The key difference is that a PET (Positron Emission Tomography) scan detects the metabolic activity of cells, especially tumor cells, while a nuclear bone scan detects the osteoblastic response (bone-building activity) resulting from bone destruction, often caused by tumor cells.
Here's a more detailed breakdown:
Purpose and Detection Mechanism
| Feature | PET Scan | Nuclear Bone Scan |
|---|---|---|
| Main Purpose | Detect metabolic activity of cells, particularly cancer cells. | Detect areas of increased bone turnover or remodeling. |
| Detection | Measures the uptake of a radioactive tracer (usually FDG, a glucose analog) by cells. High uptake indicates high metabolic activity. | Measures the uptake of a radioactive tracer (usually technetium-99m-labeled phosphate compounds) by bone. High uptake indicates increased bone activity. |
| Underlying Principle | Cancer cells typically have higher metabolic rates than normal cells, leading to increased tracer uptake. | Bone responds to damage or tumor presence by increasing osteoblastic (bone-building) activity. This increases tracer uptake. |
What They Show
- PET Scan: Highlights areas with high metabolic activity. This is useful for detecting tumors, assessing tumor response to treatment, and identifying areas of inflammation or infection. It essentially shows how cells are using energy.
- Nuclear Bone Scan: Highlights areas of increased bone turnover. This is useful for detecting bone metastases (cancer spread to the bone), fractures, infections, and arthritis. It primarily shows where bone is being remodeled or damaged.
What They Detect
- PET Scan:
- Tumor cells (primary and metastatic)
- Areas of inflammation
- Areas of infection
- Nuclear Bone Scan:
- Bone metastases
- Fractures (especially stress fractures)
- Bone infections (osteomyelitis)
- Arthritis
- Other bone disorders causing increased bone turnover (e.g., Paget's disease)
In Essence:
The nuclear bone scan is looking for the reaction of the bone to something (like a tumor), by measuring osteoblastic activity. The PET scan is looking directly at the metabolic activity of the tumor cells themselves.
