Why are percentages utilized in the international 10/20 system for electrode placement?

The use of percentages in the international 10/20 system for electrode placement is primarily to achieve consistent placement across varying head shapes. This system is designed to provide a common framework for placing electrodes on the scalp, allowing for uniformity in how recordings are obtained, regardless of the individual differences in head size and shape.

Using percentages allows practitioners to specify electrode locations based on the total distance between key anatomical landmarks, which is an effective way to adapt the system to any patient, ensuring that electrodes are positioned proportionally. This standardization is crucial in clinical settings where accurate and repeatable measurements are necessary for assessing brain activity.

This method not only enhances the reliability of the data collected during polysomnography but also ensures that different practitioners can replicate the electrode setup effectively, fostering consistency in research and clinical practice.