Comparison of Echocardiography and Multi-Planar Gated Acquisition Scans for Predicting Cancer-Treatment-Related Cardiovascular Dysfunction

BACKGROUND

Current guidelines recommend using sequential cardiac imaging to monitor for cancer treatment-related cardiac dysfunction (CTRCD) in patients undergoing potentially cardiotoxic chemotherapy. Multiple different imaging cardiac modalities are available and there are few prospective head-to-head comparative studies to help guide treatment.

OBJECTIVES

To perform an exploratory prospective cohort study of "real-world" CTRCD comparing multigated acquisition nuclear ventriculography (MUGA) at the referring cancer specialist's discretion with a novel echocardiographic strategy at an Australian tertiary hospital.

METHOD

Patients were recruited from haematology and oncology outpatient clinics if they were scheduled for treatment with anthracyclines and/or trastuzumab. Patients underwent simultaneous MUGA-based cardiac imaging (conventional strategy) at a frequency according to evidenced-based guidelines in addition to researcher-conducted echocardiographic imaging. The echocardiographic imaging was performed in all patients at time points recommended by international society guidelines. Outcomes included adherence to guideline recommendations, concordance between MUGA and echocardiographic left ventricular ejection fraction (LVEF) measurements, and detection of cardiac dysfunction (defined as >5% LVEF decrement from baseline by three-dimensional [3D]-LVEF). A secondary end point was accuracy of global longitudinal strain in predicting cardiac dysfunction.

RESULTS

In total, 35 patients were recruited, including 15 with breast cancer, 19 with haematological malignancy, and one with gastric cancer. MUGA and echocardiographic LVEF measurements correlated poorly with limits of agreement of 30% between 3D-LVEF and MUGA-LVEF and 37% for 3D-LVEF and MUGA-LVEF. Only one case (2.9%) of CTRCD was diagnosed by MUGA, compared with 12 (34.2%) cases by echocardiography. Four (4) patients had >10% decrement in 3D-LVEF that was not detected by MUGA. Global longitudinal strain at 2 months displayed significant ability to predict CTRCD (area under the curve, 0.75, 95% confidence interval, 0.55-0.94).

CONCLUSIONS

The MUGA correlates poorly with echocardiographic assessment with substantial discrepancy between MUGA and echocardiography in CTRCD diagnosis. Echocardiographic and MUGA imaging strategies should not be considered equivalent for imaging cancer patients, and a single imaging modality should ideally be used per patient to prevent misdiagnosis by inter-modality variation These findings should be considered hypothesis-generating and require confirmation with larger studies.

Competency based medical education in nuclear cardiology: A tale of two axes

BACKGROUND

Across medical specialties, including nuclear cardiology, competency based medical education (CBME) changes the emphasis of learning from a time or experiential emphasis to a proficiency focused approached. Plotted on a learning-curve graph the emphasis on learning has shifted from the duration/ volume-based x-axis to the performance-based y-axis.

CURRENT STATUS

It has proven difficult to establish y-axis-based standards within nuclear cardiology to assess learning. As such there is a paucity of data to verify current experiential training targets and only recently is data emerging that seeks to find CBME targets by which proficiency (y-axis units) can be evaluated. Initial reports from such CBME-oriented studies indicate that in current nuclear cardiology practice, the number of studies required to achieve competency is dependent upon the chosen measure of competency that is assessed (summed stress score versus % LV ischemia), the case mix, and the modality being learnt (PET versus SPECT). Recent findings have also suggested that prior levels of experiential training may be an underestimation of the number of supervised studies learners need to interpret before they achieve competency.

SUMMARY

Nuclear cardiology training has adopted the concept of CBME and is progressing toward a more modern approach to trainee assessment. This brief review provides the background, current requirements and insights into new developments in nuclear cardiology training.

Competency-based cardiac imaging for patient-centred care. A statement of the European Society of Cardiology (ESC). With the contribution of the European Association of Cardiovascular Imaging (EACVI), and the support of the Association of Cardiovascular Nursing & Allied Professions (ACNAP), the Association for Acute CardioVascular Care (ACVC), the European Association of Preventive Cardiology (EAPC), the European Association of Percutaneous Cardiovascular Interventions (EAPCI), the European Heart Rhythm Association (EHRA), and the Heart Failure Association (HFA) of the ESC

Imaging plays an integral role in all aspects of managing heart disease and cardiac imaging is a core competency of cardiologists. The adequate delivery of cardiac imaging services requires expertise in both imaging methodology-with specific adaptations to imaging of the heart-as well as intricate knowledge of heart disease. The European Society of Cardiology (ESC) and the European Association of Cardiovascular Imaging have developed and implemented a successful education and certification programme for all cardiac imaging modalities. This programme equips cardiologists to provide high quality competency-based cardiac imaging services ensuring they are adequately trained and competent in the entire process of cardiac imaging, from the clinical indication via selecting the best imaging test to answer the clinical question, to image acquisition, analysis, interpretation, storage, repository, and results dissemination. This statement emphasizes the need for competency-based cardiac imaging delivery which is key to optimal, effective and efficient, patient care.

Hybrid PET/MR in Cardiac Imaging

In the last few years, technological advances in MR imaging, PET detectors, and attenuation correction algorithms have allowed the creation of truly integrated PET/MR imaging systems, for both clinical and research applications. These machines allow a comprehensive investigation of cardiovascular diseases, by offering a wide variety of detailed anatomical and functional data in combination. Despite significant pathophysiologic mechanisms being clarified by this new data, its clinical relevance and prognostic significance have not been demonstrated yet.

Competency-based cardiac imaging for patient-centred care. A statement of the European Society of Cardiology (ESC). With the contribution of the European Association of Cardiovascular Imaging (EACVI), and the support of the Association of Cardiovascular Nursing & Allied Professions (ACNAP), the Association for Acute CardioVascular Care (ACVC), the European Association of Preventive Cardiology (EAPC), the European Association of Percutaneous Cardiovascular Interventions (EAPCI), the European Heart Rhythm Association (EHRA), and the Heart Failure Association (HFA) of the ESC

Imaging plays an integral role in all aspects of managing heart disease and cardiac imaging is a core competency of cardiologists. The adequate delivery of cardiac imaging services requires expertise in both imaging methodology-with specific adaptations to imaging of the heart-as well as intricate knowledge of heart disease. The European Society of Cardiology (ESC) and the European Association of Cardiovascular Imaging have developed and implemented a successful education and certification programme for all cardiac imaging modalities. This programme equips cardiologists to provide high quality competency-based cardiac imaging services ensuring they are adequately trained and competent in the entire process of cardiac imaging, from the clinical indication via selecting the best imaging test to answer the clinical question, to image acquisition, analysis, interpretation, storage, repository, and results dissemination. This statement emphasizes the need for competency-based cardiac imaging delivery which is key to optimal, effective and efficient, patient care.

Comorbidities and cardiac symptoms can modify myocardial function regardless of ischemia: a cross-sectional study with PET/CT

Objective

Associating comorbidities and cardiac symptoms that alter myocardial mechanical function could help clinicians to correctly identify at-risk population.

Methods

We conducted a functional open population cross-sectional study of patients referred to a positron emission computed tomography/computed tomography unit in Mexico City for evaluation of myocardial function, perfusion, and coronary circulation. Ischemia was defined as a sum difference score (SDS) > 2. Association between comorbidities and cardiac symptoms was tested using logistic regression models and trend analysis. We performed an interaction analysis to evaluate the addition of any accompanying symptoms to comorbid conditions on impairment of myocardial function.

Results

One thousand two hundred and seventy-three patients were enrolled, 66.1% male, with a mean age of 62.4 (± 12.7) years, 360 (28.7%) with ischemia, 925 (72.7%) with at least one comorbidity, and 676 (53.1%) had at least one associated cardiac symptom. Patients without ischemia, type 2 diabetes, arterial hypertension, and adverse cardiac symptoms were associated with adverse function, perfusion, and coronary flow parameters. We observed a trend of a cumulative number of comorbidities and cardiac symptoms with increased ischemia and decreased coronary flow. Only in decreased LVEF, we demonstrated an interaction effect between increased comorbidities and adverse symptoms.

Conclusions

The high burden of comorbidities and symptoms in our population alter myocardial function regardless of the level of ischemia.

Preparing for the Artificial Intelligence Revolution in Nuclear Cardiology

A major opportunity in nuclear cardiology is the many significant artificial intelligence (AI) applications that have recently been reported. These developments include using deep learning (DL) for reducing the needed injected dose and acquisition time in perfusion acquisitions also due to DL improvements in image reconstruction and filtering, SPECT attenuation correction using DL without need for transmission images, DL and machine learning (ML) use for feature extraction to define myocardial left ventricular (LV) borders for functional measurements and improved detection of the LV valve plane and AI, ML, and DL implementations for MPI diagnosis, prognosis, and structured reporting. Although some have, most of these applications have yet to make it to widespread commercial distribution due to the recency of their developments, most reported in 2020. We must be prepared both technically and socio-economically to fully benefit from these and a tsunami of other AI applications that are coming.

Utility of nuclear cardiovascular imaging in the cardiac intensive care unit

The contemporary Cardiac Intensive Care Unit (CICU) has evolved into a complex unit that admits a heterogeneous mix of patients with a wide range of acute cardiovascular diseases often complicated by multi-organ failure. Although electrocardiography (ECG) and echocardiography are well-established as first-line diagnostic modalities for assessing patients in the CICU, nuclear cardiology imaging has emerged as a useful adjunctive diagnostic modality. The versatility, safety and accuracy of nuclear imaging (e.g., perfusion, metabolism, inflammation) for the assessment of patient with coronary artery disease, ventricular arrhythmias, infiltrative cardiomyopathies, infective endocarditis and inflammatory aortopathies has been proven useful and now often incorporated into the best practices for the management of critically ill cardiac patients. Thus, clinicians must familiarize themselves with the value and current and future applications of nuclear imaging in the management of the cardiac patient in the CICU.

Performance evaluation of a novel multi-pinhole collimator on triple-NaI-detector SPECT/CT for dedicated myocardial imaging

BACKGROUND

In this study we evaluated the imaging capabilities of a novel Multi-pinhole collimator (MPH-Cardiac) specially designed for nuclear cardiology imaging on a Triple-NaI-detector based SPECT/CT system.

METHODS

^99mTc point source measurements covering the field of view (FOV) were used to determine tomographic sensitivity (TS_pointsource) and spatial resolution. Organ-size tomographic sensitivity (TS_organ) was measured with a left ventricle (LV) phantom filled with typical myocardial activity of a patient scan. Reconstructed image uniformity was measured with a 140 mm diameter uniform cylinder phantom. Using the LV phantom once filled with ^99mTc and after with ¹²³I, Contrast-to-noise ratio (CNR) was measured on the reconstructed images by ROI analysis on the myocardium activity and on the LV cavity. Furthermore, a polar map analysis was performed determining Spill-Over-Ratio in water (SOR_water) and image noise. The results were compared with that of a dual-head parallel-hole low energy high resolution (LEHR) collimator system. A patient with suspected coronary artery disease (CAD) was scanned on the LEHR system using local protocol of 16 min total acquisition time, followed by a 4-min MPH-Cardiac scan.

RESULTS

Peak TS_pointsource was found to be 1013 cps/MBq in the axial center of the FOV while it was decreasing toward the radial edges. TS_organ in the CFOV was found to be 134 cps/MBq and 700 cps/MBq for the LEHR and MPH-Cardiac, respectively. Average spatial resolution throughout the FOV was 4.38 mm FWHM for the MPH-Cardiac collimator. Reconstructed image uniformity values were found to be 0.292% versus 0.214% for the LEHR and MPH-Cardiac measurements, respectively. CNR was found to be higher in case of MPH-Cardiac than for LEHR in case of ^99mTc (15.5 vs. 11.7) as well as for ¹²³I (13.5 vs. 8.3). SOR_water values were found to be 28.83% and 21.1% for the ^99mTc measurements, and 31.44% and 24.33% for the ¹²³I measurements for LEHR and MPH-Cardiac, respectively. Pixel noise of the ^99mTc polar maps resulted in values of 0.38% and 0.24% and of the ¹²³I polar maps 0.62% and 0.21% for LEHR and MPH-Cardiac, respectively. Visually interpreting the patient scan images, MPH-Cardiac resulted in better image contrast compared to the LEHR technique with four times shorter scan duration.

CONCLUSIONS

The significant image quality improvement achieved with dedicated MPH-Cardiac collimator on triple head SPECT/CT system paves the way for short acquisition and low-dose cardiovascular SPECT applications.

Advances in Digital PET Technology and Its Potential Impact on Myocardial Perfusion and Blood Flow Quantification

PURPOSE OF REVIEW

In this review, we explore the development of digital PET scanners and describe the mechanism by which they work. We dive into some technical details on what differentiates a digital PET from a conventional PET scanner and how such differences lead to better imaging characteristics. Additionally, we summarize the available evidence on the improvements in the images acquired by digital PET as well as the remaining pitfalls. Finally, we report the comparative studies available on how digital PET compares to conventional PET, particularly in the quantification of coronary blood flow.

RECENT FINDINGS

The advent of digital PET offers high sensitivity and time-of-flight (TOF), which allow lower activity and scan times, with much less risk of detector saturation. This allows faster patient throughput, scanning more patients per generator, and acquiring more consistent image quality across patients. The higher sensitivity captures more of the potential artifacts, particularly motion-related ones, which presents a current challenge that still needs to be tackled. The digital silicon photomultiplier (SiPM) positron emission tomography (PET) machine has been an important development in the technological advancements of non-invasive nuclear cardiovascular imaging. It has enhanced the utility for PET myocardial perfusion imaging (MPI) and myocardial blood flow (MBF) quantification.

Development of a novel small-animal myocardial phantom can evaluate the image quality of dual-isotope simultaneous acquisition (DISA)

BACKGROUND

Myocardial phantom studies are widely used as a tool to accurately assess the physical phenomenon of dual-isotope simultaneous acquisition (DISA) in the small-animal fields. However, the previous phantom did not reproduce the structures of rats or mice. The aim of this study was to develop a novel myocardial phantom simulating the structure of a small animal that can be evaluated using the image quality of DISA.

METHODS

A novel small-animal myocardial phantom that simulated a rat was constructed by the myocardium, liver, lung, spine, and torso. Normal and inferior wall defect myocardial phantoms were filled with ^99mTc or ¹⁸F solution to simulate single-isotope acquisition (SIA) and DISA. Phantom and small-animal images with no scatter correction (nonSC) and scatter correction (SC) were created.

RESULTS

The ^99mTc DISA with SC showed a low %CV compared to that with nonSC. Although the ^99mTc DISA with nonSC had lower cavity contrast than that of ^99mTc SIA with nonSC, the cavity contrast of SC had similar values between SIA and DISA. The minimum %uptake of ^99mTc SIA with nonSC was a lower value compared to that of ^99mTc DISA with nonSC. The ^99mTc DISA was equivalent to the minimum %uptake of ^99mTc SIA by SC.

CONCLUSION

We have developed a novel myocardial phantom for the rat model to evaluate the image quality for reproducing the physical phenomenon associated with radiation attenuation and scattering. Furthermore, we could demonstrate the usefulness of the novel small-animal myocardial phantom by image quality evaluation of DISA with ^99mTc and ¹⁸F compared to SIA.

Methods of calculating 123I-β-methyl-P-iodophenyl-pentadecanoic acid washout rates in triglyceride deposit cardiomyovasculopathy

Objective

This study aimed to optimize various methods of calculating washout rates (WRs) of ¹²³I-β-methyl-p-iodophenyl-pentadecanoic (BMIPP), as they are essential to diagnose triglyceride deposit cardiomyovasculopathy (TGCV) which is a rare disease entity identified in Japan and has been encoded in Orphanet (ORPHA code 565612).

Methods

We calculated WRs of ¹²³I-BMIPP from early (20 min) and delayed (200 min) images. We evaluated six methods of calculating WRs to discriminate TGVC patients (age, 56.8 ± 14.6 y; male, n = 13; female, n = 4) and 21 ¹²³I-BMIPP studies were involved including 4 follow-up studies. Washout rates were calculated by two planar methods using anterior images with cardiac and background regions of interest (ROIs) and by four SPECT methods using either array and polar plots or summed short-axis images. The final diagnoses of TGCV were confirmed according to the 2020 diagnostic criteria, and the diagnostic accuracy of WRs calculated using the six methods was analyzed using the area under receiver-operating characteristics curves (ROC-AUC). Multiple scatter-plot matrix methods were evaluated with correlations for comparison.

Results

All six methods were useful for diagnosis and did not significantly differ. The four SPECT methods showed excellent diagnostic accuracy (AUC 1.0), whereas the planar methods with and without background correction could be acceptable (AUC 0.857 and 0.964, respectively). The WRs were relatively lower for patients with CAD and remarkable metabolic defects than for patients with TGCV but without defects.

Conclusions

For the diagnosis of TGCV, the WR cutoff of 10% of ¹²³I-BMIPP functioned well in planar and SPECT discrimination based on computational methods as a classifier. However, calculation optimization should improve TGCV diagnoses.

Correlation of Quantitative 99mTc DPD Scintigraphy With Echocardiographic Alterations in Left Atrial Parameters in Transthyretin Amyloidosis

AIM

Cardiac transthyretin amyloidosis (ATTR) patients have high rates of atrial arrhythmias. We evaluated echocardiographic structural and functional left atrial (LA) parameters and correlated these with technetium-99m 3,3-diphosphono-1,2-propanodicarboxylic acid (^99mTc-DPD) bone scintigraphy tracer uptake within the LA in ATTR patients.

METHODS

ATTR patients (wild-type, hereditary and asymptomatic transthyretin [TTR] variant carriers) who had undergone ^99mTc-DPD and transthoracic echocardiogram (TTE) were selected. Quantitative ^99mTc-DPD uptake analysis and echocardiographic evaluation of LA structural and functional parameters was performed.

RESULTS

Forty (40) ATTR patients (wild-type n=17; hereditary ATTR and TTR variant carriers n=23; median age 68.8±22 years) were included. TTE parameters including indexed LA minimum (LAV_min) (r=0.66), and LA maximum volumes (LAV_max) (r=0.64), LA emptying fraction (LAEF) (r=-0.68), LA function index (LAFI) (r=-0.70) and reservoir strain (ƐR) (r=-0.70) (p<0.001 for all) demonstrated good correlation to LA tracer uptake. Normal LA volume (LAV_min and LAV_max) and function (LAEF, LAFI and ƐR) was observed in hereditary ATTR and TTR variant carriers without cardiac tracer uptake. The subgroup of ATTR patients with atrial fibrillation/flutter demonstrated increased LAV_min and LAV_max with further reduction in LA function (LAEF, LAFI and ƐR). Receiver operating characteristic curves demonstrated strong diagnostic accuracies for LA structural (LAV_min and LAV_max; area under the curve [AUC] of 0.83 and 0.84 respectively) and functional (LAEF, LAFI and ƐR; AUC 0.81, 0.88 and 0.85, respectively) parameters.

CONCLUSION

Left atrial structural and functional parameters demonstrated good correlations with quantitative ^99mTc-DPD tracer LA uptake. Echocardiography and ^99mTc-DPD scintigraphy may have significant roles in identification and surveillance of ATTR patients likely to develop atrial arrhythmias.

Nuclear Cardiology in Women and Underrepresented Minority Populations

PURPOSE OF REVIEW

To outline sex-specific features of coronary artery disease (CAD) that should be considered in the assessment of women, including those from ethnic minority populations with suspected stable ischemic heart disease (IHD). Second, to determine the latest nuclear imaging tools available to assess microvascular CAD.

RECENT FINDINGS

Latest studies indicate that women are more likely to have ischemia with no obstructive coronary arteries (INOCA) and paradoxically have worse outcomes. Therefore, the evaluation of women with suspected IHD should include assessing microvascular and epicardial coronary circulation. The prevalence of CAD is increasing in younger women due to the increased cardiovascular disease (CVD) risk burden. CAD is often underrecognized in these patients. There is increasing recognition that INOCA is not benign and should be accurately diagnosed and managed. Nuclear imaging assesses the full spectrum of CAD from microvascular CAD to multivessel obstructive epicardial CAD. Further research on myocardial blood flow (MBF) assessment with PET MPI is needed.

Artificial Intelligence to Improve Risk Prediction with Nuclear Cardiac Studies

Purpose of Review

As machine learning-based artificial intelligence (AI) continues to revolutionize the way in which we analyze data, the field of nuclear cardiology provides fertile ground for the implementation of these complex analytics. This review summarizes and discusses the principles regarding nuclear cardiology techniques and AI, and the current evidence regarding its performance and contribution to the improvement of risk prediction in cardiovascular disease.

Recent Findings and Summary

There is a growing body of evidence on the experimentation with and implementation of machine learning-based AI on nuclear cardiology studies both concerning SPECT and PET technology for the improvement of risk-of-disease (classification of disease) and risk-of-events (prediction of adverse events) estimations. These publications still report objective divergence in methods either utilizing statistical machine learning approaches or deep learning with varying architectures, dataset sizes, and performance. Recent efforts have been placed into bringing standardization and quality to the experimentation and application of machine learning-based AI in cardiovascular imaging to generate standards in data harmonization and analysis through AI. Machine learning-based AI offers the possibility to improve risk evaluation in cardiovascular disease through its implementation on cardiac nuclear studies.

Graphical Abstract

AI in improving risk evaluation in nuclear cardiology. * Based on the 2019 ESC guidelines

The application of artificial intelligence in nuclear cardiology

A decade of unprecedented progress in artificial intelligence (AI) has demonstrated a lot of interest in medical imaging research including nuclear cardiology. AI has a potential to reduce cost, save time and improve image acquisition, interpretation, and decision-making. This review summarizes recent researches and potential applications of AI in nuclear cardiology and discusses the pitfall of AI.

18F-FDG PET/CT in cardiovascular infection and inflammation

The diagnosis of cardiovascular infection and inflammation by [¹⁸F]FDG PET/CT in Nuclear Cardiology is of growing interest, because with respect to echocardiography this technique has improved the certainty in the diagnosis of infective endocarditis in patients with prosthetic valves, the increasing number of patients with implantable cardiac devices because of the progressive ageing of the population, as well as in patients with suspected large vessel vasculitis. All are serious clinical situations which require correct diagnosis and appropriate treatment as soon as possible, because they can cause severe complications, high mortality and also increased health care costs. We review the use of [¹⁸F]FDG PET/CT in cardiovascular infection and inflammation, including the clinical point of view and the contribution of other image modalities. We focus on the appropriate methodology for this exploration, patient preparation, image acquisition and correct interpretation and the quantification possibilities, defining the specific characteristics of the diagnosis in patients with prosthetic valves, implantable cardiac devices and large vessel vasculitis in the initial diagnosis as well as during follow-up to assess treatment response. We analyze the possible causes of false positive and false negative results and emphasize the special value of a multidisciplinary team for optimal management of these patients.

Incremental Predictive Value of Coronary Calcium Score in Risk Stratification of Coronary Revascularization in Patients With Normal or Mild Ischemia Using Nuclear Myocardial Perfusion Single Photon Emission Computed Tomography

BACKGROUND

The incremental predictive value of the coronary artery calcium score (CACS) for risk stratification of coronary revascularization in patients with normal or mildly abnormal nuclear myocardial perfusion single photon emission computed tomography (MPS) scores is unknown.Methods and Results:We analyzed 528 patients in whom CACS was calculated and who underwent stress MPS within 3 months. Patients with known coronary artery disease, prior coronary revascularization, and those undergoing hemodialysis were excluded. Patients were followed-up with coronary revascularization based on the evidence of physiological ischemia defined by fractional flow reserve or severe coronary stenosis (≥90%). CACS was significantly associated with the summed stress score (SSS) from MPS assessment. Multivariate logistic regression analysis showed that high CACS (≥300; odds ratio [OR] 5.44, 95% confidence interval [CI] 2.28-13.0) and SSS (OR 1.29, 95% CI 1.18-1.40) were significant (P<0.001) predictors of future coronary revascularization. The log-rank test showed that high CACS stratified coronary revascularization in normal SSS (0-3; P<0.001) or mildly abnormal SSS (4-8; P=0.028) groups, whereas high CACS did not significantly stratify coronary revascularization in moderate to severe SSS (≥9; P=0.757).

CONCLUSIONS

Risk stratification using CACS with a cut-off value 300 may have incremental predictive value for revascularization in patients with normal or mildly abnormal MPS.

Contemporary Cardiovascular Imaging Advancements and Social Media

Purpose of review

Social media (SoMe) as a means of knowledge dissemination has grown significantly in cardiovascular imaging in recent years. This media platform allows for a free exchange of ideas, the development of new communities, and the ability to disseminate advancements rapidly. While the social media platforms offer limitless potential, their public domain necessitates several important suggestions around best practices.

Recent findings

In cardiovascular imaging, specific hashtags have emerged to encompass the major modalities to include #EchoFirst, #YesCCT, #WhyCMR, and #CVNuc. Cardiovascular imaging journals have established major presences in the social media space as an avenue to present novel, high-quality, peer-reviewed content to new audiences.

Summary

This review paper aims to introduce basic concepts in social media and cardiovascular imaging while highlighting recent topics of high importance, influence, and attention in cardiovascular imaging to include the ISCHEMIA trial, COVID-19, structural imaging, and multimodality advances from throughout 2020.

Quantitative clinical nuclear cardiology, part 2: Evolving/emerging applications

Quantitative analysis has been applied extensively to image processing and interpretation in nuclear cardiology to improve disease diagnosis and risk stratification. This is Part 2 of a two-part continuing medical education article, which will review the potential clinical role for emerging quantitative analysis tools. The article will describe advanced methods for quantifying dyssynchrony, ventricular function and perfusion, and hybrid imaging analysis. This article discusses evolving methods to measure myocardial blood flow with positron emission tomography and single-photon emission computed tomography. Novel quantitative assessments of myocardial viability, microcalcification and in patients with cardiac sarcoidosis and cardiac amyloidosis will also be described. Lastly, we will review the potential role for artificial intelligence to improve image analysis, disease diagnosis, and risk prediction. The potential clinical role for all these novel techniques will be highlighted as well as methods to optimize their implementation.

Combined brain/heart magnetic resonance imaging in antiphospholipid syndrome-two sides of the same coin

Antiphospholipid syndrome (APS) is an autoimmune disorder characterized by arterial, venous, and/or small vessel thrombosis, pregnancy morbidity, and persistently elevated levels of antiphospholipid antibodies (aPL). Cardiovascular disease (CVD) in APS can present as heart valvular disease (HVD), macro-micro-coronary artery disease (CAD), myocardial dysfunction, cardiac thrombi, or pulmonary hypertension. Brain disease presents as stroke or transient ischemic attack (TIA) and less frequently as cerebral venous thrombosis, seizures, cognitive dysfunction, multiple sclerosis (MS)-like syndrome, or chorea. Infarcts and focal white matter hyperenhancement are the commonest brain (MRI) abnormalities, while myocardial ischemia/fibrosis, valvular stenosis/regurgitation, or cardiac thrombi are the main abnormalities detected by cardiovascular magnetic resonance. This review aims to present the existing evidence on brain/heart involvement and their interrelationship in APS and the role of brain/heart MRI in their evaluation. Embolic brain disease, due to HVD, CAD, and/or cardiac thrombus, or brain hypo-perfusion, due to myocardial dysfunction, are among the main brain/heart interactions in APS and they are considered determinants of morbidity and mortality. Currently, there is no evidence to support the use of combined brain/heart MRI in asymptomatic APS patients. Until more data will be available, this approach may be considered in APS patients at high risk for CVD/stroke, such as systemic lupus erythematosus with high-risk aPL profile or high scores in CVD risk prediction models; APS patients with HVD/thrombus, CAD, or heart failure; those with classic and non-criteria neurologic APS manifestations (seizures, cognitive dysfunction, MS-like syndrome); or with aggressive multi-organ disease. Key Points • Cardiovascular disease (CVD) in antiphospholipid syndrome (APS) can present as heart valvular disease (HVD), macro-micro-coronary artery disease (CAD), myocardial dysfunction, cardiac thrombi, or pulmonary hypertension. • Brain disease presents as stroke or transient ischemic attack (TIA), and less frequently as cerebral venous thrombosis, seizures, cognitive dysfunction, and multiple sclerosis (MS). • A combined brain/heart MRI may be considered in APS patients at high risk for CVD/stroke, such as systemic lupus erythematosus with high-risk aPL profile or high scores in CVD risks; APS patients with HVD/thrombus, CAD, or heart failure; those with classic and non-criteria neurologic APS manifestations (seizures, cognitive dysfunction, MS-like syndrome); or with aggressive multi-organ disease.

Quantitative clinical nuclear cardiology, part 2: Evolving/emerging applications

Quantitative analysis has been applied extensively to image processing and interpretation in nuclear cardiology to improve disease diagnosis and risk stratification. This is Part 2 of a two-part continuing medical education article, which will review the potential clinical role for emerging quantitative analysis tools. The article will describe advanced methods for quantifying dyssynchrony, ventricular function and perfusion, and hybrid imaging analysis. This article discusses evolving methods to measure myocardial blood flow with positron emission tomography and single-photon emission computed tomography. Novel quantitative assessments of myocardial viability, microcalcification and in patients with cardiac sarcoidosis and cardiac amyloidosis will also be described. Lastly, we will review the potential role for artificial intelligence to improve image analysis, disease diagnosis, and risk prediction. The potential clinical role for all these novel techniques will be highlighted as well as methods to optimize their implementation. (J Nucl Cardiol 2020).

A tale of two technologies: Can nuclear cardiology survive the emergence of cardiac CT the seventeenth annual Mario S. Verani lectureship

The Mario S. Verani Lectureship has traditionally been an opportunity for presenters to reflect on the state of nuclear cardiology in clinical practice and expound on new innovations in the field. Mario Verani was a visionary who embraced change and, as a cardiologist, sought to define where other cardiac imaging techniques might complement nuclear cardiology for improving patient care. Over the last decade, nuclear cardiology and cardiac computed tomography (CT) have developed in parallel with both expanding beyond the evaluation of coronary artery disease. However, many consider cardiac CT a formidable threat to nuclear cardiology due to pivotal technical innovations and its subsequent exponential growth in recent years. It is only fitting that this year's lectureship explore the relative value of both techniques in evaluating and managing cardiac disease, their relative strengths and weaknesses, and the potential value of combining nuclear cardiology and cardiac CT imaging for enhancing patient management. To Mario, my mentor, colleague for over 20 years and friend, this lectureship is truly in honor and remembrance of you.

Cardiac Amyloidosis: Current Diagnostic Strategies Using Multimodality Imaging

Amyloidosis is a systemic disorder in which abnormal amyloid proteins deposit in body organs, leading to organ dysfunction and death. Cardiac amyloid deposition, causing a sort of restrictive cardiomyopathy and associated with increased risk of mortality. Most cases of cardiac amyloidosis are of either light chain or transthyretin type. Early and accurate diagnosis of cardiac amyloidosis may improve outcomes. However, diagnosis requires systematic approach including electrocardiography and biomarkers when encountered suspicious candidate. Diagnosis by multimodality noninvasive imaging have been substantially studied and established for differentiation from subtypes. Recent advance in the treatment of amyloidosis offers therapeutic monitoring and prognosis.

Impact of International Atomic Energy Agency support to the development of nuclear cardiology in low-and-middle-income countries: Case of Latin America and the Caribbean

Cardiovascular diseases (CVDs) are the leading cause of death in Latin America and the Caribbean (LAC) region as well as worldwide. Lifestyle, nutritional habits and the upsurge of obesity have contributed to the increase in the prevalence of CVDs in the region. The role of nuclear cardiology in the management of patients with CVDs is well established. Particularly, myocardial perfusion imaging is widely used in LAC countries and has been increasingly integrated into the healthcare systems in the region for the diagnosis of coronary artery disease, risk stratification and to guide patient management. In its role to support countries around the world to address their health needs through the peaceful applications of nuclear techniques, the International Atomic Energy Agency (IAEA) has provided assistance to the LAC region for the establishment and strengthening of the nuclear cardiology practice. To that extent, the IAEA provides support in building capacities of multidisciplinary teams of professionals, the provision of medical equipment and the promotion of communication and exchange of knowledge among the different stakeholders. In addition, the IAEA encourages the participation of nuclear medicine centers in international multi-center research studies. In this paper, we present some of the projects through which the IAEA has supported the LAC region, including regional technical cooperation projects and coordinated research projects related to cardiology within the current multimodality approach to cardiac imaging.

Determining post-test risk in a national sample of stress nuclear myocardial perfusion imaging reports: Implications for natural language processing tools

BACKGROUND

Reporting standards promote clarity and consistency of stress myocardial perfusion imaging (MPI) reports, but do not require an assessment of post-test risk. Natural Language Processing (NLP) tools could potentially help estimate this risk, yet it is unknown whether reports contain adequate descriptive data to use NLP.

METHODS

Among VA patients who underwent stress MPI and coronary angiography between January 1, 2009 and December 31, 2011, 99 stress test reports were randomly selected for analysis. Two reviewers independently categorized each report for the presence of critical data elements essential to describing post-test ischemic risk.

RESULTS

Few stress MPI reports provided a formal assessment of post-test risk within the impression section (3%) or the entire document (4%). In most cases, risk was determinable by combining critical data elements (74% impression, 98% whole). If ischemic risk was not determinable (25% impression, 2% whole), inadequate description of systolic function (9% impression, 1% whole) and inadequate description of ischemia (5% impression, 1% whole) were most commonly implicated.

CONCLUSIONS

Post-test ischemic risk was determinable but rarely reported in this sample of stress MPI reports. This supports the potential use of NLP to help clarify risk. Further study of NLP in this context is needed.

Intersoftware variability impacts classification of cardiac PET exams

BACKGROUND

Myocardial perfusion imaging (MPI) with 82Rb PET/CT is increasingly utilized in the evaluation of coronary artery disease with high diagnostic accuracy. Various softwares for data processing have been developed over the years with conflicting data regarding their reproducibility. In this study, we compared the quantitative results of myocardial perfusion and exam classification from three different softwares.

METHODS

Data from consecutive patients who have undergone rest/stress 82Rb PET/CT MPI at the Royal Brompton & Harefield Trust, London, were analyzed. All data were processed using the Corridor 4DM (Invia, Ann Arbor, Michigan, USA), QPET (Cedars-Sinai, Los Angeles, California, USA), and SyngoMBF (Siemens Healthineers, Erlangen, Germany). The software packages addressed Lortie tracer kinetic model and region of interest (ROI) extraction correction option.

STATISTICS

A repeated-measures ANOVA with a Greenhouse-Geisser correction was performed with post hoc tests using Bonferroni correction. For intersoftware variability, Pearson correlation and intraclass correlation coefficients (ICC) were calculated. Bland-Altman assessed limit of agreement. Cohen's Kappa assessed agreement in the classification of exams as normal or abnormal using an MFR cut-off value of 2.0. A P value of less than 0.05 was considered statistically significant.

RESULTS

Data from 55 patients were analyzed. The mean values of myocardial blood flow (MBF) and myocardial perfusion reserve (MFR) were statistically significantly different among the softwares (P < 0.05). Corridor4DM had considerably lower values of MFR and classified a more substantial number of exams as abnormal (MFR: 2.21 ± 0.7, 2.4 ± 0.8, and 1.98 ± 0.8; and 18, 15, and 31 exams were abnormal for Syngo, QPET, and Corridor4DM, respectively). Accordingly, kappa agreement was moderate for Syngo vs QPET (k > 0.5), but minimal for Corridor4DM in comparison to its pairs (k < 0.4).

CONCLUSION

Users should be cautious when using different software interchangeably as systematic differences amongst them may introduce more extensive quantitative variation which could be clinically significant.

How variable are the volumetric measurements from gated perfusion SPECT when a one-day stress-rest protocol is used?

BACKGROUND

Using myocardial perfusion scintigraphy (MPS), an increase in left ventricular (LV) volumes or a decrease in ejection fraction (EF) from rest to stress may be clinically important. The variation in these measures between the low-dose stress acquisition and high-dose rest acquisition in a one-day stress-rest protocol has not been established. We assessed the reproducibility of gated volumetric indices between stress and rest and the normal variation in ungated TID ratio for a one-day stress-rest 99mTc-tetrofosmin protocol.

METHODS

Two thousand and one hundred and fifty eight (2158) 99mTc-tetrofosmin MPS patient studies were analyzed retrospectively. Studies were excluded for incomplete data, significant technical difficulties, or (for gated analysis but not for analysis of TID ratio) if the LV EF was > 75%. An analysis of gated data was undertaken to establish the reproducibility of ventricular volumes and EF between stress and rest scans. Ungated volume data were analyzed to determine the confidence limits of TID ratio according to ventricular volume.

RESULTS

Gated data were analyzed for 621 patients without inducible hypoperfusion. Mean EF at rest was slightly higher than after stress (62.4% ± 10.3% vs 61.2% ± 10.4%, P < 0.001), and the standard deviation of the difference was 5.2% (95% CI 4.9% to 5.5%). Ungated volumes were available for 992 non-ischaemic patients. The upper 95% CI for TID ratio was 1.23. This increased from 1.20 to 1.37 between the highest and lowest deciles of rest ungated volume.

CONCLUSION

Using a one-day stress-rest 99mTc-tetrofosmin protocol, a fall in LV EF between rest and stress of > 11.6% or a TID ratio of > 1.23 is likely to be clinically reliable. The upper limit of normal for TID ratio needs to be increased for patients with small LV chamber volumes.

Cardiac sympathetic innervation scintigraphy with 123I-meta-iodobenzylguanidine. Basis, protocols and clinical applications in Cardiology

Imaging of cardiac sympathetic innervation is only possible by nuclear cardiology techniques and its assessment is key in the evaluation of and decision-making for patients with cardiac sympathetic impairment. This review includes the basis of cardiac sympathetic scintigraphy with ¹²³I-meta-iodobenzylguanidine (¹²³I-MIBG), recommended protocols, patient preparation, image acquisition and quantification, reproducibility, dosimetry, etc., and also the clinical indications for cardiac patients, mainly with regard to heart failure, arrhythmia, coronary artery disease, cardiotoxicity, including its contribution to establishing the indication for and monitoring the response to implantable cardiac devices, pharmacological treatment, heart transplantation and other.

The need for standardization of nuclear cardiology reporting and data system (NCAD-RADS): Learning from coronary artery disease (CAD), breast imaging (BI), liver imaging (LI), and prostate imaging (PI) RADS

Newer structured reporting manners, the reporting and data system (RADS), have made vast steps in improving standardized and structured reporting, allowing better communication between radiologists and referring providers. This has been implemented in several fields: breast (BI-RADS), lung (Lung-RADS), liver (LI-RADS), thyroid (TI-RADS), prostate (PI-RADS), and in cardiovascular radiology (CAD-RADS). The field of nuclear cardiology began its efforts of standardization years ago; however, a widespread standardized reporting structure has not yet been adopted. Such an approach in nuclear cardiology, the nuclear cardiology reporting and data system (NCAD-RADS), will assist radiologists and treating clinicians in conveying and understanding reports and determining the appropriate next steps in management. By linking explicit findings to defined recommendations, patients will receive more consistent and appropriate care.

Ability of artificial intelligence to diagnose coronary artery stenosis using hybrid images of coronary computed tomography angiography and myocardial perfusion SPECT

BACKGROUND

Detecting culprit coronary arteries in patients with ischemia using only myocardial perfusion single-photon emission computed tomography (SPECT) can be challenging. This study aimed to improve the detection of culprit regions using an artificial neural network (ANN) to analyze hybrid images of coronary computed tomography angiography (CCTA) and myocardial perfusion SPECT.

METHODS

This study enrolled 59 patients with stable coronary artery disease (CAD) who had been assessed by coronary angiography within 60 days of myocardial perfusion SPECT. Two nuclear medicine physicians interpreted the myocardial perfusion SPECT and hybrid images with four grades of confidence, then drew regions on polar maps to identify culprit coronary arteries. The gold standard was determined by the consensus of two other nuclear cardiology specialist based on coronary angiography findings and clinical information. The ability to detect culprit coronary arteries was compared among experienced nuclear cardiologists and the ANN. Receiver operating characteristics (ROC) curves were analyzed and areas under the ROC curves (AUC) were determined.

RESULTS

Using hybrid images, observer A detected CAD in the right (RCA), left anterior descending (LAD), and left circumflex (LCX) coronary arteries with 83.6%, 89.3%, and 94.4% accuracy, respectively and observer B did so with 72.9%, 84.2%, and 89.3%, respectively. The ANN was 79.1%, 89.8%, and 89.3% accurate for each coronary artery. Diagnostic accuracy was comparable between the ANN and experienced nuclear medicine physicians. The AUC was significantly improved using hybrid images in the RCA region (observer A: from 0.715 to 0.835, p = 0.0031; observer B: from 0.771 to 0.843, p = 0.042). To detect culprit coronary arteries in perfusion defects of the inferior wall without using hybrid images was problematic because the perfused areas of the LCX and RCA varied among individuals.

CONCLUSIONS

Hybrid images of CCTA and myocardial perfusion SPECT are useful for detecting culprit coronary arteries. Diagnoses using artificial intelligence are comparable to that by nuclear medicine physicians.

Improving compliance with Intersocietal Accreditation Commission (IAC) reporting standards: A serial comparison of 523 labs over seven years

BACKGROUND

The aim of this study was to evaluate reporting compliance of laboratories applying for serial accreditation by the Intersocietal Accreditation Commission (IAC) and compare compliance based on laboratory characteristics.

METHODS

All laboratories applying for IAC accreditation for the first time in 2008 and then twice more (2011-2014) were evaluated for compliance with 18 reporting elements. The elements were ranked into three severity groups (high/moderate/low).

RESULTS

Reports from 523 laboratories were evaluated. The percentage of laboratories with reporting issues by cycle was 66.2% for cycle 1, 36.7% for cycle 2, and 43.8% for cycle 3 (p < .001). For most of the 18 elements, there was a significant decrease in the percentage of labs with issues. Less moderate and high severity errors were seen over time. Also, the mean non-compliant elements per laboratory decreased from 5.78 ± 2.72 at cycle 1, down to 1.25 ± 1.77 at cycle 3.

CONCLUSIONS

In facilities applying for 3 consecutive IAC accreditation cycles, reporting compliance with IAC Standards improved between cycles 1-2 and 1-3. No significant improvement occurred between cycles 2-3. Although the quality of reports improved overall, problems remain in quantifying myocardial perfusion defects, documenting report approval date, and integrating stress and imaging reports.

Improved compliance with reporting standards: A retrospective analysis of Intersocietal Accreditation Commission Nuclear Cardiology Laboratories

BACKGROUND

In 2011, Tilkemeier et al reported significant nuclear cardiology laboratory noncompliance with reporting standards. The aim of this study was to identify and examine noncompliant reporting elements with the Intersocietal Accreditation Commission Nuclear/PET (IAC) Reporting Standards and to compare compliance between 2008 and 2014.

METHODS

This was a retrospective study of compliance with 18 reporting elements utilizing accreditation findings from all laboratories applying for accreditation in 2008 and 2014.

RESULTS

1816 labs applying for initial or subsequent accreditation were analyzed for compliance. The mean reporting noncompliance per lab decreased from 2008 to 2014 (2.48 ± 2.67 to 1.24 ± 1.79, P < .001). Noncompliance decreased across lab types, labs with Certification Board of Nuclear Cardiology physicians on staff, and by geographic region (P < .001). Overall severity of reporting issues decreased. Facilities with compliant reports increased from 35.0% in 2008 to 57.1% in 2014 (P < .001).

CONCLUSION

Continuing medical education, accreditation, and other instructional activities aimed at improving nuclear cardiology reporting appear to have made a positive impact over time with the number and severity of noncompliance decreased. More labs are now compliant with the IAC Standards and, thus, reporting guidelines. However, the need for continued educational efforts remains.

Artificial neural network retrained to detect myocardial ischemia using a Japanese multicenter database

Purpose

An artificial neural network (ANN) has been applied to detect myocardial perfusion defects and ischemia. The present study compares the diagnostic accuracy of a more recent ANN version (1.1) with the initial version 1.0.

Methods

We examined 106 patients (age, 77 ± 10 years) with coronary angiographic findings, comprising multi-vessel disease (≥ 50% stenosis) (52%) or old myocardial infarction (27%), or who had undergone coronary revascularization (30%). The ANN versions 1.0 and 1.1 were trained in Sweden (n = 1051) and Japan (n = 1001), respectively, using ^99mTc-methoxyisobutylisonitrile myocardial perfusion images. The ANN probabilities (from 0.0 to 1.0) of stress defects and ischemia were calculated in candidate regions of abnormalities. The diagnostic accuracy was compared using receiver-operating characteristics (ROC) analysis and the calculated area under the ROC curve (AUC) using expert interpretation as the gold standard.

Results

Although the AUC for stress defects was 0.95 and 0.93 (p = 0.27) for versions 1.1 and 1.0, respectively, that for detecting ischemia was significantly improved in version 1.1 (p = 0.0055): AUC 0.96 for version 1.1 (sensitivity 87%, specificity 96%) vs. 0.89 for version 1.0 (sensitivity 78%, specificity 97%). The improvement in the AUC shown by version 1.1 was also significant for patients with neither coronary revascularization nor old myocardial infarction (p = 0.0093): AUC = 0.98 for version 1.1 (sensitivity 88%, specificity 100%) and 0.88 for version 1.0 (sensitivity 76%, specificity 100%). Intermediate ANN probability between 0.1 and 0.7 was more often calculated by version 1.1 compared with version 1.0, which contributed to the improved diagnostic accuracy. The diagnostic accuracy of the new version was also improved in patients with either single-vessel disease or no stenosis (n = 47; AUC, 0.81 vs. 0.66 vs. p = 0.0060) when coronary stenosis was used as a gold standard.

Conclusion

The diagnostic ability of the ANN version 1.1 was improved by retraining using the Japanese database, particularly for identifying ischemia.

Diagnostic accuracy of an artificial neural network compared with statistical quantitation of myocardial perfusion images: a Japanese multicenter study

PURPOSE

Artificial neural networks (ANN) might help to diagnose coronary artery disease. This study aimed to determine whether the diagnostic accuracy of an ANN-based diagnostic system and conventional quantitation are comparable.

METHODS

The ANN was trained to classify potentially abnormal areas as true or false based on the nuclear cardiology expert interpretation of 1001 gated stress/rest 99mTc-MIBI images at 12 hospitals. The diagnostic accuracy of the ANN was compared with 364 expert interpretations that served as the gold standard of abnormality for the validation study. Conventional summed stress/rest/difference scores (SSS/SRS/SDS) were calculated and compared with receiver operating characteristics (ROC) analysis.

RESULTS

The ANN generated a better area under the ROC curves (AUC) than SSS (0.92 vs. 0.82, p < 0.0001), indicating better identification of stress defects. The ANN also generated a better AUC than SDS (0.90 vs. 0.75, p < 0.0001) for stress-induced ischemia. The AUC for patients with old myocardial infarction based on rest defects was 0.97 (0.91 for SRS, p = 0.0061), and that for patients with and without a history of revascularization based on stress defects was 0.94 and 0.90 (p = 0.0055 and p < 0.0001 vs. SSS, respectively). The SSS/SRS/SDS steeply increased when ANN values (probability of abnormality) were >0.80.

CONCLUSION

The ANN was diagnostically accurate in various clinical settings, including that of patients with previous myocardial infarction and coronary revascularization. The ANN could help to diagnose coronary artery disease.

Nuclear cardiology practice in Spain

BACKGROUND

In Spain, nuclear cardiology (NC) procedures represent the second most frequently performed studies in nuclear medicine (NM) centers.

METHODS

The NC Working Group of the Spanish Society of Nuclear Medicine and Molecular Imaging invited NM departments across the country to answer an online questionnaire regarding 2014 activity.

RESULTS

Data on 40,161 patients from 42 centers were collected. The responding public centers served 39% of Spain´s population. The estimated NC activity for public hospitals was 2 studies/1,000 population/year. Of all the NC procedures, 69% were SPECT myocardial perfusion imaging (MPI), 17% equilibrium ventriculography, 12% 18F-FDG PET, 1.3% first pass ventriculography, and <1% innervation and amyloidosis imaging, respectively. The most frequent NC study was a 99mTc tracer, exercise, 2-day MPI ECG-gated SPECT ordered by a cardiologist for diagnosis in an outpatient with 21 days of mean waiting time, the stress phase being supervised by both a cardiologist and a NM physician, with a NM physician writing a complete report.

CONCLUSIONS

A major challenge for NC in Spain is the gradual adoption of high-sensitivity, low-dose-dedicated cardiac SPECT cameras and the broadening of cardiac PET utilization with more cameras, and the availability of MPI tracers alongside the viability/inflammation setup.

Opportunities for improvement on current nuclear cardiology practices and radiation exposure in Latin America: Findings from the 65-country IAEA Nuclear Cardiology Protocols cross-sectional Study (INCAPS)

BACKGROUND

Comparison of Latin American (LA) nuclear cardiology (NC) practice with that in the rest of the world (RoW) will identify areas for improvement and lead to educational activities to reduce radiation exposure from NC.

METHODS AND RESULTS

INCAPS collected data on all SPECT and PET procedures performed during a single week in March-April 2013 in 36 laboratories in 10 LA countries (n = 1139), and 272 laboratories in 55 countries in RoW (n = 6772). Eight "best practices" were identified a priori and a radiation-related Quality Index (QI) was devised indicating the number used. Mean radiation effective dose (ED) in LA was higher than in RoW (11.8 vs 9.1 mSv, p < 0.001). Within a populous country like Brazil, a wide variation in laboratory mean ED was found, ranging from 8.4 to 17.8 mSv. Only 11% of LA laboratories achieved median ED <9 mSv, compared to 32% in RoW (p < 0.001). QIs ranged from 2 in a laboratory in Mexico to 7 in a laboratory in Cuba. Three major opportunities to reduce ED for LA patients were identified: (1) more laboratories could implement stress-only imaging, (2) camera-based methods of ED reduction, including prone imaging, could be more frequently used, and (3) injected activity of 99mTc could be adjusted reflecting patient weight/habitus.

CONCLUSIONS

On average, radiation dose from NC is higher in LA compared to RoW, with median laboratory ED <9 mSv achieved only one third as frequently as in RoW. Opportunities to reduce radiation exposure in LA have been identified and guideline-based recommendations made to optimize protocols and adhere to the "as low as reasonably achievable" (ALARA) principle.

Assessment of cardiovascular impairment in obese patients: Limitations and troubleshooting of available imaging tools

The prevalence and severity of obesity have increased over recent decades, reaching worldwide epidemics. Obesity is associated to coronary artery disease and other risk factors, including hypertension, heart failure and atrial fibrillation, which are all increased in the setting of obesity. Several noninvasive cardiac imaging modalities, such as echocardiography, cardiac computed tomography, magnetic resonance and cardiac gated single-photon emission computed tomography, are available in assessing coronary artery disease and myocardial dysfunction. Yet, in patients with excess adiposity the diagnostic accuracy of these techniques may be limited due to some issues. In this review, we analyze challenges and possibilities to find the optimal cardiac imaging approach to obese population.

Evaluation of Cadmium-Zinc-Telluride Detector-based Single-Photon Emission Computed Tomography for Nuclear Cardiology: a Comparison with Conventional Anger Single-Photon Emission Computed Tomography

Purpose

The differences in performance between the cadmium-zinc-telluride (CZT) camera or collimation systems and conventional Anger single-photon emission computed tomography (A-SPECT) remain insufficient from the viewpoint of the user. We evaluated the performance of the D-SPECT (Spectrum Dynamics, Israel) system to provide more information to the cardiologist or radiological technologist about its use in the clinical field.

Materials and Methods

This study evaluated the performance of the D-SPECT system in terms of energy resolution, detector sensitivity, spatial resolution, modulation transfer function (MTF), and collimator resolution in comparison with that of A-SPECT (Bright-View, Philips, Japan). Energy resolution and detector sensitivity were measured for Tc-99m, I-123, and Tl-201. The SPECT images produced by both systems were evaluated visually using the anthropomorphic torso phantom.

Results

The energy resolution of D-SPECT with Tc-99m and I-123 was approximately two times higher than that of A-SPECT. The detector sensitivity of D-SPECT was higher than that of A-SPECT (Tc-99m: 4.2 times, I-123: 2.2 times, and Tl-201: 5.9 times). The mean spatial resolution of D-SPECT was two times higher than that of A-SPECT. The MTF of D-SPECT was superior to that of the A-SPECT system for all frequencies. The collimator resolution of D-SPECT was lower than that of A-SPECT; however, the D-SPECT images clearly indicated better spatial resolution than the A-SPECT images.

Conclusion

The energy resolution, detector sensitivity, spatial resolution, and MTF of D-SPECT were superior to those of A-SPECT. Although the collimator resolution was lower than that of A-SPECT, the D-SPECT images were clearly of better quality.

Current status of nuclear cardiology practice in Latin America and the Caribbean

The burden of cardiovascular diseases (CVDs) in the world is ever growing. They represent the first cause of death worldwide and in Latin America. Nuclear cardiology has a well-established role in the management of patient with CVDs and is being increasingly integrated into the healthcare systems in the region. However, there remains variability as to the infrastructure available across the countries, in terms of existing technology, radiopharmaceuticals, and human resources. The approximate number of gamma (γ) cameras in the region is 1348, with an average of 2.25 per million population; Argentina and Brazil having the largest number. Nearly 80% of the existing cameras are single-photon emission tomography (SPECT), of which 8% are hybrid SPECT-CT systems. Positron emission tomography technology is steadily increasing, and currently, there is an average of 0.25 scanners per million inhabitants, indicating that there is a potential to expand the capacities in order to cover the needs. Four countries have nuclear reactors for research purposes, which allow the production of technetium-99 m (Argentina, Chile, Mexico and Peru), while four (Argentina, Brazil, Cuba, and Mexico) assemble 99Mo-99mTc generators. As for the nuclear cardiology studies, about 80% of studies performed are gated SPECT myocardial perfusion imaging; less than 10% are multi-gated acquisition (mainly for evaluation of cardiac toxicity in cancer patients), and the other 10% correspond to other types of studies, such as viability detection, and adrenergic innervation studies with 123I-MIBG. Physical stress is preferred, when possible, based on the clinical condition of the patient. Regarding human resources, there is an average of 1.1 physicians and 1.3 technologists per γ camera, with 0.1 medical physicists and 0.1 radiopharmacists per center in the region. The future of nuclear cardiology in Latin America and the Caribbean is encouraging, with great potential and possibilities for growth. National, regional, and international cooperation including support from scientific societies and organizations such as International Atomic Energy Agency, American Society of Nuclear Cardiology, and Latin American Association of Biology and Nuclear Medicine Societies, as well as governmental commitment are key factors for the development of the specialty. A multimodality approach in cardiac imaging will contribute to a better management of patients with CVDs.

Radionuclide Imaging Applications in Cardiomyopathies and Heart Failure

Multiple epidemiological factors including population aging and improved survival after acute coronary syndromes have contributed to a heart failure (HF) prevalence in the USA in epidemic proportions. In the absence of transplantation, HF remains a progressive disease with poor prognosis. The structural and functional abnormalities of the myocardium in HF can be assessed by various radionuclide imaging techniques. Radionuclide imaging may be uniquely suited to address several important clinical questions in HF such as identifying etiology and guiding the selection of patients for coronary revascularization. Newer approaches such as autonomic innervation imaging, phase analysis for synchrony assessment, and other molecular imaging techniques continue to expand the applications of radionuclide imaging in HF. In this manuscript, we review established and evolving applications of radionuclide imaging for the diagnosis, risk stratification, and management of HF.

Nuclear cardiology practice and associated radiation doses in Europe: results of the IAEA Nuclear Cardiology Protocols Study (INCAPS) for the 27 European countries

Purpose

Nuclear cardiology is widely used to diagnose coronary artery disease and to guide patient management, but data on current practices, radiation dose-related best practices, and radiation doses are scarce. To address these issues, the IAEA conducted a worldwide study of nuclear cardiology practice. We present the European subanalysis.

Methods

In March 2013, the IAEA invited laboratories across the world to document all SPECT and PET studies performed in one week. The data included age, gender, weight, radiopharmaceuticals, injected activities, camera type, positioning, hardware and software. Radiation effective dose was calculated for each patient. A quality score was defined for each laboratory as the number followed of eight predefined best practices with a bearing on radiation exposure (range of quality score 0 – 8). The participating European countries were assigned to regions (North, East, South, and West). Comparisons were performed between the four European regions and between Europe and the rest-of-the-world (RoW).

Results

Data on 2,381 European patients undergoing nuclear cardiology procedures in 102 laboratories in 27 countries were collected. A cardiac SPECT study was performed in 97.9 % of the patients, and a PET study in 2.1 %. The average effective dose of SPECT was 8.0 ± 3.4 mSv (RoW 11.4 ± 4.3 mSv; P < 0.001) and of PET was 2.6 ± 1.5 mSv (RoW 3.8 ± 2.5 mSv; P < 0.001). The mean effective doses of SPECT and PET differed between European regions (P < 0.001 and P = 0.002, respectively). The mean quality score was 6.2 ± 1.2, which was higher than the RoW score (5.0 ± 1.1; P < 0.001). Adherence to best practices did not differ significantly among the European regions (range 6 to 6.4; P = 0.73). Of the best practices, stress-only imaging and weight-adjusted dosing were the least commonly used.

Conclusion

In Europe, the mean effective dose from nuclear cardiology is lower and the average quality score is higher than in the RoW. There is regional variation in effective dose in relation to the best practice quality score. A possible reason for the differences between Europe and the RoW could be the safety culture fostered by actions under the Euratom directives and the implementation of diagnostic reference levels. Stress-only imaging and weight-adjusted activity might be targets for optimization of European nuclear cardiology practice.

Cardiac involvement in antiphospholipid syndrome: The diagnostic role of noninvasive cardiac imaging

OBJECTIVES

The antiphospholipid syndrome (APS) is an autoimmune disorder of acquired hypercoagulability characterized by vascular thrombosis, increased pregnancy morbidity, and elevated levels of antiphospholipid antibodies. Cardiac involvement in APS may be presented as heart valve disease affecting approximately a third of patients or less frequently as intracardial thombosis, pulmonary hypertension, right or left ventricular dysfunction, micro-vascular thrombosis, coronary artery, or micro-vascular disease with overt or silent clinical presentation.

METHODS

Noninvasive cardiovascular imaging plays a crucial role in the evaluation of heart involvement in APS. Transthoracic or transoesophageal echocardiography enable early, accurate diagnosis and severity assessment of HVD as well as of ventricular dysfunction and pulmonary hypertension. Studies by echocardiography and nuclear imaging have detected abnormalities in myocardial perfusion in approximately 30% of primary APS. CT scan is the technique of choice for the assessment of pulmonary embolism and can effectively detect intracardiac thrombi. Myocardial perfusion defects have been detected by 13N-ammonia PET in 40% of APS. Cardiovascular magnetic resonance (CMR) has identified an unexpectedly high prevalence of occult myocardial scarring and endomyocardial fibrosis in APS, and is the technique of choice, if quantification of heart valve disease and stress myocardial perfusion-fibrosis is needed.

RESULTS

Noninvasive, nonradiating imaging techniques, such as echocardiography and CMR are superior to CT or nuclear techniques and are of great value for the diagnosis and follow-up of both clinically overt and silent cardiac disease in APS.

CONCLUSIONS

The high incidence of cardiac involvement in APS demands early diagnosis/treatment and multimodality cardiovascular imaging is of great importance.

Optimization of OSEM parameters in myocardial perfusion imaging reconstruction as a function of body mass index: a clinical approach

OBJECTIVE

The present study is aimed at contributing to identify the most appropriate OSEM parameters to generate myocardial perfusion imaging reconstructions with the best diagnostic quality, correlating them with patients' body mass index.

MATERIALS AND METHODS

The present study included 28 adult patients submitted to myocardial perfusion imaging in a public hospital. The OSEM method was utilized in the images reconstruction with six different combinations of iterations and subsets numbers. The images were analyzed by nuclear cardiology specialists taking their diagnostic value into consideration and indicating the most appropriate images in terms of diagnostic quality.

RESULTS

An overall scoring analysis demonstrated that the combination of four iterations and four subsets has generated the most appropriate images in terms of diagnostic quality for all the classes of body mass index; however, the role played by the combination of six iterations and four subsets is highlighted in relation to the higher body mass index classes.

CONCLUSION

The use of optimized parameters seems to play a relevant role in the generation of images with better diagnostic quality, ensuring the diagnosis and consequential appropriate and effective treatment for the patient.

Risk stratification of patients with chronic heart failure using cardiac iodine-123 metaiodobenzylguanidine imaging: incremental prognostic value over right ventricular ejection fraction

Aims

Right ventricular (RV) systolic dysfunction has been shown to be an independent predictor of clinical outcome in patients with chronic heart failure (CHF), and cardiac metaiodobenzylguanidine (MIBG) imaging also provides prognostic information. We aimed to evaluate the long‐term predictive value of combining RV systolic dysfunction and abnormal findings of cardiac MIBG imaging on outcome in CHF patients.

Methods and results

We enrolled 63 CHF outpatients with left ventricular ejection fraction (EF) <40% in a prospective cohort study. At entry, RVEF was measured by radionuclide angiography. Furthermore, cardiac MIBG imaging was performed, and the cardiac MIBG washout rate (WR) was calculated. Reduced RVEF was defined as ≤37%, and abnormal WR was defined as >27%. The study endpoint was unplanned hospitalization for worsening heart failure (WHF) and cardiac death. During a follow‐up period of 8.9 ± 4.3 years, 19 of 63 patients had unplanned hospitalization for WHF, and 19 of 63 patients had cardiac death. In multivariate analysis, both WR and RVEF were independent predictors of unplanned WHF hospitalization, while WR was also an independent predictor of cardiac death. A risk‐stratification model based on independent predictors of unplanned WHF hospitalization separated the patients into those with low (absence of the predictors), intermediate (one of the predictors), and high (two or more of the predictors) risk of unplanned WHF hospitalization (P < 0.0001) or cardiac death (P = 0.0113).

Conclusions

Cardiac MIBG imaging provides incremental value when it is used along with RV systolic dysfunction to predict clinical outcome in patients with CHF.

Current worldwide nuclear cardiology practices and radiation exposure: results from the 65 country IAEA Nuclear Cardiology Protocols Cross-Sectional Study (INCAPS)

Aims

To characterize patient radiation doses from nuclear myocardial perfusion imaging (MPI) and the use of radiation-optimizing ‘best practices’ worldwide, and to evaluate the relationship between laboratory use of best practices and patient radiation dose.

Methods and results

We conducted an observational cross-sectional study of protocols used for all 7911 MPI studies performed in 308 nuclear cardiology laboratories in 65 countries for a single week in March–April 2013. Eight ‘best practices’ relating to radiation exposure were identified a priori by an expert committee, and a radiation-related quality index (QI) devised indicating the number of best practices used by a laboratory. Patient radiation effective dose (ED) ranged between 0.8 and 35.6 mSv (median 10.0 mSv). Average laboratory ED ranged from 2.2 to 24.4 mSv (median 10.4 mSv); only 91 (30%) laboratories achieved the median ED ≤ 9 mSv recommended by guidelines. Laboratory QIs ranged from 2 to 8 (median 5). Both ED and QI differed significantly between laboratories, countries, and world regions. The lowest median ED (8.0 mSv), in Europe, coincided with high best-practice adherence (mean laboratory QI 6.2). The highest doses (median 12.1 mSv) and low QI (4.9) occurred in Latin America. In hierarchical regression modelling, patients undergoing MPI at laboratories following more ‘best practices’ had lower EDs.

Conclusion

Marked worldwide variation exists in radiation safety practices pertaining to MPI, with targeted EDs currently achieved in a minority of laboratories. The significant relationship between best-practice implementation and lower doses indicates numerous opportunities to reduce radiation exposure from MPI globally.

Significance of worsening renal function and nuclear cardiology for predicting cardiac death in patients with known or suspected coronary artery disease

BACKGROUND

Estimated glomerular filtration rates (eGFRs) at baseline are useful to determine the severity of renal function and to predict cardiac events. However, no studies aimed to demonstrate significance of eGFRs measured during follow-up and usefulness of combination with nuclear cardiology for prediction of cardiac death in patients with coronary artery disease (CAD).

METHODS

We retrospectively investigated 1739 patients with known/suspected CAD who underwent myocardial perfusion single photon emission computed tomography (SPECT), who had eGFRs measured at baseline and after one year and who underwent a three-year follow-up. The SPECT images were analyzed with the visual scoring model to estimate summed defect scores. Reduction in eGFRs (ΔeGFR) was defined as the difference between eGFRs measured after one year and at baseline. The endpoint of the follow-up was cardiac deaths within three years after the SPECT, which were identified with medical records or responses to posted questionnaires.

RESULTS

Cardiac death was observed in 54 of 1739 patients during the follow-up period (45.6±9.1 months). The multivariate Cox regression analysis showed baseline eGFRs, ΔeGFR, and summed stress scores to be significant independent variables for prediction of cardiac death. The area under receiver operating characteristic curves for detection of cardiac death was 0.677 for the baseline eGFR and 0.802 for the follow-up eGFR. Sensitivity of detection of cardiac death was significantly higher in the follow-up eGFR than in the baseline eGFR (p=0.0002). Combination of the best cut-off values, i.e. 9 for the summed stress scores and 10 for the ΔeGFR, which were suggested by receiver operating characteristic analysis, was useful for risk stratification of cardiac death both in patients with and without chronic kidney disease.

CONCLUSION

Baseline and follow-up eGFRs as well as nuclear variables are useful to predict cardiac death in patients with known/suspected CAD.