Biomedical subjects

John W Fisher

Publications and source records attributed to John W Fisher.

8 recordsLinked to original sources

PubMed2005

A nonparametric statistical method for image segmentation using information theory and curve evolution.

In this paper, we present a new information-theoretic approach to image segmentation. We cast the segmentation problem as the maximization of the mutual information between the region labels and the image pixel intensities, subject to a constraint on the total length of the region boundaries. We assume that the probability densities associated with the image pixel intensities within each region are completely unknown a priori, and we formulate the problem based on nonparametric density estimates. Due to the nonparametric structure, our method does not require the image regions to have a particular type of probability distribution and does not require the extraction and use of a particular statistic. We solve the information-theoretic optimization problem by deriving the associated gradient flows and applying curve evolution techniques. We use level-set methods to implement the resulting evolution. The experimental results based on both synthetic and real images demonstrate that the proposed technique can solve a variety of challenging image segmentation problems. Futhermore, our method, which does not require any training, performs as good as methods based on training.

Algorithms↗

PubMed2005

Advance directives in action in a regional palliative care service: "road testing" the provisions of the Medical Treatment Act 1988 (VIC).

In order to explore the usefulness and acceptability of the provisions of the Medical Treatment Act 1988 (Vic) for palliative care patients in a rural region in Victoria, Australia, between July and December 2004 patients were given information explaining the Act and the opportunity to discuss it with the research officer. Grounded theory methodology was used to evaluate client responses. Findings suggested that palliative care patients are willing to engage in advance care planning but they have to be well enough and need skilled, practical, face-to-face assistance to complete the required legal forms. Written materials alone are not adequate, but provide the opportunity for medical staff to have conversations about death and dying. Doctors and nurses should understand the provisions of the Act to assist patients and families. It is recommended that advance care planning, appropriate to the jurisdiction, be an integral part of the palliative care assessment process.

Adult↗

PubMed2004

Synthesis of (+/-)-secosyrin 1 and a formal synthesis of (-)-secosyrin 1.

[reaction: see text] A short synthesis of (+/-)-secosyrin 1 is presented that starts from an electron-deficient furan; reductive alkylation under Birch conditions gives rapid access to the natural product skeleton. Two aspects of stereoselectivity are explored, the first being directed dihydroxylation of a homoallylic alcohol. Second, the facial selectivity obtained during reduction of a highly substituted cyclic ketone was examined. Finally, our synthesis was rendered enantioselective by the reduction of a furan bearing a chiral auxiliary.

Catalysis↗

PubMed2004

The application of volume-outcome contouring in data warehousing.

Despite a compelling body of published research on the nature of provider volume and clinical outcomes, healthcare executives and policymakers have not managed to develop and implement systems that are useful in directing patients to higher volume providers via selective referral or avoidance. A specialized data warehouse application, utilizing hospital discharge data linked to physician biographical information, allows detailed analysis of physician and hospital volume and the resulting pattern (contour) of related outcomes such as mortality, complications, and medical errors. The approach utilizes a historical repository of hospital discharge data in which the outcomes of interest, important patient characteristics and risk factors used in severity-adjusting of the outcomes are derived from the coding structure of the data.

Diagnosis-Related Groups↗

PubMed2003

A unified variational approach to denoising and bias correction in MR.

We propose a novel bias correction method for magnetic resonance (MR) imaging that uses complementary body coil and surface coil images. The former are spatially homogeneous but have low signal intensity; the latter provide excellent signal response but have large bias fields. We present a variational framework where we optimize an energy functional to estimate the bias field and the underlying image using both observed images. The energy functional contains smoothness-enforcing regularization for both the image and the bias field. We present extensions of our basic framework to a variety of imaging protocols. We solve the optimization problem using a computationally efficient numerical algorithm based on coordinate descent, preconditioned conjugate gradient, half-quadratic regularization, and multigrid techniques. We show qualitative and quantitative results demonstrating the effectiveness of the proposed method in producing debiased and denoised MR images.

Algorithms↗

PubMed2003

A unified statistical and information theoretic framework for multi-modal image registration.

We formulate and interpret several registration methods in the context of a unified statistical and information theoretic framework. A unified interpretation clarifies the implicit assumptions of each method yielding a better understanding of their relative strengths and weaknesses. Additionally, we discuss a generative statistical model from which we derive a novel analysis tool, the auto-information function, as a means of assessing and exploiting the common spatial dependencies inherent in multi-modal imagery. We analytically derive useful properties of the auto-information as well as verify them empirically on multi-modal imagery. Among the useful aspects of the auto-information function is that it can be computed from imaging modalities independently and it allows one to decompose the search space of registration problems.

Algorithms↗

PubMedDate not supplied

Hispanic health status in Orange County, Florida.

PURPOSE: To assess the health status of the Hispanic population of Orange County, Florida. METHODS: The methodology utilized secondary data for 66 ethnically identified indicators in a comparative framework applied for a 5-year period (1997-2001). FINDINGS: Orange County Hispanics are younger with lower per capita income than their Florida peers, less likely to be White, and much more likely to be of Puerto Rican origin. Relative to the Hispanic populations in the selected peer counties and statewide, Orange County Hispanics have higher age-adjusted death rates for a majority of disease categories and conditions, such as breast, lung, and prostate cancers; chronic liver disease and cirrhosis; diabetes mellitus; pneumonia and influenza; stroke; acquired immunodeficiency syndrome; motor vehicle accidents; and infant, neonatal, and child mortality. Orange County Hispanics did better in comparison to Orange non-Hispanics, with lower age-adjusted death rates for major causes of death such as heart disease, cancer, and stroke. However, for many indicators, the 5-year trends for Orange County Hispanics are moving in an unfavorable direction in contrast to the trends for non-Hispanics, which are either stable or improving. CONCLUSION: Comparative assessments of Hispanic populations using secondary data enable the development of a comprehensive health status profile. However, this approach is currently constrained by the limited number of ethnically identified indicators and, especially for Hispanics, problems in the accuracy and consistency of the assignment to racial categories and subsequent reporting.

Adolescent↗

PubMedDate not supplied

Notoginseny cream in the treatment of phlebitis.

This study investigated the curative effects of notoginseny cream versus Hirudoid cream in the treatment of postinfusion phlebitis. Sixty-five patients who received peripheral infusion therapy during a 20-month period and had developed phlebitis were divided randomly into two groups. Group A was treated with notoginseny cream, a topical Chinese medicine developed and produced by the pharmacological department of The Second Affiliated Hospital of Sun Yat-Sen University. Group B was treated with heparinoid cream (Hirudoid, a commercial product from Germany). Significantly fewer applications of notoginseny cream were required to bring about the disappearance of signs and symptoms of phlebitis in the group A patients as compared with the group B patients for the same effect. The actual time of disappearance of the signs and symptoms of phlebitis also were significantly shorter in patients treated with notoginseny cream than with heparinoid cream.

Administration, Cutaneous↗