What is the focal spot blur if an image is acquired with a 2mm effective focal spot, a 2-inch object-to-image distance (OID), and a 40-inch source-to-image distance (SID)?

To determine the focal spot blur, we can use the formula related to focal spot size, object-to-image distance (OID), and source-to-image distance (SID). The formula for calculating the blur is:

Blur = (Effective Focal Spot Size × OID) / SID

In this instance, we have the following measurements:

• Effective focal spot size = 2 mm

• OID = 2 inches (which is equal to 50.8 mm, since 1 inch = 25.4 mm)

• SID = 40 inches (which is equal to 1016 mm)

Now we can substitute these values into the formula:

First, convert OID and SID:

OID = 2 inches × 25.4 mm/inch = 50.8 mm

SID = 40 inches × 25.4 mm/inch = 1016 mm

Now apply these values to the formula:

Blur = (2 mm × 50.8 mm) / 1016 mm

Blur = 101.6 mm / 1016 mm

Blur ≈ 0.100 mm

It appears that there was a rounding error in calculating the exact focal spot blur. A more precise calculation gives a focal spot