Functional imaging method of biological electrical characteristics based on magneto-acoustic effect gives valuable information of tissue in early tumor diagnosis, therein time and frequency characteristics analysis of magneto-acoustic signal is important in image reconstruction. This paper proposes wave summing method based on Green function solution for acoustic source of magneto-acoustic effect. Simulations and analysis under quasi 1D transmission condition are carried out to time and frequency characteristics of magneto-acoustic signal of models with different thickness. Simulation results of magneto-acoustic signal were verified through experiments. Results of the simulation with different thickness showed that time-frequency characteristics of magneto-acoustic signal reflected thickness of sample. Thin sample, which is less than one wavelength of pulse, and thick sample, which is larger than one wavelength, showed different summed waveform and frequency characteristics, due to difference of summing thickness. Experimental results verified theoretical analysis and simulation results. This research has laid a foundation for acoustic source and conductivity reconstruction to the medium with different thickness in magneto-acoustic imaging.
This study aimed to verify whether the open-ended coaxial line tumor sensor with radio frequency was effective or not in detecting the differences in permittivity and conductivity between the breast malignant tissues and adjacent tissues. Sixteen breast infiltrating ductal carcinoma samples were freshly obtained from the department of general surgery in Zhujiang Hospital. The permittivity and conductivity of cancerous nidus points of breast samples, 3 cm adjacent tissue points and 5 cm adjacent tissue points were detected respectively by the open-ended coaxial line tumor sensor with radio frequency noninvasively in conjunction with vector network analyzer at the frequency ranging from 42.85~500 MHz. All the detected points were marked. After finishing the detection, we conducted postoperative pathological examinations on all the marked points. According to the statistics, there were statistically significant differences between the breast cancerous tissues and the 3 cm adjacent tissues for the dielectric properties (P < 0.01). There were statistically significant differences between the breast cancerous tissues and the 5 cm adjacent tissues for the dielectric properties (P < 0.01). There was no statistically significant difference in the dielectric properties between the 3 cm adjacent tissues and 5 cm adjacent tissues (P > 0.05). Both the 3 cm adjacent tissues and 5 cm adjacent tissues were found no breast cancer cell infiltration. The results indicated that the open-ended coaxial line tumor sensor at radio frequency could be effective in detecting the differences in permittivity and conductivity between breast cancerous tissues and adjacent tissues and, therefore, it may have a potential prospect in making a final diagnosis to confirm whether the detected breast tissue is malignant or not.
Through magnetic resonance electrical properties tomography (MR-EPT), electrical conductivity and permittivity of biological tissues could be reconstructed based on radio frequency field of magnetic resonance imaging (MRI) system. High precision and high resolution image could be obtained without current injection. In this study, XFDTD software was used to establish a finite element model of the human breast. Simulation was delivered at the Larmor frequency of 128 MHz by a 16-channel radio frequency coil. Conductivity and permittivity of the mammary tissue was reconstructed according to the B1+ field's amplitude and phase of forward problem. Anti-noise performance of the algorithm was studied by adding noise to B1+ field. The conductivity and permittivity's average relative error between simulation results and dielectric constant was 4.71% and 11.32%, respectively. With a signal-to-noise ratio of >30 dB, the noise added would not affect imaging results. This study demonstrated that high precision and high resolution image could be obtained by MR-EPT without excitation. MR-EPT had excellent feasibility and developing potential in early detection of diseases.
Objective To explore the construction and biocompatibility in vitro evaluation of the electrospun-graphene (Gr)/silk fibroin (SF) nanofilms. Methods The electrostatic spinning solution was prepared by dissolving SF and different mass ratio (0, 5%, 10%, 15%, and 20%) of Gr in formic acid solution. The hydrophilia and hydrophobic was analyzed by testing the static contact angle of electrostatic spinning solution of different mass ratio of Gr. Gr-SF nanofilms with different mass ratio (0, 5%, 10%, 15%, and 20%, as groups A, B, C, D, and E, respectively) were constructed by electrospinning technology. The structure of nanofilms were observed by optical microscope and scanning electron microscope; electrochemical performance of nanofilms were detected by cyclic voltammetry at electrochemical workstation; the porosity of nanofilms were measured by n-hexane substitution method, and the permeability were observed; L929 cells were used to evaluate the cytotoxicity of nanofilms in vitro at 1, 4, and 7 days after culture. The primary Sprague Dawley rats’ Schwann cells were co-cultured with different Gr-SF nanofilms of 5 groups for 3 days, the morphology and distribution of Schwann cells were identified by toluidine blue staining, the cell adhesion of Schwann cells were determined by cell counting kit 8 (CCK-8) method, the proliferation of Schwann cells were detected by EdU/Hoechst33342 staining. Results The static contact angle measurement confirmed that the hydrophilia of Gr-SF electrospinning solution was decreased by increasing the mass ratio of Gr. Light microscope and scanning electron microscopy showed that Gr-SF nanofilms had nanofiber structure, Gr particles could be dispersed uniformly in the membrane, and the increasing of mass ratio of Gr could lead to the aggregation of particles. The porosity measurement showed that the Gr-SF nanofilms had high porosity (>65%). With the increasing of mass ratio of Gr, the porosity and conductivity of Gr-SF nanofilm increased gradually, the value in the group A was significantly lower than those in groups C, D, and E (P<0.05). In vitro L929 cells cytotoxicity test showed that all the Gr-SF nanofilms had good biocompatibility. Toluidine blue staining, CCK-8 assay, and EdU/Hoechst33342 staining showed that Gr-SF nanofilms with mass ratio of Gr less than 10% could support the survival and proliferation of co-cultured Schwann cells. Conclusion The Gr-SF nanofilm with mass ratio of Gr less than 10% have proper hydrophilia, conductivity, porosity, and other physical and chemical properties, and have good biocompatibility in vitro. They can be used in tissue engineered nerve preparation.
Objective Historically, perioperative hemoglobin monitoring has relied on calculated saturation, using blood gas devices that measure plasma hematocrit (Hct). Co-oximetry, which measures total hemoglobin (tHb), yields a more comprehensive assessment of hemodilution. The purpose of this study was to examine the association of tHb measurement by co-oximetry and Hct, using conductivity with red blood cell (RBC) transfusion, length of stay (LOS) and inpatient costs in patients having major cardiac surgery. Methods A retrospective study was conducted on patients who underwent coronary artery bypass graft (CABG) and/or valve replacement (VR) procedures from January 2014 to June 2016, using MedAssets discharge data. The patient population was sub-divided by the measurement modality (tHb and Hct), using detailed billing records and Current Procedural Terminology coding. Cost was calculated using hospital-specific cost-to-charge ratios. Multivariable logistic regression was performed to identify significant drivers of RBC transfusion and resource utilization. Results The study population included 18 169 cardiovascular surgery patients. Hct-monitored patients accounted for 66% of the population and were more likely to have dual CABG and VR procedures (10.4% vs. 8.9%, P=0.006 9). After controlling for patient and hospital characteristics, as well as patient comorbidities, Hct-monitored patients had significantly higher RBC transfusion risk (OR=1.26, 95%CI 1.15-1.38,P<0.000 1), longer LOS (IRR=1.08, P<0.000 1) and higher costs (IRR=1.15, P<0.000 1) than tHb-monitored patients. RBC transfusions were a significant driver of LOS (IRR=1.25, P<0.000 1) and cost (IRR=1.22, P<0.000 1). Conclusion tHb monitoring during cardiovascular surgery could offer a significant reduction in RBC transfusion, length of stay and hospital cost compared to Hct monitoring.
In transcranial magnetic stimulation (TMS), the conductivity of brain tissue is obtained by using diffusion tensor imaging (DTI) data processing. However, the specific impact of different processing methods on the induced electric field in the tissue has not been thoroughly studied. In this paper, we first used magnetic resonance image (MRI) data to create a three-dimensional head model, and then estimated the conductivity of gray matter (GM) and white matter (WM) using four conductivity models, namely scalar (SC), direct mapping (DM), volume normalization (VN) and average conductivity (MC), respectively. Isotropic empirical conductivity values were used for the conductivity of other tissues such as the scalp, skull, and cerebrospinal fluid (CSF), and then the TMS simulations were performed when the coil was parallel and perpendicular to the gyrus of the target. When the coil was perpendicular to the gyrus where the target was located, it was easy to get the maximum electric field in the head model. The maximum electric field in the DM model was 45.66% higher than that in the SC model. The results showed that the conductivity component along the electric field direction of which conductivity model was smaller in TMS, the induced electric field in the corresponding domain corresponding to the conductivity model was larger. This study has guiding significance for TMS precise stimulation.