Optimization of polyethylene glycol-based hydrogel rectal spacer for focal laser ablation of prostate peripheral zone tumor

Development of a prediction model for hyperthermia-enhanced drug delivery using thermosensitive nanoparticles

Therapies targeting solid tumors are often hindered by drug resistance mechanisms, which presenting significant challenges. This study investigates the synergistic effect of hyperthermia and chemotherapy by utilizing thermosensitive nanoparticles (NPs) to enhance drug uptake by cancer cells. The thermoresponsive nature of NPs enables precise drug release under hyperthermic conditions, making them ideal for localized treatment. To achieve this, we developed a multi-component numerical model of focused ultrasound-enhanced doxorubicin delivery using tumor-targeting nanoparticles. The model incorporates critical factors such as blood coagulation and non-Fourier heat transfer, and it was validated against experimental results, thereby enhancing the reliability and accuracy of our findings. Ultimately, a prediction model was developed to estimate heat-driven irreversible cell damage in relation to heating power and NP size. The results demonstrated a remarkable 13-fold increase in drug penetration and a 4.6-fold enhancement in the fraction of killed cells with hyperthermia. These findings underscore the importance of accurately controlling the temperature field and heating power for optimal hyperthermia-assisted chemotherapy outcomes.

A new model of electrosurgical tissue damage for neurosurgery simulation

BACKGROUND

Bipolar hemostasis electrocoagulation is a fundamental procedure in neurosurgery. A precise electrocoagulation model is essential to enable realistic visual feedback in virtual neurosurgical simulation. However, existing models lack an accurate description of the heat damage and irreversible tissue deformation caused by electrocoagulation, thus diminishing the visual realism. This work focuses on the electrocoagulation model for neurosurgery simulation.

METHOD

In this paper, a position-based dynamics (PBD) model with a bioheat transfer and damage prediction (BHTDP) method is developed for simulating the deformation of brain tissue caused by electrocoagulation. The presented BTHDP method uses the Arrhenius equation to predict thermal damage of brain tissue. A deformation model with energy and thermal damage constraints is developed to characterize soft tissue deformation during heat absorption before and after thermal injury. Visual effect of damaged brain tissue is re-rendered.

RESULT

To evaluate the accuracy of the proposed method, numerical simulations were conducted and compared with commercial finite element software. The maximum normalized error of the proposed model for predicting midpoint temperature is 10.3 % and the maximum error for predicting the thermal damage is 5.4 %. The contraction effects of heat-exposed anisotropic tissues are also simulated. The results indicate that the presented electrocoagulation model provides stable and realistic visual effects, making it applicable for simulating the electrocoagulation process in virtual neurosurgery.

A sensitivity analysis of laser thermotherapy efficacy in lung cancer treatment to the temperature dependence of thermal properties

Laser interstitial thermotherapy has shown potential in the treatment of inoperable lung cancers, which make up 70-80 % of all cases, thanks to the possibility of real-time ultrasound guidance, a fine introducer needle, and faster recovery after the procedure. To plan a laser ablation session through numerical modeling, the sensitivity analysis of the input parameters is necessary since simplifying the influential parameters could lead to a different treatment outcome.The purpose of this study is to determine the sensitivity of laser-induced ablated volume, an indicator of therapy efficacy, with regard to the temperature dependence of thermal properties in the clinical power ranges (i.e., between 2 W and 5 W at the wavelength of 1064 nm) for lung tissue. According to the results, the difference between ablated volumes derived from constant and temperature-dependent thermal properties grows with increasing power, reaching 17.5% and 60.3% under ex vivo and in vivo conditions at 5 W, respectively. As the blood perfusion rate strongly affects the thermal effects in tissue, the temperature dependency of this parameter cannot be ignored. The assumption of constant thermal properties is valid for ex vivo planning by acceptable error when the laser power is set at a low level, e.g., ~ 2% at 2 W and ~ 6% at 3 W.Clinical Relevance-The methods and results of this study set the basis for defining the accurate pre-planning of laser-induced thermotherapy of lung cancer.

Optimization of laser dosimetry based on patient-specific anatomical models for the ablation of pancreatic ductal adenocarcinoma tumor

Laser-induced thermotherapy has shown promising potential for the treatment of unresectable primary pancreatic ductal adenocarcinoma tumors. Nevertheless, heterogeneous tumor environment and complex thermal interaction phenomena that are established under hyperthermic conditions can lead to under/over estimation of laser thermotherapy efficacy. Using numerical modeling, this paper presents an optimized laser setting for Nd:YAG laser delivered by a bare optical fiber (300 µm in diameter) at 1064 nm working in continuous mode within a power range of 2-10 W. For the thermal analysis, patient-specific 3D models were used, consisting of tumors in different portions of the pancreas. The optimized laser power and time for ablating the tumor completely and producing thermal toxic effects on the possible residual tumor cells beyond the tumor margins were found to be 5 W for 550 s, 7 W for 550 s, and 8 W for 550 s for the pancreatic tail, body, and head tumors, respectively. Based on the results, during the laser irradiation at the optimized doses, thermal injury was not evident either in the 15 mm lateral distances from the optical fiber or in the nearby healthy organs. The present computational-based predictions are also in line with the previous ex vivo and in vivo studies, hence, they can assist in the estimation of the therapeutic outcome of laser ablation for pancreatic neoplasms prior to clinical trials.

Spacer-Supported Thermal Ablation to Prevent Carbonisation and Improve Ablation Size: A Proof of Concept Study

Thermal ablation offers a minimally invasive alternative in the treatment of hepatic tumours. Several types of ablation are utilised with different methods and indications. However, to this day, ablation size remains limited due to the formation of a central non-conductive boundary layer. In thermal ablation, this boundary layer is formed by carbonisation. Our goal was to prevent or delay carbonisation, and subsequently increase ablation size. We used bovine liver to compare ablation diameter and volume, created by a stand-alone laser applicator, with those created when utilising a spacer between laser applicator and hepatic tissue. Two spacer variants were developed: one with a closed circulation of cooling fluid and one with an open circulation into hepatic tissue. We found that the presence of a spacer significantly increased ablation volume up to 75.3 cm³, an increase of a factor of 3.19 (closed spacer) and 3.02 (open spacer) when compared to the stand-alone applicator. Statistical significance between spacer variants was also present, with the closed spacer producing a significantly larger ablation volume (p < 0.001, M_Diff = 3.053, 95% CI[1.612, 4.493]) and diameter (p < 0.001, M_Diff = 4.467, 95% CI[2.648, 6.285]) than the open spacer. We conclude that the presence of a spacer has the potential to increase ablation size.