SEARCH · PubMed Health

Results for “Optimization”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 379 records · Page 21Linked to original sources

PubMed2006

Quality of life and pain in Chinese lung cancer patients: Is optimism a moderator or mediator?

OBJECTIVE: To clarify if optimism exerts a primarily moderating or mediating influence on the pain-QoL association in Chinese lung cancer patients. METHODS: About 334 Chinese lung cancer patients were interviewed at baseline during the first outpatient visit (Baseline), at 4 months after Baseline (FU1), and at 8 months after Baseline (FU2). Respondents completed the Chinese version of the FACT-G version-3 scale (FACT-G (Ch)). Optimism and pain were assessed using two 11-point self-rated items. Linear mixed effects (LME) models tested the moderating and mediating effects of optimism on QoL. RESULTS: Optimism, pain, and QoL were most strongly correlated at FU1. LME models failed to show any moderating effect by optimism on the pain-QoL association (standardized beta = -0.049, 95% CI -0.097 to 0.001). After adjustment for age, cancer stage, and disease recurrence, a modest mediating effect was observed for optimism on the pain-QoL association over the duration of the study (standardized beta = 0.047; Sobel test z = -4.317, p < 0.001). CONCLUSIONS: Optimism qualifies as a mediator between pain and QoL suggesting that pessimistic lung cancer patients are likely to experience greater QoL decrements in response to pain in the early post-diagnostic period. Effective pain control may be enhanced by inclusion of interventions that facilitate optimistic perspectives in patients. This study lends further support to the view that lung cancer patients' psychological needs are important in both pain control and QoL.

Adult↗

PubMed1990

DESIGN: computerized optimization of experimental design for estimating Kd and Bmax in ligand binding experiments. II. Simultaneous analysis of homologous and heterologous competition curves and analysis blocking and of "multiligand" dose-response surfaces.

We have developed a computer program, DESIGN, for optimization of ligand binding experiments to minimize the "average" uncertainty in all unknown parameters. An earlier report [G. E. Rovati, D. Rodbard, and P. J. Munson (1988) Anal. Biochem. 174, 636-649] described the application of this program to experiments involving a single homologous or heterologous dose-response curve. We now present several advanced features of the program DESIGN, including simultaneous optimization of two or more binding competition curves optimization of a "multiligand" experiment. Multiligand designs are those which use combinations of two (or more) ligands in each reaction tube. Such designs are an important and natural extension of the popular method of "blocking experiments" where an additional ligand is used to suppress one or more classes of sites. Extending the idea of a dose-response curve, the most general multiligand design would result in a "dose-response surface". One can now optimize the design not only for a single binding curve, but also for families of curves and for binding surfaces. The examples presented in this report further demonstrate the power and utility of the program DESIGN and the nature of D-optimal designs in the context of more complex binding experiments. We illustrate D-optimal designs involving one radioligand and two unlabeled ligands; we consider one example of homogeneous and several examples of heterogeneous binding sites. Further, to demonstrate the virtues of the dose-response surface experiment, we have compared the optimal surface design to the equivalent design restricted to traditional dose-response curves. The use of DESIGN in conjunction with multiligand experiments can improve the efficiency of estimation of the binding parameters, potentially resulting in reduction of the number of observations needed to obtain a desired degree of precision in representative cases.

Binding Sites↗

PubMed1987

A dynamic optimization technique for predicting muscle forces in the swing phase of gait.

The muscle force sharing problem was solved for the swing phase of gait using a dynamic optimization algorithm. For comparison purposes the problem was also solved using a typical static optimization algorithm. The objective function for the dynamic optimization algorithm was a combination of the tracking error and the metabolic energy consumption. The latter quantity was taken to be the sum of the total work done by the muscles and the enthalpy change during the contraction. The objective function for the static optimization problem was the sum of the cubes of the muscle stresses. To solve the problem using the static approach, the inverse dynamics problem was first solved in order to determine the resultant joint torques required to generate the given hip, knee and ankle trajectories. To this effect the angular velocities and accelerations were obtained by numerical differentiation using a low-pass digital filter. The dynamic optimization problem was solved using the Fletcher-Reeves conjugate gradient algorithm, and the static optimization problem was solved using the Gradient-restoration algorithm. The results show influence of internal muscle dynamics on muscle control histories vis a vis muscle forces. They also illustrate the strong sensitivity of the results to the differentiation procedure used in the static optimization approach.

Algorithms↗

PubMed1992

Optimization of 3D radiation therapy with both physical and biological end points and constraints.

A new optimization model is described and its clinical usefulness is demonstrated. The optimization technique was developed to allow computer optimization of 3-dimensional radiation therapy plans with biological models of tumor and normal tissue response to radiation as well as with scores based on physical dose. The emphasis was placed on the optimization model, which should describe, as closely as possible, the goal of the radiation treatment, which is eradication of the tumor while sparing normal tissues. Since the statement of the goals may vary from case to case, a technique that allows a variety of objective functions and types of constraints was developed. The optimization algorithm is capable of handling nonlinear and even discrete score (objective) functions and constraints and effectively explores the vast space of feasible solutions in a relatively short time (minutes of MicroVax 3200 CPU time). An example of computer optimization of radiation therapy of a chordoma of the sphenoid bone using x-ray and proton beams is shown and compared with the best plans achieved by an experienced planner. Directions for future development of the algorithm, allowing optimization of beam orientation, are presented.

Chordoma↗

PubMed1994

Tissue heterogeneity effects in treatment plan optimization.

PURPOSE: There is general agreement that tissue density correction factors improve the accuracy of dose calculations. However, there is disagreement over the proper heterogeneity correction algorithm and a lack of clinical experience in using them. Therefore, there has not been widespread implementation of density correction factors into clinical practice. Furthermore, the introduction of optimized conformal therapy leads to new and radically different treatment techniques outside the clinical experience of the physician. It is essential that the effects of tissue density corrections are understood so that these types of treatments can be safely delivered. METHODS AND MATERIALS: In this paper, we investigate the effect of tissue density corrections on optimized conformal type treatment planning in the thorax region. Specifically, we study the effects on treatment plans optimized without type treatment planning in the thorax region. Specifically, we study the effects on treatment plans optimized without tissue density corrections, when those corrections are applied to the resulting dose distributions. These effects are compared for two different conformal techniques. RESULTS: This study indicates that failure to include tissue density correction factors results in an increased dose of approximately 5-15%. This is consistent with published studies using conventional treatment techniques. Additionally, the high-dose region of the dose distribution expands laterally into the uninvolved lung and other normal structures. The use of dose-volume histograms to compare these distributions demonstrates that treatment plans optimized without tissue density corrections lead to an increased dose to uninvolved normal structures. This increase in dose often violates the constraints used to determine the optimal solution. CONCLUSIONS: The neglect of tissue density correction factors can result in a 5-15% increase in the delivered dose. In addition, suboptimal dose distributions are produced. To benefit from the advantages of optimized conformal therapy in the thorax, tissue density correction factors should be used.

Carcinoma↗

PubMed1994

Optimizing the time course of brachytherapy and other accelerated radiotherapeutic protocols.

PURPOSE: It is likely that early-responding tissues, such as tumors, repair sublethal damage more rapidly than do late-responding tissues. This difference can be exploited to design protocols with a significantly improved therapeutic advantage for accelerated radiotherapeutic regimens, including brachytherapy. METHODS AND MATERIALS: The time course of potential protocols is computer optimized, maximizing the therapeutic difference between tumor-control probability (TCP), and normal-tissue complication probability (NTCP). These quantities are evaluated with the linear-quadratic model, using clinically derived parameters. The optimization is performed by individually adjusting doses in different parts of the treatment, maximizing the therapeutic advantage. In the main calculations, half times for damage repair were T1/2(late) = 4 h, T1/2(early) = 0.5 h. Two component (fast/slow) repair processes were also investigated. RESULTS: Protocols determined by optimization have significantly greater therapeutic advantage than continuous low-dose rate (CLDR) protocols of the same overall dose and time. The optimized protocols are either (a) acute-dose/gap/CLDR/gap/acute-dose; or (b) a series of acute doses separated by 3-4 h. As a typical example, results are given for 60 Gy/120 h CLDR brachytherapy, which is assumed to give NTCP = 0.2 and TCP = 0.8. Under our assumptions, optimized regimes, with the same overall time and dose, produce an NTCP of approximately 0.11 and TCP of approximately 0.83, a significant therapeutic gain over CLDR. CONCLUSION: Difference in repair rates between early- and late-responding tissues can be exploited to produce clinically practical protocols that are significantly superior to current regimens. Such optimized protocols produce slightly better tumor control than CLDR with the same overall dose and time, significantly less late damage, and similar early normal-tissue sequellae. Temporal optimization, thus, promises to be a powerful tool in designing better treatment protocols.

Animals↗

PubMed1995

Treatment planning optimization for multiple arcs stereotactic radiosurgery using a linear accelerator.

PURPOSE: Multiarc stereotactic radiosurgery is a technique used to irradiate an intracranial tumor with minimal damage to the surrounding normal tissue. The purpose of this paper is to present a method for and the results from optimizing three dimensional (3D) treatment dose for multiarc stereotactic radiosurgery. METHODS AND MATERIALS: The normal procedure for a physician-physicist team designing a treatment plan for multiarc stereotactic radiosurgery is the trial-and-error approach of changing the collimator size and the isocenter of radiation by viewing the isodose curves on a two dimensional (2D) computed tomography (CT) or magnetic resonance imaging (MRI) image plane. Not only is this time consuming, but the resulting treatment plan is not optimal in most, if not all, cases. One reason for such nonconformal isodose curves is that the same collimator size is used for all arcs. However, it is very difficult to determine manually the different collimator sizes for different arcs. A derivative free optimization method is used to optimize the collimator size for each arc, as well as the 3D coordinates of the isocenter(s). RESULTS: One spherical and two ellipsoidal artificial tumors, and one actual tumor, were used to show the utilities of the optimization process. The 90% isodose curves resulting from optimization conform very well with the tumor; whereas the 90% isodose curves from the conventional method either do not envelop the entire tumor when the collimator size is too small, or a large volume of normal tissue is also irradiated by the 90% dose when the next larger collimator size is used. CONCLUSIONS: When the collimator size for each arc and the location of the isocenters(s) are optimized in a multiarc stereotactic surgery treatment plan, the 90% isodose curve conforms to the tumor much better than when the same collimator size is used for all arcs.

Algorithms↗

PubMed2006

Correlation of echo-Doppler optimization of atrioventricular delay in cardiac resynchronization therapy with invasive hemodynamics in patients with heart failure secondary to ischemic or idiopathic dilated cardiomyopathy.

This study investigated the optimal echocardiographic indexes to determine the most hemodynamically appropriate atrioventricular (AV) delay in cardiac resynchronization therapy (CRT) for heart failure. Doppler echocardiographic optimization of AV delay in CRT has not been correlated with invasive hemodynamic indexes. In 30 patients who underwent CRT, invasive left ventricular (LV) pressure measurements with a sensor-tipped pressure guidewire and Doppler echocardiographic examination were performed <24 hours after pacemaker implantation. Invasively, the optimal sensed AV delay was determined by LV dP/dt(max). The Doppler echocardiographic methods evaluated were the velocity-time integral (VTI) of the transmitral flow (EA VTI), diastolic filling time (EA duration), the VTI of the LV outflow tract or aorta (LV VTI), and Ritter's formula. Biventricular pacing with optimized interventricular and AV delay increased LV dP/dt(max) from 777 +/- 149 to 1,010 +/- 163 dynes/s (p<0.0001). The optimal AV delay with the EA VTI method was concordant with LV dP/dt(max) in 29 of 30 patients (r = 0.96), with EA duration in 20 of 30 patients (r= 0.83), with LV VTI in 13 patients (r = 0.54), and with Ritter's formula in none of the patients (r = 0.35). In conclusion, to obtain the optimal acute hemodynamic benefit of CRT, Doppler echocardiography is a reliable tool to optimize the AV delay compared with the invasive LV dP/dt(max). The measurement of the maximal VTI of mitral inflow is the most accurate method.

Aged↗

PubMed2006

Long-term effects of dual-chamber pacing with periodic echocardiographic evaluation of optimal atrioventricular delay in patients with hypertrophic cardiomyopathy >50 years of age.

Various treatment modalities have been introduced to reduce the subaortic pressure gradient in patients with obstructive hypertrophic cardiomyopathy, including pacemaker insertion. Complete ventricular capture during pacing is essential and requires optimization of the atrioventricular interval (AVI). In this study, a protocol using echocardiographic examination assessing the changes in the left ventricular outflow tract (LVOT) gradient in different AVIs, pacing rates, and pacing modes was used for optimal pacemaker programming. Twenty-five patients with obstructive hypertrophic cardiomyopathy were implanted with DDD pacemakers and evaluated prospectively. The LVOT gradient was measured during periodic evaluations every 3 to 6 months. Gradient measurements were done with 5 different AVIs and 3 different rate combinations. After each evaluation, the optimal AVI, pacing rate, and mode were set on the basis of the minimal LVOT gradient not associated with systolic arterial cuff pressure reduction. Follow-up ranged from 18 to 126 months. Peak LVOT gradient immediately decreased in 92% of patients. During follow-up, the optimal AVI was prolonged in most patients. Sixty-four percent of patients showed a clear relation between pacemaker modifications and gradient reduction. In 75% of these patients, optimal gradient reduction required repeated AVI and pacing rate programming on the basis of echocardiographic evaluation. Symptoms decreased in 92% of patients, and New York Heart Association class improved significantly (3.1+/-0.7 vs 1.3+/-0.4, p<0.001) during follow-up. The symptomatic reduction was positively correlated with the LVOT gradient reduction. In conclusion, DDD pacing is effective in reducing the LVOT gradient and improving functional capacity in adult patients with hypertrophic cardiomyopathy. Pacemaker programming with the periodic echocardiographic evaluation of the optimal AVI, pacing rate, and mode is imperative for optimal results.

Aged↗

PubMed2006

Temporal variation in optimal atrioventricular and interventricular delay during cardiac resynchronization therapy.

BACKGROUND: Tailored atrioventricular delay (AVd) and interventricular delay (VVd) combination improves hemodynamics in patients treated with cardiac resynchronization therapy (CRT). Whether tailored AVd-VVd combination changes over time is not known. METHODS AND RESULTS: Twenty-two patients (18 M, aged 69.9 +/- 12.5 years, New York Heart Association class III, QRS > or = 130 ms, ejection fraction 29.6 +/- 8.8%) were implanted with a biventricular device with programmable VVd. Myocardial performance index (MPI) was evaluated during pacing at different VVds and AVds at baseline and after 6 and 12 months. The optimal AVd-VVd combination was identified by the minimum MPI. After optimization, the appropriate AVd-VVd combination was programmed in each patient. MPI at 6-month follow-up after optimization was significantly higher compared with baseline (.79 +/- .21 vs. .59 +/- .15, P < .05). Re-optimization of AVd-VVd combination was required after 6 months in 21 of 22 (95%) patients. Re-optimization significantly reduced MPI compared with the value prior to re-optimization (.56 +/- .15 vs. .79 +/- .21, P < .05). The MPI remained unchanged at 12-month compared with 6-month follow-up (.59 +/- .19 vs. .56 +/-.15, P = NS). Clinical symptoms and reverse left ventricular remodeling were sustained at 6-month and 12-month follow-up. CONCLUSION: Optimal AVd and VVd combination changes over time in patients with heart failure. Sustained improvement in clinical symptoms and reverse left ventricular remodeling after CRT are not temporally associated with improvement in MPI.

Aged↗

PubMed2006

Constrained optimization of a preparative ion-exchange step for antibody purification.

Today, the optimization of chromatographic separation is usually based on experimental work and rule of thumb. The process and analytical technology (PAT) initiative, of the US Food and Drug Administration, has provided the opportunity of using model-based approach when designing downstream processing of pharmaceutical substances. A nonlinear chromatography model was used in this study to optimize a preparative ion-exchange separation step involving two components. Separation was simulated with the general rate model employing Langmuir kinetics. Optimization was performed with an indirect method allowing constraints on the purity, thus avoiding sub-optimization, which can lead to noisy objective functions. The six decision variables used in the optimizations were flow rate, loading volume, initial salt concentration in the elution, final salt concentration in the linear elution gradient and the two cut points. A graphical representation of the effect of the decision variables on the objective function was used to verify that the optimization had converged to the true optimum. The optimal operating points, using productivity and yield separately as objective functions, were found and compared with the product of productivity and yield as objective function. The optimum obtained with this objective function had a lower productivity, than the productivity function, but much higher yield, which makes it a good substitute for a cost function.

Antibodies↗

PubMed2006

Static optimization of muscle forces during gait in comparison to EMG-to-force processing approach.

Individual muscle forces evaluated from experimental motion analysis may be useful in mathematical simulation, but require additional musculoskeletal and mathematical modelling. A numerical method of static optimization was used in this study to evaluate muscular forces during gait. The numerical algorithm used was built on the basis of traditional optimization techniques, i.e., constrained minimization technique using the Lagrange multiplier method to solve for constraints. Measuring exact muscle forces during gait analysis is not currently possible. The developed optimization method calculates optimal forces during gait, given a specific performance criterion, using kinematics and kinetics from gait analysis together with muscle architectural data. Experimental methods to validate mathematical methods to calculate forces are limited. Electromyography (EMG) is frequently used as a tool to determine muscle activation in experimental studies on human motion. A method of estimating force from the EMG signal, the EMG-to-force approach, was recently developed by Bogey et al. [Bogey RA, Perry J, Gitter AJ. An EMG-to-force processing approach for determining ankle muscle forcs during normal human gait. IEEE Trans Neural Syst Rehabil Eng 2005;13:302-10] and is based on normalization of activation during a maximum voluntary contraction to documented maximal muscle strength. This method was adapted in this study as a tool with which to compare static optimization during a gait cycle. Muscle forces from static optimization and from EMG-to-force muscle forces show reasonably good correlation in the plantarflexor and dorsiflexor muscles, but less correlation in the knee flexor and extensor muscles. Additional comparison of the mathematical muscle forces from static optimization to documented averaged EMG data reveals good overall correlation to patterns of evaluated muscular activation. This indicates that on an individual level, muscular force patterns from mathematical models can arguably be more accurate than from those obtained from surface EMG during gait, though magnitude must still be validated.

Adult↗

PubMed2025

Optimizing participant and community engagement in cancer genomic sequencing research.

PURPOSE: We describe strategies implemented across research centers of the Participant Engagement and Cancer Genome Sequencing (PE-CGS) Network to optimize engagement of participants and communities in cancer genomics research. We also present consensus definitions of engagement and engagement optimization, informed by our shared experiences in the Network. METHODS: Key informant interviews and a document review identified engagement and optimization strategies across PE-CGS research centers. Findings were synthesized using qualitative content analysis. Consensus on definitions of engagement and optimization were developed through iterative review by PE-CGS members. RESULTS: PE-CGS research centers adopted tailored strategies based on community needs and scientific gaps. Engagement strategies included community-based efforts (eg, advisory boards and newsletters) and participant-focused approaches (eg, enhanced informed consent and decision support tools). Optimization strategies leveraged scientific methods (eg, randomized controlled trials and surveys) to evaluate engagement. Engagement was described as the sustained and meaningful interactions between researchers, participants, and communities. Optimization was described as the application of scientific methods to refine and improve engagement and research processes and outcomes. CONCLUSION: Engagement and optimization strategies have informed research planning, conduct, and dissemination across PE-CGS. These approaches and definitions provide a foundation for developing evidence-based practices to strengthen participant and community involvement in cancer genomics research.

Humans↗

PubMed2004

An optimization algorithm of dose distribution using attraction-repulsion model (application to low-dose-rate interstitial brachytherapy).

PURPOSE: To optimize dose distribution for prostate cancer in low-dose-rate interstitial brachytherapy, we have developed a new algorithm named the Attraction-Repulsion Model. The purpose was to find the optimal source configuration. METHODS AND MATERIALS: The Attraction-Repulsion Model is used to optimize the dose distribution by finding the best seed configuration. We arranged grids at intervals of a certain space inside and established target and critical organs as areas of interest. We can make an attribute for grids, and the grids show attraction or repulsion depending on dose delivered from source. Source position is changed by the forces that the grids impose to the sources. A calculation was done repeatedly until the attraction and repulsion forces reached a balance. The optimal configuration was established when the sources reached a stable distribution in time. To evaluate the optimization plan, dose-volume histograms were used. RESULTS: Source configuration can be optimized automatically. The calculation time was approximately 5 min. The V100, V150, V200, and D90 of the target were 95%, 39%, 9%, and 157 Gy, respectively. V150 of the urethra and V80 of the rectum were 2% and 0%, respectively. CONCLUSION: This method can optimize the dose distribution objectively.

Algorithms↗

PubMed2006

Computer optimization of noncoplanar beam setups improves stereotactic treatment of liver tumors.

PURPOSE: To investigate whether computer-optimized fully noncoplanar beam setups may improve treatment plans for the stereotactic treatment of liver tumors. METHODS: An algorithm for automated beam orientation and weight selection (Cycle) was extended for noncoplanar stereotactic treatments. For 8 liver patients previously treated in our clinic using a prescription isodose of 65%, Cycle was used to generate noncoplanar and coplanar plans with the highest achievable minimum planning target volume (PTV) dose for the clinically delivered isocenter and mean liver doses, while not violating the clinically applied hard planning constraints. The clinical and the optimized coplanar and noncoplanar plans were compared, with respect to D(PTV,99%), the dose received by 99% of the PTV, the PTV generalized equivalent uniform dose (gEUD), and the compliance with the clinical constraints. RESULTS: For each patient, the ratio between D(PTV,99%) and D(isoc), and the gEUD(-5) and gEUD(-20) values of the optimized noncoplanar plan were higher than for the clinical plan with an average increase of respectively 18.8% (range, 7.8-24.0%), 6.4 Gy (range, 3.4-11.8 Gy), and 10.3 Gy (range, 6.7-12.5). D(PTV,99%)/D(isoc), gEUD(-5), and gEUD(-20) of the optimized noncoplanar plan was always higher than for the optimized coplanar plan with an average increase of, respectively, 4.5% (range, 0.2-9.7%), 2.7 Gy (range, 0.6-9.7 Gy), and 3.4 Gy (range, 0.6-9.9 Gy). All plans were within the imposed hard constraints. On average, the organs at risk were better spared with the optimized noncoplanar plan than with the optimized coplanar plan and the clinical plan. CONCLUSIONS: The use of automatically generated, fully noncoplanar beam setups results in plans that are favorable compared with coplanar techniques. Because of the automation, we found that the planning workload can be decreased from 1 to 2 days to 1 to 2 h.

Algorithms↗

PubMed2006

Dispositional optimism and the risk of depressive symptoms during 15 years of follow-up: the Zutphen Elderly Study.

OBJECTIVE: It is unclear whether the personality trait of dispositional optimism, defined in terms of generalized positive outcome expectancies, life engagement, and a future orientation, has a protective effect on the development of depression in community-dwelling elderly men. METHODS: We included 464 men aged 64 to 84 years (mean 70.8; SD 4.6) with complete data at baseline and at 5 years of follow-up in a prospective cohort study with a follow-up period of 15 years. In 1985, 1990, 1995 and 2000 dispositional optimism was assessed using a 4-item questionnaire, and in 1990, 1995 and 2000 depressive symptoms were assessed by the Zung self-rating depression scale (SDS). Logistic regression was used to estimate odds ratios for the development of depressive symptoms (i.e., Zung SDS > or = 50). RESULTS: The cumulative incidence for depressive symptoms was 44% (n = 202) after 15 years follow-up. Dispositional optimism predicted for a lower cumulative incidence of depressive symptoms with an odds ratio of 0.23 (95% confidence interval 0.15-0.36; high vs. low optimism). The protective effect remained unaffected after multivariate adjustment for age, self-rated health, cardiovascular disease, education, and physical activity. In men free of depressive symptoms in 1990, the protective effect of dispositional optimism persisted. LIMITATION: The dispositional optimism scale has not been validated against the 'Life Orientation Test'. CONCLUSIONS: Dispositional optimism protects against the development of depressive symptoms during 15 years of follow-up in elderly community-dwelling men.

Activities of Daily Living↗

PubMed2006

Optimal risk adjustment with adverse selection and spatial competition.

Paying insurers risk-adjusted prices for covering different individuals can correct selection incentives and induce the market to provide optimal insurance policies. To calculate the optimal risk-adjusted prices we need to know (a) what the optimal policies are; (b) how much they cost; and (c) how competitive the market is. We examine these issues in a model with spatial heterogeneity and adverse selection. Market equilibrium is characterized, and delivery of the socially optimal insurance policies is possible, as long as providers are paid risk-adjusted fees for each individual they serve. When the payment can be made on the basis of an individual's risk, it should be sufficient to cover the expected cost of the socially optimal policy for that person, plus a mark-up. If payments can be made only on the basis of a partially informative signal, the optimal risk-based payments should be adjusted according to a simple linear transformation, identified by Glazer and McGuire [Glazer, J., McGuire, T., 2000. Optimal risk adjustment of health insurance premiums: an application to managed care.

Economic Competition↗

PubMed2004

Multiple-year optimization of conservation effort and monitoring effort for a fluctuating population.

We consider optimal conservation strategies for an endangered population. We assume that juvenile survival is affected by unpredictable environmental fluctuation and can be improved by costly conservation effort. The initial population size is not accurately known at the time that the conservation effort level is chosen, but the uncertainty of its estimate can be reduced by a costly monitoring effort. In a previous paper, we analysed the optimal management strategy that minimizes a weighted sum of extinction probability and economic costs when only a single year is considered. Here we examine the case in which the conservation period lasts for several years by dynamic programming with incompletely observed process states. We study the optimal levels of the conservation and the monitoring efforts, and their dependence on the length of the conservation period and other parameters. The main conclusions are: (1) The optimal conservation effort in the first year depends on the accuracy of the information on the population size in the first year, but is almost independent of the accuracy of the information in later years. (2) When the risk of population extinction is small, the optimal conservation effort increases with the uncertainty of the population size. In contrast when the population is endangered, the optimal conservation effort decreases with the uncertainty of the population size. (3) The optimal conservation and monitoring efforts both increase with the length of the conservation period, provided that the population is relatively safe. However, if the population is endangered, both types of effort become smaller when the conservation period increases.

Animals↗