The performance of scintillation detectors for x rays and gamma rays is limited fundamentally by the statistics of the scintillation light and the resulting photoelectrons. This paper presents a new experimental approach to studying these statistics by observing correlations in the signals from two photodetectors. It is shown that the Fano factors (ratios of variance to mean), both for the number the photoelectrons produced on the photocathode of the photomultiplier and for the underlying number of scintillation photons, can be deduced from these correlations. For LaBr3(Ce) and 662 keV gamma rays, the photopeak signals obtained by photomultipliers on opposite faces of a thin sample are negatively correlated, and the Fano factor for the photoelectrons is significantly less than one. The inferred Fano factor for the optical photons is very small, indistinguishable from zero within experimental error.

Including time-of-flight information in positron emission tomography (PET) reconstruction increases the signal-to-noise ratio if the timing information is sufficiently accurate. We estimate timing information by analyzing sampled waveforms, where the sampling frequency and number of samples acquired affect the accuracy of timing estimation. An efficient data-acquisition system acquires the minimum number of samples that contains the most timing information for a desired resolution. We describe a maximum-likelihood (ML) estimation algorithm to assign a time stamp to digital pulses. The method is based on a contracting-grid search algorithm that can be implemented in a field-programmable gate array and in graphics processing units. The Fisher-information (FI) matrix quantifies the amount of timing information that can be extracted from the waveforms. FI analyses on different segments of the waveform allow us to determine the smallest amount of data that we need to acquire in order to obtain a desired timing resolution. We describe the model and the procedure used to simulate waveforms for ML estimation and FI analysis, the ML-estimation algorithm and the timing resolution obtained from experimental data using a LaBr3:Ce crystal and two photomultiplier tubes. The results show that for lengthening segments of the pulse, timing resolution approaches a limit. We explored the method as a function of sampling frequency and compared the results to other digital time pickoff methods. This information will be used to build an efficient data-acquisition system with reduced complexity and cost that nonetheless preserves full timing performance.

Abiotrophia defectiva, also known as nutritionally variant streptococcus, is part of the normal flora of the oral cavity and urogenital and intestinal tracts and is a rare cause of infective endocarditis. It is fastidious or difficult to culture and associated with high rates of septic embolization, treatment failure and mortality. We describe an unusual presentation of infective endocarditis with severe mitral valve regurgitation due to Abiotrophia defectiva in an immunocompetent patient. After a complicated hospital course, surgical replacement of both the mitral and aortic valves was performed. We suggest that this patient likely had subacute infective endocarditis before diagnosis and treatment of her urinary tract infection, and following treatment failure, she developed life-threatening infective endocarditis. This case report highlights that patients with Abiotrophia defectiva infections are at high risk for infective endocarditis and that the clinical progression from this infection can be slow, with difficulty isolating the pathogen, which can significantly impact patient outcome.

H ealth care-associated infections (HAIs) are a global problem that result in an increase in patient morbidity and mortality. 1,2 Multiple efforts to decrease the occurrence of these complications have taken place, thus improving patient outcome. Recognizing that health careassociated complications are a patient safety issue and a public health threat, the United States, through the Centers for Disease Control and Prevention (CDC), has emphasized the importance of eliminating these complications. 3,4 Techniques to prevent HAI have involved the development of surveillance methods to detect both endogenous and exogenous sources of infection, as well as data-reporting systems to aid in identifying both causative and modifiable risk factors for HAI. A variety of strategies has resulted from these techniques. One impact of these initiatives has resulted in health care providers in all fields, including anesthesia, becoming engaged in the process of using various avoidance strategies with the goal of preventing and ultimately eradicating HAI. This review will focus on the prevention of complications associated with mechanical ventilation through the use of "care bundles" and discussion of the new definitions and their implications.Ventilator-associated pneumonia (VAP) is one example of an area in which specific guidelines have been created in an attempt to reduce the incidence of health care-associated complications, by implementing a group of evidence-based care interventions. Loosely termed care bundles, these care interventions are designed to decrease the rate of the targeted complications. In the case of VAP, the targeted rate initially set by the CDC and the Institute for Healthcare Improvement (IHI) was zero. The care bundle preventative strategies for VAP, including its applied rationale based on the evidence, will be discussed, as well as its limitations and shortcomings. VAP CARE BUNDLEIn 2001, the IHI recognized care of the ventilated patient as a top priority and identified the most significant complications associated with mechanically ventilated patients as VAP, venous thromboembolism, and stress-induced gastrointestinal bleeding. Four elements of care were identified as key factors in reducing these complications, with a fifth element added in 2010. The current IHI care bundle therefore consists of 5 interventions targeted to improve outcomes in mechanically ventilated patients. These include (1) head of bed (HOB) elevation, (2) daily sedation holiday with assessment for possible extubation, (3) daily oral care with chlorhexidine, (4) deep venous thrombosis prophylaxis, and (5) peptic ulcer prophylaxis. a The first 3 elements are the components that have been examined for the prevention of VAP (Table 1); the remaining 2 have been studied to reduce overall morbidity and mortality in patients who are mechanically ventilated and are not associated with a decrease in the incidence of VAP.The IHI VAP bundle has some recognized limitations and has been criticized by a number of authors. 5,6 These criticisms in...