Cardiac Blood Pool Imaging Research Articles

Preclinical PET Imaging and Toxicity Study of a 68Ga-Functionalized Polymeric Cardiac Blood Pool Agent

Cardiac blood pool imaging is currently performed almost exclusively with 99mTc-based compounds and SPECT/CT imaging. Using a generator-based PET radioisotope has a few advantages, including not needing nuclear reactors to produce it, obtaining better resolution in humans, and potentially reducing the radiation dose to the patient. When the shortlived radioisotope 68Ga is used, it can be applied repeatedly on the same day-for example, for the detection of bleeding. Our objective was to prepare and evaluate a long-circulating polymer functionalized with gallium for its biodistribution, toxicity, and dosimetric properties. A 500 kDa hyperbranched polyglycerol was conjugated to the chelator NOTA and radiolabeled rapidly at room temperature with 68Ga. It was then injected intravenously into a rat, and gated imaging allowed us to easily observe wall motion and cardiac contractility, confirming the suitability of this radiopharmaceutical for cardiac blood pool imaging. Internal radiation dose calculations showed that the radiation doses that patients would receive from the PET agent would be 2.5× lower than those from the 99mTc agent. A complete 14-day toxicology study in rats concluded that there were no gross pathology findings, changes in body or organ weights, or histopathological events. This radioactive-metal-functionalized polymer might be a suitable non-toxic agent to advance for clinical application.

Detection of Cardiac Toxicity Due to Cancer Treatment: Role of Cardiac MRI.

Common cancer treatments including anthracycline-based chemotherapy, tyrosine kinase inhibitors, and thoracic radiation therapy can result in short- and long-term cardiovascular complications with a significant impact on morbidity and mortality. Anthracycline-based chemotherapy and tyrosine kinase inhibitors are associated with left ventricular systolic dysfunction and heart failure. Radiation therapy is associated with restrictive cardiomyopathy, coronary artery disease, as well as pericardial and valvular disease. The current standard surveillance of oncology patients for cardiotoxicity involves echocardiography, radionuclide cardiac blood pool imaging, and cardiac magnetic resonance (CMR) imaging. CMR can be used to evaluate ventricular structure and function, which is important for management decisions to prevent further cardiac injury. In patients for whom standard surveillance imaging demonstrates a drop in systolic function with or without symptoms, the use of CMR is an appropriate next step for further evaluation due to the accuracy and reproducibility of measurements of function and volumes combined with the additive information provided by tissue characterization through imaging of myocardial edema and myocardial fibrosis, although the clinical applications of these latter are as yet unclear. Overall, detection of early cardiotoxicity is important since therapeutic response is improved with prompt initiation of medical treatment.

臨床 高血圧性心疾患と肥大型心筋症の鑑別 心プール法を用いて・PFR/TPFR(平均充満加速度)算出の試み

臨床 高血圧性心疾患と肥大型心筋症の鑑別 心プール法を用いて・PFR/TPFR(平均充満加速度)算出の試み

In vivovalidation of quantitative SPECT in the heart

We have previously developed and validated a method to achieve quantitative SPECT data based on CT-derived corrections, for the radionuclide (99m)Tc in phantoms and in man for lung scanning. This clinical study was performed to investigate the accuracy of this method when applied to cardiac blood pool imaging. The study involves tagging the radionuclide (99m)Tc to erythrocytes in a sample of the subject's blood before it is re-injected. After a short time, the radiolabelled cells achieve an equilibrium concentration in the blood pool, such that SPECT imaging allows the radioactivity concentration of blood present in the left ventricle to be measured. Absolute concentration of radioactivity inside the left ventricle of the heart was compared to true concentrations measured directly from a peripheral venous blood sample taken from the subject at the time of scanning. In 12 subjects, the average difference between the measured and true concentrations was found to be within approximately 1% of the true value with a range of (-6 to +5)%. This study demonstrates the accuracy of CT-based quantitative SPECT in clinical cardiac blood pool imaging, and we anticipate that similar accuracy could be achieved in the myocardium.

Development of a new semi‐quantitative non‐invasive method for evaluating ventricular stroke work

Ventricular stroke work (SW) is one of the best indices to evaluate ventricular function, however, the SW monitoring mainly depends on the invasive method with the artery catheter. In this paper, our aim is to develop a new semi-quantitative non-invasive method for evaluating ventricular SW. The multiple gated cardiac blood pool imaging was done in 25 patients with coronary artery disease and 12 normal controls. A new parameter, the relative stroke work (RSW) of left ventricle, was calculated using an equation derived from the principle of hydrodynamics. The left ventricular SW was analyzed by stroke volume (SV) and mean arterial pressure. Ejected fraction (EF), peak ejected rate (PER) and peak filling rate (PFR) were gotten with the routine software in imaging device. The left ventricular RSW was linearly correlated with the SW. The RSW was related to the SV, EF, PER and PFR of the left ventricle. The RSW had regressive relation with SV and PER. The RSW in patients, same as SW, SV, EF, PFR and PER, was noticeably lower than that in normal controls, P<0.01. The RSW is a potential and valuable clinical index for evaluation of the ventricular function.

Tumor Lysis Syndrome Associated With Reduced Immunosuppression in a Lung Transplant Recipient

Tumor lysis syndrome usually occurs after Initiation of chemotherapy or radiation therapy in cancer patients with a moderate to high tumor burden. To our knowledge, the occurrence of this syndrome after discontinuation or reduction of an immunosuppressive regimen has not been reported in the literature. We describe a patient who had undergone lung transplantation and who was receiving immunosuppression and experienced an episode of acute pancreatitis. During the course of the work-up, the patient was found to have a B-cell lymphoma (posttransplantation lymphoproliferative disease). His tacrolimus dosage was decreased, and azathioprine was discontinued. The patient subsequently developed tumor lysis syndrome. Other than the decrease in immunosuppression, we found no other factor that could have accounted for this syndrome.

Bilateral lung transplantation and pulmonary artery reconstruction in a patient with chronic obstructive pulmonary disease and a giant pulmonary artery aneurysm

Aneurysms of the pulmonary artery are a rare entity. In a review in 1947, Deterling and Clagett documented only 8 cases in more than 100,000 autopsies. Similarly, there were only 6 cases of pulmonary artery aneurysms in 4000 patients documented from 1785 to 1946. 1 These aneurysms are most commonly found with congenital heart anomalies, but acquired aneurysms may be associated with atherosclerosis, cystic medial necrosis, trauma, infections such as syphilis and endocarditis, or inflammatory processes such as giant cell arteritis. Although many patients with pulmonary artery aneurysms demonstrate pulmonary hypertension, this has not been proven to be a causative factor. In fact, most patients with pulmonary hypertension never have aneurysms. Symptoms are usually vague and may represent manifestations of the primary disease process or may be related to local compression. The disease process leads to rupture and death in approximately 30% of patients, with other deaths resulting from right-sided heart failure or pulmonary embolus. 2 Clinical Summary A 64-year-old man with a history of chronic obstructive pulmonary disease and pulmonary hypertension with giant pulmonary artery aneurysms came to our lung transplant center for evaluation. The pulmonary history was significant for tuberculosis treated at 8 months of age and an open lung biopsy performed in 1965 that showed pulmonary fibrosis. Preoperative pulmonary function tests revealed a forced expiratory volume in 1 second of 0.650 L (20% of predicted) and a diffusing capacity of lung for carbon monoxide of 28.9 (23% of predicted). Lung volumes were consistent with emphysema with a total lung capacity of 139% of predicted and a residual volume of 338% of predicted. Arterial blood gas analysis demonstrated a PaO2 of 53 mm Hg and a PaCO2 of 46 mm Hg on 21% inspired oxygen. The chest radiograph revealed enlarged bilateral pulmonary hila (Figure 1), and a computed tomographic (CT) scan of the chest performed in August 2000 showed a 6.2-cm main pulmonary artery with eccentric thrombus extending to the aneurysmal right and left pulmonary arteries (Figure 2). The lung parenchyma showed evidence of emphysema but no evidence of pulmonary fibrosis. Pretransplant cardiac blood pool imaging revealed decreased right and left ventricular ejection fractions at 29% and 39%, respectively. Cardiac catheterization showed pulmonary hypertension with a pulmonary artery pressure of 58/26 mm Hg, a cardiac index of 2.9 L/min, and no evidence of an intracardiac shunt. The patient was deemed a suitable candidate and was placed on the waiting list for a bilateral lung transplant. When donor lungs became available, he underwent a bilateral lung transplantation with reconstruction of the recipient pulmonary artery using donor aorta. The donor was an otherwise healthy 40-year-old patient who had died in a motor vehicle crash. However, the heart was not harvested because of poor left ventricular function. We were, therefore, able to harvest the entire thoracic aorta along with the lungs. The entire donor thoracic aorta was received with the specimen and was dissected from the lungs and placed in cold heparinized saline solution. The donor lungs were separated while the donor aorta was prepared. The patient was placed in the supine position, and the right and left sides of the chest were exposed through the fourth intercostal space using bilateral anterior thoracotomies and transverse division of the sternum. The lungs were then mobilized, and the aneurysm was seen extending from the origin of the main pulmonary artery into both pulmonary hila. The pericardium was opened, and the patient was placed on cardiopulmonary bypass with bicaval and ascending aortic cannulation. After this, both lungs were excised. When the pulmonary arteries were opened, a large amount of fibrinous clot was seen. The left lung was implanted first. The bronchial anastomosis

Aneurysm of the iliac artery demonstrated on Tc-99m in vitro labeled red blood cell scintigraphy.

A 76-year-old man was examined for left lower extremity claudication. An angiogram revealed severely atherosclerotic vessels with a 2- to 3-cm aneurysm of the left iliac artery and a critical stenosis in the left femoral artery. After angioplasty and stent placement of the patient stenotic lesion, cardiac blood pool imaging was obtained to evaluate ventricular function. During imaging, the aneurysm of the left iliac artery was visualized on flow, planar, and SPECT images of the abdomen. These images show that medium size aneurysms of the peripheral vessels can be visualized using blood-pool images.

Effect of Astragalus Injection on left ventricular remodeling in aged patients with acute early-stage myocardial infarction

Objective: To observe the effect of Astragalus Injection (AI) on left ventricular remodeling in aged patients with acute myocardial infarction (AMI).Methods: Patients with AMI were randomly divided into the AI group (46 cases) treated with AI and the control group (46 cases) treated conventionally. Left ventricular end-diastolic volume index (LVEDVI), left ventricular end-systolic volume index (LVESVI), anterior endocardial segmental length (ASL) and posterior endocardial segmental length (PSL) were all assessed by echocardiogram after 1 week and 4 weeks treatment. The cardiac systolic and diastolic functions were detected by nuclide gating cardiac blood pool imaging at the 4th week.Results: After four weeks’ treatment, no obvious change of LVEDVI, LVESVI and ASL in the AI group was found, but these indexes increased significantly in the control group, with significant difference shown between the two groups (P<0.05). As compared with the control group, the left ventricular ejection fraction (LVEF), left ventricular peak ejecting rate (LVPER) and left ventricular peak filling rate (LVPFR) were heightened, the time for peak filling rate (LVTPFR) in the left ventricle was shortened in the AI group.Conclusion: AI is one of the effective drugs in reversing left ventricular remodeling in aged patients with AMI.

The preparation and biodistribution of a new potential cardiac blood pool imaging agent 99mTcN‐TMCHI

The preparation and biodistribution of a new potential cardiac blood pool imaging agent ^99mTcN‐TMCHI

Cardiac blood-pool imaging in oncology more than an ejection fraction?

Cardiac function is commonly evaluated in patients with cancer in most nuclear medicine departments. At their dedicated cancer facility, the authors routinely perform a dynamic right anterior oblique first-pass study and a 4-minute left anterior oblique static planar study in addition to the routine equilibrium gated scanning in appropriate projections. Here they show the range of noncardiac disease encountered using this protocol. Useful unexpected information can be obtained from left ventricular ejection studies, and further data may be gained from these simple additions to this common test.

Atrial myxomas: Experiences with 35 patients in Hawaii

Thirty-five patients with an intracardiac myxoma underwent excision of the tumor in Hawaii between 1974 and 1993. There were 28 female and 7 male patients in the group. Their ages ranged from 11 to 79 years (mean 48) with the majority (71%) between 30 and 60 years old. The patients' medical records were reviewed and special attention was paid to clinical presentation, methods of diagnosis, operative findings, and postoperative course. No ethnic predisposition was found. Forty-six percent of the presenting symptoms were cardiac (congestive heart failure 26%, palpitations 14%, and syncope 6%) while arterial embolization accounted for 11%. Diagnosis was made by angiography, echocardiography, or gated cardiac blood pool imaging. All were reliable, but two-dimensional (2-D) echocardiography was used most often, with no false-positive or false-negative results. There were 32 left atrial, 2 right atrial, and 1 biatrial myxomas. Limited septectomy was performed in most cases, but 9 patients (26%) required Dacron patch repair of the atrial septum. There was 1 death from a cerebrovascular accident the day after the removal of a left-sided atrial myxoma. Other patients had few minor postoperative complications. One patient presented with a recurrence 8 years after resection at another institution; no further recurrences were found. We conclude that due to the non-specific presentation of atrial myxoma, a high index of suspicion is needed. The diagnostic method of choice is 2-D echocardiography. Limited septectomy is a safe procedure, but close follow-up for at least 10 years may be needed to rule out recurrence.

Preparation of dextran 70 injection labeled with technetium 99m for use as a cardiac blood-pool imaging agent

A means of compounding dextran 70 injection labeled with technetium Tc 99m by using readily available pharmaceutical components is described, and the compound's biological distribution is evaluated. The radiopharmaceutical was prepared by mixing 10 mg (0.17 mL) of dextran 70 in sodium chloride with 0.33 mL of 0.9% sodium chloride injection in a 1-mL syringe. This solution was added to a sterile, pyrogen-free vial containing stannous chloride, and the steps were repeated until five vials had been prepared. The contents of each vial were mixed by swirling until the solids were dissolved. The mixture was incubated for five minutes at 22 degrees C, then 1.48 gigabecquerels of sodium pertechnetate Tc 99m injection in a volume of 0.5 mL was added to each vial. The final mixture was incubated for 15 minutes at 22 degrees C and then stored at room temperature. Thin-layer chromatography was performed after zero, three, and six hours of storage to assess radiochemical purity. Five more vials were prepared as above, and five male volunteers were given 185 megabecquerels of the radiopharmaceutical by i.v. push, and scintigraphic images of the anterior chest were taken immediately and 1, 2, and 24 hours after injection. Immediately after preparation, a mean +/- S.D. of 99.0 +/- 1.0% of the 99mTc was bound to dextran 70. Mean +/- S.D. binding was 98.1 +/- 3.7% and 95.8 +/- 7.5% at three and six hours, respectively. Scintigraphy in the five volunteers yielded high-contrast images of the cardiac blood pool with little uptake of the radionuclide by the lungs. (ABSTRACT TRUNCATED AT 250 WORDS)

Enhanced left ventricular performance in endurance trained older men.

The age-associated decline in aerobic exercise capacity is partially reversible by endurance exercise training. Moderate-intensity endurance exercise training increases aerobic exercise capacity mediated, in part, by improvement of stroke volume and left ventricular performance in older men. The present study was designed to characterize the nature of cardiovascular adaptations to strenuous endurance exercise of long duration and to delineate the mechanisms underlying increased stroke volume and cardiac output in highly trained older endurance athletes. Nine male master athletes (MA: 64 +/- 2 years old, mean +/- SEM) and 9 older sedentary healthy men (controls: 63 +/- 1 year) were studied. Left ventricular systolic function was evaluated with the use of cardiac blood pool imaging and echocardiography. Maximal O2 uptake (VO2max) was 50.4 +/- 1.7 mL.kg-1 x min-1 in the MA and 29.6 +/- 1.4 mL.kg-1 x min-1 (P = .0001) in controls. Systolic and mean blood pressures at rest and during exercise were not different in the two groups. Left ventricular systolic function at peak exercise was higher in the MA than in sedentary controls as evidenced by (1) a higher left ventricular functional reserve (delta EF: 12.4 +/- 2 versus 5.6 +/- 2.5, P = .05), (2) a large decrease in end-systolic volume during exercise (MA: 56 +/- 4 mL at rest and 42 +/- 5 mL at peak exercise, P = .007; controls: 43 +/- 2 mL at rest and 42 +/- 6 mL at peak exercise, P = .35) with no differences in systolic blood pressure, (3) a higher left ventricular fractional shortening at peak exercise (MA: 52 +/- 2.6%; controls: 45 +/- 1%, P = .046) at comparable values for end-systolic wall stress (MA: 56 +/- 12 g/cm2; controls: 53 +/- 7 g/cm2, P = .50), and (4) a greater decrease in end-systolic diameter at peak exercise in the MA than in controls (MA: -1.2 +/- 0.16 cm versus -0.57 +/- 0.13 cm, P = .014) despite no significant differences between the changes in end-systolic wall stress during exercise (MA: -15.5 +/- 7.5 g/cm2, controls: -11.0 +/- 9.0 g/cm2, P = .6). MA had a larger end-diastolic volume at rest (153 +/- 6 versus 132 +/- 4 mL, P = .009) with a normal wall thickness-to-radius ratio (0.34 +/- 0.02). Peak exercise stroke volume was higher (P = .023) in the MA (132 +/- 6 mL/min) than in the sedentary controls (111 +/- 6 mL/min). Changes in stroke volume correlated strongly with changes in ejection fraction in the MA (r = .80, P = .010) but not in sedentary controls (r = .59, P = .097). Further, changes in stroke volume from rest to exercise correlated strongly with changes in end-diastolic volume in both MA (r = .78, P = .013) and sedentary controls (r = .73, P = .026), suggestive of reliance of stroke volume on end-diastolic volume and preload. However, for a given increase in end-diastolic volume, the rise in stroke volume during exercise was significantly larger in the MA than in controls, which, in the absence of differences in mean blood pressures, indicates that enhanced left ventricular systolic function independent of preload plays an additional role in maintaining a higher stroke volume at peak exercise in the highly trained older men. Cardiac adaptations in older endurance trained men are characterized by volume-overload left ventricular hypertrophy and enhancement of left ventricular systolic performance at peak exercise. These adaptive responses contribute to enhanced stroke volume at peak exercise in older endurance trained men.

RADIONUCLIDE VENTRICULAR FUNCTION ANALYSIS

The information available from ventricular function studies is important in the management of patients with cardiovascular disease. Radionuclide measurements of ventricular function are closely related to the presence and extent of myocardial damage secondary to various etiologies. The two most commonly used techniques to assess ventricular function are the first-pass radionuclide angiocardiogram and the equilibrium radionuclide angiogram. The first-pass radionuclide angiocardiographic technique assesses function at the time of the bolus administration of the radiotracer. The cardiac blood pool imaging technique has the advantage of being able to assess function hours after tracer administration. Both techniques have their own limitations and advantages. Several measurements can be obtained with radionuclide ventricular function analysis. The most important parameters obtained are the right and left ventricular EFs, wall motion analysis, intracardiac shunts, volumes, and diastolic function. Radionuclide ventricular function analysis can provide information beneficial to patient management in a variety of cardiac disorders including ischemic heart disease, valvular heart disease, and congenital heart disease. Radionuclide ventricular function measurements are well established, important determinants in patients with diagnosis and prognosis of cardiovascular disorders. New 99mTc-labeled radiopharmaceuticals are now available and permit the simultaneous measurement of myocardial perfusion and ventricular function. The combined perfusion and function studies obtained during a single tracer administration provide a large amount of information important to the management of patients with cardiovascular disease. The combination of perfusion and functional measurements may improve the prognostic evaluation of patients with cardiovascular disease.

Regional observer performance variation in the evaluation of gated cardiac blood pool studies.

Receiver operating characteristic (ROC) analysis demonstrated that regional variations of sensitivity exist in the detection of wall motion abnormality in cardiac blood pool imaging studies. The observer response is significantly better in the apex than either the septum or posterolateral wall segments. The observer errors tend to be false-negative in the posterolateral wall segment and false-positive in the other two segments. Image presentation can make a significant difference to the overall sensitivity, and the monochrome cine-sequence performed best in this study.

Intraventricular Photon Deficiency in Gated Cardiac Blood Pool Imaging due to Left Ventricular Metastases from Renal Cell Carcinoma

Cardiac metastasis can occur with any widely disseminated malignancy, especially from carcinoma of the kidney, stomach, lung, breast, or from melanocarcinoma. Metastasis to the myocardium can protrude from the endocardium into the intraventricular cavity of the left ventricle. We present a case of renal cell carcinoma and left ventricle cavitary metastases, documented by an echocardiogram demonstrated in a cardiac blood pool study as a photon-deficient area in the left ventricle cavity.

Simultaneous reconstruction, segmentation, and edge enhancement of relatively piecewise continuous images with intensity‐level information

A multinomial image model is proposed which uses intensity-level information for reconstruction of contiguous image regions. The intensity-level information assumes that image intensities are relatively constant within contiguous regions over the image-pixel array and that intensity levels of these regions are determined either empirically or theoretically by information criteria. These conditions may be valid, for example, for cardiac blood-pool imaging, where the intensity levels (or radionuclide activities) of myocardium, blood-pool, and background regions are distinct and the activities within each region of muscle, blood, or background are relatively uniform. To test the model, a mathematical phantom over a 64 x 64 array was constructed. The phantom had three contiguous regions. Each region had a different intensity level. Measurements from the phantom were simulated using an emission-tomography geometry. Fifty projections were generated over 180 degrees, with 64 equally spaced parallel rays per projection. Projection data were randomized to contain Poisson noise. Image reconstructions were performed using an iterative maximum a posteriori probability procedure. The contiguous regions corresponding to the three intensity levels were automatically segmented. Simultaneously, the edges of the regions were sharpened. Noise in the reconstructed images was significantly suppressed. Convergence of the iterative procedure to the phantom was observed. Compared with maximum likelihood and filtered-backprojection approaches, the results obtained using the maximum a posteriori probability with the intensity-level information demonstrated qualitative and quantitative improvement in localizing the regions of varying intensities.

Assessment of Cardiac Function Using Radionuclide Techniques. Theory, Technical Considerations and Clinical Application.

The recent expansion of interventional cardiovascular techniques has stimulated the development of non-invasive cardiac studies, to evaluate the outcome of the interventional therapy. Radionuclide ventriculographic technique provides to quantify global left ventricular systolic/diastolic performance, and evaluate the regional left ventricular wall motion during rest or exercise. This concept was extended from the "bedside" to the ambulatory environment with the description of a battery powered device, the radionuclide ventricular function monitor. To assess the performance of cardiac function using radionuclide ventriculography to that using the ambulatory ventricular function monitor, the systolic and diastolic function were measured at rest in a series of healthy volunteers (n = 10) and in patients with cardiovascular disease (n = 23). Seventeen patients had coronary artery disease (CAD) with prior myocardial infarction, three patients had coronary artery disease, and three patients had dilated cardiomyopathy. The 23 patients manifested a wide variation in LV systolic function. The relationship between the multiple gated acquisition (MUGA)-ejection fraction and the ambulatory ventricular function monitor-ejection fraction correlated well (r = 0.90). As a complement to the radionuclide perfusion studies, cardiac blood pool imaging and radionuclide ventricular function monitoring allow for through non-invasive description of cardiac physiology and function in patients with various cardiac disorders.

Clinical applications of SPECT.

The clinical use of single photon emission computed tomography (SPECT) has grown steadily over the last decade. SPECT is now an essential technique for certain studies such as cerebral blood flow imaging. Many other common nuclear medicine studies give better results when they are performed with SPECT. These include myocardial perfusion imaging with thallium-201 or the new technetium-99m perfusion agents, myocardial infarct imaging with infarct-avid agents, imaging of tumors or infections with agents such as gallium-67 or indium-111 WBC's, and certain cases of bone imaging. Still other studies such as liver/spleen imaging, most brain studies, and perhaps renal imaging may benefit from SPECT even though planar imaging gives satisfactory results. Future developments in 3D display techniques and faster computers may extend the clinical usefulness of SPECT to other areas such as pulmonary perfusion imaging and gated cardiac blood pool imaging.