Three-dimensional endoluminal ultrasound-guided interstitial brachytherapy in patients with anal cancer

Background: New techniques using image guidance other than computed tomography (CT) and traditional two-dimensional (2D) endosonography might improve interstitial brachytherapy in patients with anal cancer. Purpose: To investigate a new technique guided by three-dimensional (3D) endosonography used in our institution. Material and Methods: Seventeen patients with anal carcinoma were referred to interstitial brachytherapy under 3D endosonographic guidance after external radiotherapy. The procedure was initiated by anal endosonography performed with a 10-MHz rotating endoprobe. Cross-sectional images of the anal sphincters were stored on a 3D system during retraction of the endoprobe through the anal canal. Afterward, any projection could be reconstructed. From this scanning, the optimal positioning of the needles was determined. The needles were inserted through holes in an externally fixated anal template. A repeated endosonography assured that optimal tumor coverage could be obtained by adjusting the number, dwell positions, and/or position of the needles. Results: In all patients, endosonography was able to visualize the extension of the tumors and the position of each needle in 3D. Conclusion: 3D endosonography guidance of interstitial brachytherapy in anal carcinoma seems to optimize the implant procedure and offer better information for dose planning.