When taking a PA projection of the chest, what is the recommended SID?

For a PA (Posteroanterior) projection of the chest, the recommended source-to-image distance (SID) is typically 72 inches. This distance helps to minimize the magnification of the heart and lungs, providing a more accurate representation of the thoracic structures. A longer SID like 72 inches also aids in reducing distortion and enhances the sharpness of the image, which is crucial for assessing lung pathology, heart size, and other thoracic conditions. This standard is widely adopted in many radiography protocols to ensure optimal image quality for diagnostic purposes.