A mobile tomographic gamma camera system for acute studies

A mobile tomographic gamma camera system, called Cardiotom Mark 1, has been developed for imaging the myocardium and other small organs. The Cardiotom system is based on a tomographic technique, ectomography, which is a limited view angle method using a rotating slant hole collimator (RSHC) and a stationary detector to produce projection images. This enables the ectomographic system to be implemented as a mobile system. With the system developed, almost 200 perfusion studies have been performed. The system is based on a second-hand detector and a 30° RSHC. By segmenting the collimator, total system efficiency is increased and acquisition time can be reduced by a factor equal to the number of segments. The system developed is PC-based and totally self-contained with data acquisition, reconstruction, and image presentation. The mobility of the system and the fact that the examination requires no patient cooperation enable acute studies of myocardial perfusion in the critically ill patient, either in the intensive care unit or the emergency room. A mobile system with three-dimensional imaging can offer new possibilities in cardiological research and diagnosis     

Cytochrome P-450 complex formation by dirithromycin and other macrolides in rat and human livers

Intraluminal ultrasonography of the common duct was performed in nine patients undergoing laparoscopic cholecystectomy, using a system comprising a 20-MHz crystal in a 95-cm, blunt-tipped 6F sheath, mechanically rotated at 1,800 rpm. The probe was introduced through an incision in the cystic duct and passed into the duodenum. When the catheter was withdrawn, excellent visualization of the common and cystic ducts and lower end of the common hepatic duct was achieved. In seven patients, the biliary tree was normal. A small calculus was discovered in the common duct in one patient. This stone was not seen on a subsequent cholangiogram and was subsequently retrieved. An additional patient had mucus or sludge noted in the duct, which cast no acoustic shadow and thus was distinguished from calculi. The technique was fast, efficient, and easy to perform in this small group of patients and holds promise for screening the common duct pathology during laparoscopic cholecystectomy.     

The SIMON project: model-based signal acquisition, analysis, andinterpretation in intelligent patient monitoring

The authors describe SIMON (signal interpretation and monitoring), an approach which combines static domain-specific information, which relates variables and alarm events, with dynamic information provided by a model. It is currently being tested for the monitoring of neonates in the intensive care unit. The model component is responsible for estimating the state of the monitored system, predicting the evolution of the system's variables and parameters, and establishing a monitoring contest. This information is then used by the DA (data abstraction) and the data acquisition modules to plan a monitoring strategy to filter, rank, and abstract incoming data. Faults and artifact models included in the DA permit the low-level detection of noise-contaminated episodes. The adaptation of the monitoring strategy to these changes in the environment effectively shields the model from untrustworthy information and thus increases the reliability and robustness of the system. The scheduling mechanism included in the DA permits a continuous evaluation of the system load as well as an ability to process all its tasks     

Human corneal endothelial layer repair during organ culture

Circular freeze-thaw endothelial wounds were created on paired human corneas. Ultrastructural and physiological studies were performed after organ culture (OC) incubation at 37 C from 1 to 21 days as well as on fresh noncultured controls. As early as 24 hours after injury, OC corneas demonstrated ultrastructurally intact endothelial cells at the margin of the wound, elongating and sliding toward its center. All OC corneas were completely covered by ultrastructurally intact and physiologically functioning endothelial cells by seven days of OC. These cells were approximately twice normal size. Enlarged endothelial cells that maintained deturgescence function were seen in the wounded area after 14 and 21 days of OC. None of the fresh controls demonstrated deturgescence function and in none could ultrastructurally intact endothelial cells be found in the area of the wound. This confirms our hypothesis that during 37 C OC incubation, human corneal endothelium repairs defects in its layer by cells that are physiologically and ultrastructurally intact.     

Experimental autoimmune myasthenia gravis: a sequential and quantitative study of the neuromuscular junction ultrastructure and electrophysiologic correlations

Neuromuscular junction ultrastructure in rat forelimb digit extensor muscle was sequentially and quantitatively investigated in experimental autoimmune myasthenia gravis (EAMG). Experimental animals were immunized with highly purified eel electroplax acetylcholine receptor protein plus complete Freund's adjuvant and B pertussis vaccine; control animals received only adjuvant and vaccine. During the first 7 days (latent period) after immunization end-plate structure and neuromuscular transmission remained normal in the experimental group. Between day 7 and 11 (acute phase) mononuclear cells infiltrated those regions of muscle where the end-plates were located and there was intense degeneration of the postsynaptic regions with splitting away of abnormal junctional folds from the underlying muscle fibers. Macrophages entered the gaps thus formed and removed the degenerating folds by phagocytosis. The nerve terminals were displaced from their usual location but maintained their structural integrity. Neuromuscular transmission was blocked in many muscle fibers. Miniature end-plate potentias (MEPPs), detectable in only a few fibers, were of abnormally low amplitude. After day 11 (chronic phase) the nerve terminals returned to the highly simplified postsynaptic folds became reconstituted and again degenerated. Immature junctions with poorly differentiated postsynaptic regions and nerve sprouts near end-plates were also observed. In two animals relapsing during the chronic phase degeneration of the postsynaptic folds was more intense than in the other chronic-phase animals. The posysynaptic membrane length and length per unit area and the MEPP amplitudes were significantly decreased in all chronic phase animals and the decreases were greater in the relapsing than in the non-lapsing animals. Minor morphometric alterations were also observed in the nerve terminals. These might have been secondary to the postsynaptic changes. The postsynaptic region is the primary target of the autoimmune reaction in EAMG. The ultrastructural, morphometric and electrophysiological abnormalities of the end-plate in chronic EAMG resemble those which have been observed in human myasthenia gravis.     

Combinator evaluation of functional programs with logical variables

A technique is presented that brings logical variables into the scope of the well-known Turner method for normal order evaluation of functional programs by S, K, I combinator graph reduction. This extension is illustrated bySASL+LV, an extension of Turner's languageSASL in which arbitrary expressions serve as formal parameters, and parameter passage is done by unification. The conceptual and practical advantages of such an extension are discussed, as well as semantic pitfalls that arise from the attendant weakening of referential transparency. Only five new combinators (LV, BV, FN, FB and UNIFY) are introduced. The resulting object code is fully upward compatible in the sense that previously compiledSASL programs remain executable with unchanged semantics. However,read-only variable usage inSASL+LV programs requires amultitasking extension of the customary stack-based evaluation method. Mechanisms are presented for managing this multitasking on both single and multiprocessor systems. Finally, directions are mentioned for applying this technique to implementations involving larger granularity combinators, and fuller semantic treatment of logical variables (e.g. accommodation of failing unifications).Research was supported in part by the Marcus Wallenberg Foundation.Research supported in part by grant CCR-8704778 from the National Science Foundation, and by an unrestricted gift from Telefonaktiebolaget LM Ericsson, Stockholm.     

Determination of hydrogen in titanium alloys by cold neutron prompt gamma activation analysis

Cold neutron prompt gamma-ray activation analysis (CNPGAA) has proven useful for the analysis of hydrogen in titanium alloys. The analysis is nondestructive, measures the entire sample, and the results are independent of the chemical form of hydrogen present. We have used the technique to measure H mass fractions as low as 50 mg/kg in titanium-alloy jet-engine compressor blades and to measure hydrogen in standards for neutron tomography.