Which formula is used to determine the magnification factor in radiography?

Which formula is used to determine the magnification factor in radiography?

• A. Image Size / Object Size
• B. Source-to-Image Distance / Source-to-Object Distance
• C. Source-to-Object Distance / Source-to-Image Distance
• D. Object Size / Image Size

Answer: (B)

Magnification in radiography comes from the way X-rays diverge from the focal point. The larger the distance from the source to the image receptor (SID) relative to the distance from the source to the object (SOD), the bigger the object's shadow on the image. The standard way to quantify this is the magnification factor M = SID / SOD. This ratio directly describes how much larger the image will be than the actual object, since image size equals M times the object size. For example, if SID is 100 cm and SOD is 50 cm, M = 2, so the image is twice the size of the object. If you increase SID while keeping SOD the same, magnification grows; if you increase SOD while keeping SID fixed, magnification decreases. The alternative expression of magnification as image size divided by object size is related to this idea, but the distance-ratio form is the fundamental way we describe and control magnification in radiography because it reflects the actual setup geometry you can adjust.

Magnification in radiography comes from the way X-rays diverge from the focal point. The larger the distance from the source to the image receptor (SID) relative to the distance from the source to the object (SOD), the bigger the object's shadow on the image.

The standard way to quantify this is the magnification factor M = SID / SOD. This ratio directly describes how much larger the image will be than the actual object, since image size equals M times the object size. For example, if SID is 100 cm and SOD is 50 cm, M = 2, so the image is twice the size of the object. If you increase SID while keeping SOD the same, magnification grows; if you increase SOD while keeping SID fixed, magnification decreases.

The alternative expression of magnification as image size divided by object size is related to this idea, but the distance-ratio form is the fundamental way we describe and control magnification in radiography because it reflects the actual setup geometry you can adjust.