Contrast sensitivity drives your ability to distinguish the subtle differences in materials that are close together in material density. Imaging with higher current and lower voltage is a proven method for maximizing the detectability of low subject contrast indications. As important as this technique is, an often forgotten method of improving contrast is the process of reducing scatter radiation. Scatter radiation is caused by the part, the fixture or basically anything the primary or secondary radiation strikes. This scatter radiation significantly reduces contrast sensitivity. To help reduce scatter and further increase contrast sensitivity, consider trying one or all of the following:
- Collimate the cone of radiation to strike just the area of interest of the product being imaged.
- Use fixturing that slightly raises the product up off the rotational stage table to reduce the quantity of the scatter radiation striking the table and scattering back to the detector.
- Move the product away from the detector (for mini and micro focus tubes.)
- Try using beam hardening filtration. However, keep in mind that beam filters may create more contrast reduction through attenuation than contrast improvement through scatter reduction.