A finite element-based machine learning approach for modeling the mechanical behavior of the breast tissues under compression in real-time.

This work presents a data-driven method to simulate, in real-time, the biomechanical behavior of the breast tissues in some image-guided interventions such as biopsies or radiotherapy dose delivery as well as to speed up multimodal registration algorithms. Ten real breasts were used for this work. Their deformation due to the displacement of two compression plates was simulated off-line using the finite element (FE) method. Three machine learning models were trained with the data from those simulations. Then, they were used to predict in real-time the deformation of the breast tissues during the compression. The models were a decision tree and two tree-based ensemble methods (extremely randomized trees and random forest). Two different experimental setups were designed to validate and study the performance of these models under different conditions. The mean 3D Euclidean distance between nodes predicted by the models and those extracted from the FE simulations was calculated to assess the performance of the models in the validation set. The experiments proved that extremely randomized trees performed better than the other two models. The mean error committed by the three models in the prediction of the nodal displacements was under 2 mm, a threshold usually set for clinical applications. The time needed for breast compression prediction is sufficiently short to allow its use in real-time (<0.2 s).

Patient-specific simulation of the intrastromal ring segment implantation in corneas with keratoconus.

PURPOSE: The purpose of this study was the simulation of the implantation of intrastromal corneal-ring segments for patients with keratoconus. The aim of the study was the prediction of the corneal curvature recovery after this intervention. METHODS: Seven patients with keratoconus diagnosed and treated by implantation of intrastromal corneal-ring segments were enrolled in the study. The 3D geometry of the cornea of each patient was obtained from its specific topography and a hyperelastic model was assumed to characterize its mechanical behavior. To simulate the intervention, the intrastromal corneal-ring segments were modeled and placed at the same location at which they were placed in the surgery. The finite element method was then used to obtain a simulation of the deformation of the cornea after the ring segment insertion. Finally, the predicted curvature was compared with the real curvature after the intervention. RESULTS: The simulation of the ring segment insertion was validated comparing the curvature change with the data after the surgery. Results showed a flattening of the cornea which was in consonance with the real improvement of the corneal curvature. The mean difference obtained was of 0.74 mm using properties of healthy corneas. CONCLUSIONS: For the first time, a patient-specific model of the cornea has been used to predict the outcomes of the surgery after the intrastromal corneal-ring segments implantation in real patients.

Methodology based on genetic heuristics for in-vivo characterizing the patient-specific biomechanical behavior of the breast tissues.

This paper presents a novel methodology to in-vivo estimate the elastic constants of a constitutive model proposed to characterize the mechanical behavior of the breast tissues. An iterative search algorithm based on genetic heuristics was constructed to in-vivo estimate these parameters using only medical images, thus avoiding invasive measurements of the mechanical response of the breast tissues. For the first time, a combination of overlap and distance coefficients were used for the evaluation of the similarity between a deformed MRI of the breast and a simulation of that deformation. The methodology was validated using breast software phantoms for virtual clinical trials, compressed to mimic MRI-guided biopsies. The biomechanical model chosen to characterize the breast tissues was an anisotropic neo-Hookean hyperelastic model. Results from this analysis showed that the algorithm is able to find the elastic constants of the constitutive equations of the proposed model with a mean relative error of about 10%. Furthermore, the overlap between the reference deformation and the simulated deformation was of around 95% showing the good performance of the proposed methodology. This methodology can be easily extended to characterize the real biomechanical behavior of the breast tissues, which means a great novelty in the field of the simulation of the breast behavior for applications such as surgical planing, surgical guidance or cancer diagnosis. This reveals the impact and relevance of the presented work.

Cocaine-induced locomotor activity is enhanced by exogenous testosterone.

Anabolic-androgenic steroids are synthetic derivatives of testosterone, which are increasingly abused by adolescent populations who also abuse psychoactive substances. All these compounds lead to complex behavioral syndromes and the effects of their interactions remain unclear. The main aim of the present study was to determine the influence of testosterone on the locomotor activity-promoting effect of cocaine on male mice in an open field. In the three experiments, animals received two injections: firstly, testosterone or peanut oil, and secondly, cocaine or saline solution. In Experiments 1 and 2, testosterone (or oil) and cocaine (or saline) were injected 45 and 10 min, respectively, prior to activity recording. In the first experiment, we studied the effects of testosterone (2 mg/kg) on locomotor activity induced by different doses of cocaine (2, 4, 8, 10 or 12 mg/kg). In Experiment 2, we explored the effects of supraphysiological doses of testosterone (2, 6, 10 or 14 mg/kg) on animals treated with 10 mg/kg cocaine. Finally, in the third experiment, 14 mg/kg testosterone or vehicle was administered 15, 30, 45 or 75 min before activity data collection to animals that received 10 mg/kg cocaine or saline. Testosterone itself had no effects on spontaneous locomotor activity and, as was expected, cocaine increased locomotor activity dose-dependently. Given together, testosterone enhanced the cocaine-induced hyperactivity although not dose-dependently, the highest effects being found 45 min after testosterone injection. The present study confirmed the existence of an interaction between testosterone and cocaine at the central nervous system.

Psychophysiological responses to the Stroop Task after a maximal cycle ergometry in elite sportsmen and physically active subjects.

Physical fitness moderates the psychophysiological responses to stress. This study attempts to determine whether the degree of fitness could affect the response to physical and psychological stress after comparing two groups of men with good physical fitness. Saliva samples from 18 elite sportsmen, and 11 physically active subjects were collected to determine hormonal levels after carrying out a maximal cycle ergometry. Heart rate and skin conductance level were continuously recorded before, during, and after a modified version of the Stroop Color-Word Task. With similar scores in trait anxiety and mood, elite sportsmen had lower basal salivary testosterone, testosterone/cortisol ratio, and HR before an ergometric session than physically active subjects, but no differences were found in salivary cortisol and blood pressure. Salivary testosterone and cortisol responses were lower and testosterone/cortisol ratio responses higher in elite sportsmen. During the Stroop Task, elite subjects showed lower heart rate and skin conductance level over the entire measurement period, and greater heart rate recovery with respect to the baseline values than physically active subjects. The effects of two standardised laboratory stressors on a set of psychophysiological variables were different when elite sportsmen and physically active subjects were compared.

Rewarding properties of testosterone in intact male mice: a pilot study.

The present study examined the rewarding properties of 4-androsten-17beta-ol-3-one testosterone in intact male mice using the conditioned place preference (CPP) technique. In Experiment 1, the pharmacokinetics of 0.8 and 1.2 mg/kg of testosterone were studied to determine the most appropriate temporal interval to test behavior. Additionally, the locomotor activity was recorded to control a possible interfering effect on CPP. The maximum testosterone concentration was registered at 45 min of administration, and no effects on activity were found. In Experiment 2, three groups of male OF-1 mice received four pairings of the least-preferred compartment with testosterone (0.8, 1, or 1.2 mg/kg, SC) for 30 min. On alternate days the preferred compartment was paired with vehicle for 30 min. The control group received vehicle in both compartments. No significant differences between groups were found in the time spent in the drug-paired compartment. However, when separate analyses were performed in conjunction with the color of the drug-paired compartment. CPP was observed only in animals pairing testosterone/black compartment. These results suggest that rewarding properties of testosterone treatment can be observed in male mice; these effects probably being dependent on the environmental cues used as conditioned stimuli.

Effects of competition and its outcome on serum testosterone, cortisol and prolactin.

In various species, competitive encounters influence hormonal responses in a different way depending on their outcome, victory or defeat. This study aimed to investigate the effects of sports competition and its outcome on hormonal response, comparing it with those displayed in situations involving non-effort and non-competitive effort. To this end, serum testosterone (T), cortisol (C) and prolactin (PRL) were measured in 26 judoists who participated in three sessions (control, judo fight and ergometry). The relationship between hormonal changes and psychological variables before and after the fight were also analysed. Our results showed a hormonal response to competition, which was especially characterized by an anticipatory rise of T and C. Depending on outcome, significant higher C levels were found in winners in comparison to losers through all the competition but not in T or PRL, both groups expending a similar physical effort. Furthermore, similar hormonal responses to the fight and to a non-competitive effort with the same caloric cost were found, other than with PRL. Winners showed a higher appraisal of their performance and satisfaction with the outcome, and perceived themselves as having more ability to win than losers, although there were no significant differences in motivation to win. Finally, the relationships found between T changes in competition and motivation to win, as well as between C response and self-efficacy suggest that in humans hormonal response to competition is not a direct consequence of winning and losing but rather is mediated by complex psychological processes.

Lack of effects of anabolic-androgenic steroids on locomotor activity in intact male mice.

Anabolic-androgenic steroid abusers have reported hyperactivity, euphoria, and decreased fatigue, among other behavioral effects. It has been suggested that the effects of these substances on the central nervous system are similar to those of psychostimulants; however, the influence of steroids on general locomotor activity in laboratory animals is not well understood, especially how noncastrated male rodents are affected. In this study, spontaneous locomotor activity displayed by gonadally intact male mice submitted to several experimental conditions was analyzed. Different housing conditions (individual or cohabiting with a female), diverse steroids (testosterone propionate, nandrolone decanoate, and a mixture of both steroids) and single or repeated injections were employed. At 24 hours after the injection (after the three last injections in the case of chronic treatment) spontaneous locomotor activity was registered on an activity recorder for one 15-min. period. No effects due to the treatment were found in almost every experimental condition. These results contrast with the dramatic decreases in activity described for female mice after treatment with such steroids. It seems that in intact males the steroids' influence on spontaneous locomotor activity may be more subtle than expected. These effects seem very complex depending on duration of treatment and specific situations (spontaneous or forced activity) as well as the interaction with endogenous androgen levels.

Correlating testosterone and fighting in male participants in judo contests.

The role of hormones in human aggression is open to debate, but takes on a new urgency owing to the alarming abuse of androgenic anabolic steroids by some sports participants. In this study, video-taped behavior exhibited by 28 male competitors during a judo fight was assessed to analyze its relation to serum testosterone and cortisol levels measured before and after the bouts. A positive relation between testosterone and offensive behaviors was obtained in the sense that the greater the hormonal titer, the greater the number of threats, fights, and attacks. These findings coincide with the pattern of relationships found using observational scales. Conversely, cortisol also presented positive correlations with some of these behavioral categories but did not moderate the relationship between testosterone and competitive behavior. The present results corroborate and extend earlier findings on the role of these hormones in human behavior, giving support to the view that testosterone can be linked to the expression of competitive aggression.

Effects of chronic treatment with testosterone propionate on aggression and hormonal levels in intact male mice.

Effects of testosterone propionate, an anabolic-androgenic steroid (AAS), on aggression in gonadally intact male mice were examined. Animals were given weekly injections of 3.75, 7.5, 15, and 30 mg/kg of drug or sesame oil for 10 weeks. During the last 3 weeks, behavioral tests were conducted and at the end of the experiment, body, liver and testes weight and hormonal data were collected. The treatment had minimal behavioral and endocrine effects. It resulted in shorter latencies of 'threat' only in the last agonistic encounter, increases in testosterone levels and decreases in testes weight in a non-linear dose-dependant way. The action of treatment was different on threat and attack, the latter being unaffected. The behavioral effects in the total sample were only found in aggressive animals selected on the basis of their latency of attack in the first encounter.

Long-term chronic treatment with stanozolol lacks significant effects on aggression and activity in young and adult male laboratory mice.

1. Repeated doses of the anabolic-androgenic steroid stanozolol were assessed for their effects on agonistic behavior, motor activity, and body weight in both young and adult male laboratory mice. 2. Stanozolol significantly increased weight gain in young, but not older subjects, especially at the highest doses. 3. There were, however, no significant differences in motor activity or in ethologically assessed social behavior (including aggression) in young or adult mice.