Grid line artifact formation: A comprehensive theory.

Area of Science:

• Medical Physics
• Radiologic Technology
• Imaging Science

Background:

• Linear focused grids are essential for scatter reduction in radiography and mammography.
• Grid lines can become visible artifacts if the grid remains stationary during X-ray exposure.
• Moving the grid during exposure is a common technique to blur these artifacts.

Purpose of the Study:

• To develop a theoretical framework for quantifying grid line artifact magnitude.
• To evaluate various artifact suppression techniques, including novel methods.
• To assess the impact of grid parameters and X-ray output variations on artifacts.

Main Methods:

• A theoretical framework was developed using grid pitch, septum thickness, and exposure time as parameters.
• Grid velocity variations (constant, decreasing) and X-ray tube output fluctuations (kV ripple) were modeled.
• Artifacts were evaluated for stationary grids, grids moving at constant and decreasing velocities, and with kV ripple.
• A novel technique involving a 'feathered' exposure waveform with constant grid velocity was analyzed.

Main Results:

• The framework allows estimation of grid line artifact magnitude under diverse conditions.
• Grid movement with kV ripple significantly impacts artifact levels.
• A 'feathered' exposure waveform, combined with short grid travel distance, can effectively eliminate grid line artifacts.
• This suppression method allows for the design of efficient, compact, coarse-density grid systems.

Conclusions:

• The developed theoretical framework provides a robust method for analyzing grid line artifacts.
• Optimizing grid motion and X-ray exposure waveform is crucial for artifact suppression.
• The 'feathered' exposure technique offers a promising solution for eliminating grid line artifacts, enabling advancements in grid design.