An Electrode Array for Limiting Blood Loss During Liver Resection: Optimization via Mathematical Modeling

Liver resection is the current standard treatment for patients with both primary and metastatic liver cancer. The principal causes of morbidity and mortality after liver resection are related to blood loss (typically between 0.5 and 1 L), especially in cases where transfusion is required. Blood transfusions have been correlated with decreased long-term survival, increased risk of perioperative mortality and complications. The goal of this study was to evaluate different designs of a radiofrequency (RF) electrode array for use during liver resection. The purpose of this electrode array is to coagulate a slice of tissue including large vessels before resecting along that plane, thereby significantly reducing blood loss. Finite Element Method models were created to evaluate monopolar and bipolar power application, needle and blade shaped electrodes, as well as different electrode distances. Electric current density, temperature distribution, and coagulation zone sizes were measured. The best performance was achieved with a design of blade shaped electrodes (5 × 0.1 mm cross section) spaced 1.5 cm apart. The electrodes have power applied in bipolar mode to two adjacent electrodes, then switched sequentially in short intervals between electrode pairs to rapidly heat the tissue slice. This device produces a ~1.5 cm wide coagulation zone, with temperatures over 97 ºC throughout the tissue slice within 3 min, and may facilitate coagulation of large vessels

Changes in optical properties of ex vivo rat prostate due to heating

This study examines the effectiveness of a single, first-order Arrhenius process in accurately modelling the thermally induced changes in the optical properties, particularly the reduced scattering coefficient, μ'(s), and the absorption coefficient, μ(a), of ex vivo rat prostate. Recent work has shown that μ'(s) can increase as much as five-fold due to thermal coagulation, and the observed change in μ'(s) has been modelled well according to a first- order rate process in albumen. Conversely, optical property measurements conducted using pig liver suggest that this change in μ'(s) cannot suitably be described using a single rate parameter. In canine prostate, measurements have indicated that while the absorption coefficient varies with temperature, it does not do so according to first-order kinetics. A double integrating sphere system was used to measure the reflectance and transmittance of light at 810 nm through a thin sample of prostate. Using prostate samples collected from Sprague-Dawley rats, optical properties were measured at a constant elevated temperature. Tissue samples were measured over the range 54-83 °C. The optical properties of the sample were determined through comparison with reflectance and transmittance values predicted by a Monte Carlo simulation of light propagation in turbid media. A first-order Arrhenius model was applied to the observed change in μ'(s) and μ(a) to determine the rate process parameters for thermal coagulation. The measured rate coefficients were E(a) = (7.18 ± 1.74) x 104 J mol-1 and A(freq) = 3.14 x 108 s-1 for μ'(s). It was determined that the change in μ'(s) is well described by a single first-order rate process. Similar analysis performed on the changes in μ(a) due to increased temperatures yielded E(a) = (1.01 ± 0.35) x 105 J mol-1 and A(freq) = 8.92 x 1012 s-1. The results for μ(a) suggest that the Arrhenius model may be applicable to the changes in absorption

Induced pluripotent stem cell-related genes influence biological behavior and 5-fluorouracil sensitivity of colorectal cancer cells*

Objective: We aimed to perform a preliminary study of the association between induced pluripotent stem cell (iPS)-related genes and biological behavior of human colorectal cancer (CRC) cells, and the potential for developing anti-cancer drugs targeting these genes. Methods: We used real-time reverse transcriptase polymerase chain reaction (RT-PCR) to evaluate the transcript levels of iPS-related genes NANOG, OCT4, SOX2, C-MYC and KLF4 in CRC cell lines and cancer stem cells (CSCs)-enriched tumor spheres. NANOG was knockdowned in CRC cell line SW620 by lentiviral transduction. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays, plate colony formation, and a mouse xenograft model were used to evaluate alterations in biological behavior in NANOG-knockdown SW620 cells. Also, mock-knockdown and NANOG-knockdown cells were treated with 5-fluorouracil (5-FU) and survival rate was measured by MTT assay to evaluate drug sensitivity. Results: A significant difference in the transcript levels of iPS-related genes between tumor spheres and their parental bulky cells was observed. NANOG knockdown suppressed proliferation, colony formation, and in vivo tumorigenicity but increased the sensitivity to 5-FU of SW620 cells. 5-FU treatment greatly inhibited the expression of the major stemness-associated genes NANOG, OCT4, and SOX2. Conclusions: These results collectively suggest an overlap between iPS-related genes and CSCs in CRC. Quenching a certain gene NANOG may truncate the aggressiveness of CRC cells