Random Euclidean matching problems in one dimension.

We discuss the optimal matching solution for both the assignment problem and the matching problem in one dimension for a large class of convex cost functions. We consider the problem in a compact set with the topology both of the interval and of the circumference. Afterwards, we assume the points' positions to be random variables identically and independently distributed on the considered domain.

Finite-size corrections in the random assignment problem.

We analytically derive, in the context of the replica formalism, the first finite-size corrections to the average optimal cost in the random assignment problem for a quite generic distribution law for the costs. We show that, when moving from a power-law distribution to a Γ distribution, the leading correction changes both in sign and in its scaling properties. We also examine the behavior of the corrections when approaching a δ-function distribution.

The ECAT ART Scanner for Positron Emission Tomography. 2. Research and Clinical Applications.

The ECAT ART is a low-cost positron emission tomography (PET) scanner design for which increasing interest in the use of PET, and specifically (18)FDG PET for oncological studies, has stimulated a demand. Although targeted primarily for the clinical market, the performance of the ART scanner can also meet the demands of a research environment where, in addition to [(18)F], more challenging, shorter-lived isotopes such as [(11)C], [(13)N] and [(15)O] are used. The ART has been used successfully to perform quantitative (18)FDG studies, blood flow measurements with [(15)O]water, and brain mapping studies with [(15)O]water (activation).

Image analysis in patients with cancer studied with a combined PET and CT scanner.

Purpose: To compare combined whole-body PET and CT images of different cancers with PET images alone.

Materials And Methods: Thirty-two patients with known or possible cancers were examined using a combined positron emission tomographic (PET) and computed tomographic (CT) scanner. All data were acquired using this same combined scanner.

Whole-body FDG positron emission tomographic imaging for staging esophageal cancer comparison with computed tomography.

Purpose: The aim of the authors in this study was to critically evaluate the role of whole-body positron emission tomographic (PET) imaging with fluorine-18 fluorodeoxyglucose (FDG) in staging esophageal cancer, and further to compare this method with conventional imaging with computed tomography (CT).

Materials And Methods: The authors performed independent, blinded retrospective evaluations of FDG PET images obtained in 47 patients referred for the initial staging of esophageal cancer before minimally invasive surgical staging. Twenty PET studies from patients with nonesophageal thoracic cancers were randomly selected for inclusion in the PET readings.

A study of injected dose for brain mapping on the ECAT HR+: activation maps for a parametric verbal working memory task.

The success of the 15O-water PET technique to localize statistically significant changes in regional cerebral blood flow is dependent on factors such as the activity level injected and the magnitude of the flow change. Undetectable changes may occur if insufficient activity is injected leading to high levels of statistical noise or the task performed results in only small changes in blood flow. To explore the relationship between injected activity and statistical significance, we performed a series of studies with the ECAT EXACT HR+, a high resolution PET tomograph.

A method for the assessment of the functional neuroanatomy of human sleep using FDG PET.

Although sleep is characterized by relative behavioral inactivity, cortical activity is known to cycle in well-defined periods across this state. Cognitive function during sleep has been difficult to define, although disturbances in sleep are known to result from, and to cause, various human pathologies, including neuropsychiatric disorders. Assessment of brain function in humans (related to cognitive operations) during sleep has been limited, until recently, to surface electrophysiologic recordings that limit analysis of regional function, particularly in deep structures.