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PubMed2000

Determination of optimal radiation energy for different breast sizes using CT-simulator [correction of simulatior] in tangential breast irradiation.

BACKGROUND: The purpose of this study is to determine and recommend the optimal radiation source according to breast size for tangential irradiation in breast conserving therapy. METHODS: Twenty-eight patients treated at our department from January 1994 to January 1996 were studied. The dose distribution within the irradiated breast was calculated using a (60)Co-gamma ray and 6 MV-X ray. Then we compared 3-D dose distributions of the (60)Co-gamma ray and 6 MV-X ray in different-sized breasts. Three parameters (breast volume, chest wall separation, and breast height) were adopted as representative of breast size. We also examined correlations among the three parameters. RESULTS: When the breast size was large (breast volume >400 cm(3), chest wall separation > 19.5 cm, or breast height > 6.5 cm), the average volume of normal tissue which received more than 110% of the isocenter dose ("hot spot") was significantly greater with the (60)Co-gamma ray than with the 6 MV-X ray (p < 0.05). A similar result was obtained with regard to hot spots in the clinical target volume. The cold area that received less than 95% of the isocenter dose was greater using a 6 MV-X ray when the breast size was small (breast volume <200 cm(3), chest wall separation <17.5 cm, or breast height <5.0 cm). However, the difference was not significant. There was a significant correlation between breast volume and chest wall separation (r =0.849, p <0.001). Breast volume and breast height were also significantly correlated (r =0.813, p <0.001). CONCLUSIONS: Since breast volume and shape are different in each patient, the optimal energy should be selected for each case to obtain uniform dose distribution in breast-conserving therapy. Chest wall separation or breast height, which are measurable without a 3-D planning system, can substitute for breast volume as parameters for breast size. We recommend that the (60)Co-gamma ray not be used for treating large breasts, those with chest wall separation > or =19.5 cm or breast height > or =6.5 cm.

Anthropometry↗

PubMed2002

Global optimization by energy landscape paving.

We introduce a novel heuristic global optimization method, energy landscape paving (ELP), which combines core ideas from energy surface deformation and tabu search. In appropriate limits, ELP reduces to existing techniques. The approach is very general and flexible and is illustrated here on two protein folding problems. For these examples, the technique gives faster convergence to the global minimum than previous approaches.

Enkephalin, Methionine↗

PubMed1999

Gated TI-201 myocardial perfusion SPECT: application of energy window optimization.

PURPOSE: TI-201 scintigraphy is plagued with poor image quality because of the low-energy photons of TI-201 decay. Traditionally, a narrow 20% window centered on 71-72 keV has been used to improve sensitivity. Recent studies indicate that better imaging may be possible by optimizing the energy window to 34% centered on 77 keV. In this study, energy window optimization (EWO) was applied to gated TI-201 myocardial perfusion SPECT, and myocardial functional parameters were compared for gated TI-201 SPECT and gated Tc-99m sestamibi (Tc-99m MIBI) SPECT. METHODS: Count statistics for standard and optimal TI-201 myocardial scintigraphy were noted in 25 patients by assessing the total counts in a mid-ventricular slice of a rest-gated TI-201 myocardial SPECT study. The feasibility of performing functional studies with the application of EWO to TI-201 was assessed using the count statistics of a mid-ventricular slice of an optimized gated TI-201 SPECT study and a gated Tc-99m MIBI SPECT study. The functional parameters (ejection fraction, wall motion, and thickening) of TI-201 with EWO and Tc-99m MIBI were compared in 60 patients who underwent rest-gated TI-201 SPECT followed by poststress gated Tc-99m MIBI SPECT. The left ventricular ejection fraction was calculated using commercially available software, whereas wall thickness and motion were assessed by the consensus of two readers. RESULTS: The application of EWO increased available counts by more than 25%. It also resulted in sufficient counts being available to perform gated TI-201 SPECT without increasing acquisition times or the dose of TI-201. The average ejection fraction was 60.4% for gated TI-201 SPECT and 59.6% for gated Tc-99m MIBI SPECT (not significantly different). Overall, the image quality was rated excellent in 12% for TI-201 and Tc-99m MIBI and good in 50% and 62%, respectively, and poor in 38% and 26%, respectively. CONCLUSION: The application of EWO to TI-201 SPECT allows myocardial functional parameters to be assessed without having to increase the acquisition times or the administered dose of TI-201.

Adult↗

PubMedDate not supplied

Optimal photon energies with respect to absorbed dose for visualization of soft tissue masses with adipose tissue.

The photon energies which maximize the signal to noise ratio per unit absorbed dose (optimal photon energies) have been calculated for detection of soft tissue masses within adipose tissue 3--15 cm thick. The detection task simulates mammography in women with fatty breasts. Ideal, plain film and calcium tungstate screen-film systems were considered in the analysis. Net photographic density is not incorporated into this model; therefore, the optimal photon energy with respect to the signal to noise ratio per unit absorbed dose may not be the same as the photon energy which results in maximum film density per unit absorbed dose. Therefore, the model has limited applicability to film or screen-film systems. However, it is directly applicable to digital systems where brightness and contrast can be adjusted.

Adipose Tissue↗

PubMed1990

Diabetes and diet in pregnancy.

The mean additional energy requirement for pregnancy has been calculated at 285 kcal daily and it reflects the energy needs for production of the fetoplacental unit and for the maternal physiological adaptations to pregnancy. In practice there is considerable variation in energy requirement due to alterations in maternal energy expenditure. Optimal energy intakes are dictated also by the pre-pregnancy maternal weight. The outcome of pregnancy is improved in the underweight mother by an intake which produces a weight gain in pregnancy of approximately 14 kg, whereas a rise of only 7 kg may be optimal for the obese mother. Obesity with or without diabetes is associated with macrosomia and other problems and it is sensible to attempt to limit weight gain in pregnancy at a time when maternal motivation is high. Diabetes in pregnancy may arise in patients with pre-existing NIDDM or IDDM, but more commonly it is diagnosed for the first time during pregnancy and it usually disappears after delivery (gestational diabetes). Recent evidence suggests that gestational diabetes has a strong genetic component and is usually NIDDM precipitated early in life by the pregnancy. Both gestational diabetes and NIDDM are characterized by insulin deficiency and by insulin resistance. Long-term follow-up studies have demonstrated that NIDDM or impaired glucose tolerance develop in later life in 50-70% of women with previous gestational diabetes. The adverse effects of pregnancy on the mother with pre-existing diabetes may be minimized by good diabetic control as may be adverse effects on the fetus and neonate of diabetes in the mother. An increased incidence of fetal malformations persists in pregnancies with pre-existing maternal diabetes. Diabetes of any form may be associated with neonatal hypoglycaemia. The aim of therapy is to produce maternal normoglycaemia throughout pregnancy by dietary measures and insulin treatment if required. Women with pre-existing diabetes should tighten their blood glucose control from before conception. Optimization of insulin therapy and diet are required for IDDM and most NIDDM women will require insulin treatment in pregnancy. Gestational diabetics require diet and possibly insulin. Most pregnancies now proceed to term.

Birth Weight↗

PubMed1991

[Experimental studies on argon laser angioplasty].

To evaluate the safety and efficacy of recanalization of the occlusive arterial diseases by Argon laser, we investigated the effects of the laser irradiation using bare-ended probe (BEP) and metal-tip probe (MTP) on human cadaveric aorta and canine femoral arteries with thrombotic occlusion. In case of the BEP, the incidence of perforation of the arterial wall was high as compared with the MTP. However, laser angioplasty with angioscopic guidance could reduce the perforation rate, and made it possible to observe the new channel recanalized by laser. In case of the MTP, it was confirmed that the smaller MTP showed higher tip temperature and was more effective on plaques under the same laser energy. Optimal laser energy for single ablation was from 15J to 25J in case of 2.0mm tip and from 30J to 40J in case of 2.5mm tip. Application of the MTP equipped with thermal feedback control system could avoid the excessive thermal damage in comparison with the conventional MTP. It was considered that optimal temperature of the MTP equipped with thermal feedback control system ranged between 200 degrees C and 300 degrees C. It was concluded that laser angioplasty would be a useful treatment for the occlusive diseases of the peripheral arteries.

Angiography↗

PubMed1985

AMP deaminase reaction as a control system of glycolysis in yeast. Role of ammonium ion in the interaction of phosphofructokinase and pyruvate kinase activity with the adenylate energy charge.

The role of ammonium ion and AMP deaminase (EC 3.5.4.6) reaction in the activation of phosphofructokinase (EC 2.7.1.11) and pyruvate kinase (EC 2.7.1.40) by the decrease in the adenylate energy charge was investigated using permeabilized yeast cells. Response of AMP deaminase, phosphofructokinase, and pyruvate kinase to variation in the energy charge is typical of the ATP-regenerating enzymes: an activation with the decrease in the energy charge under the in situ conditions. The addition of polyamine activated AMP deaminase in situ, resulting in the subsequent increase in ammonium production, which can stimulate the phosphofructokinase activity with the increase in the optimal energy charge value giving maximal activity of the enzyme. The optimal energy charge value of phosphofructokinase was 0.2-0.25 in the absence of ammonium ion and was shifted to the value above 0.5 by the addition of ammonium ion, whereas Pi, an activator of the enzyme showed little effect on the increase in the optimal energy charge value. The optimal energy charge value of AMP deaminase and pyruvate kinase was not affected by the addition of their effectors. Modulation of the response to the energy charge of phosphofructokinase and pyruvate kinase was analyzed in terms of the "activation coefficient," which was defined as the ratio of the activity at the energy charge of 0.6 to that at the value of 0.9. Activation of phosphofructokinase by the physiological decrease in the energy charge (0.9 to 0.6) can be enhanced by the increase in ammonium ion specifically, although the coefficient of pyruvate kinase remained unaffected by ammonium ion. These results suggest that the AMP deaminase reaction as an ammonium-forming reaction can participate in a key role in the stimulation of phosphofructokinase or glycolytic flux in cells.

AMP Deaminase↗

PubMedDate not supplied

[Evolution of life cycle: models based on optimization of energy allocation].

A brief history of optimization approach in modern evolutionary ecology is given and author's own results concerning life history evolution are considered in more details. The problem of evolutionary optimization is formulated in terms of mathematical theory of optimal control as a problem of optimal sharing of organism's resources between growth, reproduction, repair, and maintenance. The Malthusian parameter is used as optimality criterion. This approach allows, in particular, to give evolutionary ecological explanations for some well known empirical facts such as attenuation of growth with age (law of Bertalanffi), acceleration of ageing with age (law of Gompertz), human sexual dimorphism in mean lifespan, age and size of maturity.

Aging↗

PubMed1996

Thermoregulation in homeotherms: central temperature results from optimization of energy transfers.

In contrast to the classical homeostatic concept of the constancy of the central temperature, this study proposes an original model of thermoregulation based on the optimization of energy transfers. Exchange of the energy consumed or produced by the cell between the cell and the external medium has an associated energy cost. The different variables of the internal medium-flows, pressures, concentrations and also temperatures, since heat is but a particular form of energy--are continuously set at optimal values such that this cost is always minimal for the prevailing constraints with which the organism is faced. The proposed thermoregulatory model accounts for the physiological spatial and temporal variability of the body's temperatures. The predictive curves suggest a new approach to experimental studies concerned with thermal regulation and throw new light on their results.

Animals↗

PubMed2000

Density functional geometry optimization and energy calculations of calcium(II)-triphosphate complexes. Polyphosphates as possible dissolving agents for calcium pyrophosphate dihydrate crystals in chondrocalcinosis disease.

Geometry optimizations and energy calculations have been carried out via molecular orbital methods at the density functional B3LYP/LANL2DZ level on the molecules PO3-, OPO3(3-), HOPO3(2-), CH3OPO3(2-), H(CH3OPO3)-, O(PO3)2(4-), HO(PO3)2(3-), CH2(PO3)2(4-), (CH3OPO2)O(PO3)3-, O(PO3)3(5-), HO(PO3)3(4-), (PO3)3(3-), (CH3OPO2)O(PO3)2(4-), [Mg[O(PO3)2)]]2-, [Ca[O(PO3)2]]2-, [Ca[CH2(PO3)2]]2-, [Ca[CH3OPO2)O(PO3)]]-, [Ca(PO3)3]-, [Ca[O(PO3)3]]3-, and [Ca[CH3OPO2)O(PO3)2]]2- with the aim to find reliable and easily accessible computational methods to simulate some phosphate-containing molecules of importance for the living cells and to study the energetics for protonation and metal-complex formation reactions. The analysis is part of a general investigation on phosphate-containing molecules as potential dissolving agents for calcium pyrophosphate dihydrate (CPPD) crystals which deposit in certain articular diseases. The basis set was expanded to 6-31G** for the P atoms for all the molecules investigated and to 6-31G* for the O atoms for OPO3(3-). Calculations at the semiempirical MNDO/d level were also carried out for comparison purposes on the free ligand molecules and on [Mg[O(PO3)2]]2-. The density functional analysis reproduced well the geometry found at the solid state via X-ray diffraction. The analyses of the geometrical parameters and the total electronic energy of the molecules shows that O(PO3)2(4-) and other di- and tri-phosphates are versatile ligands for divalent metal ions like Ca2+. The computed P-O-P bond angle for free O(PO3)2(4-) is 180 degrees and the conformation of the two PO3- groupings is staggered along the P...P vector. The linear arrangement for P-O-P is assisted by P-O pi interactions. The bending of the P-O-P angle when accompanied by a slight P-O(b) elongation requires a very small amount of energy; 4.65 kcal/mol to pass from 180 to 140 degrees , as calculated at the DFT level. The computed Ca-O and Mg-O bond distances for [M[O(PO3)2]]2- are 2.378 and 2.079A, when the metal ions link two oxygen atoms from each PO3 group. The computed Ca-O bond lengths for [Ca[CH3OPO2)O(PO3)]]- are 2.482 (PalphaO2) and 2.358A (PbetaO2), showing a significant lengthening for Ca-OPalpha, when compared to the pyrophosphate derivative. The Ca-O bond lengths for [Ca[O(PO3)3]]3- and [Ca[CH3OPO2)O(PO3)2]]2- are 2.251A and 2.525 (PalphaO2), 2.407 and 2.338 (PbetaO2), and 2.251 and 2.228A (PgammaO2), showing a shortening for the Ca-OPgamma bond upon methylation. The (Pbeta)O-Pgamma bond length increases significantly (0.09 A) upon Ca(II) coordination to (CH3OPO2)O(PO3)2(4-) via all the three PO3 groups. This latter result suggests that metal complexes of linear organic-triphosphates have a larger tendency to release the PgammaO3 group when compared to the free ligand molecules. The electronic contribution to the energy of the complex formation reaction for [Ca[CH2(PO3)2]]2- is only slightly higher (some 1.8 kcal) than that for [Ca[O(PO3)2]]2-; but is much higher (some 63 kcal) than that relevant to the formation of [Ca[CH3OPO2)O(PO3)2]]2-. (ABSTRACT TRUNCATED)

Calcium Phosphates↗

PubMed2006

Three-dimensional positron emission tomography imaging with 124I and 86Y.

BACKGROUND: Impure positron emitters have physical characteristics that degrade image quality compared to conventional positron emitters like 18F. Two impure positron emitters with potentially interesting applications are 124I and 86Y. The degradation in image quality due to the imperfection of these isotopes is quantified for a human three-dimensional (3-D) positron emission tomography (PET) system. An acquisition protocol to obtain similar image quality as for 18F imaging is determined by Monte Carlo simulations. METHODS: The effects of larger positron range, associated singles and the other decay modes on image quality are determined by extensive Monte Carlo simulations of the Allegro scanner. Spatial resolution was evaluated for both isotopes and compared to spatial resolution of 18F. The loss in sensitivity due to triple coincidences was determined as a function of the axial acceptance angle of the PET scanner. The performance of the scanner at low count rates was studied by determining the noise equivalent count (NEC) values for different upper energy thresholds. The image degrading effect of spurious coincidences is taken into account by adding another factor to the NEC calculation. This allowed the contribution of spurious coincidences to be minimized by using a setting for the appropriate energy window. For this optimal energy window the amount of spurious and scattered coincidences was quantified. Simulations of count rate performance were also done to determine the peak NEC and the activity at which the maximum occurred. RESULTS: Spatial resolution degradation, compared to 18F, is about 0.5 mm for 86Y and 1 mm for 124I. Associated singles have a similar effect as scattered coincidences, as they also add a background to the image. The effect, however, is less important than the effect of scatter. The fraction of triple coincidences is quite small for a 3-D PET scanner used for humans as the axial acceptance angle is still moderate. For the Allegro with an energy resolution of 18% the optimal upper energy threshold was determined at 600 keV. For 124I this leads to 2.5% extra contamination that needs to be added to the scatter fraction. For 86Y this fraction is about 5.5%. CONCLUSION: 3-D PET images of 124I and 86Y have lower spatial resolution. For PET scanners used for humans the difference is not as important as for scanners used for animals. The limited positron decay fraction of both isotopes can be compensated by increasing the imaging time by a factor of 3-5 (same activity). A short coincidence window limits the contamination from other decay modes. Good energy resolution allows setting a selective upper energy threshold to limit the effect of spurious coincidences. With an appropriate setting of the energy window it should be possible to obtain good image quality in a relatively short time because of the high sensitivity of 3-D PET scanners.

Equipment Design↗

PubMed1983

Role of AMP deaminase reaction in the response of phosphofructokinase to the adenylate energy charge.

The role of NH+4 ion and AMP deaminase reaction in the activation of phosphofructokinase with respect to its response to the adenylate energy charge was investigated using permeabilized yeast cells. (a) Phosphofructokinase and AMP deaminase were activated by the decrease in the adenylate energy charge. The addition of NH+4 further stimulated the phosphofructokinase activity in the presence of intracellular level of K+, and the optimal energy charge value giving the maximal response of the enzyme was shifted from 0.3 to the value above 0.5. (b) The increase in NH+4 ion produced through the activation of AMP deaminase by spermine which shows no direct action on the phosphofructokinase activity can activate phosphofructokinase with shift of the optimal energy charge value of the enzyme to 0.5 in the presence of K+, whereas the optimal energy charge value for AMP deaminase reaction was not affected by the addition of spermine. Phosphofructokinase can be activated most effectively by the physiological decrease in the energy charge under the condition of increased NH+4 in the presence of K+. The possibility that the interaction of phosphofructokinase with AMP deaminase under hypoxic condition might be a contributing factor to the Pasteur effect is discussed.

AMP Deaminase↗

PubMed2003

MOPED: method for optimizing physical energy parameters using decoys.

We present a method called MOPED for optimizing energetic and structural parameters in computational models, including all-atom energy functions, when native structures and decoys are given. The present method goes beyond previous approaches in treating energy functions that are nonlinear in the parameters and continuous in the degrees of freedom. We illustrate the method by improving solvation parameters in the energy function EEF1, which consists of the CHARMM19 polar hydrogen force field augmented by a Gaussian solvation term. Although the published parameters for EEF1 correctly discriminate the native from decoys in the decoy sets of Levitt et al., they fail on several of the more difficult decoy sets of Baker et al. MOPED successfully finds improved parameters that allow EEF1 to discriminate native from decoy structures on all protein structures that do not have metals or prosthetic groups.

Algorithms↗

PubMedDate not supplied

The control of a parallel hybrid-electric propulsion system for a small unmanned aerial vehicle using a CMAC neural network.

A Simulink model, a propulsion energy optimization algorithm, and a CMAC controller were developed for a small parallel hybrid-electric unmanned aerial vehicle (UAV). The hybrid-electric UAV is intended for military, homeland security, and disaster-monitoring missions involving intelligence, surveillance, and reconnaissance (ISR). The Simulink model is a forward-facing simulation program used to test different control strategies. The flexible energy optimization algorithm for the propulsion system allows relative importance to be assigned between the use of gasoline, electricity, and recharging. A cerebellar model arithmetic computer (CMAC) neural network approximates the energy optimization results and is used to control the parallel hybrid-electric propulsion system. The hybrid-electric UAV with the CMAC controller uses 67.3% less energy than a two-stroke gasoline-powered UAV during a 1-h ISR mission and 37.8% less energy during a longer 3-h ISR mission.

Algorithms↗

PubMed2000

Optimization of energy coupling: what is all the argument about?

Although it may be asked how effective glycolysis is in retaining the chemical energy in the bonds of glucose during its breakdown in the formation of ATP, the reasons for the coupled pathway of glycolysis having evolved as it has are probably as much as a consequence of the need to find reactions that can lead to formation of phosphoryl groups able to transfer to ADP as to the overall thermodynamics of the pathway. It is not meaningful to talk of optimization of energy coupling solely in terms of free energy changes.

Journal Article↗

PubMedDate not supplied

Effect of diet and weight reduction in hypertension.

Weight reduction by a low-energy diet and a high-polyunsaturates-, fiber- and potassium-rich diet may be independently useful to hypertensives. To study the effect of such diets, 416 hypertensives were randomized to either a low-energy cardiovasoprotective (CVP) diet (Group A; n = 106), a low-energy usual diet (Group B; n = 104), an optimal-energy CVP diet (Group C; n = 104), or an optimal-energy, usual pre-experimental diet (Group D; n = 102) plus drug therapy in a single-blind and controlled fashion. Groups A and B received significant (p less than 0.02) fewer calories per day than Groups C and D. Groups A and C also received significantly (p less than 0.02) more calories per amount of complex carbohydrates, polyunsaturates, potassium, and magnesium than did Groups B and D. Dietary compliance and drug intake was checked weekly. After 3 months, there was a significant fall in mean serum cholesterol (p less than 0.01) and mean serum triglycerides (p less than 0.05) in Group A compared with Group D. Group A and B patients had a loss of around 10kg of mean body weight, with no weight change seen in Group D. Weight loss was associated with a significant fall in systolic and diastolic pressures in both Group A (22/18mmHg) and Group B (16/13mmHg) compared with Group D at the end of the study. Group C patients also showed a significant fall in pressure (13/10mmHg) compared with Group D. Drug therapy, exercise, and salt intake were similar in all the groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1998

Treating ischemic heart disease by pharmacologically improving cardiac energy metabolism.

An increasing number of clinical and experimental studies have shown that optimizing energy metabolism in the heart is an effective approach to decreasing the symptoms associated with myocardial ischemia. In particular, increasing myocardial glucose metabolism can benefit heart function and/or lessen tissue injury. However, high levels of circulating fatty acids will markedly decrease glucose metabolism in the heart. These high levels of fatty acids occur in most clinically relevant conditions of myocardial ischemia, and can contribute to the severity of ischemic injury. A number of pharmacologic agents are now available that directly stimulate myocardial glucose metabolism or indirectly stimulate glucose metabolism secondary to an inhibition of fatty acid metabolism. One agent that appears to act by this mechanism is trimetazidine, which we recently found stimulates glucose oxidation in isolated rat hearts perfused with high levels of fatty acids. Clinical studies have also shown that trimetazidine has cardioprotective effects in the setting of myocardial ischemia. As a result, optimizing energy metabolism with agents such as trimetazidine may have considerable promise as a new approach to treating cardiovascular disease.

Animals↗

PubMed2006

A simple multichromophore design for energy transfer in distyrylbenzenes with pyrene pendants.

A set of Don --> Acc <-- Don multichromophores was synthesized based on a simple design with two pyrene donors (absorbing antennae) connected to a bis-1,4-(3,4,5-trimethoxystyryl)benzene core acceptor using various flexible, nonconjugated tethers. Excitation of the pyrene donors at 276 nm in solution yields near exclusive emission from the core chromophore at 445-450 nm, with energy transfer efficiencies up to 92%, far better than achieved with simple mixtures. The simple tethering design imposes a high "local" concentration of the pyrene near the acceptor core unit that is maintained even at very low multichromophore concentrations. Solvent effects on absorption and emission spectra are very small, except in cases where a pi-conjugating O-C=O moiety of the tethering group is directly attached to the core chromophore, rather than being placed in the middle of the tether. Energy transfer in the systems is effective due to good donor-acceptor energy matching. The optimal energy transfer efficiency was achieved using an eight-atom flexible linker.

Journal Article↗