Correction of Bowtie-Filter Normalization and Crescent Artifacts for a Clinical CBCT System

Area of Science:

• Medical Imaging
• Radiological Physics

Background:

• Cone beam computed tomography (CBCT) systems utilize bowtie filters to shape the X-ray beam, but these can introduce artifacts.
• Bowtie-filter crescent artifacts and bowtie-filter normalization artifacts degrade image quality in clinical CBCT.

Purpose of the Study:

• To understand and minimize bowtie-filter crescent artifacts and bowtie-filter normalization artifacts in clinical CBCT.
• To develop a practical, step-by-step procedure for artifact reduction.

Main Methods:

• Studied bowtie-filter position and profile variations during gantry rotation.
• Applied and compared two strategies (A and B) for crescent artifact correction.
• Utilized physical calibration and analytical approaches for normalization artifact minimization.
• Tested a combined procedure on phantoms and a patient, evaluating image quality via Hounsfield unit standard deviation.

Main Results:

• Bowtie-filter exhibited translational shifts and amplitude variations during rotation.
• Strategy B showed slightly better crescent artifact reduction than Strategy A.
• Physical calibration and analytical methods significantly reduced normalization artifacts.
• The combined procedure achieved the lowest Hounsfield unit standard deviation (18.8 HU), effectively minimizing both artifact types.

Conclusions:

• A combined procedure effectively minimizes both bowtie-filter crescent and normalization artifacts in clinical CBCT.
• The developed step-by-step procedure is directly applicable to clinical settings.
• This work enhances the diagnostic utility of clinical cone beam CT imaging.