The key difference between ultrasound and EEG lies in the technology they use and what they measure: ultrasound uses high-frequency sound waves to create images, while EEG measures electrical activity in the brain.
Here's a more detailed breakdown:
Ultrasound
- Technology: Employs high-frequency sound waves (typically 2-18 MHz) that are emitted from a transducer. These waves travel through the body and reflect back when they encounter different tissues and structures. The transducer receives these echoes, and a computer processes them to create an image.
- What it measures: Anatomical structures and movement in real-time. This includes organs, tissues, blood flow, and developing fetuses.
- Invasiveness: Non-invasive. It doesn't involve radiation or entering the body (except for transesophageal or transrectal ultrasounds).
- Spatial Resolution: Generally good for visualizing structures, but depends on the frequency used. Higher frequencies offer better resolution but penetrate less deeply.
- Temporal Resolution: Excellent. Images are captured in real-time, allowing doctors to see movement and changes as they happen.
- Examples:
- Prenatal imaging to monitor fetal development.
- Diagnosing gallbladder disease.
- Evaluating blood flow in arteries and veins.
- Guiding biopsies.
Electroencephalography (EEG)
- Technology: Uses electrodes placed on the scalp to detect and record electrical activity in the brain. These electrodes measure voltage fluctuations resulting from ionic current flows within the neurons of the brain.
- What it measures: Electrical activity in the brain, reflecting the activity of large populations of neurons. This activity is displayed as brain waves.
- Invasiveness: Non-invasive. Electrodes are attached to the scalp, but no instruments are inserted into the body.
- Spatial Resolution: Low. EEG signals are recorded from the scalp, so it's difficult to pinpoint the precise location of the electrical activity within the brain. It can only measure activity at low spatial resolution.
- Temporal Resolution: Excellent. EEG can capture changes in brain activity on a millisecond-by-millisecond basis.
- Examples:
- Diagnosing and monitoring seizures.
- Evaluating sleep disorders.
- Monitoring brain activity during surgery.
- Researching brain function.
Summary Table
| Feature | Ultrasound | EEG |
|---|---|---|
| Technology | Sound waves | Electrical activity |
| What it Measures | Anatomical structures and movement | Brain electrical activity (brain waves) |
| Invasiveness | Non-invasive | Non-invasive |
| Spatial Resolution | Good (depends on frequency) | Low |
| Temporal Resolution | Excellent (real-time) | Excellent (millisecond resolution) |
| Typical Uses | Imaging organs, fetal monitoring, blood flow | Seizure detection, sleep studies, brain research |
In essence, ultrasound provides anatomical images using sound waves, while EEG records brain activity using electrical signals. They serve entirely different purposes in medical diagnostics and research.
