To accurately quantify local seed displacement from Day 0 to Day 30 for our brachytherapy procedure. To quantify seed loss/migration and to identify the locations from where seeds are missing.
METHODS AND MATERIALS
Seed displacements were analyzed in 62 consecutive patients, who received brachytherapy with stranded I-125 seeds. At the start of the procedure, four fiducial gold markers were implanted. At the end of the implantation procedure an in-room 3D CBCT scan (Day 0) was acquired for accurate seed localization. At Day 30 a regular CT scan was acquired. This CT scan was rigidly registered to the CBCT scan using the fiducials. Subsequently, the Hungarian method was used to find pairs of corresponding seeds. Displacements were calculated and missing seeds were identified.
Local seed displacements are smaller than 5 mm for 76.3% of the seeds; 2.3% show displacements larger than 10 mm. The largest seed displacements are seen along the inferior-superior axis: on average 1.0 ± 3.2 mm in superior direction with respect to the intraprostatic fiducials. Largest displacements are seen at the inferior-lateral sides of the prostate. On average, the inferior seeds move 1.0 ± 2.8 mm in anterior and 1.8 ± 3.3 mm in superior direction. The percentage of missing seeds is 0.2% (8 out of 3893 seeds for 5 patients). Most of the missing seeds were also originally implanted at the inferior-lateral sides of the prostate.
Local seed displacements and number of missing seeds are small, and predominantly occur around the apex.
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Published online: January 25, 2022
Accepted: December 9, 2021
Received in revised form: November 4, 2021
Received: July 26, 2021
Disclosures: This research did not receive any specific grant from funding agencies in the public, commercial or not-for-profit sectors. The authors report no proprietary or commercial interest in any product mentioned or concept discussed in this article.
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