Localization of the prostatic apex for radiation therapy using implanted markers

Area of Science:

• Urology
• Medical Imaging
• Radiology

Background:

• Accurate localization of the prostatic apex is crucial for various urological procedures.
• Current imaging techniques like computed tomography (CT) and retrograde urethrography have limitations in precisely defining the prostatic apex.
• Implantable markers offer a potential solution for improved anatomical reference.

Purpose of the Study:

• To evaluate the accuracy of implantable radiodense markers in localizing the prostatic apex.
• To compare marker-based localization with definitions provided by computed tomography (CT) and retrograde urethrography.
• To assess the relative accuracy of CT versus retrograde urethrography in identifying the prostatic apex.

Main Methods:

• A prospective trial involving 15 patients undergoing pelvic CT, retrograde urethrogram, and transrectal ultrasound with marker placement.
• Three radiodense markers were implanted: one at the prostatic apex and two lateral to the seminal vesicles.
• Measurements were taken to compare the superior-inferior distance between the marker-defined apex and the apex identified by CT and urethrogram.

Main Results:

• Both CT and retrograde urethrography overestimated the inferior extent of the prostatic apex compared to the marker location.
• The average difference from the marker to the CT-defined apex was 0.6 cm.
• The average difference from the marker to the urethrogram-defined apex was 1.3 cm, indicating CT was more accurate.

Conclusions:

• Ultrasound-guided implantation of radiodense markers provides precise prostatic apex localization.
• CT and retrograde urethrography tend to overestimate the inferior boundary of the prostatic apex.
• CT demonstrates higher accuracy than retrograde urethrography for prostatic apex identification.