Frederick L. Datz

A Randomized Trial of Intracoronary Streptokinase in the Treatment of Acute Myocardial Infarction

Fifty patients with acute myocardial infarction were randomly assigned to receive either intracoronary streptokinase or standard (control) therapy within about three hours after the onset of pain. Coronary perfusion was reestablished in 19 of 24 patients receiving streptokinase. Streptokinase alleviated pain (as indicated by differences in subsequent morphine use). The Killip class was significantly improved after therapy with streptokinase, as were changes in radionuclide ejection fraction between Days 1 and 10 in surviving patients (+3.9 vs. -3.0 per cent, P less than 0.01). The echocardiographic wall-motion index also showed greater improvement after streptokinase treatment (P less than 0.01). Streptokinase therapy was associated with rapid evolution of electrocardiographic changes, which were essentially complete within three hours after therapy, but loss of R waves, ST elevation, and development of Q waves in the convalescent period were greater in the control group (P less than 0.01). The time required to reach peak plasma enzyme concentrations was significantly shorter after streptokinase. The incidence of early and late ventricular arrhythmias was not affected by treatment. We conclude that intracoronary streptokinase appears to have a beneficial effect on the early course of acute myocardial infarction.

Non-uniform attenuation correction using simultaneous transmission and emission converging tomography

Photon attenuation in cardiac single photon emission computed tomography (SPECT) is a major factor contributing to the quantitative inaccuracy and the decrease in sensitivity of lesion detection. A measured map of the attenuation distribution is used in combination with iterative reconstruction algorithms to accurately compensate for the variable attenuation in the chest. The transmission and emission data are acquired simultaneously using a multidetector, fan beam collimated SPECT system with a precisely aligned transmission line source (Tc-99m) at a different energy than the emission source (Tl-201). The contamination of transmission and emission data due to scatter and multiple photopeaks is removed based on measurements from the detectors acquiring only the emission data. The quantitative accuracy of cardiac SPECT is significantly improved using simultaneously acquired transmission and emission data which are obtained in clinically acceptable patient scanning times.<<ETX>>

Review of convergent beam tomography in single photon emission computed tomography

Investigation of convergent-beam single photon emission computed tomography (SPECT) is actively being pursued to evaluate its clinical potentials. Fan-beam, cone-beam, pin-hole and astigmatic collimators are being used with rotating gamma cameras having large crystal areas, to increase the sensitivity for emission and transmission computed tomography of small organs such as the thyroid, brain or heart. With new multi-detector SPECT systems, convergent-beam geometry offers the ability to simultaneously obtain emission and transmission data necessary to quantify uptake of radiopharmaceutical distributions in the heart. The development of convergent-beam geometry in SPECT requires the integration of hardware and software. In considering hardware, the optimum detector system for cone-beam tomography is a system that satisfies the data sufficiency condition for which the scanning trajectory intersects any plane passing through the reconstructed region of interest. However, the major development of algorithms has been for the data insufficient case of single planar orbit acquisitions. The development of these algorithms have made possible the preliminary evaluation of this technology and the imaging of brain and heart are showing significant potential for the clinical application of cone-beam tomography. Presently, significant research activity is pursuing the development of algorithms for data acquisitions that satisfy the data sufficiency condition and that can be implemented easily and inexpensively on clinical SPECT systems.

Influence of meal weight and caloric content on gastric emptying of meals in man.

This study was designed to assess the relative influence of meal weight and caloric content on gastric emptying of liquid and solid meals in man. A dual radioisotopic method which permits noninvasive and simultaneous measurement of liquid-and solid-phase emptying by external gamma camera techniques was employed. Nine healthy volunteer subjects ingested 50-,300-, and 900-g lettuce and water meals adjusted to either 68, 208, or 633 kcal with added salad oil. The following observations were made: (1) absolute emptying rates (grams of solid food emptied from the stomach per minute) increased directly and significantly with meal weight; (2) increasing meal total caloric content significantly slowed solid food gastric emptying but did not overcome the enhancing effect of meal weight; and (3) liquid emptying rates were uninfluenced by meal total kcal amount.

Effect of body posture on radionuclide measurements of gastric emptying

The purpose of this investigation was to compare the effect of body posture on gastric emptying measurements of radiolabeled meals. Eight healthy male subjects were studied on four separate days. During each study subjects were fed a standardized meal of beef stew labeled with technetium-99m sulfur colloid, and orange juice. Measurements of solid-phase gastric emptying rates were obtained by a gamma camera. Subjects were studied in the lying, sitting, standing, or combined sitting-standing postures. The results demonstrated that the lying position significantly slowed gastric emptying compared to all other positions. Conversely, a decrease in emptying times of 51% and 35% occurred in the combined sitting-standing position compared to the lying and sitting position. These results support a marked effect of body posture on the radionuclide measurement of gastric emptying.

The clinical use of radionuclide bone marrow imaging

Bone marrow aspiration and biopsy are excellent techniques for evaluating bone marrow, but this evaluation is limited to a small part of the total blood-forming organ. With the introduction of radionuclide bone marrow imaging, a simple technique became available that overcomes marrow sampling errors by giving a total body view of functioning marrow. Furthermore, the procedure is noninvasive and provides an atraumatic method for evaluating a number of clinical problems including a discrepancy between bone marrow histology and clinical status (possible marrow sampling error), the determination of amount of active marrow after radiation and chemotherapy when further therapy is being considered, detection of sites of extramedullary hematopoiesis, location of the optimal sites for bone marrow biopsy, the diagnosis and staging of diffuse hematologic disorders, detection of metastases, the diagnosis of bone marrow infarcts in hemolytic anemias, and detecting avascular necrosis of the femoral heads. There are two major classes of bone marrow agents: (1) those that are incorporated into the erythroid precursors such as radioiron and (2) colloids that are taken up by the reticuloendothelial system (RES). Indium-111 chloride was originally considered to be an erythropoietic agent but appears to share some properties of RES labels. The best label to use is dependent on the disease being evaluated.

Exercise increases solid meal gastric emptying rates in men.

Gastric emptying rates of radiolabeled beef stew meals were measured in 10 healthy, young (median age=27 years) male subjects on each of three randomly chosen study days. The subjects either (1) stood at rest, (2) walked on an exercise treadmill at 3.2 km/hr, or (3) at 6.4 km/hr during the study while gastric emptying was being monitored by externally positioned gamma cameras. Compared to the standing at rest study, exercise significantly increased gastric emptying (at rest emptying half-time (t1/2)=72.6±7.6 (sem) min; 3.2 km/hr t1/2=44.5±3.9 min, P=0.0051; 6.4 km/hr t1/2=32.9±1.9 min, P=0,0051). The 6.4 km/hr emptying time was significantly (P=0.0249) faster than the 3.2 km/hr emptying time. Thus, the amount of exercise is a physiological factor that alters solid meal gastric emptying rates.

The design and performance of a simultaneous transmission and emission tomography system

A commercial three-detector single-photon emission computed tomography (SPECT) system that enables simultaneous acquisition of transmission and emission data without increasing patient scanning time has been designed and manufactured. This system produces a reconstructed attenuation coefficient distribution that can be used to correct for photon attenuation in the emission reconstruction. The three detectors with fan-beam collimators are mounted to the gantry in a triangular arrangement. A transmission line source assembly was mounted at the focal line of one of the detectors and controlled to move in synchrony with the opposing fan-beam collimator. Data from transmission and emission sources at different energies were acquired in one detector, while the other two simultaneously acquired emission data. A transmission source of /sup 153/Gd was used with /sup 99m/Tc-labeled radiopharmaceuticals, and /sup 57/Co was used with /sup 201/Tl. Algorithms were developed to subtract crosstalk between transmission and emission energy windows in all three detectors. A transmission maximum-likelihood iterative algorithm was used to reconstruct the attenuation distribution, which was used in combination with an iterative maximum-likelihood expectation-maximization algorithm to compensate for the attenuation of the projection of the emission distribution. The results in phantom studies displayed greater uniformity of activity with attenuation-corrected reconstruction. This was demonstrated visually and quantitatively by using anterior-to-inferior ratios close to one and low spatial %rms error as a measure of improved uniformity.

Comparative effects of diltiazem, propranolol, and placebo on exercise performance using radionuclide ventriculography in patients with symptomatic coronary artery disease: Results of a double-blind, randomized, crossover study

The effects of oral diltiazem (120 mg), propranolol (100 mg), and placebo on exercise performance and left ventricular function were compared before and during symptom-limited supine bicycle exercise by means of multigated radionuclide ventriculography in 12 patients with documented, symptomatic coronary artery disease; a double-blind, randomized crossover protocol was used. Diltiazem increased ejection fraction (EF) at submaximal exercise (+7.0 absolute percentage points, p less than 0.02) and maximal exercise (+8.1 percentage points, p less than 0.01). Exercise EF was increased by 13.6 percentage points (p less than 0.02) in patients with decreased ventricular function (resting EF less than 50%). Propranolol had no effect on exercise EF at any stage, even when patients with EF less than 50% were excluded. The increase in total exercise time was significant after diltiazem (+27%, p less than 0.01) but not after propranolol (+16%, p = NS). As expected, propranolol decreased both resting (-9 bpm, p less than 0.01) and exercise heart rates (-27 bpm, p less than 0.001), whereas diltiazem had no significant effect. Propranolol decreased resting diastolic blood pressure (-8 mm Hg, p less than 0.02), exercise systolic (-27 mm Hg, p less than 0.001) and diastolic (-9 mm Hg, p less than 0.01) blood pressures, and rest (p less than 0.01) and exercise (p less than 0.001) double product. Diltiazem decreased resting systolic blood pressure (-9 mm Hg, p less than 0.01) and both resting (-8 mm Hg, p less than 0.001) and exercise (-9 mm Hg, p less than 0.01) diastolic blood pressures.(ABSTRACT TRUNCATED AT 250 WORDS)

Gastric emptying after gastric interposition for cancer of the esophagus or hypopharynx

Transhiatal esophagectomy with primary anastomosis to the stomach (gastric pull-up) is an attractive surgical alternative to colic interposition in patients with cancer of the esophagus and hypopharynx. However, the lack of intrinsic gastric peristalsis and complaints by patients ol postprandial regurgitation prompted us to measure the effect of body posture on the rates of gastric emptying in these patients. The rates of solid and liquid gastric emptying were measured in 14 patients who had undergone gastric interposition for esophageal and hypopharyngeal carcinoma. Rates of emptying were measured in both the supine and upright position using a dualisotope radiolabeling technique. In these patients, the rate of gastric emptying of both solids and liquids was significantly slower in the supine position than in the upright position. Emptying in supine patients was also prolonged when compared with supine normal volunteers. Conversely, the upright rate of solid and liquid emptying in the patients was accelerated when compared with published values for upright normal volunteers. We conclude that gastric emptying after gastric interposition is dependent on upright posture after meals.Transhiatal esophagectomy with primary anastomosis to the stomach (gastric pull-up) is an attractive surgical alternative to colic interposition in patients with cancer of the esophagus and hypopharynx. However, the lack of intrinsic gastric peristalsis and complaints by patients of postprandial regurgitation prompted us to measure the effect of body posture on the rates of gastric emptying in these patients. The rates of solid and liquid gastric emptying were measured in 14 patients who had undergone gastric interposition for esophageal and hypopharyngeal carcinoma. Rates of emptying were measured in both the supine and upright position using a dual-isotope radiolabeling technique. In these patients, the rate of gastric emptying of both solids and liquids was significantly slower in the supine position than in the upright position. Emptying in supine patients was also prolonged when compared with supine normal volunteers. Conversely, the upright rate of solid and liquid emptying in the patients was accelerated when compared with published values for upright normal volunteers. We conclude that gastric emptying after gastric interposition is dependent on upright posture after meals.