Comparative Asessment of Intraoperative And Postimplant Dosimetry And Volumetry in Prostrate Permanent Implant Brachytherapy With 1-125 Seeds

ABSTRACT

Post implant dosimetry has become the gold standard for prostate implant evaluation. The goal of this research was to compare the dosimetry of intraoperative real-time ultrasound plan to CT postimplant plan in permanent prostate seed implant brachytherapy. A retrospective study of 20 patients treated with 125 I prostate seeds implant were performed. All plans were created using VariSeed 8.0 planning system. Intraoperative real-time ultrasound images were acquired using 0.5 cm slice thickness. Post plan CT images were acquired 3-4 weeks after implant. 125I seed activities varied between 0.352 -0.747 U per seed. The load pattern varied slightly between patients depending on the prostate size. Statistical analysis of intraoperative real-time and CT postimplant plans for prostate volumes V150 % and D90 and prostate volumes were performed and reported using SPSS (version 20.0).The intraoperative real-time prostate volume and the CT postimplant prostate volume average size were 35.128 cc and 36.384 cc respectively. Average Prostate volume parameters, V150 % was 59.225 % and 65.291, D90 was 141.839 Gy and 140.99 Gy for intraoperative real-time dosimetry and CT postimplant dosimetry respectively. There was no statistically significant difference between the intraoperative real-time and CT postimplant prostate volumes (P value= 0.137) and the D90 (P value=0.441). However there was a significant difference between V150 % values (P value = 0.005) which was most likely due to prostate edema. In conclusion, the postimplant dosimetry using CT image set showed similar D90 dose coverage to the intraoperative real-time dosimetry using ultrasound image data. This study showed that our prostate seed implant have consistently delivered adequate therapeutic dose to the prostate. Further studies to correlate other dose parameters should be performed.