Measurement of bioelectric and acoustic profile of breast tissue using hybrid magnetoacoustic method for cancer detection

A Preliminary Study on Non-Invasive Detection of Electrical Stimulation Current Based on Magneto-Acoustic Effect

Electrical stimulation is widely used in nerve regulation and treatment. The detection of the distribution of stimulation current in tissues is of great significance to improve the accuracy of electrical stimulation, but the current technical means are still difficult to achieve the non-invasive detection of stimulation current. This study proposes a non-invasive detection method of electrical stimulation current based on the magneto-acoustic (MA) effect, which has the advantages of high spatial resolution and high spatial contrast. In this study, continuous sine waves with the frequency of 20kHz are used to stimulate samples. The MA signal generated by the stimulation current in the samples in a stable magnetic field is detected by lock-in amplifier, and the two-dimensional distribution of sound source is extracted. The current density distribution of samples is simulated by the method of finite element analysis, and the simulation results are verified by experiments. The results show that under the electrical stimulation of the order of 0.01A, the location measurement of two-dimensional surface sound source with millimeter accuracy can be achieved non-invasively in isolated pork and pig brain, and the measurement accuracy of weak MA signal can reach 10^-7Pa. In short, the stimulation current detection method based on MA effect can achieve the non-invasive and high-precision detection of electrical stimulation current distribution, which is of great significance to improve the stimulation accuracy and study the neural regulation mechanism of electrical stimulation.

A preliminary in vivo study of a method for measuring magneto-acoustic sonic source under electrical stimulation

BACKGROUND

Stimulating current distribution in the tissue is unknown due to the complex distribution.

OBJECTIVE

A preliminary in vivo measurement of the magneto-acoustic (MA) signal of the human finger is performed in this study. The approach for locating the magneto-acoustic source of the stimulating current is studied.

METHODS

We use a lock-in amplifier to measure the MA signal under continuous wave electrical stimulation. The phase of the MA signal is used to extract the location of the sonic source. The experimental system is designed to measure the MA signal under electrical stimulation.

RESULTS

Preliminary experiments results show that the amplitude precision is improved to less than 1 μPa. The sonic source is located with millimetre precision.

CONCLUSIONS

We propose a new MA source-locating method with high measurement and location precision. This method will be significant to the study of the imaging and monitoring of the current distribution of electrical stimulation with high precision.

Magneto-acoustic imaging by continuous-wave excitation

The electrical characteristics of tissue yield valuable information for early diagnosis of pathological changes. Magneto-acoustic imaging is a functional approach for imaging of electrical conductivity. This study proposes a continuous-wave magneto-acoustic imaging method. A kHz-range continuous signal with an amplitude range of several volts is used to excite the magneto-acoustic signal and improve the signal-to-noise ratio. The magneto-acoustic signal amplitude and phase are measured to locate the acoustic source via lock-in technology. An optimisation algorithm incorporating nonlinear equations is used to reconstruct the magneto-acoustic source distribution based on the measured amplitude and phase at various frequencies. Validation simulations and experiments were performed in pork samples. The experimental and simulation results agreed well. While the excitation current was reduced to 10 mA, the acoustic signal magnitude increased up to 10^-7 Pa. Experimental reconstruction of the pork tissue showed that the image resolution reached mm levels when the excitation signal was in the kHz range. The signal-to-noise ratio of the detected magneto-acoustic signal was improved by more than 25 dB at 5 kHz when compared to classical 1 MHz pulse excitation. The results reported here will aid further research into magneto-acoustic generation mechanisms and internal tissue conductivity imaging.

Modeling the positioning of single needle electrodes for the treatment of breast cancer in a clinical case

Background

Breast cancer is the most common cancer in women worldwide and is the second most common cause of cancer death in women. Electrochemotherapy (ECT) used in early-phase clinical trials for the treatment of primary breast cancer resulted in a not complete tumor necrosis in most cases. The present study was undertaken to analyze the feasibility to use ECT to treat patients with histologically proven unifocal ductal breast cancer. In particular, results of ECT treatment in a clinical case are compared with the ones of a simplified 3D dosimetric model.

Methods

This clinical study was conducted with the pulse generator Cliniporator Vitae (IGEA, Carpi, Italy). ECT procedures were performed according to ESOPE standard operating procedures. Five single needle electrodes were used with one positioned in the center of the tumor, and the other four distributed around the nodule. Histological images of the resected tumor are compared with the maps of the electric field obtained with a simplified 3D model in Comsol Multiphysics v 4.3.

Results

The results of the clinical case demonstrated a reduced efficacy of the ECT treatment described. The proposed simple numerical model of the breast tumor located in a low conductive tissue suggests that this is due to the reduced electric field induced inside the tumor with such 5 electrodes placement. However, where the electric field is predicted higher than the reversible electroporation threshold (E>400 V/cm), also the histological images confirm the necrosis of the target with a good agreement between the modeled and clinical results.

Conclusions

The results suggest the dependence of the effectiveness of the treatment on the careful placement of the electrodes. A detailed planned procedure for the tumor analysis after the treatment is also needed in order to better correlate the single electrode positions and the histological images. Simulation models could be used to identify better electrodes configuration in planning the experimental protocol for ECT treatment of breast tumors.

Identifying relevant group of miRNAs in cancer using fuzzy mutual information

MicroRNAs (miRNAs) act as a major biomarker of cancer. All miRNAs in human body are not equally important for cancer identification. We propose a methodology, called FMIMS, which automatically selects the most relevant miRNAs for a particular type of cancer. In FMIMS, miRNAs are initially grouped by using a SVM-based algorithm; then the group with highest relevance is determined and the miRNAs in that group are finally ranked for selection according to their redundancy. Fuzzy mutual information is used in computing the relevance of a group and the redundancy of miRNAs within it. Superiority of the most relevant group to all others, in deciding normal or cancer, is demonstrated on breast, renal, colorectal, lung, melanoma and prostate data. The merit of FMIMS as compared to several existing methods is established. While 12 out of 15 selected miRNAs by FMIMS corroborate with those of biological investigations, three of them viz., "hsa-miR-519," "hsa-miR-431" and "hsa-miR-320c" are possible novel predictions for renal cancer, lung cancer and melanoma, respectively. The selected miRNAs are found to be involved in disease-specific pathways by targeting various genes. The method is also able to detect the responsible miRNAs even at the primary stage of cancer. The related code is available at http://www.jayanta.droppages.com/FMIMS.html .