Purpose/Objective(s): Fiducial seed has long been recognized as an accurate tool to correct prostate patient setup error. The alternative techniques include aligning patient using bony anatomy information and endorectal balloon. The aim of this study was to evaluate the discrepancy in prostate daily alignment based on fiducial seeds versus bony anatomy or bony anatomy plus balloon.Materials/Methods: All alignment evaluations were carried out by using Elekta X-ray volume imaging (XVI) software. Seventeen prostate patients with both fiducial seeds and water-filled endorectal balloon and four patients with fiducial seeds only were chosen for this study. Each patient was followed for more than one month. Before each treatment fraction, a cone beam computed tomography (CBCT) was acquired and the daily shift information based on fiducial seeds was recorded for each patient as the gold standard. Then the alignment was performed again based on bony anatomy only (for patients without balloon) or based on bony anatomy plus balloon (for patients with both fiducial and balloon) using the same CBCT data. For alignment based on bony anatomy only, the auto-fusion based on bone filter was applied and the angular shifts were ignored. For alignment based on bony plus balloon, the same bone filter was applied first, then the balloon was used for anterior-posterior (AP) alignment correction. The differences between shifts determined using fiducial seeds and using the bony anatomy or bony anatomy + balloon were analyzed.Results: In the right-left (RL) direction, discrepancies between shifts based on fiducial seeds and shifts based on bony only or bony + balloon were all less than 4 mm. In the superior-inferior (SI) direction, the discrepancies were less than 15 mm for bony only, and less than 8 mm for bony + balloon. In the AP direction, the discrepancies were all less than 11 mm for bony only or bony + balloon. Over 96% (AP) and 98% (SI) of the discrepancies were within 7 mm for bony + balloon, while over 75% (AP) and 48% (SI) of the discrepancies were within 7 mm for bony only.Conclusions: The RL alignments are always good regardless of the alignment technique. 7 mm seems to be a reasonable setup margin for prostate patients without fiducial seeds but with balloon. Using endorectal balloon for patients without fiducial is strongly recommended since it helps alignments in both AP and SI directions.
Zhang, R,
Chu, C,
King, M,
Gibbons, J,
Evaluation of Alignment Discrepancy Based on Fiducial Seeds versus Bony Anatomy or Bony Anatomy Plus Endorectal Balloon for Prostate Cancer Patients. Radiological Society of North America 2013 Scientific Assembly and Annual Meeting, December 1 - December 6, 2013 ,Chicago IL.
http://archive.rsna.org/2013/13044496.html
