Influence of postimplant dosimetry time to evaluation of iodine-125 implantation results
| Date |
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2014-10-03 |
ISBN 978-609-95557-1-3.
Purpose. CT based postimplant dosimetry is recognised quality assurance tool for permanent prostate brachytherapy and is recommended for all patients, treated with low dose rate branchytherapy. Searching for an answer to a question - what time is optimal to postimplant dosimetry, we have compared dosimetric parameters from examination on 1 and 30 postimplant days for group of 38 patients, treated with lodine-125 brachytherapy. All of the implantations were performed under transrectal ultrasound (TRUS) guidance using real-time dynamic dosimetric planning. Patients underwent computed tomography scanning for post-implant dosimetric evaluation of the seeds implantation on 1(Day 1) and 30(Day 30) postimplant days. 2.5 mm-thick images were obtained at 2.5 mm intervals from 2 cm above the most superior seed to 2 cm below the most inferior seed. The images were transferred to the treatment planning system for analyses by the local area network. The following parameters were compared: the radiation dose to 90% of the prostate volume (D90), the radiation dose to 30% of the urethral volume (DU30), the percentage of the prostate volume receiving 100% or 200% of the prescribed dose (V100 or V200, respectively), the percentage of the rectal volume receiving 100% of the prescribed dose (VR100). Results. Prostate volume changed from 39.6±9.6 cm³ before branchytherapy to 42.8±11.0cm³±10.8 cm³ on first postimplant day and to 37.4±9.4 cm³ on 30 postimplant day. [...].