Study On The Diversity Of Dielectric Properties Of Various Benign And Malignant Thyroid Nodules

Background and objectiveThyroid disease is a common surgical disease,.Over the past few decades,the incidence of thyroid cancer has increased significantly,most of which are characterized by abnormally proliferating thyroid nodules.Previous studies have shown that the prevalence of thyroid nodules is as high as 68%,of which the risk of malignant tumors is about 10%.It is important to understand the pathological nature of the diseased nodules for the treatment,diagnosis and prognosis of thyroid disease,and to try to find and treat the disease as early as possible.At present,the common auxiliary examinations are ultrasonography and fine-needle aspiration cytology,CT etc.,and various auxiliary examination methods have their own limitations.At present,the most-relied intraoperative histopathological frozen sections also have certain shortcomings.Based on this,we hope that there is a method that can provide early warning information in the early stage of the disease.Any substance,including all biological tissues,including human tissues,can exhibit certain electromagnetic characteristics in an external electromagnetic field,which is an intrinsic property of the substance.The dielectric characteristics are generally expressed by two parameters,namely,the dielectric constant and the electrical conductivity.When the physiological or pathological state of the tissue changes,the dielectric characteristics will also change,especially after the tissue becomes cancerous,this change is more obvious.And based on this change,a variety of new diagnostic and therapeutic methods have been developed,such as magnetic resonance electric properties,electrical impedance tomography and microwave ablation.The open-ended coaxial probe method is a widely used method for measuring the dielectric properties of biological tissues at present.It has minimally invasive,fast,non-radiation,real-time in-vivo measurement,and is not affected by the water content of the measurement sample.Therefore,we chose to use the open-ended coaxial probe method to obtain the dielectric properties of thyroid tissue,and compare the dielectric properties of normal thyroid tissue,various benign and malignant thyroid nodules.MethodsBefore the measurement,follow the standard procedure to set up the measuring instruments,and follow the open circuit and short circuit in sequence;measure the dielectric properties of deionized water,physiological saline,anhydrous methanol,and absolute ethanol as the calibration data for later calculations,and record the temperature of four fluids,tissue,and room.The dielectric parameters of the freshly excised thyroid nodules and the tissues 1cm away from the nodules were measured.The specimens were examined by experienced pathologists.ResultsConfirmed by pathological examination,five types of thyroid tissues were measured including normal tissues,benign nodules:nodular goiter,follicular adenoma,and malignant nodules:papillary carcinoma and follicular carcinoma which were.After comparison,it was found that the value of the dielectric permittivity was positively correlated with the degree of malignancy of these nodules(normal<benign<malignant;all differences p<0.05).This was more obvious at frequencies within 20M～70 MHz:normal tissue<nodular goiter<follicular adenoma<papillary carcinoma<follicular carcinoma.A significant difference(p<0.05)in dielectric permittivity and conductivity was found when comparing these nodules with the surrounding 1 cm of tissue.ConclusionThe normal,benign,and malignant nodules were successfully distinguished,and the dielectric permittivity was found to be more sensitive.In particular,different disease types can be distinguished at a stimulation frequency of 20M to 70 MHz,which shows that the dielectric properties measured by the open-ended coaxial line method can provide warning information on thyroid diseases at different stages.At the same time,the dielectric parameter differences between the surrounding 1 cm of tissue and the diseased nodule can distinguish the tumor and its surrounding tissues in real time during the surgery to determine the tumor boundary.The results of our experiment complement the dielectric properties of pathological thyroid tissue and provide a theoretical basis for further clinical applications.