Sabia virus incident at Yale University.

An incident involving a human exposure to a newly isolated arenavirus, Sabia virus, in the Yale Arbovirus Research Unit occurred at Yale University on August 8, 1994. A senior-level visiting research scientist was exposed to Sabia virus while purifying the virus from a large volume of tissue culture fluid. The exposure resulted in development of a Sabia virus infection followed by recovery of the patient. The incident resulted in a comprehensive review by a Yale faculty committee and an external expert committee. As a result, a number of new practices and procedures were added to Yale's biosafety policy for investigating infectious agents in BL-3 facilities.

Radiation safety as part of a comprehensive university occupational health and safety program.

Rutgers University has developed an integrated occupational health and safety program incorporating the disciplines of radiation protection, chemical hygiene, industrial hygiene, occupational safety, hazardous substance disposal, and environmental control. The program was implemented by the Department of Radiation and Environmental Health and Safety which was organized in a nontraditional way to provide an interdisciplinary resource and service to a large state university community. In the relatively short period of time that the new organization functioned at full capacity, the strengths of the new organization as well as a few weaknesses have become apparent. We present here a short discussion of the reorganization activities and the lessons learned.

The nature of the background in radionuclide ventriculography: deductions from the mathematical behaviour of the ejection fraction.

The relationship between the ejection fractions calculated from 'uncorrected' radionuclide time activity curves (UEF) and angiographic ejection fractions (AEF) in 200 catheterized patients yielded the regression equation AEF = 1.74 UEF + 0.21. It follows from this linear relationship that the left ventricular ejection fraction can be estimated by linear regression without explicit background correction: RREF = 1.74 UEF + 0.21, where RREF is the radionuclide regression ejection fraction. We first investigated the possibility that changes in photon self-attenuation within the cardiac chambers cause the observed mathematical characteristics of the cardiac background, B. Self-attenuation was calculated for cylindrical and spherical ventricular models. The results were insensitive to the particular geometry and would have only a small effect on the observed EF. Alternatively, the 'background' may result from extra-ventricular radiation scattering from the heart into the detector. If we assume that B should be proportional to the ventricular scattering volume, Bd = Kd EDC for diastole and Bs = Ks ESC for systole, the background corrected ejection fraction will be BCEF = K UEF + (1-K) where K = (1-Ks)/(1-Kd). This agrees with the form of the empirical regression equation.

Dynamic bone imaging in the differential diagnosis of skeletal lesions.

Dynamic bone imaging differs from routine multiphase bone scintigraphy by the use of time-activity curves (TACs) and quantitation of data. TACs were divided into an arterial plus blood pool phase (first 60 s at 1 frame/s) and a subsequent early bone uptake phase (24 min at 1 frame/min). Ratios of normalized integrals, from analogous regions were calculated to determine whether blood flow was abnormal. A key feature of the technique is the monitoring of the flow proximally and distally to the area of involvement. This was of importance in distinguishing between two diseases producing the same degree of local hyperemia. Dynamic bone imaging was applied to the differential diagnosis of arthritis, septic arthritis, cellulitis, osteomyelitis, tumor, avascular necrosis, Charcot joint, Legg-Perthes (LP) disease, and Osteochondritis Dissecans (OCD). Although the method is straightforward, there are technical and clinical factors that may affect interpretation of data. Asymmetries in flow may arise due to injection technique, interfering activity of bladder and/or bowel, vascular abnormalities, AV malformation, and venous backflow. The dynamic study is also sensitive to the effects of various modes of therapy. Consideration must be given to these technical and clinical factors for the avoidance of pitfalls in interpretation of the dynamic study.

Differentiation of Charcot joint from osteomyelitis through dynamic bone imaging.

The bone scans of 25 patients with a clinical diagnosis of diabetic osteoarthropathy (Charcot joint) of the ankle and foot were analysed using the technique of dynamic bone imaging. The analysis of time-activity curves generated over the Charcot joint, the contralateral joint and the bone above the Charcot joint, produces characteristic patterns that are distinguishable from the ones observed for osteomyelitis. Recently it has been shown that the significance of dynamic bone imaging resides in its correlation to physiological and morphological components of bone. The difference in the blood supply to the long bones has been suggested as an explanation for the difference in time-activity curve patterns.

Pathophysiologic interpretation of time activity curves in dynamic bone imaging.

Reported here is a theoretical model based on a literature review correlating the 60 sec/25 min time activity curves (TAC) of dynamic bone imaging with the histologic components of bone. Information regarding healing versus nonhealing as well as a histophysiologic description of ongoing disease is obtainable from TACs of paired disease and nondiseased limbs. The TACs reflect the movement of Tc-99m MDP complexes across histologic compartments to reach the amorphous calcium phosphate (ACP) regions. These complexes must exit the bone capillaries, pass through the perivascular space, cross the osteoblastic barrier, enter the bone fluid space, and traverse collagen osteoid to reach ACP. The presence of diseases such as osteomyelitis, cellulitis, and degenerative arthritis and septic arthritis variously affect these spaces to cause typical perturbations in the TACs. The distinction of these patterns were observed in 48 patients, 12 per category. The model that explains how 60 sec/25 min TACs can reflect the histologic status of ongoing bone disease was applied to these disorders.

Computerized blood flow analysis for decision making in the treatment of osteochondritis dissecans.

Patients presenting the radiologic appearance of osteochondritis dissecans (OCD) require a decision as to further treatment. This often requires an invasive procedure. The noninvasive technique of computerized blood flow analysis (CBFA) has been used in 13 patients with OCD. In clinically early disease (four patients), there is always decreased flow in the area distal to the OCD lesion. Patients with intermediate OCD (four patients) showed characteristics of healing reflected in increased flow to the OCD lesion. These patients were left under observation and underwent spontaneous healing. Patients who showed no increase in flow or had decreased flow in the area of involvement (four patients) were clinically found to be nonviable OCD and required surgical intervention. The technique of CBFA therefore holds promise for decision making in the management of this disease.

Dynamic bone scintigraphy in osteochondritis dissecans.

We report a retrospective study of eighteen patients with pain in the knee or ankle, eleven of whom had osteochondritis dissecans. In these patients the bone-flow time-activity curves were observed after an intravenous injection of a bolus of 99mTc MDP. The curves varied according to the severity of the clinical signs and symptoms. The diagnosis rate was 29% with static scintigraphy and this improved to 57% when dynamic flow studies were used. A positive pattern in the dynamic study together with radiographs and static scintigraphs raised the diagnosis rate to 100%; the sensitivity was 90%. These preliminary results show that dynamic bone scintigraphy holds promise as a technique for identification and management of this condition.

Asymmetric distribution of left ventricular asynergy in coronary artery disease and its relation to coronary stenoses.

In 100 patients with coronary artery disease (CAD), the prevalence and severity of asynergy was determined for 9 left ventricular (LV) segments by both radionuclide and contrast angiography. The anterior, septal and lateral LV walls had significantly more prevalent and more severe asynergy in the medial segments than in the basal segments. In contrast, the inferior LV wall exhibited equally severe asynergy in both the medial and basal segments. In general, asynergy was most severe in the apical, medial septal, medial inferior and basal inferior LV segments. This asymmetric distribution of LV asynergy could not be explained by the distribution of occlusions or significant stenoses in the arterial tree, which were relatively uniformly distributed among the left anterior descending (32%), left circumflex (29%) and right (26%) coronary arteries. It is postulated instead that the asymmetric distribution of LV asynergy results from asymmetry of the coronary arterial tree supplying the left ventricle and that the prevalence of asynergy in an LV segment is directly related to its vascular distance from the coronary ostia. Unlike the relatively direct supply of the left anterior descending and circumflex arteries to the basal segments of the anterior, septal and lateral LV walls, the arterial supply to the basal inferior wall begins only after the right or dominant circumflex artery has traversed the length of the atrioventricular groove, significantly increasing its susceptibility to the pressure attenuation and occlusive jeopardy of more proximal stenoses.

Computerized blood-flow analysis in osteochondritis dissecans.

A retrospective review of static images and computerized blood flow studies (CBFS) in patients with osteochondritis dissecans (OCD) suggests that CBFS maybe useful in following the clinical course of this disease.

Inferoseptal myocardial infarction: another cause of precordial ST-segment depression in transmural inferior wall myocardial infarction?

Electrocardiographic ST-segment depression in the anterior precordial leads is a frequent observation during the initial hospital phase of acute transmural inferior myocardial infarction (MI), but is of uncertain significance. No available clinical studies have examined the prevalence of inferoseptal necrosis complicating inferior MI. Therefore, the clinical course, electrocardiographic features, radionuclide angiograms and cardiac enzyme changes in 57 patients with transmural inferior MI who did not have prior anterior or concomitant "true posterior" MI, associated anterior or posterolateral asynergy by radionuclide ventriculography, or left or right bundle branch block were reviewed retrospectively. Patients were categorized according to the presence (group A) or absence (group B) of precordial ST-segment depression and according to the presence (group I) or absence (group II) of radionuclide septal wall motion abnormalities. There were no significant differences in global left ventricular ejection fraction (group A, 49 +/- 8, group B, 52 +/- 41; group I, 51 +/- 7, group II, 51 +/- 6), right ventricular ejection fraction (group A, 45 +/- 9, group B, 42 +/- 7; group I, 43 +/- 8, group II, 41 +/- 8), or clinical outcome in the hospital. However, chi-square analysis revealed a significant (p less than 0.05) association between the presence or absence of septal asynergy and the presence or absence of precordial ST depression. In addition, average peak creatine kinase elevation (group I, 761 +/- 164 IU; group II, 698 +/- 178 IU) attained marginal significance by paired t test (p = 0.06). Precordial ST-segment depression during transmural inferior MI is frequently associated with septal asynergy by gated radionuclide angiography (15 of 26 patients, 58%).(ABSTRACT TRUNCATED AT 250 WORDS)

Left ventricular asynergy in electrocardiographic "posterior" myocardial infarction.

P2 300 selected patients, scalar electrocardiograms and contemporaneous radionuclide angiograms were analyzed retrospectively to assess the association between prominent right precordial R waves (duration greater than or equal to 0.04 second, R greater than or equal to S in lead V1 or V2), traditionally considered diagnostic of "posterior" infarction, and asynergy in various left ventricular segments. Mathematical methods for analysis of association between nonparametric variables clearly demonstrated that prominent right precordial R waves were strongly associated with asynergy of the basal lateral left ventricular wall, although asynergy of adjacent inferior and lateral segments was common. With the exclusion of right ventricular hypertrophy and bundle branch block, a prominent R wave in lead V1 exhibited a high specificity (greater than to 99%), a high positive predictive value (91%) and a low sensitivity (36%) for diagnosing basal lateral myocardial infarction. A prominent R wave in lead V2 exhibited a higher sensitivity (61%), a somewhat lower specificity (95%) and a significantly lower positive predictive value (76%). A newly developed criterion for such infarction--a prominent R wave in lead V2 and a Q wave inferior infarction--had intermediate characteristics and may be more clinically useful. The most common reasons for the decreased sensitivities of all three criteria were left ventricular hypertrophy or associated anterior myocardial infarction. These data demonstrate that prominent right precordial R waves are clinically useful in identifying inferior and lateral wall infarctions that involve the basal lateral left ventricular segment. Confusion results primarily from inappropriate use of the electrocardiographic term "posterior" for such infarctions.

Atlas of computerized blood flow analysis in bone disease.

The role of computerized blood flow analysis in routine bone scanning is reviewed. Cases illustrating the technique include proven diagnoses of toxic synovitis, Legg-Perthes disease, arthritis, avascular necrosis of the hip, fractures, benign and malignant tumors, Paget's disease, cellulitis, osteomyelitis, and shin splints. Several examples also show the use of the technique in monitoring treatment. The use of quantitative data from the blood flow, bone uptake phase, and static images suggests specific diagnostic patterns for each of the diseases presented in this atlas. Thus, this technique enables increased accuracy in the interpretation of the radionuclide bone scan.

The use of bone scanning for the diagnosis and management of musculoskeletal trauma.

Bone scanning provides a unique way of monitoring early metabolic changes in bone and its adjacent soft tissues after trauma. An abnormal scan may often precede radiographic changes by days or weeks. This accounts for its usefulness in the early diagnosis of occult fractures and in fractures not clinically suspected or seen on initial x-ray films in the patient with multiple trauma. Dynamic imaging along with static imaging can be used to evaluate fracture healing and predict delayed union and nonunion. The combined technique is useful in assessing many of the complications arising after trauma and provides a reliable method of observing their treatment. It is also a useful noninvasive technique in the evaluation of pathologic fractures. Bone scanning is becoming an increasingly useful adjunctive procedure in the diagnosis and management of musculoskeletal trauma. However, as with any diagnostic technique, it provides only part of the overall picture and must always be carefully correlated with the history, physical findings, radiographic changes, and other laboratory data.

Calculation of the left ventricular ejection fraction by gated radionuclide angiography without direct background correction.

The mathematical characteristics of the cardiac background were studied in 50 patients who underwent both gated radionuclide angiography and cardiac catheterization. The background-corrected ejection fraction (BCEF) was calculated in the standard manner using an operator-defined periventricular background region. The "uncorrected" ejection fraction (UEF) was calculated from the uncorrected left ventricular time-activity curve and compared to both the BCEF and the angiographic ejection fraction (AEF), UEF exhibited remarkable linear correlation with both BCEF and AEF. The empirically determined linear regression equation, AEF = 2.18 (UEF) + 0.13, allowed calculation of a radionuclide ejection fraction corresponding to angiographic methods without direct background correction. When measurement of the left ventricular ejection fraction using this linear regression method was tested prospectively in 25 catheterized patients, the radionuclide regression ejection fraction showed excellent linear correlation with AEF (r = 0.85) and minimal inter-observer variability.

Hemodynamic correlates of right ventricular ejection fraction measured with gated radionuclide angiography.

Right ventricular function was studied in 60 patients with equilibrium gated radionuclide angiography. The mean (+/- standard deviation) right ventricular ejection fraction in 20 normal subjects was 53 +/- 6 percent, a value in agreement with previous data from both radionuclide and contrast angiographic studies. This value was similar (55 +/- 7 percent) in 11 patients with coronary artery disease but normal left ventricular function. Radionuclide measurements of right ventricular ejection fraction were correlated with right heart hemodynamics. There was a significant negative linear correlation between right ventricular ejection fraction and mean pulmonary arterial pressure (r = -0.82) and between right ventricular ejection fraction and right ventricular end-diastolic pressure (4 = -0.67). Furthermore, patients with elevated right ventricular end-diastolic pressure and mean pulmonary arterial pressure had a more severely depressed ejection fraction than did those with an elevated mean pulmonary arterial pressure alone. Thus, an abnormal value for right ventricular ejection fraction by gated radionuclide angiography in the absence of primary right ventricular volume overload suggests abnormal right heart pressures, whereas a normal value excludes severe pulmonary arterial hypertension or an elevated right ventricular end-diastolic pressure.

Measurement of normal left atrial function with gated radionuclide angiography.

A method is described for measuring relative left atrial volume changes with gated radionuclide angiography, using an approximate computer-generated functional image to locate the atrial region of interest. M mode echocardiographic measurements of left atrial and left ventricular distances from the chest wall allowed calculation of a correction factor for the differential attenuation of atrial and ventricular photons. Background-corrected left atrial time-activity curves obtained from normal subjects exhibited excellent temporal resolution and were used to identify and quantitate the reservoir and contractile phases of left atrial volume change. In 20 normal subjects, the mean (+/- standard deviation) value for left atrial fractional emptying was 0.39 +/- 0.07. Expressed as fractions of the left ventricular stroke volume, mean values of the specific phases of atrial volume change were (1) reservoir volume 0.25 +/- 0.09, (2) contractile volume 0.29 +/- 0.10, and (3) conduit volume 0.46 +/- 0.12.