Cardiac sympathetic nervous system dysfunction is closely associated with risk of serious cardiac events in patients with heart failure (HF), including HF progression, pump-failure death, and sudden cardiac death by lethal ventricular arrhythmia. For cardiac sympathetic nervous system imaging, 123I-meta-iodobenzylguanidine (123I-MIBG) was approved by the Japanese Ministry of Health, Labour and Welfare in 1992 and has therefore been widely used since in clinical settings. 123I-MIBG was also later approved by the Food and Drug Administration (FDA) in the United States of America (USA) and it was expected to achieve broad acceptance. In Europe, 123I-MIBG is currently used only for clinical research. This review article is based on a joint symposium of the Japanese Society of Nuclear Cardiology (JSNC) and the American Society of Nuclear Cardiology (ASNC), which was held in the annual meeting of JSNC in July 2016. JSNC members and a member of ASNC discussed the standardization of 123I-MIBG parameters, and clinical aspects of 123I-MIBG with a view to further promoting 123I-MIBG imaging in Asia, the USA, Europe, and the rest of the world.
Background: Quantifying the myocardial blood flow (MBF) using 13N-ammonia or 15O-H2O position emission tomography (PET) is a gold standard method. However, PET MBF measurements can only be applied for limited population. A recent study showed a new myocardial uptake ratio (MUR) method. This approach may apply for the quantitative evaluation of the MBF and functional severity of the CAD. The purpose of the present study was to evaluate the diagnostic utility of the myocardial flow reserve (MFR) with this MUR method using a standard dual-head single-photon emission computed tomography (SPECT) camera. Methods: A total of 46 known or suspected CAD patients underwent adenosine stress dynamic planar acquisition following conventional 99mTc-sestamibi (99mTc-MIBI) SPECT. The area under the curve of aorta time-activity curve (TAC) was used to obtain the time integral of the first-pass 99mTc-MIBI count. The myocardial counts were obtained from SPECT short-axis images. MUR under stress and rest conditions was estimated and corrected with the cross calibration factor. Then, the MFR was calculated as the ratio of stress MUR to rest MUR. Results: The median MFR was significantly lower in patients with CAD than that without CAD (1.23 [IQR, 1.10-1.34] vs. 1.33 [IQR, 1.26-1.61], p<0.05). Conclusions: Patients with CAD showed significantly lower MFR using the dynamic MUR approach. Therefore, the MUR method was useful for distinguish between CAD and non-CAD patients. In this regard, MFR measurements may be useful in discerning CAD from non-CAD for the selected population.
Objective: Left ventricular mechanical dyssynchrony (LVMD) is associated with deterioration of systolic function and adverse clinical outcomes. This study investigated whether LVMD influenced subsequent cardiac events (CEs), including cardiac death, recurrent nonfatal myocardial infarction, hospitalization for heart failure, and ventricular tachycardia/ventricular fibrillation in patients with acute myocardial infarction (AMI). Methods: Two hundred and six AMI patients aged 64 ± 11 years (163 men) who underwent successful percutaneous coronary intervention between April 1998 and December 2007 were enrolled. All patients received myocardial 99mTc-sestamibi or 99mTc-tetrofosmin perfusion imaging at rest, and the total defect score was calculated as the sum of the defect scores in 17 standard myocardial segments. Indicators of left ventricular (LV) function were acquired with quantitative gated SPECT software, including the LV end-diastolic volume (LVEDV), LV end-systolic volume (LVESV), and LV ejection fraction (LVEF). Then the LVMD index was evaluated by using CardioGraf software. Results: The follow-up period was 63 ± 31 months. Cardiac events (CEs) occurred in 30 patients, including 15 patients hospitalized for congestive heart failure, 8 patients with recurrent AMI, 4 patients with ventricular tachycardia, and 3 patients with cardiac death. These patients were classified as the CE group, while the other 176 patients without CEs formed the non-CE group. According to univariate analysis with the Cox proportional hazards model, the maximum creatine kinase, frequency of multivessel disease (2-vessel or 3-vessel disease), total defect score, LVEDV, LVESV, and dyssynchrony index were all significantly higher in the CE group than the non-CE group. In contrast, LVEF and the peak ejection rate were significantly lower in the CE group than in the non-CE group. Multivariate analysis showed that multivessel disease (p=0.003) and the LVMD index (p=0.047) were independent prognostic factors for CEs. Conclusion: LVMD contributes to the risk of subsequent cardiac events in AMI patients.
Background: Gated myocardial perfusion single-photon emission computed tomography (SPECT) has been used to evaluate quantitative cardiac functional parameters using a dedicated software program. The aim of this study was to measure normal values of left ventricular (LV) functional parameters for a cardioREPO software program (cREPO) and to evaluate gender differences in these parameters. Methods: The Japanese normal database consisted of 206 99mTc-sestamibi or 99mTc-tetrofosmin myocardial perfusion SPECT images was used. The RR interval of the electrocardiogram was divided into 16 frames in the gated image. The cREPO can automatically calculate LV ejection fraction (EF), end-diastolic volume (EDV), end-systolic volume (ESV), peak filling rate, 1/3 mean filling rate (MFR), time to PFR (TTPF) as well as phase histogram parameters of 95% phase bandwidth, phase standard deviation (SD), and entropy. Results: Mean LVEF was slightly higher in females (71.7 vs. 69.6%, p=0.0018), and EDV and ESV were higher in males (92.5 vs. 70.9 mL for EDV, p<0.0001; and 27.5 vs. 19.9 mL for ESV, p<0.0001). Diastolic functions of 1/3 MFR, TTPF, and TTPF/RR interval significantly differed between males and females (1.46 vs. 1.62/sec, p=0.007; 171 vs. 153 ms, p=0.001; and 0.18 vs. 0.17, p=0.028, respectively). Gender differences were observed in 95% bandwidth (43° for males vs. 37° for females, p<0.0001), phase SD (10.6° vs. 9.2°, p<0.0001), and entropy (46% vs. 41%, p<0.0001). Conclusions: Normal mean values of LV functional parameters for cREPO were determined. These normal values for cREPO could be used as a basis for evaluation of a gated SPECT image in patients with cardiac diseases.
Purpose: The novel 3 Detector SPECT ‘GCA-9300R’ is equipped with attenuation correction algorithm of 3D-OSEM and SSPAC. The combination of this highly sensitive gamma camera with high quality techniques seems very promising concerning diagnostic value. The aim of this study is to comprehend the difference of tracer uptake in MPS under the usage of 3D-OSEM, SSPAC method compared with FBP using triple head gamma camera. Methods: We examined a total of 40 consecutive cases (20 cases for both male and females), in which conducted myocardial perfusion scans and diagnosed as no heart ischemic state. The examination was conducted under rest first 1-day protocol. Comparative analysis was conducted between FBP and 3D-OSEM (rest and stress), FBP and SSPAC (rest and stress), and FBP and prone images (stress) as well as 3D-OSEM and prone images (stress). Results: In FBP, we observed a lower count distribution in septal region, higher count distribution in apical region and apical side of the lateral region. 3D-OSEM showed slightly lower count distribution compared with FBP in the septal, lateral and a apical region. The reduction was more prominent with the males. Regarding SSPAC, in comparison with FBP, count elevations were observed in the inferior and septal regions while in the lateral and apical region the count was reduced. There was no statistically significant count difference between SSPAC and prone image in the inferior regions. Conclusion: With GCA-9300R, 3D-OSEM has the tendency toward count reduction in the septal, lateral and apical regions. On the other hand, SSPAC could reduce the count reduction in sepal and inferior regions toward FBP, and could prove to be a very helpful tool in the diagnosis of ischemia.
In recent years, advancements in diagnostic imaging modalities, such as cardiac magnetic resonance (CMR) and 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET), as well as the accumulation of cases, have allowed a more accurate diagnosis of cardiac sarcoidosis (CS). In addition, emerging cases of “isolated CS” in which no obvious lesions are present in organs other than the heart have been reported, and the clinical importance of CS has become recognized. Many issues including etiology, pathology, diagnosis, and treatment of CS remain to be solved. Considering this situation, guidelines for the diagnosis and treatment of cardiac sarcoidosis were recently updated by the Japanese Circulation Society and were published in February 2017.
Clinical researchers often need to quantify the degree of agreement, the “closeness,” between two quantitative methods of measurement taken on the same subject and same variable, either when a new or revised method is considered for use in place of an established one or when measurements are separated by time. An ideal model of agreement would capture the degree of exactly equal outcomes. Analysis should be based on differences between two methods of measurement. Inappropriate statistical methods, including correlation, e.g. Pearson’s r, are often used. But correlation, r, measures the degree of linear relationship between two variables, not the extent of agreement. A more informative and appropriate tool, the Bland and Altman (B&A) plot analysis, uses a graphical approach to present and assess differences between two measures. The differences between paired measurements are plotted on the Y-axis against the mean of the paired measures on the X-axis. The B&A chart allows for assessment of bias, both in size and consistency, over the range of measurements; it does not specify whether the agreement limits are acceptable; acceptable limits must be defined before. Additional reference lines can facilitate interpretation of the scatter plot.
Fractional flow reserve (FFR) is now accepted as the reference standard to indicate whether a stenosis is likely to be responsible for ischemia. It is generally accepted that a stenosis with an ischemic value of FFR is responsible for symptom and a worse outcome and should be revascularized, whereas lesions with a non-ischemic FFR have a more favorable prognosis and can be treated medically. Furthermore, FFR-guided revascularization strategy has been definitely proven to be better than angiography-guided strategy in pivotal landmark studies. Instantaneous wave free ratio (iFR) is another physiological index which can be obtained at rest without hyperemic stimulation. iFR is conceptually different from FFR, leading to lively scientific debate about this index. In this review article, the concept, differences and similarities of FFR and iFR are reviewed.
When you have finally completed your research, documented your findings, observations, conclusions and future considerations, the time has come to add your work to that of the larger nuclear cardiology community. But how can you share your work with other scientists? For a young physician new to the world of publishing, the task of putting together an illuminating, cohesive and yet succinct manuscript can appear daunting. Even so, the “publish or perish” imperative remains if you are to advance your career while contributing to the worldwide pool of knowledge, so try you must. Luckily, there are some concrete principles you can follow that will remove some of the mystery and, from an editorial point of view, improve your chances of having your manuscript accepted for submission. Presenting findings in a way that has the best possible chance of being accepted for publication means paying close attention to clarity, accuracy and suitability of both content, in terms of science, and presentation, in terms of language, style and format. This review will address the role that editing plays in the submission and publication process and will provide some practical approaches for improving your manuscript.
Coronary atherosclerosis with acute thrombosis is the most common cause of sudden cardiac death. Because the disruption of coronary atherosclerotic plaques triggers acute thrombosis, it is important to identify disruption-prone plaques with imaging modalities. The pathology of “plaque disruption” incudes three distinct morphologic entities: plaque rupture, plaque erosion, and calcified nodule. Currently, invasive imaging modalities such as intravascular ultrasound and intravascular optical coherence tomography can identify rupture-prone plaques, or thin-cap fibroatheromas, and calcified nodules, and unveiled that asymptomatic, multiple-plaque ruptures are a frequent complication in patients with coronary atherothrombosis. However, they cannot identify erosion-prone plaques. This article describes the morphological characteristics of coronary plaque disruptions and their possible mechanisms. In addition, the plaque imaging by nuclear medicine is discussed from a pathological viewpoint.
PET/MR is a hybrid imaging modality that enables simultaneous acquisition of PET and MR images, and fuses functional or metabolic information obtained using PET and superior soft tissue contrast acquired using MR. Although PET has mostly been used for oncologic indications, PET/MR has significant potential for evaluating cardiac diseases. 18F-fluorodeoxyglucose PET/MR can evaluate not only inflammation and myocardial glucose metabolism, but also cardiac function, tissue edema, and myocardial fibrosis, simultaneously. Furthermore, using specific PET tracers, PET/MR enables the evaluation of various cardiac diseases. Although there are several technical issues that remain to be solved, PET/MR is a key modality for evaluating the pathophysiology of cardiac diseases.
Late Gadolinium Enhanced (LGE) Cardiovascular Magnetic Resonance (CMR) imaging has a unique ability to characterize diverse mechanisms of non-ischemic myocardial injury. The pattern and extent of LGE findings have been studied across a wide range of cardiomyopathy states. To date, these collective findings provide strong justification for the use of LGE-CMR in the evaluation and prognostication of patients with Dilated, Hypertrophic, Restrictive and Inflammatory cardiomyopathies. This review article summarizes relevant studies in the field and highlights the clinical role of LGE-CMR in contemporary practice.
Background: Digital anthropomorphic phantoms have gradually gained an important role in nuclear medicine imaging. The aim of this study was to generate digital phantom models simulated with cardiac and respiratory motions and to evaluate motion-induced artifact using a quantitative software program developed with artificial intelligence (AI) technology in myocardial perfusion single-photon emission computed tomography (SPECT) images. Methods: A digital anthropomorphic torso phantom and Monte Carlo simulation program were used to generate the projection image. We prepared electrocardiographic- and respiratory-gated models with cardiac and respiratory motions in the diaphragmatic motion of 0-50 mm and chest anterior-posterior (AP) expansion of 0-30 mm. The phantoms had 99mTc radiopharmaceuticals embedded based on a normal male subject. The projection data were reconstructed with filtered back projection method. The 17-segment polar map without attenuation correction was created. Myocardial count ratio was calculated in the anterior and inferior walls to the anterolateral wall on the polar map. Results: The low myocardial perfusion distribution was clearly observed in the basal to mid anterior and inferior walls, when the diaphragmatic motion and AP expansion were increased. The anterior and inferior count ratios showed significant decrease with diaphragmatic motion (≥30 mm) compared to without diaphragmatic motion (0.71±0.05 vs. 0.76±0.06; p<0.0001, 0.67±0.04 vs. 0.69±0.04; p=0.038, respectively). The anterior and inferior motion artifacts could not be detected by the quantitative software program in the diaphragm motion of ≤20 mm and AP expansion of ≤12 mm. Conclusions: The cardiac and respiratory motion-induced artifacts were characterized as low anterior and inferior myocardial counts. Therefore, motion artifacts should be considered when we observe this sort of count decreases on the reconstructed images and polar maps. However, we could exclude the mild motion-induced artifacts by using the quantitative software program integrated with AI technology.
Diseases Discovered in Japan and the Role of Nuclear Cardiology
Triglyceride deposit cardiomyovasculopathy (TGCV) is a novel clinical entity we found in patients with severe heart failure waiting for cardiac transplantation. The probands carried genetic mutations in adipose triglyceride lipase (ATGL), which is an essential molecule for the intracellular hydrolysis of TG. Patients with TGCV showed ectopic accumulation of TG in cardiomyocytes and smooth muscle cells resulting from the abnormal intracellular metabolism of TG and its substrates, long chain fatty acids (LCFAs). Our postmortem analyses demonstrated substantial numbers of autopsied individuals with TGCV phenotype, whose expression of ATGL was conserved. These results suggest that TGCV might be difficult to diagnose in daily clinics, however be more prevalent than expected, and a possible important cause of cardiac death. This review article focuses on imaging modalities to evaluate cardiomyovascular TG accumulation of this novel disease. Data and images are shown from pathological analyses, imaging mass spectrometry, myocardial scintigraphy with a radioactive analogue for LCFA, iodine-123-β-methyl iodophenyl-pentadecanoic acid, MR spectroscopy, and CT-based TG imagings in primary TGCV patients with genetic ATGL deficiency, which is ultra-rare, but the monogenic model.
In this issue, Hirano et al. addressed a novel hypothesis for the onset of takotsubo syndrome. The authors presented the two-step energy failure hypothesis. The first step is sudden stress increase in cardiac energy demands, following the additional supply from stored triglycerides. The second step is the prolonged stunning of the ventricle due to impaired uptake of energy substrates in the myocardium. They insisted that these steps might be one of the underlying mechanisms to develop this syndrome. To understand this mechanism would be helpful as a future option for the treatment and prevention of takotsubo syndrome.
Regional Specific Disease and the Role of Nuclear Cardiology
Takotsubo cardiomyopathy (TCM) is a transient myocardial stunning, typically showing apical ballooning. Although catecholamine toxicity, vasospasm, and disturbed microcirculation have been implicated, the precise pathophysiology of TCM is unknown. We present a two-step energy failure hypothesis which could explain the clinical course and pathogenesis. Sudden stress-induced increase in cardiac energy demand of normal subjects can be compensated for by additional supply of long chain fatty acids released from triglycerides stored in adipose tissues. Subjects at high risk for TCM cannot tolerate such stress-induced energy demand/supply imbalance, which triggers initial energy failure and induces myocytes’ stunning in vulnerable mid- and apical myocardial segments. Receptor-mediated uptake for energy substrates then declines due to impairment of contraction-dependent recruitment of responsible transporters (e.g. CD36). This in turn induces the second energy failure, which prolongs the myocardial stunning. Eventually, spontaneous or therapeutic improvements in the energetics awaken the heart.
Cardiac Sarcoidosis - From the CME Session at 63rd SNMMI Annual Meeting
Abnormal uptake of 18F-fluorodeoxyglucose (FDG) in the heart on positron emission tomography (PET) was recently included in the major criteria of diagnostic guidelines for cardiac sarcoidosis (CS). The high sensitivity but great variability in specificity in the diagnosis probably due to variable preparation methodologies of FDG-PET was reported. There are three main methods which have been reported to minimize physiological FDG uptake in the normal myocardium. A low carbohydrate diet on the day before PET with an overnight fasting more than 18-h achieves almost complete suppression of myocardial FDG uptake. Use of heparin pre-injection or high-fat diet preparation may enhance the suppressive effect. Serum FFA levels before PET imaging might be a biomarker of predicting the physiological FDG uptake in the myocardium.
Sarcoidosis is a multisystem disease pathologically characterized by non-caseating granuloma. Cardiac sarcoidosis (CS) remains an important prognostic factor of sarcoidosis patients. 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) has been applied as a noninvasive tool not only for CS diagnoses but also for the evaluation of therapeutic effects and prognoses. Visual assessment is a standard method to evaluate whether the 18F-FDG uptake is physiological or active inflammation due to the CS. A semi-quantitative assessment using the standardized uptake value (SUV) is a simple method for achieving a more accurate diagnosis. A volume-based analysis has been proposed as a new marker that can provide information about the improvement or prevention of heart failure and can be used to predict a further clinical event in CS patients. This is a brief review of the objective and quantitative assessments of the magnitude and extent of CS activity with the use of 18F-FDG PET.
For patients with sarcoidosis involving organs, those with cardiac lesions have especially poor prognosis. Among sarcoidosis patients, those in Japan have higher rates of cardiac involvement of sarcoidosis (CS) than do those in other countries. Therefore, the Japanese medical community has put great efforts into managing CS patients and has developed research activities. In this regard, the Japanese Ministry of Health & Welfare (JMHW) issued CS diagnostic guidelines in 1993 and these have been widely used around the world. The Japanese Circulation Society updated its nuclear medicine guidelines in 2010 and recommended using nuclear imaging to diagnose CS. In 2012 JMHW approved insurance reimbursement for 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) and since then 18F-FDG PET has been used in clinical practice for the diagnosis of CS in Japan. In 2014 the Japanese Society of Nuclear Cardiology recommended using 18F-FDG PET imaging in the diagnosis of CS.
Sarcoidosis is a multisystem granulomatous disease of unknown etiology that is characterized by the formation of non-caseating granulomas at various sites in the body. Cardiac sarcoidosis (CS) has been underdiagnosed in the past due to a lack of imaging modalities with high sensitivity. CS may cause various symptoms including conduction disturbance, ventricular arrhythmias, cardiac dysfunction and sudden cardiac death, which account for an increased mortality rate in these patients. 18F-fluorodeoxyglucose positron emission tomography (FDG PET) and late gadolinium-enhanced cardiac magnetic resonance imaging (LGE CMR) have played important roles in the recent guidelines for the diagnosis of CS. Each one possesses its own unique abilities and can contribute to early disease detection, assessment of disease activity, response to treatment, and risk stratification. However, further studies are necessary in order to establish the standard methods for clinical application of FDG PET and CMR.
Approximately 5% of patients with sarcoidosis will have cardiac involvement clinically manifest as one or more of ventricular arrhythmias, conduction abnormalities and heart failure. Another 20% to 25% have clinically silent disease (asymptomatic cardiac involvement). There is a growing realisation that CS can be the first manifestation of sarcoidosis in any organ. In particular physicians should consider CS in patients with VT of unknown etiology and in patients aged <60 presenting with idiopathic advanced conduction system disease. Immunosuppression therapy (usually with corticosteroids) has been suggested for the treatment of clinically manifest CS despite modest data. Positron Emission Tomography (FDG-PET) imaging is often used to detect active disease and guide immunosuppression. The extent of left ventricular dysfunction seems to be the most important predictor of prognosis. Also the extent of LGE on CMR is emerging as an important prognostic factor. Patients with clinically manifest disease often need device therapy, usually with implantable cardioverter defibrillators. There are still much to be learned as regarding best practices in managing CS patients and multi-center research efforts are underway.
In patients with suspected coronary artery disease (CAD), an anatomical or functional approach can be used to guide further patient management. Functional techniques are able to assess the presence and extent of myocardial ischemia, whereas coronary computed tomography angiography (CTA) can assess the presence and extent of coronary atherosclerosis. Coronary CTA has a high sensitivity to detect obstructive CAD in patients with a low to intermediate probability and is therefore commonly used to rule out coronary atherosclerosis. To improve its specificity, novel techniques as fractional flow reserve using CT (FFRct) and CT myocardial perfusion imaging (CTP) are emerging. This review will summarize the latest trials that investigated how coronary CTA can be applied in clinical practice and compare this technique to other imaging modalities.
The purpose of this review article is to describe the essential characteristics of cardiac magnetic resonance imaging (MRI) in the evaluation of coronary artery disease in comparison with other noninvasive imaging modalities. Recently, technical advances and improvements in cardiac MRI have provoked increasing interest regarding its clinical role in the diagnosis and evaluation of coronary artery disease. Major advantages of cardiac MRI in comparison with other noninvasive imaging tests include its excellent spatial resolution and the characterization of myocardial tissue. These features allow the accurate assessment of ventricular volume and function, as well as clear delineation of infarcted tissue from normal myocardium. Further, myocardial ischemia can also be assessed by cardiac MRI upon pharmacological stress testing. In addition, coronary MR angiography has emerged as a possible alternative to X-ray angiography for visualizing the coronary arteries. The capability to perform comprehensive evaluations of ventricular function and myocardial perfusion and viability, as well as to assess the coronary anatomy, is a major strength of cardiac MRI.
Diagnostic modalities including SPECT and CT are both useful for detecting coronary artery disease. Physiological and anatomical approaches are two sides of same coin. In a twist of irony, increasing of CT angiography and decreasing of SPECT field in Japan would be associated with in appropriate coronary interventions in terms of American appropriate use criteria of coronary interventions. Quantification of perfusion abnormality and myocardial flow reserve using dedicated CZT gamma camera would make it possible to identify the patients, in whom interventions may improve the long-term prognosis. Recent publication reported that initial non-invasive diagnostic modalities (SPECT or CT) did not affect patients’ outcome. Medical economical approach should be taken into account for the selection of those two modalities in future.
While single photon emission computed tomography (SPECT) is by far the predominant modality for radionuclide myocardial perfusion imaging in the United States in 2017, there has been impressive growth in positron emission tomography (PET) and especially hybrid PET/computed tomography (CT) utilization. Advantages, clinical indications, and procedural standards have been documented by professional society publications. FDA clearances exist and payments are defined for governmental and commercial contractors. Current efforts are underway to standardize training and education for physicians and technologists who will perform PET perfusion studies, and to advance standards for performance, quality control, and reporting of myocardial blood flow quantification. Industry appears heavily invested in the future of PET perfusion, with recent FDA approval of a second Rubidium-82 generator and elution system, a new production facility capable of substantially increasing Rubidium-82 availability, and a novel fluorine-based perfusion tracer undergoing Phase 3 studies. Current paradigms appear to favor SPECT for less complicated patients who are able to exercise, and PET for more complicated or higher-risk patients who require pharmacologic stress.
Coronary artery disease (CAD) is one of the major causes of death in Japan. Fractional flow reserve with angiography is a well validated method for identifying significant focal stenosis, but is not applied for the estimation of hyperemic vasodilatory capacity in the myocardium. Coronary flow reserve (CFR) estimated from sequential myocardial perfusion images obtained by blood flow tracers and positron emission tomography (PET) is a quantitative value. CFR is regulated not only by focal stenoses but also by diffuse atherosclerosis and coronary microvascular dysfunction (CMD) in patients with CAD. Accordingly, low CFR is shown to be a strong predictor of cardiac death in combination with anatomical disease burden. Optimal medical therapies such as beta-blockers, angiotensin converting enzyme (ACE) inhibitors, statins, and medications for diabetes could increase CFR by improving CMD at the early stage of CAD. It is also important to clarify the effects of coronary revascularization for focal stenoses on CFR. This paper focuses on the application of CFR estimated by cardiac PET to the evaluation of per-patient atherosclerotic burden and microvascular dysfunction.
Assessment of physiological ischemia is recently essential for the indication of coronary revascularization; such as percutaneous coronary intervention (PCI) and coronary artery bypass graft (CABG) in patients with coronary artery disease. Moreover, quantitative assessment of myocardial flow reserve (MFR) is also getting important role for the evaluation of prognosis of heart diseases including non-ischemic cardiomyopathy. In the field of nuclear cardiology, positron emission tomography (PET) has been the only modality for the quantitative assessment of myocardial blood flow (MBF) and MFR. However, since availability of PET is much less than that of single photon emission computed tomography (SPECT) imaging, quantitative MBF/MFR assessment has been limited. Recently, high sensitivity gamma camera which equipped semiconductor detectors has been developed. It is reported that its image quality and spatial resolution are much superior to conventional Anger-type gamma camera. Moreover, since high sensitivity gamma camera consists of plural detectors, it can evaluate whole heart perfusion simultaneously. These advances make quantitative MBF/MFR analysis feasible like PET imaging. Although quantitative assessment with high sensitivity gamma camera is getting useful in clinical practice, several points; such as acquisition protocol and analysis methods, are immature compared to PET. Therefore, we have to investigate the solutions for these issues in near future for diagnostic certainty.
The 27th JSNC Annual Scientific Meeting Highlights
Cardiovascular disease (CVD) has become the main cause of death in Latin America as a consequence of the demographic, economic and social changes experienced by the region. In the last decade, there have been important improvements in nuclear cardiology (NC) practice, but there is still great heterogeneity among countries regarding availability of technology, education, and human resources. The total number of gamma cameras in the region is above 1,300, with an average of about 2.3 per million inhabitants. Nearly all cameras have SPECT capabilities, almost 10% with hybrid technology (SPECT/CT). PET technology is steadily increasing, but perfusion agents are not available at most sites. Training and education are probably the most important challenges for the development of NC practice in the region; formal programs for physicians and technologists only exist in some countries, with different curricular approaches. Distance training and other educational tools have been successfully used and are expected to expand. The future of NC in Latin America is encouraging, with wide clinical utilization and showing potential for growth as a cost-effective diagnostic method. Education of referring physicians and training in other imaging techniques will become increasingly important for nuclear cardiologists, since a multimodality approach in cardiac imaging would contribute to a better management of patients with CVD. It also seems necessary to increase the number of indexed publications in NC and to improve the quality of regional journals. National, regional, and international collaborative networks are key factors for the development of the specialty in the region.
There are many challenges and opportunities for nuclear cardiology in the assessment and treatment of ischemic heart disease in Asia. A short recitation of the scope of the problem in Asia, the role of nuclear cardiology, and the various impediments to the widespread, appropriate and cost-effective use of nuclear cardiology is given, together with a list of possible solutions to these hindrances applicable to Asian countries.
Nuclear Cardiology in India is underutilized. Contributing factors include high cost of starting Nuclear medicine facility, stringent regulations, small pool of trained nuclear physicians and technologists, high cost of radio pharmaceuticals and supply issues, poor penetrance of nuclear medicine in rural areas, inadequate exposure of cardiologists during training to the advantages of nuclear cardiology. India is poised to see an epidemic of coronary artery disease (CAD) and diabetes by end of few decades and nuclear cardiology would make significant contributions to handle this epidemic. Government and insurance companies advocacy is necessary for nuclear Cardiology to get its important rightful place in the management of CAD in India.
Although ischemia should be evaluated before revascularization, stress myocardial perfusion imaging (MPI) is declining in Japan. On the other hand, computed tomography coronary angiography (CTCA) is increasing. Elective PCI increases in proportion to increase of CTCA. Fractional flow reserve (FFR) can also assess ischemia and identify the lesion for revascularization. FFR-guided revascularization improves prognosis, so FFR is increasingly used before PCI. However, elective PCI hardly decreases. FFR-CT can assess ischemia similar to FFR and correlated well with FFR. Therefore, the role of stress MPI as a gate keeper for CAG/PCI may be partially replaced by FFR-CT in the near future.
The present paper provides an overview of selected articles published by French research teams that are representative of recent advances in the field of nuclear cardiology, particularly in connection with the advent of new dedicated cardiac CZT cameras. The topics discussed here cover the impact of respiratory motion correction in myocardial perfusion imaging, global and regional LV function assessment using CZT cameras, innovative approaches in MIBG imaging, and RV function analysis by means of gated blood pool SPECT.
Radiation Safety and Handling Physicians Should Know About
The most common form of spill of radioactive liquids in Nuclear Cardiology facilities occur in conjunction with exercise tests during rapid injection of a bolus of activity through an indwelling intravenous line and stop-cock mechanism. While minor spills are those involving 3.7 MBq or less of activity, most Nuclear Cardiology stress tests employ considerably larger amounts of radioactivity and produce major spills requiring a methodical response in order to limit radiation dose to patients and occupationally exposed radiation workers. Following a major spill the recommended procedure is to seal off the contaminated area until safe levels of radiation exposure survey meter readings are reached, considered to be less than 1 mR/hr. Diligent adherence to a quality assurance program schedule is necessary in order to guarantee that radiation measuring equipment is operating reliably. By following reasonable precautions and with adequate training of personnel, the majority of major radiation spills encountered in Nuclear Cardiology laboratories are easily avoidable.
Innervation imaging using 123I-meta-iodobenzylguanidine (MIBG) has been applied mainly to imaging heart failure in nuclear cardiology. The most popular quantitation tools comprise the heart-to-mediastinum (H/M) ratio and the washout rate (WR) derived from anterior planar images. Although the method of calculation is simple, some cautions are essential for region-of-interest setting. In addition, camera-collimator differences should be considered for the H/M ratio, and background and time-decay correction is needed to precisely determine the WR. Since the H/M ratio and WR have been applied to most diagnostic and prognostic studies of heart failure, understanding these parameters is important for clinical applications of 123I-MIBG.
Cardiac positron emission tomography (PET) has evolved over the several decades since its introduction. In current clinical practice and research, cardiac PET imaging is accepted as a valuable noninvasive modality for assessing various cardiac diseases such as coronary artery disease (CAD), cardiac tumors, and inflammatory diseases including cardiac sarcoidosis (CS). PET enables the imaging and evaluation of the cardiovascular system by myocardial perfusion with 82Rb, 13N-NH3 and 15O-H2O, and those of metabolism and inflammation using 18F-fluorodeoxyglucose (18F-FDG). PET has demonstrated superior diagnostic accuracy for the detection of CAD and also has well-established prognostic value. The combination of qualitative and absolute quantifications of myocardial blood flow enhances the diagnostic accuracy for multiple-vessel disease and provides incremental functional and prognostic information. In this review, we focus on the current and future roles of cardiac PET imaging, on the basis of our own experience.
The Japanese Society of Nuclear Cardiology (JSNC) annual scientific meeting has a young investigator competition (YIA) session each year. The JSNC scientific committee selects the top 3 qualified abstracts submitted by JSNC members under age 40 who wish to receive the YIA. Given the high quality of presentations and content on the latest research topics, the YIA session is one of the highlights of the JSNC annual scientific meeting. Each of the 3 YIA candidates makes a presentation at the YIA session. At last year’s annual meeting, the scientific committee selected 2 clinical research abstracts and 1 technical research abstract. These 3 abstracts included the latest findings in nuclear cardiology on topics including risk stratification after coronary revascularization, myocardial blood flow quantification, and the performance of a new-generation single-photon emission computed tomography (SPECT) scanner.
The Japanese Society of Nuclear Cardiology (JSNC) has given Technical Award for outstanding technologists since 2012 to promote nuclear cardiology research. Tomohiko Kobota won the 5th JSNC Technical Award. The February issue of “Shinzo Kaku Igaku” (Japanese Journal of Nuclear Cardiology) contains his review article related to his work wining the prize. He and his colleagues developed a method to automatically measure the heart-to-mediastinum ratio in 123I-MIBG scintigraphy, which is expected to reduce the intra- and inter-observer differences of the calculated values. The major feature of this method is the use of chest X-ray data to guarantee the accuracy of the measurement even when myocardial tracer uptake is markedly reduced.