Multimodality imaging in coronary artery disease – “The more the better?”

Multimodality imaging in coronary artery disease (CAD) comprises a combination of information from more than one imaging technique. These combinations, performed in a side-by-side or fusion mode, include computed tomography (CT) and single photon emission computed tomography (SPECT), positron emission tomography (PET) and CT, and PET with magnetic resonance imaging (MRI). Data thus obtained lead to either a summative or synergistic gain of information. For instance, morphology (coronary plaques/stenosis) can be depicted by coronary CT angiography, whereas functional aspects of CAD such as myocardial perfusion abnormalities or myocardial metabolism can be evaluated by the complementary technique in order to separate a hemodynamic significant coronary stenosis from a hemodynamic non-significant stenosis. Distinguishing these two entities has an important impact on patient management. Beyond the diagnostic yield, some of these combinations in multimodality imaging also have prognostic implications. In this article, we will describe different multimodality imaging approaches (CT/SPECT, PET/CT and PET/MRI) for evaluation of CAD in patients with suspected or known CAD and put them into the context of current knowledge.     

Cardiac PET-CT

Integrated positron emission tomography computed tomography (PET/CT) scanners allow a true integration of the structure and function of the heart. Myocardial perfusion PET provides a high sensitivity (91%) and specificity (89%) for the diagnosis of obstructive coronary artery disease (CAD). But, as with single photon emission CT, relative perfusion PET often uncovers only the territory subtended by the most severe coronary stenosis, leading to underestimation of the extent of CAD. In contrast, quantitative PET provides a noninvasive assessment of myocardial blood flow and coronary flow reserve and improves detection of preclinical and multivessel coronary atherosclerosis. Similarly, CT coronary angiography is an accurate means to image the entire continuum of anatomic coronary atherosclerosis from nonobstructive to obstructive CAD. However, not all coronary stenoses are hemodynamically significant and <50% of the patients with obstructive CAD on CT angiography demonstrate stress induced perfusion defects. Stress PET data complement the anatomic information on the CT angiogram by providing instant readings about the ischemic burden of coronary stenoses. Thus, combined PET/CT may be potentially superior to CT angiography alone for the guiding revascularization decisions. Further, fusion of the PET and CT angiogram images allows identification of the culprit stenosis in patients presenting with chest pain. Finally, the advances in molecular imaging and image fusion may soon make noninvasive detection of vulnerable coronary plaques a clinical reality. In summary, integrated PET/CT is a powerful new noninvasive modality that offers the potential for refined diagnosis and management of the entire spectrum of coronary atherosclerosis.     

Prognostic value of coronary CT angiography

Coronary computed tomography angiography (CTA) is a highly accurate noninvasive test that is increasingly used in symptomatic patients primarily for the diagnosis of coronary artery disease (CAD). Beyond its proven accuracy, data have now clearly demonstrated the incremental prognostic information available from coronary CTA related to the presence, extent, and severity of obstructive and nonobstructive CAD across a variety of clinical settings and patient populations. Current evidence supports the use of coronary CTA not only for the diagnosis of CAD in appropriately selected symptomatic patients but also to further refine their cardiovascular risk assessment following testing.     

CT Perfusion: Ready for Prime Time

Advancements in computed tomography (CT) technology have revolutionized clinical practice, particularly regarding the noninvasive assessment of coronary artery disease (CAD). The versatility of cardiac CT has rendered multiple applications including assessment of cardiac structure and function, myocardial viability, and coronary anatomy. The merits of cardiac computed tomography angiography (CTA) have been proven for the detection, and particularly the exclusion, of CAD. However, CTA becomes limited in the presence of significant CAD. Its inability to consistently identify lesion-associated ischemia may necessitate additional radionuclide myocardial perfusion imaging. Myocardial computed tomography perfusion imaging (CTP) has emerged as a useful and convenient method to immediately assess myocardial ischemia. In this review, we discuss the current state of CTP including available technology, its performance to date from current literature, and future challenges to this field.     

Diagnostic Performance of Hybrid Cardiac Imaging Methods for Assessment of Obstructive Coronary Artery Disease Compared With Stand-Alone Coronary Computed Tomography Angiography: A Meta-Analysis

Objectives

The current meta-analysis aimed to evaluate the diagnostic performance of hybrid cardiac imaging techniques compared with stand-alone coronary computed tomography angiography (CTA) for assessment of obstructive coronary artery disease (CAD).

Computed Fractional Flow Reserve (FFTCT) Derived from Coronary CT Angiography

Recent advances in image-based modeling and computational fluid dynamics permit the calculation of coronary artery pressure and flow from typically acquired coronary computed tomography (CT) scans. Computed fractional flow reserve is the ratio of mean coronary artery pressure divided by mean aortic pressure under conditions of simulated maximal coronary hyperemia, thus providing a noninvasive estimate of fractional flow reserve (FFR_CT) at every point in the coronary tree. Prospective multicenter clinical trials have shown that computed FFR_CT improves diagnostic accuracy and discrimination compared to CT stenosis alone for the diagnosis of hemodynamically significant coronary artery disease (CAD), when compared to invasive FFR as the reference gold standard. This promising new technology provides a combined anatomic and physiologic assessment of CAD in a single noninvasive test that can help select patients for invasive angiography and revascularization or best medical therapy. Further evaluation of the clinical effectiveness and economic implications of noninvasive FFR_CT are now being explored.     

Comparison of Coronary Computed Tomography Angiography,Fractional Flow Reserve,and Perfusion Imaging for Ischemia Diagnosis

Background

Fractional flow reserve (FFR) computation from coronary computed tomography angiography (CTA) datasets (FFR_CT) has emerged as a promising noninvasive test to assess hemodynamic severity of coronary artery disease (CAD), but has not yet been compared with traditional functional imaging.

Multi-slice computed tomography coronary angiography: anatomic vs functional assessment in clinical practice.

Non-invasive imaging plays an increasingly important role in the diagnosis and risk stratification of coronary artery disease (CAD). Several techniques such as stress echocardiography and myocardial perfusion imaging have become available to assess cardiac function and myocardial perfusion. With the arrival of multi-slice computed tomography coronary angiography (CTA), non-invasive imaging of coronary anatomy has also become possible. Studies concerning the diagnostic accuracy have demonstrated a good agreement with conventional coronary angiography resulting in a sensitivity and specificity of approximately 86% and 96%, respectively. The high negative predictive value of 97% renders it particularly useful to rule out the presence of CAD in patients with an intermediate pretest likelihood. Moreover, comparative studies have demonstrated that anatomic imaging with CTA may provide information complementary to the traditionally used techniques for functional assessment. From these studies can be derived that only approximately 50% of significant stenoses on CTA are functionally relevant; a large proportion of significant (>50%) lesions on CTA does not result in perfusion abnormalities. Alternatively, many patients with a normal perfusion CTA show considerable atherosclerosis on CTA. Therefore, the combined use of these techniques may enhance the assessment of the presence and extent of CAD. In the future diagnostic algorithms, combining non-invasive anatomic and functional imaging need to be evaluated in large patient populations to establish their efficacy, safety, and cost effectiveness. Importantly, these investigations should result in the development of comprehensive guidelines on the use of CTA in clinical practice as well.     

16排CT在评价胸痛患者冠状动脉病变中的应用价值

目的：探讨16排计算机断层扫描技术(CT)在评价胸痛疑似冠心病患者冠状动脉病变中的应用价值。方法：52例胸痛疑似冠心病患者人选,分别用16排CT造影方法(CTA)和常规冠状动脉造影方法(CAG)评价冠状动脉病变情况,并以CAG为标准计算CTA诊断冠状动脉病变的敏感度、特异度、阳性预测值(PPV)和阴性预测值(NPV)。结果：CTA能评价所有627个冠状动脉节段中的546个(87%)。在该546个冠状动脉节段中,CTA诊断冠状动脉病变的敏感度、特异度、PPV和NPV分别是94%、95%、82%和99%;CTA对冠状动脉左主干及其近中段病变的敏感度、特异度、PPV和NPV均高于冠状动脉远段和分支血管。结论：CTA能较准确地评价胸痛疑似冠心病患者冠状动脉(尤其是近、中段)的病变情况。     

PET/CT在胰腺癌临床应用中的进展

胰腺癌是一类发病率高、早期诊断困难、治疗疗效不佳的消化系统恶性肿瘤.PET/CT作为现代医学成像重要组成内容之一,将PET的功能显像与CT的解剖成像有机融合,不仅能有效显示肿瘤的代谢、增生、乏氧和细胞凋亡状态,而且能精确显示肿瘤与其周围脏器组织的解剖结构.在胰腺癌患者的诊疗指导、肿瘤分期、疗效监控和预后评价等方面,PET/CT都具有重要的临床应用价值.本文将简要介绍PET/CT在胰腺癌临床应用中的进展情况.     

Merits of FDG PET/CT and Functional Molecular Imaging Over Anatomic Imaging With Echocardiography and CT Angiography for the Diagnosis of Cardiac Device Infections

The diagnosis of cardiac device infections, particularly device-related endocarditis, is challenging. Fluorine-18-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) is based on in vivo FDG targeting of the pre-existing inflammatory cells at an infectious site. Hence, it is able to identify cardiac device infection early, before the development of morphological damages from the infectious process. Transesophageal echocardiography (TEE) and electrocardiographically gated computed tomographic angiography (CTA) are currently the first-line imaging studies for device-related endocarditis, but their application to evaluate the extracardiac components or sources of primary infection and/or emboli is limited. Functional FDG PET/CT may have unique advantages over the anatomically based TEE and CT or CTA in the following settings: 1) diagnosing infection earlier than TEE and CTA, before morphological damage ensues; 2) identifying prosthetic endocarditis when findings on TEE and CTA are inconclusive; 3) evaluating infection in the extracardiac components of devices; 4) detecting unexpected source of the primary infection; and 5) discovering embolic consequences of endocarditis in the body. All of these findings may ultimately affect patient management. Although the nonspecific nature of FDG is a concern in differentiating infection from inflammation, accurate diagnosis of infection can be reasonably achieved on the basis of FDG distribution pattern and clinical history or by adding radiolabeled white blood cell scan to improve specificity. Recent publications support the judicious use of FDG PET/CT, particularly in patients with inconclusive or negative results on initial echocardiography and CT.     

Relationship between CT coronary angiography and stress perfusion imaging in patients with suspected ischemic heart disease assessed by integrated PET-CT imaging.

BACKGROUND: Although computed tomography (CT) coronary angiography (CTA) provides detailed assessments of the anatomic extent of coronary artery disease (CAD), its value for predicting myocardial ischemia is unclear. We examined the value of CTA to identify the presence of ischemia, as determined by stress perfusion imaging, using integrated positron emission tomography (PET)-CT imaging. METHODS AND RESULTS: We studied 110 consecutive patients (median age, 57 years; 55% male) with suspected CAD undergoing stress rubidium 82 myocardial perfusion PET imaging and CTA in the same setting. Increasing degrees of CTA-detected luminal narrowing (<50%, 50%-70%, and >70%) were associated with reduced sensitivity with commensurate improvements in specificity for identifying myocardial ischemia both on a per-vessel basis and on a per-patient basis. Consequently, with increasing degrees of CTA-detected stenosis severity, the positive predictive value increased (14%, 26%, and 53%, respectively, on a per-vessel basis [P < .001] and 29%, 44%, and 77%, respectively, on a per-patient basis [P = .005]), whereas the negative predictive value was unchanged (97%, 97%, and 96%, respectively, on a per-vessel basis [P = not significant (NS)] and 92%, 91%, and 88%, respectively, on a per-patient basis [P = NS]). Receiver operating characteristic analysis revealed no differences between these 3 anatomic criteria (receiver operating characteristic areas of 0.66 +/- 0.07, 0.73 +/- 0.06, and 0.71 +/- 0.07, respectively [P = NS]) for identifying ischemia. Nearly half of significant angiographic stenoses (47%) occurred without evidence of myocardial ischemia, whereas 50% of normal PET studies were associated with some CTA abnormality. CONCLUSIONS: Despite an excellent negative predictive value, CTA is a poor discriminator of patients with myocardial ischemia. Conversely, a normal stress PET study is a poor discriminator of patients without evidence of non-flow-limiting (subclinical) coronary atherosclerosis. These results suggest potentially complementary roles of CT and perfusion imaging in the evaluation of patients with suspected CAD.     

Incremental Diagnostic Value of Stress Computed Tomography Myocardial Perfusion With Whole-Heart Coverage CT Scanner in Intermediate- to High-Risk Symptomatic Patients Suspected of Coronary Artery Disease

Objectives

The goal of this study was to evaluate the diagnostic accuracy of stress computed tomography myocardial perfusion (CTP) for the detection of functionally significant coronary artery disease (CAD) by using invasive coronary angiography (ICA) plus invasive fractional flow reserve (FFR) as the reference standard in consecutive intermediate- to high-risk symptomatic patients.

Diagnosis and evaluation of gastric cancer by positron emission tomography

Gastric cancer is the second leading cause of cancer mortality worldwide.The diagnosis of gastric cancer has been significantly improved with the broad availability of gastrointestinal endoscopy.Effective technologies for accurate staging and quantitative evaluation are still in demand to merit reasonable treatment and better prognosis for the patients presented with advanced disease.Preoperative staging using conventional imaging tools,such as computed tomography(CT)and endoscopic ultrasonography,is inadequate.Positron emission tomography(PET),using 18F-fluorodeoxyglucose(FDG)as a tracer and integrating CT for anatomic localization,holds a promise to detect unsuspected metastasis and has been extensively used in a variety of malignancies.However,the value of FDG PET/CT in diagnosis and evaluation of gastric cancer is still controversial.This article reviews the current literature in diagnosis,staging,response evaluation,and relapse monitoring of gastric cancer,and discusses the current understanding,improvement,and future prospects in this area.     

Utility of PET/CT in diagnosis,staging, assessment of resectability and metabolic response of pancreatic cancer

Pancreatic cancer is one of the most common gastrointestinal tumors, with its incidence staying at a high level in both the United States and China. However, the overall 5-year survival rate of pancreatic cancer is still extremely low. Surgery remains the only potential chance for long-term survival. Early diagnosis and precise staging are crucial to make proper clinical decision for surgery candidates. Despite advances in diagnostic technology such as computed tomography (CT) and endoscopic ultrasound, diagnosis, staging and monitoring of the metabolic response remain a challenge for this devastating disease. Positron emission tomography/CT (PET/CT), a relatively novel modality, combines metabolic detection with anatomic information. It has been widely used in oncology and achieves good results in breast cancer, lung cancer and lymphoma. Its utilization in pancreatic cancer has also been widely accepted. However, the value of PET/CT in pancreatic disease is still controversial. Will PET/CT change the treatment strategy for potential surgery candidates? What kind of patients benefits most from this exam? In this review, we focus on the utility of PET/CT in diagnosis, staging, and assessment of resectability of pancreatic cancer. In addition, its ability to monitor metabolic response and recurrence after treatment will be emphasis of discussion. We hope to provide answers to the questions above, which clinicians care most about.     

Planning percutaneous coronary interventions using computed tomography angiography and fractional flow reserve‐derived from computed tomography: A state‐of‐the‐art review

Fractional flow reserve derived by coronary computed tomography angiography (CTA; FFRCT) is an accurate noninvasive method for identifying coronary artery disease (CAD) and detecting hemodynamically significant stenosis. Although initially proposed as noninvasive tools to “rule out” significant CAD in low‐risk patients, CTA and FFRCT are now utilized in higher‐risk patients. Furthermore, new applications of CTA and FFRCT include a planning tool for percutaneous coronary intervention (PCI), which allows the cardiologist to assess lesion‐specific ischemia, plan stent locations and sizes, and use virtual remodeling of the lumen (virtual stenting) to assess the functional impact of PCI. The purpose of this review is to discuss the principles of CTA and FFRCT acquisition, and their application for PCI planning, even before invasive angiography is performed.     

Fractal Analysis of Dynamic Stress CT-Perfusion Imaging for Detection of Hemodynamically Relevant Coronary Artery Disease

BackgroundCombined computed tomography–derived myocardial blood flow (CTP-MBF) and computed tomography angiography (CTA) has shown good diagnostic performance for detection of coronary artery disease (CAD). However, fractal analysis might provide additional insight into ischemia pathophysiology by characterizing multiscale perfusion patterns and, therefore, may be useful in diagnosing hemodynamically significant CAD.ObjectivesThe purpose of this study was to investigate, in a multicenter setting, whether fractal analysis of perfusion improves detection of hemodynamically relevant CAD over myocardial blood flow quantification (CTP-MBF) using dynamic, 4-dimensional, dynamic stress myocardial computed tomography perfusion (CTP) imaging.MethodsIn total, 7 centers participating in the prospective AMPLIFiED (Assessment of Myocardial Perfusion Linked to Infarction and Fibrosis Explored with Dual-source CT) study acquired CTP and CTA data in patients with suspected or known CAD. Hemodynamically relevant CAD was defined as ≥90% stenosis on invasive coronary angiography or fractional flow reserve <0.80. Both fractal analysis and CTP-MBF quantification were performed on CTP images and were combined with CTA results.ResultsThis study population included 127 participants, among them 61 patients, or 79 vessels, with CAD as per invasive reference standard. Compared with the combination of CTP-MBF and CTA, combined fractal analysis and CTA improved sensitivity on the per-patient level from 84% (95% CI: 72%-92%) to 95% (95% CI: 86%-99%; P = 0.01) and specificity from 70% (95% CI: 57%-82%) to 89% (95% CI: 78%-96%; P = 0.02). The area under the receiver-operating characteristic curve improved from 0.83 (95% CI: 0.75-0.90) to 0.92 (95% CI: 0.86-0.98; P = 0.01).ConclusionsFractal analysis constitutes a quantitative and pathophysiologically meaningful approach to myocardial perfusion analysis using dynamic stress CTP, which improved diagnostic performance over CTP-MBF when combined with anatomical information from CTA.     

Diagnosis of coronary artery disease in patients with permanent cardiac pacemaker by dobutamine stress echocardiography or exercise thallium-201 myocardial tomography

This study evaluated the use of dobutamine stress echocardiography and exercise thallium-201 myocardial computed tomography (CT) in the diagnosis of coronary artery disease (CAD) in patients with permanent transvenous pacemaker with the electrode implanted in the right ventricle (RV). Twenty-nine consecutive patients with pacemaker underwent dobutamine stress echocardiography, exercise thallium-201 myocardial CT, and coronary arteriography over a period of 8 +/- 1 days. None of these patients had suffered a myocardial infarction (MI). The cardiac rhythm of every patient was electrically paced during echocardiography and tomography. Sixteen (55%) patients showed CAD on angiography (stenosis > or = 50% of the luminal diameter of a major epicardial vessel). The detection sensitivity for CAD was 94% for the tomography and 88% for the echocardiography (P = NS). The difference between the sensitivities of the two techniques in detecting CAD based on the affected coronary artery was not statistically significant. Of the 13 patients without CAD, tomography showed a positive result in nine cases, i.e., a specificity of 31%, whereas echocardiography showed a positive result in only one case, i.e., a specificity of 92% (P < 0. 01). Exercise thallium-201 myocardial computed tomography produces an increased rate of false-positive results in patients with permanent transvenous cardiac pacemaker (PCP) implanted in the right ventricle (RV). Dobutamine stress echocardiography can thus be used to reduce considerably the level of false-positive results in these patients and still retain a detection sensitivity for CAD equal to that of myocardial tomography.     

Molecular imaging of plaques in coronary arteries with PET and SPECT

Coronary artery disease remains a major cause of mortality. Presence of atherosclerotic plaques in the coronary artery is responsible for lu-men stenosis which is often used as an indicator for determining the severity of coronary artery disease. However, the degree of coronary lumen stenosis is not often related to compromising myocardial blood flow, as most of the cardiac events that are caused by atherosclerotic plaques are the result of vulnerable plaques which are prone to rupture. Thus, identification of vulnerable plaques in coronary arteries has become increas-ingly important to assist identify patients with high cardiovascular risks. Molecular imaging with use of positron emission tomography （PET） and single photon emission computed tomography （SPECT） has fulfilled this goal by providing functional information about plaque activity which enables accurate assessment of plaque stability. This review article provides an overview of diagnostic applications of molecular imaging tech-niques in the detection of plaques in coronary arteries with PET and SPECT. New radiopharmaceuticals used in the molecular imaging of coro-nary plaques and diagnostic applications of integrated PET/CT and PET/MRI in coronary plaques are also discussed.     

Diagnostic value of 18F-FDG PET in the assessment of myocardial viability in coronary artery disease: A comparative study with 99mTc SPECT and echocardiography

ObjectiveTo investigate the diagnostic value of 18F-fluorodeoxyglucose positron emission tomography （18F-FDG PET） in the as-sessment of myocardial viability in patients with known coronary artery disease （CAD） when compared to99mTc single photon emission computed tomography （SPECT） and echocardiography, with invasive coronary angiography as the gold standard.MethodsThirty patients with diagnosed CAD met the selection criteria, with 10 of them （9 men, mean age 59.5 ± 10.5 years） undergoing all of these imaging proce-dures consisting of SPECT and PET, echocardiography and invasive angiography. Diagnostic sensitivity of these less invasive modalities for detection of myocardial viability was compared to invasive coronary angiography. Inter- and intra-observer agreement was assessed for di-agnostic performance of SPECT and PET.ResultsOf all patients with proven CAD, 50% had triple vessel disease. Diagnostic sensitivity of SPECT, PET and echocardiography was 90%, 100% and 80% at patient-based assessment, respectively. Excellent agreement was achieved between inter-observer and intra-observer agreement of the diagnostic value of SPECT and PET in myocardial viability （k= 0.9）. Conclusion18F-FDG PET has high diagnostic value in the assessment of myocardial viability in patients with known CAD when com-pared to SPECT and echocardiography. Further studies based on a large cohort with incorporation of18F-FDG PET into patient management are warranted.