How doctors peer inside the human body to spot hidden diseases using Positron Emission Tomography
Imagine a medical camera that doesn't just photograph your bones or organs, but instead takes a picture of your body's very own cellular activity. This is the power of Positron Emission Tomography, or PET.
Shows structure and anatomy - what organs and tissues look like.
Reveals function and metabolism - how cells are working.
Unlike an X-ray that shows structure, a PET scan reveals function, allowing doctors to see the body at work by tracking its metabolic processes. This technology has transformed the detection and management of diseases, particularly cancer, by identifying abnormal cell activity long before physical symptoms or structural changes appear 3 .
The ability to detect these faint signals and turn them into a precise image relies on incredible engineering.
Dense crystals that absorb gamma rays and re-emit them as flashes of visible light.
Sensors that detect faint light flashes and convert them to electrical signals.
Electronics that identify simultaneous detector hits to locate annihilation events.
| Crystal Material | Key Characteristics | Impact on Imaging |
|---|---|---|
| Bismuth Germanate (BGO) | High density, high stopping power | Reliably detects photons but has longer dead time, limiting count rates |
| Lutetium Oxyorthosilicate (LSO) | High stopping power, very fast light output, high light yield | Enables faster imaging and better image resolution; reduces dead time |
| Event Type | Description | Effect on Image |
|---|---|---|
| True Coincidence | Both photons from a single annihilation are detected without scattering. | Provides accurate signal for image formation. |
| Scatter Coincidence | One or both photons scatter before detection, but are still recorded as a coincidence. | Adds a diffuse background, reducing image contrast and quantitative accuracy. |
| Random Coincidence | Two photons from unrelated annihilations are detected within the coincidence timing window. | Adds noise and background, particularly problematic at high activity levels. |
In 2024, a research team at UC Davis, led by Professor Guobao Wang, published a breakthrough that pushes the boundaries of PET technology 2 .
Using the revolutionary EXPLORER total-body PET scanner that captures data from the entire body simultaneously.
Harnessing the high-energy gamma rays from the PET tracer's positron annihilations themselves.
Using PET data to computationally generate a second, high-energy CT image.
Combining the newly created CT image with the standard low-energy CT scan to create dual-energy CT data.
More accurately distinguish between healthy and cancerous tissues.
Improved assessment of bone marrow health and diseases.
New insights into the role of bone and bone marrow in inflammation.
The "light amplifiers" that detect faint light flashes and multiply them into measurable signals 8 .
PET instrumentation continues to evolve at a breathtaking pace, with exciting developments on the horizon.
AI is being integrated to improve image reconstruction, reduce noise, and assist in diagnosis .
Using PET to both diagnose a disease and deliver targeted therapy for personalized medicine .
As technology continues to refine our ability to see the inner workings of the human body, PET imaging stands as a powerful testament to how physics, engineering, and medicine can converge to illuminate the once unseeable, offering hope and healing for millions.