PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “optimal control”

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 163 records · Page 9Linked to original sources
PubMed2002

Cancer pain management among underserved minority outpatients: perceived needs and barriers to optimal control.

BACKGROUND: Minority patients with cancer are at risk for undertreatment of cancer-related pain. Most studies of patient-related barriers to pain control have surveyed primarily non-Hispanic Caucasian patients. The purpose of the current study was to explore barriers to optimal pain management among African-American and Hispanic patients with cancer through the use of structured patient interviews. Structured interviews allowed the authors to probe for previously unidentified barriers to pain management in these populations. METHODS: Thirty-one socioeconomically disadvantaged minority patients with cancer (14 African-American patients and 17 Hispanic patients) who had cancer-related pain completed structured interviews that assessed three main content areas: information and communication regarding cancer pain, treatment of cancer pain, and the meaning of cancer pain. RESULTS: The African-American and Hispanic patients reported severe pain and many concerns about pain management. The majority of patients in both ethnic groups expressed a belief in stoicism and concerns about possible addiction to opioid medications and the development of tolerance. The patients described their physicians as the most frequent and trusted source of information about cancer pain. However, patients also reported difficulties with communication and a reluctance to complain of pain. CONCLUSIONS: The reported barriers to pain management indicate that socioeconomically disadvantaged African-American and Hispanic patients can benefit from educational interventions on cancer pain that dispel myths about opioids and teach patients to communicate assertively about their pain with their physicians and nurses.

Black or African American↗
PubMed1996

[Optimal control by ondansetron of acute and prolonged emesis induced by chemotherapy without cisplatin].

Chemotherapy-induced emesis is dependent not only on individual parameters but also on treatment parameters (type and dose of the cytotoxic drug, combination with other cytotoxic drugs). Cyclophosphamide-based chemotherapy is potentially emetogenic and the emtogenicity is proportionally dependent on the dose. Therefore, the preventive antiemetic treatment must be adapted to this emetogenic risk. A number of studies have assessed the efficacy of ondansetron, a highly selective 5-HT3 receptor antagonist, for the control of 'non cisplatin' chemotherapy. In mild emetogenic regimens, oral ondansetron is more effective than placebo and its efficacy is similar to the classic antiemetic regimen metoclopramide-dexamethasone. Concerning moderately emetogenic chemotherapies, iv ondansetron is highly effective and its effecicay is superior to that of metoclopramide and alizapride. Delayed nausea and vomiting can be controlled by an oral ondansetron treatment. This allows to maintain the good response obtained by the initial antiemetic regimen. With very high doses of cyclophosphamide, as in conditioning chemotherapy and total body irradiation prior to bone marrow transplantation, no optimal antiemetic treatment has still been defined; but the combination of ondansetron with dexamethasone should be used according to the poor control obtained with ondansetron alone. However, studies combining 5-HT3 receptor antagonists with dexamethasone are warranted in order to define the optimal treatment in this particularly emetogenic treatment setting.

Antiemetics↗
PubMed2003

Deciphering the reaction dynamics underlying optimal control laser fields.

Femtosecond high-resolution pump-probe experiments have been used together with theoretical ab initio quantum calculations and wave packet dynamics simulations to decode an optimal femtosecond pulse that is generated from adaptive learning algorithms. This pulse is designed to maximize the yield of the organometallic ion CpMn(CO)3 while hindering the competing fragmentation. The sequential excitation and ionization of the target ion are accomplished by an optimized field consisting of two dominant subpulses with optimal frequencies and time delays.

Journal Article↗
PubMed2001

Insulin therapy: optimizing control in type 1 and type 2 diabetes.

Insulin has been available for therapeutic use for more than 75 years and remains a powerful pharmacologic tool with nearly unlimited potential to lower plasma glucose levels in patients with diabetes. Required essentially by all patients with type 1 diabetes and many patients with type 2 diabetes, insulin is capable of restoring near-normoglycemia--the primary treatment goal to forestall the onset and progression of long-term complications. Attainment and maintenance of near-normal glycemic control can be achieved with the use of insulin replacement strategies designed to simulate the physiologic, nondiabetic patterns of insulin secretion in response to 24-hour postabsorptive and postprandial glucose profiles. This article reviews the physiologic basis and current therapeutic agents for optimal insulin replacement and provides practical clinical guidelines and strategies to achieve near-normal glycemic control in patients with either type 1 or type 2 diabetes.

Blood Glucose↗
PubMed2003

Controlled optimization of mode conversion from electron Bernstein waves to extraordinary mode in magnetized plasma.

In the CDX-U spherical torus, agreement between radiation temperature and Thomson scattering electron temperature profiles indicates approximately 100% conversion of thermally emitted electron Bernstein waves to the X mode. This has been achieved by controlling the electron density scale length (L(n)) in the conversion region with a local limiter outside the last closed flux surface, shortening L(n) to the theoretically required value for optimal conversion. From symmetry of the conversion process, prospects for efficient coupling in heating and current drive scenarios are strongly supported.

Journal Article↗
PubMedDate not supplied

Optimal control of receptor reinsertion in the low density lipoprotein endocytic cycle.

On the basis of this study, it is concluded that within physiological limits the minimum value for the mean capture time of LDL receptors by coated pits must be induced fundamentally by an optimal characterization of their insertion rate function. The corresponding steady-state surface aggregation patterns for the unbound receptors are consistent with experimental observations. The implications of the derived results for the estimation of the minimum physiological value for the referred mean capture time are also discussed.

Coated Pits, Cell-Membrane↗
PubMed1996

Optimal control of cyclophosphamide-induced emesis.

Cyclophosphamide induces moderate to severe emesis. The severity of emesis is dependent on the dose of cyclophosphamide and on the addition of other cytotoxic drugs. A review of the literature dividing studies according to the dose of cyclophosphamide and the specific cytotoxic combination shows that ondansetron plus dexamethasone provides optimal antiemetic therapy in patients receiving standard or high-dose cyclophosphamide (> or = 450 mg/m2). These studies also show that it is important to give antiemetic therapy to cover the prolonged duration emesis and nausea induced by these regimens, e.g. intravenous CMF/(F)AC/(F)EC. For continuous 'oral' (low-dose) CMF chemotherapy, oral ondansetron or oral metoclopramide plus intravenous (or possibly oral) dexamethasone are effective antiemetic therapies.

Antiemetics↗
PubMed2006

Optimal control of set-up margins and internal margins for intra- and extracranial radiotherapy using stereoscopic kilovoltage imaging.

In this paper the clinical introduction of stereoscopic kV-imaging in combination with a 6 degrees-of-freedom (6 DOF) robotics system and breathing synchronized irradiation will be discussed in view of optimally reducing interfractional as well as intrafractional geometric uncertainties in conformal radiation therapy. Extracranial cases represent approximately 70% of the patient population on the NOVALIS treatment machine (BrainLAB A.G., Germany) at the AZ-VUB, which is largely due to the efficiency of the real-time positioning features of the kV-imaging system. The prostate case will be used as an example of those target volumes showing considerable changes in position from day-to-day, yet with negligible motion during the actual course of the treatment. As such it will be used to illustrate the on-line target localization using kV-imaging and 6 DOF patient adjustment with and without implanted radio-opaque markers prior to treatment. Small lung lesion will be used to illustrate the system's potential to synchronize the irradiation with breathing in coping with intrafractional organ motion.

Brain Neoplasms↗
PubMed1990

Optimal control for a cancer chemotherapy problem with general growth and loss functions.

We investigate a model of a cancer chemotherapy problem where the aim is to minimize the tumor burden at the end of the treatment period while maintaining a normal cell population above a lower level as a limit of toxicity. The analysis is performed for general classes of growth and loss functions. The optimal drug dose is maximum initially so that the normal cell population is driven down to its lower level, and then the drug level is chosen to maintain the normal cell population there until the end of treatment. During treatment the number of tumor cells is always decreasing.

Antineoplastic Agents↗
PubMed1990

Some optimal control problems in cancer chemotherapy with a toxicity limit.

We investigate some models of a cancer chemotherapy problem where the normal cell population must be maintained above a lower limit and a measure of the total drug use is bounded as a limit of toxicity. Three sets of objective functions are analyzed, and some numerical solutions are provided for the last case. In all cases the structure of the optimal solution is similar, including a bolus application of drug followed later by continuous infusion.

Antineoplastic Agents↗
PubMed2001

A fast algorithm to find optimal controls of multiantenna applicators in regional hyperthermia.

The goal of regional hyperthermia is to heat up deeply located tumours to temperatures above 42 C while keeping the temperatures in normal tissues below tissue-dependent critical values. The aim of this paper is to describe and analyse functions which can be used for computing hyperthermia treatment plans in line with these criteria. All the functionals considered here can be optimized by efficient numerical methods. We started with the working hypothesis that maximizing the quotient of integral absorbed power inside the tumour and a weighted energy norm outside the tumour leads to clinically useful power distributions which also yield favourable temperature distributions. The presented methods have been implemented and tested with real patient data from the Charité Berlin. Campus Virchow-Klinikum. The results obtained by these fast routines are comparable with those obtained by relatively expensive global optimization techniques. Thus the described methods are very promising for online optimization in a hybrid system for regional hyperthermia where a fast response to MR-based information is important.

Algorithms↗
PubMed1993

Somatic hypermutation in B cells: an optimal control treatment.

The vertebrate immune system generates high-affinity antibodies to external antigens through a process of somatic hypermutation that takes place in germinal centers formed in the secondary lymphoid tissues. B cells proliferating in these germinal centers experience random mutations in the genes encoding the variable region of their immunoglobulin molecules and are subsequently selected for high-affinity binding to antigen. These germinal center reactions last for only about 2 weeks, yet in that time typically produce multiple point mutations resulting in affinity increases of factors of ten to a hundred or more. We have attempted to understand this extraordinary effectiveness by causing the problem of affinity maturation as an optimization problem in which a quantity that we call the total affinity is maximized as a functional of mu(t), the mutation rate as a function of time. We have developed a single-compartment model for the process and an optimization algorithm based on the Pontryagin maximum principle. Our results show that the optimum mutation schedule is one with brief bursts of high mutation rates interspersed between periods of mutation-free growth. Though this result at first seems highly non-physiological, we show that, in fact, it provides a framework within which the anatomy and kinetics of the germinal center reaction can be understood.

Animals↗
PubMed1984

Forecasting cancer trends to optimize control strategies.

Population projections and age-stratified cancer rates were used to forecast the trends for cancer occurrence for the United States during the coming decades: A progressive increase in the number of new cases is already predetermined by the high birth rate that occurred during the middle part of the century, and it will lead to nearly a doubling in the number of cases in about 4 decades. The demographic circumstances that determine the per capita costs of cancer are likely to worsen, because expected population trends will produce a deteriorating per capita economic base. Furthermore, the high costs of emerging treatment technologies are likely to magnify the deterioration ever further. Development of methods for cancer trend forecasting can provide a sound and accurate foundation for planning a comprehensive national strategy for optimal partitioning of research resources between the need for development of new treatments and the need for new research directed toward primary preventive measures.

Adolescent↗
PubMed2000

Optimal control for a stochastic model of cancer chemotherapy.

Chemotherapy is useful in a number of cancers to reduce or eliminate residual disease. When used in this way the objective is to maximise the likelihood that the cancer will be eliminated. In this article, we extend a stochastic model of chemotherapy for cancer to incorporate its concomitant effect on the normal system and derive overall measures of outcome. The model includes the development of drug resistance and is sufficiently flexible to include a variety of tumour and normal system growth functions. The model is then applied to situations previously examined in the literature and it is shown that early intensification is a common feature of successful regimens in situations where drug resistance is likely. The model is also applied to data collected from clinical trials analysing the effect of adriamycin, and cyclophosphamide, methotrexate and 5-flourouracil (CMF) therapy in the treatment of operable breast cancer. The model is able to mimic the data and provides a description of the optimal regimen.

Antimetabolites, Antineoplastic↗
PubMed1991

High cell density fermentation of recombinant Escherichia coli with computer-controlled optimal growth rate.

In recent years recombinant DNA technology has enabled us to produce various proteins of therapeutic importance with microorganisms. As an appropriate host organism, E. coli plays a dominant role. Yields of E. coli dry cell mass in shaker flask culture range from 1-2 g/L, whereas in fermentors up to 10 g dry cells/L can be achieved. ZIMET and GBF have developed a high cell density fermentation process that produces E. coli (on a glucose/mineral salt medium) up to more than 100 g dry cells/L in a special fed-batch mode. This cultivation strategy prevents oxygen limitation and hence the accumulation of acetate and other metabolic byproducts. The specific growth rate can be adjusted so that product formation reaches its optimum value. An example of the production of alpha1-interferon is presented. The high cell density fermentations were realized in 30- and 450-L Chemap fermentors (ZIMET) and in a three-stage bioreactor scale-up system (72, 300, and 1,500 L) developed in cooperation with GBF and B. Braun Melsungen AG. Multiloop controllers were used to control the process variables.

Biotechnology↗
PubMed1993

[Endoscopically controlled optimization of trans-scleral suture fixation of posterior chamber lenses in the ciliary sulcus].

Two technical difficulties have to be overcome in transscleral suture fixation of posterior chamber intraocular lenses (PCL) in the ciliary sulcus: first, exact needle penetration through the sulcus, and second, exact positioning of the PCL haptics in the sulcus. Incongruence of the two may lead to long-term complications by compression or even strangulation of ciliary processes. Intraocular endoscopy was used intraoperatively to visualize the site of needle penetration and the final location of the haptics in patients. It turned out that with our previously described standard techniques the precision was far less than anticipated. Thus, new technical ways had to be sought to improve the precision of positioning. In secondary implantation without perforating keratoplasty we achieved the best results when the needle was passed ab externo before opening the eye and before anterior vitrectomy, taking advantage of a precisely prepared sclerocorneal zone. Passing the needle ab externo in an already hypotonic eyeball gives much less precise results. In combination with perforating keratoplasty with an open-sky approach, needle penetration ab interno is reliable. Correct positioning of the PCL haptics is at least as difficult as correct needle penetration, a fact which up to now has mostly been ignored. In 33 consecutively operated eyes the technique of implantation and PCL design was varied under endoscopical control.(ABSTRACT TRUNCATED AT 250 WORDS)

Combined Modality Therapy↗
PubMed1996

Optimal control of interferon-gamma and tumor necrosis factor-alpha by interleukin-10 produced in response to one HLA-DR mismatch during the primary mixed lymphocyte reaction.

Interleukin (IL)-10 is an immunosuppressive cytokine potentially involved in the control of the allogeneic response. Several studies failed to detect it in mixed lymphocyte reaction supernatants. However, experiments using IL-10-specific antibodies, revealing its inhibitory action on interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha, provided indirect evidence that endogenous IL-10 was produced. The aim of the present work is to elucidate the role of IL-10 during mixed lymphocyte reaction and to investigate the influence of HLA-DR antigens on its production and on the regulatory loop involving TNF-alpha and IFN-gamma. Using a highly sensitive ELISA, a significant (P < 0.0001) but low IL-10 release could be detected (33.7 +/- 3.6 pg/ml) in response to HLA-DR disparities. However, IL-10 release was not graded as 1 DR mismatch (MM)-induced maximal secretion (32.3 +/- 5.1 pg/ml). This contrasted with TNF-alpha and IFN-gamma productions, which significantly increased in 2 DR MM pairs. Addition to IL-10-specific antibodies resulted in higher enhancement of INF-gamma (235 +/- 38% vs. 122 +/- 39%, P = 0.02) and, to a lesser extent, TNF-alpha (147 +/- 56% vs. 112 +/- 20%, NS) in 1 compared with 2 DR MM pairs. We conclude that the 1 DR MM setting is associated with optimal IL-10 secretion and more efficient inhibition of IFN-gamma and TNF-alpha compared with the 2 DR MM configuration. Although promoting enhanced IFN-gamma and TNF-alpha release, introduction of an additional DR MM does not result in increased IL-10 production. These data indicating that the IL-10 regulatory feedback loop is more effective in 1 DR rather than complete DR incompatibility could have an impact on matching policies for planned transfusion.

Antibodies, Blocking↗