4. Gamma Camera
The gamma camera (Anger camera) is the fundamental imaging device in nuclear medicine SPECT.
Learning Objectives
- Identify gamma camera components and their functions
- Compare different collimator types
- Understand image formation principles
- Recognize common quality control procedures
Components
Collimator
Defines spatial resolution and sensitivity:
| Type | Resolution | Sensitivity | Use |
|---|---|---|---|
| LEHR | Highest | Lowest | Tc-99m bone, thyroid |
| LEAP | Moderate | Moderate | General purpose |
| MEGP | Moderate | Moderate | Ga-67, In-111 |
| HEGP | Lower | Higher | I-131 |
| Pinhole | Variable | Low | Thyroid, small organs |
Crystal
- NaI(Tl), typically 9.5 mm thick
- Optimal for Tc-99m (140 keV)
PMT Array
- Hexagonal arrangement
- Position calculation (Anger logic)
- Energy determination
Image Formation
Position calculation uses weighted signals from PMTs:
Quality Control
Daily QC
- Uniformity flood
- Background check
Weekly/Monthly
- Spatial resolution (bar phantom)
- Energy calibration
- COR (center of rotation)
Content under development: SPECT acquisition, reconstruction methods