Signal Enhancement Technology of High-Voltage Power Supply in Gamma Cameras

Gamma cameras, as core devices in nuclear medicine imaging and radiation monitoring, rely heavily on the signal accuracy and noise resistance of photoelectric conversion modules. The high-voltage power supply, serving as the source of the signal chain, directly impacts the stability of the amplitude spectrum and the precision of feature extraction. 
1. Signal Chain and Role of High-Voltage Power Supply 
Gamma camera imaging is based on the interaction between gamma rays and scintillation crystals (e.g., NaI(Tl)), where visible photons generated by the crystal are converted into electrical signals via photoelectric conversion modules (e.g., photomultiplier tube arrays). The amplitude of these signals correlates with incident gamma photon energy, and the accuracy of the expected signal amplitude determines subsequent gain calibration and image quality. The high-voltage power supply plays a dual role: 
1. Providing operational voltage (typically hundreds to thousands of volts) for photomultiplier tubes, affecting electron multiplication efficiency and signal gain; 
2. Maintaining signal baseline stability to prevent feature point drift (e.g., differential minima) in the amplitude spectrum due to equivalent baseline deviation. 
2. Voltage Stability and Noise Control 
Accurate parsing of the amplitude spectrum depends on precise extraction of spectral features. For example, the first differential minimum in a significant region is located through differential calculations as the expected signal amplitude at the photoelectric effect center. Power ripple or drift may shift this feature point, compromising gain calibration. Optimization strategies include: 
Multi-stage power architecture: Combining switching power supplies with linear regulators (e.g., converting 220V AC to +5V DC, then using LDOs to generate +3.3V precision supply) to reduce high-frequency noise; 
Noise isolation: Integrating optocouplers in signal conversion modules to block ground loop interference and comparator filtering to suppress EMI. 
3. Innovations in Pulse Signal Processing 
Signal integrity is critical for energy spectrum reconstruction. Advanced circuit designs enhance quality through: 
1. Dynamic voltage stacking: Superimposing additional voltage signals (e.g., generated via diodes and controllable logic circuits) on the initial gamma voltage to amplify monochromatic drive signals without reducing overall brightness; 
2. Redundant power paths: Implementing a two-way selector to automatically switch to a backup reference voltage (VREF2) derived from gate high-voltage (VGH) buck conversion when the primary supply (e.g., AVDD) fails, ensuring gamma voltage curve stability. 
4. Gamma Voltage Generation and Enhancement 
Gamma voltage precision directly affects image contrast. Beyond traditional resistor networks, innovations involve: 
Digital PMIC regulation: Monitoring thresholds via registers and comparators, with automatic switching to a buck-circuit-generated stable voltage (VREF2 ≥ set value) if AVDD drops; 
Integrated boost units: Augmenting initial voltage amplitude before gamma correction to extend low-gray-level signals and enhance detail resolution. 
5. Future Directions 
For portable gamma cameras, miniaturization and low power consumption are key trends: 
Wide-input voltage adaptation (e.g., aviation batteries) using wide-voltage DC-DC converters; 
Intelligent gain calibration: Dynamically adjusting amplifier gains of photoelectric modules based on real-time amplitude spectrum analysis to compensate for power fluctuations.