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Biomedical subjects

R F Wagner

Publications and source records attributed to R F Wagner.

At least 55 records · Page 3Linked to original sources
PubMed1997

Mucoepidermoid carcinoma with cutaneous presentation.

Mucoepidermoid carcinomas are malignant neoplasms that rarely involve the skin. Composed of both mucus-secreting cells and epidermoid-type cells in various proportions, mucoepidermoid carcinomas occur most commonly in salivary glands. In this case report, we describe a high-grade mucoepidermoid carcinoma with cutaneous involvement. Although this patient was referred for Mohs' micrographic surgery, further evaluation showed either direct or metastatic extension from the parotid gland to skin and distant metastases to the lung and bone. Despite extensive bone involvement, serum levels of ionized calcium, phosphorus, and lactate dehydrogenase remained normal. In view of the widespread metastases, the treatment plan was altered to radiotherapy and chemotherapy instead of surgery. Instructive lessons from this case include the recognition by dermatologists of this rare entity, the importance of a detailed history and complete evaluation of the patient before determining appropriate therapy, and the necessity of individualizing diagnostic tests to a particular patient.

Biopsy, Needle↗
PubMed1996

Primary cutaneous melanoma of the buttock: does injury from ultraviolet light play a role?

A 38-year-old man, initially referred for Mohs' surgery of a facial skin cancer, was found to have a thin (less than 0.5 mm thick, Clark Level II) primary cutaneous melanoma of the buttock. The melanoma, previously unnoticed by the patient, was 0.5 cm in diameter. Sunburn, a widely recognized risk factor for primary cutaneous melanoma, had occurred on the patient's buttocks during skinny dipping 20 years earlier. Traumatic injury due to ultraviolet light exposure may explain the subsequent development of some skin cancer on sites ordinarily protected by clothing.

Adult↗
PubMed1995

Quantitative assessment of myocardial ultrasound tissue characterization through receiver operating characteristic analysis of Bayesian classifiers.

OBJECTIVES: This work proposes a self-consistent assessment methodology for quantitative evaluation of any combination of diagnostic features, with the immediate goal of quantitatively assessing the discriminating power in diabetic patients of features derived from ultrasound backscatter from myocardium. BACKGROUND: Four features from analysis of left ventricular myocardial ultrasound backscatter have previously been shown to be sensitive to potentially cardiomyopathic changes in patients with insulin-dependent diabetes mellitus who have no overt heart disease. The measured features were significantly different between such patients and normal control subjects, as well as among groups of such patients with and without systemic complications of the disease. The quantitative discriminating potential of the features was not assessed. METHODS: Multivariate classifier functions were constructed and analyzed by using the methodology of the receiver operating characteristic curve, which allows quantitative assessment of the discriminating power of these features, alone or in combination. The area under the receiver operating characteristic curve--the true positive rate averaged over all false positive rates--was used as a summary measure of performance. RESULTS: In distinguishing patients with insulin-dependent diabetes mellitus from normal control subjects, the most discriminating combination of ultrasound features for the detection of such changes in these patients yielded receiver operating characteristic curves with area measures of approximately 0.80; for such patients with retinopathy the measure increased to 0.90. This performance is comparable to that of many commonly used diagnostic tests. CONCLUSIONS: A self-consistent set of evaluation methodologies has quantitatively demonstrated the sensitivity of four ultrasound backscatter features to otherwise latent changes in myocardial structure that accompany the evolution of insulin-dependent diabetes mellitus. The results are remarkable in themselves and suggest the potential of the features for the general field of cardiac ultrasound tissue characterization.

Bayes Theorem↗
PubMed1995

Pseudoepitheliomatous hyperplasia mistaken for cancer after delayed reconstruction.

Pseudoepitheliomatous hyperplasia (PEH) arises in areas of chronic inflammation and can be mistaken for squamous cell carcinoma, leading to unnecessary removal of more tissue. We present a study of 21 patients having delayed reconstruction of defects left by Mohs micrographic surgery (MMS) to remove facial skin cancers. Reconstruction was done at an average of 6 days after MMS. Four of these 21 patients (19%) had PEH in the wound margins. Presence of PEH did not correlate with age, sex delay in reconstruction, frequency of wound care, size or location of the defect, type of tumor, or smoking status. During an average 24-month follow-up, none of these four patients had tumor recurrence, suggesting that the benign diagnosis of PEH was correct. We detail the histologic features of PEH, and describe techniques for minimizing confusion with squamous cell carcinoma.

Carcinoma, Squamous Cell↗
PubMed1995

Informed consent and informed refusal.

BACKGROUND: This article continues our medicolegal series that addresses issues affecting current dermatology practice. Informed consent and informed refusal have become cornerstones of modern American healthcare, and can serve to facilitate communication and trust between physician and patient. METHODS: A format with an initial discussion of legal concepts is followed by hypothetical problems and a review of actual cases to illustrate the principles of informed consent and informed refusal. RESULTS: A valid informed consent from a competent patient should be obtained before initiating most dermatologic treatment. When a competent patient refuses a recommended medical test or procedure, the physician should make sure the patient understands the potential negative consequences of refusal. Some form of written documentation in the medical record is advised in either situation. CONCLUSION: Failure to obtain a patient's informed consent prior to beginning treatment or failing to obtain an informed refusal before accepting a patient's decision to forego a test or procedure may subject the dermatologist to multiple later allegations, most commonly negligence.

Adult↗
PubMed1995

Toward consensus on quantitative assessment of medical imaging systems.

Consensus has been developing over the past few decades on a number of measurements required for the laboratory assessment of medical imaging modalities. Nevertheless, understanding of the connection between these measurements and human observer performance in a broad range of tasks remains far from complete. Focusing primarily on projection radiography to provide concrete examples, this overview indicates areas in which consensus on methodology for physical image-quality measurement has been established. Concepts such as "noise equivalent quanta" (NEQ) and "detective quantum efficiency" (DQE) have been found useful for normalizing physical measurements on an absolute scale and for relating those measurements to the decision performance of a hypothetical "ideal observer" that effectively performs decision tasks from the image data. The connection between ideal observer performance and human performance, as determined by receiver operating characteristic (ROC) analysis, remains to be understood for many clinically relevant tasks.

Biophysical Phenomena↗
PubMed1995

Objective assessment of image quality. II. Fisher information, Fourier crosstalk, and figures of merit for task performance.

Figures of merit for image quality are derived on the basis of the performance of mathematical observers on specific detection and estimation tasks. The tasks include detection of a known signal superimposed on a known background, detection of a known signal on a random background, estimation of Fourier coefficients of the object, and estimation of the integral of the object over a specified region of interest. The chosen observer for the detection tasks is the ideal linear discriminant, which we call the Hotelling observer. The figures of merit are based on the Fisher information matrix relevant to estimation of the Fourier coefficients and the closely related Fourier crosstalk matrix introduced earlier by Barrett and Gifford [Phys. Med. Biol. 39, 451 (1994)]. A finite submatrix of the infinite Fisher information matrix is used to set Cramer-Rao lower bounds on the variances of the estimates of the first N Fourier coefficients. The figures of merit for detection tasks are shown to be closely related to the concepts of noise-equivalent quanta (NEQ) and generalized NEQ, originally derived for linear, shift-invariant imaging systems and stationary noise. Application of these results to the design of imaging systems is discussed.

Computer Simulation↗
PubMed1995

[A meta-theoretical scope model of psychotherapeutic theories. Consequences for human image and therapy in behavior therapy].

Proceeding on the science-theoretical units Handeln, Tun and Verhalten, developed by Groeben 1986 connected with an integration of empirical and hermeneutical investigation, a metatheoretic frame model of psychotherapeutic theories is presented and its relevance for the practice is explained. The model integrates different therapeutic ways with another and lays down an ethic-sequential order of rank for the choice of theories and methods, which orientates itself according to the basic main assumptions (qua assumptions of man-picture) of the different theories. Starting out from the epistemological subject model (Groeben & Scheele, 1977) as another derivation of the model, an embedding of therapeutic action in a therapist-client-relationship is required, which is characterized with mutual structural parallelism. Goal of therapeutic intervention is the re-establishment of Handlungs-capacity of the client, as postulated in the self management approach. Because of its initial behaviouristic tradition especially the behaviour therapy has to struggle with immense image problems concerning its assumptions of man-picture. Up to now a science-theoretical clarification of these problems has only been occurred in dissatisfied approaches. The present work should fill in this desideratum.

Adaptation, Psychological↗
PubMed1994

Quantitative ultrasonic detection of parenchymal structural change in diffuse renal disease.

OBJECTIVE: The authors determined whether quantitative ultrasound could be useful in the evaluation of diffuse renal disease. METHODS: Digitized radiofrequency ultrasound data were acquired from the kidneys of patients with biopsy-proven diffuse renal disease and transplant rejection (37 patients plus 18 normal volunteers). The results of the quantitative analysis were compared with histology results to determine if microscopic renal structure could be correlated with quantitative features such as scatterer size and scatterer spacing. The results also were analyzed using receiver operating characteristic analysis to determine if diffuse disease could be detected reliably using quantitative methods. RESULTS: The three most useful features in the native kidneys were mean scatterer spacing (MSS), sigma's, and average scatterer size (D). Using these features, it was possible to detect diffuse renal disease causing a decrease in renal function with an area under the ROC curve (Az) of 0.93. The feature D corresponded closely to histologically measured average glomerular diameters. For normals, D = 216 microns and glomerular diameter = 211 microns. No histologic correlate was found for scatterer spacing. In transplants, MSS and integrated backscatter were most useful for detecting rejection (Az = 0.87), and D in rejection was similar to the values for normal kidney and normally functioning transplants. CONCLUSIONS: The D value corresponds to glomerular diameter, and glomerular enlargement can be detected readily using quantitative ultrasound. Combinations of two to four quantitative features can detect diffuse renal disease and transplant rejection reliably.

Humans↗
PubMed1994

A double-blind placebo controlled study of a 5% lidocaine/prilocaine cream (EMLA) for topical anesthesia during thermolysis.

BACKGROUND: Electrolysis and thermolysis are commonly used electrosurgical methods for the permanent destruction of unwanted hair. However, patient fear of pain during treatment may interfere with or even prevent desired treatment of hirsutism on sensitive areas such as the upper lip. OBJECTIVE: This study was conducted to assess the efficacy of EMLA (Eutetic Mixture of Local Anesthetics), a 5% lidocaine/prilocaine cream, as a topically applied local anesthetic during thermolysis on the upper lip. METHODS: A double-blind placebo control study was conducted by the University of Texas Medical Branch thermolysis clinic. Thirty women with idiopathic hirsutism of the upper lip were studied. Pain was measured with a 100 mm visual analog scale (VAS). RESULTS: Total paired VAS score differences comparing the placebo VAS scores to the EMLA VAS scores were significant by paired t-test (P = .0001). Adverse reactions were mild and transient. CONCLUSION: EMLA cream may have multiple applications to the practice of dermatologic surgery, including topically achieved local anesthesia during thermolysis and electrolysis.

Adolescent↗
PubMed1994

Medical liability claims and lawsuits filed against the University of Texas System involving adult psychiatric patients.

A survey was conducted to investigate medical liability claims filed against the University of Texas System (the U.T. System), physicians, and/or institutions concerning care of adult psychiatric patients. There were 34 such claims filed between 1978 and 1991 that had closed by December 1991. In many of these cases, medical record documentation was determined to be inadequate. Of the 34 claims filed, only seven were settled on behalf of U.T. personnel or U.T. institutions. Of these seven settlements, the mean monetary amount paid per case on behalf of U.T. System and non-U.T. System parties was $98,678.57. The two categories with the largest number of claims were 1) cases involving suicides, and 2) cases involving adverse reactions to medication. The largest award was $350,000, paid on behalf of U.T. physicians, a private physician, and non-U.T. institutions for alleged negligent failure to diagnose Cushing's disease. Of this amount, only $150,000 was paid on behalf of U.T. physicians. Risk management strategies should be implemented to address areas of liability in psychiatry residency programs.

Adult↗
PubMed1993

SNR and noise measurements for medical imaging: I. A practical approach based on statistical decision theory.

A method of measuring the image quality of medical imaging equipment is considered within the framework of statistical decision theory. In this approach, images are regarded as random vectors and image quality is defined in the context of the image information available for performing a specified detection or discrimination task. The approach provides a means of measuring image quality, as related to the detection of an image detail of interest, without reference to the actual physical mechanisms involved in image formation and without separate measurements of signal transfer characteristics or image noise. The measurement does not, however, consider deterministic errors in the image; they need a separate evaluation for imaging modalities where they are of concern. The detectability of an image detail can be expressed in terms of the ideal observer's signal-to-noise ratio (SNR) at the decision level. Often a good approximation to this SNR can be obtained by employing sub-optimal observers, whose performance correlates well with the performance of human observers as well. In this paper the measurement of SNR is based on implementing algorithmic realizations of specified observers and analysing their responses while actually performing a specified detection task of interest. Three observers are considered: the ideal prewhitening matched filter, the non-prewhitening matched filter, and the DC-suppressing non-prewhitening matched filter. The construction of the ideal observer requires an impractical amount of data and computing, except for the most simple imaging situations. Therefore, the utilization of sub-optimal observers is advised and their performance in detecting a specified signal is discussed. Measurement of noise and SNR has been extended to include temporally varying images and dynamic imaging systems.

Decision Theory↗
PubMed1993

Medical student academic misconduct: implications of recent case law and possible institutional responses.

Recent case law has protected medical students found guilty of academic misconduct from severe sanctions by emphasizing due process and contractural rights. In light of this development, proactive approaches should be considered by medical schools. Faculty or administrators who have legal backgrounds are more likely to avoid breach of contract and violation of due process and should be appointed as hearing officers in cases of alleged academic misconduct. Finally, determination of a student's mental state (as defined in the MPC) by the hearing officer is a fair and rational method of determining what sanctions should be placed on medical students found to have cheated or plagiarized.

Judicial Role↗