Fiducial-based quantification of prostate tilt using cone beam computer tomography (CBCT)

Area of Science:

• Radiation oncology
• Medical imaging
• Biomechanical analysis

Background:

• Accurate prostate positioning is critical for effective radiation therapy.
• Understanding prostate movement, including tilt, is essential to minimize off-target radiation exposure.

Purpose of the Study:

• To quantify prostate tilt in response to translational shifts during image-guided radiation therapy.
• To characterize the relationship between prostate displacement and resultant tilt angles.

Main Methods:

• Utilized fiducial markers for precise prostate localization.
• Employed cone-beam computed tomography (CBCT) for in-room imaging during treatment.
• Analyzed translational shifts and corresponding prostate tilt using image registration techniques.

Main Results:

• Moderate anterior prostate displacements (<5mm) correlated with an anterior tilt.
• Large anterior displacements (>5mm) resulted in complex movements, potentially including backward tilt.
• Posterior prostate movements consistently induced a backward tilt, approximately 1 degree per millimeter of displacement.

Conclusions:

• Prostate tilt is a translation-dependent phenomenon during image-guided radiation therapy.
• The direction and magnitude of prostate displacement significantly influence the direction and degree of tilt.
• These findings highlight the importance of considering prostate tilt in treatment planning and delivery to improve accuracy.