In PET quality control, what process converts reconstructed image pixel values into activity concentration?

The process that converts reconstructed image pixel values into activity concentration in PET quality control is calibration. This is because calibration involves adjusting the imaging system's response to accurately represent the amount of radioactive material present within the scanned object. It ensures that the measurements obtained from PET scans reflect true activity concentrations in the tissues being examined.

During calibration, a known source of radioactivity is used to establish a relationship between the counts detected by the PET scanner and the actual radioactivity levels in the patient's body. This process is essential because various factors, such as detector efficiency and system geometry, can influence the accuracy of the pixel value readings. By calibrating the system, these variables are taken into account, ensuring that the final images depict an accurate representation of radioactive concentrations.

The other processes listed, such as normalization, standardization, and validation, while important in various aspects of imaging and quality control, do not specifically refer to the conversion of pixel values into activity concentration. Normalization typically refers to adjusting data to eliminate systematic differences across measurements, standardization relates to ensuring consistency in procedures, and validation focuses on confirming that the system meets specific specifications and requirements.