Breast cancer represents 12.5% of all newly diagnosed cancer cases globally, establishing it as the most prevalent form of cancer worldwide. It accounts for around 30% of all newly diagnosed female cancers in the United States. The most vital and efficient tactics for reducing breast cancer-related fatalities involve early-stage tumor detection and receiving appropriate treatment. When breast cancer is identified and managed in its early stages, 98% of patients will survive five years following diagnosis.

The current methods for early breast cancer detection rely primarily on X-ray mammography and ultrasound imaging. X-ray mammography offers excellent spatial resolution but poses the risk of X-ray radiation exposure, while the compression involved can cause patient discomfort. Ultrasound imaging, though radiation-free, requires trained professionals and comes at a higher cost, potentially limiting accessibility. While effective, these standard methods have limitations related to health risks, discomfort, price, and accessibility.

In an article published in the IEEE Journal of Solid-State Circuits, researchers introduce an advanced 3-D electrical impedance tomography (EIT) imaging system for detecting breast cancer. To prove its effectiveness, the researchers successfully reconstructed 3-D images of a human phantom using a mobile device. Additionally, the system has a 3-D rotatable imaging application that can determine the location of cancer by directly rotating the breast model.

Electrical Impedance Tomography

The proposed imaging system relies on electrical impedance tomography (EIT), which operates on a novel principle of calculating the internal conductivity distribution within biological tissues by measuring impedance at the surface. According to the researchers, EIT's noninvasive and cost-effective characteristics make it an attractive option for observing biological tissues.

In direct comparison to traditional medical imaging technologies like X-ray and ultrasound, EIT offers several compelling advantages:

  • EIT boasts a compact form factor, making it easily deployable in-home use.
  • EIT offers a radiation-free imaging process, eliminating concerns related to radiation exposure.
  • EIT is designed to be user-friendly and does not necessitate the presence of specialized practitioners, further reducing barriers to utilization.

These attributes combine to make EIT a promising candidate for early breast cancer detection, particularly in scenarios where traditional methods may be less feasible or accessible.

Unfortunately, the contact impedance between the electrode and the detected object significantly influences EIT image reconstruction. To combat this issue, the researchers propose a high-resolution 3-D EIT system that represents a novel approach to mitigating the impact of contact impedance variations on EIT imaging. This system incorporates a dedicated IC that includes two key features: A high-input-impedance instrumentation amplifier (IA) with auxiliary source followers; and calibration of the loading effect of contact impedance using a trans-conductance (TC) current driver and trans-impedance (TI) monitoring circuit.

As a result, the proposed EIT imaging IC achieves the highest input impedance. This application allows for the manipulation and examination of 3-D breast model imaging results from multiple perspectives, enhancing the ability to identify the location of cancer through direct rotation of the breast model.

3-D Imaging System 

The researchers outline a 3-D breast cancer detection system concept diagram with the proposed EIT IC. One EIT IC can measure two electrodes (equivalent to one electrode pair), and multiple electrodes are measured sequentially simultaneously with three ICs. The gathered impedance data are then acquired and transmitted to mobile imaging devices, such as smartphones and tablets, where imaging applications execute the image reconstruction process.

Concept diagram of a 3-D breast cancer detection system with the proposed EIT IC.

 

A reconstruction algorithm is necessary for generating the EIT image based on surface measurements. The frequency-difference (FD) imaging technique uses impedance variations at two distinct frequencies to depict a specific target, highlighting features that show frequency-dependent variations, like breast cancer cells. Selecting the right operational frequency in FD imaging is crucial for effectively identifying the target object.

3-D image reconstruction measurement setup.

 

Measurement results of 3-D image reconstruction.

 

Significantly, the EIT imaging IC proposed in this work achieves the highest input impedance at 28.4 MΩ at 10 kHz, which is crucial for accurate boundary measurements impacting image reconstruction. This attribute dramatically bolsters the accuracy and robustness of the EIT system, making it especially effective for applications that demand the detection and localization of minor anomalies. While previous iterations of EIT systems have shown improvements in impedance resolution, the current approach advances the technology by addressing the challenge of input impedance variation and the need for real-time monitoring, shortcomings that are prevalent in other applications. The proposed EIT system mitigates issues and enhances image analysis capabilities by allowing for multi-perspective manipulation and examination of 3-D breast model imaging results, which was not possible in earlier models.

Promising Tool

The proposed EIT system has demonstrated its potential by successfully reconstructing a 3-D image of a human phantom through a mobile device, enabling the identification of cancer location by directly manipulating the breast model. This innovative approach paves the way for the 3-D EIT imaging system to deliver highly accurate and dependable results, establishing it as a promising tool for future medical imaging applications.

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