What does extrinsic QC refer to when performed on a camera?

Extrinsic quality control (QC) refers to testing performed on a gamma camera system when the collimator is in place. This form of QC is crucial because it assesses how well the entire system, including the collimator, detector, and electronics, performs when imaging a patient's radiopharmaceutical distribution.

When conducting extrinsic QC, a known radioactive source (often a point source or a flooded phantom) is used to evaluate parameters such as spatial resolution, uniformity, and sensitivity. The presence of the collimator is essential because it affects the camera's ability to detect and accurately image the gamma rays emitted from the source. The collimator controls the directionality of incoming photons, significantly impacting image quality and system performance.

Thus, performing extrinsic QC with the collimator allows for an accurate representation of how the gamma camera will function in clinical settings, ensuring that the images produced will be of high quality and reliability for diagnostic purposes.