Positron emission tomography compartmental models.

The current article presents theory for compartmental models used in positron emission tomography (PET). Both plasma input models and reference tissue input models are considered. General theory is derived and the systems are characterized in terms of their impulse response functions. The theory shows that the macro parameters of the system may be determined simply from the coefficients of the impulse response functions. These results are discussed in the context of radioligand binding studies. It is shown that binding potential is simply related to the integral of the impulse response functions for all plasma and reference tissue input models currently used in PET. This article also introduces a general compartmental description for the behavior of the tracer in blood, which then allows for the blood volume-induced bias in reference tissue input models to be assessed.

On a class of support vector kernels based on frames in function Hilbert spaces.

There has been an increasing interest in kernel-based techniques, such as support vector techniques, regularization networks, and gaussian processes. There are inner relationships among those techniques, with the kernel function playing a central role. This article discusses a new class of kernel functions derived from the so-called frames in a function Hilbert space.

Implications of arterial pressure variation in patients in the intensive care unit.

Positive-pressure ventilation alters stroke volume by transiently increasing intrathoracic pressure and thereby decreasing preload. This phasic variation in stroke volume results in a cyclic fluctuation in arterial pressure with a phase length equal to the respiratory rate. Measuring ventilation-induced arterial pressure variation allows the clinician to predict the cardiovascular response to changes in intravascular volume status. Thus, one may predict preload responsiveness because the greater the amount of ventilation-associated arterial pressure variation, the greater the patient's preload responsiveness. This variation in arterial pressure can been defined as a variation in either systolic pressure or pulse pressure. Although pulse pressure gives a clearer signal, systolic pressure variation may be easier to measure bedside without invasive hemodynamic monitoring. Newer methods of quantifying this arterial pressure variation include the respiratory systolic variation test, which can performed without an apneic baseline, and the pulse pressure variation, a potentially more accurate measure of preload responsiveness.

The relevance vector machine technique for channel equalization application.

The relevance vector machine (RVM) technique is applied to communication channel equalization. It is demonstrated that the RVM equalizer can closely match the optimal performance of the Bayesian equalizer, with a much sparser kernel representation than that is achievable by the state-of-art support vector machine (SVM) technique.

CQI action team: responding to the detoxification patient.

BACKGROUND: The management of detoxification patients is a complex interdisciplinary effort requiring involvement, cooperation, and understanding from staff at all levels of the facility. In 1992-93, alcohol-related diagnoses were the highest admission diagnosis at the Royal C. Johnson Veterans Affairs Medical Center (VAMC). Yet only 44% of the detoxification patients admitted to the VAMC were placed in beds specifically designed for detoxification. Initially, the action team believed that the issues were apparent and that the problems were the result of uncooperative and noncompliant providers who were not following established policy. METHODS AND RESULTS: Data analysis of admission and discharge trends, laboratory results, and bed census revealed discrepancies with several widespread myths held by local health care workers. These misperceptions and attitudes often interfered with treatment. CONCLUSIONS: Recommended changes included the development of a clinical pathway for the detoxification patient, implementation of an alcohol withdrawal assessment tool to manage and treat the patient at risk for experiencing alcohol withdrawal, and hospitalwide education on management of the detoxification patient.