CV Imaging Process Research Paper

CV Imaging Process Research Paper

The increasing speed and magnitude of change in health care provide both challenges and opportunities. To successfully navigate the future, it is essential to anticipate difficulties and design strategic solutions. This is as true for cardiac imaging as it is for the rest of cardiac medicine. Dramatic changes have already occurred in imaging, including the introduction of promising new technologies such as coronary computed tomography (CT) angiography and substantial reductions in reimbursement driven by cost cutting and concerns regarding overuse. The cardiology imaging community has responded with an array of approaches, including the convening of think tanks to define and address imaging quality 1, 2, radiation safety (3), and other relevant topics; the design and implementation of appropriate use criteria (4); the codification of methods for the creation of technology quality metrics (5); the creation of increasingly robust accreditation standards, such as those from the Intersocietal Accreditation Commission; and the performance of large, outcomes-driven randomized controlled trials 6, 7. Additionally, individual societies have issued an array of guidelines and standards documents and have created certification examinations to document competency 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18.CV Imaging Process Research Paper

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Our system-wide imaging facilities at University of Minnesota Health occupy 22,000 square feet and offer access to state-of-the-art MR, CT and PET scanners. The Advanced Cardiovascular Imaging Fellow will train at the Cardiovascular MRI (CMR) and Cardiovascular CT (CCT) Programs at the University of Minnesota Medical Center. These programs are collaborative efforts between the Department of Radiology and the Cardiovascular Division of the Department of Medicine with leadership and administration by the Cardiovascular Division. The CMR Program includes a state-of-the-art Siemens 1.5T Aera MRI scanner dedicated solely to cardiovascular imaging and the CCT Program includes a dual source Flash CT scanner.

Standard imaging tests include .

Standard CT and MRI have limited application because the heart constantly beats, but faster CT and magnetic resonance techniques can provide useful cardiac images; sometimes patients are given a drug (eg, a beta-blocker) to slow the heart rate during imaging.

In ECG gating, the image recording (or reconstruction) is synchronized with the ECG (ECG gating), providing information from several cardiac cycles that can be used to create single images of selected points in the cardiac cycle.

CT gating uses the ECG to trigger the x-ray beam at the desired portion of the cardiac cycle, exposing the patient to less radiation than gating that simply reconstructs information from only the desired portion of the cardiac cycle (gated reconstruction) and does not interrupt the x-ray beam.

Chest x-rays
Chest X-Ray (Prosthetic Heart Valve)
Chest X-Ray (Prosthetic Heart Valve)
ZEPHYR/SCIENCE PHOTO LIBRARY
Chest x-rays are often useful as a starting point in a cardiac diagnosis. Posteroanterior and lateral views provide a gross view of atrial and ventricular size and shape and pulmonary vasculature, but additional tests are almost always required for precise characterization of cardiac structure and function.

CT
Cardiac CT (3D Scan of Prosthetic Heart Valve)
Cardiac CT (3D Scan of Prosthetic Heart Valve)
ZEPHYR/SCIENCE PHOTO LIBRARY
Spiral (helical) CT may be used to evaluate pericarditis, congenital cardiac disorders (especially abnormal arteriovenous connections), disorders of the great vessels (eg, aortic aneurysm, aortic dissection), cardiac tumors, acute pulmonary embolism, chronic pulmonary thromboembolic disease, and arrhythmogenic right ventricular dysplasia. However, CT requires a radiopaque dye, which may limit its use in patients with renal impairment.CV Imaging Process Research Paper

Cardiac CT Angiogram
Cardiac CT Angiogram
LIVING ART ENTERPRISES, LLC/SCIENCE PHOTO LIBRARY
Cardiac CT (3D Scan of Prosthetic Heart Valve)
Cardiac CT (3D Scan of Prosthetic Heart Valve)
ZEPHYR/SCIENCE PHOTO LIBRARY
Non-Contrast CT Showing Coronary Artery Calcification
Non-Contrast CT Showing Coronary Artery Calcification
© 2017 ELLIOT K. FISHMAN, MD.
Contrast CT Showing Coronary Artery Disease
Contrast CT Showing Coronary Artery Disease
© 2017 ELLIOT K. FISHMAN, MD.
Electron beam CT, formerly called ultrafast CT or cine CT, unlike conventional CT, does not use a moving x-ray source and target. Instead, the direction of the x-ray beam is guided by a magnetic field and detected by an array of stationary detectors. Because mechanical motion is not required, images can be acquired in a fraction of a second (and recorded at a specific point in the cardiac cycle).

Clinical Training
The Advanced Cardiovascular Imaging Fellow will be responsible for supervising, reviewing, interpreting, and reporting all CMR and CCT studies on a daily basis under the close supervision of faculty members. We have among the highest volume CMR and CCT programs in the United States, with studies spanning the entire spectrum of clinical indications. Fellows in this program will interpret over 1000 studies each in CMR and CCT by the end of their training.

Research Training
Mentored research training opportunities are available. The CMR and CCT Programs participate in National Institutes of Health-funded and industry-sponsored studies. The Advanced Cardiovascular Imaging Fellow is expected to participate in research and scholarly activity during their training. Travel to conferences and meetings for presenting research will be supported.CV Imaging Process Research Paper

Eligibility
There is typically one funded Advanced Cardiovascular Imaging Fellowship position. The typical Fellowship training is for one year. To be eligible, applicants must have successfully completed three years of training in an ACGME-accredited Cardiovascular Disease Fellowship. The start date for the fellowship is July 1 each year.

Additional clinical and/or research fellowship positions may also be available to eligible candidates with funding from their own hospital or university, research grants, government or other sources.

What we do
The Cardiovascular Imaging Section’s research is mainly based around cardiovascular magnetic resonance (CMR), nuclear medicine, cardiac CT and echocardiography. Our aims include research to gain a better understanding of cardiac disease so that we can develop appropriate treatments tailored to the needs of individual patients. We investigate and implement prevention strategies in cardiovascular medicine, particularly in conditions such as cardiomyopathy, congenital heart disease, and coronary disease.

Why it is important
We use the different imaging modalities to look at diverse patient problems and each technique has particular research strengths; CMR is good for looking at myocardium and cardiac function, CT for coronary arteries, nuclear medicine for nerves to the heart and echocardiography for the valves. With our research, we help to develop new treatments for patients. The research 3T magnet at Royal Brompton Hospital is a valuable asset allowing us to work in completely novel areas such as the microstructure of the heart with diffusion tensor imaging.

Research impact
Important publications include a new theory to explain myocardial dysfunction in hypertrophic and dilated cardiomyopathy, identifying titin as a cause of ~25% of dilated cardiomyopathy, and identifying fibrosis in the right side of the heart in congenital heart disease to predict sudden death in the future. This section also combines structural and functional cardiac imaging, with the aim of integrating these approaches and collaborating with the expertise at Imperial College in such areas as Computing, Chemistry, Materials, Fluid Dynamics and Biomedical Engineering to develop new investigational and treatment strategies. We aim to do this by increasing knowledge and understanding of the detectable abnormalities of structure and function in cardiovascular disease.CV Imaging Process Research Paper

The cardiovascular imaging research group focuses on the development and application of methods to help improve diagnosis of cardiovascular diseases using MRI and CT. Cardiovascular researchers have access to state of the art CT and MRI at Northwestern Memorial Hospital and also at Northwestern University Feinberg School of Medicine through the Center for Translational Imaging (CTI). Cardiovascular imaging researchers from radiology collaborate with departments across campus including cardiology, cardiac surgery, vascular surgery, pediatric medicine and biomedical engineering. Cardiovascular Imaging also has a strong collaborative research relationship with Siemens Medical Solutions, who have four PhD scientists on site for research and development.

Feinberg Radiology’s research in cardiovascular imaging equipment and services includes:

Two state-of-the-art MR-systems dedicated to cardiovascular MRI research (Siemens 64-channel 1.5T Area System and Siemens 48-channel 3T Skyra)
State-of-the-art whole-body Siemens 1.5-Tesla Area MRI scanner (Siemens Medical Solutions, Erlangen, Germany), 70 cm open bore design with 64 channels; XQ gradients (45 mT/m @ 200 T/m/s) which offers advanced features such as multi-channel technology and DOT engines not yet released to other systems. The 1.5T scanner has physiological monitoring equipment and a power injector.
State-of-the-art whole-body Siemens 3.0 Tesla Skyra MRI scanner (Siemens Medical Solutions, Erlangen, Germany), 70 cm open bore design with 48 channels; XQ gradients (45 mT/m @ 200 T/m/s). The Magnetom 3T Skyra is the world’s first 70cm Tim+Dot 3 Tesla MR system and sets a new standard for efficiency, ease of use, and the ability to enhance productivity.
The Siemens Powermobile C-ARM Angiographic System is fully equipped for any x-ray angiographic study. It is capable of fluoroscopic and digital subtraction angiographic studies.CV Imaging Process Research Paper

Noninvasive cardiac imaging refers to a combination of methods that can be used to obtain images related to the structure and function of the heart. As opposed to invasive techniques, which require catheters to be inserted into the heart, noninvasive tests are easier to perform, are safe, and can be used to detect various heart conditions, ranging from plaque in the arteries that supply the heart muscle (known as coronary artery disease) to abnormalities that impair the ability of the heart to pump blood.

Recent rapid technologic advances have contributed to the widespread clinical use of coronary computed tomography (CT) with multidetector CT scanners for the noninvasive and accurate assessment of coronary artery disease, and multidetector coronary CT provides excellent image quality. In numerous single- and multicenter trials with CT scanners with 64 or more detectors to enhance spatial and temporal resolution, investigators have demonstrated the superior diagnostic accuracy of multidetector systems for detecting significant coronary artery disease at coronary CT, using invasive catheter coronary angiography as a reference modality (1–4). The high negative predictive value of normal coronary CT results can be used to effectively exclude significant coronary artery disease and to avoid further imaging tests or catheter coronary angiography in patients with low to intermediate risk factor profiles (1–5).

Predicting cardiac events through traditional imaging
The buildup of cholesterol and plaque in the coronary arteries happens gradually over many years. The rupture or breakage of the plaque that causes a blood clot that can result in a heart attack is sudden, and carries little warning. The challenge for diagnostic testing is to detect the condition of an artery before the blockage occurs.

“Most of the time, when people describe their symptoms of a heart attack, they really didn’t have much of an advance warning,” says Dr. David Bush, Director of the Cardiac Computed Tomography Lab at Johns Hopkins Bayview Medical Center.CV Imaging Process Research Paper

“What we’ve come to recognize is that the plaque can sit there for years and not cause a problem. Our goals with imaging for coronary heart disease are to try to detect these plaques before they cause problems, so we might be able to intervene.”

Traditional cardiac diagnostic tests such as stress tests and echocardiograms can show a physician how much blood is flowing to the heart. If there are regions of the heart that are not getting as much blood as others, it might be a sign of clogged coronary arteries. However, blood flow can also appear to be normal even with plaque buildup. New kinds of imaging are required to see the extent of that buildup.

Different types of new cardiovascular imaging
Advanced imaging techniques can display three-dimensional pictures within the arteries, and perhaps provide clues to future cardiovascular events. There are three main types:

Coronary calcium scoring/screening – This test uses a CT scan to take an image the heart, which looks for calcium deposits within the coronary arteries. Calcium is not present in normal coronary arteries and when present is a sign of atherosclerosis. A recent NIH study has shown that the more coronary calcium you have, the greater your risk of a heart attack.
Carotid ultrasound – A new imaging test that looks for thickness of the inner lining of the carotid arteries. It’s been shown that the more this artery thickens, the higher the risk of cardiovascular disease.
CT coronary angiography – Shows calcium deposits and possible blockages or narrowings in the blood vessels. A CT coronary angiography is used to determine whether symptoms such as chest pain or shortness of breath are related to a coronary problem, and whether those symptoms can be treated with medicine, with non-invasive techniques, or with surgery.
Who benefits most from new imaging tests?
New imaging tests are a way to assess the cardiovascular condition among patients not necessarily at low or high risk for cardiovascular disease, but in a kind of middle area where the physician needs to determine future diagnosis or treatment.CV Imaging Process Research Paper

The development and widespread use of noninvasive imaging techniques have contributed to the improvement in evaluation of patients with known or suspected coronary artery disease. Stress echocardiography and single-photon computed tomography are well-established noninvasive techniques with a proven track record for the diagnosis of coronary atherosclerosis. These modalities are generally widely available and provide a relatively high sensitivity and specificity along with an incremental value over clinical risk factors for detection of coronary artery disease. PET has a high diagnostic performance but continues to have limited clinical use because of the high expense of the dedicated equipment and difficulties in obtaining adequate radionuclides. Cardiac MRI and multislice computed tomography constitute the most recent addition to the cardiac imaging armamentarium. Cardiac MRI offers a comprehensive cardiac evaluation, which includes wall-motion analysis, myocardial tissue morphology, rest and stress first-pass myocardial perfusion, as well as ventricular systolic function. Cardiac computed tomography allows coronary calcium scanning along with noninvasive anatomic assessment of the coronary tree. It can be combined with functional imaging to provide a complete evaluation of the presence and physiological significance of the atherosclerotic coronary disease. No single imaging modality has been proven to be superior overall. Available tests all have advantages and drawbacks, and none can be considered suitable for all patients. The choice of the imaging method should be tailored to each person based on the clinical judgment of the a priori risk of cardiac event, clinical history and local expertise.CV Imaging Process Research Paper

Coronary artery disease is the leading cause of death in advanced countries. Early detection and diagnosis of coronary artery disease plays an important role in the identification of disease severity and prediction of disease outcome, consequently improving patient management. Diagnosis and management of coronary artery disease is increasingly dependent on less-invasive imaging modalities, including coronary CT angiography, cardiac magnetic resonance imaging, cardiac radionuclide imaging such as SPECT and PET modalities. Rapid developments of these imaging modalities have significantly improved the diagnostic performance of each imaging technique with high diagnostic accuracy achieved in both diagnostic and prognostic value in coronary artery disease. This editorial provides an overview of the diagnostic applications of a variety of less-invasive imaging modalities in the diagnosis of coronary artery disease. This special issue of “Arteriosclerotic Vascular Disease: Part II” in the journal of Clinical and Experimental Cardiology will give particular attention to contributions focusing on the clinical applications of these imaging modalities in the arteriosclerotic vascular disease, in particular, coronary artery disease.

Keywords
Coronary artery disease; Arteriosclerotic vascular disease; Diagnostic value; Imaging modalities
Coronary artery disease (CAD) is the leading cause of death in advanced countries and its prevalence is increasing among developing countries [1,2]. Various less-invasive imaging modalities are increasingly used in the diagnosis of CAD including coronary CT angiography, cardiac magnetic resonance imaging (MRI), and cardiac single photon emission computed tomography (SPECT), positron emission tomography (PET) and integrated SPECT/CT and PET/CT [3]. To improve early diagnosis and patient management, it is essential to have an overview of the diagnostic value of different imaging modalities in CAD. This editorial provides an overview of the diagnostic performance of these imaging modalities in CAD, with a focus on the advantages, limitations and future directions of the use of each imaging modality in the diagnosis of CAD.
Coronary CT angiography represents the most rapidly developed imaging modality in cardiac imaging with evolution from single slice CT to multislice CT, from early generation of 4- and 16-slice CT to 64- and 320-slice CT scanners, demonstrating excellent visualization of coronary anatomy and assessment of coronary artery disease [4- 6]. In summary, diagnostic sensitivity of coronary CT angiography has been significantly improved with 64- or more slice CT scanners when compared to the early generations of 4- and 16-slice scanners, while, the negative predictive value remains consistently high (>90%), regardless of the type of CT scanners [7-11]. This indicates the main role of coronary CT angiography is to rule out significant CAD, thus reducing the need for invasive coronary angiography. The prime indication of coronary CT angiography is to diagnose patients with a low and intermediate probability of CAD as a simple non-invasive testing, while patients with a high probability of CAD will benefit from invasive coronary angiography [12].CV Imaging Process Research Paper
In addition to the diagnostic value, coronary CT angiography allows for characterization of plaque components (calcified versus non-calcified plaques and shows potential prognostic value of disease extent and cardiac events [13,14]. Studies based on single center and multicenter clinical trials have shown that coronary CT angiography provides incremental prognostic value over clinical risk analysis in predicting major adverse cardiac events with absence of CAD leading to event free survival period, while presence of plaques associated with increased risk of cardiac events [15-19].
Radiation dose associated with coronary CT angiography is the main concern of this technique in cardiac imaging, and this has increased substantially over the last decade with the development of multislice CT scanners and widespread use of cardiac CT in routine clinical practice. This has raised a serious concern and it is a hot topic of debate in the literature. Various dose-saving strategies have been proposed and recommended in the past few years to lower radiation exposure to patients undergoing coronary CT angiography with tremendous progress having been achieved. Effective dose reduction has been accomplished by employing techniques with a radiation dose of less than 10 mSv to as low as 1 mSv in some studies [11,20,21], although much effort is still required to ensure that coronary CT angiography is safely performed in imaging patients with suspected coronary artery disease.
MRI provides excellent soft tissue contrast, with inherent 3D capabilities, and acquisition of images in any anatomical plane. Furthermore, MRI does not expose the patient to ionizing radiation, thus, the usefulness of MRI has been investigated widely. However, the diagnostic accuracy of cardiac MRI in CAD varies widely according to the literature, with sensitivity ranging from 38% to 83%, and specificity ranging from 57% to 95% due to variable scanning protocols used in the studies [22]. Recent technical developments in MRI, especially with the emergence of 3.0 T MR imaging system have been shown to be a promising technique for performing cardiac MRI, with significant improvement of diagnostic value for detection of CAD [23,24]. Despite these advantages, cardiac MRI is still limited in the visualization of distal coronary segments due to inferior spatial resolution, thus, it is not as widely used as coronary CT angiography in the diagnosis of CAD.
Noninvasive evaluation for obstructive CAD is performed by gatekeeper tests that offer physiologic information of coronary stenosis (physiologic imaging) or the degree of stenosis (anatomic imaging). Coronary CT angiography serves as an excellent anatomic gatekeeper as it has a very high negative predictive value, while stress perfusion cardiac MRI is a regarded as a physiologic gatekeeper. Stress perfusion cardiac MRI has been proved to be a robust and accurate diagnostic test for CAD when invasive coronary angiography is used as the reference standard [25-28]. Several systematic reviews and meta-analyses have shown that the sensitivity and specificity of stress perfusion MRI ranged from 89% to 91% and 76% to 81%, using invasive coronary angiography as the reference standard [26-28]. Desai and Jha recently conducted a meta-analysis of 12 studies regarding the cardiac stress perfusion MRI in the diagnosis of flow-limiting obstructive CAD using fractional flow reserve measured at invasive coronary angiography as the reference standard [29]. Their analysis shows that cardiac stress perfusion MRI has a sensitivity of 89.1% and 87.7% and a specificity of 84.9% and 88.6% on a patient-based and on a coronary territory-based analysis, respectively. Thus, cardiac stress perfusion MRI is an accurate test for the detection of flow-limiting stenosis.CV Imaging Process Research Paper
Myocardial perfusion imaging (MPI) with stress gated SPECT has been widely used in the diagnosis of CAD and is a well-documented non-invasive method for risk stratification with high diagnostic accuracy when compared to coronary CT angiography [30,31]. The presence of ischemia could be used to classify the patients as having CAD and candidates for receiving aggressive medical therapy and management. Coronary CT angiography has limited accuracy for identifying the physiologic significance of perfusion defects in patients with intermediate or high pre-test likelihood of CAD when compared to MPI SPECT [32]. Thus, MPI SPECT offers additional functional information in the evaluation of coronary stenosis.MPI SPECT can be used as the gatekeeper to invasive coronary angiography. Bateman et al. showed that referral to invasive coronary angiography was 3.5%, 9%, and 60%, respectively, corresponding to normal to mild, moderately abnormal and severely abnormal perfusion scans [33]. A negative SPECT imaging has been confirmed to serve as an excellent prognostic indicator with an annual cardiac event rate of <1% for the general population, while an increasing cardiac events are associated with increasing severity of both fixed and reversible perfusion defects, regardless of the presence of non-obstructive coronary disease [34-36].
Cardiac PET imaging is another well-established tool for the evaluation of ischemia, blood flow quantification, myocardial viability and perfusion [37,38]. Cardiac PET utilizing 18F-FDG is considered the most sensitive modality for detecting hibernating viable myocardium and predicting left ventricular functional recovery post-coronary revascularization. PET has higher spatial and temporal resolution than SPECT due to more robust methods of attenuation correction, thus, PET allows quantification of resting and hyperemic regional myocardial perfusion. When PET was integrated into clinical patient management, a significant reduction in cardiac events was observed in patients with 18F-FDG PET-assisted management, according to randomized controlled trials [39,40]. PET images provide incremental prognostic information to the clinical and angiographic findings with regard to event-free survival. An increased extent and severity of perfusion defects with stress PET were reported to be associated with increased frequency of adverse cardiac events, thus, this indicates PET can be used to predict cardiac mortality [41,42].
Cardiac PET is not yet as widely available as SPECT imaging. Furthermore, experience in image interpretation and operation may vary widely. Cardiac PET will continue to play a key role in the investigation of myocardial viability and perfusion contributing more to available data.
Integrated SPECT/PET-multislice CT has huge potential for cardiac imaging. The incremental value of hybrid imaging lies in accurate spatial co-localization of myocardial perfusion defects and anatomic coronary arteries. This combined technology allows detection and quantification of the burden of calcified and non-calcified plaques, quantification of vascular activity and endothelial health, identification of flow-limiting coronary stenosis, and potentially identification of high-risk plaques in the coronary artery tree [43]. Combined SPECT/CT and PET/CT systems are today well established in clinical routine imagingwith promising results reported [44-48], although more multicentre trials are needed to validate the diagnostic value of the hybrid imaging modalities. Combined PET/MRI represents another new integrated protocol, however, it is only limited to a few clinical centers for preclinical cardiac imaging with a focus on animal experiments [49,50].
In summary, this editorial briefly reviews the diagnostic applications of these less-invasive imaging modalities including coronary CT angiography, cardiac MRI, cardiac SPECT and cardiac PET in coronary artery disease. Advantages and limitations of each imaging modality in the detection of coronary artery disease are also highlighted. Researchers are encouraged to contribute both original and review papers to this special issue with the aim of delivering both educational and teaching message to clinicians with research interests in cardiac imaging.CV Imaging Process Research Paper

For healthier patients, that decision can be to keep them on a healthy track. For patients who show signs of borderline-high cardiovascular risk, the physician might recommend modifying their diet or taking cholesterol-lowering medication.

It is among this intermediate-risk group of individuals that new imaging can make a difference. Here are a few of the more important things to remember about the relevance of new imaging:

When used properly, new imaging can be useful in putting someone on a diet and exercise plan before they need surgical intervention.
New imaging tests do not replace understanding, recognizing, and managing traditional cardiovascular risk factors such as blood pressure, smoking, diabetes, diet, weight, and exercise.
New imaging may be useful when deciding the next step in treatment, or whether to start treatment at all. For example, this can be especially relevant for people with heart disease in the family, and who are trying to decide whether their current living habits are healthy enough.
In non-lifesaving situations, new imaging tests such as CT angiograms can be a simpler alternative to surgical procedures such as stenting or catheterization.
Women who are post-menopausal have increased cardiovascular risk, and might benefit from new imaging such as calcium screening.
CT coronary angiography might be useful for older women where there’s a question about the nature of their symptoms. Women often have non-classical symptoms of heart disease, or experience a higher rate of false-positive and false-negative stress tests.
“In many cases, new imaging techniques can accurately guide treatment and replace unnecessary surgical procedures,” says Dr. Bush. “The real question is whether new imaging offers an advantage to the individual patient. These are very important judgment calls physicians need to make on a case-by-case basis.”

Coronary artery disease still is the main cause of death worldwide in spite of recent improvements in therapeutic and interventional methods. With the introduction of revascularization therapy, using coronary artery bypass grafting and percutaneous coronary intervention (PCI), the need for identifying viable myocardium has arisen. Furthermore, by preoperatively assessing the transmural size of the infarct, the functional recovery of dysfunctional segments after revascularization therapy in patients with chronic LV dysfunction can be predicted (1-3).CV Imaging Process Research Paper

Cardiac imaging is a rapidly evolving field, with improvements in the diagnostic capabilities of non-invasive cardiac assessment. In this article, we seek to introduce family physicians to the two main emerging technologies in cardiac imaging: computed tomography coronary angiography (CTCA) to evaluate chest symptoms consistent with ischaemia and exclude coronary artery disease; and cardiovascular magnetic resonance (CMR) imaging for evaluating cardiac morphology, function and presence of scar. These modalities are now in routine clinical practice for cardiologists in Australia and New Zealand. We provide a practical summary of the indications, clinical utility and limitations of these modern techniques to help familiarise clinicians with the use of these modalities in day-to-day practice. The clinical vignettes presented are cases that may be encountered in clinical practice. We searched the PubMed database to identify original papers and review articles from 2008 to 2016, as well as specialist society publications and guidelines (Society of Cardiovascular Computed Tomography, Society for Cardiovascular Magnetic Resonance, Cardiac Society of Australia and New Zealand, and Australian and New Zealand Working Group for Cardiovascular Magnetic Resonance), to formulate an evidence-based overview of new cardiac imaging techniques, as applied to clinical practice.

Part 1: Computed tomography coronary angiography for clinicians
CTCA is a non-invasive coronary angiogram, using electrocardiogram (ECG)-gated CT. The accuracy of CTCA has been well established in three large multicentre studies, with a negative predictive value approaching 100%, making it an excellent “rule out” test.1 This means that a normal CTCA showing no coronary plaque or stenosis accurately correlates to absence of disease on invasive angiography. Prognostic data have shown that a negative CTCA has very low event rate (< 1%), whereas increasing levels of disease seen on CTCA are associated with increasing risk of myocardial infarction and death over 5 years for both men and women. CV Imaging Process Research Paper

CTCA has been formally tested in randomised trials of chest pain in the emergency department, showing more rapid discharge and decreased health care costs, including in the Australian health system.3,4

The radiation dose for CTCA has decreased dramatically in recent years, with current generation scanners able to image the entire heart and coronary arteries for 2–3 mSv (equivalent to annual background radiation), and < 1 mSv in appropriate patients (similar to a mammogram). Thus, CTCA is gaining traction in clinical practice to rule out coronary artery disease (CAD) in a variety of clinical situations.

The primary use for CTCA is to exclude significant coronary artery stenosis in patients with symptoms consistent with coronary ischaemia due to potential stenotic CAD (harnessing the near 100% negative predictive value of CTCA). Application of the test in this manner is appropriate for patients with chest pain syndromes, with angina equivalent symptoms (eg, dyspnoea), to exclude graft stenosis in symptomatic patients after coronary artery bypass surgery, and also for patients with ongoing symptoms despite negative results from functional tests such as nuclear or echocardiography stress tests (as functional tests may return false-negative results). The Society of Cardiovascular Computed Tomography has published Appropriate Use Criteria,5 and the Cardiac Society of Australia and New Zealand has produced guidelines on non-invasive coronary imaging CV Imaging Process Research Paper

A number of indirect techniques have been introduced to assess myocardial viability. These techniques are echocardiography (for assessing recovery of contractile function), fluoro-2-deoxygluclose (FDG) positron emission tomography (PET) (for assessing glucose metabolism) and 201Tl single-photon emission computed tomography (SPECT) in patients with ischemic heart disease. Unlike echocardiography, magnetic resonance imaging (MRI) does not present the limitations of the acoustic window. MRI also offers more spatial and temporal resolution than nuclear medicine modalities and better tissue characterization. In addition, MRI does not use ionizing radiation, which is another advantage in respect to other imaging modalities such as computed tomography (CT) or nuclear medicine (4). MR images are acquired with a high contrast between blood pool and myocardium using a steady state free precession (SSFP) sequence. Similar to echocardiography, cine MRI allows dynamic imaging of cardiac wall motion, but with superior endocardial border definition, facilitating more accurate wall motion assessment. Left ventricular function and mass, measured with cine MRI, are used in clinical practice as an endpoint in clinical trials (5,6). End-diastolic wall thickness is easy to measure; however, this indicator does not measure the size of myocardial infarct (MI).

Another method for detecting myocardial viability and critical coronary stenosis is perfusion MRI. With this technique a bolus of contrast media is used to visualize the delay in perfusion in ischemic myocardium compared to healthy myocardium. Perfusion of ischemic myocardium can be assessed quantitatively by calculating perfusion indices (curve upslope, maximum signal intensity and time to the peak). However, clinical studies indicated that MI size is a stronger predictor of future events than LV functional or perfusion parameters, where significant areas of stunning and/or hibernating may be present (7-9).CV Imaging Process Research Paper

Unlike echocardiography, PET and SPECT, MRI has the unique ability to provide quantitative information on cardiac function, perfusion and viability. Delayed enhancement MRI (DE-MRI) provides high contrast between viable and nonviable myocardium, thus it has been frequently used for detecting and measuring MI size. Furthermore, discrimination between viable and infarcted myocardium allows patients to avoid the risks associated with revascularization therapy when they are unlikely to benefit. MRI examination for evaluating suspected coronary artery disease consists of T2-weighted imaging for area at risk (AAR) demonstration and DE-MRI for infarct visualization. A recent study using T2 mapping, however, indicated that edematous reaction during the first week after ischemia/reperfusion is not stable and warranted the use of edema extent in evaluating therapies (10). Inversion-recovery prepared T1-weighted gradient-echo (GRE) sequence after intravenous administration of a gadolinium-chelate demonstrates MI, microvascular obstruction (MVO) zone, patchy microinfarct and peri-infarct zone (incomplete infarct at the infarct border). Evidence suggests that the likely mechanism is different volumes of distribution of gadolinium-based MR contrast media in viable and infarcted myocardium (11). It should be noted that an increased volume of distribution occurs in both acute and chronic (scar) MI, as there is an increase in the interstitial space. In the former, the loss of sarcomere membrane integrity increases the potential interstitial volume, whereas in the latter, the presence of fibrotic tissue increases the interstitial space. Additionally, dynamic first pass perfusion and cine SSFP sequences are used for detection of perfusion deficits and LV remodeling. The main disadvantages of the current cardiac MRI sequences are breath-holds, the exam time, contrast media reaction and relatively high cost. New real-time MRI sequences eliminated part of these disadvantages.

New imaging and radiation risk among women
Techniques have recently been introduced that have dramatically lowered radiation exposure. However, CT angiography and other types of computerized tomography still carry some degree of radiation risk. They are not recommended for younger women, especially when used to image the chest. CT scans are also not recommended for pregnant women. As women age, their radiation risk becomes lower, especially in the years after menopause.CV Imaging Process Research Paper

Advantages
In comparison to other techniques, cardiac MRI offers:

improved soft tissue definition
protocol can be tailored to likely differential diagnoses
a large number of sequences are available
dynamic imaging provides functional assessment
no ionizing radiation
MRI safety still requires consideration
Limitations
MRI is generally inferior to cardiac CT for evaluation of the coronary arteries.

Cardiac MRI can be technically challenging. In particular, a comprehensive understanding of cardiac imaging planes is required for scan planning.

Imaging
Dark blood Imaging
Dark blood imaging may be based on spin echo or steady-state free precession sequences. The fast acquisition time of the sequences minimizes respiratory and cardiac movement artefacts. However, a low signal/noise ratio results in inferior spatial resolution.

These can be T1, T2, or proton density weighted sequences:

T1 weighted sequences achieve better anatomic definition
T2 and PD weighted sequences reach better tissue characterization
White blood Imaging
White blood imaging involves gradient echo sequences and steady-state free precession MRI (SSFP). In practice, the difference between the two is that SSFP is less vulnerable to the T2* effect.

The main advantage of white blood imaging is its fast acquisition. It can obtain movement sequences and allows studying cardiac function and movement.

Flux quantification sequences
The most usual sequence of this group is phase contrast imaging. It encodes flux direction and speed, similarly to CSF flow studies.

Inversion Recovery sequences
These imaging techniques use additional 180º pulses to null signal from blood and other tissues, and, therefore, improve contrast.

The most used sequence is STIR.

Contrast-enhanced techniques
Perfusion imaging (also known as first-pass images)
These are T1 weighted, gradient-echo sequences. Image acquisition is performed 3 minutes after gadolinium contrast administration. If there is a hypoenhanced area, this implies a zone of myocardial infarction that is non-viable.

Viability study delayed (also known as myocardial enhancement study)
These are T1 weighted, gradient-echo sequences. Image acquisition is performed 10 minutes after gadolinium contrast administration.

Focal myocardial fibrosis has a delayed gadolinium contrast wash out. So hyperenhancement indicates a myocardial scar, thus an evolved myocardial infarction.CV Imaging Process Research Paper

Usually, an extra inversion pulse is used to improve contrast between fibrosis and the surrounding myocardium.

coronary artery disease (CAD) remains one of the leading causes of morbidity and mortality worldwide. Moreover, the disease is reaching endemic proportions and will put an enormous strain on health care economics in the near future. Non-invasive testing is important to exclude CAD with a high certainty on the one hand, and to detect CAD with its functional consequences at an early stage, to guide optimal patient management, on the other hand. For these purposes, non-invasive imaging techniques have been developed and used extensively over the last years. Currently, the main focus of non-invasive imaging for diagnosis of CAD is twofold: (1) functional imaging, assessing the haemodynamic consequences of obstructive coronary artery disease; and (2) anatomical imaging, visualising non-invasively the coronary artery tree.

For functional imaging, nuclear cardiology, stress echocardiography, and magnetic resonance imaging (MRI) are used, whereas for anatomical imaging or non-invasive angiography, MRI, multislice CT (MSCT), and electron beam CT (EBCT) are used.

This manuscript will update the reader on the current status of non-invasive imaging, with a special focus on functional imaging versus anatomical imaging for the detection of CAD. The accuracies of the different imaging modalities are illustrated using pooled analyses of the available literature data when available.

Cardiac computed tomography (CT), magnetic resonance imaging (MRI), echocardiography and nuclear myocardial perfusion imaging each offer advantages and disadvantages, and frequently at least two of these tests are required to get the full picture of a patient’s cardiac health. However, in this age of cutting healthcare costs, declining reimbursements and improving efficiency, it would be advantageous to have a single gold standard exam. Technology advances are now making that possibility.

MRI is ideal because it uses zero radiation, offers higher contrast and clarity than CT, can image without contrast and performs perfusion exams. But, its limitation remains its expense, ferrous metal and implantable device safety issues and the complexity of its operation.CV Imaging Process Research Paper

Nuclear imaging is limited because it fails to provide detailed anatomical information and uses ionizing radiation. It also is expensive, and short half-life radiotracers limit its hours of operations and on-demand use.

Software advances have improved 3-D echo image quality to the point where it appears like a CT reconstruction. It uses no radiation and offers immediate images of anatomy inside the body. But, echo has a limited ability to image the function of the heart. It also requires highly trained operators to ensure precise positioning of the transducer and interpretation can be subjective. (To read about recent echo advances from the September-October 2012 issue, go to www.dicardiology.com/article/ultrasound-sees-increasing-use-interventional-procedures)

CT has the major disadvantage of high radiation doses compared to other modalities, but technical advances make CT the most likely dominant cardiac imaging technology in the next decade. The rapid expansion and decreasing cost of computing power has enabled fast iterative reconstruction software for lower dose scans. New detector technology is reducing the amount of electronic noise in lower-dose scans and new ECG gating technology has helped cut dose. Combined, these advances have reduced CT dose by more than 50 percent compared to doses a few years ago.

CT analysis software now allows visualization and quantification of perfusion in the myocardium with images similar to nuclear studies, but with a highly accurate anatomic image base.CV Imaging Process Research Paper

Taking perfusion imaging a step further, CT software now cleared in Europe and in trials in the United States can quantify the fractional flow reserve (FFR) for all vessel segments in the coronary tree, allowing cardiologists to pinpoint the exact lesion causing ischemia. In the future, this technology may eliminate the need for diagnostic catheter angiography and provide a detailed navigation and treatment plan for interventional cardiologists to cut procedure time and improve patient outcomes. (To read more about these CT advances in the September-Octover 2012 issue, go to www.dicardiology.com/article/latest-advances-coronary-ct-angiography-software.)

Since the early 1960s, selective x-ray coronary angiography has provided the only means of visualizing the coronary arterial system in vivo. However, it has several disadvantages. First, the incidence, albeit relatively low, of so-called major adverse events (death, myocardial infarction, or stroke) during or within 24 hours of selective coronary angiography is reported to be 0.2% to 0.3%, and the incidence of so-called minor complications (most of which are related to problems with the peripheral vessels through which catheters are inserted) is roughly 1% to 2%.1–3 Second, x-ray coronary angiography is accompanied by a modest amount of discomfort, because the placement of catheters is invasive. Third, it is expensive: the required equipment is costly, and the performance of the procedure necessitates considerable time and skill of highly trained physicians and support personnel. Last, the information obtained via catheter-based coronary angiography pertains to the coronary arterial lumen alone. As a result, alternative methods of visualizing the coronary arterial system that would allow one to avoid these disadvantages are desirable.

Over the past 15 years, substantial advances have been made in noninvasive cardiac imaging in general and in visualization of the coronary arteries in particular. Magnetic resonance angiography (MRA) of the coronary arteries was advanced in the early 1990s with the development of high-speed gradient techniques and dedicated cardiac coils. The primary advantage of this technique is the patient’s lack of exposure to ionizing radiation or iodinated contrast media. Coronary MRA may also be combined with other magnetic resonance (MR) imaging techniques for assessment of cardiac function, structure, blood flow, and viability. CV Imaging Process Research Paper

Electron-beam computed tomography (CT) with iodinated contrast injection was originally used to perform coronary angiograms, but this has been supplanted by multidetector CT (MDCT) scanners that have 16 to 256 rows of detectors. MDCT can provide visually compelling images of the coronary arterial tree, although at present, the necessary radiation dose is higher than that associated with x-ray coronary angiography.

In this statement, we discuss and summarize these two noninvasive modalities, MRA and computed tomographic angiography (CTA), which may be used for coronary artery evaluation. Because the advantages and limitations of CT to assess the presence and extent of coronary arterial calcification are discussed in a separate document sponsored by the American Heart Association, the assessment of coronary arterial calcification is not presented in this statement. For both MRA and CTA, we provide a discussion of technical issues, applications, advantages, and limitations, after which we offer recommendations for current and future uses. To accomplish this, the Writing Committee conducted a comprehensive review of the literature published between 1990 and 2006. Literature searches of the PubMed/MEDLINE databases were undertaken to identify pertinent articles. Searches were limited to the English language. The major search terms included the following: coronary angiography, coronary disease, coronary vessels, humans, magnetic resonance angiography, tomography, and x-ray computed.

MRA of the Coronary Arteries
Technical Considerations for Coronary MRA
Images of the heart must be obtained rapidly and with high temporal resolution to reduce motion artifacts that could otherwise cause blurring in coronary MRA images. Unlike angiographic images obtained via catheter, MRA (and CTA) images take a long time to acquire; for example, high-resolution MRA visualization of the entire coronary arterial tree takes minutes rather than seconds. In addition, cardiac motion must be accounted for during this time period.

Cardiac Motion
Two sources of motion are associated with coronary MRA: motion related to intrinsic cardiac contraction/relaxation and motion attributable to superimposed diaphragm and chest wall movement during respiration. Because the extent of motion exceeds the diameter of the coronary artery, blurring artifacts of the coronary artery lumen will occur unless adequate motion-suppression techniques are applied. ECG gating is used to account for intrinsic cardiac motion.CV Imaging Process Research Paper

Coronary artery motion occurs in a triphasic pattern during the cardiac cycle. Mid-diastole is the preferred time for image acquisition, because cardiac motion is minimized while coronary flow is high. The patient-specific diastasis period (of reduced coronary motion) is usually determined by visual inspection of cine images perpendicular to the long axis of the proximal/mid-right coronary artery (RCA). Multiple heartbeats are required to generate a coronary MRA. The beat-to-beat variation in the duration of the cardiac cycle and the period of diastasis results in image blurring. β-Blockade prolongs the period of coronary diastasis and may help to improve the quality of coronary MRA images.

Respiratory Motion
A straightforward approach to suppressing respiratory motion involves the use of breath-holding during coronary MRA. However, breath-holding strategies have several limitations. First, spatial and temporal image resolution is limited by the patient’s ability to hold his or her breath. Some patients may have difficulty sustaining adequate breath-holds, particularly when the procedure lasts longer than a few seconds. Additionally, it has been shown that during a sustained breath-hold, there is up to 1 cm of cranial diaphragmatic (and thus cardiac) drift.5–7 Thus, at present, breath-hold strategies for coronary MRA have limited applicability to the broad range of patients with cardiovascular disease.

To overcome these limitations, so-called navigator echoes8–11 (similar to M-mode echocardiographic beams) can be used during free-breathing coronary MRA to track a patient’s diaphragmatic motion. MRA images are acquired only when the diaphragm is within 3 to 5 mm of its end-expiratory position. Respiratory blurring is minimized with this method and may be further reduced by using real-time tracking of the imaged volume position.9

Free-breathing navigator coronary MRA offers improved patient comfort as compared with breath-holding techniques and does not require significant patient motivation. However, this method prolongs the duration of the coronary MRA, because image data are collected only when the end-expiratory position of the diaphragm coincides with the period of coronary artery diastasis.12 Typical examination times for free-breathing 3D navigator coronary MRA are 7 to 15 minutes.

Spatial Resolution
The spatial resolution achievable with 3D MRA imaging (0.7 to 0.8 mm in-plane resolution and 1 to 3 mm through-plane resolution) is inferior to that obtainable with x-ray coronary angiography (<0.3 mm).CV Imaging Process Research Paper

For MRA imaging, improvement in spatial resolution is generally accompanied by reduction in the signal-to-noise ratio (SNR). As the voxel size is reduced toward the resolution achievable with x-ray angiography, methods to reduce motion artifacts from both intrinsic and extrinsic motion of the coronary arteries become increasingly important.13

Contrast Enhancement in Coronary MRA
Coronary MRA examinations are typically performed without the addition of intravenously administered contrast agents. The relative signal of the coronary arteries is augmented using fat-saturation prepulses,14 magnetization transfer contrast prepulses,15 or T2 preparatory pulses,16,17 which take advantage of natural T2 differences between the blood and the surrounding myocardium. When these techniques are used, the coronary lumen appears bright, whereas the surrounding myocardium has reduced signal intensity. The lack of exposure to ionizing radiation and the absence of exogenous contrast agents facilitate repeat MRA studies when clinically warranted.

With the use of intravenous MR contrast agents, the T1 relaxation time for blood can be shortened, which allows for an increased contrast-to-noise ratio for coronary MRA.18,19 The extravascular contrast agents that are presently available in the United States for coronary MRA quickly extravasate from the coronary lumen. Use of these agents requires rapid first-pass imaging, which necessitates breath-holding20 and results in images with reduced spatial resolution (as discussed in Spatial Resolution, above).

Recent Technical Developments
Technical improvements in coronary MRA include the development of MR methods that generate improved coronary signals and support reduced scanning times while simultaneously minimizing the complexity of the examination.

Steady-State With Free-Precession Coronary MRA
Use of the steady-state with free-precession (SSFP) method to perform MRA makes it possible to obtain high signal intensity from the coronary arteries and very high contrast between the ventricular blood pool and the myocardium without the need for contrast agents.21 SSFP imaging permits high-quality coronary MRA during free-breathing with substantial improvements in SNR, contrast-to-noise ratio, and vessel sharpness as compared with standard T2-prepared gradient-echo imaging.22 Therefore, SSFP imaging may lead to improved identification of significant coronary artery stenoses. At present, SSFP is being evaluated at many clinical and research centers.CV Imaging Process Research Paper

Phase-Contrast MR Imaging
The phase-contrast technique measures blood-flow velocity23 combined with arterial diameter to yield a quantitative measurement of blood flow (in milliliters per minute). Blood flow can be determined when a patient is at rest or after he or she is stressed for measurement of coronary artery blood-flow reserve.23,24 Although it has been demonstrated in clinical research, this method can be applied on most 1.5-Tesla and some 3.0-Tesla MR scanners. Coronary blood flow is measured along a 2-cm straight proximal or mid-arterial segment in vessels that are >2 mm in diameter.25

Parallel Imaging for Coronary MRA
Parallel imaging is an MR method for reducing MR scanning time by a factor of 2 to 3.26 However, the trade-off for reduced acquisition time is reduced SNR for visualization of the coronary arteries.

3-Tesla Coronary MRA
Most coronary MRA examinations are performed on 1.5-Tesla MR systems. Higher field, 3-Tesla systems provide better signal and contrast values relative to 1.5-Tesla systems. The recent availability of 3-Tesla systems equipped with dedicated cardiac hardware (eg, real-time spectrometer, parallel receiver technology with high bandwidth, body radiofrequency send coil, vector ECG) and software (parallel imaging, navigators, interactive interface) may provide a means for substantial coronary MRA improvements in the future.27

Whole-Heart Coronary MRA
Until recently, coronary MRA was performed with only portions of each arterial tree visible in each set of images.28 This method requires the MR imaging technologist to have extensive experience and familiarity with coronary artery anatomy. The recent development of whole-heart coronary MRA, which is analogous to coronary CTA, allows for imaging of the entire coronary artery tree in an axially acquired 3D volume. Postprocessing of the 3D images is performed in a manner similar to that for coronary CTA. To collect such large volumetric data sets, spatial resolution is somewhat lower (usually >1 mm in-plane and through-plane resolution), data are collected over approximately 100 ms of each cardiac cycle (with potential for blurring), and scan times are lengthy (10 to 15 minutes), thereby mandating the use of navigator echoes. Nevertheless, the whole-heart coronary MRA approach has gained rapid acceptance on the basis of promising initial results. CV Imaging Process Research Paper

Clinical Applications and Results
Anomalous Coronary Artery
Projection x-ray angiography has traditionally been the imaging test of choice for the diagnosis and characterization of coronary artery anomalies. However, the presence of an anomalous coronary artery origin is sometimes only suspected after the invasive procedure, particularly in the case of unsuccessful engagement or visualization of a coronary artery. In addition, the declining use of pulmonary artery catheters during routine x-ray coronary angiography has made it more difficult to discern the anterior versus the posterior trajectory of the anomalous vessels.

Multiple published series exist30–33 of patients who underwent blinded comparison of coronary MRA with x-ray angiography (Table 1). Early coronary MRA studies often used a 2D breath-hold ECG-triggered segmented k-space gradient-echo approach.30–36 These 2D coronary MRA studies uniformly reported excellent accuracy, including several studies in which coronary MRA was determined to be superior to x-ray angiography.31,32 At most centers, 3D coronary MRA is now used, because it offers superior reconstruction capabilities with similarly excellent results.37 For these reasons, coronary MRA is the preferred test for younger patients in whom an anomalous artery origin is suspected or a known anomalous coronary artery origin needs to be clarified and for patients who have another cardiac anomaly associated with coronary anomalies (eg, tetralogy of Fallot).

Reliable coronary imaging with the use of standard coronary CT is also limited by (a) insufficient spatial resolution, specifically for evaluating small or peripheral vessel disease and the lumen of coronary stents, particularly those with a diameter of less than 3 mm (6); (b) insufficient temporal resolution, which causes motion and stair-step artifacts; (c) severe coronary calcification; and (d) limited characterization of coronary plaque (Table). Various clinical solutions with current and novel imaging techniques are designed to overcome these issues. Specifically, high-definition CT can be used to improve in-plane spatial resolution; dual-source CT and a motion correction algorithm (SnapShot Freeze; GE Healthcare, Milwaukee, Wis) can be used to improve temporal resolution and reduce motion artifacts; and dual-energy CT can be used to reduce beam-hardening artifacts, remove (or decrease) the depiction of coronary calcification, and provide a detailed analysis of plaque composition (Table). A comprehensive understanding of these imaging techniques will increase the value of coronary CT for the assessment of coronary artery disease.

The purpose of this article is to help radiologists understand the limitations of standard coronary CT and the various current imaging techniques to overcome these limitations. First, standard coronary CT is reviewed, along with its limitations. Then an overview of current and novel imaging techniques of coronary CT is presented, as well as optimal imaging strategies with the use of these techniques to overcome the limitations of standard coronary CT. Illustrative clinical data and images are provided.CV Imaging Process Research Paper

Standard Coronary CT and Its Limitations
Standard Retrospective ECG-gated Helical Scan
The primary challenge in imaging small and rapidly moving coronary arteries with CT is having sufficiently high spatial resolution to resolve the fine structures and sufficiently high temporal resolution to freeze arterial motion. Frequently, imaging is best performed during the diastolic phase, the most quiescent part of the cardiac cycle. Monitoring the cardiac cycle with ECG recording during scanning enables (a) the synchronization of image acquisition and reconstruction with cardiac motion, (b) the reconstruction of images with retrospective gating, and (c) the selection of the optimal reconstruction phase to diminish motion artifacts that arise from occasional premature beats.

The combined use of multidetector CT scanners with the retrospective ECG-gated helical scanning technique allows high-speed acquisition of motion-free volume data for the whole heart with submillimeter spatial resolution during a single breath hold. Current CT scanners with 64 or more detectors are widely used to assess coronary artery disease noninvasively and accurately, and they provide excellent image quality. The standard retrospective ECG-gated helical technique requires a highly overlapping scan with a low pitch (eg, 0.16–0.24) to ensure coverage of the entire heart with a constant tube current and thus to enable selection of the reconstruction window throughout the cardiac phase (Fig 1a). However, in many patients, particularly those with a sufficiently low and regular heart rate, acquisition of other phases is often unnecessary because the diastolic phase is optimal for reconstruction of coronary CT.

Exposure of the patient to a nephrotoxic contrast medium and carcinogenic radiation limits the usefulness of coronary CT. The radiation dose is greater for coronary CT than for routine diagnostic catheter coronary angiography when the standard retrospective electrocardiography (ECG)–gated helical scanning technique with a tube voltage of 120 kVp is applied with a low helical pitch and high tube power on CT scanners with 64 or more detectors. Various imaging techniques that have been introduced to reduce the radiation dose include the step-and-shoot scan, iterative reconstruction, and the prospective ECG-gated high-pitch dual-source helical scan (Flash Spiral Cardio; Siemens Healthcare, Erlangen, Germany)CV Imaging Process Research Paper

As a result of technological advances, the number of available noninvasive cardiac tests that physicians can order has increased substantially over the last decade (the Figure). Although these tests have improved physicians’ abilities to diagnose and treat heart disease, it is important to understand that not all individuals benefit from noninvasive cardiac imaging. Therefore, these tests should be ordered only at the advice of a physician and should be considered only if the information provided would influence subsequent treatment with medications, procedures, or lifestyle interventions.

These efforts have addressed some of the challenges facing cardiac imaging, but many remain. Health care reform is raising expectations about access to care and cost reductions. Reform is mandating new ways of paying for imaging services that emphasize value over volume, a far more challenging standard to demonstrate (19). Although it is easy to be pessimistic about these changes, opportunities abound. A consortium of cardiovascular imaging centers has demonstrated that a partnership with payers can yield dramatic improvements in imaging safety and appropriateness 20, 21. The introduction of novel percutaneous devices for valvular and structural heart disease requiring complex imaging has highlighted an essential role for imagers on the heart team. New technologies such as fractional flow reserve derived from computed tomography (FFRCT) and positron emission tomography (PET)-CT offer hope that we will soon attain the “holy grail” of imaging in coronary artery disease diagnosis: providing both anatomic and functional information noninvasively.

Despite such progress, the changing landscape of health care remains challenging to the field of cardiac imaging and to imagers individually. Accordingly, the American College of Cardiology’s (ACC) Executive Committee and Cardiovascular Imaging Section Leadership Council convened a discussion regarding the future of cardiac imaging during a 2-day Think Tank held at Heart House on April 28 and 29, 2015. Participants were thought leaders in the field, including council leadership and experts nominated by the participating organizations (Online Appendix). The charge was to think broadly about the future of imaging and develop a road map to address the critical challenges facing cardiac imagers.CV Imaging Process Research Paper

The Think Tank was chaired by Pamela S. Douglas, MD, and Manuel D. Cerqueira, MD, and guided by a steering committee that included representatives from the ACC Cardiovascular Imaging Council and 5 cardiovascular imaging subspecialty societies: the American Society of Echocardiography, the American Society of Nuclear Cardiology, the Society of Cardiovascular Computed Tomography, the Society for Cardiovascular Magnetic Resonance, and the Society for Cardiovascular Angiography and Interventions. Representatives from the American Heart Association, the American College of Radiology, the Radiological Society of North America, the Intersocietal Accreditation Commission, and the Society of Nuclear Medicine and Molecular Imaging also joined the dialogue. Discussion focused on creating a vision for the future on the basis of the current state of the field and sought to develop specific actionable recommendations to ensure a vibrant presence for cardiac imaging in contemporary health care. It was organized around 4 goals: 1) to preserve and enhance the relevance of cardiac imaging in a value-based health care system; 2) to define the cardiac imager of the future; 3) to ensure robust innovation and research; and 4) to maximize imaging information and improve outcomes. CV Imaging Process Research Paper