Effects of carvedilol on right ventricular function in chronic heart failure.

This study investigated the effects of carvedilol on right ventricular (RV) volume and systolic function in chronic heart failure patients. Carvedilol treatment resulted in a significant improvement of RV ejection fraction and systolic performance, which paralleled the improvement of systolic function demonstrated in the left ventricle.

Effects of carvedilol on systolic and diastolic left ventricular performance in idiopathic dilated cardiomyopathy or ischemic cardiomyopathy.

Recent evidence has shown that improvement in left ventricular (LV) systolic function in patients with New York Heart Association class II to III heart failure occurs with beta-adrenergic blocking agents. However the specific effects on LV diastolic function have been subjected to only limited examination. This study investigated the effects of the combined beta blocker/vasodilator, carvedilol, on systolic and diastolic LV performance in dilated cardiomyopathy. Thirty-six patients with New York Heart Association II to III heart failure and LV ejection fraction < or = 0.35 were entered into either arm of this placebo-controlled, double-blind 4-month trial. Twenty-one subjects were entered into the carvedilol treatment arm and 15 patients were entered into the placebo arm in a 3:2 ratio. Carvedilol therapy resulted in a significant improvement in LV ejection fraction, from 0.22 +/- 0.02 to 0.30 +/- 0.02 when compared with the placebo group (0.19 +/- 0.02 to 0.21 +/- 0.02 at baseline and after 4 months of therapy, respectively; p = 0.0001). However, no significant change in radionuclide parameters of LV diastolic function, including peak filling rate or time to peak filling rate, was observed. LV end-diastolic volume index did not change with carvedilol therapy, whereas end-diastolic volume index increased in the placebo group, although the difference between groups at 4 months was significant (p = 0.02). In conjunction with these changes, end-systolic volume index was smaller at 4 months after carvedilol treatment compared with that of the placebo group (p = 0.04). Thus, these results demonstrate that in moderate chronic heart failure, systolic LV performance improves but diastolic LV function does not improve when compared with placebo after treatment with carvedilol.

Use of computer conferencing to allow view box-style teaching sessions with residents at outlying hospitals.

RATIONALE AND OBJECTIVES: Health care reform is placing new pressures on radiology faculty members to use their time more efficiently. We implemented a computer conferencing technique that allows one faculty member to perform a simultaneous view box-style teaching session with residents at local and outlying hospitals. METHODS: The system simultaneously displays digital images on computer screens at the local and outlying hospitals; an on-screen pen allows the instructor or the participants to point to findings on the images. Audio is provided either by a telephone conference call using speakerphones or over the wide-area network using microphones and speakers built into the computers. RESULTS: The technique has been in use for 1 year. A survey of the faculty and residents indicate that computer conferencing is equivalent to traditional face-to-face teaching sessions at the view box. CONCLUSION: Computer conferencing is possible and accepted. The technique is low-cost, using generic computers that are part of the picture archiving and communication system at both hospitals, and relatively inexpensive conferencing software.

Abdominal abscess detection: gallium, 111In-, and 99mTc-labeled leukocytes, and polyclonal and monoclonal antibodies.

Computed tomography (CT) and magnetic resonance imaging (MRI) are excellent modalities for imaging patients with localizing signs of an intra-abdominal abscess. However, radionuclide techniques have an advantage over CT and MRI because they can evaluate the entire body for infection. In addition, radionuclides can noninvasively differentiate infection and inflammation from benign fluid collections. Radiopharmaceuticals available for imaging abdominal infection include gallium-67 citrate, indium-111, and technetium-99m-labeled leukocytes, and radiolabeled whole antibodies. The use of these radiopharmaceuticals for abdominal imaging is dependent on their biodistribution and mechanism of abscess localization.

Biodistribution and dosimetry of indium-111-polyclonal IgG in normal subjects.

UNLABELLED: Indium-111-polyclonal IgG is a new imaging agent of infection and inflammation that has been developed as a possible replacement for radiolabeled leukocytes. We undertook a study to determine the safety, biodistribution and dosimetry of the agent in normal subjects. METHODS: Twelve normal male volunteers with an average age of 34 yr (range 21-55 yr) were studied. Each was injected with 1.22-1.47 mCi 111In-labeled polyclonal IgG; digital whole-body images, in addition to blood, urine and fecal samples, were obtained immediately after injection and at 6, 24, 48, 72, 96 and 120 hr. Whole-body counts, as well as individual organ data obtained by outlining regions of interest, were measured. Blood, urine and fecal counting were done in a well counter and compared to known standards; dosimetry calculations were performed with the MIRD technique. RESULTS: The mean whole-blood activity had a two-phase disappearance curve: the T1/2I was 11.4 hr (61.1%) and the T1/2II was 112.5 hr (38%). Twelve percent of the dose was excreted in the urine and 1.14% in the feces. Skeletal muscle had the highest percentage of uptake, followed by the bone marrow, liver and lungs; the spleen showed less than 1% uptake. Activity in the lungs varied with time, falling by 37% after 18 hr and by 68% after 72 hr. Dosimetry calculations indicated that the highest absorbed dose was to the liver (1.42 rad/mCi) followed by the testes (1.23 rad/mCi) and red marrow (0.976 rad/mCi). The total-body dose was 0.467 rad/mCi, with an effective dose equivalent of 790.84 mrem. CONCLUSION: The biodistribution of 111In IgG is similar to that of 99mTc-HMPAO-labeled leukocytes. Activity in the liver, kidneys and GI tract may make evaluation of infection in these regions difficult. The dosimetry data indicate that adequate doses can be administered for clinical imaging without exposing the patient to excessive radiation.

A transmission-map-based scatter correction technique for SPECT in inhomogeneous media.

In this paper a method of modeling the distribution of scattered events in emission projection data is developed and applied. This method is based on the use of a transmission map to define the inhomogeneous scattering object. The key point is the use of the set of line integrals calculated as part of the attenuation correction technique, as the basis of a model of the distribution of scattered events. The probability of a photon being scattered through a given angle and being detected in the emission energy window is approximated using a Gaussian function. The parameters of this Gaussian are determined using Monte Carlo generated parallel-beam scatter line spread functions from a nonuniformly attenuating phantom. The model is incorporated into a two-dimensional projector-backprojector and used with the Expectation-Maximization-Maximum-Likelihood algorithm for the reconstruction of fan-beam phantom data. The correction is shown to perform well for a phantom that varies slowly in the axial direction. For the more clinically realistic situation of a torso phantom, the method produces improvements in terms of blood pool to myocardium contrast, but does not restore the contrast to the level exhibited in a reconstruction from "scatter free" data.

Gastric emptying response to variable oral erythromycin dosing in diabetic gastroparesis.

Intravenous erythromycin has been shown to improve gastric emptying in diabetic gastroparesis. Oral erythromycin also accelerates gastric emptying, but to a lesser degree. To determine if this is a dose-dependent phenomenon, gastric emptying was measured in 10 insulin-requiring diabetic patients with gastroparesis after administration of either 250 mg or 1000 mg of erythromycin or placebo. The drugs were orally administered in a randomized, double-blind fashion 30 min prior to ingestion of a meal containing [99mTc]-sulfur colloid-labeled beef stew and [111In]DTPA-labeled orange juice. Anterior and posterior gastric images were recorded for 3 hr at 15-min intervals using an externally positioned gamma camera. The results demonstrated that both doses of oral erythromycin significantly improved solid-phase gastric emptying. The mean half-emptying time of solids was decreased from 151 +/- 40 min with placebo to 58 +/- 10 min and 40 +/- 9 min with 250 mg and 1000 mg of erythromycin, respectively. However, a dose-dependent relationship was not demonstrated with the two doses of erythromycin employed. These results suggest that for most patients with diabetic gastroparesis, a single 250-mg dose of erythromycin will significantly improve gastric emptying. It is possible that a dose-dependent relationship will be demonstrated with doses of erythromycin less than 250 mg.

Bilateral fatigue fractures of the radial shaft in a gymnast.

A 24-year-old female gymnast had a 3-month history of bilateral forearm pain. A Tc-99m MDP bone scan demonstrated focally increased activity in the radial shafts on blood pool and delayed images, characteristic of fatigue fractures. Fatigue fractures commonly occur in the lower extremities. Upper extremity fatigue fractures, in contrast, are uncommon and usually involve the humerus or ulna. Fatigue fracture of the radial shaft from gymnastic exercise has not been previously reported.

Redirection of client/server relationship of X Window system as a simple, low-cost, departmental picture archiving and communication system solution for nuclear medicine.

Picture archiving and communication systems (PACS) offer significant advantages over current film-management techniques. However, PACS are complex and expensive, factors that have limited their entry into the radiology and nuclear medicine communities. We present a simple, low-cost PACS solution that allows viewing of images from different computer systems by redirection of the X Window system. In this technique, multiple copies of the imaging software are remotely opened from generic UNIX workstations interfaced to the main computer system via Transmission Control Protocol/Internet Protocol over Ethernet. The X Window system that provides the windowing system for the main computer is redirected to the workstations' displays. With this technique, viewing and processing of images on a remote station is virtually identical to working at the main computer's console. The technique requires that the commercial imaging system's hardware, operating system, and imaging software support multiuser multitasking and the execution of multiple copies of its imaging software, and that they use X Windows as the graphical system. Advantages of the technique include low cost, ease of maintenance, ease of interconnecting different types of computers, the capacity to view images regardless of file format, and the capacity to both view and process images. The latter is a necessity for modalities such as nuclear medicine. A disadvantage of the technique is that the number of nodes that can be supported is limited.

Scintigraphic appearance of bone during external beam irradiation.

Separate imaging studies employing Tc-99m MDP, In-111 labeled leukocytes, and Tc-99m SC were performed in a patient receiving external beam radiation therapy to the mediastinum and left hemithorax. The leukocyte scan demonstrated greatly increased activity at the site of the radiation port. The bone marrow (sulfur colloid) scan was normal and the bone scan demonstrated only minimally increased activity in the irradiated region. The varying appearance of these scans may represent the difference in the early effect of radiation on bone and bone marrow elements.

Image analysis and categorization of ventilation-perfusion scans for the diagnosis of pulmonary embolism using an expert system.

UNLABELLED: An expert system was developed that interprets ventilation-perfusion lung scans. The use of such scans for suspected pulmonary embolism is ideal for computer-assisted diagnosis by expert systems. The data are digital, only a single disease entity is diagnosed or excluded, and well-established diagnostic criteria already exist for visual interpretation that can be easily integrated into an expert system. METHODS: This expert system is divided into two modules. The first module is responsible for image analysis. Analysis was performed on the eight standard perfusion images and on single-breath, equilibrium and 3-min washout ventilation images. Each image was analyzed for the presence of regional perfusion or ventilation defects, as determined by pixel values that fell 2.2 s.d. below the mean (or above the mean in the case of washout images) compared with a database of normal studies. The defect size, segment involved and number of defects were determined. Ventilation and perfusion images were then compared to determine whether defects were matched or mismatched. The second program module applied the modified Biello's criteria to the data and categorized the scan as normal to low, intermediate or high probability. RESULTS: A total of 80 patients were prospectively studied. An 81% (65 of 80) correlation was obtained when the results of the expert system were compared with visual interpretations made by three experienced nuclear medicine physicians. CONCLUSION: This study shows that the interpretation of ventilation-perfusion lung scans by an expert system is possible. The technique holds the promise of reducing interobserver variability and assisting less experienced observers in the interpretation of such scans.

Indium-111-labeled leukocytes for the detection of infection: current status.

Several chelates are available for leukocyte labeling. Studies indicate that cells labeled with any of the chelates have a sensitivity for infection of 90% to 95% when imaged at 24 hours postinjection. The sensitivity of 111In-labeled leukocytes at earlier imaging times is more controversial. There has been concern about the utility of labeled leukocytes in musculoskeletal infection. Recent leukocyte studies show a high sensitivity for infected prostheses, even though these infections are often walled off and do not cause systemic symptoms. However, leukocytes frequently miss osteomyelitis of the spine for reasons that are not known. Although some investigators do not recommend the use of 111In-labeled leukocytes in chronic infections, we have found a high sensitivity for infections that are 2 or more weeks old. Autopsy studies from the preantibiotic era indicate that bacterial infections with common organisms have high levels of neutrophil infiltration for months. Labeled lymphocytes from mixed-cell preparations also may play a role in detecting these inflammatory sites. Questions have been raised about the effect of antibiotic therapy on leukocyte sensitivity. Antibiotics do not appear to have a significant effect on scan sensitivity. By reducing the number of bacteria at an inflammatory site, antibiotics reduce the amount of chemotactic inhibitors. In addition, some antibiotics have been shown to directly stimulate leukocyte chemotaxis. Other factors that can theoretically reduce leukocyte function, including hemodialysis, hyperalimentation, hyperglycemia, and steroids, do not appear to reduce labeled leukocyte sensitivity for infection. The specificity of leukocyte uptake is reduced in the gastrointestinal tract and lungs. In these sites, uptake correlates with infection or the true cause of the patients' fever in only 10% to 50% of cases.

Kinetic modeling of teboroxime using dynamic SPECT imaging of a canine model.

UNLABELLED: The tomographic utility of 99mTc-labeled teboroxime has been limited because of its fast washout from the heart, which requires rapid data acquisitions that have not been feasible until the recent development of multidetector SPECT systems. METHODS: Using a three-detector SPECT system to acquire dynamic tomographic data every 10.2 sec, we investigated the potential of modeling the kinetics of teboroxime to develop a sensitive and quantitative measure of cardiac perfusion. Seven studies were performed on four dogs; in three of the studies the LAD artery was occluded. The three-dimensional activity distributions were reconstructed and were corrected for attenuation using a transmission scan. Time-activity curves from the blood and tissue were fit to a two-compartment model with two-way exchange. RESULTS: Performing attenuation correction during the reconstruction process affected the washin parameter k21 significantly (p < 0.0001). The washin parameter k21 also decreased significantly (p < 0.002) when the LAD was occluded. CONCLUSIONS: The results indicate that the washin of teboroxime in myocardial tissue (k21) measured using dynamic SPECT imaging and kinetic modeling is an indicator of myocardial blood flow.

Application of convergent-beam collimation and simultaneous transmission emission tomography to cardiac single-photon emission computed tomography.

Single-photon emission computed tomography (SPECT) is the most commonly performed imaging technique for perfusion studies of the heart and brain. However, these organs are much smaller than the crystal surface of gamma cameras. SPECT sensitivity and resolution can be improved by using fan- and cone-beam collimators to magnify the image of these organs over a larger portion of the crystal face. Special orbits and reconstruction algorithms must be used with convergent-beam acquisitions to prevent image distortion. Differential attenuation of source activity in the chest is one of the most vexing problems in cardiac SPECT, especially with Thallium-201. Multi-headed cameras equipped with convergent-beam collimators allow a transmission image to be obtained at the same time as emission images. Applying a transmission map of the chest attenuation values to the emission images produces a truer picture of source distribution in the heart. This article reviews the technical problems associated with convergent-beam geometry and simultaneous transmission emission tomography SPECT imaging of the heart.

The efficacy of indium-111-polyclonal IgG for the detection of infection and inflammation.

UNLABELLED: The purpose of this study was to determine the efficacy of 111In-polyclonal immunoglobulin (IgG) for the diagnosis of infection or inflammation. METHODS: Fifty-three patients with suspected infection were prospectively studied. Each underwent an 111In-polyclonal IgG study; biopsy, surgery, additional nuclear medicine scans and radiographic studies were used to confirm the IgG scan results. RESULTS: The polyclonal IgG scan had a sensitivity of 97.9% and a specificity of 94% for infection or inflammation. When only infection or severe inflammation such as bowel infarction was considered, the sensitivity remained the same but the specificity fell to 83%. Chronic infections were detected equally as well as acute infections. Antibiotics, steroids, anti-inflammatory agents, diabetes and diminished renal function did not affect scan sensitivity. There were no adverse reactions to the radiopharmaceutical. Three patients underwent extended imaging. Their scans stayed positive for an average of 8 days. Three patients treated for infection had their scans turn negative on repeat study, confirming the efficacy of their antibiotic therapy. CONCLUSION: Indium-111-polyclonal IgG is an effective imaging agent of infection and/or inflammation that is useful in a variety of infections and in severe inflammatory diseases. The ease of preparation and safety make it an attractive alternative to labeled leukocytes.

Distribution of gallium-67 in normal and hypotransferrinemic tumor-bearing mice.

The mechanism by which 67Ga accumulates in tumors is controversial. The most popular theory is that 67Ga binds to transferrin and gains access to cells by the transferrin receptor. However, substantial evidence suggests that uptake of 67Ga may not be universally mediated by transferrin in tumors. To determine whether transferrin is required for uptake of 67Ga in vivo, we compared the uptake of 67Ga by two types of implanted tumors and by normal tissues in normal and severely hypotransferrinemic strains of Balb/C mice. One type of tumor was strongly gallium-avid in normal mice; the other was not. Uptake of 67Ga by normal soft tissues was markedly less in hypotransferrinemic than in normal mice. Uptake of 67Ga by bone was equivalent in the two types of mice. For the more gallium-avid tumor, uptake of 67Ga was similar and the ratio of tumor-to-background activity was substantially higher in the hypotransferrinemic than in the normal mice. For the less gallium-avid tumor, uptake was significantly less in hypotransferrinemic than in normal mice. These data suggest that uptake of 67Ga by bone and by some tumors may be a transferrin-independent process.