An Optimized Method for Evaluating the Potential Gd-Nanoparticle Dose Enhancement Produced by Electronic Brachytherapy.

This work reports an optimized method to experimentally quantify the Gd-nanoparticle dose enhancement generated by electronic brachytherapy. The dose enhancement was evaluated considering energy beams of 50 kVp and 70 kVp, determining the Gd-nanoparticle concentration ranges that would optimize the process for each energy. The evaluation was performed using delaminated radiochromic films and a Poly(methyl methacrylate) (PMMA) phantom covered on one side by a thin 2.5 µm Mylar filter acting as an interface between the region with Gd suspension and the radiosensitive film substrate. The results for the 70 kVp beam quality showed dose increments of 6±6%, 22±7%, and 9±7% at different concentrations of 10, 20, and 30 mg/mL, respectively, verifying the competitive mechanisms of enhancement and attenuation. For the 50 kVp beam quality, no increase in dose was recorded for the concentrations studied, indicating that the major contribution to enhancement is from the K-edge interaction. In order to separate the contributions of attenuation and enhancement to the total dose, measurements were replicated with a 12 µm Mylar filter, obtaining a dose enhancement attributable to the K-edge of 29±7% and 34±7% at 20 and 30 mg/mL, respectively, evidencing a significant additional dose proportional to the Gd concentration.

A Novel Method for Surface Exploration by 6-DOF Encountered-Type Haptic Display Towards Virtual Palpation.

Surface exploration in virtual reality has a large potential to enrich the user's experience. It could for example be used to train and simulate medical palpation. During palpation, users tap, indent, and rub the surface of a sample to estimate the underlying properties. However, up to now there is no good approach to render such intricate interaction realistically. This paper introduces 6 degrees of freedom (DoF) encountered-type haptic display technology for simulating surface exploration tasks. Among the different phases of exploration, this article focuses on the 'in-contact sliding' phase. Two novel control approaches to render sliding over a virtual surface are elaborated. A first rendering method generates lateral frictional forces as the finger slides over the surface. A second method adjusts the inclination of the end-effector to render tissue properties. With both methods a stiff nodule embedded in a soft tissue was prepared. User experiments were carried out to find proper parameter and intensity ranges and to confirm the feasibility of the new rendering schemes. Participants indicated that both rendering schemes felt realistic. Compared to earlier work, where only the vertical stiffness was altered, lower thresholds to detect and localise embedded virtual nodules were found. Users also made fewer errors in detecting nodule edges. Furthermore, the method that used end-effector inclination allowed faster discovery of the nodule's edges. It is expected that approaches that combine both rendering methods could provide an even more realistic feel.

Evaluation of Haptic Feedback on Bimanually Teleoperated Laparoscopy for Endometriosis Surgery.

Robotic minimal invasive surgery is gaining acceptance in surgical care. In contrast with the appreciated three-dimensional vision and enhanced dexterity, haptic feedback is not offered. For this reason, robotics is not considered beneficial for delicate interventions such as the endometriosis. Overall, haptic feedback remains debatable and yet unproven except for some simple scenarios such as fundamentals of laparoscopic surgery exercises. OBJECTIVE: This work investigates the benefits of haptic feedback on more complex surgical gestures, manipulating delicate tissue through coordination between multiple instruments. METHODS: A new training exercise, "endometriosis surgery exercise" (ESE) has been devised approximating the setting for monocular robotic endometriosis treatment. A bimanual bilateral teleoperation setup was designed for laparoscopic laser surgery. Haptic guidance and haptic feedback are, respectively, offered to the operator. User experiments have been conducted to assess the validity of ESE and examine possible advantages of haptic technology during execution of bimanual surgery. RESULTS: Content and face validity of ESE were established by participating surgeons. Surgeons suggested ESE also as a mean to train lasering skills, and interaction forces on endometriotic tissue were found to be significantly lower when a bilateral controller is used. Collisions between instruments and the environment were less frequent and so were situations marked as potentially dangerous. CONCLUSION: This study provides some promising results suggesting that haptics may offer a distinct advantage in complex robotic interventions were fragile tissue is manipulated. SIGNIFICANCE: Patients need to know whether it should be incorporated. Improved understanding of the value of haptics is important as current commercial surgical robots are widely used but do not offer haptics.

Predictors of pulmonary hypertension in patients with end-stage heart failure.

Pulmonary hypertension (PH) is associated with a greater mortality rate in patients with heart failure (HF) and it is a risk factor for right ventricular failure after heart transplantation. This study was designed to explore risk factors for PH development in patients with advanced heart failure and left ventricular dysfunction. In a retrospective observational study of 419 patients evaluated for heart transplantation due to end stage HF, different variables were analyzed to find predictors of PH (defined as a mean pulmonary pressure >25 mmHg), reactive PH (defined as a transpulmonary gradient >12 mmHg) and severe PH (defined as a mean pulmonary pressure >40 mmHg and/or pulmonary vascular ressistance >3 WU) using a multivariate stepwise logistic regression analysis. Prevalence of PH, out of proportion and severe PH was 62.2%, 23.8%, and 18.8% respectively. The presence of moderate-severe mitral regurgitation [2.1 (1.2-3.7); P=0.006], moderate-severe tricuspid regurgitation [OR 2.9 (1.3-6.4); P=0.005] and a duration of disease >3 years [OR 1.7 (1.1-2.7); P=0.03] were independent risk factors associated with PH. Moreover, the presence of a moderate-severe mitral regurgitation and a duration of disease greater than 3 years, were independent predictors of out of proportion and severe PH.

Initial accuracy of bedside ultrasound performed by emergency physicians for multiple indications after a short training period.

PURPOSES: Emergency physician-performed ultrasonography holds promise as a rapid and accurate method to diagnose multiple diseases in the emergency department (ED). Our objective was to assess the initial diagnostic accuracy (first 55 explorations) of emergency physician-performed ultrasonography for multiple categories of ultrasound use after a short training period. BASIC PROCEDURES: This was a prospective observational study conducted at an urban ED from June 2010 to March 2011 in patients with suspected cholecystitis, hydronephrosis, deep vein thrombosis, and different cardiovascular problems. Five physicians had a 10-hour training session before enrolling patients. The test characteristics of bedside ultrasonography were determined with the final radiologist/cardiologist interpretation. MAIN FINDINGS: A total of 275 ultrasonographic examinations were performed (78 abdominal explorations, 80 renal explorations, 76 2-point compression ultrasonographic examinations in patients with suspected deep vein thrombosis, and 41 echocardiograms in patients with different acute cardiovascular problems). Radiologists/cardiologists detected 28 cases of cholecystitis, 26 cases of deep vein thrombosis, 49 cases of hydronephrosis, and 15 cases of significant cardiovascular alterations. The overall diagnostic accuracy of ED ultrasonograms yielded a sensitivity, specificity, positive predictive value, and negative predictive value of 92.6% (95% confidence interval [CI], 90%-99%), 89% (95% CI, 84%-94%), 86.2 % (95% CI, 82%-93%), and 94.2% (95% CI, 92%-99%), respectively. Nineteen (6.9%) false-positive results and 6 false-negative results (2.1%) were obtained. PRINCIPAL CONCLUSIONS: Emergency physicians in our institution attained reasonably high initial accuracy in the performance of ultrasonography for a variety of clinical problems after a 10-hour training period.

Outcomes of atherothrombotic transient ischemic attack and minor stroke in an emergency department: results of an outpatient management program.

STUDY OBJECTIVE: Management of patients with transient ischemic attack varies widely. The aim of this study is to analyze the outcomes of patients with transient ischemic attacks or minor stroke managed in the emergency department (ED) on an outpatient basis and to identify risk factors associated with stroke recurrence. METHODS: We prospectively analyzed 97 patients with transient ischemic attack or minor stroke who were treated with a standard diagnostic and therapeutic protocol in the ED by emergency physicians. Factors in previous reports were analyzed in relation with a new neurologic event at 90 days or the presence of a severe extracranial carotid stenosis. RESULTS: Incidence of recurrent transient ischemic attack or stroke was 7.2% at 24 hours, 9.3 % at 1 week, and 23.7 % at 3 months. Overall incidence of moderate to severe stroke was 0%, 1%, and 5% at the same points, and in outpatients was 0%, 0%, and 4.2%. ABCD2 scoring in these patients predicted stroke rates of 6% at 7 days and 9.9% at 90 days. CONCLUSION: Patients with transient ischemic attack of atherothrombotic origin can be safely treated at the ED with an exhaustive diagnostic and therapeutic protocol. The rates of stroke recurrence obtained in our study are comparable with those in previous studies that show low recurrence risk.

Re-entrant nematic behavior in the 7OCB+9OCB mixtures: evidence for multiple nematic-smectic tricritical points.

The metastable phase diagram of the two-component system heptyloxycyanobiphenyl (7OCB)+nonyloxycyanobiphenyl (9OCB) was determined by means of modulated differential scanning calorimetry (MDSC) and optical microscopy measurements. It was experimentally established that the 7OCB+9OCB two-component system exhibits a monotropic re-entrant nematic behavior. A complete quantitative thermodynamic analysis, through Oonk's equal G analysis, was performed, allowing for the calculation of the monotropic re-entrant behavior and the prediction of two tricritical points, one of them experimentally accessible for the SmAd-to-N transition and the other non-experimentally accessible for the RN-to-SmAd transition. From specific-heat measurements, latent heats were obtained for those mixtures displaying a first-order SmAd-to-N transition. Additionally, for some mixtures, the specific-heat critical exponents (alpha), through the second-order SmAd-to-N transition, were obtained. Both batches of data enable us to access to the experimental tricritical temperature for the SmAd-to-N transition.

Liquid crystal binary mixtures of 8OCB + 10OCB. Evidence for a smectic A-to-nematic tricritical point.

The two-component system octyloxycyanobiphenyl (8OCB) + decyloxycyanobiphenil (10OCB) has been studied by means of modulated differential scanning calorimetry as well as optical microscopy. The general trends of the phase diagram are similar to the two-component system octylcyanobiphenyl (8CB) + decylcyanobiphenil (10CB), previously published. Evidence for the existence of a TCP have been reported, the molar composition being about 0.33 of 10OCB. Additionally, the smectic mesophase of the 8OCB + 10OCB mixtures has been unmistakably characterized through optical measurements as smectic A for the whole composition range.

Analysis and evaluation of periodic physiological organ motion in radiotherapy treatments.

BACKGROUND AND PURPOSE: A system for the detection, measurement and analysis of the periodic physiological organ motion during radiotherapy treatment is proposed and clinically tested in this paper. MATERIAL AND METHODS: The procedure is based on the acquisition of fluoroscopic sequences, followed by an automatic detection of the movement using cross-correlations with matched filters. RESULTS: The system generates a probability density function (PDF) of finding a mobile organ in a position at a certain time. The maximum path of the mobile structures can be determined to define the planning target volume (PTV) without ambiguities. CONCLUSIONS: Physiological movements can be accurately included in the daily planning routine, which is not essentially modified, without needing previous patient training.

Células troncales en neurología / Stem Cells in neurology

Las investigaciones sobre células troncales han concitado creciente actividad en el campo de la investigación y publicaciones científicas. Nuestra revisión de la literatura expone qué es una célula troncal, sus propiedades, algunas de las estrategias para aislar y hacer proliferar células troncales neurales y los mecanismos moleculares involucrados en la integración funcional de estas células al cerebro receptor. Finalmente se comentan los posibles pasos de las futuras investigaciones, las que deberán identificar mejor las señales del receptor a las células donantes, así como descifrar con mayor profundidad la capacidad neurogénica del ambiente celular del cerebro adulto.