classification of coronary plaques as lipid rich or fibrous based on absolute CT attenuation values is significantly affected by vascular attenuation and density thresholds used for the definition.

Cardiac CT: practical approach to integrate appropriate indications in daily practice

Recent advances in CT technologies had significantly improved the clinical utility of cardiac CT. Major efforts have been made to optimize the image quality, standardize protocols and limit the radiation exposure. Rapid progress in post-processing tools dedicated not only to the coronary artery assessment but also to the cardiac cavities, valves and veins extended applications of cardiac CT. This potential might be however used optimally considering the current appropriate indications for use as well as the current technical imitations. Coronary artery disease and related ischemic cardiomyopathy remain the major applications of cardiac CT and at the same time the most complex one. Integration of a specific knowledge is mandatory for optimal use in this area for asymptomatic as for symptomatic patients, with a specific regards to patient with acute chest pain. This review aimed to propose a practical approach to implement appropriate indications in our routine practice. Emerging indications and future direction are also discussed. Adequate preparation of the patient, training of physicians, and the multidisciplinary interaction between actors are the key of successful implementation of cardiac CT in daily practice.

Computed tomography-coronary angiography in the detection of coronary artery disease

Computed tomography-coronary angiography (CT-CA) is a well-tolerated and reliable non-invasive imaging technique and can now be achieved at low levels of radiation exposure. CT-CA is highly valuable to exclude coronary artery disease, but due to over- and underestimation of the severity of coronary lesions, CT-CA cannot replace invasive coronary angiography. Coronary calcium scoring has an incremental independent prognostic value beyond traditional risk factor scores (Framingham, European Score) and may be useful to reclassify risk in asymptomatic individuals at intermediate risk. Appropriate indications for CT-CA are evolving, but studies are lacking to demonstrate that CT coronary imaging improves patient outcome.

Cardiac hybrid imaging

Computed tomography coronary angiography (CTCA) and myocardial perfusion imaging techniques (single photon emission computed tomography, SPECT, or positron emission tomography, PET) are established non-invasive modalities for the diagnosis of coronary artery disease (CAD). Cardiac hybrid imaging consists of the combination (or 'fusion') of both modalities and allows obtaining complementary morphological (coronary anatomy, stenoses) and functional (myocardial perfusion) information in a single setting. However, hybrid cardiac imaging has also generated controversy with regard to which patients should undergo such integrated examinations for clinical effectiveness and minimization of costs and radiation dose. The feasibility and clinical value of hybrid imaging has been documented in small cohort studies and selected series of patients. Hybrid imaging appears to offer superior diagnostic and prognostic information compared with stand-alone or side-by-side interpretation of data sets. Particularly in patients with multivessel disease, the hybrid approach allows identification of flow-limiting coronary lesions and thereby provides useful information for the planning of revascularization procedures. Furthermore, integration of the detailed anatomical information from CTCA with the high molecular sensitivity of SPECT and PET may be useful to evaluate targeted molecular and cellular abnormalities in the future. While currently still restricted to specialized cardiac centres, the ongoing efforts to reduce radiation exposure and the increasing clinical interest will further pave the way for an increasing use of cardiac hybrid imaging in clinical practice.

Focus on the research utility of intravascular ultrasound - comparison with other invasive modalities

Intravascular ultrasound (IVUS) is an invasive modality which provides cross-sectional images of a coronary artery. In these images both the lumen and outer vessel wall can be identified and accurate estimations of their dimensions and of the plaque burden can be obtained. In addition, further processing of the IVUS backscatter signal helps in the characterization of the type of the plaque and thus it has been used to study the natural history of the atherosclerotic evolution. On the other hand its indigenous limitations do not allow IVUS to assess accurately stent struts coverage, existence of thrombus or exact site of plaque rupture and to identify some of the features associated with increased plaque vulnerability. In order this information to be obtained, other modalities such as optical coherence tomography, angioscopy, near infrared spectroscopy and intravascular magnetic resonance imaging have either been utilized or are under evaluation. The aim of this review article is to present the current utilities of IVUS in research and to discuss its advantages and disadvantages over the other imaging techniques.

Clinical perspective of coronary computed tomographic angiography in diagnosis of coronary artery disease

Since a 4-detector row coronary computed tomographic angiography (CCTA) was launched in 1998, CCTA has experienced rapid improvement of imaging qualities with the ongoing evolution of computed tomography (CT) technology. The diagnostic accuracy of CCTA to detect coronary artery stenosis is well established, whereas improvements are still needed to reduce the overestimation of coronary artery disease (CAD) and assess plaque composition. CCTA has been used to evaluate CAD in various clinical settings. For example, CCTA could be an efficient initial triage tool at emergency departments for patients with acute chest pain with low-to-intermediate risk because of its high negative predictive value. In patients with suspected CAD, CCTA could be a cost-effective alternative to myocardial perfusion imaging and exercise electrocardiogram for the initial coronary evaluation of patients with intermediate pre-test likelihood suspected CAD. However, in asymptomatic populations, there is a lack of studies that show an improved prognostic power of CCTA over other modalities. Therefore, the clinical use of CCTA to detect CAD for purposes of risk stratification in asymptomatic individuals should be discouraged. As CT technology evolves, CCTA will provide better quality coronary imaging and non-coronary information with lower radiation exposure. Future studies should cover these ongoing technical improvements and evaluate the prognostic power of CCTA in various clinical settings of CAD in large, well-designed, randomized trials.

Comparison of Plaque Composition in Diabetic and Non-Diabetic Patients With Coronary Artery Disease Using Multislice CT Angiography

BACKGROUND AND OBJECTIVES

Plaque composition rather than degree of luminal narrowing may be predictive of future coronary events in high risk patients. The purpose of this study was to compare degree of plaque burden and composition with multislice computed tomography (MSCT) angiography between diabetic and non-diabetic patients.

SUBJECTS AND METHODS

A total of 452 consecutive MSCT angiography examinations were performed between July 2007 and June 2009. Of these, the patients who underwent invasive coronary angiography were evaluated for the presence and type of atherosclerotic plaque and severity of luminal narrowing.

RESULTS

Ninety two (46 in the diabetic group and 46 in the non-diabetic group) patients underwent both MSCT angiography and invasive coronary angiography. Among them, 30 patients (65.2%) in the diabetic group and 26 patients (56.5%) in the non-diabetic group had significant coronary narrowing on MSCT angiography. Sixteen patients (34.8%) in the diabetic group and 15 patients (32.6%) in non-diabetic group underwent coronary angioplasty and stenting. Forty-two patients (93.3%) in the diabetic group and 39 patients (88.6%) in the non-diabetic group had multiple types of coronary plaque (p=0.485). MSCT angiography was similar to conventional coronary angiography in its ability to predict significant coronary artery disease in that the area under the curve was 0.88 (95% confidence interval, 0.81 to 0.95). Diabetic patients had more mixed plaque compared with non-diabetic patients.

CONCLUSION

Differences in coronary plaque composition between diabetic and non-diabetic patients can be determined noninvasively by MSCT angiography. In patients with diabetes, mixed plaque types contribute to the total plaque burden to a higher degree than in non-diabetic patients.

Imaging of coronary atherosclerosis by computed tomography

Modern computed tomography (CT) systems afford sufficient spatial and temporal resolution for imaging of the heart and coronary arteries. The detection of coronary artery calcium (CAC) is relatively straightforward and it is applied to detect and quantify subclinical coronary atherosclerosis even in asymptomatic individuals. A large body of evidence has accumulated that uniformly attests to a high predictive value of CAC for future cardiac events. More complex data acquisition protocols, which require higher spatial and temporal resolution, specific patient preparation, and the intravenous injection of contrast agent, allow to perform coronary CT angiography (CTA). With CTA, the presence of luminal stenoses and, given sufficient image quality, calcified as well as non-calcified atherosclerotic plaque can be visualized. Initial studies have shown that certain plaque characteristics, such as positive remodelling or very low CT attenuation, are associated with plaque vulnerability. So far, the available clinical data are not sufficient to draw specific conclusions as to the risk-benefit ratio of contrast-enhanced coronary CTA for risk prediction, especially for asymptomatic individuals. Hence, CTA is currently not recommended for risk stratification purposes. However, the technology of coronary CTA continues to evolve at a rapid pace and clinical applications for plaque imaging and characterization may become possible in the future.

Missense mutations resulting in type 1 lissencephaly

Proper human brain formation is dependent upon the integrated activity of multiple genes. Malfunctioning of key proteins results in brain developmental abnormalities. Mutation(s) in the LIS1 gene or the X-linked gene doublecortin (DCX) results in a spectrum of disorders including lissencephaly, or "smooth brain", and subcortical band heterotopia, or "doublecortex". Here, we will focus on a particular subset of missense mutations in these two genes and their effect on protein structure and function.