Design Essentials for Fast-Scan Cyclic Voltammetry PCBAs

December 17, 2020 Cadence PCB Solutions

Key Takeaways

  • What is fast-scan cyclic voltammetry (FSCV)?

  • What components comprise an FSCV device? 

  • Essentials for designing FSCV PCBAs.

Researcher attaching brain scan equipment to a human subject

Neural scan preparation.

The human brain is a highly complex organ capable of phenomenal feats of integration from a variety of sensory and electrical information. It is also capable of functioning in various states of consciousness of the host body. How this, and almost all of the other activities that our brains perform, is done is largely still a mystery. That is not to say that we have not been able to peel back a few layers of the onion, so to speak. For example, we do know that neurons and synapses are key processing structures that are interconnected to form vast networks composed of multiple alternative paths. Yet, neuroscience, the branch of biological study that seeks to uncover the brain’s secrets in their totality, can still be considered to be in its infancy.  

To date, probably the most used technique for analyzing the brain is a neural scan. The most popular of these scans is the noninvasive electroencephalogram (EEG), which is used to record the alpha, beta, delta, and theta brain wave patterns. Analyzing these signals can aid in the diagnosis of sleep disorders, epilepsy, and other types of seizures by identifying changes in typically constant patterns. 

Over the past few decades, interest in associating brain activity with behavior has resulted in electrochemical monitoring techniques, such as fast-scan cyclic voltammetry. This in vivo procedure has shown great promise and is the most used method of testing dopamine activity in living organisms. As such, there are special considerations that must be taken into account when designing the electronic boards that are required. 

Let’s take a look at these PCBA essentials after first exploring fast-scan cyclic voltammetry and the types of board elements that are typically used.   

What Is Fast-Scan Cyclic Voltammetry?

Fast-scan cyclic voltammetry (FSCV) is a method for measuring the chemical activity of the brain. It is most often used to measure the neurotransmission dopamine. The importance of FSCV lies in the fact that it enables measurement while the host organism is at rest or performing activity.  FSCV may even be used to help diagnose diseases such as Parkinson’s. The difference between it and EEG is that EEGs detect electrical activity, while FSCV detects chemical activity. However, for this information to be best utilized, the results are converted to electrical signals for observation and analyses. Signals obtainable from the process are illustrated below [1].

Overview of FSCV process graphs for measured dopamine levels

FSCV process signals for dopamine level recording.

As shown in the figure above, multiple signal types can be derived from the chemical measurements obtained during FSCV, which requires the utilization of various signal processing techniques and the nonlinear components of which they are primarily composed.  

Understanding FSCV Elements and Functionality

An example of the apparatus used for an FSCV system is shown in the figure below [2].

Major elements of an FSCV system shown in a block diagram

Block diagram of FSCV system.

As the diagram above shows, an FSCV system requires a number of processors, amplifiers, and signal converters. These devices provide control over reference electrode rates, sampling intervals, motor control for the infusion pumps and signal generation, modulation and transmission (TX), reception (RX), and other processing.  

As many of these signals are quite small--dopamine current levels may be in the 10-9 range--precision is a major consideration for board components. Also important is size, as the board directly attached to the invasive work electrode should not be cumbersome or in any way impede the subject’s ability to perform normal activities. These and other factors, as discussed below, must be considered when designing boards for FSCV applications.

How to Design PCBAs for FSCV Application

Like many circuit board designs today, a premium is placed on small size with high functionality, just like for PCBAs used in FSCV systems. These systems are typically multi-board, including a board that is attached to the biological subject and another that performs most of the signal processing and data analysis duties. The system may also include a computer for an enhanced user experience (UX). Therefore, board design may include communication devices for Wi-Fi, Bluetooth, low-energy Bluetooth (BLE), or infrared (IR) TX/RX; multi-board connectors are likely to be included as well. These and other considerations, as listed below, are essential when designing boards for FSCV application. 

Fast-Scan Cyclic Voltammetry PCBA Design Essentials

  • Component Selection: FSCV requires the processing of signals over a wide range of frequencies and amplitudes. This necessitates that components be high fidelity with small tolerances. Moreover, EMI control is important to ensure proper signal detection and identification. 

  • Board and Materials: Boards must be small enough to not introduce any significant alteration in mobility for the subject. Additionally, contamination from the subject and/or environment must also be minimized (or eliminated) as this could result in malfunction or inaccurate results.

  • Layout: As FSCV boards typically require the processing of multiple signal types, it is important to follow best practices, such as component separation by signal type and separate grounding, to maximize signal integrity. 

  • Connectivity: Some FSCV tests on laboratory animals in controlled environments utilize cabling.  However, there is a significant push to utilize remote communication methods, which allow for expanded application, especially as this technology is utilized more on human subjects. The utilization of these communication methods introduces additional components into the design that must also meet the prevailing size and precision requirements. 

In order to simultaneously satisfy the various requirements for FSCV board design, a comprehensive and advanced PCB Design and Analysis software package is required. Cadence’s Allegro PCB Editor, which provides real-time layout DFM checks and is built for system-level development, is the best option for efficient, optimal designs.

If you’re looking to learn more about how Cadence has the solution for you, talk to us and our team of experts

References

1.     Hossein Zamani et al., “On the use of compressive sensing (CS) for brain dopamine recording with fast-scan cyclic voltammetry (FSCV),” IEEE International Symposium on Circuits and Systems (ISCAS)(April 2017): DOI: 10.1109/ISCAS.2017.8050302

2.     Carlos Eduardo de Araujo, et al., “In vitro evaluation of a closed-loop feedback system for dopamine concentration control,” Research on Biomedical Engineering vol.31 no.1 (Jan/Mar 2015):  https://doi.org/10.1590/2446-4740.0653.

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