[Prostate and seminal vesicle displacement following urethrography: a computed tomography-based study]

Area of Science:

• Radiology
• Radiation Oncology
• Medical Imaging

Background:

• Prostate localization is crucial for accurate radiation therapy.
• Urethrography is used for prostate apex localization.
• Potential for organ displacement after urethrography is a concern.

Purpose of the Study:

• To investigate if retrograde urethrography causes systematic displacement of the prostate and seminal vesicles.
• To quantify organ shift using CT-CT image registration.

Main Methods:

• Two CT scans were performed on 52 patients before and after urethrography.
• CT-CT image registration using external fiducials was employed.
• Displacement in x, y, and z-axes was analyzed, with blinded assessment for z-axis motion.

Main Results:

• A mean anterior displacement of 1.3 mm (y-axis) and a 1.35 mm cranial shift (z-axis) of the prostate were observed.
• Statistically significant shifts were noted (P<0.001 for y-axis, P<0.0001 for z-axis).
• Similar displacements were found for the seminal vesicles.

Conclusions:

• Retrograde urethrography leads to a small, systematic cranial and anterior displacement of the prostate and seminal vesicles.
• Findings suggest this displacement should be considered in treatment planning for prostate cancer.