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Biomedical subjects

D G Fryback

Publications and source records attributed to D G Fryback.

At least 55 records · Page 3Linked to original sources
PubMed1979

Application of case series review results to the evaluation of individual cases in diagnostic radiology.

Probability theory provides a simple method for physicians to use their "intellectual linkages" to their past clinical experience in making current diagnoses. Only a pencil and paper are required for making a few likelihood calculations. To illustrate this method, evaluation was done of a new diagnostic sign (presence of knee ossification centers) for differentiating rubella from cytomegalovirus infection in young infants. Two practical questions can be answered by use of this method for calculating probabilities: (1) How certain can one be about either diagnosis when centers are present or absent? (2) How can other radiologists apply these results to their individual cases?

Cytomegalovirus Infections↗
PubMed1978

Informal use of decision theory to improve radiological patient management.

Six radiologists reviewed 50 urograms to determine whether arteriography or needle aspiration should be recommended for evaluation of a space-occupying renal lesion. In addition to their usual decision methods, they were encouraged to think about the problem from a decision theory viewpoint. No computations were required. It was found that even informal, non-numerical application of decision theory resulted in improved outcomes; further improvement was noted with explicit use of numerical methods.

Angiography↗
PubMed1978

Effect of screen/film combinations on diagnostic certainty: Hi-Plus/RPL versus Lanex/Ortho G in excretory urography.

A method using radiologists' subjective judgments was developed to compare the quality of the diagnostic image information from two different screen/film combinations (Hi Plus/RPL versus Lanex/Ortho G). A sample of 148 comparison film pairs was obtained in the course of performing 74 urograms using the two film/screen combinations. Each film pair was evaluated by three radiologists, using a blind film-reading format, in regard to:(1) anatomic diagnostic criteria visualization; (2) radiologic diagnostic certainty; (3) presence or absence of quantum mottle; and (4) prediction of which film of a pair was the rare earth screen/film combination. There was a significant difference favoring Hi Plus/RPL in perceived quality of visualization of anatomic criteria. However, the difference was more of statistical rather than practical importance. Diagnostic certainty differed only marginally and slightly favored the Hi Plus/RPL combination. No signficant differences in perception of quantum mottle were attributable to either screen/film combination. Radiologists were able to correctly identify the screen/film combination a significant proportion of the time. Radiation exposure with the Lanex/Ortho G combination was about half that with the Hi Plus/RPL combination. In this study, this would seem to constitute the major factor in film/screen selection.

Adult↗
PubMed1976

Use of excretory urogram information in the solution of the renal cyst/tumor/cortical nodule problem.

A decision analysis was made of the choice of angiography or needle aspiration to solve the cyst/tumor/cortical nodule diagnostic problem. With a test panel of 43 proved cases, the urogram diagnoses and decisions made at the time of actual patient management were compared with those made by a radiologist viewing the test panel as unknowns. The test panel radiologist based his recommendations on his subjective probability estimates of the three diagnoses in each case. Results indicate that the use of subjective probabilities increases the frequency of specific diagnoses and decreases inappropriate choice of angiography or aspiration.

Decision Making↗
PubMed1975

Likelihood ratios as a measure of the diagnostic usefulness of excretory urogram information.

The log likelihood ratio (LLR) method of assessing physicians' diagnostic judgments can be used to measure the diagnostic usefulness of radiologic information (urography in this study). The method requires collection of referring pbysicians' diagnosis prior to and after urography and their certainty in relation to receipt of the radiologic information. Physicians in daily practice are able to provide diagnoses and assign a percentage number to their certainty. The LLR method permits measurement of the diagnostic usefulness of both normal and abnormal urogram results. Retrospective chart review does not provide the same LLR results as those obtained from the prospective study.

Adult↗
PubMedDate not supplied

Limited use of hypertensive excretory urography.

Clinical experience indicates that hypertensive excretory urography is not a satisfactory screening examination to detect patients having hypertension due to renal artery stenosis. Review of the Cooperative Study data indicates the false negative rate for screening was 21.8%. In addition, the prevalence of hypertension caused by renal artery stenosis appears quite low, in the range of 1-3%. Since the objective is to identify patients who will benefit from surgery, clinical sorting strategy should focus on evaluating patients as surgical candidates, not as having the disease. Once that is done, pharmacodynamic renal arteriography is recommended as the first imaging examination to find the renal artery lesion and determine its hemodynamic significance.

False Negative Reactions↗
PubMedDate not supplied

Technology assessment--an American view.

Technology assessment of an imaging method such as magnetic resonance (MR) is a complicated concept that includes aspects of epidemiology, biostatistics, clinical efficacy determination, outcomes assessment, and knowledge of the technical and medical bases of the imaging method under study. To enhance understanding of the interrelations of the different aspects of technology assessment, a hierarchical model is proposed. This extends from the basic imaging physics domain through clinical applications in diagnosis and treatment decisions to patient outcomes and ultimately societal considerations. This overview paper presents the conceptual continuum of the hierarchical model, and then describes the interrelationships among efficacy, cost effectiveness, and outcomes research as components embedded within the context of technology assessment. It also points out how scientific quality of research in MR imaging assessment can be enhanced through improved research design that takes into account basic concepts of the model.

Humans↗
PubMedDate not supplied

Evaluation of a computerized Bayesian model for diagnosis of renal cyst vs. tumor vs. normal variant from urogram information.

The diagnostic problem of cyst/tumor/normal variant raised on an excretory urogram leads to a decision to do needle aspiration or renal arteriography. This decision depends critically upon the probability distribution for the three diagnoses. A computerized Bayesian model of a uroradiologist's diagnostic process in solving the problem was developed. The model was based on subjective probabilities supplied by an experienced uroradiologist. The model was evaluated in terms of its ability to decrease the cost of further diagnosis regarding aspiration versus arteriography. The model's output was compared with decisions made by unaided radiologists viewing the same panel of 50 urogram test cases. Results indicate that the model does not improve upon the decisions made by a radiologist highly experienced with this diagnostic problem. However, the decisions made by unaided, less experienced radiologists result in greater cost than those of the model.

Angiography↗
PubMedDate not supplied

Uncertainty/information as measure of various urographic parameters: an information theory model of diagnosis of renal masses.

A new decision model for differentiating renal masses by urographic criteria has been developed and tested to demonstrate the use of uncertainty/information as a measure. The conditional probabilities used in this model are the relative frequency of occurrence of 15 specific uroradiographic signs in the presence of cyst, tumor, and benign cortical nodule. The decision model was applied to data obtained at the time of initial interpretation of 80 cases of renal mass discovered on urography. The probability of diagnosis was calculated by computer and compared to the radiologist's subjective probability estimate made prospectively at the time of initial interpretation. Information theory was applied to optimize the sequence in which signs were evaluated. The signs likely to maximally reduce the uncertainty of a diagnosis were evaluated first. The utility of this model and the comparative significance of various urographic signs used diagnose renal cysts, tumors, and benign cortical nodules were assessed. This model of renal mass evaluation at urography demonstrates principles of information theory that can be applied to more difficult and complex diagnostic and management problems.

Decision Making↗
PubMedDate not supplied

A time-tradeoff method for cost-effectiveness models applied to radiology.

PURPOSE: The wait tradeoff (WTO) is a simple time-tradeoff method designed for temporary health states that uses a realistic and intuitive interface for the patient/subject. This method was tested by assessing patients' preferences for magnetic resonance angiography (MRA) versus x-ray angiography (XRA). MATERIALS AND METHODS: The WTO was tested by telephone interview in 38 patients with atherosclerotic peripheral vascular disease, all having previously undergone both MRA and XRA. At indifference point, patients were ambivalent about having MRA or XRA and immediate treatment, versus having a waiting period for test results and treatment after a hypothetical "ideal test" that entailed no pain or risk. RESULTS: The patients were willing to wait a mean of 42.1 days after the ideal test for results and treatment, as opposed to XRA. They were willing to wait only 16.1 days as opposed to MRA. This difference in waiting times was significant (p = 0.0001) and indicates a clear preference for MRA, in agreement with known literature. CONCLUSION: The WTO method assesses preferences for these radiologic tests in an intuitive fashion that does not invoke artificial or irrelevant health states. This approach may also prove useful for other testing situations or short-term treatments being evaluated for cost-effectiveness.

Adult↗
PubMedDate not supplied

A decision theoretic methodology for severity index development.

Severity indices are a key element in evaluation of health programs. But the methodologies used in development of such indices are rarely clearly defined. Moreover, there have been no tests of transportability of the index development methodologies that do exist, so there is no guarantee that panels of physicians convened by different facilitators would produce indices with similar performance characteristics. This paper describes a replicable index development strategy, a heart disease severity index developed by using that methodology, and a test of that methodology's transportability.

Coronary Disease↗
PubMedDate not supplied

The frontier.

Explore the source record for details and available documents.

Bayes Theorem↗
PubMedDate not supplied

The efficacy of diagnostic imaging.

The authors discuss the assessment of the contribution of diagnostic imaging to the patient management process. A hierarchical model of efficacy is presented as an organizing structure for appraisal of the literature on efficacy of imaging. Demonstration of efficacy at each lower level in this hierarchy is logically necessary, but not sufficient, to assure efficacy at higher levels. Level 1 concerns technical quality of the images; Level 2 addresses diagnostic accuracy, sensitivity, and specificity associated with interpretation of the images. Next, Level 3 focuses on whether the information produces change in the referring physician's diagnostic thinking. Such a change is a logical prerequisite for Level 4 efficacy, which concerns effect on the patient management plan. Level 5 efficacy studies measure (or compute) effect of the information on patient outcomes. Finally, at Level 6, analyses examine societal costs and benefits of a diagnostic imaging technology. The pioneering contributions of Dr. Lee B. Lusted in the study of diagnostic imaging efficacy are highlighted.

Clinical Protocols↗