OBJECTIVE: To investigate the sensing volume of open-ended coaxial probe technique for measurement of dielectric characteristics. METHODS: A measurement model combining macro- measurement device with a layer model of dielectric properties parameters was established for evaluating the sensing volume of open-ended coaxial probe technique. We defined sensing depth and sensing diameter to describe the distance that could be detected in vertical and horizontal direction. Using a variety of materials with different dielectric properties (Teflon, deionized water, ethanol, and gradient concentration sodium chloride solution), a layered model of dielectric properties differentiation was established. The total combined uncertainties (TCU) were calculated for different output power, and the output power was controlled to increase from -50 dBm to 15 dBm to calibrate the error range of the dielectric properties measurement system. The optimal output power range was determined based on the results of TCU test. In sensing volume measurement experiment, we set the control groups based on measurement parameters that potentially affect the sensing volume including output power (-10, -5, 0, 3, 6, and 9 dBm), frequency (1-500 MHz), Teflon, deionized water, and ethanol to form a dielectric constant difference between high and low contrast groups. Different concentrations of sodium chloride solution and Teflon were used to generate a conductivity difference between high and low contrast groups. These groups were tested in the sensing depth and sensing diameter measurement experiments. RESULTS: The result of TCU test indicated that accurate and stable measurement results could be obtained when the output power was greater or equal to-10 dBm (TCU < 2%). Sensing volume measurement experiment revealed a positive correlation between the sensing depth and output power ( < 0.05). As the measured power increased, the sensing depth gradually increased in deionized water and ethanol, and the difference reached 70 μm. The sensing depth was negatively correlated frequency ( < 0.05). As the concentration of sodium chloride solution increased, the corresponding sensing depth gradually decreased, with a difference reaching 270 μm. The sensing depth of high dielectric materials was greater than that pf low dielectric materials. The results of sensing diameter measurement were not obviously affected by the measurement parameters, and the sensing diameter was stable in a fixed range (1.0 to 1.8 mm) between the diameter of the inner conductor and the diameter of the insulation layer, and was less than the diameter of the probe. CONCLUSIONS The sensing volume of open-ended coaxial probe technique is affected by measurement parameters and dielectric properties of materials, which significantly affect the sensing depth.
Algorithms ; Electric Conductivity ; Electrochemistry ; instrumentation

OBJECTIVE: To investigate the sensing volume of open-ended coaxial probe technique for measurement of dielectric characteristics. METHODS: A measurement model combining macro- measurement device with a layer model of dielectric properties parameters was established for evaluating the sensing volume of open-ended coaxial probe technique. We defined sensing depth and sensing diameter to describe the distance that could be detected in vertical and horizontal direction. Using a variety of materials with different dielectric properties (Teflon, deionized water, ethanol, and gradient concentration sodium chloride solution), a layered model of dielectric properties differentiation was established. The total combined uncertainties (TCU) were calculated for different output power, and the output power was controlled to increase from -50 dBm to 15 dBm to calibrate the error range of the dielectric properties measurement system. The optimal output power range was determined based on the results of TCU test. In sensing volume measurement experiment, we set the control groups based on measurement parameters that potentially affect the sensing volume including output power (-10, -5, 0, 3, 6, and 9 dBm), frequency (1-500 MHz), Teflon, deionized water, and ethanol to form a dielectric constant difference between high and low contrast groups. Different concentrations of sodium chloride solution and Teflon were used to generate a conductivity difference between high and low contrast groups. These groups were tested in the sensing depth and sensing diameter measurement experiments. RESULTS: The result of TCU test indicated that accurate and stable measurement results could be obtained when the output power was greater or equal to-10 dBm (TCU < 2%). Sensing volume measurement experiment revealed a positive correlation between the sensing depth and output power ( < 0.05). As the measured power increased, the sensing depth gradually increased in deionized water and ethanol, and the difference reached 70 μm. The sensing depth was negatively correlated frequency ( < 0.05). As the concentration of sodium chloride solution increased, the corresponding sensing depth gradually decreased, with a difference reaching 270 μm. The sensing depth of high dielectric materials was greater than that pf low dielectric materials. The results of sensing diameter measurement were not obviously affected by the measurement parameters, and the sensing diameter was stable in a fixed range (1.0 to 1.8 mm) between the diameter of the inner conductor and the diameter of the insulation layer, and was less than the diameter of the probe. CONCLUSIONS The sensing volume of open-ended coaxial probe technique is affected by measurement parameters and dielectric properties of materials, which significantly affect the sensing depth.
Algorithms ; Electric Conductivity

OBJECTIVE: To investigate the effects of millimeter wave (MMW) exposure on apoptosis of human melanoma A375 cells and explore the mechanisms. METHODS: Through electromagnetic field calculation we simulated MMW exposure in cells and calculated the specific absorption rate (SAR). The optimal irradiation parameters were determined according to the uniformity and intensity of the SAR. A375 cells were then exposed to MMV for 15, 30, 60, or 90 min, with or without pretreatment with the caspase-3 inhibitor AC-DEVD-fmk (10 μmol/L) for 1 h at 90 min before the exposure. CCK-8 assay was used to assess the changes in the viability and Annexin-V/ PI staining was used to detect the apoptosis of the cells following the exposures; Western blotting was used to detect the expression of caspase-3 in the cells. RESULTS: The results of electromagnetic field calculation showed that for optimal MMV exposure, the incident field needed to be perpendicular to the bottom of the plastic Petri dish with the antenna placed below the dish. CCk-8 assay showed that MMW exposure significantly inhibited the cell viability in a time-dependent manner ( < 0.05); exposures for 15, 30, 60, and 90 min all resulted in significantly increased apoptosis of the cells ( < 0.05). The cells with MMW exposure showed significantly increased expression of caspase-3. The inhibitory effect of MMW on the cell viability was antagonized significantly by pretreatment of the cells with AC-DEVD-fmk ( < 0.05), which increased the cell viability rate from (36.7±0.09)% to (59.8±0.06)% ( < 0.05). CONCLUSIONS 35.2 GHz millimeter wave irradiation induces apoptosis in A375 cells by activating the caspase-3 protein.
Apoptosis ; Caspase 3 ; metabolism ; Caspase Inhibitors ; pharmacology ; Cell Line, Tumor ; Cell Survival ; Electromagnetic Fields ; Enzyme Activation ; Humans ; Magnetic Field Therapy ; Melanoma ; enzymology ; pathology ; therapy ; Time Factors

OBJECTIVE: To investigate the application of high-frequency ultrasound (HFUS) and optical coherence tomography (OCT) for monitoring the progression of cutaneous melanoma (CM) in nude mice. METHODS: Twenty 4-week-old nude mice were randomly divided into CM group (=16) and control group (=4). In CM group, A375 cell suspension were injected subcutaneously on the back of the nude mice, and only culture medium was injected in the control group. The tumor growth was monitored by gross observation and with HFUS and OCT on a daily basis. The tumor formation rate, time, and size were recorded and melanoma visibility was assessed quantitatively using the contrast- to-background-noise ratio (CNR). Twentyfour days after cell implantation, the tumors were dissected for pathological examination. RESULTS: The tumor formation rate was 87.5% in CM group. OCT detected tumor formation at an earlier time than HFUS. With the growth of the tumor, HFUS detected spots or bands of strong echoes, and flattening of the upper dermis could be observed in OCT; the of HFUS and OCT were obviously enhanced over time ( < 0.05). The tumor growth curve showed that OCT was more sensitive for measurement of the tumor thickness than HFUS. The length, depth and volume of the tumors measured by HFUS were significantly greater than those measured by OCT ( < 0.05). CONCLUSIONS HFUS and OCT can monitor the dynamic development of cutaneous melanoma in nude mice, and their imaging performance differs in different stages of tumor development.
Animals ; Melanoma ; Mice ; Mice, Nude ; Skin Neoplasms ; Tomography, Optical Coherence ; Ultrasonography

Objective To estimate the diagnostic value of cytology, DNA-ICM(DNA-image cytometry),cytology combined with DNA-ICM for pancreatic malignancy,and to explore the cut-off value for DNA-ICM. Methods Patients with suspicious pancreatic malignancy were retrospectively identified. In total,145 EUS-FNA specimens acquired from 140 separate patients were examined by cytology and DNA-ICM. Diagnostic values among cytology, DNA-ICM and the combination of the techniques in detecting pancreatic malignancy were compared. Results Compared with cytology, DNA-ICM had a lower sensitivity (63.0% VS 82.4%)and accuracy(69.7% VS 85.5%). After combining the techniques, the diagnostic value for pancreatic malignancy significantly improved compared with that by cytology(0.941 VS 0.912, P=0.007 0)or DNA-ICM only(0.941 VS 0.815, P<0.000 1). By using the Youden index, the cut-off value for DNA-ICM to detect pancreatic malignancy was one cell with DI(DNA index)≥2.5. Notably,with this standard, the sensitivity and accuracy of DNA-ICM significantly increased to 72.3% and 77.2%, and those of the combined techniques increased to 91.6% and 93.1%, respectively. Conclusion Automated DNA-ICM is an objective and effective method for pancreatic malignancy. Although DNA-ICM has a lower diagnostic value than that of conventional cytology, an improved value was obtained after combining the techniques.

Objective To investigate the clinical outcome of pancreatic pseudocyst(PPC)treated with non-surgical methods,and to compare the efficacy and safety between percutaneous drainage and endoscopic drainage in the management of PPC.Methods From February 2010 to July 2017,clinical data of patients with PPC,who received percutaneous drainage or endoscopic drainage,were retrospectively analyzed.The symptom relief rate,short-term and long-term radiologic remission rate,complication rate, recurrence rate and length of hospital stay were compared between patients treated by ultrasound guided percutaneous drainage(percutaneous group),by endoscopic ultrasonography-guided drainage(EUS group)and by endoscopic retrograde pancreatography guided transpapillary drainage(ERP group).Two independent samples t test,one-way analysis of variance,non-parametric test and Fisher′s exact test were performed for statistical analysis.Results A total of 153 patients were treated and the operation was successfully conducted in 148 patients(96.7%),of whom 39 were in percutaneous group,73 in EUS group and 36 in ERP group.The median follow-up time was 26 weeks(two weeks to 358 weeks).The symptom relief rate,long-term radiographic remission rate,complication rate,recurrence rate and retreatment rate of percutaneous group,EUS group and ERP group were 87.2%(34/39),79.5%(58/73),80.6%(29/36);81.5%(22/27),88.6%(39/44),66.7%(16/24);17.9%(7/39),28.8%(21/73),16.7%(6/36);15.0%(3/20),13.8%(8/58),10.0%(2/20);and 10.3%(4/39),8.2%(6/73),2.8%(1/36),respectively.There was no statistically significant difference among three groups (all P> 0.05).The short-term radiographic remission rate of ERP group was significantly lower than those of percutaneous group and EUS group(46.7%,14/30 vs 77.1%,27/35 and 87.7%,64/73),and the differences were statistically significant(χ2 =6.442 and 19.450,both P<0.01).The median hospital stay of percutaneous group was longer than those of EUS group and ERP group(14.0 days vs 9.0 days and 8.0 days),and the differences were statistically significant(Z= -3.687 and -2.630,both P<0.01).Conclusions The efficacies of percutaneous drainage and EUS-guided drainage are both better than ERP,and they are effective and safe methods especially for the patients with complication of pseudocysts and necrosis debris in pseudocysts.However,the hospitalization time of percutaneous drainage is longer. In addition,percutaneous drainage can be an alternative method after failed endoscopic drainage.

Objective To explore the diagnostic value of endoscopic ultrasonography(EUS)for the minimal submucosal invasion of early gastrointestinal tumor. Methods A total of 242 patients with early gastrointestinal tumor,who underwent endoscopic submucosal dissection,were retrospectively analyzed. The accuracy of EUS diagnosis was calculated based on postoperative histopathological findings as the golden standard,and influencing factors were also analyzed. Results Overall diagnostic accuracy of EUS for sub-mucosal invasion of early gastrointestinal tumors was 72. 3%(175/ 242),with an overstaging rate of 21. 5%(52/ 242)and an understaging rate of 6. 2%(15/ 242).Tumor size(P = 0. 018)and location(P = 0. 005) had significant effects on the diagnostic accuracy of the minimal submucosal invasion of early gastrointestinal tumor by EUS. The overstaging rate in the lesion length of diameter>3 cm was higher than those of 3 cm or less[27. 0%(33/ 122)VS 15. 8%(19/ 120),P = 0. 807],the overstaging rates of early colonrectal and gastric cancer were also significantly higher than the understaging rate[ Colonrectum:12. 2%(9/ 74)VS 2. 7%(2/ 74),P= 0. 028;Stomach:26. 9%(28/ 104)VS 2. 9%(3/ 104),P = 0. 000]. Conclusion Endoscopic ultrasonography is of diagnostic value for the invasion depth of early cancer in gastrointestinal tract. However,precaution should be taken in large lesions and the tendency of overstaging in gastrointestinal tract.

Objective To confirm whether the open-ended coaxial line is effective in detection of the differences in dielectric properties between colorectal cancer tissues and surrounding normal tissues and evaluation of the depth of tumor invasion. Methods The open-ended coaxial line system at frequencies ranging from 50 to 500 MHz in 98 freshly excised colorectal cancerous specimens obtained from the operating theatre of Zhujiang Hospital, was used to detect both the relative permittivity and conductivity on the serosal surface of the carcinoma nidus, the mucosa of the carcinoma nidus, and the mucosa of the surgical resection margin. Pathological examinations were conducted on each specimen after surgery. Results The values for relative permittivity and conductivity of the colorectal cancerous mucosa were significantly higher than those of the normal mucosa (P < 0.01). For the tumor which had invaded or penetrated the serosa (stage ≥ T3), the dielectric properties of both the cancerous serosa and mucosa were higher than the one restricted to muscularis propria or less intestine wall (stage < T3) over the measured frequency range, and there existed statistical differences at the common frequencies of 213 MHz and 426 MHz. Conclusion The open-ended coaxial line system may result in fast and effective diagnostic differentiation between cancerous and normal colorectal tissues as well as reasonable assessment of the tumor infiltration depth.

OBJECTIVETo study the efficacy of B1 field shimming technique and evaluate the specific absorption rate (SAR) in ultra-high field magnetic resonance imaging (MRI) for MRI-guided high-intensity focused ultrasound (HIFU).

METHODSAn electromagnetic model of the female pelvis with a temperature gradient was established. B1 field homogeneity and local SAR were simulated and calculated using regular and optimized B1 shimming coefficients.

RESULTSThe maximum local SAR reached 10.24 W/kg, which exceeded the safe threshold of 10 W/kg, as calculated using regular B1 shimming coefficients in the normal model. Using the optimized B1 shimming coefficients, the maximum local SAR of the tissue was 9.65 W/kg, which was below the safe threshold.

CONCLUSIONThe temperature distributions in the body generated by ultrasound energy need to be considered in ultra-high field MRI-guided HIFU surgery. The proposed optimized B1 shimming strategy based on the temperature gradient can be used to control the local SAR levels.

In the present study, the effect of the electromagnetic field, induced by radio frequency (RF) coils and coupled with the pelvic tissues, was calculated with the method of finite difference time domain (FDTD). Using the established electromagnetic model of human pelvis region, the simulation was implemented. The imaging uniformity was quantitatively calculated and scaled with the values of the percentage image uniformity (PIU). The electromagnetic model was derived from the anatomical data of human pelvic region and loaded into the simulation. The results showed that the homogeneity of the magnetic fields was severely damaged due to the coupling between the RF coil and the human tissues when loaded with the human pelvis in the Birdcage RF coils at 3T. The research results set a basis meaningful for the design of RF coils.
Adult ; Algorithms ; Computer Simulation ; Electromagnetic Fields ; Equipment Design ; Female ; Humans ; Magnetic Resonance Imaging ; instrumentation ; Magnetics ; instrumentation ; Models, Anatomic ; Pelvis ; anatomy & histology ; diagnostic imaging ; Radio Waves ; Tomography, X-Ray Computed