bluuebunny/crossref_metadata_2025 huggingface dataset:
Public Preferences for Prevention versus Cure: What if an Ounce of Prevention is Worth Only an Ounce of Cure?
Authors: Ubel Peter A. , Spranca Mark D. , Dekay Michael L. , Hershey John C. , Asch David A.
Published: March 2007

Background. The belief that small preventive efforts bring large benefits may explain why many people say they value prevention above all other types of health care. However, it often takes a great deal of preventive medicine to prevent a bad outcome. This study explores whether people value prevention or cure more when each brings the same magnitude of benefit and examines whether preferences for prevention or cure vary according to the severity of the disability of the patients who can receive the preventive or curative intervention. Methods. 289 prospective jurors were presented with a policy dilemma involving how best to allocate funds to benefit people with varying levels of disability. Each project was said to influence the functional ability of 100 nursing home residents, either by improving their level of function or by preventing their level of function from declining. Results. When given a choice between preventive and curative interventions, more subjects preferred the preventive intervention (37% vs 21%, p = 0.002). However, when the strength of people's preferences was taken into account, the preference for preventive interventions was not statistically significant (p = 0.135). With both preventive and curative interventions, the subjects preferred helping patients with more severe disabilities (p < 0.005 for both comparisons). This preference for helping more severely disabled patients did not differ for prevention and cure (p = 0.663). Conclusion. When the magnitude of benefit was held constant, the subjects slightly preferred prevention over cure. In addition, they preferred directing limited resources toward those with greater disabilities, regardless of whether those resources were targeted toward prevention or cure. These findings suggest that previously stated preferences for prevention over cure may result from a belief that small efforts at prevention will be repaid by large reductions in the later need for cure.
Decision and Cost-Utility Analyses of Surgical versus Transcatheter Closure of Patent Ductus Arteriosus
Authors: Gray Darryl T. , Weinstein Milton C.
Published: March 2007

Decision and cost-utility analyses considered the tradeoffs of treating patent ductus arteriosus (PDA) using conventional surgery versus transcatheter implantation of the Rashkind occluder. Physicians and informed lay parents assigned utility scores to procedure success/complications combinations seen in prognostically similar pediatric patients with isolated PDA treated from 1982 to 1987. Utility scores multiplied by outcome frequencies from a comparative study generated expected utility values for the two approaches. Cost-utility analyses combined these results with simulated provider cost estimates from 1989. On a 0-100 scale (worst to best observed outcome), the median expected utility for surgery was 99.96, versus 98.88 for the occluder. Results of most sensitivity analyses also slightly favored surgery. Expected utility differences based on 1987 data were minimal. With a mean overall simulated cost of $8,838 vs $12,466 for the occluder, surgery was favored in most cost-utility analyses. Use of the inherently less invasive but less successful, more risky, and more costly occluder approach conferred no apparent net advantage in this study. Analyses of comparable current data would be informative.
Testing for the BRCA1 and BRCA2 Breast-Ovarian Cancer Susceptibility Genes
Authors: Tengs Tammy O. , Winer Eric P. , Paddock Susan , Aguilar-Chavez Omar , Berry Donald A.
Published: March 2007

Objective. The authors developed a Markov decision model to evaluate the health implications of testing for mutations in the BRCA1 and BRCA2 breast-ovarian cancer susceptibility genes. Prophylactic measures considered included various combinations of immediate and delayed bilateral mastectomy and oophorectomy or taking no action. Methods. The model incorporated the likelihood of developing breast and/or ovarian cancer, survival, and quality of life. Parameter values were taken from public data bases, the published literature, and a survey of cancer experts. Outcomes considered were additional life expectancy and quality-adjusted life years (QALYs). Results are reported for 30-year-old cancer-free women at various levels of hereditary risk. Results and conclusions. The vast majority of women will not benefit from testing because their pre-test risks are low and surgical prophylaxis is undesirable. However, women who have family histories of early breast and/or ovarian cancer may gain up to 2 QALYs by allowing genetic testing to inform their decisions. Key words: BRCA1; BRCA2; ge netic testing; breast cancer; ovarian cancer; decision analysis. (Med Decis Making 1998;18:365-375)
Clinical Diagnosis and the Order of Information
Authors: Bergus George R. , Chapman Gretchen B. , Levy Barcey T. , Ely John W. , Oppliger Robert A.
Published: March 2007

Background. Information order can influence judgment. However, it remains unclear whether the order of clinical data affects physicians' interpretations of these data when they are engaged in familiar diagnostic tasks. Methods. Of 400 randomly selected family physicians who were given a questionnaire involving a brief written scenario about a young woman with acute dysuria, 315 (79%) returned usable responses. The physicians had been randomized into two groups, and both groups had received the same clinical information but in different orders. After learning the patient's chief com plaint, physicians received either the patient's history and physical examination results followed by the laboratory data (the H&P-first group) or the laboratory data followed by the history and physical examination results (the H&P-last group). The results of the history and physical examination were supportive of the diagnosis of UTI, while the laboratory data were not. All physicians judged the probability of a urinary tract infection (UTI) after each piece of information. Results. The two groups had similar mean estimates of the probability of a UTI after learning the chief complaint (67.4% vs 67.8%, p = 0.85). At the end of the scenario, the H&P-first group judged UTI to be less likely than did the H&P-last group (50.9% vs 59.1 %, p = 0.03) despite having identical information. Comparison of the mean likelihood ratios attributed to the clinical information showed that the H&P-first group gave less weight to the history and phys ical than did the H&P-last group (p = 0.04). Conclusions. The order in which clinical information was presented influenced physicians' estimates of the probability of dis ease. The clinical history and physical examination were given more weight by phy sicians who received this information last. Key words: diagnosis; urinary tract infec tions ; judgment; primary care; clinical decision making. (Med Decis Making 1998;18: 412-417)
Tests of Preferential Independence in the QALY Model
Authors: Treadwell Jonathan R.
Published: March 2007

The author presents evidence for the descriptive adequacy of the quality-adjusted life years (QALY) model as applied to health profiles. One important assumption of the model is preferential independence: if two profiles have the same health state during year X, then preference between them does not switch if the level of health changes during year X. In experiment 1, 30-year health profiles were used to perform 27 em pirical tests of independence with 98 subjects. Independence was reliably satisfied in all 27 tests. In experiment 2, 15 additional tests were conducted. These tests had been specifically designed to be more sensitive to independence violations, but indepen dence was still mostly satisfied. In both experiments, the conclusions about indepen dence hold regardless of what discount rate is used. These results act as a "lower bound" on the validity of the QALY model for health profiles. Key words: quality-ad justed life years; QALY model; health profiles; preferential independence. (Med Decis Making 1998;18:418-428)
Cost—Effectiveness of Regulations against Using a Cellular Telephone while Driving
Authors: Redelmeier Donald A. , Weinstein Milton C.
Published: March 2007

Purpose: To evaluate the cost—effectiveness of regulations that prohibit using a cellular telephone while driving a motor vehicle. Design: Decision analysis of risks and benefits related to cellular telephones and driving. Setting: United States population in 1997. Measures: Health benefits measured as the quality-adjusted life years potentially saved. Financial benefits measured as health care and other services potentially averted. Costs of regulation measured as the lost productivity derived from willingness to pay for cellular telephone calls. Results: Under base-case conditions, cellular tele phone calls in the United States each day accounted for about 984 reported collisions, 1,729 total collisions, 2 deaths, 317 persons with injuries, 99 lost years of life expec tancy, 161 lost quality-adjusted life years, $1 million in health care costs, and $4 million in property damage and other costs. This reflected a total of about 35 million telephone calls while driving, 70 million calling minutes, and $33 million in total value to society. The estimated cost—effectiveness ratio for a regulation restricting cellular telephone usage while driving was $300,000 per quality-adjusted life year saved, but ranged from $50,000 to $700,000 under alternative assumptions and interpretations of data. Reg ulations applied to teenage males could be cost-saving to society if the value of a call fell below 37¢ per minute. Conclusions: Regulations restricting cellular telephone us age while driving are less cost-effective for society than other safety measures. Nev ertheless, regulations may be justifiable because the benefits and harms do not always involve the individual who has the cellular telephone. Increasing the price of a call (or adding a supplementary tax) might decrease the number of discretionary calls, be cost- saving for society, and be life-saving for individuals. Key words: cost—effectiveness; motor vehicle accidents; regulation; cellular telephones; driving. (Med Decis Making 1999;19:1-8)
The Stability of Preferences for Life-sustaining Care among Persons with AIDS in the Boston Health Study
Authors: Weissman Joel S. , Haas Jennifer S. , Fowler Floyd J. , Gatsonis Constantine , Massagli Michael P. , Seage George R. , Cleary Paul
Published: March 2007

Background. Clinicians recognize the importance of eliciting patient preferences for life-sustaining care, yet little is known about the stability of those preferences for pa tients with serious disease. Objectives. To examine the stability of preferences for life- sustaining care among persons with AIDS and to assess factors associated with changes in preferences. Design. Two patient surveys and medical record reviews, administered four months apart in 1990-1991. Setting. Three health care settings in Boston. Patients. 252 of 505 eligible persons with AIDS who participated in both base line and follow-up surveys. Main outcome measures. A single question assessing de sire for cardiac resuscitation and a scale of preferences for life-extending treatment conditional on hypothetical health states. Results. Approximately one-fourth of the re spondents changed their minds about life-sustaining care during a four-month period. Of patients who initially desired cardiac resuscitation, 23% decided to forego it four months later, and of those who initially said they would decline care, 34% later said they would accept it. Of those who initially desired any of the life-extending treatments, 25% decided to forego them four months later, and of those who initially said they would decline life-extending care, 24% later said they would accept some treatment. Patients reporting changes in physical function, pain, or suicide ideation were more likely to modify their desires to be resuscitated (all p ≤ 0.05). Patients lacking an advance directive, not completing high school, or becoming more severely ill were more likely to change their preferences on the Life Extension scale (p ≤ 0.05). Patients who discussed their preferences with at least one physician were just as likely as others to change desires for cardiac resuscitation. Age, gender, race, emotional health, clinical severity, social support, and site of care were not significant correlates of change for either measure. Conclusions. Health care providers should periodically reassess preferences for life-sustaining care, particularly for patients with progressive disease, given the instability in patient preferences. However, predictors of instability may vary with how preferences are measured. In particular, changes in health status may be related to instability of preferences for certain types of treatments. Key words: life-sustaining care; patient preferences; AIDS. (Med Decis Making 1999;19:16-26)
Multiattribute Utility Scores for Predicting Family Physicians' Decisions Regarding Sinusitis
Authors: de Bock Geertruida H. , Reijneveld Sijmen A. , van Houwelingen Johannes C. , Knottnerus J. André , Kievit Job
Published: March 2007

To examine whether multiattribute utility (MAU) scores can be used to predict family physicians' decisions regarding patients suspected to have sinusitis and rhinitis, 100 randomly selected family physicians from the Leiden area (The Netherlands) were asked to rank a set of six attributes regarding their importance, yielding attribute weights. Next, the physicians were asked to rate the degrees to which five decision alternatives optimized each attribute, yielding utilities, regarding three case vignettes about a patient suspected to have acute maxillary sinusitis and rhinitis, with a brief clinical history. By combining attribute weights and utilities, a MAU score was calcu lated for each decision alternative regarding each case vignette. Finally, for each case vignette the physicians' treatment preferences were assessed by means of an open ended question. For the clear-cut sinusitis case, management strategies and highest MAU scores were concordant for 80% of the physicians. Regarding the dubious si nusitis and rhinitis case, concordance was 50%. The latter was associated with small differences in values between the highest MAU scores. Because agreement among the physicians regarding the management strategies and weight ranks was high and there was little variation in the highest MAU scores, the kappas between the reported management strategies and weight ranks were poor (0.24 and lower). It is concluded that MAU scores may be used to predict family physicians' decisions regarding the management of patients suspected of having sinusitis where there are significant dif ferences in values between the highest MAU scores. Key words: multiattribute utilities; sinusitis; rhinitis; family physician; decision making. (Med Decis Making 1999;19:58- 65)
Three-way ROCs
Authors: Mossman Douglas
Published: March 2007

Receiver operating characteristic (ROC) analysis traditionally has dealt with dichoto mous diagnostic tasks (e.g., determining whether a disorder is present or absent). Often, however, medical problems involve distinguishing among more than two diag nostic alternatives. This article extends ROC concepts to diagnostic enterprises with three possible outcomes. For a trichotomous decision task, one can plot a ROC surface on three-dimensional coordinates; the volume under the ROC surface (VUS) equals the probability that test values will allow a decision maker to correctly sort a trio of items containing a randomly-selected member from each of three populations. Thus, the VUS summarizes global diagnostic accuracy for trichotomous tests, just as the area under a ROC curve does for a two-alternative diagnostic task. Information gain at points on the surface can be calculated just as is done for two-dimensional ROC curves, and investigators can thus compare three-way ROCs by comparing maximum information gain on each ROC surface. Key words: receiver operating characteristic, ROC, three-way ROC, three-alternative decision task, resampling, bootstrap, infor mation. (Med Decis Making 1999;19:78-89)
Health-related Quality of Life in Economic Evaluations for Osteoporosis
Authors: Gabriel Sherine E. , Kneeland Terry S. , Melton L. Joseph , Moncur Megan M. , Ettinger Bruce , Tosteson Anna N.A.
Published: March 2007

Objective. To determine whether the source of preference scores has an impact on the cost-effectiveness of osteoporosis interventions. Methods. Three groups of sub jects aged ≥50 years—199 women without fractures and 183 women with osteopo rotic fractures—were studied at two major medical centers. Medical history and co morbidity data were obtained from review of medical records. Health status was measured using the Medical Outcomes Study SF-36. Two preference-classification systems (i.e., quality of well-being scores estimated from SF-36 subscales and the Health Utilities Index) were also used. Preferences for current health and for hypo thetical health states were assessed using a time tradeoff and implemented with a computer-based utility instrument (U-Titer). Wilcoxon's rank-sum and signed-rank tests were used to compare preferences for current health among women with osteoporotic fractures with 1) directly assessed preferences for osteoporosis health states deline ated by outcome descriptions and 2) preference scores obtained from the preference- classification systems. The potential impact of the source of the preference scores was estimated using a Markov state-transition model. Results. The preference scores for hypothetical osteoporosis health states of the non-fracture subjects were approximately 50% lower than those of the women who had actually experienced the health state. Differences of this magnitude would change the estimated cost-effectiveness of a 15- year intervention (which for approximately $280 per year prevents hip fracture about as well as hormone-replacement therapy) from $25,000 per QALY gained when non- fracture subjects' preferences were used to $94,000 per QALY gained when fracture subjects' preferences were used. Preferences estimated using the Health Utilities Index and those directly measured in fracture subjects using the time tradeoff did not differ significantly. Conclusions. The Health Utilities Index preference-classification system may provide an efficient and inexpensive alternative to direct utility assessment in this patient group. However, there are important differences in the valuation of health states by women who have experienced osteoporotic fractures compared with women who have not. Cost-utility analyses based solely on fracture patients' preferences for os teoporotic health states may undervalue prevention. Key words: osteoporosis; quality of life; utility assessment; patients' preferences. (Med Decis Making 1999;19:141- 148)
Distributed Decision Support Using a Web-based Interface
Authors: Sanders Gillian D. , Hagerty C. Greg , Sonnenberg Frank A. , Hlatky Mark A. , Owens Douglas K.
Published: March 2007

Although decision models can provide a formal foundation for guideline development and clinical decision support, their widespread use is often limited by the lack of plat form-independent software that geographically dispersed users can access and use easily without extensive training. To address these limitations the authors developed a World Wide Web-based interface for previously developed decision models. They describe the use and functionality of the interface using a decision model that evaluates the cost-effectiveness of strategies for preventing sudden cardiac death. The system allows an analyst to use a web browser to interact with the decision model and to change the values of input variables within pre-specified ranges, to specify sensitivity or threshold analyses, to evaluate the decision model, and to view the results gener ated dynamically. The web site also provides linkages to an explanation of the model, and evidence tables for input variables. The system demonstrates a method for pro viding distributed decision support to remote users such as guideline developers, de cision analysts, and potentially practicing physicians. The web interface provides plat form-independent and almost universal access to a decision model. This approach can make distributed decision support both practical and economical, and has the potential to increase the usefulness of decision models by enabling a broader audience to in corporate systematic analyses into both policy and clinical decisions. Key words: de cision-support techniques; practice guidelines; user-computer interface; decision anal ysis. (Med Decis Making 1999;19:157-166)
Relative Entropy as a Measure of Diagnostic Information
Authors: Benish William A.
Published: March 2007

Relative entropy is a concept within information theory that provides a measure of the distance between two probability distributions. The author proposes that the amount of information gained by performing a diagnostic test can be quantified by calculating the relative entropy between the posttest and pretest probability distributions. This statistic, in essence, quantifies the degree to which the results of a diagnostic test are likely to reduce our surprise upon ultimately learning a patient's diagnosis. A previously proposed measure of diagnostic information that is also based on information theory (pretest entropy minus posttest entropy) has been criticized as failing, in some cases, to agree with our intuitive concept of diagnostic information. The proposed formula passes the tests used to challenge this previous measure. Key words: diagnostic test; entropy; information theory; relative entropy; uncertainty. (Med Decis Making 1999;19: 202-206)
Use of Focus Groups to Identify Concerns about Dialysis
Authors: Bass Eric B. , Jenckes Mollie W. , Fink Nancy E. , Cagney Kate A. , Wu Albert W. , Sadler John H. , Meyer Klemens B. , Levey Andrews. , Powe Neil R.
Published: March 2007

Background. Patients with end-stage renal disease (ESRD) may have quality-of-life (QOL) concerns that are not fully appreciated by their providers. The authors con ducted focus groups with dialysis patients and dialysis professionals to determine whether this qualitative method would reveal differences between patients' and provid ers' views about: 1) domains of QOL that are affected by ESRD and dialysis; and 2) aspects of dialysis that affect QOL. Methods . Separate focus group discussions were held with: 8 adult hemodialysis patients (mean age 50 years; 3 women; mean duration of dialysis 8.5 years), 5 adult peritoneal dialysis patients (mean age 54 years; 3 women; mean duration of dialysis 4.6 years), 8 nephrologists (mean of 12 years of dialysis practice), and 9 other health professionals involved in dialysis care (3 nurses, 2 dieti tians, 2 social workers, and 2 technicians; mean of 10 years experience in dialysis care). Discussions were audiotaped, transcribed verbatim, and reviewed independently by three investigators to identify and categorize distinct thoughts. Results. 1,271 dis tinct thoughts were identified and grouped into 20 related categories, which included ten QOL domains and ten aspects of dialysis that affect QOL. Compared with the professionals, the patients identified one additional relevant QOL domain (10 vs 9), and one additional aspect of dialysis that affects QOL (10 vs 9), and expressed more thoughts per domain (p < 0.05), although the contents of their comments were fre quently similar. Among QOL domains, the numbers of related thoughts identified by patients and professionals, respectively, were: freedom/control (60, 89); social rela tionships (36, 11); anxiety (37, 4); role function (24, 10); energy (12, 10); body image (16, 4); sex (11, 21); mental attitude (21, 0); sleep (15, 1), and cognitive function (13, 7). Among aspects of dialysis that affect QOL, the numbers of thoughts identified by patients and professionals were: general dialysis issues (159, 105); relationships with staff (62, 110); patient education (63, 68); diet (44, 40); scheduling (57, 3); vascular or peritoneal access issues (31, 17), adaptation to dialysis (16, 14); dialysis dose (18, 8); symptoms (25, 0), and self-care (5, 24). Conclusions. Although health professionals have a good understanding of patient concerns about the effects of ESRD and dialysis, the focus group discussions revealed a breadth and depth of QOL concerns that they may not fully appreciate. Key words: focus groups; dialysis treatment; quality of life; patient perspective. (Med Decis Making 1999; 19:287-295)
Framing Effects in Choices between Multioutcome Life-expectancy Lotteries
Authors: Bernstein Lionel M. , Chapman Gretchen B. , Elstein Arthur S.
Published: March 2007

Aim. To explore framing or editing effects and a method to debias framing in a clinical context. Method. Clinical scenarios using multioutcome life-expectancy lotteries of equal value required choices between two supplementary drugs that either prolonged or shortened life from the 20-year beneficial effect of a baseline drug. The effects of these supplementary drugs were presented in two conditions, using a between-sub jects design. In segregated editing ( n = 116) the effects were presented separately from the effects of the baseline drug. In integrated editing ( n = 100), effects of supple mentary and baseline drugs were combined in the lottery presentation. Each subject responded to 30 problems. To explore one method of debiasing, another 100 subjects made choices after viewing both segregated and integrated editings of 20 problems (dual framing). Results. Statistically significant preference reversals between segre gated and integrated editing of pure lotteries occurred only when one framing placed outcomes in the gain domain, and the other framing placed them in the loss domain. When both editings resulted in gain-domain outcomes only, there was no framing ef fect. There was a related relationship of framing-effect shifts from losses to gains in mixed-lottery-choice problems. Responses to the dual framing condition did not con sistently coincide with responses to either single framing. In some situations, dual framing eliminated or lessened framing effects. Conclusion. The results support two components of prospect theory, coding outcomes as gains or losses from a reference point, and an s-shaped utility function (concave in gain, convex in loss domains). Pre senting both alternative editings of a complex situation prior to choice more fully in forms the decision maker and may help to reduce framing effects. Given the extent to which preferences shift in response to alternative presentations, it is unclear which choice represents the subject's "true preferences." Key words: life expectancy; mul tioutcome lotteries; framing effects; preference reversal; segregated and integrated editing; prospect theory; utility functions. (Med Decis Making 1999; 19:324-338)
Power and Sample Size in Cost- Effectiveness Analysis
Authors: Laska Eugene M. , Meisner Morris , Siegel Carole
Published: March 2007

For resource allocation under a constrained budget, optimal decision rules for mutually exclusive programs require that the treatment with the highest incremental cost-effec tiveness ratio (ICER) below a willingness-to-pay (WTP) criterion be funded. This is equivalent to determining the treatment with the smallest net health cost. The designer of a cost-effectiveness study needs to select a sample size so that the power to reject the null hypothesis, the equality of the net health costs of two treatments, is high. A recently published formula derived under normal distribution theory overstates sample- size requirements. Using net health costs, the authors present simple methods for power analysis based on conventional normal and on nonparametric statistical theory. Key words: cost-effectiveness analysis; power; sample size; cost-effectiveness ratios; net health costs; net health benefits; statistical analysis. (Med Decis Making 1999;19: 339-343)
How Patients' Preferences for Risk Information Influence Treatment Choice in a Case of High Risk and High Therapeutic Uncertainty
Authors: Mazur Dennis J. , Hickam David H. , Mazur Marcus D.
Published: March 2007

To assess how patients' preferences for non-numerical risk information are related to their tendency to choose early surgical treatment for asymptomatic gland-confined prostate cancer (a choice with high risk and high therapeutic uncertainty), the authors conducted a cross-sectional study of 228 patients receiving continuing care in a gen eral medicine clinic. After being provided with three data disclosures related to the treatment decision, subjects were given a choice between surgery-now and watchful waiting. Data about surgical complications were presented in numerical format. The subjects were also asked whether they preferred communication with their physician about the chance (probability) of adverse outcomes—related to management strate gies—in terms of words (such as possible or probable) or numbers (such as percent ages). Of the 226 patients who chose either surgery-now or watchful waiting, 71.2% preferred risk information in terms of words only or numbers only: 44% words only, and 56% numbers only. Younger patients (OR = 1.06 per year; Cl = 1.02-1.10, p = 0.0008) and those wanting risk communication in terms of words only (OR = 2.41; Cl = 1.24-4.70, p = 0.01) tended to prefer surgery-now over watchful waiting as the management strategy for asymptomatic gland-confined prostate carcinoma. The au thors conclude that there is a significant association between patients' preferences for risk communication with their physicians in terms of words only and a tendency to prefer early surgical intervention for prostate cancer when surgical risk data are pro vided numerically. Key words: informed consent; medical decision making; patient- physician communication; patient preference; prostate carcinoma; nsk. (Med Decis Making 1999;19:394-398)
Evaluation of a Decision-support System for Preoperative Staging of Prostate Cancer
Authors: Phei Lang ChangHANG  , Li  , TA Min Wang  , Shih Tsung Huang  , Ming Li Hsieh  , Ke Hung Tsui
Published: March 2007

The usefulness and effectiveness of a decision-support system for preoperative stag ing of prostate cancers (PCES) were evaluated. The study population consisted of 43 consecutive patients with the preoperative diagnosis of prostate cancer who underwent surgical operation. Results obtained using the PCES were compared with staging by four urology attending physicians and five urology residents. The effect of PCES con sultation on the physicians' staging of prostate cancer was also evaluated. To confirm the usefulness of the clinical findings of prostate-specific antigen, prostate-specific an tigen density, prostate volume, and abnormal Gleason score in the PCES, their re ceiver operating characteristic (ROC) curves for diagnosis of advanced prostate cancer were plotted. The values of the areas under the curves were 0.772, 0.800, 0.531, and 0.752. The stage of prostate cancer was correctly determined by the PCES for 38 of the 43 patients, yielding 88.4% preoperative diagnostic accuracy. The PCES was sig nificantly more accurate than two of the attending physicians and all residents. PCES consultation improved the residents' staging accuracy to approximately that of the at tending physicians. The effect of PCES consultation on the residents' staging was significantly (p < 0.001) greater than the effect on the physicians' staging. The PCES may be useful in the preoperative staging of prostate cancers, especially during resi dency. The system's accuracy in determining the stage of advanced prostate cancer may make it possible to avoid unneccesary surgical operations. Key words: decision- support system; expert system; prostate cancer. (Med Decis Making 1999;19:419- 427)
The Discrepancy between Risky and Riskless Utilities
Authors: Stalmeier Peep F.M. , Bezembinder Thom G.G.
Published: March 2007

Utilities differ according to whether they are derived from risky (gamble) and riskless (visual analog scale, time-tradeoff) assessment methods. The discrepancies are usu ally explained by assuming that the utilities elicited by risky methods incorporate atti tudes towards risk, whereas riskless utilities do not. In (cumulative) prospect theory, risk attitude is conceived as consisting of two components: a decision-weight function (attentiveness to changes in, or sensitivity towards, chance) and a utility function (sen sitivity towards outcomes). The authors' data suggest that a framing effect is a hitherto unrecognized and important factor in causing discrepancies between risky and riskless utilities. They collected risky evaluations with the gamble method, and riskless evalu ations with difference measurement. Risky utilities were derived using expected-utility theory and prospect theory. With the latter approach, sensitivity towards outcomes and sensitivity towards chance are modeled separately. When the hypothesis that risky utilities from prospect theory coincide with riskless utilities was tested, it was rejected (n = 8, F(1,7) = 132, p = 0.000), suggesting that a correction for sensitivity towards chance is not sufficient to resolve the difference between risky and riskless utilities. Next, it was assumed that different gain/loss frames are induced by risky and riskless elicitation methods. Indeed, identical utility functions were obtained when the gain/loss frames were made identical across methods (n = 7), suggesting that framing was operative. The results suggest that risky and riskless utilities are identical after correc tions for sensitivity towards chance and framing. Key words: utility assessment; de cision making; risk attitude; framing; risky and riskless utilities. (Med Decis Making 1999;19:435-447)
Design and Implementation of a VLSI Tactile Sensing Computer
Authors: Raibert Marc H. , Tanner John E.
Published: March 2007

A new type of tactile sensor is presented that was designed to give a robot manipulation system information about contact between its hand and objects in the environment. We describe a device that is at once a special-purpose parallel computer and a high-resolution tactile array sen sor. The passive substrates of earlier tactile sensors have been replaced with a custom-designed very large scale in tegration (VLSI) device that performs transduction, tactile image processing, and communication. Forces are trans duced using a conductive plastic technique in conjunction with metal electrodes on the surface of an integrated cir cuit. An array of processors implemented within the inte grated circuit perform parallel two-dimensional convolu tions between programmable filtering masks and a binary tactile image. Data are then read from the array serially, so they can be transmitted to a control computer. A 6 x 3 array sensor with 1 mm2 tactile cells has been designed and tested. It is fully functional.

In preparation for constructing large sensor arrays with hundreds of elements, the possibility of constructing defect tolerant tactile cells was explored. Analyses based on the Poisson model indicate that working arrays with 1,000 functional cells are possible if computing elements are rep licated within each tactile cell. Experiments on a 3 x 3 array sensor with redundant pairs of computing elements suggest that large tactile sensing arrays are within reach.
Dynamic Sensing for Robots: An Analysis and Implementation
Authors: Beni G. , Hackwood S. , Hornak L.A. , Jackel J.L.
Published: March 2007

Dynamic sensing is discussed in detail. We have initiated a systematics of robotic sensor design by formulating the general problems and addressing the specific question of how to arrange the sensing elements. We have derived a general relationship between the number and speed of the sensing elements as a function of their response and processing times. We have thus constructed afiber-optic sensor for the fingers of a Unimation Puma 500 robot. The sensor consists of three linear arrays ( each with 12 sensing elements) , attached to the edges of the robot fingers in a U shape. The elements are composed of parallel, equally spaced, collimated light beams that pass from finger to finger. Each linear array can be scanned dynamically to provide a 12 X 18 = 256-pixel cov erage of a 2 X 3-cm area.
Mechanics of Locomotion
Authors: McMahon T.A.
Published: March 2007

Energetic and mechanical principles of walking and running are reviewed, using information available from force-plate studies. A mathematical model of walking is described that conserves the sum of the kinetic and gravitational potential energies of the body. In running, energy is stored transiently in the elastic deformations of stretched muscles and tendons. Theory and experiments are described using these principles and others to find the range of stiffness values for a running track that both lowers the potential for injuries and increases running speed.
The Gaits of Bipedal and Quadrupedal Animals
Authors: Alexander R. McN.
Published: March 2007

The gaits of reptiles, birds, and mammals are reviewed. It is shown that mammals of different sizes tend to move in dy namically similar fashion whenever their Froude numbers u2/gh are equal: here u is speed, g is the acceleration of free fall, and h is the height of the hip joint from the ground. The gaits of turtles and people are examined in detail. The gaits of turtles appear to reduce unwanted displacements ( pitch, roll, etc.) to the minimum possible for animals with such slow muscles. The patterns of force exerted in human walking and running minimize the work required of the muscles at each speed. Much of the energy that would otherwise be neededfor running, by people and other large mammals, is saved by tendon elasticity.
Stability Analysis and Input Design of a Two-Link Planar Biped
Authors: Hemami Hooshang , Chen Ben-Ren
Published: March 2007

A two-link planar biped system under the influence of holo nomic ( connection) constraints with constraints not in effect and in effect is investigated in this paper. The use of quadratic Lyapunov functions to construct the feedback strategies for maintaining stability in the vicinity of an operating point is presented. The role of the different inputs in opposing gravity, maintaining connection constraints, and moving the system is delineated. Finally, the effectiveness of this methodology and one of its applications are demonstrated via some digital computer simulations.
Characteristics of Leg Movements and Patterns of Coordination in Locusts Walking on Rough Terrain
Authors: Pearson K.G. , Franklin R.
Published: March 2007

A cinematographic analysis was made of locusts walking on a variety of terrains to determine the tactics used by single legs to find a site for support and the patterns of leg coordina tion when walking on rough terrain. Three tactics were used by individual legs for finding a support site: ( 1) rhythmic searching movements initiated when the leg failed to contact the substrate at the end of the swing phase, ( 2) a tactile reflex to lift the leg above an object contacted during swing phase, and ( 3) local searching movements once the leg had contacted a potential supporting surface. Animals did not adopt rigid gaits when walking on rough terrains. The wide range of stepping patterns was due mainly to variation in the timing of stepping in opposite legs of the same segment. However, there was a tendency for the stepping movements of opposite legs to be either 180° out of phase or exactly in phase. In- phase stepping of the middle legs was observed frequently when animals walked over a ditch or up onto an elevated ob ject. Once the forelegs had found support on either the far side of the ditch or on the elevated object, both middle legs stepped simultaneously and were then used together to move the animal over the ditch or up onto the object.
The UTAH/M.I.T. Dextrous Hand: Work in Progress
Authors: Jacobsen S.C. , Wood J.E. , Knutti D.F. , Biggers K.B.
Published: March 2007

The Center for Biomedical Design at the University of Utah and the Artificial Intelligence Laboratory at the Massachu setts Institute of Technology are developing a tendon-oper ated multiple-degree-of-freedom dextrous hand (DH) with multichannel touch-sensing capability. Our goal is the design and fabrication of a high-performance yet well-behaved sys tem that is fast and stable and that includes considerable operational flexibility as a research tool. The paper reviews progress to date on project subtasks and discusses design issues important to hardware and control systems develop ment in terms of (1) structures that contain tendons, actua tors, joints, and sensors; (2) both pneumatic and electric tendon actuation systems; (3) optically based sensors that detect touch; (4) subcontrol systems that provide internal management of the DH; and (5) preliminary higher control systems that supervise general operation of the hand during execution of tasks and that provide integration of vision and tactile information.
On the Complexity of Motion Planning for Multiple Independent Objects; PSPACE- Hardness of the "Warehouseman's Problem"
Authors: Hopcroft J.E. , Schwartz J.T. , Sharir M.
Published: March 2007

Coordinated motion planning for a large number af three-di mensional objects in the presence of obstacles is a computa tional problem whose complexity is important to calibrate. In this paper we show that even the restricted two-dimensional problem for arbitrarily many rectangles in a rectangular region is PSPACE-hard. This result should be viewed as a guide to the difficulty, of the general problem and should lead researchers to consider more tractable restricted classes of motion problems of practical interest.
A Nondegenerate Kinematic Solution of a Seven-Jointed Robot Manipulator
Authors: Stanisic Michael M. , Pennock Gordon R.
Published: March 2007

Kinematically simple manipulators with six joints have unavoidable degenerate configurations that correspond to certain positions or orientations of the end-effector within the workspace. In these degenerate configurations, the end-effec tor of the manipulator is not capable of a motion with six independent degrees of freedom. Such a manipulator reduces the flexibility of a manufacturing system because manufac turing processes need to be planned so that positions or ori entations of the end-effector that correspond to degenerate configurations of the manipulator are not required.

In this paper a nondegenerate kinematic solution is devel oped for a kinematically simple seven-jointed robot manipu lator. The solution guarantees that the manipulator is capa ble of positioning and orienting its end-effector within the workspace without ever finding itself in a degenerate configu ration. The nondegenerate kinematic solution is in closed form and is developed from well-known methods and results in three-dimensional kinematics. It is believed that this seven-jointed robot manipulator will be most useful in flexible manufacturing systems.
The Robust Control of Robot Manipulators
Authors: Slotine Jean-Jacques E.
Published: March 2007

A new scheme is presented for the accurate tracking control of robot manipulators. Based on the more general suction control methodology, the scheme addresses the following problem: Given the extent of parametric uncertainty ( such as imprecisions or inertias, geometry, loads) and the frequency range of unmodeled dynamics ( such as unmodeled structural modes, neglected time delays) , design a nonlinear feedback controller to achieve optimal tracking performance, in a suitable sense. The methodology is compared with standard algorithms such as the computed torque method and is shown to combine in practice improved performance with simpler and more tractable controller designs.
Computer-Aided Off-Line Planning and Programming of Robot Motion
Authors: Hornick Mark L. , Ravani Bahram
Published: March 2007

Off-line planning of tasks and robot motion via the computer- graphics simulation of the robot and its environment is dis cussed. The internal structure and the mathematical basis of a generalized computer program developed for this purpose are described. Methods based on truncated trigonometric series for the off-line planning of robot trajectories and methods for the planning of multiple-segment robot motions with minimum cycle times are presented. The dynamic aspects of motion trajectories are discussed in relation to the generation of these time-optimal motions.
The Extraction of Curved Surface Features with Generic Range Sensors
Authors: Brown Michael K.
Published: March 2007

A generic range sensor is a member of a collection of sensors that provide surface location information. This collection includes ultrasonic, laser, structured light, and tactile sensors. The tactile sensor can be viewed as a degenerate range sensor when in contact with the surface. This paper will deal pri marily with the ultrasonic range sensor, which is probably the most difficult to handle, but extension of the techniques to other sensors is apparent.

The use of ultrasonic range finding to gather data about object surfaces in an air transmission medium poses several problems. First, there is very little information returned in a single range measurement. One range measurement tells us that some surface exists, approximately orthogonal to the transmission axis of the transducer, at the measured range. However, the surface can lie anywhere within the sensitivity pattern of the transducer, and it can be oriented at any angle that reflects energy back to the transducer. Moving the trans ducer adaptively allows us to obtain much more information about the surface including determination of the actual path of the signal echo point on the surface of the object. The topic of ultrasonic echo trajectories introduced in an earlier paper will be reviewed.

A property of ultrasonic echo trajectories on object surfaces is exploited. These trajectories are very nearly geodesic for the ultrasonic transducers being used when they are moved on a straight path parallel to a smooth regular surface. This property has several useful consequences. The surface path of the echo trajectory can be approximately determined. Fur thermore, surface normals can be obtained everywhere along this path. Thus, fundamental properties of the surface can be determined.
Using Backprojections for Fine Motion Planning with Uncertainty
Authors: Erdmann Michael
Published: March 2007

This paper outlines a method for planning motions in the presence of uncertainty. Tasks are modeled as geometrical goals in configuration space. The planning process consists of determining regions from which particular motions are guar anteed to reach a desired goal successfully. An algorithm is presented for backprojecting from desired goal states. The backprojection regions are computed by erecting constraints that geometrically capture the uncertainty in motion. The relationship of backprojections to goal recognizability is discussed within the formal framework of preimages. This relationship suggests a partitioning of desired goal states into recognizable goal states. Backprojections are actually per formed from this partitioning.
Singularities, Configurations, and Displacement Functions for Manipulators
Authors: Litvin F.L. , Zhang Yi  , Castelli V. Parenti , Innocenti C.
Published: March 2007

A manipulator is considered as a system of rigid bodies interconnected by joints that permit relative motions with certain degrees of freedom. Nonlinear equations that relate the parameters of relative motions generally do not provide unique solutions, and consequently the bodies (links) of the mechanical system may form various configuratxons.

The authors propose a method for determination of the configurations of this mechanical system and associated displacement functions that are based on the determination of singularities in motion of the mechanical system. Applica tion to the execution of prescribed trajectories by the Uni mation Puma Manipulator is also presented.