Research On The Dielectric Properties Of Freshly Excised Colorectal Cancerous Tissues Measured By The Open-ended Coaxial Line Method

Background and objectiveColorectal cancer is one of the most common gastrointestinal cancers.In recent years,there has been an increasing trend in the incidence and mortality rates in China.Therefore,early diagnosis and treatment of colorectal cancer is of great importance.In the electromagnetic field,the material could exhibit certain electrical and magnetic properties,which is the inherent property of the material.Electrical properties,also known as dielectric properties,are composed of two dielectric parameters,namely conductivity and permittivity.Previous studies have reported that the dielectric properties of tissues were frequency-dependent and were mainly affected by tissue types,temperature,and water content.Malignant tissue has higher values of dielectric properties than normal tissue because of its higher internal water content.The open-ended coaxial line system in the study equips the elaborate structure which is suitable for ultra wide band measurement of electrical properties.In addition,the detection system has characteristic of strong versatility,and it doesn't make special requirements for the physical shape and size of the measured material.So the solid,semi-solid and liquid substances can be under test without any sample processing.Currently it has become the most commonly used method of measuring the dielectric properties of biological tissues.The feasibility and accuracy of the open-ended coaxial line method that was used to measure both the permittivity and conductivity has been sufficiently demonstrated by previous studies.Accurate knowledge of the dielectric properties of different human tissues can reportedly be applied in cancer detection,hyperthermia treatment and the most recent technique called magnetic resonance electrical properties tomography(MREPT).However,a large proportion of previous studies have been limited to normal and/or benign tissues,with only an adequately profound knowledge of the dielectric properties of breast cancer and liver cancer tissues.There exists scant data regarding the dielectric properties of malignant colorectal tissues.The lack of such data led us to conduct the present study,which is the largest study to date regarding the dielectric properties of colorectal cancer.It aims to identify the differences in the dielectric properties between malignant and normal colorectal tissues,among different gross tumor configuration types,differentiated degrees,histological types,tumor invasion depths,and tumor stages.MethodsWith the open-ended coaxial line system starting to work,a wide frequency range from 50 to 500 MHz was adjusted to scan through the measurement process.In a typical calibration,open-circuit,short-circuit,and deionized water are used.Three liquids-namely,methyl alcohol,ethyl alcohol,and normal propyl alcohol-were selected to test their respective dielectric properties.101 preoperative diagnosis of colon/rectal cancer patients underwent surgical treatment in the operation room,and the experiment operators would perform dielectric properties measurement of freshly excised colorectal cancerous tissues,including the serosal surface of the carcinoma nidus,the mucosa of the carcinoma nidus,and the mucosa of the surgical resection margin.All tumor specimens were sent to take pathological section examination.and pathological T and TNM staging were determined according to the 2016 National Comprehensive Cancer Network(NCCN)colorectal cancer guidelines.The values of the dielectric properties at several discrete frequencies,including 64,85,128,170,213,255,298,341,383,426,and 500 MHz were selected for statistical analysis.ResultsAll of the 101 excised specimens were diagnosed as colonic or rectal cancer based on the pathological reports.Surgical resection was defined as normal tissue because no cancer cells could be found on any of the specimens.The ex vivo time was(10.30±8.50)min,and the experimental time was(11.86± 0.31)min.It took 30 seconds to test the dielectric characteristics for each measuring location.There was no statistically significant difference among temperature on the serosal surface of the carcinoma nidus,the mucosa of the carcinoma nidus,and the mucosa of the surgical resection margin(P>0.05).So was that between colonic and rectal tissues.Both the relative permittivity and conductivity of the cancerous mucosa were significantly greater than those of the normal mucosa(P<0.01),and there was on average a 8.98%difference in the relative permittivity and a 11.01%difference in the conductivity between these two locations.There were no statistical significances in the comparison of the differences in the dielectric properties among different gross tumor configuration types as well as differentiated degrees(P>0.05).In contrast to the dielectric properties of different histological types of colorectal cancer,mucinous adenocarcinoma had higher conductivity than adenocarcinoma over the measured frequencies except 341 and 500 MHz(P<0.05).Comparing the dielectric properties of different depths of tumor invasion,the relative permittivity and conductivity increased with higher T staging.There existed statistical differences in conductivity for cancerous serosa and cancerous mucosa at the common frequencies of 213 and 426 MHz among stages<T1(Tis + TO),T2,T3,T4(P<0.05).The tumor which invaded or penetrated the serosa(stage ?T3)had higher relative permittivity as well as conductivity than the one restricted to muscularis propria or less intestine wall(stage ?T2)at the common frequencies of 213 MHz and 426 MHz.In comparison with the differences in the dielectric properties of different TNM staging,there were statistically significant differences in the relative permittivity of both colorectal cancerous serosa and mucosa among stages<I(0 +?),?,?,and ? as well as between stages ?? and ??(P<0.05)at most frequencies under 300 MHz;significant differences in the conductivity were also observed for most of the measured frequencies.ConclusionThe open-ended coaxial line method could enable diagnostical differentiation between cancerous and normal colorectal tissue as well as reasonable assessment of pathological type,the depth of tumor infiltration and tumor staging.In the future,the open-ended coaxial line system is expected to be a real-time,fast,effective as well as accurate technique for detection of colorectal cancer.It can serve as an important reference for evaluating the prognosis of patients with colorectal cancer,selecting corresponding individualized therapy and making reasonable surgical strategies.