ASRT Practice Exam 2025 – Complete Study Resource

The most important factor in controlling size distortion is the object-to-image distance (OID). Size distortion occurs when an object is projected onto the image receptor, and its size can be affected by the distance between the object being imaged and the image receptor itself. When the OID is increased, the object appears larger than its actual size because of the geometry of the imaging process. This happens since the x-ray beam diverges as it travels from the source to the image receptor, causing objects that are farther away from the receptor to appear larger.

By minimizing OID, the projection is more accurate, and size distortion is reduced, leading to a more true representation of the object's size. This is crucial for accurate diagnosis and analysis in radiology.

While other factors like focal spot size can influence detail and blurriness, and source-to-image distance impacts magnification and sharpness, OID has a direct relationship with size distortion, making it the key factor in controlling how the size of an object is represented on the image.