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Laser Ablation (LA) is a minimally-invasive procedure for tumor treatment. LA outcomes depend on the heat distribution inside tissues and require accurate temperature measurement during the procedure. Magnetic resonance imaging (MRI) allows a non-invasive and three-dimensional thermometry of the organ undergoing LA. In this study, the temperature distribution within two swine pancreases and three swine livers undergoing LA (Nd:YAG, power: 2 W, treatment time: 4 min) was monitored by a 1.5-T MR scanner, utilizing two T 1 -weighted sequences (IRTF and SRTF). The signal intensity in four regions of interest, placed at different distances from the laser applicator, was related to temperature variations monitored in the same regions by twelve fiber Bragg grating sensors. The relationship between the signal intensity and temperature increase was calculated to obtain the calibration curve and to evaluate accuracy, sensibility and precision of each sequence. This is the first study of MR-based thermometry during LA on pancreas. More specifically, the IRTF sequence provides the highest temperature sensitivity in both liver (1.8 ± 0.2 °C −1 ) and pancreas (1.8 ± 0.5 °C −1 ) and the lowest precision and accuracy. SRTF sequence on pancreas presents the highest accuracy and precision (MOD SFRT = −0.1 °C and LOA SFRT = [−2.3; 2.1] °C). [ABSTRACT FROM AUTHOR]

Laser interstitial thermotherapy (LITT) is employed to destroy tumors in organs, and its outcome strongly depends on the temperature distribution inside the treated tissue. The recent introduction of computed tomography (CT) scan thermometry, based on the CT number dependence of the tissue with temperature, overcomes the invasiveness of other techniques used to monitor temperature during LITT. The averaged CT number (ROI = 0.02 cm²) of an ex vivo swine pancreas is monitored during LITT (Nd:YAG laser power of 3W, treatment time: 120 s) at different distances from the applicator (from 4 to 30 mm). The averaged CT number shows a clear decrease during treatment: it is highest at 4 mm from the applicator (mean variation in the whole treatment of -0.256 HU s-1) and negligible at 30 mm, since the highest temperature increase is present close to the applicator (i.e., 45 °Cat 4 mm and 25 °Cat 6 mm). To obtain the relationship between CT numbers and pancreas temperature, the reference temperature was measured by 12 fiber Bragg grating sensors. The CT number decreases as a function of temperature, showing a nonlinear trend with a mean thermal sensitivity of -0.50 HU °C-1. Results here reported are the first assessment of pancreatic CT number dependence on temperature, at the best of our knowledge. Findings can be useful to further investigate CT scan thermometry during LITT on the pancreas. [ABSTRACT FROM AUTHOR]

Heated wire humidifiers (HWHs) are widely used to heat and humidify gases during mechanical ventilation. The control strategy implemented on commercial HWHs, based on maintaining constant gas temperature at the chamber outlet, shows weaknesses: humidifying performances depend on environmental temperature and ventilatory settings, and often condensation occurs. Herein, we analyzed in vitro HWH performances focusing on the condensation amount according to ventilatory settings. We used a physical model to define the parameters which mainly influence the HWH performances. In order to investigate the influence of minute volume (MV) and frequency rate (fr) on condensation, the other influencing parameters were kept constant during experiments, and we introduced a novel approach to estimate the condensation. The method, based on measuring the condensed vapor mass (Δm), provided more objective information than the visual-based scale used in previous studies. Thanks to both the control of other influencing factors and the accurate Δm measures, the investigation showed the Δm increase with MV and fr. Substantial condensation after 7 h of ventilation and the influence of MV and fr on Δm (i.e., Δm = 3 g at MV = 1.5 L min−1 and fr = 8 bpm and Δm = 9.4 g at MV = 8 L min−1 and fr = 20 bpm) confirm the weaknesses of `single-point temperature' control strategies. [ABSTRACT FROM AUTHOR]

Controlling thermo-hygrometric conditions of gas delivered in neonatal mechanical ventilation shows some unresolved issues due to the design and control strategies implemented in heated wire humidifiers. We perform an in vitro evaluation of humidifier performances, which use a control strategy based on a single-point temperature as feedback, and propose a novel design of the control which consists in pre-warming the gas upwards in the humidification chamber. The ad hoc developed control approach based on a theoretical model is implemented in vitro with and without pre-warming for comparative purposes. Without pre-warming, gas at the chamber outlet needs further post-warming and, depending on the flow rate, the vapour content condensates along the breathing circuit. Whereas, with pre-warming, the proposed control strategy allows us to considerably improve steady-state thermo-hygrometric conditions (T = 37 ± 1 °C, RH = 96% ± 4%) of gas, reaching the Y-piece near to ideal ones in the whole flow rate range, even though a high inlet chamber temperature is required at low flow rate values. The proposed solution, as theoretically predicted, also allows us to limit the vapour condensation along the circuit. [ABSTRACT FROM AUTHOR]

Objective: We implement a data assimilation Bayesian framework for the reconstruction of the spatiotemporal profile of the tissue temperature during laser irradiation. The predictions of a physical model simulating the heat transfer in the tissue are associated with sparse temperature measurements, using an Unscented Kalman Filter. Methods: We compare a standard state-estimation filtering procedure with a joint-estimation (state and parameters) approach: whereas in the state-estimation only the temperature is evaluated, in the joint-estimation the filter corrects also uncertain model parameters (i.e., the medium thermal diffusivity, and laser beam properties). We have tested the method on synthetic temperature data, and on the temperature measured on agar-gel phantom and porcine liver with fiber optic sensors. Results: The joint-estimation allows retrieving an accurate estimate of the temperature distribution with a maximal error $< $ 1.5 $^{\circ }$ C in both synthetic and liver 1D data, and $< $ 2 $^{\circ }$ C in phantom 2D data. Our approach allows also suggesting a strategy for optimizing the temperature estimation based on the positions of the sensors. Under the constraint of using only two sensors, optimal temperature estimation is obtained when one sensor is placed in proximity of the source, and the other one is non-symmetrical. Conclusion: The joint-estimation significantly improves the predictive capability of the physical model. Significance: This work opens new perspectives on the benefit of data assimilation frameworks for laser therapy monitoring. [ABSTRACT FROM AUTHOR]

The dependence of computed tomography (CT) values on temperature has been pointed out by several authors since the late 1970s. They emphasised the importance of this phenomenon on the calibration process with water equivalent phantoms of the CT scanners. Few years later the potential of CT thermometry for non-invasive temperature mapping during thermal procedures was investigated. The interest on the employment of this technique during thermal treatments has been recently renewed with the improvement of modern CT scanner performances and with the increased popularity of minimally invasive thermal techniques for cancer treatment. A good thermometry allows avoiding unintended damage of the healthy tissues during the procedure by providing a detailed tissue temperature distribution; therefore, it is recommended in order to achieve good effectiveness of the thermal treatment. Researchers have been working on this issue for more than four decades and different non-invasive solutions have been proposed, i.e., microwave thermal imaging, infrared (IR)-, ultrasound-, magnetic-resonance (MR)-, and CT-based thermometry. This review aims to summarise the essential physics and the currently available data on CT-based thermometry and to elucidate the potential use of this technique during thermal procedures. Background information on measuring principle, an investigation of the performances achieved by this technique and the thermal sensitivity of the CT-number of different organs are provided and discussed. [ABSTRACT FROM AUTHOR]

Background: Pressures (Pe) exerted by bronchial blockers on the inner wall of the bronchi may cause mucosal ischaemia. Our aims were as follows: (i) to compare the intracuff pressure (Pi) and Pe exerted by commercially available bronchial blockers in an in vitro and an ex vivo model; (ii) to investigate the influence of both the inflated intracuff volume and cuff diameter on Pe; and (iii) to estimate the minimal sealing volume (VSmin) and the corresponding Pe for each bronchial blocker studied.Methods: The Pe exerted by seven commercial bronchial blockers was measured at different inflation volumes using a custom-designed system using in vitro and ex vivo animal models with two internal diameters (12 and 15 mm).Results: In the same conditions, Pi was significantly lower than Pe (P<0.05), and Pe was higher in the in vitro model than in the ex vivo model. The Pe increased with the inflated volume, with use of the small-diameter model (P<0.05). Ex vivo models needed a higher minimal sealing volume than the in vitro models, and this volume increased with the diameter (e.g. the VSmin at a positive pressure of 25 cm H2O required a Pe ranging from 12 to 78 mm Hg on the 15 mm ex vivo model and from 66 to 110 mm Hg on the 12 mm ex vivo model).Conclusions: The Pi cannot be used to approximate Pe. The diameter of the model, the inflated volume, and the bronchial blocker design all influence Pe. A pressure higher than the critical ischaemic threshold (i.e. 25 mm Hg) was needed to prevent air leak around the cuff in the in vitro and ex vivo models. [ABSTRACT FROM AUTHOR]

We characterized maraviroc susceptibility of dual/mixed tropic viruses from subjects enrolled onto phase IIb study A4001029. Maraviroc baseline plasma samples from 13 multidrug-experienced subjects were sequenced and the HIV-1-env gene cloned into pNL4.3Δenv to obtain recombinant viruses. The V3 region was sequenced by the Sanger method and ultradeep sequencing. By analysing subjects having a weighted optimized background therapy susceptibility (wOBT) score of <1, 3/7 subjects were characterized by good in vivo and in vitro response to maraviroc therapy. Molecular docking simulations allowed us to rationalize the maraviroc susceptibility of dual/mixed tropic viruses. A subset of subjects with dual/mixed tropic viruses responded to maraviroc. Further investigations are warranted of CCR5 antagonists in subjects carrying dual/mixed tropic virus that explore the feasible use of maraviroc in subjects that is potentially larger than those infected with a pure R5 virus. [ABSTRACT FROM AUTHOR]