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Purpose: To investigate the effect of radiofrequency ablation (RFA) electrode trajectory on complete tumor ablation using computational simulation. Material and methods: The RFA of a spherical tumor of 2.0cm diameter along with 0.5cm clinical safety margin was simulated using Finite Element Analysis software. A total of 86 points inside one-eighth of the tumor volume along the axial, sagittal and coronal planes were selected as the target sites for electrode-tip placement. The angle of the electrode insertion in both craniocaudal and orbital planes ranged from -90° to +90° with 30° increment. The RFA electrode was simulated to pass through the target site at different angles in combination of both craniocaudal and orbital planes before being advanced to the edge of the tumor. Results: Complete tumor ablation was observed whenever the electrode-tip penetrated through the epicenter of the tumor regardless of the angles of electrode insertion in both craniocaudal and orbital planes. Complete tumor ablation can also be achieved by placing the electrode-tip at several optimal sites and angles. Conclusions: Identification of the tumor epicenter on the central slice of the axial images is essential to enhance the success rate of complete tumor ablation during RFA procedures. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this paper was to synthesise core-shell nanostructures comprised of mesoporous silica core and a low melting-point polyethylene glycol (PEG) nanoshell with a sharp gel–liquid phase transition for rapid drug release at hyperthermia temperature range.Materials and methods: The phase transition behaviours of PEGs with molecular weights of 1000, 1500, and 2000 Da were analysed using differential scanning calorimetry (DSC) to determine the optimal formulation with phase transition in the hyperthermia range. The ‘graft-to’ method was employed to synthesise core–shell nanostructures using the selected PEG formulation. The drug loading and release behaviours of these nanocarriers were examined by ultra-violet visible spectroscopy (UV-Vis) using doxorubicin as a model drug. Magnetic resonance-guided focused ultrasound (MRgFUS) was also applied as a typical thermal modality to evaluate the rate of drug release from the core-shell nanostructures.Results: The PEG molecular weight of 1500 Da presented the optimal phase transition temperature for thermal-triggered release under hyperthermia conditions. Drug release measurements at different temperatures using UV-Vis methods showed a 20.2 ± 4.3% leakage in aqueous solution at 37 °C after 30 min, while this value was significantly increased to 68.2 ± 3.7% at 50 °C. A 45.5 ± 3.1% drug release was also obtained after sonication of the drug-loaded nanoparticles for 5 × 20 s using MRgFUS.Conclusion: Although the ratio of drug leakage at physiological temperatures was relatively high, the sharp transition temperature, high loading efficiency, and fast drug release at hyperthermia temperature range could make these core-shell nanoparticles prominent for enhancing the efficacy of various hyperthermia modalities in the treatment of cancer tumours. [ABSTRACT FROM PUBLISHER]

Purpose: The aim of this paper was to introduce a new mechanism of thermal sensitivity in nanocarriers that results in a relatively low drug release at physiological temperature and rapid release of the encapsulated drug at hyperthermia and thermal ablation temperature range (40-60 °C). Materials and methods: The nanocarriers were synthesised by coating mesoporous silica nanoparticles with a thin layer of polyacrylamide. The low gelation temperature of the protective shell provides preferred routes for drug diffusion when the nanocarriers are heated within the hyperthermia temperature range. In order to determine the gelation point of polyacrylamide shell, differential scanning calorimetry was used. Various chemical, morphological, thermal, as well as drug loading capacities of these nanocarriers were characterised and their drug release behaviour was examined using magnetic resonance -guided focused ultrasound (MRgFUS). Results: Drug release measurements at different temperatures using doxorubicin showed 11.5 ± 2.4% leakage in aqueous solution at 37 °C after 30 min, while this value was significantly increased to 67.6 ± 2.5% at 60 °C. A 39.2 ± 2.2% release of doxorubicin was also obtained due to the sonication of drug-loaded nanoparticles for 5 × 20 s using MRgFUS. Conclusion: The nanocarriers developed do not exhibit a sharp transition temperature. However, a relatively high loading efficiency as well as rapid drug release at thermal ablation temperature range makes these nanostructures promising candidates for application as adjuvants to various thermal modalities such as radiofrequency and high intensity focused ultrasound. [ABSTRACT FROM AUTHOR]

Purpose: The emergence of thermal modalities has promoted the use of heat-sensitive phantoms for calibration, measurement, and verification purposes. However, development of durable phantoms with high precision ability to represent the temperature distribution remains a challenge. This study aims to introduce a reusable phantom that provides an accurate assessment of the heated region in various thermal modalities. Materials and methods: The phantom contains a thermochromic dye that is transparent blue at room temperature and becomes colourless after exceeding a threshold temperature. In order to determine the threshold temperature of the phantom, spectrophotometry analysis was performed. The various thermal (specific heat, thermal conductivity, melting point and latent heat of melting) and acoustic (sound speed, attenuation) properties of this phantom were measured and compared with those of the reference phantom without dye. The application of this phantom for radio-frequency and magnetic resonance guided focused ultrasound modalities was also examined. Results: The spectrophotometry analysis showed a threshold temperature of 50 ± 3 °C for this phantom. The results also demonstrated a 6 °C difference between the onset and ending temperatures of the discolouration process. Moreover, the starting temperature of colouration during cooling was found to be 4 °C lower than the ending temperature of discolouration. The sound speed, attenuation, specific heat, thermal conductivity and melting point of the heat-sensitive phantom were statistically equal to those of the reference phantom; however, the latent heat, and onset temperature of the melting of the heat-sensitive phantom were decreased by addition of the dye. Conclusions: The developed phantom is applicable for accurate evaluation of temperature variations in various thermal modalities. [ABSTRACT FROM AUTHOR]

Critical limb ischemia (CLI) is a syndrome manifested by ischemic rest pain, non-healing ulcers and tissue loss. CLI patients are at very high risk of amputation and experience poor physical function, leading to severe morbidity and mortality. The fundamental goal for CLI treatment is to relieve ischemic rest pain, heal ulcers, prevent limb loss and improve the quality of life, thereby extending the survival of the patient. Surgical or endovascular revascularization aimed at increasing blood flow is currently available for limb salvage in CLI. However, up to 30% of CLI patients are not suitable for such interventions because of high operative risk or unfavorable vascular anatomy. Therefore exploring new and more effective strategies for revascularization of ischemic limbs is imperative for the establishment of a viable therapeutic alternative. With the emergence of new approaches, this review describes up-to-date progress and developments in cell-based therapy as a novel and promising alternative for CLI treatment. Preliminary clinical data have established the safety, feasibility and efficacy of stem cells, and numerous studies are underway to consolidate this evidence further. However, significant hurdles remain to be addressed before this research can be responsibly translated to the bedside. In particular, we need better understanding of the behavior of cells post-transplantation and to learn how to control their survival and migration proliferation/differentiation in the hostile pathologic environment. Future research should focus on methods of isolation, optimal dosage, appropriate cell type, route of administration, role of tissue-derived factors and supportive endogenous stimulation. [ABSTRACT FROM AUTHOR]