Cardiovascular Nuclear Medicine Research Articles

Cardiovascular molecular imaging

The recent introduction of novel gene therapies for treatment of cardiac and noncardiac diseases has caused a remarkable need for noninvasive imaging approaches to evaluate and track the progress of these therapies. In the past we have relied on the evaluation of the physiological consequences of therapeutic interventions. With advances in targeted molecular imaging we now have the ability to evaluate early molecular effects of these therapies. The development of dedicated high resolution small animal imaging systems and the establishment of transgenic animal models has enhanced our understanding of cardiovascular disease and has expedited the development of new gene therapies. Noninvasive targeted molecular imaging will allow us to directly track biochemical processes and signaling events that precede the pathophysiological changes. The examples of targeted molecular imaging outlined in this seminar provide some insight into the bright and growing future of cardiovascular molecular imaging. The success of this new field rests on the development of targeted biological markers of molecular and physiological processes, development of new instruments with improved sensitivity and resolution, and the establishment of multidisciplinary teams of experimental and clinical investigators with a wide range of expertise. Molecular imaging already plays a critical role in the experimental laboratory. We expect that, in the near future, targeted molecular imaging will be routinely used in clinical cardiovascular nuclear medicine laboratories in conjunction with existing imaging modalities for both diagnostic and prognostic purposes, as well as for evaluation of new genetic based therapeutic strategies.

“THE UNVEILED HEART” a teaching program in cardiovascular nuclear medicine

The functional investigation of cardiac diseases using nuclear techniques involves several variables, such as myocardial perfusion, cellular viability or mechanical contraction. The combined, topographical and quantitative assessment of these variables can characterize the functional state of the heart in terms of normal myocardium, ischemia, hibernation or necrosis. The teaching program, “The Unveiled Heart”, has been designed in order to help nuclear physicians or cardiologists approaching these concepts and their implications for diagnosis of coronary artery disease, optimization of therapeutic strategies and prognosis evaluation. Anatomical correlations with coronary angiographic results obtained during balloon occlusion at the time of coronary angioplasty demonstrate the complementary role of imaging techniques and highlight the patient to patient variability of risk areas. A sectorial model derived from a polar projection of the myocardium presents for each sector the probability of involvement of a given coronary artery.

Cardiovascular imaging: who does it and how important is it to the practice of radiology?

Our research was conducted to ascertain the importance of noninvasive cardiovascular imaging to the practice of radiology and to determine what percentages of noninvasive cardiovascular imaging are performed by radiologists and by other types of physicians. Using the national 1998 Medicare Part B database, we reviewed all 460 procedure codes pertaining to noninvasive diagnostic imaging and identified 65 that were specifically related to the cardiovascular system. These 65 codes were grouped in five categories: cardiac MR imaging, MR angiography, cardiovascular nuclear medicine, echocardiography, and vascular sonography. For each code and category, we determined the nationwide examination volume, the utilization rate per 1,000 Medicare fee-for-service enrollees, Part B physician reimbursements, and the percentages of examinations performed by radiologists, cardiologists, surgeons, and other physicians. During 1998, 19,244,001 noninvasive cardiovascular imaging studies were performed on Medicare enrollees, which accounted for 17.7% of all Medicare diagnostic imaging studies carried out that year and 33.6% of all Part B imaging-related reimbursements paid. The utilization rate for noninvasive cardiovascular imaging was 603 per 1,000 Medicare enrollees per year. Echocardiography alone accounted for 63.4% of these examinations. Radiologists conducted 16.7% of all noninvasive cardiovascular imaging, whereas cardiologists conducted 61.5%, surgeons 4.8%, and other physicians 16.9% of the examinations. The strong role of cardiologists was largely attributable to their dominance in echocardiography. Radiologists had a substantial role in all categories except echocardiography. Noninvasive cardiovascular imaging represents an important component of the practice of radiology. Radiologists have substantial participation in all aspects of the field with the exception of echocardiography.

Nuclear medicine and cardiology: the position of the Union of European Medical Specialists/Section of Nuclear Medicine.

This paper summarizes a communication presented at the Second International Conference of Nuclear Cardiology, held in Cannes on 23-26 April 1995. The general evolution of nuclear medicine in Europe is examined within the context of European Union Directives, and the role of the Union of European Medical Specialists/Section of Nuclear Medicine is discussed. Thereafter consideration is given to the technical aspects of cardiovascular nuclear medicine procedures, and the situation with respect to such procedures in European countries is examined. In most European countries, nuclear medicine is a recognized specialty, while "nuclear cardiology" does not exist in its own right. In general, only nuclear medicine specialists have the responsibility for radionuclide studies, and most cardiovascular studies are performed under the direct responsibility of a licensed nuclear medicine specialist.

Nuclear Medicine in Clinical Diagnosis and Treatment, vols 1 & 2

This encyclopedic pair of volumes contains 114 chapters by a renowned international mix of contributors, who have discussed in a direct manner the scientific bases of clinical nuclear medicine. Clinical nuclear medicine, of course, has grown exponentially since the early 1970s, when bone scanning, cardiovascular nuclear medicine, and reconstructive tomography allowed it to embark on a prolonged and continuing period of growth. More recently, we have seen major advances in radiopharmaceutical design with wonderful new tracers, novel positron emission tomography (PET) investigations of neuroreceptors, great interest in tumor imaging, and, just now, heightened expectations of a revolution in single photon emission computed tomography (SPECT) instrumentation, such as fan-beam collimation for multidetector systems with capabilities for attenuation and scatter corrections. The textbook edited by Drs Murray and Ell builds upon this incredible development in clinical nuclear medicine during the past 25 years. The first 20 chapters cover the clinical nuclear medicine

Selected Atlases of Cardiovascular Nuclear Medicine

Each volume in the Atlases of Clinical Nuclear Medicine covers one anatomic region or system. Extensively illustrated with superb quality images, each atlas reveals the spectrum of normal scintigraphic findings as well as examples of both common and unusual conditions. Detailed figure legends describe the findings within each image, and most discuss the image's important teaching point. The text, which is descriptive yet concise, covers such topics as procedure technique, dosimetry, physiology, and scan interpretation. The Atlases of Clinical Nuclear Medicine fulfill equally the needs of practicing radiologists, nuclear medicine physicians, and residents seeking to utilize this helpful diagnostic modality more effectively. Selected Atlases of Cardiovascular Nuclear Medicine is comprised of five individual atlases in the areas of Myocardial Perfusion Images, Artifacts in 201 Thallium Spect Cardiac Perfusion Imaging, Artifacts in 99m Technetium Sestamibi SPECT Cardiac Perfusion Imaging, Cardiac Positron Emission Tomography, and Indium-111 Antimyosin Imaging of Myocardial Necrosis.

Current procedural terminology coding of nuclear medicine procedures

The future of nuclear medicine is dependent on payment for new procedures. Today, the basis of payment by the federal government is a relative value unit (RVU) system; the RVUS employed in this system are for medical services and procedures listed and described in Physicians' Current Procedural Terminology, fourth edition. Current procedural terminology (CPT) is maintained by the AMA; annual revisions include adding new codes or revised or deleted old codes. This process involves all national medical specialty societies. Starting in 1992 a new process, the Relative Updating Committee, which was initiated by the AMA, organized medicine to formalize a method for recommending relative values for physician procedures and services. In this rapidly changing scenario, all nuclear medicine procedure codes are under review by the coding and nomenclature committees of the medical societies interested in imaging. Significant CPT changes and additions were made in the cardiovascular nuclear medicine codes in 1992, reflecting the current imaging protocols and pharmacological agents for performing cardiac stress testing and new codes that recognize combinations of ventricular function measurements in patients undergoing myocardial perfusion imaging with technetium-99m agents.

Work force problems in nuclear medicine and possible solutions

Nuclear medicine practice and work force demographics reflect the historically diverse evolution of this specialty. The most pressing problem for nuclear medicine is a projected shortage of fully trained physicians due to practitioner retirement that is unmatched by residency program output. During the past decade the number of 2-year nuclear medicine residency programs (average of 90) and the total number of residents (average of 191 in both years) have remained remarkably stable. In contrast, the number of 1-year nuclear radiology residency programs, available positions, and residents have declined significantly. A similar decline is seen in radiologists obtaining full nuclear medicine training and American Board of Nuclear Medicine (ABNM) board certification. This void has been filled by nonradiologist trainees who only seek certification by ABNM. Perhaps such shifts in resident profile are an early indicator that the United States is evolving toward practice models in which nuclear medicine is provided by fully trained, full-time physicians, similar to the European work force model. The recent Society of Nuclear Medicine survey of 10,446 physicians who practice nuclear medicine shows a current practice pattern in the United States that is distinctly different from that in Europe. The vast majority of those surveyed practice part time. Only 7% of all physicians who practice nuclear medicine do so full time, (ie more than 90% of the time), but they account for as much full-time employee (FTE) work load as 70% of all part-time physicians. Although the number of radiologists entering nuclear medicine is declining, 51% of total FTE work load is still done by radiologists with only American Board of Radiology certification. Physicians certified by ABNM represent 42% of all FTE work load. Cardiologists certified by American Board of Internal Medicine-Cardiovascular Specialization account for approximately 4% of nuclear medicine (15% of total cardiovascular nuclear medicine) FTE work load. Work force shortage of nuclear medicine technologists remains a chronic problem in spite of extensive study: however, recent predictions suggest some improvement in the future. Solutions to work force problems facing nuclear medicine will require ongoing data surveys, aggressive recruitment of trainees, expansion of training positions, and socioeconomic initiatives that promote desirable future practice models.

Role of single photon wall motion and perfusion studies in the evaluation of patients with suspected coronary artery disease

Cardiovascular nuclear medicine procedures are useful to characterize coronary artery disease by measuring changes in perfusion, myocardial metabolism, cellular integrity, and regional or global function. Coronary angiography, while an excellent indicator of anatomic changes in arterial lumenal diameter, is a poor predictor of downstream perfusion, since neither the length of the stenosis nor absolute lumenal diameter is considered. Even if the anatomy is known, perfusion measurements provide information about ischaemia and ventricular dysfunction that is helpful for planning therapy. New technetium 99m-labelled perfusion agents are likely to improve the certainty of diagnosis due to their higher photon flux. The development of techniques for continuous ventricular function monitoring during daily activities provides an opportunity for detecting the impact of silent ischaemia on cardiac function. The role of the radionuclide imaging procedures in classifying patients with coronary disease is discussed in light of the pathophysiology of ischaemia and necrosis.

Normwerte der Äquilibrium- Radionuklidventrikulographie

The Working Group on Cardiovascular Nuclear Medicine of the German Society of Nuclear Medicine has organised a multi-center study in which 13 institutes in the FRG participated. Data on equipment and methods employed in equilibrium radionuclide ventriculography and on results in 585 non-cardiac patients were obtained by means of a questionnaire. The global left-ventricular ejection fraction amounted, on average, to 64% but there were significant differences between participating institutes, probably due to differences in the selection of subjects and in the methods used. The majority of institutes reported an increase in EF by more than 10% after an ergometric workload of more than 100 W. Enddiastolic, endsystolic and stroke volumina agreed well throughout. However, whereas peak ejection and peak filling rates at rest showed good agreement between institutes, those after exercise differed widely, probably also because of differences in methods.

The clinical use of nuclear exercise tests.

In the mid-1970s, after decades of clinical use, the utility of electrocardiographic exercise testing for the evaluation of patients with suspected ischemic heart disease was critically examined and questioned. Concurrent with this critique, two sophisticated, more expensive and powerful "nuclear" exercise tests were introduced sequentially for clinical use: myocardial perfusion imaging with thallium-201 and radionuclide ventriculography with technetium 99m. The published indications for the two tests are similar, and both have been shown to offer advantages over ECG stress testing in selected populations. However, few data are available regarding the comparative utility of thallium versus ventriculographic imaging. As part of a prospective study to assess the efficacy of cardiovascular nuclear medicine studies, we undertook the present analysis to assess the clinical evolution of these tests and to elucidate factors responsible for clinicians' choice for the often competing examinations. The study examined 213 consecutive patient referrals for thallium scintigraphy and 183 referrals for ventriculography, ranging from patients with no symptoms or highly non-specific chest pain syndromes (21% of referrals) to patients with proven coronary disease (28% of the referrals). Twenty-one percent of patients were referred to confirm the clinical impression that the patient did not have coronary disease, 40% to confirm its presence, and 37% to determine its severity. Analyses were undertaken to determine the factors that dictated a preference for thallium scintigraphy rather than ventriculography; only the physician's intent in testing and level of training were significant predictors for a particular nuclear test.

The efficacy of cardiovascular nuclear medicine exercise studies

Radionuclide stress tests were initially introduced into medicine as new diagnostic tests for coronary artery disease (CAD). These tests are very effective for this purpose when applied to populations with an intermediate pre-test probability of coronary artery disease. Radionuclide stress tests, however, also are used now in guiding many management decisions in patients with established CAD, based on the ability of these tests to assess the extent and severity of myocardial ischemia, the functional significance of coronary stenoses, and myocardial viability. Specific uses beyond diagnosis include decisions regarding whom to catheterize, send to coronary bypass surgery, or angioplasty; risk stratification following myocardial infarction or before noncardiac surgery; and evaluation of the results of therapy. This article reviews both the diagnostic efficacy of radionuclide stress tests and their efficacy in guiding management decisions in patients with known coronary artery disease.

Recent developments of cyclotron produced radionuclides for nuclear cardiology

For over a decade myocardial perfusion imaging with thallium-201, a cyclotron product, has been routinely used in clinical medicine. Recent advances have allowed the efficient production of very high purity (> 99.8%) iodine-123. New metabolically active 123I labeled radiopharmaceuticals, including alkyl and phenyl fatty acids, and norepinephrine analogs, have been developed and are undergoing clinical trials. Fab' fragments of monoclonal antibodies to cardiac myosin have been labeled with indium-111 (111In) and are undergoing clinical evaluation for imaging myocardial infarcts. Monoclonal antibodies to platelets, fibrin, and the thrombolytic agent, tissue plasminogen activator (TPA), have recently been labeled with 111In. Together these developments in radiotracers and instrumentation should have a significant impact on the future of cardiovascular nuclear medicine. This manuscript will discuss developments in single photon emitting radiotracers for myocardial imaging.

Current status and prospects of new radionuclides and radiopharmaceuticals for cardiovascular nuclear medicine

The rapid emergence of new imaging modalities like positron emission tomography (PET) and single photon emission computerized tomography (SPECT) and their advance into the clinical arena offered new opportunities for, but also stimulated research and development of new radiopharmaceuticals suitable for cardiac imaging. While tracers of myocardial blood flow remained in the center of interest, other trends heralded possibilities of studying more comprehensively cardiac physiology and pathophysiology as, for example, metabolism, the severity of tissue injury, neural activity and membrane function. N-13 ammonia and rubidium-82 became the primary tracers for evaluating and possibly quantifying regional myocardial blood flow with PET, while cationic Tc-99m isonitrile complexes have now reached a stage where high contrast images of the human heart are obtained on planar scintigraphy and SPECT. These radiopharmaceuticals hold considerable promise for routine clinical use. Tracers of metabolism, especially those labeled with positron emitting isotopes as for example, C-11 palmitate, F-18 2-deoxyglucose, are approaching the phase of clinical use and provide information on regional myocardial substrate metabolism and oxidative processes. Less successful and more limited were developments of single photon emitting tracers of metabolism which remained largely confined to radioiodinated fatty acid analogs. Exploration and characterization of the metabolic fate of the radiolabel in tissue and its relation to the externally observed signal have been truly impressive. Tested in humans primarily in western European countries, these tracers promise to yield metabolic information on a more limited scope. Most widely applied are iodohepta- and hexadecanoic acid and, more recently, the aromatic fatty acid analog, paraiodophenylpentadecanoic acid. Labeled monoclonal antibodies rapidly advanced to the point of clinical use. Accurate identification and sizing of acute myocardial infarction is now possible with Tc-99m or indium-111 labeled specific antimyosin antibody fragments. This success stimulated new research activities for use of labeled antibody techniques in other areas as for example, scintigraphic evaluation of formation and presence of vascular thrombi. While promising, these efforts have however remained in an early stage of development. The same holds true for single photon and positron emitting tracers that are suitable for assessing sympathetic neuron densities in myocardium as well as imaging of both cholinergic and adrenergic receptors.(ABSTRACT TRUNCATED AT 400 WORDS)

Nuclear scans: A clinical decision making tool that reduces the need for cardiac catheterization

We have assessed the impact of cardiovascular nuclear medicine studies (CVNMS) on physicians' decisions to send patients with suspected ischemic heart disease ( N = 439) on to cardiac catheterization at three Bronx hospitals. A change in management plans with respect to catheterization was observed in 31% of cases. Catheterization rates were reduced by 25% among patients referred for resting studies and by 49% for exercise studies (thallium perfusion or exercise wall motion studies). Results of CVNMS had little impact on catheterization decisions for resting study patients ( N = 192). Among exercise study patients ( N = 247), those with normal results had a relative reduction in catheterization post-CVNMS of 82% vs 27% for patients with abnormal results ( p < 0.001). However, impact of exercise CVNMS test results on post-CVNMS catheterization rates obtained for men only; women with abnormal exercise study results were much less likely to undergo subsequent catheterization (7.7%) than men with abnormal results (41.9%), p < 0.005, independent of age. The apparent discrepancy in referral for catheterization based on sex needs to be investigated further.

Current Status and Prospects of Cardiovascular Nuclear Medicine in the Diagnosis of Ischemic Heart Disease

虚血性心疾患の診療において, PTCAやACバイパス術などの積極的治療がさかんに行われるようになり, 虚血部位の判定や心筋のviabilityの評価をする上で, 心筋血流画像法の果たす役割はますます重要になってきている. 現在, 日常臨床の場で, 広く普及しているのがタリウムを用いる方法であるが, その需要はさらに増えつつある. タリウム法の原理・断層画像の判定法・定量解析, およびその表示法・検査の適応・診断率などについて述べ, その意義を強調した. さらに, これからの新しい核医学検査法として, 注目されているテクネチウム標識の心筋血流トレーサーと, ポジトロン標識のN-13アンモニアおよびO-15水による心筋血流の検査法にふれ, その将来を展望した.

Recent trend and future of the cardiovascular nuclear medicine

Recent trend and future of the cardiovascular nuclear medicine

Successful tricuspid valvulectomy without replacement for endocarditis during pregnancy

5 t Gordon DG, Ashburn WL, Slutsky RL: Assessment of ventricular function by first-pass radionuclide angiography. In Berman DS, Mason DT, editors: Clinical nuclear cardiology. New York, 1981, Grune & Stratton, Inc, pp 204-223. Parker .J, Treves S: Radionuclide detection, localization and quantitation of intracardiac shunts and shunts between the great arteries. In Holman BL, editor: Principles of cardiovascular nuclear medicine. New York, 1978, Grune & Stratton Inc. pp 189-218. Howman-Giles RB, Gilday DL, Mason DT, Berman DS: Nuclear cardiology in pediatrics: Evaluation of intracardiac shunts and additional congenital diseases. In Berman DS, Mason DT, editors: Clinical nuclear cardiology. New York, 1981, Grune & Stratton, Inc, pp 285-317. Saalouke MG, Shapiro SR, Perry LW, Scott LP III: Incomplete anomalous pulmonary venous drainage associated with pulmonary vascular obstructive disease. Am J Cardiol 1977; 39:439-444. Perloff J: The clinical recognition of congenital heart disease. Philadelphia, 1978, W. B. Saunders Co, pp 281.284.

New radionuclides for cardiac imaging

T WO RADIONUCLIDES, thallium-201 and technetium-99m, have assumed preeminence in cardiovascular nuclear medicine because their photon energies, kinetics, and dosimetry are well-suited to make three major physiologic measurements: perfusion, function, and viability. The photon energies of these nuclides are well matched to the characteristics of the Anger camera, which has optimum efficiency and resolution for energies between 100 and 200 keV. The spatial resolution of the “system” for the average cardiovascular nuclear medicine study (radiopharmaceutical, collimator, camera, and computer) at the depth of the heart is approximately 1 cm full width half maximum (FWHM). Against this background, new radiopharmaceuticals suggested for the evaluation of the heart (Table 1) must offer an improvement in dosimetry and resolution, or provide data on a previously unmeasurable parameter. This review will concentrate on the new radiopharmaceuticals that have met two criteria: (1) experience with the radiopharmaceutical in human subjects, and (2) some likelihood of commercial production of the agent for widespread clinical use. Although equilibrium studies provide high quality data for evaluation of regional and global cardiac function, a high photon flux first pass approach, which could evaluate ventricular function during breathholding (to eliminate respiratory motion), would improve resolution. The ideal first pass radionuclide should have a short physical halflife, have no particulate emissions, produce photons of 100 to 200 keV, and decay to a stable daughter. Such an agent would permit multiple measurements to be performed in each view and would allow repetitive determinations of ventricular function during the action of drugs, exercise, or physiologic maneuvers (Valsalva, etc). The following agents have some of these properties and may supplant Tc-99m as the radionuclide for first pass studies.

Radiology of the Heart: Cardiac Imaging in Infants, Children, and Adults

This textbook is written from the radiologist's point of view, relating chest roentgenogram findings to angiograms and echocardiograms (M mode and two dimensional). It is closer to an atlas than a textbook: its main thrust is the large number of superb reproductions, many of which are a full or half page in size. Whenever needed, schematic drawings are used to further understanding. Cardiovascular nuclear medicine and magnetic resonance imaging are discussed in single chapters but are not interwoven with the rest of the text. Digital subtraction angiography is excluded. The chapters on specific methodologies such as echocardiography, nuclear medicine, or angulated views for coronary arteriography, are short; they serve as general introductions and are not intended for the serious student of the field. The extensive clinical material represents the personal experience of the authors and their colleagues. The representation of less common lesions is uneven: some are covered in detail,