Computed tomography based evaluation of prostatic fiducial marker migration between the periods of insertion and simulation

Abstract

Objective: The aim of this study was to determine whether significant fiducial marker migration occurs between the periods of prostatic marker insertion and computed tomography (CT) performed for radiotherapy planning and if a waiting period is necessary. Material and methods: Thirty-nine patients with prostate adenocarcinoma underwent fiducial marker insertion before radiotherapy between June 2013 and December 2015. Three markers were inserted by one radiologist under the guidance of transrectal ultrasonography. All patients underwent CT three hours after insertion to confirm the number and position of fiducial markers. Radiotherapy planning CT was performed on an average of 11 days (range 7-20) after insertion. CT images were imported into treatment planning system to analyze the position of fiducial markers. Point-based marker match algorithm was used to find the distance of marker migration. The mean and maximum distances between each fiducial markers were calculated. Results: The mean distance of migration was 1.029+/-0.42 mm (range 0.23-1.93 mm) and the maximum distance was 1.361+/-0.59 mm (range 0.25-2.74 mm). The distance of marker migration was not statistically significant for the groups organized according to the timing of marker insertion, prostate volume, patient age, prostate specific antigen level and Gleason score. Conclusion: According to our results significant fiducial marker migration did not occur during the interval between insertion and treatment planning CT. It should be taken into consideration that performing simulation on the same day as marker insertion might prevent increased cost and delayed radiation therapy by saving the patients from extra visits to the clinic.